A method and system for inverter multi-parameter coordinated adaptive VSG parallel control

Abstract

The present disclosure provides an inverter multi-parameter collaborative adaptive VSG parallel control method and system, including: sampling current and voltage data in an AC bus; performing power calculation and first-order low-pass filtering on the sampled current and voltage to obtain line impedance; adding adaptive inertia damping parameter VSG control and adaptive virtual impedance control to the control circuit; wherein the adaptive virtual impedance control adjusts the equivalent output impedance of the VSG in a biased inductive direction by compensating for the line impedance, thereby achieving parallel droop control and power balancing; effectively avoiding errors caused by external factors such as line measurement, achieving accurate power distribution, and effectively improving the parallel power balancing accuracy of microgrid inverters and system frequency stability.

Description

Technical Field

[0001] The present disclosure relates to the field of smart grid power technology, and in particular to a method and system for inverter multi-parameter collaborative adaptive VSG parallel control. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] When the microgrid is operating in island mode, due to the lack of support from the large power grid, distributed micro-source inverters are required to maintain the system voltage and frequency. The dynamic performance of the inverter plays a vital role in the stability of the power quality of the microgrid. However, since the power electronic devices that constitute the inverter do not have the "inertia" and "damping" characteristics, when the microgrid is switched on and off with large-capacity loads, it is easy to cause the system frequency to fluctuate, which will seriously affect the stability of the microgrid. In this context, the virtual synchronous generator (VSG) control technology came into being. The rotor motion equation is added to the droop control algorithm so that the inverter and the traditional synchronous generator (SG) have similar external characteristics and operating mechanisms. By adjusting the VSG output voltage amplitude and frequency and providing the inertia and damping required by the system, the stability of the microgrid system is improved [3]-[4]. With the increase in the number of distributed micro-sources and the limited capacity of a single inverter, the VSG parallel control technology has received more and more attention. How to achieve "on-demand distribution" of power when VSG is paralleled and ensure excellent power-frequency characteristics is a key technical problem in the VSG parallel system.

[0004] Zhang Bo et al. established a small signal model of parallel VSG and derived the inertia coefficient J, damping coefficient D, droop coefficient and virtual impedance Z when multiple VSGs are connected in parallel. v The matching method provides theoretical guidance for the parameter setting of parallel VSG.

[0005] To improve the power distribution accuracy of parallel VSG systems, Mahmood H et al. proposed a control strategy that leverages communication technology to enhance reactive power distribution accuracy. Using energy management system (EMS) communication, they adjusted virtual impedance to compensate for output voltage inequality caused by line impedance mismatch, thereby achieving reactive power equalization. To address the problem of droop control failing to accurately distribute reactive power when line impedance mismatch occurs, An R, Liu Z et al. employed a pulse-triggered successive approximation virtual impedance tuning control method to adaptively adjust the virtual impedance value. Drawing on the excitation regulation characteristics of synchronous generators, Xu H et al. reduced the reactive power equalization error when multiple VSGs are connected in parallel when the synchronous generator output carries a capacitive load, while also minimizing the voltage deviation caused by the droop regulation characteristics of the system. Guo Zhiqiang et al. employed a virtual negative impedance method, using Zv = -Rv + jLv to offset the resistive component of the inverter's equivalent output impedance, ensuring that the equivalent output impedance is inductive. This facilitates decoupling control of the active and reactive loops and improves droop control accuracy. Zhang Hui and his colleagues improved the excitation regulation characteristics of the reactive loop. They summed the output voltage error of the traditional reactive loop and the deviation between the AC bus UPCC and the output voltage, feeding this into an integral regulator, transforming the reactive loop into a first-order inertia link. Through appropriate parameter configuration, reactive power output is achieved according to reference instructions. Furthermore, they analyzed the uneven power distribution caused by line impedance mismatch in actual projects, detecting line impedance in real time, setting the total equivalent output impedance in proportion to the capacity, and adaptively adjusting the virtual impedance value based on line impedance.

