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CN114447930B - Offshore wind turbine grid-connected capacity calculation method considering power grid security constraint - Google Patents

Offshore wind turbine grid-connected capacity calculation method considering power grid security constraint Download PDF

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CN114447930B
CN114447930B CN202210175451.3A CN202210175451A CN114447930B CN 114447930 B CN114447930 B CN 114447930B CN 202210175451 A CN202210175451 A CN 202210175451A CN 114447930 B CN114447930 B CN 114447930B
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CN114447930A (en
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刘自发
赵海岩
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North China Electric Power University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/004—Generation forecast, e.g. methods or systems for forecasting future energy generation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications

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Abstract

The invention relates to a grid-connected capacity calculation method of an offshore wind farm taking account of grid safety constraint, which belongs to the field of grids, and is characterized in that the acceptance capacity of the grid to the offshore wind farm is determined according to grid section constraint conditions, grid peak regulation constraint conditions, grid frequency modulation constraint conditions and grid voltage regulation constraint conditions by comprehensively considering the grid structure, the active output limit value and the power change rate limit value of the offshore wind farm are obtained by utilizing the minimum output of a whole-grid thermal power unit in the next day, the offshore wind farm is enabled to arrange the wind power active output of the offshore wind farm to stably operate in a safe area, the difficulty brought by the randomness, intermittence and anti-peak regulation characteristics of offshore wind power generation to the grid scheduling scheme is reduced to a certain extent, the cross section out-of-limit caused by the high wind power output in the area during load valley is avoided, the large fluctuation of the grid voltage caused by the active output fluctuation of the offshore wind power is rapidly limited, the safe and stable operation of the grid is facilitated, and the acceptance capacity of the offshore wind power is improved.

Description

Offshore wind turbine grid-connected capacity calculation method considering power grid security constraint
Technical Field
The invention relates to the field of power grids, in particular to a grid-connected capacity calculation method of an offshore wind turbine generator set considering power grid safety constraint.
Background
In recent years, offshore wind power is becoming a hotspot for research and development in various countries, and is expected to become a main force of wind power industry in the future. At present, the global offshore wind power installation exceeds 35GW, china has run the world for two years continuously on the newly increased installation quantity, and the whole installation capacity of the offshore wind power in China is located in the second world by the end of 2020. According to the prediction of the global wind energy management, the total installed capacity of the global offshore wind power reaches 234GW by 2030, the total installed amount of the Chinese offshore wind power reaches 58.8GW, and the world is the country with the largest accumulated installed capacity of the world offshore wind power. The offshore wind power in China must walk into a development expressway and gradually develops towards the trend of large-scale, deep-open sea and low price.
However, after the large-capacity offshore wind turbine generator is connected to the power grid, the influence of the wind farm on the power grid has been developed from the problems of simple local voltage fluctuation and the like to the aspects of power grid regulation control (frequency modulation peak regulation, economic dispatch), electric energy quality, power grid stability and the like, and no small pressure is generated on the safe and stable operation of the large power grid.
Therefore, in order to meet the requirement of rapid development of the offshore wind power, the safe and reliable operation of the power system after the offshore wind turbine is connected to the power grid is ensured, the offshore wind turbine is connected to the power grid according to the requirement by fully considering factors in all aspects, and the adverse effect of grid connection of the offshore wind turbine on the power grid is reduced to the greatest extent. Therefore, how to accept offshore wind power to the maximum extent and ensure safe and stable operation of the power grid is a technical problem to be solved urgently at present.
Disclosure of Invention
The invention aims to provide a grid-connected capacity calculation method of an offshore wind turbine generator, which takes account of the safety constraint of a power grid, not only can ensure the safe and stable operation of the power grid, but also can furthest accommodate offshore wind power.
In order to achieve the above object, the present invention provides the following solutions:
An offshore wind turbine grid-connected capacity calculation method considering grid security constraints, the calculation method comprising:
constructing a power grid section constraint condition, a power grid peak regulation constraint condition, a power grid frequency modulation constraint condition and a power grid voltage regulation constraint condition;
Determining the minimum output of the next-day full-grid thermal power unit according to the next-day load power predicted value and the next-day offshore wind power predicted value;
Calculating the output limit value of a single offshore wind turbine in a next-day section by using the constraint condition of the power grid section according to the minimum output of the next-day full-grid thermal power turbine and the predicted value of the next-day offshore wind power;
Calculating the output limit value of a single offshore wind turbine in a next-day regional power grid according to the minimum output, the next-day load power predicted value and the next-day offshore wind power predicted value of the next-day full-grid thermal power turbine and by using the power grid peak regulation constraint condition;
determining the minimum value of the output limit value of the single offshore wind turbine in the next-day section and the output limit value of the single offshore wind turbine in the next-day regional power grid as the active output limit value of the single offshore wind turbine in the next day;
according to the predicted value of the next-day offshore wind power, determining the maximum output change rate of a single next-day offshore wind turbine by using a grid frequency modulation constraint condition;
Calculating the maximum fluctuation amplitude of the allowable active power of the single offshore wind turbine in the next day according to the output limit value of the single offshore wind turbine in the next day section and the output limit value of the single offshore wind turbine in the next day regional power grid;
Calculating the maximum active power change rate of the single offshore wind turbine according to the maximum fluctuation amplitude of the allowable active power of the single offshore wind turbine on the next day and by using the voltage regulation constraint condition of the power grid;
and determining the power change limit value of the single offshore wind turbine on the next day according to the maximum active power change rate of the single offshore wind turbine on the next day, the maximum output change rate of the single offshore wind turbine on the next day and the maximum fluctuation amplitude of the allowable active power of the single offshore wind turbine on the next day.
Optionally, the constraint condition of the section of the power grid is that
Wherein P a,i is the output limit value of the offshore wind turbine generator set i in the section, P a,max is the section stability limit, P a,cu,min is the minimum total output value of the conventional wind turbine generator set in the section, lambda j is the load factor predicted value of the offshore wind turbine generator set j which does not participate in the output control in the section, P w,j is the installed capacity of the offshore wind turbine generator set j which does not participate in the output control in the section,For the sum of all active output predicted values of the offshore wind turbines not participating in the output control in the section, E area is all the wind turbines in the section, P a,tw is the total capacity of the offshore wind turbines in the section, P w,c,k is the installed capacity of the excised wind turbine k in the section, and P w,i is the installed capacity of the offshore wind turbine i.
