Network-constructed converter control parameter setting method for improving active support capability

Abstract

The application discloses a network-constructing type converter control parameter setting method for improving active support capability, which comprises the following steps: firstly, inputting the known output active power limit of a network-constructing type converter to be solved, inputting the set step disturbance amplitude of the network-constructing type converter to be solved, inputting the initial value 0.1 of a damping coefficient, inputting the maximum value of the damping coefficient, inputting the search number of the damping coefficient, and inputting the inertia time constant; secondly, obtaining an active output response function of the network-constructing type converter according to a closed-loop transfer function formula of the active power output of the network-constructing type converter and the grid point angular frequency; and finally, calculating the damping ratio, the response time and the regulation time of the active power output of the network-constructing type converter, and obtaining a damping coefficient parameter range in combination with the requirement of the national standard GB / T 38983.1-2020 on the active frequency modulation capability of a virtual synchronous machine. The method can be used as a support basis for the design of the control parameters of the network-constructing type converter, improves the active support capability of the network-constructing type converter, and guarantees the safe and stable operation of a power system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of device parameter setting for use with power supply or similar power supply system, and particularly relates to a control parameter setting method for grid-forming converter with improved active support capability. BACKGROUND

[0002] New energy is gradually playing an increasingly important role in the power system. At the same time, the traditional power system dominated by synchronous machines is accelerating to evolve into a new type of power system with power electronics technology as the core. These new energy generation devices are mainly connected to the grid through converters, resulting in a continuous decrease in system inertia and a continuous decrease in anti-interference ability, posing a severe challenge to the construction of a safe and stable new energy power system.

[0003] Most of the new energy in the current power system is connected to the grid through grid-following converters. Unlike traditional synchronous machines with large capacity, high inertia and strong frequency regulation capability, grid-following converters achieve synchronization with the grid through a phase-locked loop (PLL) and rarely have active support functions, with insufficient inertia response and frequency regulation capability. Grid-forming converters simulate the characteristics of synchronous machines by using virtual synchronous generator (VSG) control and can act as equivalent voltage sources after being connected to the grid. Unlike grid-following converters that act as equivalent current sources and track the voltage phase through a phase-locked loop, grid-forming converter control can provide inertia and damping for the power system, active support, and improve the stability of the grid.

[0004] However, the control parameters of grid-forming converters have an important influence on their active support capability, and how to reasonably adjust the parameter range to better exert the active support capability is a problem to be solved. SUMMARY

[0005] In order to solve the problem of lack of grid-forming converter control parameter setting method considering active response time and regulation time limit, the purpose of the present application is to propose a grid-forming converter control parameter setting method with improved active support capability. Under the premise of given inertia time constant, the present application gives the parameter range of the damping coefficient of the grid-forming converter through the limitation of damping ratio, response time and regulation time, shortens the active response time and regulation time of the grid-forming converter while limiting active overshoot and active oscillation, improves the active support capability of the grid-forming converter, and solves the problem of lack of grid-forming converter control parameter setting method considering active response time and regulation time limit.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0007] A network configuration type converter control parameter setting method for improving active support capability, comprising the following steps:

[0008] Step 1: input the known output active power limit K of the network configuration type converter to be solved p , input the set step disturbance amplitude A of the network configuration type converter to be solved, the initial value 0.1 of the damping coefficient D, the maximum value D of the damping coefficient D max , the search number n of the damping coefficient D, and the inertia time constant T J ;

[0009] Step 2: calculate the search step size of the damping coefficient △D=(D max -0.1) / (n-1);

[0010] Step 3: set the storage space of the damping coefficient valid_D as an empty set;

[0011] Step 4: calculate the damping ratio , wherein , represents the angular frequency of the power system where the network configuration type converter is located, and f represents the frequency of the power system where the network configuration type converter is located;

[0012] Step 5: judge whether the damping ratio is greater than or equal to 0.707, if yes, continue to the next step; if not, jump to step 12;

