General networking control method for converter

Abstract

The invention relates to a general network construction control method for a converter, the converter is connected to a common connection point through an LCL filter, the control link comprises an active outer ring, a reactive outer ring, a virtual impedance ring and a voltage and current control ring, and in the reactive voltage control link, a voltage amplitude difference value and a reactive power difference value are obtained through calculation; multiplying and superposing with a voltage feedback coefficient and a reactive power regulation coefficient, and generating a voltage amplitude reference of a converter voltage loop through a proportional-integral regulator; in the active frequency control link, a frequency difference value and an active power difference value are obtained through calculation, are multiplied by a frequency feedback coefficient and an active adjustment coefficient respectively and then are superposed, and a frequency reference of a voltage inner loop is generated through a proportional-integral regulator; in the general networking control process, outer loop control parameters are changed according to different application scenes, and different active loop and reactive loop control is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of network control, and proposes a network control method and a converter based on virtual synchronous generator control, which can realize multi-type network control and has primary frequency regulation, primary voltage regulation and inertia support capabilities. Background Art

[0002] With the increasing number and power level of renewable energy power generation, mainly wind power and photovoltaic power, the application of high proportion of renewable energy and high proportion of power electronic equipment has become a new feature of the power system, and the number of power electronic converters connected to the power grid is increasing. At present, there are two control modes of converters: grid-forming (GFM) and grid-following (GFL). Grid-following control requires the use of a phase-locked loop to synchronize with the grid. There are small disturbance stability problems in weak grids, and it is suitable for use in strong grids. Grid-forming control adopts a power synchronization strategy similar to that of synchronous generators. It has voltage support and active inertia support characteristics. It can replace synchronous machines to achieve grid support, and has the ability to operate with load without an external power grid. It is suitable for use in power grids with weak system strength and low physical inertia. [1-2] . Grid control mainly includes droop control and virtual synchronous machine control. Among them, virtual synchronous machine control has a variety of control structures. References [3-6] proposed a variety of grid control structures, including active power regulation and reactive power regulation. Reference [7] introduced two types of virtual synchronous generator control technologies, current control type and voltage control type. Reference [8] proposed a grid control with a unified reactive power control structure. Based on this, the present invention proposes a universal grid control with a unified architecture for active and reactive power control loops.

[0003] References

[0004] [1] Xu Jieyi, Liu Wei, Liu Shu, et al. Current status and development trend of power system converter grid control technology[J]. Power System Technology, 2022, 46(09): 3586-3595.2021.2149.

[0005] [2] Zhao Zhihong. Research on grid-connected current loop control and off-grid power generation application of energy storage converter[D]. Nanjing: Southeast University, 2017.

[0006] [3] Ding Ming, Yang Xiangzhen, Su Jianhui. Microgrid inverter power supply control strategy based on virtual synchronous generator[J]. Automation of Electric Power Systems, 2009, 33(08):89-93.

[0007] [4] Lü Zhipeng, Sheng Wanxing, Zhong Qingchang, et al. Virtual synchronous generator and its application in microgrid [J]. Proceedings of the CSEE, 2014, 34(16): 2591-2603.

[0008] [5]Hirase Y,Sugimoto K,Sakimoto K,et al.Analysis ofResonance inMicrogrids and Effects of System Frequency Stabilization using a VirtualSynchronous Generator[J].IEEE Journal of Emerging&Selected Topics in PowerElectronics,2016:1-1.

[0009] [6] Zheng Tianwen, Chen Laijun, Chen Tianyi, et al. Virtual synchronous generator technology and prospects[J]. Automation of Electric Power Systems, 2015, 39(21): 165-175.

[0010] [7] Zhang Xing, Zhu Debin, Xu Haizhen. Virtual synchronous generator technology in distributed generation[J]. Journal of Power Supply, 2012(03):1-6+12.

