CN114447925A - Oscillation instability risk detection and instability source determination reduction method of new energy collection system - Google Patents

Abstract

The invention provides a new energy collection system oscillation instability risk detection and instability source judgment order reduction method, which comprises the steps of selecting the nth new energy power generation unit aiming at a new energy collection system consisting of N new energy power generation units, wherein the state space model of the nth new energy power generation unit is (A)_n,B_n,C_n,D_n) The nth similar new energy collection system is constructed by replacing the dynamic models of the rest new energy power generation units; constructing a network reactance matrix, and calculating and obtaining all characteristic values of the network reactance matrix; calculating and obtaining all oscillation modes by using an equivalent subsystem method of a full-order model of a similar new energy collection system; all oscillation modes of a similar new energy collection system can be fully damped by adjusting control parameters of a new energy power generation unit which may be an oscillation instability source, so that the original new energy collection system does not have a negative damping mode, namely, the risk of oscillation instability of the original new energy collection system is eliminated. The invention reduces the calculation amount and the data storage amount.

Description

Oscillation instability risk detection and instability source determination reduction method of new energy collection system

technical field

The invention belongs to the technical field of analysis and calculation of new energy bases, and in particular relates to a new energy collection system oscillation instability risk detection and instability source determination order reduction method, which is suitable for large-scale photothermal-photovoltaic-wind power new energy collection systems.

Background technique

With the development of new energy technology, my country's wind power, photovoltaic and other new energy power generation capacity continues to grow. The solar thermal power generation is connected to the grid through the steam turbine generator set, which has the response characteristics of the grid connection of the conventional unit, which can improve the stability of the wind power-photovoltaic power grid to a certain extent and balance a part of the wind and solar fluctuating power. As my country's CSP demonstration projects are successively connected to the grid for power generation, it is an inevitable trend for CSP to participate in grid scheduling control, and the emergence of CSP-PV-wind power new energy collection systems has become inevitable. At present, the research on photovoltaic and wind power generation by domestic and foreign scholars is relatively mature, and the theoretical research on CSP is still less.

The emergence of the solar thermal-photovoltaic-wind power new energy collection system will definitely have a significant impact on the safe and stable operation of the power grid. The new energy collection system may include different types of new energy power generation units, and their dynamic characteristics are different, which makes it difficult to directly use any method for stability analysis and instability source tracking. Large-scale new energy collection systems contain a huge number of new energy power generation units, especially large-scale wind farms often contain hundreds of wind power generation units. The state matrix of the new energy collection system model has an excessively high order, which means that Mode solving faces great difficulties, and even the disaster of dimensionality.

SUMMARY OF THE INVENTION

In view of the above-mentioned technical problems, the present invention proposes a method for detecting the oscillation instability risk and determining the instability source of a large-scale solar thermal-photovoltaic-wind power new energy collection system, and the specific technical scheme is as follows:

The new energy collection system oscillation instability risk detection and instability source judgment reduction method includes the following steps:

Step 1: For the new energy collection system composed of N new energy power generation units, select the nth new energy power generation unit whose state space model is (A _n , B _n , C _n , D _n ), and replace the rest by replacing The new energy generation unit dynamic model constructs the nth similar new energy collection system;

Step 2: Construct the network reactance matrix, calculate and obtain all its eigenvalues;

Step 3: Calculate and obtain all oscillation modes by using the equivalent subsystem method of the full-order model of the similar new energy collection system;

Step 4: By adjusting the control parameters of the new energy generation unit that may be the source of oscillation instability, all the oscillation modes of the similar new energy collection system can be fully damped, so that there is no negative damping mode in the original new energy collection system. Oscillation instability risk of the original new energy collection system.

The step 3 includes: if there is little damping or even negative damping in the obtained oscillation mode, the nth new energy power generation unit may bring the risk of oscillation instability to the original new energy collection system, and it may be oscillation instability. If the obtained oscillation modes are sufficiently damped, the nth new energy generating unit will not bring the risk of oscillation instability to the new energy collection system. If there is no negative damping mode in all similar new energy collection systems, the original new energy collection system does not have the risk of oscillation instability.

Beneficial effects of the present invention:

By constructing a similar new energy collection system and judging its oscillation stability to determine the oscillation stability of the original new energy collection system, the amount of calculation and data storage is reduced when faced with the determination of the oscillation stability of a large-scale new energy collection system.

Description of drawings

FIG. 1 is a basic flow chart of the method proposed by the present invention.

FIG. 2 is a structural diagram of a solar thermal-photovoltaic-wind power new energy collection system according to an embodiment.

Figure 3 shows the distribution of oscillation modes of the original new energy and similar new energy collection systems.

