CN114498715B - New energy storage system with centralized access to flexible traction transformer and control method - Google Patents
New energy storage system with centralized access to flexible traction transformer and control method Download PDFInfo
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- CN114498715B CN114498715B CN202111573975.XA CN202111573975A CN114498715B CN 114498715 B CN114498715 B CN 114498715B CN 202111573975 A CN202111573975 A CN 202111573975A CN 114498715 B CN114498715 B CN 114498715B
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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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
- H02J1/102—Parallel operation of dc sources being switching converters
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
- H02J1/106—Parallel operation of dc sources for load balancing, symmetrisation, or sharing
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/14—Balancing the load in a network
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33584—Bidirectional converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
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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
- 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
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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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
- 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
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- Engineering & Computer Science (AREA)
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- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
The invention discloses a new energy storage system with a centralized access flexible traction transformer and a control method, wherein the new energy storage system comprises: the system comprises a flexible traction transformer, an isolated DC/DC converter, a direct current bus, a new energy power generation system and an energy storage system; the flexible traction transformer is connected with the isolated DC/DC converter; the isolated DC/DC converter is respectively connected with the new energy power generation system and the energy storage system through a direct current bus; the new energy power generation system is connected with the direct current bus and used for accessing power to a direct current link of the flexible traction transformer through the isolated DC/DC converter; the energy storage system is used for effectively stabilizing the intermittence and fluctuation of the new energy power generation; the invention can reasonably and flexibly design the number of the access cascade modules according to the capacity of the accessed new energy, effectively consume the new energy while ensuring the optimal cost and the maximum benefit, and improve the utilization rate of the new energy and the regenerative braking energy under the condition of relatively simple coordination control; and the transformation of the traction net is not involved, and the engineering realization is easy.
Description
Technical Field
The invention relates to the field of new energy storage systems, in particular to a new energy storage system with a flexible traction transformer connected in a centralized mode and a control method.
Background
A large number of research achievements and application cases of new energy power generation in the field of power systems exist, and the new energy power generation is applied to the traction and development technology of the electrified railway, and belongs to a new research direction.
At present, domestic and foreign researches on new energy access to electrified railways mainly focus on station power utilization, signal, communication and other low-voltage system power supply, and few researches on access to traction power supply systems are carried out. New energy power generation is connected into a traction power supply system, and a complex connection structure and a control method are involved. The prior art provides a control system related to in-phase traction power supply and remote power generation grid connection, but the method does not consider the coexistence of multiple new energy sources and does not relate to how to access the multiple new energy sources into a traction power supply system; the method is characterized in that a new energy convergence power cable is arranged in a corridor along a railway and then connected to a traction bus of the traction substation, but the mode has the problems of large consumption of the convergence cable, complex tide distribution caused by increase of access points and the like, new energy fluctuation and intermittence can directly influence the stability of a traction network through the traction bus, and the resonance of the traction network is aggravated; in addition, the distributed power generation and supply system of the AT traction network still has the defect that new energy fluctuation influences the traction network.
How high-efficient with new forms of energy access traction power supply system, satisfy new forms of energy and consume nearby, reduce "abandon wind, abandon light" phenomenon, effectively restrain photovoltaic fluctuation and intermittent type nature and to pull the net influence, improve new forms of energy utilization ratio and stability and be the focus of current new forms of energy access traction power supply system research.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a new energy storage system with centralized access to a flexible traction transformer and a control method thereof, so as to realize the purposes of flexibly relating to the access quantity according to the sizes of various new energy, stably and efficiently accessing to a traction power supply system under the condition of relatively simple coordination control and improving the utilization rate of the new energy and regenerative braking energy.