[0006] To improve the power-frequency characteristics of parallel VSG systems, an adaptive inertia damping adjustment scheme has been proposed. This scheme uses a smaller J to reduce power oscillations during parallel operation. At the onset of a load disturbance, a larger J is used to slow the frequency rate of change. When the load disturbance ends, a smaller J is used to quickly restore the frequency to a stable value. To address the power oscillations caused by the large J parameter in parallel systems, an auxiliary damping method using feedforward frequency rate of change and power commands is used to suppress active power oscillations. However, this method only works under small-signal models, and its effectiveness under large load disturbances requires further verification. By simulating the stator reactance, a virtual stator reactance is added in series with the inverter filter inductor to adjust the inverter's equivalent output reactance and improve the active power damping ratio. Furthermore, an adaptive inertia parameter with a signed function, sgn(), is proposed. This adaptively increases or decreases the inertia parameter based on the power offset direction to damp active power oscillations. Optimal control is used to optimize the key parameters J and D in VSG control under frequency offset and frequency change rate constraints, improving the system's dynamic response characteristics in frequency and power when subjected to disturbances. However, this requires multiple iterations of the variables, resulting in a high computational load. Alternatively, based on the VSG's output power being a second-order system, an optimal second-order system is used to derive the equation satisfying the J and D parameters, incorporating the frequency change rate into the values of these two parameters and adaptively adjusting the inertial damping coefficient. However, these methods cannot effectively avoid errors caused by external factors such as line measurement, resulting in inaccurate power distribution and insufficient stability. Summary of the Invention

[0007] In order to solve the above problems, the present disclosure proposes a multi-parameter collaborative adaptive VSG parallel control method and system for inverters, which uses the power line voltage drop method to accurately calculate the line impedance and avoid errors caused by external factors such as line measurement; under the premise of ensuring that the equivalent output impedance of the inverter is configured in inverse proportion to the capacity, the adaptive virtual impedance is used to correct the line impedance of the parallel VSG inverter in real time to achieve accurate power distribution.

[0008] According to some embodiments, the present disclosure adopts the following technical solutions:

[0009] An inverter multi-parameter coordinated adaptive VSG parallel control method, comprising:

[0010] Sampling the current and voltage data in the AC bus;

[0011] The sampled current and voltage are subjected to power calculation and first-order low-pass filtering to obtain the line impedance;

[0012] Add adaptive inertia damping parameter VSG control and adaptive virtual impedance control to the control circuit;

[0013] Among them, the adaptive virtual impedance control adjusts the equivalent output impedance of the VSG towards the inductive direction by compensating for the line impedance, thereby realizing parallel droop control and power sharing.

[0014] According to other embodiments, the present disclosure adopts the following technical solutions:

[0015] An inverter multi-parameter cooperative adaptive VSG parallel control system, comprising:

[0016] Voltage and current sampling module, used to sample the current and voltage data in the AC bus;

[0017] A calculation module is used to perform power calculation and first-order low-pass filtering on the sampled current and voltage to obtain line impedance;

[0018] The adaptive control module is used to add adaptive inertia damping parameter VSG control and adaptive virtual impedance control to the control circuit.

[0019] According to some embodiments, the present disclosure adopts the following technical solutions:

[0020] A medium stores a program, which, when executed by a processor, implements the steps of a method for controlling inverter multi-parameter coordinated adaptive VSG parallel connection.

[0021] An electronic device includes a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, steps in a method for controlling inverter multi-parameter coordinated adaptive VSG parallel connection are implemented.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present disclosure addresses the problems of uneven power distribution and reduced system frequency stability during load switching caused by line impedance mismatch in parallel VSG systems, and proposes a multi-parameter collaborative adaptive VSG control strategy. First, the power line voltage drop method is used to accurately inversely calculate the line impedance, effectively avoiding errors caused by external factors such as line measurement. Under the premise of ensuring that the equivalent output impedance of the inverter is configured in inverse proportion to the capacity, the line impedance of the parallel VSG inverter is corrected in real time using adaptive virtual impedance to achieve accurate power distribution. At the same time, in order to avoid power oscillations in the parallel system and improve frequency stability, a microgrid inverter control strategy based on the collaborative adaptation of the three parameters J, D and Zv is proposed, which effectively improves the parallel power sharing accuracy of the microgrid inverter and the system frequency stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which constitute a part of the present disclosure, are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation to the present disclosure.

