Reactive power control method and system for a net-following converter

Abstract

The application discloses a reactive power control method and system of a grid-connected converter, and comprises the following steps: calculating a q-axis reference current i gq_ref of the grid-connected converter through a reactive power reference value, and compensating for the error of the q-axis reference current i gq_ref through an integral element; cross-coupling and compensating for a d-axis output current and a q-axis output current of the grid-connected converter to obtain a q-axis current compensation current; comparing the q-axis reference current i gq_ref with the q-axis current compensation current, processing the error of the two through a PI controller to generate a final q-axis control voltage u sq ; and converting the q-axis control voltage u sq into a q-axis output current of the grid-connected converter, so that the q-axis output current is equal to the given current reference value, thereby realizing the reactive power control of the grid-connected converter. The application introduces a feedforward control element, calculates the output current reference value through the reactive power reference value, and simultaneously introduces an integral element to compensate for the calculation error, thereby improving the response speed and the support speed of the reactive voltage.

Description

Technical Field

[0001] This invention relates to the field of grid-connected converter control technology, and in particular to a reactive power control method and system for grid-connected converters. Background Technology

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

[0003] A PID controller is a feedback controller that uses a combination of proportional, integral, and derivative control strategies to adjust the system output and achieve the control objective. The proportional part adjusts the control quantity based on the current error value, the integral part eliminates deviation by accumulating the error, and the derivative part predicts future trends based on the rate of change of error, improving the system's dynamic response. In many cases, a PI controller is used instead of a PID controller because the derivative term is more sensitive to system noise, easily amplifying noise and leading to control instability; moreover, PI controllers are simpler than PID controllers and are easier to debug and implement.

[0004] In modern power systems, renewable energy sources such as wind and solar power are being integrated into the grid in large quantities. The proportion of distributed generators that rely on power electronics for energy conversion is steadily increasing, transforming traditional power systems into highly penetrated renewable energy networks. However, due to the lack of inherent inertia of rotating machinery, power electronic devices offer limited transient support to the grid, especially during voltage fluctuations or faults. This lack of inertia leads to grid frequency and voltage instability.

[0005] To improve grid stability, researchers have extensively studied the dynamic support capabilities of grid-connected converters, which exhibit superior performance in grid support due to their active frequency and voltage control capabilities. Nevertheless, grid-connected converters remain prevalent in modern power systems and continue to dominate. In weaker grids, there is an urgent need to improve the reactive voltage control response speed of grid-connected converters to achieve faster voltage support and better overall support capabilities. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a reactive power control method and system for grid-connected converters. By establishing the relationship between the output voltage vector and output power of the grid-connected converter, the reactive power output and the q-axis current i of the grid-connected converter are determined. gq Positive correlation is achieved by using a PI controller to form feedback control to adjust the converter output voltage so that the converter output current is equal to the given current reference value, thereby controlling the reactive power output of the grid-connected converter. Based on PI control, a feedforward control link and a dynamic coefficient integral link are introduced to improve the response speed, further improving the reactive power voltage support speed.

[0007] In some implementations, the following technical solutions are adopted:

[0008] A reactive power control method for a grid-connected converter includes:

[0009] Calculate the q-axis reference current i of the grid converter using the reactive power reference value. gq_ref And through an integrator, the q-axis reference current i gq_ref To compensate for the error;

[0010] Cross-coupling compensation is performed on the d-axis output current and q-axis output current of the grid-type converter to obtain the q-axis current compensation current.

[0011] The q-axis reference current i gq_ref The current is compared with the q-axis current compensation current, and the error between the two is processed by a PI controller to generate the final q-axis control voltage u. sq ;

[0012] The q-axis control voltage u sq This is converted into the q-axis output current of the grid-connected converter, so that the q-axis output current is equal to the given current reference value, thereby realizing the reactive power control of the grid-connected converter.

[0013] Furthermore, when the reactive power error of the grid-connected converter is greater than a set threshold, the coefficient of the integral element is set to 0; when the reactive power error of the grid-connected converter is less than the set threshold, the coefficient of the integral element is set to not be 0.

[0014] Furthermore, when the reactive power error of the grid-connected converter is less than a set threshold, the coefficient of the integral element is set to increase as the error decreases.

[0015] Furthermore, the coefficients of the integral element are specifically set as follows:

[0016]

[0017] Where e represents the reactive power error of the grid-connected converter.

