Grid-connected inverter control mode switching method, device, equipment, medium and product

Abstract

The embodiment of the invention provides a grid-connected inverter control mode switching method and device, equipment, a medium and a product, and is applied to the technical field of electrical control. The method comprises the following steps: acquiring a control mode switching signal of the grid-connected inverter, and determining a switching direction of a control mode based on the switching signal; when the switching direction indicates that the current control mode is switched from the GFL mode to the GFM mode, setting an initial value of an integrator of a power synchronization loop of the GFM mode as a phase angle value of a phase-locked loop corresponding to the GFL mode; switching the control mode from the GFL mode to the GFM mode based on a first preset path and a step-by-step switching mode; when the switching direction indicates that the current control mode is switched from the GFM mode to the GFL mode, acquiring a power steady-state output value of the GFM mode, and setting a power reference value of the GFL mode as the power steady-state output value; and switching the control mode from the GFM mode to the GFL mode based on the second preset path and the step-by-step switching mode. The technical effect of improving the control mode switching fluency is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of power system operation control, and in particular to a method, device, equipment, medium and product for switching control modes of a grid-connected inverter. Background Art

[0002] With the increasing adoption of renewable energy in power grids, research on renewable energy output stability is increasing. Due to the randomness and intermittent nature of renewable energy output, the transition from traditional power systems to power electronics requires continuous adjustment of grid-connected inverter control modes to cope with changing external grid conditions and ensure high reliability.

[0003] In the prior art, a control mode switching method for a grid-connected inverter is to trigger the switching of the control mode according to the change of the grid strength, and simultaneously utilize an integrator, voltage synchronization, and a state follower to realize the switching of the grid-connected inverter.

[0004] Since the control mode switching in the prior art lacks consideration for smooth transition, the prior art has a technical problem of low smoothness in the control mode switching. Summary of the Invention

[0005] The embodiments of the present application provide a method, apparatus, device, medium, and product for switching the control mode of a grid-connected inverter, so as to achieve the technical effect of improving the smoothness of the control mode switching.

[0006] In a first aspect, an embodiment of the present application provides a method for switching a control mode of a grid-connected inverter, comprising:

[0007] Obtaining a control mode switching signal of the grid-connected inverter, and determining a switching direction of the control mode based on the switching signal;

[0008] When the current control mode is the GFL mode and the switching direction indicates that the current control mode is switched from the GFL mode to the GFM mode, obtaining a phase angle value of a phase-locked loop corresponding to the GFL mode, setting an initial value of an integrator of a power synchronization loop in the GFM mode to the phase angle value; and switching the control mode from the GFL mode to the GFM mode based on a first preset path and a step-by-step switching manner;

[0009] When the current control mode is GFM and the switching direction indicates that the current control mode is switched from the GFM mode to the GFL mode, obtaining a steady-state power output value of the GFM mode, setting a power reference value of the GFL mode to the steady-state power output value; and switching the control mode from the GFM mode to the GFL mode based on a second preset path and a step-by-step switching manner;

[0010] Among them, in the GFL mode and the GFM mode, the control structure inside the current loop is consistent.

[0011] In a possible implementation, based on the first preset path and in a step-by-step switching manner, switching the control mode from the GFL mode to the GFM mode includes:

[0012] When the control enable switch of the excitation loop of the grid-connected inverter is in the open state, the signal selection switch of the grid synchronization module in the grid-connected inverter is switched from the output end of the phase-locked loop to the output end of the power synchronization loop;

[0013] Switch the reference source selection switch of the current loop in the grid-connected inverter from the power loop output end to the voltage loop output end;

[0014] When the grid-connected inverter is in a stable state, the control enable switch of the excitation loop of the grid-connected inverter is switched to a closed state.

[0015] In one possible implementation, obtaining a steady-state power output value in the GFM mode, setting a power reference value in the GFL mode as the steady-state power output value; and switching the control mode from the GFM mode to the GFL mode based on a second preset path and a step-by-step switching manner, includes:

[0016] Obtaining the active power output by the grid-connected inverter within a first preset time period, and calculating an average value of the active power;

[0017] Obtaining the real-time voltage amplitude of the grid-connected inverter, and calculating the reactive power output value of the grid-connected inverter based on a preset reactive power reference value and the real-time voltage amplitude;

[0018] Determine the steady-state power output value based on the active power mean value and the reactive power output value;

[0019] Set the power reference value of the GFL mode to the power steady-state output value;

[0020] Based on the second preset path and the step-by-step switching method, the control mode is switched from the GFM mode to the GFL mode.