[0025] Figure 1 Schematic diagram of the collaborative adaptive control process of the three-level inverter in parallel with VSG disclosed in the present invention;

[0026] Figure 2 A block diagram of the adaptive virtual impedance control algorithm disclosed herein;

[0027] Figure 3 This is a schematic diagram of the active power-frequency control of the VSG disclosed in the present invention;

[0028] Figure 4 This is the block diagram of the VSG power outer loop control disclosed in the present invention;

[0029] Figure 5 The system frequency change characteristic curves of different J values disclosed in the present invention;

[0030] (a) is the step response diagram when the frequency changes with J; (b) is the step response diagram of the frequency when J takes different values;

[0031] Figure 6 The system frequency change characteristic curves of different D values disclosed in the present invention;

[0032] (a) is the step response diagram when the frequency changes with D; (b) is the step response diagram of the frequency when D takes different values;

[0033] Figure 7 is an equivalent circuit structure diagram of the power circuit disclosed herein;

[0034] (a) Π-type equivalent circuit structure diagram, (b) T-type equivalent circuit structure diagram, (c) I-type equivalent circuit;

[0035] Figure 8 Calculating a power line voltage phasor diagram for the disclosed headend;

[0036] Figure 9 This is the impedance back-calculation simulation result of the disclosed line;

[0037] (a) is the simulation result of the measured resistance R1 and the measured reactance X1; (b) is the simulation result of the measured resistance R2 and the measured reactance X2;

[0038] Figure 10 is the output power of the parallel VSG disclosed in this disclosure, Figure 10 (a) represents the output power of VSG1 and VSG2; Figure 10 (b) Multiply the output power of VSG2 by 2;

[0039] Figure 11 Comparison of output frequency between fixed parameters and coordinated parameter control in this disclosure;

[0040] Figure 12 The changing trend of the inertia parameter J disclosed in this paper;

[0041] Figure 13 is the changing trend of the damping parameter D disclosed in this paper; DETAILED DESCRIPTION

[0042] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0043] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs.

[0044] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0045] Example 1

[0046] An embodiment of the present disclosure provides an inverter multi-parameter cooperative adaptive VSG parallel control method, such as Figure 1 Shown, including:

[0047] Step S101: sampling the current and voltage data in the AC bus;

[0048] Step S102: performing power calculation and first-order low-pass filtering on the sampled current and voltage to obtain line impedance;

[0049] Step S103: adding adaptive inertia damping parameter VSG control and adaptive virtual impedance control to the control circuit;

[0050] Among them, the adaptive virtual impedance control adjusts the equivalent output impedance of the VSG towards the inductive direction by compensating for the line impedance, thereby realizing parallel droop control and power sharing.

[0051] Adaptive inertia damping parameter VSG control includes active power-frequency control, reactive power-voltage control and rotor motion equations for inertia damping parameter optimization.

[0052] Furthermore, the VSG's power outer loop control includes active-frequency control and reactive-voltage control. The rotor's equations of motion are used to assign inertia and damping characteristics to the inverter. The droop control simulates the power-frequency regulation characteristics of a synchronous generator (SG), improving the stability of the inverter system.

[0053] like Figure 3 As shown in FIG, as an embodiment, the active power-frequency control link of the VSG includes the rotor motion equation and the active power-frequency droop link. Analogous to the rotor operating characteristics of the synchronous generator, the rotor motion equation of the virtual synchronous generator is:

[0054]

[0055] Where J and D represent the virtual inertia coefficient and virtual damping coefficient, ω and ω are ref They represent the actual angular velocity and rated angular velocity of the inverter output power, θ is the electrical angle, P m is the virtual mechanical power, P e is the electromagnetic power; P m It can be obtained by the active power-frequency droop equation (2)

[0056]

[0057] Where m is the active power-frequency droop coefficient; P ref is the active power given value; f is the VSG output frequency; f ref Output frequency reference value for VSG.