In order to achieve the purpose of the invention, the invention adopts the technical scheme that:
in one aspect, a new energy storage system with centralized access to a flexible traction transformer comprises: the system comprises a flexible traction transformer, an isolated DC/DC converter, a direct current bus, a new energy power generation system and an energy storage system;
the flexible traction transformer is connected with the isolated DC/DC converter and is used for receiving energy of the isolated DC/DC converter;
the isolated DC/DC converter is respectively connected with the new energy power generation system and the energy storage system through a direct current bus and is used for keeping the voltage of a direct current link stable along with the power of the flexible traction transformer in the direct current link; the new energy power generation system is connected with the direct current bus and used for accessing power to a direct current link of the flexible traction transformer through the isolated DC/DC converter;
the energy storage system is connected with the direct current bus and used for stabilizing the intermittence and fluctuation of the new energy power generation system and storing surplus new energy and regenerative braking energy of the traction network;
the direct current bus is used as an energy convergence bus and is used for connecting the isolated DC/DC converter, the new energy power generation system and the energy storage system.
Preferably, the flexible traction transformer comprises a traction transformer, a multi-winding step-down transformer, a three-phase rectifier and a single-phase cascade rectifier which are connected in sequence.
Preferably, a direct current link between the three-phase rectifier and the single-phase cascade rectifier provides an access point for the new energy power generation system and the energy storage system to be connected to a flexible traction transformer through the isolated DC/DC converter.
Preferably, the single-phase inverter comprises a plurality of cascade modules, and the number of the cascade modules connected with new energy corresponds to the number of the isolated DC/DC converters one by one.
Preferably, the new energy power generation system adopts a direct current mode for networking, and the generated energy and the generated power of the new energy are adjustable.
Preferably, the energy storage system is connected to the direct current bus through a bidirectional DC/DC energy storage converter, and energy release and energy absorption of the direct current bus can be realized.
On the other hand, the control method of the new energy storage system intensively accessed to the flexible traction transformer comprises the following steps:
s1, acquiring and calculating power of each port of a new energy storage system;
s2, judging whether the new energy storage system is in a load state or not according to the power of a traction network, if so, recording that the energy flows to the traction network to be positive, and entering the step S3; otherwise, recording that the energy returned to the flexible traction transformer by the traction network is negative, and entering the step S8;
s3, judging whether the input power of each cascade module in the single-phase cascade inverter is larger than the new energy power of each cascade module accessed by the isolated DC/DC converter, and if so, entering the step S4; otherwise, entering step S5;
s4, judging whether the charge state of the energy storage system is larger than the minimum charge state of the energy storage system, if so, enabling the new energy power generation system to be in a maximum power point tracking state, enabling the energy storage system to absorb and store energy and supplementing the difference power by a three-phase power grid, otherwise, enabling the new energy power generation system to be in the maximum power point tracking state, stopping the energy storage system and supplementing the difference power by the three-phase power grid;
s5, judging whether the input power of each cascade module in the single-phase cascade inverter is smaller than the power of the cascade module in the new energy power generation system accessed to the isolation DC/DC converter, if so, entering the step S6, otherwise, enabling the new energy power generation system to be in a maximum power point tracking state, and stopping the energy storage system;
s6, judging whether the charge state of the energy storage system is smaller than the maximum charge state of the energy storage system, if so, entering the step S7, otherwise, reducing the power of the new energy power generation system to generate power, and stopping the energy storage system;
s7, judging whether the difference value between the new energy power generation power and the traction network power born by a cascade module connected to the new energy power generation system is larger than the maximum charging power of the energy storage system or not, if so, reducing the power of the new energy power generation system to generate power, and absorbing and storing the energy by the energy storage system; otherwise, the new energy power generation system is in a maximum power point tracking state, and the energy storage system absorbs and stores energy;
s8, judging whether the charge state of the energy storage system is smaller than the maximum charge state of the energy storage system, if so, entering a step S9, otherwise, stopping the new energy power generation system and stopping the energy storage system;
and S9, judging whether the power of the traction network is smaller than the maximum charging power of the energy storage system, if so, absorbing and storing energy by the energy storage system, reducing the power of the new energy power generation system to generate power, otherwise, absorbing and storing the energy by the energy storage system, and stopping the power generation of the new energy power generation system.
Preferably, step S1 specifically includes:
the method comprises the steps of collecting and calculating the power of an energy storage system, the power of a new energy power generation system, the maximum charging power of the energy storage system, the power of a traction network, the power of a three-phase power network, the power of an isolated DC/DC converter, the charge state of the energy storage system, the minimum charge state of the energy storage system and the maximum charge state of the energy storage system in the new energy storage system.
