Power grid simulator control method based on generalized second-order differential simulation impedance characteristics

Abstract

The invention discloses a power grid simulator control method based on generalized second-order differential simulation impedance characteristics, belongs to the technical field of power grid simulator control, and is suitable for a line impedance characteristic simulation system. The control method comprises the steps of firstly calculating active power and reactive power of a power grid simulator, then calculating through a VSG algorithm to obtain an output voltage instruction, and finally adding a virtual complex impedance based on generalized second-order differential on the basis of an original voltage and current double-closed-loop feedback control system to realize a simulation function of system line impedance. The generalized second-order differential function keeps the phase lead compensation differential effect on a specific frequency range, and eliminates the inherent high-frequency noise amplification effect of a traditional differential function. According to the control method, the dynamic performance of the system can be effectively improved, the output signal ripple is small, and the control speed is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of power grid simulator control, and in particular relates to a power grid simulator control method based on generalized second-order differential simulated impedance characteristics. Background Art

[0002] With the increase in the penetration rate of distributed power generation systems, the demand for power quality and grid adaptability test platforms for new energy power generation systems such as photovoltaic and wind power is increasing. They need to be connected to the grid through long-distance transmission and distribution lines. At this time, the system line impedance will not only change the impedance characteristics of the grid, but also affect the working performance of the grid-connected converter. Therefore, in order to more realistically simulate the actual grid situation and detect and simulate the line impedance of a single-machine system, it is very meaningful for the grid simulator to use the line impedance simulation function to conduct simulation experiments.

[0003] At present, there are two ideas for impedance simulation in existing research: introducing virtual impedance in control and adjusting virtual impedance parameters to simulate impedance. Another idea is to improve the main circuit topology and introduce active converters into the circuit to simulate impedance, such as the Chinese invention patent application publication "Inverter system line impedance simulation method based on starting impedance angle" (publication number CN 109787280A), "Weak power grid simulator and line impedance simulation method of series active H-bridge converter" (publication number CN117239825A) and "Power grid simulator control method with transmission line impedance wide frequency domain simulation function" (publication number CN 118068125A), among which:

[0004] The "Inverter System Line Impedance Simulation Method Based on Starting Impedance Angle" published on May 21, 2019 obtains the starting impedance angle sine and cosine values ​​corresponding to the required simulated line impedance from the starting impedance angle equation, and then uses the line impedance simulation equation to achieve the simulation function of the inverter system line impedance. It only improves the control method of the existing inverter, without adding additional power electronic equipment, reducing costs, but the integral controller involved in the patent control loop brings a phase lag problem;

[0005] The "Weak Grid Simulator and Line Impedance Simulation Method of Series Active H-Bridge Converter" published on December 5, 2023 achieves the purpose of accurately simulating line impedance by controlling the active H-bridge converter connected in series in the main topology. However, the impedance command of this method is obtained based on the harmonic current extraction control, resulting in many harmonic components;

[0006] The "Grid Simulator Control Method with Wide-Frequency Domain Simulation Function of Transmission Line Impedance" published on May 24, 2024 constructs a transmission line with complex parameters into a distributed parameter circuit model through a transmission line model. The simulated line impedance has high accuracy, but the multi-order linear approximation method used in the transmission line model is relatively complex, and the control performance is greatly affected by the parameters.

[0007] In summary, the prior art has deficiencies, specifically:

[0008] 1. The integral controller involved in the control loop brings about phase lag problem;

[0009] 2. Most of the existing analog inductive impedance characteristics use traditional differential links, which will cause high-frequency harmonic interference;

[0010] 3. Among the control methods of power grid simulators for simulating line impedance characteristics, there is little research on dynamic stability performance and improvement measures. Summary of the invention

[0011] The technical problem to be solved by the present invention is to overcome the limitations of the above-mentioned various technical solutions, to solve the phase lag problem corresponding to the integral link and to improve the harmonic compensation performance, the present invention proposes a power grid simulator control method based on generalized second-order differential simulated impedance characteristics.