[0021] In a possible implementation, switching the control mode from the GFM mode to the GFL mode based on the second preset path and the step-by-step switching method includes:

[0022] When the power loop of the grid-connected inverter is in an open-loop holding mode, switching a reference source selection switch of the current loop in the grid-connected inverter from the voltage loop output end to the power loop output end;

[0023] Switch the signal selection switch of the grid synchronization module in the grid-connected inverter from the output end of the power synchronization loop to the output end of the phase-locked loop;

[0024] When the grid-connected inverter is in a stable state, the power loop is switched from the open-loop holding mode to the closed-loop regulation mode.

[0025] In one possible implementation, the method further includes:

[0026] Obtaining the operating status data of the target power grid corresponding to the grid-connected inverter;

[0027] When the operating status data meets the first preset condition and the control mode of the grid-connected inverter is the GFL mode, switching the control mode of the grid-connected inverter to the GFM mode;

[0028] The first preset condition refers to that the voltage value in the operating status data is continuously lower than the first preset threshold value within the second preset time period, and the fluctuation range of the frequency value in the operating status data exceeds the preset range.

[0029] In one possible implementation, the method further includes:

[0030] When the operating status data meets the second preset condition and the control mode of the grid-connected inverter is the GFM mode, switching the control mode of the grid-connected inverter to the GFL mode;

[0031] The second preset condition refers to that the voltage harmonic rate in the operating status data is less than a second preset threshold, and the change value of the grid impedance value in the operating status data exceeds a third preset threshold.

[0032] In a second aspect, an embodiment of the present application provides a control mode switching device for a grid-connected inverter, comprising:

[0033] An acquisition module, configured to acquire a control mode switching signal of the grid-connected inverter and determine a switching direction of the control mode based on the switching signal;

[0034] a first processing module configured to, when the current control mode is the GFL mode and the switching direction indicates that the current control mode is switched from the GFL mode to the GFM mode, obtain a phase angle value of a phase-locked loop corresponding to the GFL mode, set an initial value of an integrator of a power synchronization loop in the GFM mode to the phase angle value; and switch the control mode from the GFL mode to the GFM mode based on a first preset path and a step-by-step switching method;

[0035] a second processing module, configured to, when the current control mode is GFM and the switching direction indicates that the current control mode is switched from the GFM mode to the GFL mode, obtain a steady-state power output value of the GFM mode, set a power reference value of the GFL mode to the steady-state power output value; and switch the control mode from the GFM mode to the GFL mode based on a second preset path and a step-by-step switching manner;

[0036] Among them, in the GFL mode and the GFM mode, the control structure inside the current loop is consistent.

[0037] In a possible implementation, the first processing module is further configured to:

[0038] When the control enable switch of the excitation loop of the grid-connected inverter is in the open state, the signal selection switch of the grid synchronization module in the grid-connected inverter is switched from the output end of the phase-locked loop to the output end of the power synchronization loop;

[0039] Switch the reference source selection switch of the current loop in the grid-connected inverter from the power loop output end to the voltage loop output end;

[0040] When the grid-connected inverter is in a stable state, the control enable switch of the excitation loop of the grid-connected inverter is switched to a closed state.

[0041] In a possible implementation manner, the second processing module is further configured to:

[0042] Obtaining the active power output by the grid-connected inverter within a first preset time period, and calculating an average value of the active power;

[0043] Obtaining the real-time voltage amplitude of the grid-connected inverter, and calculating the reactive power output value of the grid-connected inverter based on a preset reactive power reference value and the real-time voltage amplitude;

[0044] Determine the steady-state power output value based on the active power mean value and the reactive power output value;

[0045] Set the power reference value of the GFL mode to the power steady-state output value;

[0046] Based on the second preset path and the step-by-step switching method, the control mode is switched from the GFM mode to the GFL mode.