Preferably, the power control among the isolated DC/DC converters is independent, the output voltage is adjusted to follow the voltage of the direct current side of the corresponding single-phase cascade inverter, and the power balance of the cascade module is realized; and when the power of the traction network is larger than zero, each isolated DC/DC converter equally divides the power of the new energy subsystem and the power of the energy storage subsystem transmitted by the direct current bus.
Preferably, the flexible traction transformer is connected to the cascade module of the new energy through the isolated DC/DC, the energy of the new energy and the energy storage system is preferentially consumed, the energy of the three-phase power grid is used as a relaxation port, the power shortage is automatically supplemented, the new energy is preferentially supplied to the traction grid for consumption, and when the power of the new energy is larger than that of the traction grid, the surplus energy is stored by the energy storage system.
The invention has the following beneficial effects:
1. the method comprises the steps that multiple new energy sources such as photovoltaic energy, wind power and the like are gathered in a direct current mode, and are connected into a flexible traction transformer through an isolated DC/DC converter to be supplied to a traction power supply system, so that the multiple new energy sources are connected into the traction power supply system, and the green railway construction is assisted;
2. the energy storage system arranged on the direct current bus can effectively stabilize the energy fluctuation of new energy, reasonably store the new energy and regenerative braking energy and realize the optimized management of energy;
3. the method has the advantages that the access quantity is flexibly related according to the sizes of various new energy sources, the traction power supply system is stably and efficiently accessed under the condition of relatively simple coordination control, and the utilization rate of the new energy sources and the regenerative braking energy is improved;
4. the number of the access cascade modules can be reasonably and flexibly designed according to the capacity of the accessed new energy, and the new energy can be effectively consumed while the optimal cost and the maximum benefit are ensured;
5. new forms of energy are drawn the net through flexible traction transformer access, and photovoltaic fluctuation can not lead to the fact the influence to drawing the net, and this access mode does not relate to and draws the net and reform transform, easily engineering realization.
Drawings
Fig. 1 is a schematic system structure diagram of a new energy storage system centrally connected to a flexible traction transformer according to the present invention;
FIG. 2 is a schematic illustration of the configuration of a traction network under traction load/regenerative braking energy as provided in an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a traction network provided in an embodiment of the present invention in a locomotive regenerative braking condition;
FIG. 4 is a control block diagram of a traction network provided in an embodiment of the present invention under different operating conditions;
fig. 5 is a flowchart illustrating steps of a control method of a new energy storage system centrally connected to a flexible traction transformer according to the present invention;
fig. 6 is a comparison diagram of system simulation provided in the embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined by the appended claims, and all changes that can be made by the invention using the inventive concept are intended to be protected.
The invention provides a new energy storage system with centralized access to a flexible traction transformer and a control method;
as shown in fig. 1, in one aspect, a new energy storage system with centralized access to a flexible traction transformer includes: the system comprises a flexible traction transformer, an isolated DC/DC converter, a direct current bus, a new energy power generation system and an energy storage system;
the flexible traction transformer is connected with the isolated DC/DC converter and used for receiving energy of the isolated DC/DC converter;
optionally, the input side of the traction transformer is connected with a three-phase power grid, the traction transformer, the multi-winding step-down transformer, the three-phase rectifier and the single-phase cascade inverter output the power, and the output side of the traction transformer is connected with the single-phase traction power supply network, wherein a middle direct-current link between the three-phase rectifier and the single-phase cascade inverter is used for connecting the provided new energy system into a flexible traction transformer access point.
The isolated DC/DC converter is respectively connected with the new energy power generation system and the energy storage system through a direct current bus and is used for keeping the voltage of a direct current link stable along with the power of the flexible traction transformer in the direct current link;
optionally, one side of the isolated DC/DC converter is connected to a DC link of the flexible traction transformer, that is, between the three-phase rectifier and the single-phase cascade inverter, and the other side is connected to the DC bus.
The new energy power generation system is connected with the direct current bus and used for accessing power to a direct current link of the flexible traction transformer through the isolated DC/DC converter;
optionally, the new energy power generation system may be one or more of a photovoltaic power generation device, a wind power generation device, a hydrogen power generation device, a photo-thermal power generation device, a biochemical power generation device, and other renewable energy power generation devices, and energy is converged to the dc bus in a dc form through corresponding electric energy conversion.