[0058] Specifically, it includes two parts: the active power droop link and the realization of the rotor motion equation. The active power droop link corresponds to formula (2), and its realization process can be expressed as: VSG output frequency reference value f ref The difference between the actual output frequency f and the actual output frequency f is divided by the droop coefficient m, and then added to the given value of the active power to obtain the virtual mechanical power P m .

[0059] The rotor motion equation can be expressed as: virtual mechanical power P m and electromagnetic power P e The difference is divided by the rated angular velocity ω of the inverter ref , then subtract D*(ω-ω ref ), then divide the deviation by the virtual inertia coefficient J and integrate to obtain Δω, and then calculate Δω and ω ref The sum ω is integrated to obtain the electrical angle θ of the virtual rotor.

[0060] like Figure 4 As shown, the reactive power control strategy is:

[0061] The reactive power-voltage control part of VSG is obtained by introducing reactive power deviation, ignoring the influence of excitation current and combining the droop characteristics of SG, and obtaining the reactive power-voltage control equation as follows:

[0062] U ref =U0+n·(Q ref -Q) (3)

[0063] Where Q ref and Q are the reactive power reference value and the reactive power actual value respectively; U ref and U0 are the output voltage reference value and the output voltage actual value respectively, and n is the reactive-voltage droop coefficient.

[0064] When a microgrid supplies power to various loads, its output power quality should meet the load requirements. According to the VSG active-frequency control and reactive-voltage control links, the rotor motion equation, active-frequency droop equation, and reactive-voltage droop equation of the SG are combined to form a three-phase reference voltage, and the microgrid inverter is given "inertia" and "damping" characteristics. The overall control of the VSG power outer loop is as follows: Figure 4 As shown:

[0065] Specifically, it includes four parts: active power droop link, rotor motion equation link, power calculation + first-order low-pass filtering link, reactive power droop link and reference voltage synthesis link.

[0066] The power calculation + first-order low-pass filtering link is to detect the three-phase output voltage uabc and three-phase output current iabc of the inverter in real time, and then obtain the instantaneous active power and instantaneous reactive power according to the instantaneous power calculation method. Then, the high-frequency noise in the actual measurement is removed through the first-order low-pass filtering to obtain the active power P. e and reactive power Q, and are output to the rotor motion equation link and reactive power droop link for calculation respectively;

[0067] The reactive power droop link corresponds to formula 3, which can be expressed as: reactive power reference value Q ref The deviation from the actual value of reactive power Q is multiplied by the reactive-voltage droop coefficient n, and then added to the actual value of output voltage U0 to obtain the output voltage reference value U ref .

[0068] The reference voltage synthesis link can be expressed as follows: by obtaining the rotor electrical angle phase θ and the output reference voltage amplitude U ref Then, the three-phase reference command voltage e of the inverter can be synthesized according to the amplitude and electrical angle phase. * abc .

[0069] The three-level neutral point potential balance control algorithm is implemented using the existing segmented zero-sequence injection method.

[0070] Furthermore, when the active load increases, the influence of the virtual inertia coefficient J and virtual damping coefficient D of the VSG controller on the system frequency is analyzed.

[0071] Combining formula (1) and formula (2) we can get

[0072]

[0073] in,

[0074]

[0075] In the above formula, τ and m P They represent the active power-frequency droop coefficient and inertia time constant of VSG respectively.

[0076] Using equation (4), analyze the frequency response characteristics of the VSG when the active power step is 1kW and the J and D parameters change. Write the transfer function G between Δω(s) and ΔP(s) ω (s) is

[0077]

[0078] It should be noted that the step power is set to negative (load reduction state), so the value of the obtained frequency response characteristic curve is positive.

[0079] Depend on Figure 5 As shown in (a), it can be seen that as J increases, the frequency change rate of the system decreases; Figure 5 (b) Frequency step response for different J values. It can be clearly seen that when J increases from 0.2 to 1, the frequency response speed slows down, which means that J mainly affects the dynamic characteristics of the system frequency but does not affect the steady-state offset of the frequency.