[0013] Step 6: judge whether the damping ratio is greater than or equal to 1, if yes, continue to the next step; if not, jump to step 8;

[0014] Step 7: the step response expression of the output active power of the network configuration type converter is: , jump to step 9;

[0015] In the formula, P s (t) is the output active power of the network configuration type converter changing with time t, , ; , represents the natural oscillation angular frequency; , are two roots of the characteristic equation , and s is the Laplace operator;

[0016] Step 8: the step response expression of the output active power of the network configuration type converter is: ;

[0017] Step 9: calculate the response time t r and the regulation time t s , wherein the response time t r refers to the time when P s (t) reaches 90% of the steady-state value for the first time, and the regulation time ts P refers to P s (t) the time when the last time the output active power of the grid-connected type converter enters the error band of ±5% of the steady-state value;

[0018] Step 10: judge whether t r ≤ 0.5 seconds and t s ≤ 1 second, if yes, continue to the next step; if no, jump to step 12;

[0019] Step 11: add the damping coefficient D to the storage space valid_D of the damping coefficient;

[0020] Step 12: let D=D+△D;

[0021] Step 13: judge whether D>D max , if yes, continue to the next step; if no, jump to step 4;

[0022] Step 14: judge whether the storage space valid_D of the damping coefficient is empty, if yes, continue to the next step; if no, jump to step 16;

[0023] Step 15: output: there is no D value meeting the condition, and the method ends;

[0024] Step 16: output the maximum value and the minimum value of valid_D.

[0025] The method of the present application considers the response time and the regulation time limit of the active power of the grid-connected type converter, and considers the problems of active overshoot and active oscillation caused by insufficient damping, realizes the identification of the parameter range of the damping coefficient under any given inertia time constant, can meet the requirements of the state standard on the response time and the regulation time of the output active power of the grid-connected type converter, and can limit the active overshoot and the active oscillation. For the parameter design of the grid-connected type converter, the present application has a guiding role in improving the active support capability of the grid-connected type converter.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] The method can calculate the parameter range of the damping coefficient according to the known grid-forming converter output active power limit and the set inertia time constant. The method effectively solves the problem of the grid-forming converter control parameter setting method without considering the active response time and the regulation time limit, can suppress the active overshoot and active oscillation while improving the active response and regulation speed of the grid-forming converter, and effectively improves the active support capability of the grid-forming converter. Based on the closed-loop transfer function of the output active power and the grid point angular frequency, under the premise of the given inertia time constant, combined with the requirement of the active frequency modulation capability of the virtual synchronous machine (VSG) in the national standard GB / T 38983.1-2020 of China: the regulation time is not more than 1 second, the response time is not more than 0.5 second, and the influence of the damping coefficient on the active power oscillation and overshoot is considered, the parameter range of the damping coefficient in the grid-forming converter is given through the limitation of the damping ratio, the response time and the regulation time, the active support capability of the grid-forming converter is improved, and it has important significance in guiding the parameter design of the grid-forming converter and guaranteeing the safe and stable operation of the power system. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flow chart of the method.

[0029] Figure 2 is a power system model containing a grid-forming converter.

[0030] Figure 3 is K p =7.52, T J =2~12s, the optional range of the damping coefficient.

[0031] Figure 4 is K p =7.52, T J =5, D=154, the P s (t) curve proposed by the application and the active power curve obtained by simulation.

[0032] Figure 5 is K p =7.52, T J =5, D=437, the P s (t) curve proposed by the application and the active power curve obtained by simulation.

[0033] Figure 6 is K p =7.52, T J =10, D=218, the P s (t) curve proposed by the application and the active power curve obtained by simulation.

[0034] Figure 7 is K p= 7.52, T J = 10, D = 463, the P s (t) curve and the active power curve obtained by simulation.

[0035] Figure 8 is K p = 7.52, T J = 5, the active power curve obtained by simulation when the value of D is changed. DETAILED DESCRIPTION

[0036] The application will be further described in detail below in combination with the drawings and examples.