FIG. 4 shows the participation factors of the oscillation modes λ′ ₁ , λ′ ₂ and λ′ ₃ of the original new energy collection system of the embodiment.

FIG. 5 is a distribution diagram of oscillation modes of the original new energy and similar new energy collection systems after parameters are adjusted in the embodiment.

FIG. 6 is a nonlinear simulation image of the new energy collection system before and after parameter adjustment in the embodiment.

Detailed ways

The specific technical solutions of the present invention are described with reference to the embodiments.

As shown in Figure 1, it includes the following steps:

Step 1: For the new energy collection system composed of N new energy power generation units, select the nth new energy power generation unit whose state space model is (A _n , B _n , C _n , D _n ), and replace the rest by replacing The new energy generation unit dynamic model constructs the nth similar new energy collection system;

Step 2: Construct the network reactance matrix, calculate and obtain all its eigenvalues;

Step 3: Calculate and obtain all oscillation modes by using the equivalent subsystem method of the full-order model of the similar new energy collection system;

Step 4: By adjusting the control parameters of the new energy generation unit that may be the source of oscillation instability, all the oscillation modes of the similar new energy collection system can be fully damped, so that there is no negative damping mode in the original new energy collection system. Oscillation instability risk of the original new energy collection system.

The step 3 includes: if there is little damping or even negative damping in the obtained oscillation mode, the nth new energy power generation unit may bring the risk of oscillation instability to the original new energy collection system, and it may be oscillation instability. If the obtained oscillation modes are sufficiently damped, the nth new energy generating unit will not bring the risk of oscillation instability to the new energy collection system. If there is no negative damping mode in all similar new energy collection systems, the original new energy collection system does not have the risk of oscillation instability.

Beneficial effects of the present invention:

By constructing a similar new energy collection system and judging its oscillation stability to determine the oscillation stability of the original new energy collection system, the amount of calculation and data storage is reduced when faced with the determination of the oscillation stability of a large-scale new energy collection system.

The concrete method of the present invention is as follows:

The solar thermal-photovoltaic-wind power new energy collection system includes a variety of power generation units, such as solar thermal power generation units, photovoltaic power generation units and wind power generation units. Linearize the models of these new energy generating units, which can all be represented by their respective state space models. The linearized state space model of the kth new energy generation unit can be written as:

Among them, X _k is the column vector of all state variables of the kth new energy power generation unit; A _k is the linearized state space matrix, B _k is the linearized control matrix, C _k is the linearized output matrix, and Δ represents the state variable or A small increment of the column vector of the state variable; the state space model of the kth new energy generating unit can be represented by (A _k , B _k , C _k , D _k ). .

The linearized network voltage equation of the solar thermal-photovoltaic-wind new energy collection system with N new energy generation units can be written as:

ΔV=Z _f ΔI (2)

in,

Equation (3) can be obtained from equations (1) and (2), which is the full-order linearized state space model of the solar thermal-photovoltaic-wind power new energy collection system with N new energy power generation units:

in,

A _f =diag[A _k ]+diag[B _k ](EZ _f diag[D _k ]) ^-1 diag[C _k ]; E is the identity matrix.

The main theoretical basis of the present invention is: consider replacing all the power generation units of the new energy collection system with the same new energy power generation unit with similar dynamic characteristics. The oscillation mode of the full-order model corresponds to the original new energy collection system. The oscillation mode damping of the new energy generation unit will be worse or better, and the oscillation mode frequency will also increase or decrease. This means that the oscillation modes of N similar new energy collection systems will expand around the corresponding oscillation modes of the original new energy collection system on the complex plane, that is, cover the area occupied by the oscillation modes of the original new energy collection system. If the areas occupied by the oscillation modes of N similar new energy collection systems are all located in the left half plane of the complex plane, then the oscillation modes of the covered original new energy collection systems are also located in the left half plane, that is, there is no risk of oscillation instability; The area occupied by the oscillation modes of N similar new energy collection systems is partly located in the right half plane of the complex plane, so the original new energy collection system may have the risk of oscillation instability.

Consider selecting any new energy power generation unit in a new energy collection system with N power generation units, and replace the dynamic models of the rest of the new energy power generation units with the dynamic models of the new energy power generation units, a virtual power generation unit can be constructed. Similar to the new energy collection system. Similarly, selecting another new energy power generation unit can also construct a similar new energy collection system, so a total of N similar new energy collection systems can be obtained. The full-order model of each similar new energy collection system can be obtained by the following methods:

1) Select any new energy power generation unit, and represent it as the nth new energy power generation unit of the new energy collection system, and its state space model is (A _n , B _n , C _n , D _n );

2) Use the state space model of the nth new energy power generation unit to replace the state space models of all other new energy power generation units in the new energy collection system, namely

(A _k ,B _k ,C _k ,D _k )=(A _n ,B _n ,C _n ,D _n ); k≠n,k=1,2,…N (4)

3) According to equations (1), (2) and (4), the state state space model of a similar new energy collection system can be obtained:

in,

A _r (n)=diag[A _n ]+diag[B _n ](EZ _f diag[D _n ]) ⁻¹ diag[C _n ].