The energy storage system is connected with the direct current bus and used for stabilizing the intermittence and fluctuation of the new energy power generation system and storing surplus new energy and regenerative braking energy of the traction network;
optionally, the energy storage system is one or more of water pumping energy storage, flywheel energy storage, super capacitor energy storage, chemical battery energy storage (lead-acid battery, nickel-cadmium battery, lithium battery, etc.), and other energy storage modes.
And the direct current bus is used as an energy convergence bus and is used for connecting the isolated DC/DC converter, the new energy power generation system and the energy storage system.
Preferably, the flexible traction transformer comprises a traction transformer, a multi-winding step-down transformer, a three-phase rectifier and a single-phase cascade rectifier which are connected in sequence.
Optionally, as shown in fig. 2, the single-phase cascaded inverter of the flexible traction transformer has a bidirectional energy flow characteristic, and when the single-phase cascaded inverter is in an inversion state and supplies energy to the traction network, it is recorded as a working mode 1: the power of a single cascade module inverter is recorded as Pinv, and the maximum inversion power is Pinv _ max; when energy is absorbed from the traction network in a rectification state, the operation mode is marked as 2: and the single cascade module rectifies the power to be Prec, and the maximum rectified power is precmax.
Preferably, a direct current link between the three-phase rectifier and the single-phase cascade rectifier provides an access point for the new energy power generation system and the energy storage system to be connected to the flexible traction transformer through the isolation type DC/DC converter.
Preferably, the single-phase inverter includes a plurality of cascade modules, and the number of the cascade modules connected to the DC link corresponds to the number of the isolated DC/DC converters one to one.
Optionally, in the embodiment of the present invention, the number of the cascade modules of the single-phase cascade inverter is denoted by n, the number of the modules of the direct current bus connected to the direct current link through the isolated DC/DC converter is denoted by m, and m is greater than or equal to 1 and less than or equal to n; the access direct-current link modules correspond to the isolated DC/DC converters one by one and are independent of each other, and the number m of the access modules can be flexibly designed according to different capacities of new energy in actual engineering; wherein: the isolated DC/DC converters appear in pairs at access points of all cascade modules between a three-phase rectifier and a single-phase cascade inverter, and are sequentially U1P, U1N, U P, U2N, …, umP and UmN; umP and UmN are connected to the three-phase rectifier Rm module output RmP and RmN of the mth module and the input CmP and CmN of the cascade inverter Cm module, respectively;
the positive pole output n # _ + of each module of the isolated DC/DC converter is connected to a middle connection point UnP of the rectifier Rn module and the single-phase cascade inverter _ Cn module, and the negative pole output n # _+ -of each module of the isolated DC/DC converter is connected to a middle connection point UnN of the rectifier Rn module and the single-phase cascade inverter _ Cn module; the isolated DC/DC converter has the characteristic of bidirectional energy flow, can transfer energy in two directions, and has controllable energy flow direction and power magnitude, and the isolated DC/DC converter comprises topologies such as a double-active full bridge, a full bridge resonant converter and the like, and can be in a two-level structure or a multi-level structure.
Preferably, the new energy power generation system adopts a direct current mode for networking, and the generated energy and the generated power of the new energy are adjustable.
Optionally, the new energy power generation system is networked in a direct current mode, various new energies are converted in corresponding electric energy modes to converge electric energy to the direct current bus, and the generated energy and the generated power of the new energies are adjustable.
Preferably, the energy storage system is connected to the direct current bus through the bidirectional DC/DC energy storage converter, and energy release and energy absorption of the direct current bus can be achieved.
Optionally, the energy storage system is connected to the DC bus through a bidirectional DC/DC energy storage converter, so that energy absorption/release to the DC bus can be quickly achieved.
As shown in fig. 3, in another aspect, a method for controlling a new energy storage system centrally connected to a flexible traction transformer includes the following steps:
s1, acquiring and calculating power of each port of a new energy storage system;
preferably, step S1 is specifically:
the method comprises the steps of collecting and calculating the power of an energy storage system, the power of a new energy power generation system, the maximum charging power of the energy storage system, the power of a traction network, the power of a three-phase power network, the power of an isolated DC/DC converter, the charge state of the energy storage system, the minimum charge state of the energy storage system and the maximum charge state of the energy storage system in the new energy storage system.