[0018] Furthermore, the q-axis reference current i of the grid-type converter is calculated using the reactive current reference value. gq_ref Specifically:

[0019]

[0020] Among them, Q ref Here, Q is the reactive power reference value, and T is the measured reactive power. c K and T represent the time constant and proportional parameter of the inertial element, respectively, due to the increased delay in the issuance of the simulated reactive power command. Q K is the time constant for reactive power detection filtering.i The coefficients of the integral element.

[0021] Furthermore, the q-axis current compensation current is specifically:

[0022] i gq_comp =ωL g i gd ;

[0023] Among them, i gd ω is the q-axis output current of the grid-connected converter; ω is the angular velocity of the dq rotating coordinate system; L g This refers to the output reactance of the converter.

[0024] Furthermore, the q-axis control voltage u sq Converted to the q-axis output current of the grid-connected converter, specifically:

[0025]

[0026] ε gq =u gq_filtered +u sq ;

[0027]

[0028] Among them, i gq To match the q-axis output current of the grid-connected converter, ε gq The q-axis output voltage and L obtained by comparison by the summer g R is the output reactance of the converter. g The resistance at the converter outlet, u gq_filtered T is the filtered q-axis voltage. u U is the voltage detection filter time constant. gq This is for outputting the q-axis voltage.

[0029] In other embodiments, the following technical solutions are adopted:

[0030] A reactive power control system for a grid-connected converter includes:

[0031] The reference current calculation module is used to calculate the q-axis reference current i of the grid-type converter based on the reactive power reference value. gq_ref And through an integrator, the q-axis reference current i gq_ref To compensate for the error;

[0032] The compensation current calculation module is used to perform cross-coupling compensation on the d-axis output current and q-axis output current of the grid-connected converter to obtain the q-axis current compensation current.

[0033] The control voltage generation module is used to generate the q-axis reference current i. gq_refThe current is compared with the q-axis current compensation current, and the error between the two is processed by a PI controller to generate the final q-axis control voltage u. sq ;

[0034] Output current conversion module, used to convert q-axis control voltage u sq This is converted into the q-axis output current of the grid-connected converter, so that the q-axis output current is equal to the given current reference value, thereby realizing the reactive power control of the grid-connected converter.

[0035] In other embodiments, the following technical solutions are adopted:

[0036] A terminal device includes a processor and a memory, wherein the processor is used to implement instructions; and the memory is used to store multiple instructions adapted to be loaded and executed by the processor for the reactive power control method of the grid-connected converter described above.

[0037] In other embodiments, the following technical solutions are adopted:

[0038] A computer-readable storage medium storing a plurality of instructions adapted for loading and execution by a processor of a terminal device of the above-described reactive power control method for a grid-connected converter.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] (1) This invention establishes a circuit model of a grid-connected converter, derives the circuit equation relating the converter output voltage vector to the reactive power output, and constructs a dual-loop control framework for reactive power control. It introduces a feedforward control loop, calculates the output current reference value using the reactive power reference value, and introduces an integral loop to compensate for calculation errors, thereby improving the response speed and thus improving the reactive voltage support speed.

[0041] (2) The present invention dynamically adjusts the coefficient of the integral link. When the reactive power error is large in the initial stage of optimized control, a time delay is set for the integrator so that it starts after a certain period of time. This can weaken the effect of the initial integral link and effectively reduce overshoot and adjustment time. When the reactive power error is small, the integral coefficient is increased and the integral coefficient is set to increase as the error decreases. This enables the system to eliminate steady-state error more effectively and improve the steady-state accuracy of the system.

[0042] (3) The method of the present invention improves the performance of the reactive power control system and helps to improve the speed of reactive power voltage support of grid-connected converters. The method of the present invention can not only be applied to the reactive power control structure design of grid-connected converters, but its analysis process and design principles can also play a corresponding role in other scenarios where PI control is applied, and it has a certain degree of universality.

[0043] Other features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0044] Figure 1 This is a circuit diagram of the grid-side converter and the power grid.