[0012] The object of the present invention is achieved in this way. The present invention provides a power grid simulator control method based on generalized second-order differential analog impedance characteristics, the power grid simulator includes three identical single-phase full-bridge inverter submodules, the single-phase full-bridge inverter submodule includes a DC source, a DC side filter capacitor, a single-phase full-bridge inverter, a filter inductor, a filter capacitor and a load, wherein the DC side filter capacitor is connected in parallel between the positive and negative busbars of the DC source, the input end of the single-phase full-bridge inverter is connected in parallel with the DC side filter capacitor, the output end is connected in parallel with the filter capacitor, and the load is connected in parallel to the other side of the filter capacitor, The filter inductor is connected to the line connecting the output end of the single-phase full-bridge inverter and the positive electrode of the filter capacitor; the three single-phase full-bridge inverter submodules are independently controlled, and the output phases of the two adjacent phases are 120° apart; the negative electrodes of the filter capacitors of the three single-phase full-bridge inverter submodules are connected together, and the node is recorded as point N0; the positive electrodes of the filter capacitors of the three single-phase full-bridge inverter submodules serve as the three-phase output of the power grid simulator, which respectively simulates the A, B, and C phases of the power grid simulator, and the input ends of the three single-phase full-bridge inverters are connected in parallel to form the input of the power grid simulator;

[0013] The steps of the control method are as follows:

[0014] Step 1: The three filter inductors, three filter capacitors, and three loads in the three single-phase full-bridge inverter submodules are regarded as the three-phase filter inductors, three-phase filter capacitors, and three-phase loads of the power grid simulator respectively; the current flowing through the three-phase filter inductors is sampled and recorded as the bridge arm side inductor current i La ,i Lb ,i Lc , sample the voltage at the three-phase filter capacitor and record it as the filter capacitor voltage u ca ,u cb u cc , sample the current at the three-phase load and record it as load current i oa ,i ob ,i oc ; For the filter capacitor voltage u ca ,u cb ,u cc and load current i oa ,i ob ,i oc Perform coordinate transformation to obtain the dq component of the filter capacitor voltage U cd , U cq and the load current dq component I od , I oq ;

[0015] Step 2: The dq component U of the filter capacitor voltage obtained in step 1 cd , U cq and the load current dq component I od , I oq , the active power P and reactive power Q of the power grid simulator are calculated, and their expressions are: P = 1.5 (U cq I oq +U cd I od ), Q = 1.5 (U cd I oq -U cq I od );

[0016] Step 3, according to the active power P obtained in step 2, the given active power command P0 and the rated angular frequency ω0 at the given active power command P0, the power grid simulator output angular frequency ω is obtained through the power angle control equation, and the power grid simulator control output phase θ is obtained by integrating ω;

[0017] Step 4, according to the reactive power Q obtained in step 2, the given reactive power command Q0, and the rated voltage U0 when the given reactive power command Q0 is used, the output voltage amplitude command U of the power grid simulator is obtained. c_ref , U c_ref =U0+n(Q0-Q), n is the reactive power-voltage droop coefficient;

[0018] Step 5: Control the output phase θ of the power grid simulator obtained in step 3 and the output voltage amplitude instruction U of the power grid simulator obtained in step 4. c_ref , the output voltage command u of the three single-phase full-bridge inverter submodules is obtained through the voltage command synthesis equation ca_ref ,u cb_ref ,i cc_ref ;

[0019] Step 6: Introduce the generalized second-order differential transfer function G i (s), i=a,b,c;where s is the Laplace operator, K i is the generalized second-order differential transfer function G i (s) proportionality coefficient, Q i is the generalized second-order differential transfer function G i The quality factor of (s), ω i is the generalized second-order differential transfer function G i (s) angular frequency; introduce the generalized second-order differential transfer function G i (s) is the virtual complex impedance Z vi ;

[0020] Step 7: Based on the virtual complex impedance Z introduced in step 6 vi , the output voltage command u obtained in step 5 ca_ref ,u cb_ref ,u cc_ref 、The filter capacitor voltage u obtained in step 1 ca ,u cb ,u cc and load current i oa ,i ob ,i oc , the output current command signal i is obtained through the voltage control equation a_ref ,i b_ref ,i c_ref ; According to the output current command signal i a_ref ,i b_ref ,i c_ref , the bridge arm side inductor current i obtained in step 1 La ,i Lb ,i Lc and load current i oa ,i ob ,i oc , the output voltage command u obtained in step 5 ca_ref ,i cb_ref ,u cc_ref , the control signal is obtained through the current control equation According to Generate PWM control signals for three single-phase full-bridge inverter switch tubes.