[0037] As Figure 1 shown, the application is a network configuration type converter control parameter setting method for improving active support capability, which comprises the following steps:

[0038] Step 1: input the known output active power limit K p of the network configuration type converter to be solved, input the set step disturbance amplitude A of the network configuration type converter to be solved, the initial value 0.1 of the damping coefficient D, the maximum value D max of the damping coefficient D, the search number n of the damping coefficient D, and the inertia time constant T J ;

[0039] Step 2: calculate the search step length △D of the damping coefficient, which is equal to (D max -0.1) / (n-1);

[0040] Step 3: set the storage space valid_D of the damping coefficient as an empty set;

[0041] Step 4: calculate the damping ratio , wherein , represents the angular frequency of the power system in which the network configuration type converter is located, and f represents the frequency of the power system in which the network configuration type converter is located;

[0042] Step 5: judge whether the damping ratio is greater than or equal to 0.707, if yes, continue to the next step; if no, jump to step 12;

[0043] Step 6: judge whether the damping ratio is greater than or equal to 1, if yes, continue to the next step; if no, jump to step 8;

[0044] Step 7: the step response expression of the output active power of the network configuration type converter is: , jump to step 9;

[0045] In the formula, P s (t) is the output active power of the network configuration type converter changing with time t, , ; , represents the natural oscillation angular frequency; 、 The characteristic equations are The two roots of , s is the Laplace operator;

[0046] Step 8: The step response expression of the active power output of the grid-connected converter is: ;

[0047] The derivation process of the step response expression of the active power output of the grid-type converter in steps 7 and 8 is as follows: Based on the active power output equation of the grid-type converter , active outer loop control equation of grid-connected converter The relationship equation between the angle and angular frequency of the grid-connected converter ; Linearize and Laplace transform the three equations: 、 、 , eliminate and ,make Obtain the closed-loop transfer function of the grid-connected converter output active power and grid-connected point angular frequency , when the angular frequency of the power system where the grid-type converter is located experiences a step disturbance ,at this time ; When the damping ratio is greater than or equal to 1, the characteristic equation There are two real roots 、 , the active power response of the grid-type converter under step disturbance is obtained by inverse transformation ; When the damping ratio is less than 1, the characteristic equation There is a pair of conjugate complex roots, and the active power response of the grid-type converter under step disturbance is obtained by inverse Latent transformation.

[0048] Where, P s is the active power output of the grid-type converter, U PCC 、 are the voltage amplitude and phase angle of the grid connection point, E, are the voltage amplitude and phase angle of the grid-connected converter, x2 is the reactance from the grid-connected converter to the grid point, It means taking the derivative of the variable with respect to time t, is the per-unit value of the angular frequency of the grid-type converter, P ref The active power reference value output by the grid-connected converter is is the per-unit value of the grid-connected point angular frequency, is the output active power change of the grid-type converter in the frequency domain, The variation of the voltage phase angle of the grid-connected converter and the voltage phase angle of the grid point in the frequency domain, The variation of the grid-connected converter angle frequency in the frequency domain, The variation of the grid point angle frequency in the frequency domain.

[0049] Step 9: Calculate the response time t r And the adjustment time t s , wherein the response time t r refers to the time when P s (t) reaches 90% of the steady-state value for the first time, the adjustment time t s refers to the time when P s (t) enters the steady-state value ±5% error band of the grid-connected converter output active power for the last time;

[0050] Step 10: Determine whether t r ≤ 0.5 seconds and t s ≤ 1 second, if yes, continue to the next step; if no, jump to step 12;

[0051] Step 11: Add the damping coefficient D to the damping coefficient storage space valid_D;

[0052] Step 12: Let D=D+△D;

[0053] Step 13: Determine whether D>D max , if yes, continue to the next step; if no, jump to step 4;

[0054] Step 14: Determine whether the damping coefficient storage space valid_D is empty, if yes, continue to the next step; if no, jump to step 16;

[0055] Step 15: Output: no D value meets the condition, and the method ends;

[0056] Step 16: Output the maximum and minimum values of valid_D. Embodiment

[0057] To verify the correctness of the grid-connected converter control parameter setting method for improving active support capability, a power system model containing a grid-connected converter as shown in Figure 2 is built on a simulation platform, and simulation verification is performed according to the following parameters:

[0058] The grid-connected converter output is 10 MW, and the receiving end power grid output is 5 MW. The disturbance is a 0.2 Hz system frequency drop at 0 s.