[0011] [8]F.Zhao,Z.Shuai,W.Huang,et al.Unified Model ofVoltage-ControlledInverter for Transient Angle StabilityAnalysis[J].IEEE Transactions on PowerDelivery,2022,37(3):2275-2288. Summary of the invention

[0012] The present invention discloses a general network control method for converters. A detailed electromagnetic transient simulation model example is built on the PSCAD / EMTDC simulation platform, and the effectiveness of the general network control method proposed by the present invention is verified through a variety of transient simulation conditions. The technical solution is as follows:

[0013] A universal network control method for a converter, wherein the converter is connected to a common connection point through an LCL filter, and the control links thereof include an active outer loop, a reactive outer loop, a virtual impedance loop and a voltage and current control loop. In the reactive voltage control link, a voltage amplitude difference and a reactive power difference are obtained by calculation, which are respectively multiplied with a voltage feedback coefficient and a reactive regulation coefficient and then superimposed, and a voltage amplitude reference of a converter voltage loop is generated through a proportional-integral regulator; in the active frequency control link, a frequency difference and an active power difference are obtained by calculation, which are respectively multiplied with a frequency feedback coefficient and an active regulation coefficient and then superimposed, and a frequency reference of a voltage inner loop is generated through a proportional-integral regulator; in the universal network control process, the outer loop control parameters are changed according to different application scenarios to realize different active loop and reactive loop controls.

[0014] Here are the steps:

[0015] Step 1: The converter controller collects the three-phase voltage u of the filter capacitor through the sensor c_abc , three-phase current i of the filter inductor on the converter side Lf_abc , grid-side filter inductor three-phase current i g_abc ;

[0016] Step 2: Collect the three-phase voltage and current u c_abc 、i Lf_abc 、i g_abc Perform PARK transformation to obtain the voltage u in the dq rotating coordinate system c_dq and current i Lf_dq 、i g_dq , and calculate the voltage amplitude V vsc ;

[0017] Step 3: Calculate the active power P and reactive power Q output by the converter. According to the chronotropic power theory, use the voltage u c_dq Current i Lf_dq Calculate the active and reactive power output by the three-phase converter;

[0018] Step 4: Convert active power P and active power reference P * As well as the rotor angular frequency ω and the reference frequency ω * Input active power outer loop; the active power outer loop converts P and P * Active power deviation and active power regulation coefficient k p Multiplying, ω and ω * The frequency deviation and frequency feedback coefficient k f Multiply them, and the two are superimposed and passed through the proportional-integral controller to obtain the rotor angular frequency reference ω of the converter, and ω is further integrated to obtain the phase angle reference θ;

[0019] Reactive power Q and reactive power reference Q * and the converter voltage amplitude V vscWith reference voltage amplitude V * Input reactive outer loop; the reactive outer loop converts Q and Q * Reactive power deviation and reactive power regulation coefficient k q Multiply, V vsc and V * Voltage deviation and voltage feedback coefficient k v Multiply them, and the two are superimposed and passed through the proportional integral controller to obtain the voltage amplitude reference E of the converter;

[0020] Step 5: Voltage amplitude reference E as d-axis voltage reference v dref , q-axis voltage reference v qref Set to 0, and get the voltage reference u after passing through the virtual impedance link * d and u * q

[0021] Step 6: Voltage Loop DQ Axis Reference U * dq , capacitor voltage u c_dq , the inductor current i on the converter side Lf_dq , grid-side inductor current i g_dq The input voltage and current dual-loop control unit generates a modulation voltage v invd and v invq ;

[0022] Step 7: v invd and v invq Based on PWM modulation output modulation signal, the power devices of the converter are controlled; in the general network control process, the outer loop control parameters are changed according to different application scenarios to achieve different active loop and reactive loop controls.

[0023] Further: Let k p_APC and k i_APC are the frequency ratio and integral coefficient respectively, s is the Laplace operator, and the active power regulation coefficient k of the outer loop control of the network is changed p , frequency feedback coefficient k f , reactive power regulation coefficient k q , voltage feedback coefficient k v As well as the voltage and frequency proportional integral coefficients, different control forms can be achieved:

[0024] If k p , k f , k p_APC and k i_APC All are not 0, and the active outer loop control is shown in formula (1), which can respond to the active power command and grid frequency disturbance, and provide active support for the grid when the grid frequency changes;

[0025]

[0026] If k p , k f and k i_APC All are not 0, k p_APC If is 0, the control expression of the active outer loop is as shown in equation (3), which has the same form as the expression of the speed regulation equation of the simulated synchronous generator and can respond to the active power command and the grid frequency disturbance;

[0027]

[0028] If k p and k p_APC All are not 0, k i_APC and k f is 0, then the control expression of the active outer loop is as shown in formula (4), which belongs to active droop control:

[0029] ω=ω * +k p_APC *k p (P * -P) (4)