[0021] Preferably, the power angle control equation in step 3 is:

[0022]

[0023] Wherein, m is the power angle control droop coefficient, and J is the simulated virtual moment of inertia.

[0024] Preferably, the voltage command synthesis equation in step 5 is:

[0025] u ca_ref =U c_ref sin(θ)

[0026] u cb_ref =U c_ref sin(θ-120°).

[0027] u cc_ref =U c_ref sin(θ+120°)

[0028] Preferably, the voltage control equation and the current control equation in step 7 are respectively:

[0029]

[0030] Among them, K ap1 , K bp1 , K cp1 is the proportional coefficient of the first PI controller corresponding to the three single-phase full-bridge inverters, K ai1 , K bi1 , K ci1 is the integral coefficient of the first PI controller corresponding to the three single-phase full-bridge inverters, K ap2 , K bp2 , K cp2 is the proportional coefficient of the second PI controller corresponding to the three single-phase full-bridge inverters, K ai2 , K bi2 , K ci2 is the integral coefficient of the second PI controller corresponding to the three single-phase full-bridge inverters.

[0031] Preferably, the virtual complex impedance Z in step 6 is vi is a virtual complex impedance containing a purely inductive component, and its expression is:

[0032]

[0033] Among them, L va , L vb , L vcis the virtual inductance corresponding to the three single-phase full-bridge inverters.

[0034] Preferably, the virtual complex impedance Z in step 6 is vi is a virtual complex impedance containing resistive and inductive components, and its expression is:

[0035]

[0036] Among them, L va , L vb , L vc is the virtual inductance corresponding to the three single-phase full-bridge inverters, R va , R vb , R vc is the virtual resistance corresponding to the three single-phase full-bridge inverters.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The generalized second-order differential function in the present invention has a phase lead compensation effect in a specific frequency range, which can make up for the phase lag caused by the integral link, thereby increasing the phase margin and improving the dynamic stability performance of the system;

[0039] 2. Compared with the common differential link, the generalized second-order differential function in the present invention not only retains the phase lead compensation differential effect in a specific frequency range, but also eliminates the high-frequency noise amplification effect inherent in the traditional differential function, thereby improving the reliability of the system;

[0040] 3. The power grid simulator control method based on generalized second-order differential simulated line impedance adopted by the present invention has good output dynamic performance and fast control speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a topological diagram of the present invention.

[0042] Figure 2 It is a control block diagram of the present invention.

[0043] Figure 3 It is a simulation waveform diagram in an implementation case of the present invention.

[0044] Figure 4 It is a Fourier analysis histogram of the simulation waveform in the implementation case of the present invention.

[0045] Figure 5 It is a simulation waveform diagram in an implementation case of the present invention.

[0046] Figure 6 It is a Fourier analysis histogram of the simulation waveform in the implementation case of the present invention.

[0047] Figure 7It is a simulation waveform diagram in an implementation case of the present invention.

[0048] Figure 8 It is a Fourier analysis histogram of the simulation waveform in the implementation case of the present invention.

[0049] Fig. 9 It is a simulation waveform diagram in an implementation case of the present invention.

[0050] Fig.10 It is a Fourier analysis histogram of the simulation waveform in the implementation case of the present invention. DETAILED DESCRIPTION

[0051] The preferred embodiments of the present invention are described in further detail below in conjunction with the accompanying drawings.