[0045] Figure 2 This is the three-phase circuit diagram of the grid-side converter;

[0046] Figure 3 This is a block diagram of the decoupling of the control system in an embodiment of the present invention;

[0047] Figure 4 This is a block diagram of reactive power output control in an embodiment of the present invention;

[0048] Figure 5 This is a system control block diagram with feedforward control added in an embodiment of the present invention;

[0049] Figure 6 This is a system control block diagram with the addition of delay integral in an embodiment of the present invention;

[0050] Figure 7 This is a system control block diagram with dynamic integration added in an embodiment of the present invention;

[0051] Figure 8 This is a comparison diagram of the step response of the method in this embodiment of the invention with other methods;

[0052] Figure 9 In order to be in Figure 8 A comparison of the step responses of each method after adding perturbations;

[0053] Figure 10 In order to be in Figure 8 Comparison of step responses after changing the integral coefficients based on the above;

[0054] Figure 11 This is a comparison of the step responses of a feedforward combined with a dynamic integral strategy and a feedforward combined with a fixed coefficient integral strategy. Detailed Implementation

[0055] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0056] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0057] Example 1

[0058] Combination Figure 1 The grid-side converter is a converter circuit composed of voltage-source three-phase full-bridge IGBTs. Through SPWM modulation, it can generate a three-phase AC voltage vector E at the converter ports. g .

[0059] Combination Figure 2 Given the three-phase circuit diagram of the grid-side converter, the three-phase circuit equations are as follows:

[0060]

[0061] i ga +i gb +i gc =0;

[0062] Among them, e ga e gb e gc These are the three-phase voltages directly output by the converter, i ga i gb i gc These are the three-phase current values ​​on the output line, u ga u gb u gc These are the three-phase voltage values ​​at the grid connection point, R g L is the resistance at the converter outlet. g This refers to the output reactance of the converter.

[0063] Based on the coordinate transformation relationships of abc-αβ0 and αβ0-dq0, the circuit equations are transformed to the dq coordinate system, and the matrix is ​​expanded. Ignoring the zero-sequence components, the following system of equations can be obtained:

[0064]

[0065] Among them, e gd e gq These are the d-axis and q-axis voltages directly output from the converter, i gd i gq These are the d-axis and q-axis currents on the output line, respectively, u gd u gqThese are the d-axis and q-axis voltages at the grid connection point, respectively.

[0066] In converter control, the magnitude of power is expressed using instantaneous active and reactive power theory:

[0067]

[0068] Where P represents active power and Q represents reactive power. Voltage amplitude, φ is the current amplitude. u_i The angle by which voltage leads current, u d For the d-axis voltage, u q Let i be the q-axis voltage. d Let i be the d-axis current. q This is the q-axis current.

[0069] A phase-locked loop is used to align the d-axis of the rotating coordinate system with the grid voltage vector U. g Overlap, at this time U g Only the d-axis component exists, while the q-axis component is 0. The instantaneous power output by the converter to the grid is:

[0070]

[0071] Based on the above analysis, it can be seen that the reactive power output is related to the q-axis current i. gq Positive correlation means that to control the reactive power output of the converter, it is necessary to control i. gq To achieve this, and i gq The rate of change is affected by the q-axis output voltage E of the grid-side converter. gq The effect is positively correlated. In other words, to control the q-axis current change, the q-axis output voltage of the grid-side converter should be adjusted. Since the dq-axis current is a DC current, a PI controller can be used to form feedback control to adjust the converter output voltage, thereby making the converter output current equal to a given current reference value.

[0072] Based on this, this embodiment discloses a reactive power control method for a grid-connected converter, which mainly includes the following process:

[0073] S101: Calculate the q-axis reference current i of the grid converter based on the reactive power reference value. gq_ref And through an integrator, the q-axis reference current i gq_ref To compensate for the error;

[0074] S102: Perform cross-coupling compensation on the d-axis output current and q-axis output current of the grid-type converter to obtain the q-axis current compensation current;

[0075] S103: Set the q-axis reference current i gq_refThe current is compared with the q-axis current compensation current, and the error between the two is processed by a PI controller to generate the final q-axis control voltage u. sq ;

[0076] S104: Set the q-axis control voltage u sq This is converted into the q-axis output current of the grid-connected converter, so that the q-axis output current is equal to the given current reference value, thereby realizing the reactive power control of the grid-connected converter.

[0077] The specific implementation process of the method in this embodiment is described below:

[0078] Combination Figure 3 There is a cross-coupling relationship between the current and the d-axis components of the grid converter, which is difficult to handle in subsequent calculations. Therefore, U is fed forward into the feedback loop of the inner current loop. g and ωL g i g The signal cancels out these two input quantities in the actual circuit.