[0080] Depend on Figure 6 As shown in (a), it can be seen that as D increases, the frequency offset of the system in steady state decreases; according to Figure 6 (b) Frequency step response for different D values. It can be clearly seen that when D increases from 2 to 10, the frequency offset decreases, which indicates that the D parameter mainly affects the steady-state characteristics of the system frequency and has little effect on the dynamic characteristics of the system frequency.

[0081] When the load is reduced, the effects of the J and D coefficients on the system frequency are similar to those when the load is increased, and will not be repeated.

[0082] Furthermore, during the operation of parallel VSGs, line impedance is difficult to measure. Because line impedance varies depending on factors such as line length and material, it cannot be precisely configured according to capacity ratio, which can easily lead to uneven power distribution. Line impedance is calculated in real time using electrical quantities, and adaptive virtual impedance compensates for it, enabling the inverter's equivalent output impedance to be configured inversely proportional to capacity. Referring to the power line voltage drop calculation method, the line impedance is calculated using the VSG output voltage and the common bus PCC voltage, facilitating subsequent adaptive virtual impedance compensation.

[0083] In the power system, there are three main types of equivalent circuits for power lines: Pi type, T type and straight type, such as Figure 7 shown.

[0084] For power lines with a length not exceeding 100 km and a rated voltage less than 60 kV, the influence of the electric field effect can be ignored, that is, the influence of the conductance G and the susceptance B can be ignored. Then the line impedance of the short power line can be considered to be Z line =R+jX.

[0085] Known line head voltage Terminal voltage When the power at the head end of the line is P1+jQ1, the line impedance can be calculated inversely. The voltage phasor of the power line when calculated from the head end is shown in Figure 8.

[0086] is the voltage drop, is the longitudinal component of voltage drop, is the voltage drop transverse component. According to the voltage phasor relationship in the figure, we get

[0087]

[0088]

[0089] Therefore, the vertical and horizontal components of the voltage drop can be expressed as

[0090]

[0091] because

[0092]

[0093] Solving formula (10), we can get the calculated values of line resistance R and line reactance X as

[0094]

[0095] It should be noted in the above formula that since the active power P and reactive power Q are three-phase powers, the voltages U1 and U2 should be calculated using the line voltages, and the unit of the power angle δ is rad.

[0096] Formula (11) can be used to accurately calculate the value of the line impedance in real time and avoid measurement deviations caused by external factors.

[0097] Set the initial impedance Z0 = 0.2 + j0.0628, Z1 = 0.9, Z0 = 0.18 + j0.0565, Z2 = 0.4, Z0 = 0.08 + j0.0251.

[0098] The simulation results are as follows Figure 9 As shown in the figure, R1, X1, R2, and X2 are the line impedance values obtained by calculation. Figure 7 As can be seen, the resistance of line 1, R1, is 0.18Ω, and X1 is 0.056Ω; the resistance of line 2, R2, is 0.08Ω, and X2 is 0.025Ω. The results of the line impedance inversion calculation remain essentially unchanged and consistent with the theoretical values. This demonstrates that the method of inverting line impedance using voltage is effective and can lay a theoretical foundation for the research of virtual impedance adaptive algorithms.

[0099] As an embodiment, adaptive virtual impedance control adjusts the equivalent output impedance of the VSG toward an inductive direction by compensating for line impedance, which is beneficial for achieving parallel droop control and power sharing.

[0100] Specifically, adaptive virtual impedance control is used to compensate for the line impedance, making the VSG equivalent output impedance inversely proportional to the capacity. After compensation, the output voltage at the common point is:

[0101]

[0102] In the above formula, Z apd It represents the value of adaptive virtual impedance, Z0 represents the equivalent output impedance setting value, U0 is the inverter output voltage, and I0 is the inverter output current.