[0052] Figure 1 is a topological diagram of the present invention, Figure 2 It is the control block diagram of the present invention. Figure 1 and Figure 2 It can be seen that the power grid simulator includes three identical single-phase full-bridge inverter sub-modules, and the single-phase full-bridge inverter sub-module includes a DC source, a DC side filter capacitor, a single-phase full-bridge inverter, a filter inductor, a filter capacitor and a load, wherein the DC side filter capacitor is connected in parallel between the positive and negative busbars of the DC source, the input end of the single-phase full-bridge inverter is connected in parallel with the DC side filter capacitor, the output end is connected in parallel with the filter capacitor, the load is connected in parallel to the other side of the filter capacitor, and the filter inductor is connected to the line connecting the output end of the single-phase full-bridge inverter and the positive electrode of the filter capacitor. The three single-phase full-bridge inverter submodules are independently controlled, and the output phase difference between two adjacent phases is 120°; the negative electrodes of the filter capacitors of the three single-phase full-bridge inverter submodules are connected together, and the node is recorded as point N0; the positive electrodes of the filter capacitors of the three single-phase full-bridge inverter submodules serve as the three-phase output of the power grid simulator, which simulates the A, B, and C phases of the power grid simulator respectively, and the input ends of the three single-phase full-bridge inverters are connected in parallel to form the input of the power grid simulator.

[0053] exist Figure 1 and Figure 2 Up,U dc is the DC side voltage at the DC source, C is the capacitance of the DC side filter capacitor, L1 is the inductance of the filter inductor, C1 is the capacitance of the filter capacitor, R L is the load, and Z1, Z2, Z3, and Z4 are switch tubes of a single-phase full-bridge inverter. Specifically, the parameters in this embodiment are as follows: U dc is 600V, the output AC phase voltage effective value is 220V / 50Hz, the rated capacity is 30kW, L1=0.1mH, C1=60μF, the sampling frequency is f s is 30kHz, so the sampling period T s =33.3μs.

[0054] Depend on Figure 2 It can be seen that the steps of the power grid simulator control method based on the generalized second-order differential simulated impedance characteristics of the present invention are as follows:

[0055] Step 1: The three filter inductors, three filter capacitors, and three loads in the three single-phase full-bridge inverter submodules are regarded as the three-phase filter inductors, three-phase filter capacitors, and three-phase loads of the power grid simulator respectively; the current flowing through the three-phase filter inductors is sampled and recorded as the bridge arm side inductor current i La ,i Lb ,i Lc , sample the voltage at the three-phase filter capacitor and record it as the filter capacitor voltage u ca ,u cb ,u cc , sample the current at the three-phase load and record it as load current i oa ,i ob ,i oc ; For the filter capacitor voltage u ca ,u cb ,u cc and load current i oa ,i ob ,i oc Perform coordinate transformation to obtain the dq component of the filter capacitor voltage U cd , U cq and the load current dq component I od , I oq ;

[0056] Step 2: The dq component U of the filter capacitor voltage obtained in step 1 cd , U cq and the load current dq component I od , I oq , the active power P and reactive power Q of the power grid simulator are calculated, and their expressions are: P = 1.5 (U cq I oq +U cd I od ), Q = 1.5 (U cd I oq -U cq I od ).

[0057] Step 3, according to the active power P obtained in step 2, the given active power command P0 and the rated angular frequency ω0 at the given active power command P0, the power grid simulator output angular frequency ω is obtained through the power angle control equation, and the power grid simulator control output phase θ is obtained by integrating ω.

[0058] In this embodiment, the power angle control equation is:

[0059]

[0060] Wherein, m is the power angle control droop coefficient, and J is the simulated virtual moment of inertia.

[0061] The active power droop curve relationship in the power angle control equation includes three coefficients. The power angle control droop coefficient m represents the slope of the droop curve. The value is based on the principle that when the active power changes by 100%, the frequency changes within 0.5Hz. The given active power command P0 and the corresponding rated angular frequency ω0 represent the position relationship of the droop curve, which mainly considers the output frequency size of the new energy grid-connected inverter when the output active power is P0. In this embodiment, J=0.06kg·m 2 In order to ensure that the energy does not flow to the DC side during control operation, the active power instruction value is given as P0=30kW, and the corresponding rated angular frequency value is ω0=314.1593rad / s.

[0062] Step 4, according to the reactive power Q obtained in step 2, the given reactive power command Q0, and the rated voltage U0 when the given reactive power command Q0 is used, the output voltage amplitude command U of the power grid simulator is obtained. c_ref , U c_ref =U0+n(Q0-Q), where n is the reactive power-voltage droop coefficient.