Optionally, the power grid peak shaving constraint condition is that
Wherein P g,i is the output limit value of a single offshore wind turbine generator in a regional power grid, P g,lf is the predicted value of total load power in the grid, P g,if is the planned value of power of an inter-grid interconnecting line, P g,cu,min is the minimum output of a whole-grid thermal power generating unit, lambda j′ is the predicted value of the load rate of an offshore wind turbine generator j 'which does not participate in the output control in the grid, P w,j′ is the installed capacity of the offshore wind turbine generator j' which does not participate in the output control in the grid,For the sum of all active output predicted values of the offshore wind turbines which do not participate in the output control in the network, E grid is all the wind turbines in the network, I ACE is the regional control error, P g,tw is the total capacity of the wind turbines in the network, and P w,c,k′ is the installed capacity of the cut wind turbine k' in the network.
Optionally, the grid frequency modulation constraint condition is that
In the method, in the process of the invention,For the maximum output change rate of the offshore wind turbine generator set i, delta P is the active power change quantity transmitted by the connecting line from the offshore wind power plant to the access point, delta t is the change time corresponding to the active power change,Is the frequency adjustment capability of the system.
Optionally, the construction process of the power grid voltage regulation constraint condition is as follows:
establishing a relation between the voltage variation and the active power variation as Wherein DeltaV is voltage variation, X is line equivalent reactance, V is terminal voltage of a connecting line, S SC is bus short-circuit capacity, and P is active power transmitted from a marine wind power plant to a connecting line of an access point;
according to the power grid section constraint condition, the power grid peak shaving constraint condition and the relation between the voltage variation and the active power variation, establishing a calculation formula of the maximum fluctuation amplitude of the allowable active power of the offshore wind turbine as Wherein DeltaP max,i is the maximum fluctuation amplitude of the allowable active power of the offshore wind turbine i, and DeltaV max is the maximum voltage variation;
According to a calculation formula of the maximum fluctuation amplitude of the allowable active power of the offshore wind turbine, establishing a calculation formula of the maximum active power change rate of a single offshore wind turbine as follows In the method, in the process of the invention,For the maximum active power change rate of the offshore wind turbine i, P l,i is the power transmitted to the grid-connected point by the offshore wind turbine i.
Optionally, the formula for determining the power change limit value of the single offshore wind turbine in the next day is as follows
In the method, in the process of the invention,The power change limit value of the offshore wind turbine i is the next day.
Optionally, determining the minimum output of the next-day full-grid thermal power unit according to the next-day load power predicted value and the next-day offshore wind power predicted value specifically includes:
Calculating the minimum output of the next-day thermal power unit by using a formula P th＝Pl,min-Po,f-Ps,f,max according to the load power predicted value of the next-day load valley period and the offshore wind power predicted maximum value of the next-day same period; wherein P th is the minimum output of the next-day thermal power unit, P l,min is the load power predicted value of the next-day load valley period, P s,f,max is the maximum predicted value of the next-day same-period offshore wind power, and P o,f is the power generation planned value of an energy unit other than the offshore wind power unit;
according to the minimum output of the next-day thermal power unit, the formula is utilized Determining the number of the starting units of the thermal power generating unit; wherein P r,th is the output of the thermal power unit r, and n is the number of the thermal power units started;
According to the load predicted value of the next day load peak time and the offshore wind power predicted minimum value of the next day same time period, determining the peak regulating capacity of the thermal power unit required by the system by using a formula delta P n＝Pl,max-Po,f-Ps,f,min-Pth; wherein DeltaP n is the peak regulation capacity of the thermal power unit required by the system, P l,max is the load predicted value of the next day load peak time period, and P s,f,min is the offshore wind power predicted minimum value of the next day same time period;
Using the formula Determining the rotation standby capacity of the thermal power unit under the starting number of the thermal power unit; wherein, delta P p is the spare capacity of the thermal power unit rotation under the starting number of the thermal power unit, and P r,N is the rated active power of the thermal power unit r;
if the rotation reserve capacity of the thermal power unit is greater than or equal to the peak regulation capacity of the thermal power unit, enabling the minimum output P g,th of the next-day full-net thermal power unit to be equal to the minimum output P th of the next-day thermal power unit;
if the rotation reserve capacity of the thermal power unit is smaller than the peak regulation capacity of the thermal power unit, the thermal power unit is started up, so that the rotation reserve capacity of the thermal power unit after the thermal power unit is started up is equal to the peak regulation capacity of the thermal power unit;
according to the thermal power generating unit after the expansion, the formula is utilized Determining the minimum output of the whole network thermal power unit in the next day; wherein n 1 is the number of the increased thermal power generating units.
Optionally, determining a power change limit value of the single next-day offshore wind turbine according to the maximum active power change rate of the single next-day offshore wind turbine, the maximum output change rate of the single next-day offshore wind turbine and the maximum fluctuation amplitude of the allowable active power of the single next-day offshore wind turbine, and then further including:
If the predicted value of the output of the single offshore wind turbine on the next day is smaller than or equal to the active output limit value of the single offshore wind turbine on the next day and the output change rate of the single offshore wind turbine on the next day is smaller than or equal to the power change limit value of the single offshore wind turbine on the next day, the offshore wind farm is kept to normally operate according to the current control strategy;
If the predicted value of the output of the single next-day offshore wind power is smaller than or equal to the active output limit value of the single next-day offshore wind power or the power change limit value of the single next-day offshore wind power, overspeed control and variable pitch control methods are adopted to adjust the predicted value of the output of the single next-day offshore wind power, the predicted value of the output of the single next-day offshore wind power is updated to the adjusted predicted value of the output of the single next-day offshore wind power, and the method returns to the step of calculating the output limit value of the single next-day offshore wind power in a next-day section according to the minimum output of the whole-day power generating unit and the predicted value of the output of the single next-day offshore wind power by using the constraint condition of the power grid section.