According to this method, the full-order models of N similar new energy collection systems can be obtained. If the number of power generation units contained in the original new energy collection system is too large, that is, when N is large, it means that the amount of calculation is very large, and there is a possibility of dimension disaster during calculation. Therefore, it is an important aspect to reduce the amount of calculation to calculate the oscillation modes of similar new energy collection systems by using the reduced order method.

In general, the line reactance is much smaller than the line resistance, so Z _f can be written as:

in,

From this, the equivalent model of the full-order model of the similar new energy collection system can be obtained:

A _r (n)=diag[A _n ]+diag[B _n ](EX _f diag[D _n ]) ^-1 diag[C _n ] (7)

The network reactance matrix X _e that defines the new energy collection system is shown in formula (8), and ζ _n (n=1,2,...,N) is the eigenvalue of the network reactance matrix X _e . Since X _e is a symmetric matrix and all its elements are positive real numbers, ζ _n ≥ 0.

There exists a transformation matrix such that:

T ^-1 A _r (n) T=diag[A _n +ζ _i B _n H(E-ζ _i D _n H) ^-1 C _n ] (9)

Among them, ζ _i (i=1,2,...,N) is all the eigenvalues of the network reactance matrix X _e .

According to equation (9), the equivalent model of the full-order model of a similar new energy collection system can be represented by N equivalent subsystems, which greatly reduces the matrix dimension during model calculation.

Combined with the above-mentioned order reduction method, the basic flow of a method for oscillation instability risk detection and instability source determination suitable for a large-scale solar thermal-photovoltaic-wind power new energy collection system is shown in Figure 1.

When this method is applied to an actual power system, the following steps can be taken:

1) Select the nth new energy power generation unit whose state space model is (A _n , B _n , C _n , D _n ), and construct the nth similar new energy collection system by replacing the dynamic models of other new energy power generation units ;

2) Construct the network reactance matrix shown in formula (8), calculate and obtain all its eigenvalues ζ _i (i=1,2,...,N);

3) Using the equivalent subsystem method of the full-order model of the similar new energy collection system shown in equation (9), calculate and obtain all the oscillation modes. If there is little damping or even negative damping in the obtained oscillation mode, the nth new energy generation unit may bring the risk of oscillation instability to the original new energy collection system, and it may be one of the sources of oscillation instability; If the oscillation modes are fully damped, the nth new energy generating unit will not bring the risk of oscillation instability to the new energy collection system. If there is no negative damping mode in all similar new energy collection systems, the original new energy collection system does not have the risk of oscillation instability.

4) By adjusting the control parameters of the new energy generation unit that may be the source of oscillation instability, all the oscillation modes of the similar new energy collection system can be fully damped, so that there is no negative damping mode in the original new energy collection system, that is, to eliminate the original new energy collection system. Oscillation instability risk of new energy collection system.

The method is demonstrated below with an example, in which the nonlinear simulation results are obtained by applying the improved Euler method.

The structure of the solar thermal-photovoltaic-wind power new energy collection system is shown in Figure 2, and the external power grid connected to it is a four-machine two-area system. This new energy collection system consists of 5 power generation fields, namely PMSG field, DFIG field, CSP field, PV field and hybrid field. It is considered that the power generation units in each power station are produced and provided by the same manufacturer, that is, the factory parameters of the new energy power generation units in each field are the same. The line impedance of the collection system connected to the external power grid is Z ₁ =0.007+j0.07; the line impedance of each power plant to the common connection point of the collection system is Z ₂ =0.003+j0.03; PMSG, DFIG, PV field and mixed field The line impedance within the CSP field is Z ₃ =0.001+j0.01; the line impedance within the CSP field is Z ₄ =0.002+j0.02. The active output of each power generation unit is shown in Table 1.

Table 1 Active output of each power generation unit

The oscillation mode calculated by the full-order model of the new energy collection system according to Equation (3) is represented by a black hollow circle, and the boundary of the region occupied by the oscillation mode is outlined by a black solid line; the oscillation mode of a similar new energy collection system calculated by Equation (9) The mode is represented by a black triangle, the boundary of the area it occupies is outlined by a black dotted line, and the influence of the line resistance is ignored in the calculation; when the influence of the line resistance is considered, the oscillation mode of a similar new energy collection system is represented by a black cross, and its occupied Region boundaries are outlined with black dashed lines, as shown in Figure 3.

