A transient power frequency overvoltage suppression parameter setting method, device and medium

Abstract

The present invention discloses a transient power frequency overvoltage suppression parameter setting method, device and medium. The present invention determines the system overshoot limit of the fault recovery process according to the preset transient power frequency overvoltage limit, increases the system damping ratio by adjusting the phase-locked loop integral parameter, thereby reducing the system overshoot, so that the system overshoot is less than the overshoot limit, and finally achieves the purpose of suppressing the transient power frequency overvoltage at the machine end of the converter during the fault recovery process, and improves the stability of the converter grid-connected system. The present invention can effectively suppress the transient power frequency overvoltage when the system meets the dynamic performance, so that the overvoltage value is lower than the limit, thereby improving the system stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of transient stability control of electric power systems, and in particular relates to a method, a device and a medium for setting transient power frequency overvoltage suppression parameters of a grid-following converter. Background Art

[0002] With the continuous development of new energy, a large number of new energy sources are connected to the power grid through long-distance transmission in the Sha, Go and Huang areas. There is a problem of weak voltage support capacity at the grid connection point. During faults, transient power frequency overvoltage may occur at the converter end or the grid-connected bus, which is not conducive to stable operation of the system.

[0003] At present, most new energy sources adopt the grid-following control mode, for example, they use the phase-locked loop to achieve synchronous operation with the power grid. The existing converter control strategy is to improve the voltage support capacity of the grid connection point during the fault by entering the low voltage ride-through control, but it does not consider the transient power frequency overvoltage problem at the converter machine end caused by the dynamic characteristics of the second-order phase-locked loop system during the fault recovery process, which may cause the new energy to be disconnected from the grid and cause serious power loss.

[0004] At present, there are two methods to suppress transient power frequency overvoltage: the first is to suppress transient power frequency overvoltage by reasonably configuring reactive power compensation devices. For example, in the article "Optimal Configuration of Distributed Phase Modulators in High Proportion New Energy DC Sending-End Systems", the particle swarm algorithm is used to find the optimal configuration scheme of distributed phase modulators to suppress transient power frequency overvoltage, but the configuration of phase modulators increases the system operation cost; the second is control strategy optimization. For example, in the article "A P-Q Coordination Based Model Predictive control for DFIG High-Voltage RideThrough", by comparing time domain simulations under different phase-locked loop parameters, basic regulations and qualitative guidance are provided for parameter setting, but there is a lack of theoretical guidance and no more practical parameter setting method is proposed.

[0005] In summary, a practical method for suppressing transient power frequency overvoltage is urgently needed. Summary of the invention

[0006] In order to solve at least one of the problems existing in the prior art, the present invention provides a method, device and medium for setting the transient power frequency overvoltage suppression parameters of a grid-connected converter, which can enable the converter grid-connected system to effectively suppress overvoltage transiently while meeting the dynamic performance, so that the overvoltage value is lower than the limit value, thereby improving the system stability.

[0007] In order to achieve the purpose of the present invention, a method for setting transient power frequency overvoltage suppression parameters of a grid-following converter of the present invention comprises the following steps:

[0008] Step (1): Measure the active current value output by the converter during the fault period using the current sensor in the grid-connected converter. , the active current value , Transient power frequency overvoltage limit , proportional parameters of the phase-locked loop controller Preset values ​​of three parameters and integral parameters The initial values ​​are respectively input into the controller of the grid-following converter;

[0009] Step (2): Combine the active current value output by the grid-connected converter during the fault period , calculate the phase angle value of the phase-locked loop tracking during the fault recovery process ;

[0010] Step (3): Combined with transient power frequency overvoltage limit , calculate the phase angle limit of the phase-locked loop ;

[0011] Step (4): The phase-locked loop tracking phase angle value calculated according to step (2) And the phase angle limit of the phase-locked loop calculated in step (3) , calculate the system overshoot limit ;

[0012] Step (5): Calculate the peak time of the phase-locked loop dynamic process during fault recovery according to the following formula:

[0013]

[0014] In the formula, m is the adjustment factor;

[0015] Step (6): Calculate the real value of the extreme point , the extreme imaginary part value , natural frequency , differential coefficient , Damping ratio and the damping angle ;

[0016] Step (7): The peak time obtained from step (5) and the real part of the extreme point obtained in step (6) , the extreme imaginary part value , natural frequency , differential coefficient , Damping ratio and damping angle , the system overshoot during the fault recovery process is calculated by the following formula:

[0017]

[0018] Step (8): Compare system overshoot limits and system overshoot during fault recovery , select whether to adjust the integral parameter of the phase-locked loop controller The value of

[0019] Step (9): If the integral parameter of the phase-locked loop controller in step (8) Adjust to the new value and repeat steps (5)-(8) to recalculate , until satisfied .

[0020] Furthermore, the phase-locked loop tracks the phase angle value during the fault recovery process. The calculation formula is:

[0021]

[0022] In the formula, Indicates the grid voltage value; It indicates the reactance per unit value between the grid connection point and the grid. Indicates the active current value output by the converter during a fault.

[0023] Furthermore, the phase angle limit of the phase-locked loop The calculation formula is:

[0024]

[0025] In the formula, Represents the reactive power compensation coefficient, Indicates the grid voltage value, It indicates the reactance per unit value between the grid connection point and the grid. Indicates the active current value output by the converter during the fault period. Indicates the transient power frequency overvoltage limit.

[0026] Furthermore, the calculation formula of the reactive power compensation coefficient is: , It indicates the per unit reactance value between the grid connection point and the grid.

[0027] Furthermore, the system overshoot limit The calculation formula is , where Indicates the phase angle value tracked by the phase-locked loop. Indicates the phase angle limit of the phase-locked loop.

[0028] Furthermore, in step (6), the real part value of the extreme point Calculated by the following formula:

[0029]

[0030] In the formula, Represents the proportional parameter of the phase-locked loop controller.

[0031] The imaginary value of the pole Calculated by the following formula:

[0032]

[0033] In the formula, represents the proportional parameter of the phase-locked loop controller, represents the integral parameter of the phase-locked loop controller;

[0034] The natural frequency Calculated by the following formula:

[0035]

[0036] In the formula, represents the integral parameter of the phase-locked loop controller;

[0037] The differential coefficient Calculated by the following formula:

[0038]

[0039] In the formula, represents the proportional parameter of the phase-locked loop controller, represents the integral parameter of the phase-locked loop controller;

[0040] The damping ratio Calculated by the following formula:

[0041]

[0042] In the formula, represents the proportional parameter of the phase-locked loop controller, represents the integral parameter of the phase-locked loop controller;

[0043] The damping angle Calculated by the following formula:

[0044]

[0045] In the formula, represents the proportional parameter of the phase-locked loop controller, represents the integral parameter of the phase-locked loop controller;

[0046] Furthermore, step (5) performs peak time The calculation includes the following steps:

[0047] Step 1): Letm =0, calculate the initial peak time;

[0048] Step 2): If the initial peak time calculated in step 1) is less than zero, then let m = m +1, recalculate the peak time according to the peak time calculation formula provided in step (5) , until the peak time is reached ; If the initial peak time calculated in step 1) is greater than zero, then the initial peak time is directly used as the peak time.

[0049] Furthermore, in step (8), the integral parameter of the phase-locked loop controller is adjusted The steps include:

[0050] Compare the system overshoot limit calculated in step (4) The system overshoot calculated in step (7) ,like ,but ;like , then the integral parameter is equal to the initial value of the integral parameter of the phase-locked loop controller entered in step (1).

[0051] The present invention also provides a computer device, comprising a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above method.

[0052] The present invention also provides a computer-readable storage medium on which a computer program or instruction is stored. When the computer program or instruction is executed by a processor, the steps of the above method are implemented.