An offshore wind turbine grid-tie capacity computing system that accounts for grid security constraints, the computing system comprising:
The constraint condition construction module is used for constructing a power grid section constraint condition, a power grid peak regulation constraint condition, a power grid frequency modulation constraint condition and a power grid voltage regulation constraint condition;
The minimum output determining module is used for determining the minimum output of the next-day full-network thermal power unit according to the next-day load power predicted value and the next-day offshore wind power predicted value;
The section output limit value calculation module is used for calculating the output limit value of a single offshore wind turbine in the next-day section according to the minimum output of the next-day whole-grid thermal power unit and the predicted value of the next-day offshore wind power unit by utilizing the grid section constraint condition;
The in-network output limit value calculation module is used for calculating the output limit value of a single offshore wind turbine generator in a next-day regional power grid according to the minimum output, the next-day load power predicted value and the next-day offshore wind power predicted value of the next-day full-network thermal power generator set by using the power grid peak regulation constraint condition;
the active output limit value determining module is used for determining the minimum value of the output limit value of the single offshore wind turbine in the next-day section and the output limit value of the single offshore wind turbine in the next-day regional power grid as the active output limit value of the single offshore wind turbine in the next day;
The maximum output change rate determining module is used for determining the maximum output change rate of a single offshore wind turbine generator in the next day by utilizing the grid frequency modulation constraint condition according to the predicted value of the offshore wind power in the next day;
The maximum fluctuation amplitude calculation module is used for calculating the maximum fluctuation amplitude of the allowable active power of the single sea wind turbine generator in the next day according to the output limit value of the single sea wind turbine generator in the next day section and the output limit value of the single sea wind turbine generator in the next day regional power grid;
The maximum active power change rate calculation module is used for calculating the maximum active power change rate of the single offshore wind turbine generator in the next day according to the maximum fluctuation amplitude of the active power allowed by the single offshore wind turbine generator in the next day by using the voltage regulation constraint condition of the power grid;
the power change limit value determining module is used for determining the power change limit value of the single next-day offshore wind turbine according to the maximum active power change rate of the single next-day offshore wind turbine, the maximum output change rate of the single next-day offshore wind turbine and the maximum fluctuation amplitude of the allowable active power of the single next-day offshore wind turbine.
Optionally, the system further comprises:
The control strategy maintenance judging module is used for keeping the offshore wind farm to normally operate according to the current control strategy if the predicted value of the output of the single offshore wind turbine on the next day is smaller than or equal to the active output limit value of the single offshore wind turbine on the next day and the change rate of the output of the single offshore wind turbine on the next day is smaller than or equal to the power change limit value of the single offshore wind turbine on the next day;
The circulation judging module is used for adjusting the predicted value of the next-day offshore wind power by adopting an overspeed control and pitch control method if the predicted value of the next-day single offshore wind power output is smaller than or equal to the active output limit value of the next-day single offshore wind power unit or the power change limit value of the next-day single offshore wind power unit, updating the predicted value of the next-day offshore wind power into the adjusted predicted value of the next-day offshore wind power, and returning to the step of calculating the output limit value of the single offshore wind power unit in the next-day section according to the minimum output and the predicted value of the next-day offshore wind power of the next-day full-grid thermal power unit by utilizing the constraint condition of the power grid section.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
The invention discloses a grid-connected capacity calculation method of an offshore wind farm, which is used for considering grid safety constraint, and determining the capacity of a power grid to output the offshore wind farm according to grid section constraint conditions, grid peak regulation constraint conditions, grid frequency modulation constraint conditions and grid voltage regulation constraint conditions, wherein the minimum output of the next-day full-grid thermal power generation unit is used for obtaining the active output limit value and the power change rate limit value of the offshore wind farm, so that the offshore wind farm can arrange the wind power active output of the offshore wind farm to stably operate in a safe area, the phenomenon of automatic cutting-off of the wind power generation unit caused by power grid voltage and frequency fluctuation caused by the rapid change of the active output of the offshore wind power is avoided, the difficulty brought to the grid scheduling scheme formulation by randomness, intermittence and anti-peak regulation characteristics of offshore wind power generation can be reduced to a certain extent, the problem that the area is out of cross section is out caused by the wind power output during low load period is avoided, the safe and stable operation of the offshore wind power farm is facilitated, and the capacity of the offshore wind power on the offshore wind farm is rapidly limited.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for calculating the grid-connected capacity of an offshore wind turbine, which is provided by the invention and takes account of the safety constraint of a power grid;
FIG. 2 is a coordinated optimization schematic diagram of a day-ahead thermal power generation plan provided by the invention;
FIG. 3 is a schematic diagram of the grid-connected capacity calculation of the offshore wind farm provided by the invention;
FIG. 4 is a schematic diagram of the present invention for determining the regulation of the output of an offshore wind farm.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a grid-connected capacity calculation method of an offshore wind turbine generator, which takes account of the safety constraint of a power grid, not only can ensure the safe and stable operation of the power grid, but also can furthest accommodate offshore wind power.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
The invention provides a method for calculating the grid-connected capacity of an offshore wind turbine, which takes account of the safety constraint of a power grid, as shown in figure 1, and comprises the following steps:
And S1, constructing a power grid section constraint condition, a power grid peak shaving constraint condition, a power grid frequency modulation constraint condition and a power grid voltage regulation constraint condition.
1. Constraint condition of power grid section
For a section of a region needing external air supply electricity, assuming that a generator set in the section is a conventional unit and an offshore wind turbine set, and considering a calculation formula of an i output limit value P a,i of a single offshore wind farm under the constraint condition of the section is as follows:
wherein P a,i is the output limit value of the offshore wind turbine i in the section, P a,max is the stability limit of the section, P a,cu,min is the minimum total output value of the conventional wind turbine in the section, lambda j is the load factor predicted value of the offshore wind turbine j in the section which does not participate in the output control, P w,j is the installed capacity of the offshore wind turbine j in the section which does not participate in the output control, E area is all wind turbines in the section, P a,tw is the total installed capacity of the offshore wind turbine in the section, P w,c,k is the installed capacity of the wind turbine k cut out in the section, and P w,i is the installed capacity of the offshore wind turbine i.