[0103] The parallel VSG scheme adopted is implemented in the dq coordinate system, so the voltage on the virtual impedance is From the abc stationary coordinate system to the dq rotating coordinate system, we can get

[0104]

[0105] Specifically, firstly, the d-axis component i of the output current of the input three-phase inverter can be obtained by the coordinate transformation method. d and the q-axis component i q And set the equivalent output impedance to R0, L0, and the line impedance R line, L line Together with the output angular frequency ω of the inverter, it is used as the input of the adaptive virtual impedance control. According to formula (13), the conversion relationship between the variables in the algorithm block diagram can be obtained, so that the d-axis voltage component u in the dq synchronous rotating coordinate system under the adaptive virtual impedance control can be obtained. apd_d and the q-axis voltage component u apd_q .

[0106] By using the above-mentioned adaptive virtual impedance control algorithm, the inverter equivalent output impedance is controlled to be configured inversely proportional to the capacity, which can correct the power sharing problem caused by line impedance mismatch in real time. While achieving power sharing, in order to improve the frequency stability of the parallel VSG system, the virtual inertia parameter J and virtual damping parameter D in the form of piecewise functions are used. The J and D parameters are dynamically adjusted according to the frequency change rate and frequency offset to adapt to the working conditions of power mutation. The parallel VSG inertia damping parameters are selected according to the following scheme

[0107]

[0108]

[0109] In the above formula, ε i (i=1,2) represents the threshold value of the virtual inertia parameter, which is set according to the operating standard and actual operating conditions of the microgrid; ε3 represents the threshold value of the virtual damping parameter. In order to make J increase or decrease according to the power mutation state, D increases with the increase of frequency offset, and k is set. J1 >0,k J2 <0,k D > 0. The specific parameter value needs to be set according to the actual operating power of the inverter.

[0110] Based on the above theoretical analysis, a simulation model of a parallel VSG three-level inverter was built using MATLAB / Simulink. The main parameters of the parallel inverter are shown in Table 1.

[0111] Table 1 Parallel VSG three-level simulation parameters

[0112] Main circuit parameters value <![CDATA[DC bus voltage U dc1，2 / V]]> 800 <![CDATA[Filter inductor L 1，2 / mH > 2 <![CDATA[Filter inductor C 1，2 / uF > 30 <![CDATA[Rated AC side voltage U N / V]]> 311 <![CDATA[Line impedance Z1 / Ω]]> 0.2+j0.0628 <![CDATA[Line impedance Z2 / Ω]]> 0.2+j0.0628 Control parameters value <![CDATA[Active droop coefficient K w > 1e4 Reactive power droop coefficient n 6.28e-3 <![CDATA[Moment of inertia J0 / kg·m 2 > 0.2 <![CDATA[Damping coefficient D0]]> 10 <![CDATA[Equivalent output impedance Z0 / Ω]]> 0.2+j0.0628 <![CDATA[Voltage loop proportional coefficient k up > 0.9 <![CDATA[Voltage loop integral coefficient k ui > 70 <![CDATA[Current loop proportionality coefficient k up > 2.5

[0113] After two VSG inverters are connected in parallel, the line impedance ratio connected through the LC filter output is set to Z1:Z2=1:1, and the inverter output is 2:1 to verify the control effect of the proposed parallel NPC three-level parameter coordinated VSG control scheme.

[0114] To verify the power sharing effect, the simulation time was set to 0.8s. From 0 to 0.2s, a traditional virtual impedance control strategy was used, ignoring the impact of line impedance on reactive power sharing. The parameter-coordinated adaptive VSG control strategy was switched in at 0.2s, with loading at 0.4s and load shedding at 0.6s. The rated operating power of VSG1 and VSG2 was Pref1 = 10kW, Qref1 = 3kVar, and Pref2 = 5kW, Qref2 = 1.5kVar, with a capacity ratio of 2:1.

[0115] Figure 10 is the output power of the parallel VSG, Figure 10 (a) represents the output power of VSG1 and VSG2; Figure 10 (b) Multiply the output power of VSG2 by 2 to observe the output power distribution. When using the traditional virtual impedance control strategy (adding virtual impedance Z0), there is a difference in the output voltages of VSG1 and VSG2, resulting in a significant reactive power imbalance of approximately 250Var. However, because the active power output meets the fP droop characteristic curve, the active power is essentially evenly distributed.