[0053] Compared with the prior art, the present invention can at least achieve the following beneficial effects: (1) The present invention can determine the system overshoot limit of the fault recovery process according to the converter output active current value measured during the fault and the preset transient power frequency overvoltage limit, and increase the system damping ratio by adjusting the phase-locked loop integral parameter, thereby reducing the system overshoot, so that the system overshoot is less than the overshoot limit, thereby achieving the purpose of suppressing the transient power frequency overvoltage at the converter machine end during the fault recovery process.

[0054] (2) The present invention enables the system to effectively suppress transient power frequency overvoltage while meeting dynamic performance requirements, so that the overvoltage value is lower than the limit value, thereby improving the stability of the converter grid-connected system. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The present invention is a flow chart of a method for setting transient power frequency overvoltage suppression parameters of a grid-following converter in an embodiment of the present invention.

[0056] Figure 2 Schematic diagram of a simulation system in an embodiment of the present invention.

[0057] Figure 3 It is a comparison curve diagram of the time domain variation of the active current output by the grid-type converter in the embodiment of the present invention.

[0058] Figure 4 1 is a comparison curve diagram of the phase angle time domain variation of the phase-locked loop in the embodiment of the present invention.

[0059] Figure 5 It is a comparison curve diagram of the time domain variation of the terminal voltage of the grid-type converter in the embodiment of the present invention. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] See also Figure 1 The present invention provides a method for setting transient power frequency overvoltage suppression parameters of a grid-connected converter, comprising the following steps:

[0062] Step (1): Measure the active current value output by the grid-following converter during the fault period through the current sensor in the grid-following converter , input the integral parameter to the controller of the grid-type converter The initial value of the transient power frequency overvoltage limit is , proportional parameters of the phase-locked loop controller The preset value of

[0063] In some embodiments of the present invention, a converter grid-connected system is built on a PSCAD / EMTDC simulation platform and a time domain simulation is performed, such as Figure 2 As shown in the figure, the grid-following converter in the simulation system is connected to the grid point through the filter reactance, and the per-unit value of the filter reactance is Indicates that the grid connection point is connected to a reactive power compensation device, and the reactive power compensation reactance standard value is The grid connection point is connected to the grid through impedance, and the impedance is represented by vector Represents, where R represents the resistance value between the grid connection point and the grid, and j is the identifier of the imaginary part.

[0064] As a specific example, the parameters of the simulation system are: the system base capacity is 20MVA, the base voltage is 35kV, and the base impedance is 61.25Ω. 0.5pu, resistance per unit value 0.01pu, filter reactance per unit value 0.0225pu, reactive compensation reactance per unit value It is -3.732pu.

[0065] Measuring the active current value output by the grid-connected converter during a fault , determine the transient power frequency overvoltage limit based on the converter withstand voltage capability In this example, the transient power frequency overvoltage limit value during the fault recovery process is The value is 1.1 (other values ​​are possible in other examples), and the proportional parameter of the phase-locked loop controller is , the initial value of the integration parameter . By using the simulation system to simulate, we can get the following Figure 3 The output active current time domain variation comparison curve shown in the figure shows that the output active current value of the grid-type converter during the fault period is measured. .

[0066] In the following steps, substitute the values ​​of the corresponding parameters given above and perform the calculations together.

[0067] Step (2): Calculate the phase angle value of the phase-locked loop tracking during the fault recovery process according to the following formula: :

[0068]

[0069] In the formula, the grid voltage value is , the output active current value of the grid-type converter during the fault period , reactance per unit value between the grid connection point and the grid =0.5pu.

[0070] Step (3): Calculate the phase angle limit of the phase-locked loop according to the following formula: :

[0071]

[0072] In the formula, the reactive power compensation coefficient , Transient power frequency overvoltage limit =1.1.