[0059] Figure 3 K p = 7.52, T = 0.5 s calculated according to the method of the present application.J =The optional range of the damping coefficient when 2~12s.

[0060] In order to verify the correctness of the control parameter setting method of the grid-type converter for improving the active power support capability of the present invention, the K p =7.52, T J =5, a simulation analysis is performed on the active power response of the grid-connected converter. Figure 4 It's K p =7.52, T J =5, D=154 when the P s (t) curve and the active power curve obtained by simulation. Figure 5 It's K p =7.52, T J =5, D=437 when the P s (t) curve and the active power curve obtained by simulation. Figure 4 It can be seen that when the damping coefficient takes the minimum value, the response time and adjustment time meet the requirements. At this time, the condition that the damping ratio is not less than 0.707 limits the lower limit of D. Figure 5 It can be seen that when the damping coefficient takes the maximum value, both the response time and the adjustment time meet the requirements. In this case, the condition that the response time does not exceed 0.5 seconds limits the upper limit of D. This proves the rationality of the control parameter tuning method of the grid-connected converter for improving the active power support capability of the present invention.

[0061] In order to verify the correctness of the control parameter setting method of the grid-type converter for improving the active power support capability of the present invention, the K p =7.52, T J =10, the active power response of the grid-connected converter is simulated and analyzed. Figure 6 It's K p =7.52, T J =10, D=218 The P s (t) curve and the active power curve obtained by simulation. Figure 7 It's K p =7.52, T J =10, D=463 when the P s (t) curve and the active power curve obtained by simulation. Figure 6 It can be seen that when the damping coefficient takes the minimum value, the response time and adjustment time meet the requirements. At this time, the condition that the damping ratio is not less than 0.707 limits the lower limit of D. Figure 7It can be seen that when the damping coefficient takes the maximum value, the response time and the regulation time meet the requirements, at this time, the upper limit of D is limited by the condition that the response time is not more than 0.5 seconds. The rationality of the control parameter setting method of the grid-connected type converter for improving the active power support capability is proved.

[0062] Figure 8 K p =7.52, T J =5, the active power curve obtained by changing the value of D is simulated. Figure 3 It can be seen that when K p =7.52, T J =5, the range of D is 154~437. In order to verify the rationality of the range, the simulation verification is carried out for the cases of D=100 / 300 / 500. It can be seen that when D=100, the active power output by the grid-connected type converter overshoots, which reduces the active power support capability of the grid-connected type converter. When D=500, the active response speed is too slow, and the active power output by the grid-connected type converter has not reached the balance 2s after the disturbance occurs, which reduces the active power support capability of the grid-connected type converter. When D=300, the active power output by the grid-connected type converter has a small overshoot that can be accepted, and can meet the requirements of the national standard that the response time is not more than 0.5 seconds and the regulation time is not more than 1 second.

[0063] By analyzing Figure 4 and Figure 5 , Figure 6 and Figure 7 , it is proved that the P s (t) proposed in the application can better fit the actual simulated active power curve. Figure 8 It is proved that the control parameter setting method of the grid-connected type converter for improving the active power support capability proposed in the application can give the parameter range of the damping coefficient of the grid-connected type converter that meets the requirements of the active power overshoot and oscillation, the regulation time and the response time of the grid-connected type converter under the conditions of the given output limit and the inertia time constant, and can be used as the support basis for the control parameter design of the grid-connected type converter, and can improve the active power support capability of the grid-connected type converter.