Optionally, after comprehensive determination is performed by detecting the power Pt of the traction network, the power Pne of the new energy power generation system, the state of charge SoC of the energy storage system, and the power Pess of the energy storage system, a control signal for mode switching of the isolated DC/DC converter, the bidirectional DC/DC energy storage converter, the new energy power generation system, the forward inversion of the single-phase cascade inverter, and the reverse cascade rectifier is provided, wherein the power Pt of the traction network is the power of the traction network connected to the single-phase cascade rectifier.
Optionally, the power of each port is calculated by obtaining voltage and current information of each port, where: the power of the traction network is recorded as Pt, when the traction network is under the load of the locomotive, the energy flow direction is recorded as positive, when the traction network is under the braking of the locomotive, the energy returned to the flexible traction transformer is recorded as negative; injecting energy into the traction network by the three-phase power grid and recording the energy as Pr; the new energy system takes energy injected into a direct current bus as positive, records as new energy power generation system power Pne, and meets Pne = Ppv + Pw + Poth, wherein Ppv is photovoltaic energy, pw is wind energy, and Poth is other new energy; the power of the energy storage system is denoted as Pess, the energy injected into the direct current bus is positive, and the energy absorbed from the direct current bus is negative, wherein the maximum charging/discharging power of the energy storage system is denoted as +/-Pess _ max, and the maximum value and the minimum value of the state of charge SoC of the energy storage system are denoted as SoCmax and SoCmin, namely: the maximum charge state of the energy storage system is recorded as SoCmax, the minimum charge state of the energy storage system is recorded as SoCmin, and in order to prevent the energy storage system from being damaged by over-charging and over-discharging, when the SoC of the energy storage system is more than or equal to the SoCmax or the SoC is less than or equal to the SoCmin, the energy storage system stops working; the isolated DC/DC converter power Pdc takes the power transmitted to a direct-current link as positive and the power absorbed from the direct-current link as negative, and meets the requirement that Pdc = Pess + Pne.
S2, judging whether the new energy storage system is in a load state or not according to the power of a traction network, if so, recording that the energy flows to the traction network to be positive, and entering the step S3; otherwise, recording that the energy returned to the flexible traction transformer by the traction network is negative, and entering the step S8;
as shown in fig. 4, optionally, when the power Pt of the traction grid is positive, the input power Pinv = Pt/n of each cascade module in the single-phase cascade inverter, the new energy accessed to each module through the isolated DC/DC converter is Pdc/m, and the isolated DC/DC converter power Pdc satisfies: pdc = Pne + energy storage system power pest.
S3, judging whether the input power of each cascade module in the single-phase cascade inverter is larger than the new energy power of each cascade module accessed by the isolated DC/DC converter, and if so, entering the step S4; otherwise, entering step S5;
s4, judging whether the charge state of the energy storage system is larger than the minimum charge state of the energy storage system, if so, enabling the new energy power generation system to be in a maximum power point tracking state, enabling the energy storage system to absorb and store energy and supplementing the difference power by a three-phase power grid, otherwise, enabling the new energy power generation system to be in the maximum power point tracking state, stopping the energy storage system and supplementing the difference power by the three-phase power grid;
s5, judging whether the input power of each cascade module in the single-phase cascade inverter is smaller than the power of the cascade module in the new energy power generation system accessed to the isolation DC/DC converter, if so, entering a step S6, otherwise, enabling the new energy power generation system to be in a maximum power point tracking state, and stopping the energy storage system;
s6, judging whether the charge state of the energy storage system is smaller than the maximum charge state of the energy storage system, if so, entering the step S7, otherwise, reducing the power of the new energy power generation system to generate power, and stopping the energy storage system;
s7, judging whether the difference value between the new energy power generation power and the traction network power born by a cascade module connected to the new energy power generation system is larger than the maximum charging power of the energy storage system or not, if so, reducing the power of the new energy power generation system to generate power, and absorbing and storing the energy by the energy storage system; otherwise, the new energy power generation system is in a maximum power point tracking state, and the energy storage system absorbs and stores energy;