[0063] The reactive power-voltage droop coefficient n is taken as follows: when the reactive power changes by 100%, the voltage amplitude changes within 2%; the given reactive power command Q0 and the corresponding rated output capacitor voltage U0 represent the positional relationship of the droop curve, which mainly considers the output voltage size of the new energy grid-connected inverter when its output reactive power is Q0.

[0064] In this embodiment, Q0=0, U0=220V.

[0065] Step 5: Control the output phase θ of the power grid simulator obtained in step 3 and the output voltage amplitude instruction U of the power grid simulator obtained in step 4. c_ref , the output voltage command u of the three single-phase full-bridge inverter submodules is obtained through the voltage command synthesis equation ca_ref ,u cb_ref ,u cc_ref .

[0066] In this embodiment, the voltage command synthesis equation is:

[0067] u ca_ref =U c_ref sin(θ)

[0068] u cb_ref =U c_refsin(θ-120°).

[0069] u cc_ref =U c_ref sin(θ+120°)

[0070] Step 6: Introduce the generalized second-order differential transfer function G i (s), G i (s) = K i s 2 / (s 2 +2Q i ω i s+ω i 2 ), i = a, b, c; where s is the Laplace operator, K i is the generalized second-order differential transfer function G i (s) proportionality coefficient, Q i is the generalized second-order differential transfer function G i The quality factor of (s), ω i is the generalized second-order differential transfer function G i (s) angular frequency; introduce the generalized second-order differential transfer function G i (s) is the virtual complex impedance Z vi .

[0071] In this embodiment, Q i =0.32(i=a, b, c), K i =1(i=a,b,c).

[0072] Step 7: Based on the virtual complex impedance Z introduced in step 6 vi , the output voltage command u obtained in step 5 ca_ref ,u cb_ref ,u cc_ref 、The filter capacitor voltage u obtained in step 1 ca ,u cb ,u cc and load current i oa ,i ob ,i oc , the output current command signal i is obtained through the voltage control equation a_ref ,i b_ref ,i c_ref ; According to the output current command signal i a_ref ,i b_ref ,i c_ref , the bridge arm side inductor current i obtained in step 1 La ,i Lb ,i Lc and load current i oa ,i ob ,ioc , the output voltage command u obtained in step 5 ca_ref ,u cb_ref ,u cc_ref , the control signal is obtained through the current control equation According to Generate PWM control signals for three single-phase full-bridge inverter switch tubes.

[0073] In this embodiment, the voltage control equation and the current control equation are respectively:

[0074]

[0075] Among them, K cp1 , K bp1 , K cp1 is the proportional coefficient of the first PI controller corresponding to the three single-phase full-bridge inverters, K ai1 , K bi1 , K ci1 is the integral coefficient of the first PI controller corresponding to the three single-phase full-bridge inverters, K cp2 , K bp2 , K cp2 is the proportional coefficient of the second PI controller corresponding to the three single-phase full-bridge inverters, K ai2 , K bi2 , K ci2 is the integral coefficient of the second PI controller corresponding to the three single-phase full-bridge inverters.

[0076] In this embodiment, K ap1 , K bp1 , K cp1 Both are 0.5, K ai1 , K bi1 , K ci1 Both are 100, L ap2 , L bp2 , K cp2 Both are 0.05, K ai2 , K bi2 , K ci2 Both are 0.

[0077] In this embodiment, the virtual complex impedance Z in step 6 vi is a virtual complex impedance containing a purely inductive component, and its expression is:

[0078]

[0079] Among them, L va , L vb , L vc is the virtual inductance corresponding to the three single-phase full-bridge inverters.

[0080] In this embodiment, L va =1mH, the calculated analog voltage theoretical value u va =i oa Z va =0.1946;

[0081] In this embodiment, the virtual complex impedance Z in step 6 vi is a virtual complex impedance containing resistive and inductive components, and its expression is:

[0082]

[0083] Among them, L va , L vb , L vc is the virtual inductance corresponding to the three single-phase full-bridge inverters, R va , R vb , R vc is the virtual resistance corresponding to the three single-phase full-bridge inverters.