[0116] After the parallel parameter-coordinated VSG control strategy is activated at 0.2s, the line impedance is corrected through adaptive virtual impedance, ensuring that the equivalent output impedance of the two VSGs is configured in inverse proportion to their capacity, achieving equal distribution of reactive power. Furthermore, the proposed control strategy still achieves equal power distribution during power disturbances at 0.4s and 0.6s. Therefore, the parallel parameter-coordinated VSG control strategy achieves precise power distribution even when the line impedance is unknown.

[0117] Formulas (14) and (15) give the value scheme of the parallel adaptive J and D parameters. After the parameters of VSG1 are set, let J1 = 2J2 and D1 = 2D2 to complete the setting of the key parameters of VSG2.

[0118]

[0119]

[0120] In the above formula, D0 is the reference value of virtual damping parameter in steady state, J0 is the reference value of moment of inertia in steady state, k J1 、k J2 and k D is the adjustment coefficient, Δω is the difference between the actual angular velocity ω output by the inverter and the rated angular velocity ω ref .

[0121] ε i (i=1,2) represents the threshold of the virtual inertia parameter, which is set according to the microgrid operation standard and actual operating conditions; ε3 represents the threshold of the virtual damping parameter.

[0122] like Figure 11 As shown in the figure, it can be seen that compared with the fixed parameter VSG control scheme, the system frequency offset is further reduced; when loading at 0.4s, the deviation speed of the system frequency slows down; when unloading at 0.6s, the recovery speed of the system frequency speeds up.

[0123] like Figure 12 and Figure 13 As shown, during the 0.4s loading phase, when the frequency change rate and frequency offset exceed the set threshold, J increases, slowing the parallel system's frequency response. This helps address the problem of excessively fast transient response speeds in traditional power electronic devices when load power abruptly changes. During the 0.6s load reduction phase, when the frequency change rate and frequency offset exceed the set threshold, J decreases, accelerating the parallel system's frequency response, helping the system frequency return to a steady-state operating point more quickly. When the frequency offset exceeds the set threshold, D increases, essentially reducing the active power droop coefficient and further minimizing the system's steady-state frequency offset.

[0124] The values of the adaptive J and D parameters fully consider the fluctuation characteristics of the frequency offset and frequency change rate during small disturbances. By setting the frequency change rate and frequency offset thresholds, it is ensured that the J and D parameters will not change frequently when the system is disturbed, further improving the frequency stability of the parallel system.

[0125] Example 2

[0126] An embodiment of the present disclosure provides an inverter multi-parameter coordinated adaptive VSG parallel control system, including:

[0127] Voltage and current sampling module, used to sample the current and voltage data in the AC bus;

[0128] A calculation module is used to perform power calculation and first-order low-pass filtering on the sampled current and voltage to obtain line impedance;

[0129] The adaptive control module is used to add adaptive inertia damping parameter VSG control and adaptive virtual impedance control to the control circuit.

[0130] The adaptive virtual impedance control adjusts the equivalent output impedance of the VSG toward an inductive direction by compensating for the line impedance, thereby achieving parallel droop control and power sharing.

[0131] The above system implements a multi-parameter coordinated adaptive VSG parallel control method for inverters, including:

[0132] Sampling the current and voltage data in the AC bus;

[0133] The sampled current and voltage are subjected to power calculation and first-order low-pass filtering to obtain the line impedance;

[0134] Add adaptive inertia damping parameter VSG control and adaptive virtual impedance control to the control circuit;

[0135] Among them, the adaptive virtual impedance control adjusts the equivalent output impedance of the VSG towards the inductive direction by compensating for the line impedance, thereby realizing parallel droop control and power sharing.

[0136] Example 3

[0137] An embodiment of the present disclosure provides a medium having a program stored thereon, which, when executed by a processor, implements steps in a method for inverter multi-parameter coordinated adaptive VSG parallel control.

[0138] Example 4

[0139] An embodiment of the present disclosure provides an electronic device, including a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, steps in a method for multi-parameter collaborative adaptive VSG parallel control of an inverter are implemented.