optionally, if the input power Pt/n of each module of each cascade inverter is greater than or equal to the new energy accessed to each cascade module by the isolated DC/DC converter is Pdc/m, that is, pt/n is greater than or equal to Pdc/m, the traction grid power is provided by the three-phase grid power Pr and the isolated DC/DC converter power Pdc, pt = Pr + Pdc is satisfied, the new energy transmitted by the isolated DC/DC is preferentially consumed, the power difference is complemented by the three-phase grid power, and at this time, the new energy system is in a maximum power generation state; if the state of charge (SoC) of the energy storage system is larger than the minimum state of charge (SoCmin) of the energy storage system, the energy storage system injects energy into the direct current bus and meets the condition that the power Pdc of the isolated DC/DC converter is the sum of the power of the energy storage system and the power of a new energy power generation system, namely: pdc = Pess + Pne, and difference power Pr is complemented by a three-phase power grid, satisfying Pr = Pt-Pess-Pne; if the state of charge (SoC) of the energy storage system is less than or equal to the minimum state of charge (SoCmin) of the energy storage system, stopping working, and meeting the condition that the power of the isolated DC/DC converter is equal to the power of the new energy power generation system, namely meeting the condition that Pdc = Pne; at the moment, energy is supplied to the module which is not accessed with new energy by a three-phase power grid, and Pr = Pt-Pne is met;
optionally, if the input power Pt/n of each module of the cascade inverter is less than the new energy, which is accessed to each cascade module by the isolated DC/DC converter, of Pdc/m, that is, pt/n is less than Pdc/m, the energy, which is supplied to the traction network by the cascade module accessed to the new energy, is completely provided by the isolated DC/DC converter, and whether the power of the cascade module accessed to the isolated DC/DC converter by the new energy power generation system is less than or equal to the input power of each cascade module in the single-phase cascade inverter is further determined, that is: pne/m is less than or equal to Pt/n, the new energy is in maximum power generation, the energy storage system complements the difference power and injects the energy storage system power to the direct current bus, and the following conditions are met: pess = (Pt/n-Pne/m) × m, and the supplementary power of the three-phase power grid is as follows: pr = Pt (n-m)/n; when the power of a cascade module in a new energy power generation system accessed to an isolation DC/DC converter is greater than the input power of each cascade module in a single-phase cascade inverter, namely Pt/n is greater than Pdc/m, whether the state of charge SoC of an energy storage system is smaller than the maximum state of charge SoCmax of the energy storage system is further judged, if yes, whether the difference Pne-Pt m/n between the power Pne of the new energy power generation system and the power Pt m/n of a traction network born by the accessed new energy module is greater than the maximum charging power Pess _ max of the energy storage system is judged again, otherwise, the energy storage system stops working, the new energy power generation system reduces the power to generate power, and meets Pne = Pt m/n, and the output of a three-phase power network is Pr = Pt (n-m)/n; when the state of charge (SoC) of the energy storage system is smaller than the maximum state of charge (SoCmax) of the energy storage system and the difference value Pne-Pt m/n between the new energy power (Pne) and the traction network power Pt m/n borne by the cascade module connected to the new energy storage system is judged to be larger than the maximum charging power Pess _ max of the energy storage system, the energy storage system stores energy at the maximum charging power Pess _ max, the new energy power generation system reduces the power to generate power, and the requirement that Pne = Pt m/n + Pess _ max is met, otherwise, the new energy is in the MPPT state, namely: the new energy power generation system is in a maximum power point tracking state, and the energy storage system stores energy and meets the following requirements: and Pess = Pne-Pt m/n, three-phase power grid output, and Pr = Pt (n-m)/n.
S8, judging whether the charge state of the energy storage system is smaller than the maximum charge state of the energy storage system, if so, entering a step S9, otherwise, stopping the new energy power generation system and stopping the energy storage system;
and S9, judging whether the power of the traction network is smaller than the maximum charging power of the energy storage system, if so, absorbing and storing energy by the energy storage system, reducing the power of the new energy power generation system to generate power, otherwise, absorbing and storing the energy by the energy storage system, and stopping the power generation of the new energy power generation system.