[0030] If k f , k p_APC and k i_APC All are not 0, k p is 0, then the control expression of the active outer loop is as shown in formula (5), which belongs to constant frequency control:

[0031]

[0032] Further: Let k p_RPC and k i_RPC are the voltage proportion and integral coefficient respectively, s is the Laplace operator; changing the active power regulation coefficient k of the outer loop control of the network p , frequency feedback coefficient k f , reactive power regulation coefficient k q , voltage feedback coefficient k v As well as the voltage and frequency proportional integral coefficients, different control forms can be achieved:

[0033] If k q , k v , k p_RPC and k i_RPC If both are not 0, the reactive outer loop control expression is as shown in equation (2), which can respond to reactive power instructions and grid voltage disturbances and provide active support for reactive power when the grid voltage changes:

[0034]

[0035] If kq , k v and k i_RPC All are not 0, k p_APC is 0, then the control expression of the reactive outer loop is shown in equation (6), which has the same form as the expression of the excitation voltage regulation equation simulating the synchronous generator and can respond to reactive power commands and grid voltage disturbances:

[0036]

[0037] If k q and k p_RPC All are not 0, k i_RPC and k v is 0, then the control expression of the reactive power outer loop is shown in equation (7), which has the same form as the traditional reactive power droop control:

[0038] E=v * +k p_RPC *k q (Q * -Q) (7)

[0039] If k q and k i_RPC All are not 0, k p_RPC and k v is 0, then the control expression of the reactive outer loop is shown in equation (8), which has the same form as the QV droop control with integration:

[0040]

[0041] If k v , k p_RPC and k i_RPC All are not 0, k q is 0, then the control expression of the reactive outer loop is shown in equation (9), which has the same form as the constant voltage control:

[0042]

[0043] The beneficial effects of the present invention are as follows:

[0044] 1) The present invention proposes a universal grid control technology that meets the technical specifications of grid converters. The control structure is as follows: Figure 1 As shown, the active regulation coefficient, frequency feedback coefficient, reactive regulation coefficient, voltage feedback coefficient and proportional integral coefficient of the active and reactive outer loop of the grid-connected converter can be easily designed directly according to the requirements of technical specifications.

[0045] 2) The universal network control technology proposed in the present invention can realize different active power control and reactive power control schemes by changing the outer loop control coefficient, and has good adaptability.

[0046] 3) Compared with the traditional virtual synchronous generator control, the universal network control technology proposed in the present invention has a simpler and more symmetrical structure, and realizes the frequency modulation, voltage regulation and inertial support control of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Schematic diagram of general grid control for grid-connected converters

[0048] Figure 2 General network control outer loop control structure block diagram

[0049] Figure 3 Transient simulation results for case 1

[0050] Figure 4 Transient simulation results for Case 2

[0051] Figure 5 Transient simulation results for case 3

[0052] Figure 6 Transient simulation results for Case 4

[0053] Figure 7 Transient simulation results for Case 5

[0054] Figure 8 Transient simulation results for Case 6

[0055] Fig. 9 Transient simulation results for Case 7

[0056] Fig.10 Transient simulation results of case 8

[0057] Fig.11 Transient simulation results of case 9 DETAILED DESCRIPTION

[0058] The general grid control of the grid-connected converter mainly includes the active frequency control link, the reactive voltage control link, the virtual impedance link, the voltage outer loop control link and the current inner loop control link. Figure 1 As shown, where ω is the rotor angular frequency, ω * is the rated angular frequency, E is the internal potential generated by the universal grid control, v * is the rated output voltage, V is the actual output voltage, θ is the phase angle generated by the grid control, P is the output active power, Q is the output reactive power, P * is the active power command, Q * is the reactive power command, k p is the frequency modulation coefficient, k q is the voltage regulation coefficient, k f is the frequency feedback coefficient, k v is the voltage feedback coefficient, uc _ d Capacitor voltage d-axis component, u c _ q is the q-axis component of the capacitor voltage, i g_d The d-axis component of the grid-side inductor current, i g_q is the q-axis component of the grid current, F is the grid current feedforward coefficient, i Lfd is the d-axis component of the inductor current on the converter side, i Lfq is the q-axis component of the inductor current on the converter side, L f is the filter inductor value, C is the filter capacitor value, R v is the virtual resistor value, L v is the virtual inductance value. The universal network outer loop control generates the voltage amplitude and phase angle reference, and obtains the voltage reference u in the dq coordinate system through the virtual impedance link. d * and u q * , and then the current reference i is obtained through the voltage inner loop control d * and i q * , and finally the modulation voltage v is obtained through the current inner loop invd and v invq .