Claims

1. A method for setting control parameters of a grid-connected converter to improve active power support capability, characterized by: The following steps are involved: Step 1: Input the known output active power limit K of the grid-connected converter to be determined p , input the step disturbance amplitude A, initial value of damping coefficient D 0.1, maximum value of damping coefficient D D of the grid-type converter to be set max , the number of searches n for the damping coefficient D, the inertia time constant T J ; Step 2: Calculate the search step size of the damping coefficient △D=(D max -0.1) / (n-1); Step 3: Set the storage space valid_D of the damping coefficient to an empty set; Step 4: Calculate the damping ratio ,in , represents the angular frequency of the power system where the grid-type converter is located, and f represents the frequency of the power system where the grid-type converter is located; Step 5: Determine whether the damping ratio is greater than or equal to 0.

707. If so, proceed to the next step; if not, jump to step 12; Step 6: Determine whether the damping ratio is greater than or equal to 1. If so, proceed to the next step; if not, jump to step 8; Step 7: The step response expression of the grid-connected converter output active power is: , jump to step 9; Where, P s (t) is the active power output of the grid-connected converter that changes with time t, , ; , represents the natural oscillation angular frequency; 、 The characteristic equations are The two roots of , s is the Laplace operator; Step 8: The step response expression of the active power output of the grid-connected converter is: ; Step 9: Calculate the response time t r and adjustment time t s , where the response time t r Refers to P s (t) The time when the steady-state value reaches 90% for the first time, adjustment time t s Refers to P s (t) The time when the grid-connected converter output active power last entered the ±5% error band of the steady-state value; Step 10: Determine whether t is satisfied r ≤ 0.5 seconds and t s ≤ 1 second, if yes, proceed to the next step; if no, skip to step 12; Step 11: Add the damping coefficient D to the damping coefficient storage space valid_D; Step 12: Let D = D + △ D; Step 13: Determine whether D>D max If yes, continue to the next step; if no, jump to step 4; Step 14: Determine whether the storage space valid_D of the damping coefficient is an empty set. If so, proceed to the next step; if not, jump to step 16; Step 15: Output: There is no D value that meets the conditions, and the method ends; Step 16: Output the maximum and minimum values ​​of valid_D.

2. The method for setting control parameters of a grid-connected converter for improving active power support capability according to claim 1, wherein: Active power output equation based on grid-connected converter , active outer loop control equation of grid-connected converter The relationship equation between the angle and angular frequency of the grid-connected converter ; Linearize and Laplace transform the three equations: 、 、 , eliminate and ,make Obtain the closed-loop transfer function of the grid-connected converter output active power and grid-connected point angular frequency , when the angular frequency of the power system where the grid-type converter is located experiences a step disturbance ,at this time ; When the damping ratio is greater than or equal to 1, the characteristic equation There are two real roots 、 , the active power response of the grid-type converter under step disturbance is obtained by inverse transformation ; When the damping ratio is less than 1, the characteristic equation There is a pair of conjugate complex roots, and the active power response of the grid-type converter under step disturbance is obtained by inverse Latent transformation. ; Where, P s is the active power output of the grid-type converter, U PCC 、 are the voltage amplitude and phase angle of the grid connection point, E, are the voltage amplitude and phase angle of the grid-connected converter, x2 is the reactance from the grid-connected converter to the grid point, It means taking the derivative of the variable with respect to time t, is the per-unit value of the angular frequency of the grid-type converter, P ref The active power reference value output by the grid-connected converter is is the per-unit value of the grid-connected point angular frequency, is the output active power change of the grid-type converter in the frequency domain, is the change in the voltage phase angle of the grid-connected converter and the voltage phase angle difference at the grid connection point in the frequency domain, is the per-unit change of the angular frequency of the grid-connected converter in the frequency domain, is the per-unit change of the angular frequency at the grid connection point.

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