As shown in fig. 5, when the power Pt of the traction network is negative, the traction network is in locomotive braking, and the regenerative braking energy is returned to the flexible traction transformer, at this time, if the state of charge SoC of the energy storage system is greater than or equal to the maximum state of charge socax of the energy storage system, the energy storage system stops working, the regenerative braking energy cannot be stored, and at this time, the regenerative braking energy is released or consumed;
if the state of charge (SoC) of the energy storage system is less than the maximum state of charge (SoCmax) of the energy storage system, further judging the magnitude of regenerative braking energy power and the maximum charging power (Pess _ max) of the energy storage system, wherein the regenerative braking energy power meets the magnitude of traction network power (Pt), namely, when the regenerative braking energy power is greater than the maximum charging power (Pt) of the energy storage system, namely Pt is greater than the Pess _ max, the energy storage system cannot completely store the regenerative braking energy, the energy storage system stores the power with the maximum charging power (Pess _ max), consumes the power which cannot be stored, meets the Pt-Pess _ max, and the new energy power generation system stops generating power; otherwise, when Pt is less than or equal to Pess _ max, the energy storage system stores energy, and the new energy power generation system reduces power to generate power, namely Pne = Pess _ max-Pt.
Preferably, the power control among the isolated DC/DC converters is independent, the output voltage is adjusted to follow the voltage of the direct current side of the corresponding single-phase cascade inverter, and the power balance of the cascade module is realized; and when the power of the traction network is larger than zero, each isolated DC/DC converter equally divides the power of the new energy subsystem and the power of the energy storage subsystem transmitted by the direct current bus.
As shown in fig. 5, optionally, the isolated DC/DC converter has a function of adjusting a voltage of a direct-current link of the flexible traction transformer, so that voltages Upn1, upn2, … … Upnm on direct-current sides of all cascade modules all follow a preset reference value Upn _ ref of the system, thereby ensuring power balance of all modules of the cascade inverter; the power control of the isolated DC/DC converter 1#, the isolated DC/DC converter 2#, the isolated DC/DC converter … … m # are mutually independent; when the power Pt of the traction network is greater than 0, the isolation type DC/DC converters equally divide new energy and stored energy power on the direct-current bus, and transmit power to the direct-current link, wherein the power is respectively P _1# = P _2# = … … = P _ m # = Pdc/m = (Pne + Pess)/m.
Preferably, the flexible traction transformer is connected to the cascade module of the new energy through the isolated DC/DC to preferentially consume the new energy and the energy storage system, the three-phase power grid energy is used as a relaxation port to automatically supplement power shortage, the new energy is preferentially supplied to the traction grid for consumption, and when the new energy power is greater than the traction grid power, the surplus energy is stored by the energy storage system.
The embodiment of the invention provides an overall power simulation experiment, wherein preset simulation parameters are as follows: the locomotive is loaded with 20MW (full power), and the maximum power generation amount of the new energy is 4MW;
in simulating natural condition changes, illumination: reduced illumination (0.42 s), increased illumination (0.65 s); temperature: under the standard condition of 45 ℃→ 25 ℃ (0.9 s switching), the implementation result is shown in fig. 6, and it can be seen that the flexible traction transformer and the new energy system are always in a complementary relationship in the dynamic changes of locomotive load and photovoltaic output, and jointly provide energy for the traction network load; in the process of locomotive load change, the photovoltaic power generation and energy storage state in the new energy system also changes, and the flexible traction transformer is used as the supplement of the new energy system, dynamically follows the energy change of the new energy system and supplements the power difference.