[0073] Step (4): The phase-locked loop tracking phase angle value calculated according to step (2) And the phase angle limit of the phase-locked loop calculated in step (3) , calculate the system overshoot limit :

[0074]

[0075] Step (5): Calculate the peak time of the phase-locked loop dynamic process during fault recovery :

[0076]

[0077] In the formula, m is the adjustment factor, represents the proportional parameter of the phase-locked loop controller, Represents the integral parameter of the phase-locked loop controller.

[0078] This step includes the following sub-steps when determining the peak time:

[0079] Step 1): Let m =0, calculate the initial peak time;

[0080] Step 2): If the initial peak time calculated in step 1) is less than zero, then let m = m +1, recalculate the peak time according to the peak time calculation formula , until satisfied , determined as the peak time to be obtained; if the initial peak time calculated in step 1) is greater than zero, the calculated initial peak time is directly used as the peak time.

[0081] Step (6): Calculate the real value of the extreme point , the extreme imaginary value , natural frequency , differential coefficient b , Damping ratio and the damping angle , the specific calculation formula includes:

[0082] Calculate the real value of the extreme point :

[0083]

[0084] Calculate the imaginary value of the pole :

[0085]

[0086] Calculate the natural frequency :

[0087]

[0088] Calculate the differential coefficient :

[0089]

[0090] Calculate the damping ratio :

[0091]

[0092] Calculate the damping angle :

[0093]

[0094] Step (7): The peak time calculated according to step (5) , the real part of the extreme point calculated in step (6) , the extreme imaginary value , natural frequency , differential coefficient , Damping ratio and damping angle , calculate the system overshoot during the fault recovery process :

[0095]

[0096] Step (8): Compare the system overshoot limit calculated according to step (4) The system overshoot during the fault recovery process calculated in step (7) is , and determine whether to adjust the integral parameters The value of .

[0097] In the above calculation results, ,make .

[0098] Step (9): Reduce the integral parameter of the phase-locked loop controller After taking the value of , repeat steps (5) to (8) until the . Calculate the integral parameters of the phase-locked loop controller that ultimately meets the requirements =120, the calculated overshoot of the fault recovery process system Less than the system overshoot limit , meet the transient power frequency overvoltage limit requirements.

[0099] In some embodiments of the present invention, in order to verify the effectiveness of the proposed method for setting parameters of transient power frequency overvoltage suppression for a grid-following converter, the following experiment is designed:

[0100] It is set that a three-phase short circuit fault occurs on the grid side within 6s and the fault duration is 0.1s.

[0101] The experimental comparison scheme includes:

[0102] 1) Scheme 1: The integral parameter of the phase-locked loop controller of the grid-connected converter in the converter grid-connected system adopts the initial value as a blank control;

[0103] 2) Scheme 2: The grid-following converter in the converter grid-connected system uses this method to adjust the integral parameter of the phase-locked loop controller (transient power frequency overvoltage limit value , the proportional parameters of the phase-locked loop controller are directly set at the beginning of the experiment, and this method does not adjust these two parameters);

[0104] The simulation results of the two schemes are compared. Figure 4 and Figure 5 As shown, from Figure 4 It can be seen from the figure that after the transient power frequency overvoltage parameters are set using this method, the phase angle overshoot of the phase-locked loop in the fault recovery process is significantly reduced; Figure 5 It can be seen that after the transient power frequency overvoltage parameter is adjusted by this method, the transient power frequency overvoltage is reduced from 1.2pu to the limit value of 1.1pu. Therefore, the transient power frequency overvoltage parameter adjustment method provided by the present invention can effectively suppress the transient power frequency overvoltage at the machine end of the converter during the fault recovery process and improve the transient stability of the system.

[0105] In combination with the setting method provided in the above embodiments, in some embodiments of the present invention, a computer device is also provided, including a memory, a processor and a computer program stored in the memory, and the processor executes the computer program to implement the steps of the method described in the above embodiments.

[0106] In combination with the setting method provided in the above embodiments, in some embodiments of the present invention, a computer-readable storage medium is also provided, on which a computer program or instructions are stored, and when the computer program or instructions are executed by a processor, the steps of the method described in the above embodiments are implemented.