According to the above formula, the maximum value of the active power output by the offshore wind farm is P a,i, and exceeding the maximum value causes the power transmission section to be out of limit, thereby threatening the safe operation of the power system. Therefore, the output of the offshore wind farm is strictly controlled according to the constraint condition of the section of the power grid, and out-of-limit is not allowed.
2. Grid peak shaving constraint
The load of the power system is changed at any moment, the conventional unit and the offshore wind turbine unit jointly provide the power required by the load in the regional power grid and the power planned to be transmitted to another regional power grid, the power grid has enough peak shaving capacity under the assumption that the active power output by the offshore wind power plant is large enough, and at any moment, the calculation formula of the i output limit value of the single offshore wind power plant meets the following formula:
Wherein P g,i is the output limit value of a single offshore wind turbine I in a regional power grid, P g,lf is the predicted value of total load power in the grid, P g,if is the planned value of inter-grid tie power, P g,cu,min is the minimum output of a whole-grid thermal power generating unit, lambda j′ is the predicted value of the load rate of the offshore wind turbine j ' which does not participate in the output control in the grid, P w,j′ is the installed capacity of the offshore wind turbine j ' which does not participate in the output control in the grid, E grid is all wind turbines in the grid, I ACE is the regional control error, P g,tw is the total capacity of the wind turbines in the grid, and P w,c,k′ is the installed capacity of the cut wind turbine k ' in the grid.
3. Grid frequency modulation constraint condition
Under normal operation, the offshore wind farm can be regarded as a power supply with rapidly changing active output for the power system due to unstable offshore wind speed. The system must have positive and negative active reserve capacities with fast response speed, and the system frequency can be kept stable when the active output of the offshore wind power plant changes rapidly.
Therefore, in the case of determining the other unit start-up modes of the system, the frequency adjustment capability (Δp/Δt) max,f of the system is also determined at the same time. In order to ensure that the system frequency is not out of limit due to insufficient regulation rate when the active output of the offshore wind farm is changed rapidly, the output change rate of the offshore wind farm must be controlled, namely:
in the method, in the process of the invention, For the maximum output change rate of the offshore wind turbine generator set i, delta P is the active power change quantity transmitted by the connecting line from the offshore wind power plant to the access point, delta t is the change time corresponding to the active power change,Is the frequency adjustment capability of the system.
Therefore, in order to ensure that the system frequency is in a safe operation range, the change rate of the active power of the offshore wind farm should meet the constraint condition of system frequency modulation, and the system frequency modulation cannot be out of limit.
4. Power grid voltage regulation constraint condition
According to the voltage requirement, the offshore wind farm should be capable of controlling the grid-connected point voltage to be in the range of 97% -107% of the nominal voltage. According to a voltage change empirical formula, when the power of a connecting line from an offshore wind power plant to an access point is unchanged in transmission of reactive power Q, and the transmitted active power fluctuates from P to delta P+P, the relationship between the voltage change level and the active power change amount can be deduced as follows:
wherein DeltaV is voltage variation, X is line equivalent reactance, V is terminal voltage of a connecting line, S SC is bus short-circuit capacity, and P is active power transmitted by the connecting line from the offshore wind farm to the access point.
Thus, for a particular offshore wind farm, active power changes may cause voltage violations. According to the voltage condition of the current operating point and the allowable voltage fluctuation amplitude, the allowable active power fluctuation amplitude calculation formula of the offshore wind farm can be deduced according to the above formula, and the calculation formula is shown as follows:
Wherein DeltaP max,i is the maximum fluctuation amplitude of the allowable active power of the offshore wind turbine i, and DeltaV max is the maximum voltage variation.
And after comprehensively considering the power grid section constraint condition and the power grid peak regulation constraint condition, selecting the minimum value of P a,i and P g,i as the output limit value of the final grid-connected operation of the offshore wind farm, and substituting the minimum value as the maximum power flow of the connecting line into the upper formula to calculate the active power fluctuation amplitude limit value of the offshore wind farm.
In the case of a constant transmission reactive power, the transmission of active power is affected and limited by the line parameters and the voltage level. Therefore, to increase the active power delivery capacity of the tie-line, reactive compensation equipment must be added, and the response rate of reactive compensation determines the rate of active increase. The rate of change of active power determined by the voltage control measure is shown as follows:
in the method, in the process of the invention, For the maximum active power change rate of the offshore wind turbine i, P l,i is the power transmitted to the grid-connected point by the offshore wind turbine i, and the active power output by the offshore wind farm in the numerical value of P l,i is equal to the active power output by the offshore wind farm in the grid-connected state.
From the above equation, to meet the voltage stable operation of the wind power access point, for each offshore wind farm, at a certain time of the reactive power compensation device of the wind power access point, the response speed of the reactive power compensation device determines the allowable voltage change rate, that is, the allowable active power increase rate, and the larger the transmission power, the larger the power increase amplitude, the smaller the allowable power increase rate.
And S2, determining the minimum output of the next-day full-network thermal power unit according to the next-day load power predicted value and the next-day offshore wind power predicted value.
This step belongs to the coordinated optimization of the thermal power generation plan in the day ahead, and a specific flow chart is shown in fig. 2.
According to factors such as offshore wind power prediction, load prediction, tie line planning, safety constraint and the like, errors of all prediction systems are considered, and a starting mode and a power generation plan of the thermal power generating unit and a power generation plan of an offshore wind farm are coordinated, optimized and arranged. And when a day-ahead power generation plan is formulated, the power and electricity quantity data obtained by the offshore wind power prediction are incorporated into power generation and electricity balance calculation, and a reserved space is reserved for offshore wind power output in the power generation plan formulation process, so that conditions are created for accepting the offshore wind power output as much as possible.