The novel energy source energy management system can be accessed to a cascade module of a new energy source through an isolated DC/DC, the energy of the new energy source and an energy storage system is preferentially consumed, the energy of a three-phase power grid is used as a relaxation port to automatically supplement the power shortage, the new energy source is preferentially supplied to a traction grid to be consumed, and when the power of the new energy source is greater than that of the traction grid, the surplus energy is stored by the energy storage system; the new energy power generation system is connected with the energy storage system through the direct current bus, the energy storage system can effectively stabilize the intermittence and fluctuation of the new energy power generation, the 'wind and light abandonment' is reduced, meanwhile, the new energy is connected into a traction network through the isolated DC/DC converter and the single-phase cascade inverter, and the fluctuation of the new energy cannot influence the traction network; the new energy is connected to the traction network through the flexible traction transformer, the transformation of the traction network is not involved, and the engineering realization is easy.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The principle and the implementation mode of the invention are explained by applying specific embodiments in the invention, and the description of the embodiments is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
Claims (4)
1. A control method for a new energy storage system intensively accessed to a flexible traction transformer is characterized by comprising the following steps:
s1, collecting and calculating power of each port of a new energy storage system;
s2, judging whether the new energy storage system is in a load state or not according to the power of a traction network, if so, recording that the energy flows to the traction network to be positive, and entering the step S3; otherwise, recording that the energy returned to the flexible traction transformer by the traction network is negative, and entering the step S8;
s3, judging whether the input power of each cascade module in the single-phase cascade inverter is larger than the new energy power of each cascade module accessed by the isolated DC/DC converter, and if so, entering the step S4; otherwise, entering step S5;
s4, judging whether the charge state of the energy storage system is larger than the minimum charge state of the energy storage system, if so, enabling the new energy power generation system to be in a maximum power point tracking state, enabling the energy storage system to absorb and store energy and supplementing the difference power by a three-phase power grid, otherwise, enabling the new energy power generation system to be in the maximum power point tracking state, stopping the energy storage system and supplementing the difference power by the three-phase power grid;
s5, judging whether the input power of each cascade module in the single-phase cascade inverter is smaller than the power of the cascade module in the new energy power generation system accessed to the isolation DC/DC converter, if so, entering a step S6, otherwise, enabling the new energy power generation system to be in a maximum power point tracking state, and stopping the energy storage system;
s6, judging whether the charge state of the energy storage system is smaller than the maximum charge state of the energy storage system, if so, entering the step S7, otherwise, reducing the power of the new energy power generation system to generate power, and stopping the energy storage system;
s7, judging whether the difference value between the new energy power generation power and the traction network power born by a cascade module connected to the new energy power generation system is larger than the maximum charging power of the energy storage system or not, if so, reducing the power of the new energy power generation system to generate power, and absorbing and storing the energy by the energy storage system; otherwise, the new energy power generation system is in a maximum power point tracking state, and the energy storage system absorbs and stores energy;
s8, judging whether the charge state of the energy storage system is smaller than the maximum charge state of the energy storage system, if so, entering a step S9, otherwise, stopping the new energy power generation system and stopping the energy storage system;
and S9, judging whether the power of the traction network is smaller than the maximum charging power of the energy storage system, if so, absorbing and storing energy by the energy storage system, reducing the power of the new energy power generation system to generate power, otherwise, absorbing and storing the energy by the energy storage system, and stopping the power generation of the new energy power generation system.
2. The control method according to claim 1, wherein step S1 is specifically:
the method comprises the steps of collecting and calculating the power of an energy storage system, the power of a new energy power generation system, the maximum charging power of the energy storage system, the power of a traction network, the power of a three-phase power network, the power of an isolated DC/DC converter, the charge state of the energy storage system, the minimum charge state of the energy storage system and the maximum charge state of the energy storage system in the new energy storage system.
3. The control method according to claim 1, wherein power control among the isolated DC/DC converters is independent, and output voltage is adjusted to follow the voltage of the direct current side of the corresponding single-phase cascade inverter, so that power balance of the cascade module is realized; and when the power of the traction network is larger than zero, each isolated DC/DC converter equally divides the power of the new energy subsystem and the power of the energy storage subsystem transmitted by the direct current bus.
4. The control method according to claim 1, characterized in that the flexible traction transformer is connected to the cascade module of the new energy through an isolated DC/DC, the energy of the new energy and the energy storage system is preferentially consumed, the energy of the three-phase power grid is used as a relaxation port to automatically supplement the power shortage, the new energy is preferentially supplied to the traction grid for consumption, and when the power of the new energy is greater than that of the traction grid, the surplus energy is stored by the energy storage system.
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