[0079] First, reactive power filtering and error calculation are performed:

[0080]

[0081] Among them, e Q The reactive power error is the error between the reference value and the actual output value of reactive power, Q. ref Q is the reactive power reference value. filtered The filtered output reactive power, T Q This is the time constant for reactive power detection filtering.

[0082] Reference current generation (integral control and PI controller)

[0083] reactive power error e Q A reference current i is generated by an integrator and a PI controller. gq_ref DC voltage error (u dc_ref -u dc i is generated through a PI controller gd_ref :

[0084]

[0085] Among them, i gd_ref i gq_ref These are the reference values ​​for the d-axis and q-axis output currents of the grid-connected converter, respectively; u dc_ref The reference value for DC voltage, u dc To measure the DC voltage, K p K i These are the proportional and integral parameters of the active outer loop PI controller, K′. pK′ i These are the proportional and integral parameters of the reactive power outer loop PI controller.

[0086] Using inductor ωL g to i gq and i gd Perform cross-coupling compensation:

[0087]

[0088] Among them, i gd_comp i gq_comp These are the d-axis current compensation current and the q-axis current compensation current, respectively.

[0089] The reference current is compared with the compensation current, and the error is processed by a PI controller to generate the final control voltage.

[0090]

[0091] Among them, u sd u sq These are the d-axis control voltage and the q-axis control voltage, respectively.

[0092] Perform voltage filtering and error calculation:

[0093]

[0094] Among them, u gq_filtered u gd_filtered The output voltages obtained by filtering the q and d axes are T, respectively. u ε is the voltage detection filter time constant. gq ε gd These are the q-axis and d-axis output voltages obtained by comparison using a summer, respectively.

[0095] Finally, the voltage control signal is converted into output current through a filter inductor circuit.

[0096]

[0097] After decoupling, the coupling terms between the d-axis and q-axis are eliminated, and the reactive power output is only related to the q-axis component. The simplified block diagram is as follows: Figure 4 As shown.

[0098] To improve the speed of reactive power support, this embodiment optimizes the above-mentioned reactive power control process. During the derivation, we noted that the reactive current reference value can be calculated from the reactive power reference value. Even if there are calculation errors, these errors can be compensated by designing an integral element. Therefore, the design method is to transform the PI controller into a combination of feedforward and integral elements. The specific control block diagram is as follows: Figure 5 As shown, the reactive current reference value Qref The reactive current reference value is obtained through feedforward calculation:

[0099] Increasing the integral coefficient can more effectively eliminate steady-state error, thereby improving the steady-state accuracy of the system. However, a large integral coefficient may cause excessive overshoot before the system reaches steady state. Therefore, this embodiment further introduces a delayed integration strategy, setting a time delay for the integrator at the signal input, so that it starts after a certain period of delay. This aims to weaken the effect of the initial integration stage, while strengthening the integration in the later stage to eliminate the static error of the system. Its control block diagram is as follows: Figure 6 As shown.

[0100] However, while the delayed integration strategy can effectively reduce overshoot and settling time, the duration of the delay is difficult to tune to a uniform expression for different systems, thus limiting the applicability of the strategy. Therefore, this embodiment further improves and optimizes the strategy by introducing a dynamic coefficient integration stage: In the initial stage of integration, when the error is large (the error is greater than the set threshold), the integrator does not function because of the delayed start of integration, i.e., the coefficient of integration is 0; when the error decreases (the error is less than the set threshold), the integrator starts, and at this time, the integral with a fixed coefficient can play a regulating role in the system.

[0101] Based on this, this embodiment further segments the integral coefficients, and adjusts the basis for segmentation from the time scale to the error amount. Due to the per-unit calculation method, when an error boundary is tuned, it is applicable to different systems and the tuning value can be flexibly adjusted.

[0102] When the initial error is large, the integral coefficient is set to 0, and only the feedforward control plays a role in the outer loop control. When the error decreases to a certain value, the integrator starts to work, and its coefficient increases as the error decreases, eventually eliminating the steady-state error.

[0103] As a specific example, combined with Figure 7 In this embodiment, when the error exceeds a set threshold, the integral coefficient is set to the following form: in, e This indicates the reactive power error compared to the grid-type converter.

[0104] This embodiment uses a reactive power control method similar to that of a grid converter. Based on PI control, it introduces a feedforward control loop and a dynamic coefficient integral loop to improve the response speed and increase the support speed of reactive voltage.