For example, firstly, according to the predicted maximum value of the offshore wind power in the next load valley period, the minimum output of the thermal power unit is arranged, and the predicted value of the load power in the next load valley period is assumed to be P l,min, the predicted maximum value of the offshore wind power in the same period is assumed to be P s,f,max, the power generation plan value of the energy units except the offshore wind power unit is assumed to be P o,f, and then the minimum output of the thermal power unit in the next day is assumed to be P th＝Pl,min-Po,f-Ps,f,max; then the minimum starting mode is obtained by back-pushing according to the low valley peak shaving capacity of the thermal power unit, namely the starting number n of the thermal power unit and the output P r,th of the thermal power unit r are determined according to P th, namelyRated active power of the r-th thermal power generating unit is P r,N; finally, the peak capacity of the thermal power unit under the minimum starting mode is checked again, the supporting capacity of other quick peak regulating units is considered, the peak regulating capacity of the thermal power unit required by the system can be confirmed to be delta P n＝Pl,max-Po,f-Ps,f,min-Pth according to the load predicted value P l,max of the next day load peak time period and the offshore wind power predicted minimum value P s,f,min of the next day same time period, the peak regulating capacity of the thermal power unit is the peak capacity, and the rotation standby capacity of the thermal power unit under the minimum starting modeΔp p should be greater than Δp n, i.e. when Δp p>ΔPn, the peak regulation requirement of the system is met, and if Δp p<ΔPn, the peak regulation capability is insufficient, i.e. the power supply is insufficient at peak time, the thermal power unit must be started up, so that "wind curtailment" at low valley may be caused. If DeltaP p>ΔPn, P g,th＝Pth and if DeltaP p<ΔPn, mainly meet the system peak regulation requirement, increase n 1 thermal power generating units to increase the rotation reserve capacity to DeltaP n,I.e.The minimum output P g,th of the whole network thermal power unit in the next day is obtained through the steps.
And S3, calculating the output limit value of the single offshore wind turbine in the next-day section by using the constraint condition of the power grid section according to the minimum output of the next-day full-grid thermal power unit and the predicted value of the next-day offshore wind power.
And enabling the total output minimum value P a,cu,min of the conventional unit in the section to be equal to the minimum output P g,th of the whole-network thermal power unit in the next day. And determining the sum of all active output predicted values of the offshore wind turbines which do not participate in output control in the section according to the next-day offshore wind power predicted valueAnd further calculating to obtain the output limit value P a,i of the single offshore wind turbine in the next-day section by using the constraint condition of the power grid section.
And S4, calculating the output limit value of the single offshore wind turbine in the next-day regional power grid by using the power grid peak regulation constraint condition according to the minimum output of the next-day full-grid thermal power unit, the next-day load power predicted value and the next-day offshore wind power predicted value.
The total load power predicted value P g,lf in the network is enabled to be equal to the next day load power predicted value, the minimum output P g,cu,min of the whole network thermal power unit is enabled to be equal to the minimum output P g,th of the whole network thermal power unit in the next day, and the sum of the active output predicted values of all the offshore wind power units which do not participate in output control in the network is determined according to the next day offshore wind power predicted valueAnd further calculating to obtain the output limit value P g,i of the single offshore wind turbine in the next-day regional power grid by using the power grid peak shaving constraint condition.
And S5, determining the minimum value of the output limit value of the single offshore wind turbine in the next-day section and the output limit value of the single offshore wind turbine in the next-day regional power grid as the active output limit value of the single offshore wind turbine in the next day.
That is, the active power output limit P i,max for an individual offshore wind farm may be determined according to:
Pi,max＝min{Pa,i,Pg,i}
and S6, determining the maximum output change rate of the single offshore wind turbine in the next day by using the grid frequency modulation constraint condition according to the predicted value of the offshore wind power in the next day.
The active power change quantity delta P of the tie line transmission from the offshore wind farm to the access point is determined according to the predicted value of the next-day offshore wind power, and the maximum output change rate of the next-day single offshore wind turbine can be calculated by further utilizing the grid frequency modulation constraint condition
And S7, calculating the maximum fluctuation amplitude of the allowable active power of the single sea wind turbine in the next day according to the output limit value of the single sea wind turbine in the next day section and the output limit value of the single sea wind turbine in the next day regional power grid.
According to the output limit value P a,i of a single offshore wind turbine in the next-day section and the output limit value P g,i of a single offshore wind turbine in the next-day regional power grid, a calculation formula of maximum fluctuation amplitude of allowable active power of the offshore wind turbine is utilizedAnd a relation between the voltage variation and the active power variationThe maximum fluctuation amplitude delta P max,i of the allowable active power of the single offshore wind turbine generator on the next day can be calculated.
And S8, calculating the maximum active power change rate of the single offshore wind turbine on the next day by using the power grid voltage regulation constraint condition according to the maximum fluctuation amplitude of the allowable active power of the single offshore wind turbine on the next day.
The maximum fluctuation amplitude delta P max,i of active power allowed by single offshore wind turbine generator on the next day is brought into power grid voltage regulation constraint conditionCalculating to obtain the maximum active power change rate of the single offshore wind turbine in the next day
And S9, determining the power change limit value of the single offshore wind turbine on the next day according to the maximum active power change rate of the single offshore wind turbine on the next day, the maximum output change rate of the single offshore wind turbine on the next day and the maximum fluctuation amplitude of the allowable active power of the single offshore wind turbine on the next day.
Exemplary, the power change limit value of the single offshore wind turbine in the next day is determined by the following formula
In the method, in the process of the invention,The power change limit value of the offshore wind turbine i is the next day.
The invention calculates and obtains the minimum output P g,th of the next day full-grid thermal power generating unit according to the flow of the figure 2, comprehensively considers the power grid section constraint condition, the power grid peak regulation constraint condition, the power grid frequency regulation constraint condition and the power grid voltage regulation constraint condition according to the power grid structure, determines the admittance capacity of the power grid to the output of the offshore wind power plant, and obtains the active output limit P i,max and the power change rate limit of the offshore wind power plantThe limit value of the grid-connected capacity of the single offshore wind farm and the limit value of the power change rate after grid connection, which are considered for the safety constraint of the power grid, are determined. As shown in fig. 3. The calculation flow of the grid-connected capacity of the offshore wind farm in the week, the day before and the day is the same, and the difference is the frequency of rolling calculation, wherein the rolling calculation is carried out once every 15min in the safety area in the day, and the real-time adjustment is carried out.