[0140] The present disclosure is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present disclosure. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0141] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0142] Although the above describes the specific implementation methods of the present disclosure in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present disclosure. Those skilled in the art should understand that on the basis of the technical solution of the present disclosure, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present disclosure.

Claims

1. A multi-parameter cooperative adaptive VSG parallel control method for inverters, characterized in that: include: Sampling the current and voltage data in the AC bus; The sampled current and voltage are subjected to power calculation and first-order low-pass filtering to obtain the line impedance; Add adaptive inertia damping parameter VSG control and adaptive virtual impedance control to the control circuit; Among them, the adaptive virtual impedance control adjusts the equivalent output impedance of the VSG towards the inductive direction by compensating for the line impedance, thereby achieving parallel droop control and power sharing; Adaptive virtual impedance control is used to compensate for line impedance, making the VSG equivalent output impedance inversely proportional to the capacity. After compensation, the output voltage at the common point is: In the above formula, Z apd represents the value of the adaptive virtual impedance, Z 0 represents the equivalent output impedance setting value, U 0 is the inverter output voltage, I 0 is the inverter output current, Z line is the line impedance of the short power line.

2. The inverter multi-parameter cooperative adaptive VSG parallel control method according to claim 1, characterized in that: Convert the voltage on the virtual impedance from the stationary coordinate system to the rotating coordinate system.

3. The inverter multi-parameter cooperative adaptive VSG parallel control method according to claim 1, characterized in that: The adaptive inertia damping parameter VSG control includes active power-frequency control, reactive power-voltage control and rotor motion equations for inertia damping parameter optimization.

4. The inverter multi-parameter cooperative adaptive VSG parallel control method according to claim 3, characterized in that: VSG active frequency control includes the rotor motion equation and the active-frequency droop link. The rotor motion equation of the virtual synchronous generator is: Where, J and D denote the virtual inertia coefficient and virtual damping coefficient respectively, ω and ω ref They represent the actual angular velocity and rated angular velocity of the inverter output power respectively, Ɵ is the electrical angle, P m is the virtual mechanical power, P e is the electromagnetic power; Δω represents: the actual angular velocity ω of the inverter output power and the rated angular velocity ω ref difference.

5. The inverter multi-parameter cooperative adaptive VSG parallel control method according to claim 3, characterized in that: The reactive power-voltage control of VSG is achieved by introducing reactive power deviation, ignoring the influence of excitation current and combining the droop characteristics of SG. The reactive power-voltage control equation is: Where, Q ref and Q They are reactive power reference value and reactive power actual value respectively; U ref and U 0 are the output voltage reference value and the output voltage actual value respectively, n is the reactive-voltage droop coefficient.

6. An inverter multi-parameter cooperative adaptive VSG parallel control system, characterized in that: include: Voltage and current sampling module, used to sample the current and voltage data in the AC bus; A calculation module is used to perform power calculation and first-order low-pass filtering on the sampled current and voltage to obtain line impedance; Adaptive control module, used to add adaptive inertia damping parameter VSG control and adaptive virtual impedance control to the control circuit; Adaptive virtual impedance control is used to compensate for line impedance, making the VSG equivalent output impedance inversely proportional to the capacity. After compensation, the output voltage at the common point is: In the above formula, Z apd represents the value of the adaptive virtual impedance, Z 0 represents the equivalent output impedance setting value, U 0 is the inverter output voltage, I 0 is the inverter output current, Z line is the line impedance of the short power line.

7. The inverter multi-parameter cooperative adaptive VSG parallel control system according to claim 6, characterized in that: The adaptive virtual impedance control adjusts the equivalent output impedance of the VSG toward an inductive direction by compensating for the line impedance, thereby achieving parallel droop control and power sharing.

8. A medium having a program stored thereon, characterized in that: When the program is executed by a processor, the steps of the inverter multi-parameter collaborative adaptive VSG parallel control method as described in any one of claims 1 to 5 are implemented.

9. An electronic device comprising a memory, a processor, and a program stored in the memory and executable on the processor, wherein: When the processor executes the program, the steps in the inverter multi-parameter collaborative adaptive VSG parallel control method as described in any one of claims 1 to 5 are implemented.

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