[0105] The reactive power control method of the grid converter in this embodiment will be experimentally verified below.

[0106] The method of this embodiment is applied to the reactive power outer loop control system of the grid-connected control system. Given a unit step input, the reactive power output waveform under different methods is examined, and the overshoot and rise time of the output waveform under different control methods are compared.

[0107] Figure 8 The step response performance of the feedforward combined with integral control method in this embodiment is compared with that of traditional PI control only, feedforward control combined with PI control, and feedforward control only.

[0108] In the theoretical derivation, we note that the above strategy is based on u gd Based on the condition that Q = 0, the relationship between reactive power output and reactive current is simplified as follows: Q = -u gd i gq ; when u gq If the value is not equal to 0, the above relationship is no longer satisfied. In this case, the amount obtained by reactive power feedforward is not the current required by the q-axis, and an error occurs.

[0109] Suppose that during a certain reactive power regulation, due to the presence of disturbances, the relationship between reactive power output and reactive current is: Q = -0.8u gd i gq However, the coefficients in the feedforward control were not changed (when only the feedforward strategy is used, the control side is unknown to the disturbance), and the simulation results at this time are as follows. Figure 9 As shown.

[0110] This indicates that although feedforward control has a good adjustment effect, for systems that rely solely on feedforward control, when subjected to disturbances, the lack of an integral element to eliminate steady-state errors will lead to significant deviations in the output.

[0111] During the adjustment process, various parameters in the control loop can be adjusted to achieve better adjustment results. Setting the integral coefficient is a crucial step. Adjusting the integral parameters of the outer loop in simulation allows observation of their impact on the system response performance, such as... Figure 10 As shown in (a), (b), and (c); Figure 10 In the diagram, (a), (b), and (c) represent the reactive power output waveforms obtained after the integral coefficient is reduced by 50%, increased by 1, and increased by 2, respectively. Compare these waveforms with... Figure 8 By comparing the waveforms, it can be found that increasing the integral coefficient can make the system eliminate steady-state error more effectively, thereby improving the steady-state accuracy of the system. However, a large integral coefficient may cause the system to have excessive overshoot before reaching steady state.

[0112] The step response performance of the feedforward control combined with the dynamic integral coefficient strategy in this embodiment is compared with that of the feedforward control combined with the fixed coefficient integral strategy. Figure 11As shown, compared to feedforward control combined with a fixed integral coefficient integrator, the feedforward control combined with a dynamic integral coefficient strategy in this embodiment has lower overshoot and shorter rise time. Therefore, the actual reactive power output can track the reference value more quickly, thereby improving the reactive power voltage support speed.

[0113] Example 2

[0114] In one or more embodiments, a reactive power control system for a grid-connected converter is disclosed, comprising:

[0115] The reference current calculation module is used to calculate the q-axis reference current i of the grid-type converter based on the reactive power reference value. gq_ref And through an integrator, the q-axis reference current i gq_ref To compensate for the error;

[0116] The compensation current calculation module is used to perform cross-coupling compensation on the d-axis output current and q-axis output current of the grid-connected converter to obtain the q-axis current compensation current.

[0117] The control voltage generation module is used to generate the q-axis reference current i. gq_ref The current is compared with the q-axis current compensation current, and the error between the two is processed by a PI controller to generate the final q-axis control voltage u. sq ;

[0118] Output current conversion module, used to convert q-axis control voltage u sq This is converted into the q-axis output current of the grid-connected converter, so that the q-axis output current is equal to the given current reference value, thereby realizing the reactive power control of the grid-connected converter.

[0119] The specific implementation methods of the above modules are the same as those in Example 1, and will not be described in detail again.

[0120] Example 3

[0121] In one or more embodiments, a terminal device is disclosed, comprising a processor and a memory, wherein the processor is used to implement instructions; and the memory is used to store multiple instructions adapted to be loaded by the processor and executed by the processor to perform the reactive power control method for the grid-connected converter described in Embodiment 1.

[0122] It should be understood that in this embodiment, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc.

[0123] Memory may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of memory may also include non-volatile random access memory. For example, memory may also store information about the device type.

[0124] In the implementation process, each step of the above method can be completed by the integrated logic circuits in the processor hardware or by software instructions.

[0125] Example 4

[0126] In one or more embodiments, a computer-readable storage medium is disclosed, wherein a plurality of instructions are stored, the instructions being adapted to be loaded by a processor of a terminal device and executed by the reactive power control method for a grid-connected converter as described in Embodiment 1.