Further, the invention is based on the active output limit value P i,max and the power change rate limit value of the offshore wind farmAnd (3) verifying predicted output data of the offshore wind farm, if the output and the output change rate of the offshore wind farm do not exceed the limit values, enabling the offshore wind farm to normally operate according to an original control strategy, if the output data of the offshore wind farm in a certain period does not meet the constraint condition of a power grid and exceeds the limit value data of the power grid, adopting a method for reducing or increasing the rotating speed of a fan, discarding tracking wind speed to capture the maximum power so as to reduce the output of the offshore wind farm, adopting a variable pitch control method, giving a smooth output power value of a wind turbine, taking the deviation of the real-time rotating speed of the wind turbine and the smooth rotating speed as an input value of a variable pitch control system to participate in adjustment, enabling the rotating speed of the wind turbine to track the smooth rotating speed so as to smooth the output power of the fan, enabling the output value and the output change rate of the offshore wind farm to be reduced below the limit values so as to meet the constraint condition of the power grid, and guaranteeing safe and stable operation of the power grid, wherein the specific flow is shown in figure 4.
By adopting the grid-connected capacity calculation method of the offshore wind farm, which takes the safety constraint of the power grid into account, the active power output of the offshore wind farm can be arranged to stably run in a safe area, the phenomenon of automatic cutting off of the wind turbine caused by the voltage and frequency fluctuation of the power grid due to the rapid change of the active power output of the offshore wind farm is avoided, the difficulty in formulating a power grid dispatching scheme due to the randomness, intermittence and anti-peak regulation characteristic of the offshore wind power generation can be reduced to a certain extent, the out-of-limit of the area delivery section caused by the high wind power output during the load valley is avoided, the large fluctuation of the power grid voltage caused by the active power output fluctuation of the offshore wind farm is rapidly limited, the safe and stable running of the power grid is facilitated, the acceptance of the power grid to the offshore wind power is improved, and the utilization rate of the offshore wind power is improved.
The invention also provides a system for calculating the grid-connected capacity of the offshore wind turbine, which takes the security constraint of the power grid into account, wherein the system comprises:
The constraint condition construction module is used for constructing a power grid section constraint condition, a power grid peak regulation constraint condition, a power grid frequency modulation constraint condition and a power grid voltage regulation constraint condition;
The minimum output determining module is used for determining the minimum output of the next-day full-network thermal power unit according to the next-day load power predicted value and the next-day offshore wind power predicted value;
The section output limit value calculation module is used for calculating the output limit value of a single offshore wind turbine in the next-day section according to the minimum output of the next-day whole-grid thermal power unit and the predicted value of the next-day offshore wind power unit by utilizing the grid section constraint condition;
The in-network output limit value calculation module is used for calculating the output limit value of a single offshore wind turbine generator in a next-day regional power grid according to the minimum output, the next-day load power predicted value and the next-day offshore wind power predicted value of the next-day full-network thermal power generator set by using the power grid peak regulation constraint condition;
the active output limit value determining module is used for determining the minimum value of the output limit value of the single offshore wind turbine in the next-day section and the output limit value of the single offshore wind turbine in the next-day regional power grid as the active output limit value of the single offshore wind turbine in the next day;
The maximum output change rate determining module is used for determining the maximum output change rate of a single offshore wind turbine generator in the next day by utilizing the grid frequency modulation constraint condition according to the predicted value of the offshore wind power in the next day;
The maximum fluctuation amplitude calculation module is used for calculating the maximum fluctuation amplitude of the allowable active power of the single sea wind turbine generator in the next day according to the output limit value of the single sea wind turbine generator in the next day section and the output limit value of the single sea wind turbine generator in the next day regional power grid;
The maximum active power change rate calculation module is used for calculating the maximum active power change rate of the single offshore wind turbine generator in the next day according to the maximum fluctuation amplitude of the active power allowed by the single offshore wind turbine generator in the next day by using the voltage regulation constraint condition of the power grid;
the power change limit value determining module is used for determining the power change limit value of the single next-day offshore wind turbine according to the maximum active power change rate of the single next-day offshore wind turbine, the maximum output change rate of the single next-day offshore wind turbine and the maximum fluctuation amplitude of the allowable active power of the single next-day offshore wind turbine.
The system further comprises:
The control strategy maintenance judging module is used for keeping the offshore wind farm to normally operate according to the current control strategy if the predicted value of the output of the single offshore wind turbine on the next day is smaller than or equal to the active output limit value of the single offshore wind turbine on the next day and the change rate of the output of the single offshore wind turbine on the next day is smaller than or equal to the power change limit value of the single offshore wind turbine on the next day;
The circulation judging module is used for adjusting the predicted value of the next-day offshore wind power by adopting an overspeed control and pitch control method if the predicted value of the next-day single offshore wind power output is smaller than or equal to the active output limit value of the next-day single offshore wind power unit or the power change limit value of the next-day single offshore wind power unit, updating the predicted value of the next-day offshore wind power into the adjusted predicted value of the next-day offshore wind power, and returning to the step of calculating the output limit value of the single offshore wind power unit in the next-day section according to the minimum output and the predicted value of the next-day offshore wind power of the next-day full-grid thermal power unit by utilizing the constraint condition of the power grid section.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.