[0084] In this embodiment, R vb =0.5Ω, L vb =1mH, the calculated analog voltage theoretical value is u vb =i ob Z vb =0.3576.

[0085] In order to demonstrate the technical effect of the present invention, the invention was simulated.

[0086] Figure 3 , Figure 5 The full-bridge inverter uses a generalized second-order differentiator to simulate the output voltage waveform corresponding to the pure inductive and resistive inductive components. Figure 3 It can be seen that the inductive simulation voltage leads the load voltage by 1 / 4 cycle, and the response time is within 0.02s. Figure 4 , Figure 6 Yes Figure 3 , Figure 5 The Fourier analysis bar graph of the simulated voltage shows that the components of the pure inductive and resistive inductive simulated voltages at power frequency are 0.1935 and 0.3547 respectively. Compared with the theoretical values, it can be proved that this control method can achieve high-precision simulation at specific sub-frequency; at the same time, the THD is 0.61% and 1.13% respectively, proving that the generalized second-order differentiator can filter out high-order harmonics.

[0087] In order to verify the advantages of the control method based on generalized second-order differential, three single-phase inverters are simulated based on pure differential control method to simulate the resistive and inductive components. The simulation waveforms based on the generalized second-order differentiator to simulate the impedance characteristics are compared with the simulation waveforms based on the pure differential control unit, and the topology and control system parameters are consistent. Figure 7 , Fig. 9 The waveforms of pure inductive and resistive inductive are given based on pure differential control unit respectively; Figure 8 , Fig.10 Yes Figure 7 , Fig. 9 The Fourier analysis bar graph of the simulated voltage shows that the THD is 40.83% and 23.48% respectively. Compared with the above conclusions, it can be seen that the generalized second-order differentiator eliminates the high-frequency noise amplification effect inherent in the traditional differential function and effectively improves the dynamic performance of the system.