[0059] The specific control process is as follows:

[0060] Step 1: The converter controller collects the three-phase voltage U of the filter capacitor through the sensor c_abc , three-phase current i of the filter inductor on the converter side Lf_abc , grid-side filter inductor three-phase current i g_abc .

[0061] Step 2: Collect the three-phase voltage and current U vsc_abc 、i Lf_abc 、i g_abc Perform PARK transformation to obtain the voltage u in the dq rotating coordinate system c_dq and current i Lf_dq 、i g_dq , and calculate the voltage amplitude V vsc .

[0062] Step 3: Calculate the active power P and reactive power Q output by the converter. According to the chronotropic power theory, use the voltage u vsc_dq Current i Lf_dq The active and reactive power output by the three-phase converter is calculated as follows.

[0063]

[0064] Step 4: Convert active power P and active power reference P * As well as the rotor angular frequency ω and the reference frequency ω * Input such as Figure 2 The active outer loop converts P and P * Active power deviation and active power regulation coefficient k p Multiplying, ω and ω * The frequency deviation and frequency feedback coefficient k f Multiply them together, and the two are superimposed and passed through the proportional-integral controller to obtain the rotor angular frequency reference ω of the converter. ω is then integrated to obtain the phase angle reference θ. * and the converter voltage amplitude V vsc With reference voltage amplitude V * Input such as Figure 2 The reactive outer loop converts Q and Q * Reactive power deviation and reactive power regulation coefficient k q Multiply, V vsc and V * Voltage deviation and voltage feedback coefficient k v Multiply them, and the two are superimposed and passed through the proportional integral controller to obtain the voltage amplitude reference E of the converter. Therefore, the mathematical expression of the general network control outer loop is:

[0065]

[0066] Before the program runs, you only need to change the active loop control parameters or reactive control parameters to achieve different control functions. The details are as follows:

[0067] ⒈Active external loop

[0068] ①k p , k f and k i_APC Not equal to 0, k p_APC = 0, the control expression of the active outer loop is as shown in equation (12). The active outer loop simulates the speed regulation and inertia equations of the synchronous generator and can respond to active commands and grid frequency disturbances.

[0069]

[0070] ②k p and k p_APC Not equal to 0, k i_APC and k f If is equal to 0, the control expression of the active outer loop is as shown in equation (13), and the active outer loop realizes active droop control.

[0071]

[0072] ③kf , k p_APC and k i_APC Are not equal to 0, k p If is equal to 0, the control expression of the active outer loop is as shown in equation (14), and the active outer loop can achieve constant frequency control.

[0073]

[0074] ⒉ Reactive external loop

[0075] ①If k q , k v and k i_RPC Are not equal to 0, k p_APC If is equal to 0, the control expression of the reactive outer loop is as shown in equation (15). The reactive outer loop simulates the excitation voltage regulation equation of the synchronous generator and can respond to reactive commands and grid voltage disturbances.

[0076]

[0077] ②If k q and k p_RPC Are not equal to 0, k i_RPC and k v If is equal to 0, the control expression of the reactive outer loop is as shown in equation (16), and the reactive outer loop realizes reactive droop control.

[0078] E=v * +k p_RPC *k q (Q * -Q) (16)

[0079] ③If k q and k i_RPC Are not equal to 0, k p_RPC and k v If is equal to 0, the control expression of the reactive outer loop is as shown in equation (17), and the reactive outer loop realizes QV droop control with integration.

[0080]

[0081] ④ If k v , k p_RPC and k i_RPC Are not equal to 0, k q If is equal to 0, the control expression of the reactive outer loop is as shown in equation (18), and the reactive outer loop realizes constant voltage control.

[0082]

[0083] Step 5: Voltage amplitude reference E as d-axis voltage reference v dref , q-axis voltage reference vqref Set to 0, after Figure 1 After the virtual impedance link, the voltage reference u is obtained * d and u * q .

[0084] Step 6: Voltage Loop DQ Axis Reference U * dq , capacitor voltage u c_dq , the inductor current i on the converter side Lf_dq , grid-side inductor current i g_dq The input voltage and current dual-loop control unit generates a modulation voltage v invd and v invq .