Claims (10)

1. The method for calculating the grid-connected capacity of the offshore wind turbine with consideration of the safety constraint of the power grid is characterized by comprising the following steps of:
constructing a power grid section constraint condition, a power grid peak regulation constraint condition, a power grid frequency modulation constraint condition and a power grid voltage regulation constraint condition;
Determining the minimum output of the next-day full-grid thermal power unit according to the next-day load power predicted value and the next-day offshore wind power predicted value;
Calculating the output limit value of a single offshore wind turbine in a next-day section by using the constraint condition of the power grid section according to the minimum output of the next-day full-grid thermal power turbine and the predicted value of the next-day offshore wind power;
Calculating the output limit value of a single offshore wind turbine in a next-day regional power grid according to the minimum output, the next-day load power predicted value and the next-day offshore wind power predicted value of the next-day full-grid thermal power turbine and by using the power grid peak regulation constraint condition;
determining the minimum value of the output limit value of the single offshore wind turbine in the next-day section and the output limit value of the single offshore wind turbine in the next-day regional power grid as the active output limit value of the single offshore wind turbine in the next day;
according to the predicted value of the next-day offshore wind power, determining the maximum output change rate of a single next-day offshore wind turbine by using a grid frequency modulation constraint condition;
Calculating the maximum fluctuation amplitude of the allowable active power of the single offshore wind turbine in the next day according to the output limit value of the single offshore wind turbine in the next day section and the output limit value of the single offshore wind turbine in the next day regional power grid;
Calculating the maximum active power change rate of the single offshore wind turbine according to the maximum fluctuation amplitude of the allowable active power of the single offshore wind turbine on the next day and by using the voltage regulation constraint condition of the power grid;
and determining the power change limit value of the single offshore wind turbine on the next day according to the maximum active power change rate of the single offshore wind turbine on the next day, the maximum output change rate of the single offshore wind turbine on the next day and the maximum fluctuation amplitude of the allowable active power of the single offshore wind turbine on the next day.
2. The method for calculating the grid-connected capacity of the offshore wind turbine, taking into account grid safety constraints, according to claim 1, wherein the grid section constraints are as follows
Wherein P a,i is the output limit value of the offshore wind turbine generator set i in the section, P a,max is the section stability limit, P a,cu,min is the minimum total output value of the conventional wind turbine generator set in the section, lambda j is the load factor predicted value of the offshore wind turbine generator set j which does not participate in the output control in the section, P w,j is the installed capacity of the offshore wind turbine generator set j which does not participate in the output control in the section,For the sum of all active output predicted values of the offshore wind turbines not participating in the output control in the section, E area is all the wind turbines in the section, P a,tw is the total capacity of the offshore wind turbines in the section, P w,c,k is the installed capacity of the excised wind turbine k in the section, and P w,i is the installed capacity of the offshore wind turbine i.
3. The method for calculating the grid-connected capacity of the offshore wind turbine, taking account of grid security constraints, according to claim 2, wherein the grid peak shaving constraints are as follows
Wherein P g,i is the output limit value of a single offshore wind turbine generator in a regional power grid, P g,lf is the predicted value of total load power in the grid, P g,if is the planned value of power of an inter-grid interconnecting line, P g,cu,min is the minimum output of a whole-grid thermal power generating unit, lambda j′ is the predicted value of the load rate of an offshore wind turbine generator j 'which does not participate in the output control in the grid, P w,j′ is the installed capacity of the offshore wind turbine generator j' which does not participate in the output control in the grid,For the sum of all active output predicted values of the offshore wind turbines which do not participate in the output control in the network, E grid is all the wind turbines in the network, I ACE is the regional control error, P g,tw is the total capacity of the wind turbines in the network, and P w,c,k′ is the installed capacity of the cut wind turbine k' in the network.
4. The method for calculating the grid-connected capacity of the offshore wind turbine generator set according to claim 3, wherein the grid frequency modulation constraint condition is that
In the method, in the process of the invention,For the maximum output change rate of the offshore wind turbine generator set i, delta P is the active power change quantity transmitted by the connecting line from the offshore wind power plant to the access point, delta t is the change time corresponding to the active power change,Is the frequency adjustment capability of the system.
5. The method for calculating the grid-connected capacity of the offshore wind turbine generator set according to claim 4, wherein the construction process of the grid voltage regulation constraint condition is as follows:
establishing a relation between the voltage variation and the active power variation as Wherein DeltaV is voltage variation, X is line equivalent reactance, V is terminal voltage of a connecting line, S SC is bus short-circuit capacity, and P is active power transmitted from a marine wind power plant to a connecting line of an access point;
according to the power grid section constraint condition, the power grid peak shaving constraint condition and the relation between the voltage variation and the active power variation, establishing a calculation formula of the maximum fluctuation amplitude of the allowable active power of the offshore wind turbine as Wherein DeltaP max,i is the maximum fluctuation amplitude of the allowable active power of the offshore wind turbine i, and DeltaV max is the maximum voltage variation;
According to a calculation formula of the maximum fluctuation amplitude of the allowable active power of the offshore wind turbine, establishing a calculation formula of the maximum active power change rate of a single offshore wind turbine as follows In the method, in the process of the invention,For the maximum active power change rate of the offshore wind turbine i, P l,i is the power transmitted to the grid-connected point by the offshore wind turbine i.
6. The method for calculating the grid-connected capacity of the offshore wind turbine generator set according to claim 5, wherein the determination formula of the power change limit value of the single offshore wind turbine generator set in the next day is as follows
In the method, in the process of the invention,The power change limit value of the offshore wind turbine i is the next day.
