Network construction type converter control parameter setting method for improving active supporting capability

Abstract

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

Description

Technical Field

[0001] The present invention belongs to the technical field of parameter setting of equipment used with a power supply or a similar power supply system, and in particular relates to a control parameter setting method for a grid-connected converter for improving active power support capability. Background Art

[0002] Renewable energy sources are playing an increasingly important role in power systems. At the same time, the traditional power system, long dominated by synchronous generators, is rapidly evolving into a new power system centered on power electronics. These renewable energy generation devices are primarily connected to the grid via converters, resulting in a continuous decrease in system inertia and interference resistance, posing a severe challenge to building a safe and stable renewable energy power system.

[0003] Currently, most renewable energy sources in power systems are connected to the grid via grid-following converters. Unlike traditional synchronous motors with large capacity, high inertia, and strong frequency regulation capabilities, grid-following converters achieve synchronization with the grid through a phase-locked loop (PLL). They rarely have active support functions and lack inertia response and frequency regulation capabilities. Grid-forming converters use virtual synchronous generator (VSG) control to emulate the characteristics of synchronous motors, acting as an equivalent voltage source when connected to the grid. Unlike grid-following converters, which act as equivalent current sources and track voltage phases through a phase-locked loop (PLL), grid-forming converter control can provide inertia and damping to the power system, providing active power support and improving grid stability.

[0004] However, the control parameters of the grid-type converter have an important impact on its active power support capability. How to reasonably adjust the parameter range to enable it to better exert its active power support capability is a problem to be solved. Summary of the Invention

[0005] In order to solve the problem of the current lack of a control parameter setting method for a grid-type converter that takes into account the active power response time and adjustment time limitations, the purpose of the present invention is to propose a control parameter setting method for a grid-type converter that improves the active power support capability. Under the premise of a given inertia time constant, the present invention provides a parameter range of the damping coefficient of the grid-type converter by limiting the damping ratio, response time and adjustment time. This shortens the active power response time and adjustment time of the grid-type converter while limiting active power overshoot and active power oscillation, thereby improving the active power support capability of the grid-type converter and solving the problem of the current lack of a control parameter setting method for a grid-type converter that takes into account the active power response time and adjustment time limitations.

[0006] In order to achieve the above object, the technical solution adopted in the present invention is: A method for adjusting control parameters of a grid-connected converter for improving active power support capability comprises the following steps: 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 ts ≤ 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.

[0007] The method of the present invention considers the response and regulation time limitations of the active power of a grid-type converter, while also accounting for active power overshoot and active power oscillation caused by insufficient damping. It identifies the parameter range of the damping coefficient for any given inertia time constant, meeting national standards for the response and regulation time of the grid-type converter's output active power while limiting active power overshoot and active power oscillation. This provides guidance for the parameter design of grid-type converters and for improving their active power support capabilities.

[0008] Compared with the prior art, the present invention has the following advantages: The method of the present invention can calculate the parameter range of the damping coefficient based on the known active power output limit of the grid-type converter and the set inertia time constant. This method effectively solves the problem of the lack of grid-type converter control parameter tuning methods that consider active power response time and adjustment time constraints. It can improve the active power response and adjustment speed of the grid-type converter while suppressing active power overshoot and active power oscillation, effectively enhancing the active power support capability of the grid-type converter. The present invention is based on the closed-loop transfer function of the output active power and the grid-connected point angular frequency. Under the premise of a given inertia time constant, it combines the requirements of my country's national standard GB / T 38983.1-2020 on the active frequency regulation capability of the virtual synchronous machine (VSG): the adjustment time does not exceed 1 second, and the response time does not exceed 0.5 seconds. At the same time, considering the influence of the damping coefficient on the active power oscillation and overshoot, the parameter range of the damping coefficient in the grid-type converter is given by limiting the damping ratio, response time and adjustment time, thereby improving the active support capability of the grid-type converter. It is of great significance in guiding the parameter design of the grid-type converter and ensuring the safe and stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a flow chart of the method of the present invention.

[0010] Figure 2 It is a power system model including grid-type converter.

[0011] Figure 3 It's K p =7.52, T J =The optional range of the damping coefficient when 2~12s.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] Figure 8 It's K p =7.52, T J =5, the active power curve obtained by simulation when the value of D is changed. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0018] like Figure 1 As shown, the present invention provides a method for adjusting control parameters of a grid-connected converter for improving active power support capability, comprising the following steps: 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 TJ ; 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: ; 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 power 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 of the grid-connected 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.

[0019] 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 is first reached 90%, the 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. Example

[0020] In order to verify the correctness of the control parameter setting method of the grid-connected converter proposed in this invention to improve the active power support capability, a simulation platform is built as follows: Figure 2 The power system model with grid-connected converter shown in the figure was simulated and verified according to the following parameters: The grid-connected converter has an output of 10 MW and the receiving grid has an output of 5 MW. The system frequency drops by 0.2 Hz at 0 seconds of disturbance.

[0021] Figure 3 K is calculated according to the method of the present invention p =7.52, T J =The optional range of the damping coefficient when 2~12s.

[0022] 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.

[0023] 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, TJ =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 7 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.

[0024] Figure 8 K p =7.52, T J =5, the active power curve obtained by simulation when the value of D is changed. Figure 3 It can be seen that the K obtained by the method of the present invention p =7.52, T J =5, the range of D is 154–437. To verify the rationality of this range, simulations were performed for D = 100 / 300 / 500. It can be seen that when D = 100, the active power output of the grid-type converter overshoots, reducing the active power support capability of the grid-type converter. When D = 500, the active power response speed is too slow, and the active power output of the grid-type converter has not reached equilibrium 2 seconds after the disturbance occurs, reducing the active power support capability of the grid-type converter. However, when D = 300, the active power output of the grid-type converter has an acceptable small overshoot and meets the national standard requirements of a response time of no more than 0.5 seconds and an adjustment time of no more than 1 second.

[0025] Through analysis Figure 4 and Figure 5 , Figure 6 and Figure 7 , proves that the P s (t) It can better fit the actual simulated active power curve. Figure 8 It is proved that the control parameter adjustment method of the grid-type converter proposed in the present invention for improving the active power supporting capability can, under the conditions of given output limit and inertia time constant, provide a parameter range of the damping coefficient of the grid-type converter that meets the requirements of active power overshoot and oscillation, adjustment time and response time of the grid-type converter. It can serve as a supporting basis for the design of control parameters of the grid-type converter and improve the active power supporting capability of the grid-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 is first reached 90%, the 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 power 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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