[0127] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A reactive power control method for a grid-connected converter, characterized in that, include: Calculation based on reactive power reference value and grid converter q Shaft reference current i gq_ref And through the points system q Shaft reference current i gq_ref The error is compensated; the calculation of reactive current reference value and the grid converter are performed. q Shaft reference current i gq_ref Specifically: ； in, Here, Q is the reactive power reference value, and Q is the measured reactive power. , These represent the time constant and proportional parameter of the inertial element, respectively, due to the increased delay in simulating the reactive power command issuance. The time constant for reactive power detection filtering. The coefficients of the integral element; The integration process q Shaft reference current i gq_ref The error compensation specifically involves: setting a time delay for the integrator at signal input; when the reactive power error of the grid-connected converter exceeds a set threshold, setting the coefficient of the integrator to 0; when the reactive power error of the grid-connected converter is less than the set threshold, setting the coefficient of the integrator to be non-zero and increasing as the error decreases. In this case, the coefficient of the integrator is specifically: ;in, To compensate for reactive power error in grid-connected converters; For grid-type converters d Shaft output current and q Cross-coupling compensation is applied to the shaft output current to obtain... q Shaft current compensation current; q-axis reference current i gq_ref and q The shaft current compensation current is compared, and the error between the two is processed by a PI controller to generate the final value. q Shaft control voltage ; Will q Shaft control voltage Convert to grid-type converter q Shaft output current, so that q The shaft output current is equal to the given current reference value, thereby realizing reactive power control of the grid-connected converter.

2. The reactive power control method for a grid-connected converter as described in claim 1, characterized in that, The q The shaft current compensation current is specifically: ； in, For grid-type converters q Shaft output current; for dq Angular velocity of rotating coordinate system This refers to the output reactance of the converter.

3. The reactive power control method for a grid-connected converter as described in claim 1, characterized in that, Will q Shaft control voltage Convert to grid-type converter q The shaft output current is as follows: ； ； ； in, For grid-type converters q Shaft output current, The result obtained by comparison using a summer q Shaft output voltage, For the converter output reactance, The resistance at the converter outlet. After filtering q shaft voltage, The voltage detection filter time constant is For output q Shaft voltage.

4. A reactive power control system for a grid-connected converter, characterized in that, include: The reference current calculation module is used to calculate the reactive power reference value for the grid-type converter. q Shaft reference current i gq_ref And through the points system q Shaft reference current i gq_ref The error is compensated; the calculation of reactive current reference value and the grid converter are performed. q Shaft reference current i gq_ref Specifically: ； in, Here, Q is the reactive power reference value, and Q is the measured reactive power. , These represent the time constant and proportional parameter of the inertial element, respectively, due to the increased delay in simulating the reactive power command issuance. The time constant for reactive power detection filtering. The coefficients of the integral element; The integration process q Shaft reference current i gq_ref The error compensation specifically involves: setting a time delay for the integrator at signal input; when the reactive power error of the grid-connected converter exceeds a set threshold, setting the coefficient of the integrator to 0; when the reactive power error of the grid-connected converter is less than the set threshold, setting the coefficient of the integrator to be non-zero and increasing as the error decreases. In this case, the coefficient of the integrator is specifically: ;in, To compensate for reactive power error in grid-connected converters; The compensation current calculation module is used for grid-connected converters. d Shaft output current and q Cross-coupling compensation is applied to the shaft output current to obtain... q Shaft current compensation current; The control voltage generation module is used to generate the q-axis reference current. i gq_ref and q The shaft current compensation current is compared, and the error between the two is processed by a PI controller to generate the final value. q Shaft control voltage ; Output current conversion module, used to convert... q Shaft control voltage Convert to grid-type converter q Shaft output current, so that q The shaft output current is equal to the given current reference value, thereby realizing reactive power control of the grid-connected converter.

5. A terminal device comprising a processor and a memory, wherein the processor is used to implement instructions; and the memory is used to store multiple instructions, characterized in that, The instructions are adapted to be loaded by a processor and executed by the reactive power control method for a grid-connected converter as described in any one of claims 1-3.

6. A computer-readable storage medium storing a plurality of instructions, characterized in that, The instructions are adapted to be loaded by the processor of the terminal device and executed by the reactive power control method of the grid-connected converter according to any one of claims 1-3.

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