[0085] The control expression of the voltage loop is shown as follows, k p_v and k i_v They are the voltage loop proportional and integral coefficients respectively.

[0086]

[0087] The control expression of the current loop is shown as follows, k p_c and k i_c They are the current loop proportional and integral coefficients respectively.

[0088]

[0089] Step 7: v invd and v invq Based on the PWM modulation output modulation signal, the power devices of the converter are controlled.

[0090] Built with PSCAD / EMPDC Figure 1 The simulation example shown verifies the general network control method of the present invention, and the system parameters are shown in Table 3.

[0091] Table 3 System parameters

[0092] Table 3 System parameter

[0093]

[0094] Table 4 Outer loop control parameters

[0095]

[0096] Different types of control can be achieved by selecting different outer loop control parameters as shown in Table 4 above, and simulation verification of different working conditions can be performed for different types of control.

[0097] 1. General network active power control

[0098] ① Simulation condition 1: the grid frequency drops from 1pu to 0.996pu in 5s, the converter frequency drops to 0.996pu, and the active output increases by 0.08pu.

[0099] ② Simulation condition 2: The active power command jumps from 0.5pu to 0.6pu in 5s. The converter can quickly track the active power command.

[0100] Active power output increased to 0.6pu.

[0101] ③ Simulation condition 3: The grid voltage drops from 1pu to 0.98pu in 5s, and the port voltage drops first and then rises to 0.995pu.

[0102] The reactive power rises to 0.095pu.

[0103] ④Simulation condition 4: The reactive power instruction jumps from 0pu to 0.2pu in 5s, the port voltage rises to 1.007pu, and the reactive power rises to 0.06pu.

[0104] 2. Simulate synchronous generator control

[0105] ① Simulation condition 5: the grid frequency jumps from 1pu to 1.004pu in 5s, the converter frequency jumps to 1.004pu, and the active output decreases by 0.08pu.

[0106] ② Simulation condition 6: Simulate the synchronous generator excitation voltage regulation equation. The grid voltage jumps from 1pu to 1.02pu in 5s, the port voltage drops to 1.0025pu, and the reactive power drops to -0.05pu.

[0107] 3. Droop control

[0108] ① Simulation condition 7: the grid frequency drops from 1pu to 0.996pu in 5s, and the active output increases by 0.04pu.

[0109] ② Simulation condition 8: The grid voltage drops from 1pu to 0.98pu in 5s, and the port voltage drops from 0.975pu to 0.955pu.

[0110] The reactive power increased from -0.086pu to -0.078pu.

[0111] 4. Constant voltage and frequency control

[0112] ① Simulation condition 9: disconnect the switch connected to the grid. When off-grid, add 0.1MVA load on top of 0.1MW load 5s later. The converter frequency remains unchanged, and the active output increases by 1 times. The converter output voltage remains unchanged, and the reactive power increases to 0.045pu.

[0113] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A general inverter network control method, characterized in that: The converter is connected to the public connection point through an LCL filter. Its control links include an active outer loop, a reactive outer loop, a virtual impedance loop and a voltage and current control loop. In the reactive voltage control link, the voltage amplitude difference and the reactive power difference are obtained by calculation, which are multiplied with the voltage feedback coefficient and the reactive regulation coefficient respectively and then superimposed. The voltage amplitude reference of the converter voltage loop is generated through a proportional-integral regulator. In the active frequency control link, the frequency difference and the active power difference are obtained by calculation, which are multiplied with the frequency feedback coefficient and the active regulation coefficient respectively and then superimposed. The frequency reference of the voltage inner loop is generated through a proportional-integral regulator. In the general network control process, the outer loop control parameters are changed according to different application scenarios to achieve different active loop and reactive loop controls.