7. The method for calculating the grid-connected capacity of the offshore wind turbine generator set according to claim 1, wherein the determining the minimum output of the next-day whole-grid thermal power generation unit according to the next-day load power predicted value and the next-day offshore wind power predicted value specifically comprises:
Calculating the minimum output of the next-day thermal power unit by using a formula P th＝Pl,min-Po,f-Ps,f,max according to the load power predicted value of the next-day load valley period and the offshore wind power predicted maximum value of the next-day same period; wherein P th is the minimum output of the next-day thermal power unit, P l,min is the load power predicted value of the next-day load valley period, P s,f,max is the maximum predicted value of the next-day same-period offshore wind power, and P o,f is the power generation planned value of an energy unit other than the offshore wind power unit;
according to the minimum output of the next-day thermal power unit, the formula is utilized Determining the number of the starting units of the thermal power generating unit; wherein P r,th is the output of the thermal power unit r, and n is the number of the thermal power units started;
According to the load predicted value of the next day load peak time and the offshore wind power predicted minimum value of the next day same time period, determining the peak regulating capacity of the thermal power unit required by the system by using a formula delta P n＝Pl,max-Po,f-Ps,f,min-Pth; wherein DeltaP n is the peak regulation capacity of the thermal power unit required by the system, P l,max is the load predicted value of the next day load peak time period, and P s,f,min is the offshore wind power predicted minimum value of the next day same time period;
Using the formula Determining the rotation standby capacity of the thermal power unit under the starting number of the thermal power unit; wherein, delta P p is the spare capacity of the thermal power unit rotation under the starting number of the thermal power unit, and P r,N is the rated active power of the thermal power unit r;
if the rotation reserve capacity of the thermal power unit is greater than or equal to the peak regulation capacity of the thermal power unit, enabling the minimum output P g,th of the next-day full-net thermal power unit to be equal to the minimum output P th of the next-day thermal power unit;
if the rotation reserve capacity of the thermal power unit is smaller than the peak regulation capacity of the thermal power unit, the thermal power unit is started up, so that the rotation reserve capacity of the thermal power unit after the thermal power unit is started up is equal to the peak regulation capacity of the thermal power unit;
according to the thermal power generating unit after the expansion, the formula is utilized Determining the minimum output of the whole network thermal power unit in the next day; wherein n 1 is the number of the increased thermal power generating units.
8. The method for calculating the grid-connected capacity of the offshore wind turbine generator according to claim 1, wherein the determining the power variation limit value of the single offshore wind turbine generator in the next day according to the maximum active power variation rate of the single offshore wind turbine generator in the next day, the maximum output variation rate of the single offshore wind turbine generator in the next day and the maximum fluctuation amplitude of the allowed active power of the single offshore wind turbine generator in the next day further comprises:
If the predicted value of the output of the single offshore wind turbine on the next day is smaller than or equal to the active output limit value of the single offshore wind turbine on the next day and the output change rate of the single offshore wind turbine on the next day is smaller than or equal to the power change limit value of the single offshore wind turbine on the next day, the offshore wind farm is kept to normally operate according to the current control strategy;
If the predicted value of the output of the single next-day offshore wind power is smaller than or equal to the active output limit value of the single next-day offshore wind power or the power change limit value of the single next-day offshore wind power, overspeed control and variable pitch control methods are adopted to adjust the predicted value of the output of the single next-day offshore wind power, the predicted value of the output of the single next-day offshore wind power is updated to the adjusted predicted value of the output of the single next-day offshore wind power, and the method returns to the step of calculating the output limit value of the single next-day offshore wind power in a next-day section according to the minimum output of the whole-day power generating unit and the predicted value of the output of the single next-day offshore wind power by using the constraint condition of the power grid section.
9. An offshore wind turbine grid-connected capacity computing system taking into account grid security constraints, the computing system comprising:
The constraint condition construction module is used for constructing a power grid section constraint condition, a power grid peak regulation constraint condition, a power grid frequency modulation constraint condition and a power grid voltage regulation constraint condition;
The minimum output determining module is used for determining the minimum output of the next-day full-network thermal power unit according to the next-day load power predicted value and the next-day offshore wind power predicted value;
The section output limit value calculation module is used for calculating the output limit value of a single offshore wind turbine in the next-day section according to the minimum output of the next-day whole-grid thermal power unit and the predicted value of the next-day offshore wind power unit by utilizing the grid section constraint condition;
The in-network output limit value calculation module is used for calculating the output limit value of a single offshore wind turbine generator in a next-day regional power grid according to the minimum output, the next-day load power predicted value and the next-day offshore wind power predicted value of the next-day full-network thermal power generator set by using the power grid peak regulation constraint condition;
the active output limit value determining module is used for determining the minimum value of the output limit value of the single offshore wind turbine in the next-day section and the output limit value of the single offshore wind turbine in the next-day regional power grid as the active output limit value of the single offshore wind turbine in the next day;
The maximum output change rate determining module is used for determining the maximum output change rate of a single offshore wind turbine generator in the next day by utilizing the grid frequency modulation constraint condition according to the predicted value of the offshore wind power in the next day;
The maximum fluctuation amplitude calculation module is used for calculating the maximum fluctuation amplitude of the allowable active power of the single sea wind turbine generator in the next day according to the output limit value of the single sea wind turbine generator in the next day section and the output limit value of the single sea wind turbine generator in the next day regional power grid;
The maximum active power change rate calculation module is used for calculating the maximum active power change rate of the single offshore wind turbine generator in the next day according to the maximum fluctuation amplitude of the active power allowed by the single offshore wind turbine generator in the next day by using the voltage regulation constraint condition of the power grid;
the power change limit value determining module is used for determining the power change limit value of the single next-day offshore wind turbine according to the maximum active power change rate of the single next-day offshore wind turbine, the maximum output change rate of the single next-day offshore wind turbine and the maximum fluctuation amplitude of the allowable active power of the single next-day offshore wind turbine.
10. The offshore wind turbine grid-tie capacity computing system of claim 9, wherein the system further comprises:
The control strategy maintenance judging module is used for keeping the offshore wind farm to normally operate according to the current control strategy if the predicted value of the output of the single offshore wind turbine on the next day is smaller than or equal to the active output limit value of the single offshore wind turbine on the next day and the change rate of the output of the single offshore wind turbine on the next day is smaller than or equal to the power change limit value of the single offshore wind turbine on the next day;
The circulation judging module is used for adjusting the predicted value of the next-day offshore wind power by adopting an overspeed control and pitch control method if the predicted value of the next-day single offshore wind power output is smaller than or equal to the active output limit value of the next-day single offshore wind power unit or the power change limit value of the next-day single offshore wind power unit, updating the predicted value of the next-day offshore wind power into the adjusted predicted value of the next-day offshore wind power, and returning to the step of calculating the output limit value of the single offshore wind power unit in the next-day section according to the minimum output and the predicted value of the next-day offshore wind power of the next-day full-grid thermal power unit by utilizing the constraint condition of the power grid section.
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