Claims

1. A power grid simulator control method based on generalized second-order differential simulated impedance characteristics, characterized in that: The power grid simulator includes three identical single-phase full-bridge inverter submodules, and the single-phase full-bridge inverter submodule includes a DC source, a DC side filter capacitor, a single-phase full-bridge inverter, a filter inductor, a filter capacitor and a load, wherein the DC side filter capacitor is connected in parallel between the positive and negative busbars of the DC source, the input end of the single-phase full-bridge inverter is connected in parallel with the DC side filter capacitor, the output end is connected in parallel with the filter capacitor, the load is connected in parallel to the other side of the filter capacitor, and the filter inductor is connected to the connection line between the output end of the single-phase full-bridge inverter and the positive electrode of the filter capacitor; the three single-phase full-bridge inverter submodules are independently controlled, and the output phases of the adjacent two phases differ by 120°; the negative electrodes of the filter capacitors of the three single-phase full-bridge inverter submodules are connected together, and the node is recorded as point N0; the positive electrodes of the filter capacitors of the three single-phase full-bridge inverter submodules are used as the three-phase output of the power grid simulator, and the outputs simulate the A, B, and C phases of the power grid simulator respectively, and the input ends of the three single-phase full-bridge inverters are connected in parallel to form the input of the power grid simulator; The steps of the control method are as follows: Step 1: The three filter inductors, three filter capacitors, and three loads in the three single-phase full-bridge inverter submodules are regarded as the three-phase filter inductors, three-phase filter capacitors, and three-phase loads of the power grid simulator respectively; the current flowing through the three-phase filter inductors is sampled and recorded as the bridge arm side inductor current i La ,i Lb ,i Lc , sample the voltage at the three-phase filter capacitor and record it as the filter capacitor voltage u ca ,u cb ,u cc , sample the current at the three-phase load and record it as load current i oa ,i ob ,i oc ; For the filter capacitor voltage u ca ,u cb ,u cc and load current i oa ,i ob ,i oc Perform coordinate transformation to obtain the dq component of the filter capacitor voltage U cd , U cq and the load current dq component I od , I oq ; Step 2: The dq component U of the filter capacitor voltage obtained in step 1 cd , U cq and the load current dq component I od , I oq , the active power P and reactive power Q of the power grid simulator are calculated, and their expressions are: P = 1.5 (U cq I oq +U cd I od ), Q = 1.5 (U cd I oq -U cq I od ); Step 3, according to the active power P obtained in step 2, the given active power command P0 and the rated angular frequency ω0 at the given active power command P0, the power grid simulator output angular frequency ω is obtained through the power angle control equation, and the power grid simulator control output phase θ is obtained by integrating ω; Step 4, according to the reactive power Q obtained in step 2, the given reactive power command Q0, and the rated voltage U0 when the given reactive power command Q0 is used, the output voltage amplitude command U of the power grid simulator is obtained. c_ref , U c_ref =U0+n(Q0-Q), n is the reactive power-voltage droop coefficient; Step 5: Control the output phase θ of the power grid simulator obtained in step 3 and the output voltage amplitude instruction U of the power grid simulator obtained in step 4. c_ref , the output voltage command u of the three single-phase full-bridge inverter submodules is obtained through the voltage command synthesis equation ca_ref ,u cb_ref ,u cc_ref ; Step 6: Introduce the generalized second-order differential transfer function G i (s), i=a,b,c;where s is the Laplace operator, K i is the generalized second-order differential transfer function G i (s) proportionality coefficient, Q i is the generalized second-order differential transfer function G i The quality factor of (s), ω i is the generalized second-order differential transfer function G i (s) angular frequency; introduce the generalized second-order differential transfer function G i (s) is the virtual complex impedance Z vi ; Step 7: Based on the virtual complex impedance Z introduced in step 6 vi , the output voltage command u obtained in step 5 ca_ref ,u cb_ref ,i cc_ref 、The filter capacitor voltage u obtained in step 1 ca ,u cb ,u cc and load current i oa ,i ob ,i oc , the output current command signal i is obtained through the voltage control equation a_ref ,i b_ref ,i c_ref ; According to the output current command signal i a_ref ,i b_ref ,i c_ref , the bridge arm side inductor current i obtained in step 1 La ,i Lb ,i Lc and load current i oa ,i ob ,i oc , the output voltage command u obtained in step 5 ca_ref ,i cb_ref ,u cc_ref , the control signal is obtained through the current control equation According to Generate PWM control signals for three single-phase full-bridge inverter switch tubes.

2. The power grid simulator control method based on generalized second-order differential simulated impedance characteristics according to claim 1 is characterized in that: The power angle control equation in step 3 is: Wherein, m is the power angle control droop coefficient, and J is the simulated virtual moment of inertia.

3. The power grid simulator control method based on generalized second-order differential simulated impedance characteristics according to claim 1 is characterized in that: The voltage command synthesis equation in step 5 is:

4. The power grid simulator control method based on generalized second-order differential simulated impedance characteristics according to claim 1, characterized in that: The voltage control equation and current control equation in step 7 are: Among them, K cp1 , K bp1 , K cp1 is the proportional coefficient of the first PI controller corresponding to the three single-phase full-bridge inverters, K ai1 , K bi1 , K ci1 is the integral coefficient of the first PI controller corresponding to the three single-phase full-bridge inverters, K ap2 , K bp2 , K cp2 is the proportional coefficient of the second PI controller corresponding to the three single-phase full-bridge inverters, K ai2 , K bi2 , K ci2 is the integral coefficient of the second PI controller corresponding to the three single-phase full-bridge inverters.

5. The power grid simulator control method based on generalized second-order differential simulated impedance characteristics according to claim 1, characterized in that: The virtual complex impedance Z in step 6 vi is a virtual complex impedance containing a purely inductive component, and its expression is: Among them, L va , L vb , L vc is the virtual inductance corresponding to the three single-phase full-bridge inverters.

6. The power grid simulator control method based on generalized second-order differential simulated impedance characteristics according to claim 1, characterized in that: The virtual complex impedance Z in step 6 vi is a virtual complex impedance containing resistive and inductive components, and its expression is: Among them, L va , L vb , L vc is the virtual inductance corresponding to the three single-phase full-bridge inverters, R va , R vb , R vc is the virtual resistance corresponding to the three single-phase full-bridge inverters.

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