According to the results shown in Figure 3, it can be seen that the area occupied by the oscillation mode of the similar new energy collection system on the complex plane does indeed cover the area occupied by the oscillation mode of the original new energy collection system; the part of the area where the similar new energy collection system exists is located in the right half The plane, that is, the original new energy collection system may have the risk of oscillation instability; the area occupied by the oscillation mode of the original new energy collection system calculated by the full-order model of equation (3) exists in the right half plane, that is, the original new energy collection system. There is indeed a risk of oscillation instability. This result confirms that the method proposed in the present invention can detect the risk of oscillation instability. When considering line resistance and ignoring line resistance, the area occupied by similar new energy collection systems is basically the same.

As shown in Figure 3: Some similar new energy collection systems have negative damping modes, specifically similar new energy collection systems constructed by No. 1-15 DFIG, No. 7-10 and No. 17-20 PMSGs. The specific values of the negative damping mode are as follows shown in Table 2.

Table 2 Negative damping mode

After adjusting the control parameters of the corresponding new energy power generation unit, the negative damping modes of each similar new energy collection system are shown in Table 3.

Table 3 Negative damping mode after parameter adjustment

It can be seen from Table 3 that the original negative damping mode has been effectively improved after parameter adjustment, eliminating the risk of oscillation instability. In order to determine the correctness of the method for determining the source of instability, the participation factors of the negative damped oscillation modes λ′ ₁ , λ′ ₂ and λ′ ₃ are calculated using the full-order model of the original new energy collection system. The calculation results are shown in Figure 4. In addition, according to Fig. 3, the pattern distribution diagram of each new energy collection system after parameter adjustment is drawn, as shown in Fig. 5.

The results in Figure 4 show that the negative damping mode of the original new energy collection system is indeed mainly related to No. 1-15 DFIG, No. 7-10 and No. 17-20 PMSG, which confirms the correctness of the above method for determining the source of instability. According to the results shown in Figure 5, after the parameters are adjusted, the original negative damping mode of the original new energy collection system disappears, and the improvement is shown in Table 4; the risk of oscillation instability is eliminated, and the new energy collection system at this time is stable.

Table 4 Changes of λ′ ₁ , λ′ ₂ and λ′ ₃ after parameter adjustment

Figure 6 shows the nonlinear simulation images before and after parameter adjustment. When the fault is set to 0.5s, the mechanical torque of PMSG No. 2 decreases by 10%, and returns to normal at 0.6s. By comparing the nonlinear simulation results before and after parameter adjustment, it can be seen that: before parameter adjustment, the original new energy collection system has the risk of oscillation instability, and oscillation instability will occur when encountering small disturbances; after parameter adjustment, the original new energy collection system eliminates In order to avoid the risk of oscillation instability, even when encountering small disturbances, oscillation instability will not occur. This result verifies the feasibility of the method for detecting the oscillation stability risk of the large-scale new energy collection system and determining the oscillation instability source proposed by the present invention.

This embodiment is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. , all should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (2)

1. The method for detecting the risk of oscillation instability and determining the order of the instability source of the new energy collection system is characterized by comprising the following steps:

step 1: aiming at a new energy collection system consisting of N new energy power generation units, selecting the nth new energy power generation unit, wherein the state space model of the nth new energy power generation unit is (A)_n,B_n,C_n,D_n) The nth similar new energy collection system is constructed by replacing the dynamic models of the rest new energy power generation units;

step 2: constructing a network reactance matrix, and calculating and obtaining all characteristic values of the network reactance matrix;

and step 3: calculating and obtaining all oscillation modes by using an equivalent subsystem method of a full-order model of a similar new energy collection system;

and 4, step 4: by adjusting the control parameters of the new energy power generation unit which may be an oscillation instability source, all oscillation modes of a similar new energy collection system can be fully damped, and further, the original new energy collection system does not have a negative damping mode, namely, the oscillation instability risk of the original new energy collection system is eliminated.

2. The new energy collection system oscillation instability risk detection and instability source determination order reduction method according to claim 1, wherein the step 3 comprises the following processes:

if the obtained oscillation mode has the condition of very small damping or even negative damping, the nth new energy power generation unit may bring the risk of oscillation instability to the original new energy collection system, and may be one of oscillation instability sources;

if the obtained oscillation modes are all fully damped, the nth new energy power generation unit cannot bring oscillation instability risks to the new energy collection system. And if all similar new energy collection systems do not have a negative damping mode, the original new energy collection system does not have the risk of oscillation instability.

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