2. The universal network control method for converters according to claim 1, characterized in that: Here are the steps: Step 1: The converter controller collects the three-phase voltage u of the filter capacitor through the sensor c_abc , three-phase current i of the filter inductor on the converter side Lf_abc , grid-side filter inductor three-phase current i g_abc ; Step 2: Collect the three-phase voltage and current u c_abc 、i Lf_abc 、i g_abc Perform PARK transformation to obtain the voltage u in the dq rotating coordinate system c_dq and current i Lf_dq 、i g_dq , and calculate the voltage amplitude V vsc ; Step 3: Calculate the active power P and reactive power Q output by the converter. According to the chronotropic power theory, use the voltage u c_dq Current i Lf_dq Calculate the active and reactive power output by the three-phase converter; Step 4: Convert active power P and active power reference P * As well as the rotor angular frequency ω and the reference frequency ω * Input active power outer loop; the active power outer loop converts P and P * Active power deviation and active power regulation coefficient k p Multiplying, ω and ω * The frequency deviation and frequency feedback coefficient k f Multiply them, and the two are superimposed and passed through the proportional-integral controller to obtain the rotor angular frequency reference ω of the converter, and ω is further integrated to obtain the phase angle reference θ; The reactive power Q is compared with the reactive power reference Q * and the converter voltage amplitude V vsc With reference voltage amplitude V * Input reactive outer loop; the reactive outer loop converts Q and Q * Reactive power deviation and reactive power regulation coefficient k q Multiply, V vsc and V * Voltage deviation and voltage feedback coefficient k v Multiply them, and the two are superimposed and passed through the proportional integral controller to obtain the voltage amplitude reference E of the converter; Step 5: Voltage amplitude reference E as d-axis voltage reference v dref , q-axis voltage reference v qref Set to 0, and get the voltage reference u after passing through the virtual impedance link * d and u * q Step 6: Voltage Loop DQ Axis Reference U * dq , capacitor voltage u c_dq , the inductor current i on the converter side Lf_dq , grid-side inductor current i g_dq The input voltage and current dual-loop control unit generates a modulation voltage v invd and v invq ; Step 7: v invd and v invq The modulation signal is output based on PWM modulation to control the power devices of the converter.

3. The universal network control method for converters according to claim 1, characterized in that: Let k p_APC and k i_APC are the frequency ratio and integral coefficient respectively, s is the Laplace operator, and the active power regulation coefficient k of the outer loop control of the network is changed p , frequency feedback coefficient k f , reactive power regulation coefficient k q , voltage feedback coefficient k v As well as the voltage and frequency proportional integral coefficients, different control forms can be achieved: If k p , k f , k p_APC and k i_APC All are not 0, and the active outer loop control is shown in formula (1), which can respond to the active power command and grid frequency disturbance, and provide active support for the grid when the grid frequency changes; If k p , k f and k i_APC All are not 0, k p_APC If is 0, the control expression of the active outer loop is as shown in equation (3), which has the same form as the expression of the speed regulation equation of the simulated synchronous generator and can respond to the active power command and the grid frequency disturbance; If k p and k p_APC All are not 0, k i_APC and k f is 0, then the control expression of the active outer loop is as shown in formula (4), which belongs to active droop control: oh = oh * +k p_APC *k p (P * -P) (4) If k f , k p_APC and k i_APC All are not 0, k p is 0, then the control expression of the active outer loop is as shown in formula (5), which belongs to constant frequency control:

4. The universal grid control method for converters according to any one of claims 2 or 3, characterized in that: Let k p_RPC and k i_RPC are the voltage proportion and integral coefficient respectively, s is the Laplace operator; changing the active power regulation coefficient k of the outer loop control of the network p , frequency feedback coefficient k f , reactive power regulation coefficient k q , voltage feedback coefficient k v As well as the voltage and frequency proportional integral coefficients, different control forms can be achieved: If k q , k v , k p_RPC and k i_RPC If both are not 0, the reactive outer loop control expression is as shown in equation (2), which can respond to reactive power instructions and grid voltage disturbances and provide active support for reactive power when the grid voltage changes: If k q , k v and k i_RPC All are not 0, k p_APC is 0, then the control expression of the reactive outer loop is shown in equation (6), which has the same form as the expression of the excitation voltage regulation equation simulating the synchronous generator and can respond to reactive power commands and grid voltage disturbances: If k q and k p_RPC All are not 0, k i_RPC and k v is 0, then the control expression of the reactive power outer loop is shown in equation (7), which has the same form as the traditional reactive power droop control: E=v * +k p_RPC *k q (Q * -Q) (7) If k q and k i_RPC All are not 0, k p_RPC and k v is 0, then the control expression of the reactive outer loop is shown in equation (8), which has the same form as the QV droop control with integration: If k v , k p_RPC and k i_RPC All are not 0, k q is 0, then the control expression of the reactive outer loop is shown in formula (9), which has the same form as the constant voltage control:

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