[0107] The step numbers in the aforementioned embodiments are only provided for the convenience of explanation and description, and no limitation is imposed on the order of the steps. The execution order of the steps in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0108] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for setting transient power frequency overvoltage suppression parameters, characterized in that: The following steps are involved: Step (1): Measure the active current value output by the converter during the fault period using the current sensor in the grid-connected converter. , the active current value , Transient power frequency overvoltage limit and the proportional parameters of the phase-locked loop controller Preset values ​​and integration parameters The initial value is input into the controller of the grid-following converter; Step (2): Combine the active current value output by the grid-connected converter during the fault period , calculate the phase angle value of the phase-locked loop tracking during the fault recovery process ; Step (3): Combined with the transient power frequency overvoltage limit , calculate the phase angle limit of the phase-locked loop ; Step (4): The phase-locked loop tracking phase angle value calculated according to step (2) And the phase angle limit of the phase-locked loop calculated in step (3) , calculate the system overshoot limit ; Step (5): Calculate the peak time of the phase-locked loop dynamic process during fault recovery according to the following formula: In the formula, m is the adjustment factor; Step (6): Calculate the real value of the extreme point , the extreme imaginary value , natural frequency , differential coefficient , Damping ratio and the damping angle ; The real value of the extreme point Calculated by the following formula: The imaginary value of the pole Calculated by the following formula: The natural frequency Calculated by the following formula: The differential coefficient Calculated by the following formula: The damping ratio Calculated by the following formula: The damping angle Calculated by the following formula: Step (7): The peak time obtained from step (5) and the real part of the extreme point obtained in step (6) , the extreme imaginary value , natural frequency , differential coefficient , Damping ratio and damping angle , the system overshoot during the fault recovery process is calculated by the following formula: Step (8): Compare system overshoot limits and system overshoot during fault recovery , choose whether to adjust the integral parameters The value of Step (9): If the integral parameter in step (8) Adjust to the new value and repeat steps (5) to (8) to recalculate the system overshoot during the fault recovery process. , until satisfied .

2. A transient power frequency overvoltage suppression parameter setting method according to claim 1, characterized in that: The fault recovery process phase-locked loop tracks the phase angle value The calculation formula is In the formula, Indicates the grid voltage value; It indicates the per unit reactance value between the grid connection point and the grid.

3. A transient power frequency overvoltage suppression parameter setting method according to claim 1, characterized in that: The phase-locked loop phase angle limit The calculation formula is In the formula, Represents the reactive power compensation coefficient, Indicates the grid voltage value, It indicates the per unit reactance value between the grid connection point and the grid.

4. A transient power frequency overvoltage suppression parameter setting method according to claim 3, characterized in that: The calculation formula of the reactive power compensation coefficient is: , It indicates the per unit reactance value between the grid connection point and the grid.

5. A transient power frequency overvoltage suppression parameter setting method according to claim 1, characterized in that: The system overshoot limit The calculation formula is .

6. A transient power frequency overvoltage suppression parameter setting method according to claim 1, characterized in that: Step (5) Peak time The calculation includes the following steps: Step 1): Let m =0, calculate the initial peak time; Step 2): If the initial peak time calculated in step 1) is less than zero, then let m = m +1, recalculate the peak time according to the peak time calculation formula provided in step (5) , until satisfied ; If the initial peak time calculated in step 1) is greater than zero, then the initial peak time is directly used as the peak time.

7. A method for setting transient power frequency overvoltage suppression parameters according to any one of claims 1 to 6, characterized in that: In step (8), adjust the integral parameter The steps include: Compare the system overshoot limit calculated in step (4) The system overshoot calculated in step (7) ,like ,but ;like , then the integral parameter is equal to the initial value of the integral parameter of the phase-locked loop controller entered in step (1).

8. A computer device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of any one of claims 1-7.

9. A computer-readable storage medium having a computer program or instruction stored thereon, characterized in that: When the computer program or instruction is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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