[0047] In a possible implementation, the second processing module is further configured to:

[0048] When the power loop of the grid-connected inverter is in an open-loop holding mode, switching a reference source selection switch of the current loop in the grid-connected inverter from the voltage loop output end to the power loop output end;

[0049] Switch the signal selection switch of the grid synchronization module in the grid-connected inverter from the output end of the power synchronization loop to the output end of the phase-locked loop;

[0050] When the grid-connected inverter is in a stable state, the power loop is switched from the open-loop holding mode to the closed-loop regulation mode.

[0051] In a possible implementation, the device further includes a third processing module, configured to:

[0052] Obtaining the operating status data of the target power grid corresponding to the grid-connected inverter;

[0053] When the operating status data meets the first preset condition and the control mode of the grid-connected inverter is the GFL mode, switching the control mode of the grid-connected inverter to the GFM mode;

[0054] The first preset condition refers to that the voltage value in the operating status data is continuously lower than the first preset threshold value within the second preset time period, and the fluctuation range of the frequency value in the operating status data exceeds the preset range.

[0055] In a possible implementation, the third processing module is further configured to:

[0056] When the operating status data meets the second preset condition and the control mode of the grid-connected inverter is the GFM mode, switching the control mode of the grid-connected inverter to the GFL mode;

[0057] The second preset condition refers to that the voltage harmonic rate in the operating status data is less than a second preset threshold, and the change value of the grid impedance value in the operating status data exceeds a third preset threshold.

[0058] In a third aspect, an embodiment of the present application provides an electronic device, comprising: a memory, a processor;

[0059] Memory stores computer-executable instructions;

[0060] The processor executes the computer-executable instructions stored in the memory, so that the processor executes the above first aspect and various possible implementations of the first aspect.

[0061] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement the above-mentioned first aspect and various possible implementation methods of the first aspect.

[0062] In a fifth aspect, an embodiment of the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the above first aspect and various possible implementation methods of the first aspect.

[0063] The embodiments of the present application provide a method, apparatus, device, medium, and product for switching the control mode of a grid-connected inverter. The method determines the control mode switching direction of the grid-connected inverter by obtaining a control mode switching signal of the grid-connected inverter; when the current control mode is the GFL mode, if the switching direction indicates switching from the GFL mode to the GFM mode, it is necessary to obtain a phase angle value of a phase-locked loop in the GFL mode, use the phase angle value as the initial value of an integrator of a power synchronization loop in the GFM mode, and switch the control mode from the GFL mode to the GFM mode based on a first preset path and a step-by-step switching method; when the current control mode is the GFM mode and the switching direction indicates switching from the GFM mode to the GFL, it is necessary to obtain a steady-state power output value in the GFM mode, use the steady-state power output value as a power reference value for the GFL mode, and simultaneously switch the control mode from the GFM mode to the GFL mode based on a second preset path and a step-by-step switching method. Compared with the prior art, the present application adopts a step-by-step switching method during the control mode switching process, avoiding the phase mutation problem caused by the smooth switching of the control mode. At the same time, when switching from the GFM mode to the GFL mode, the steady-state value of the GFM mode is used as the power reference value of the GFL mode to avoid reactive step-over during the switching process. At the same time, the same current loop internal control structure is used in the two modes to eliminate the influence of the disturbance source, thereby achieving the technical effect of improving the smoothness of the control mode switching. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0065] Figure 1 Schematic diagram of the process of switching the control mode of the grid-connected inverter provided in this application Figure 1 ;

[0066] Figure 2 Schematic diagram of the process of switching the control mode of the grid-connected inverter provided in this application Figure 2 ;

[0067] Figure 3 A schematic diagram of the grid-connected inverter circuit topology provided in this application;

[0068] Figure 4 Schematic diagram of seamless switching of control modes of the grid-connected inverter provided in this application;

[0069] Figure 5 A flow chart of seamless switching of control modes for the grid-connected inverter provided in this application;

[0070] Figure 6 A voltage and current comparison diagram of the grid-connected inverter provided in this application before and after adopting the seamless switching method;

[0071] Figure 7 A schematic diagram of the structure of the control mode switching device for the grid-connected inverter provided in this application;

[0072] Figure 8 This is a schematic diagram of the structure of the electronic device provided in this application.

[0073] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0074] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0075] First, let’s explain the terms involved in this application:

[0076] Grid-Following (GFL): refers to an inverter control mode that depends on the amplitude, frequency, and phase of the grid voltage. It requires real-time tracking of the grid phase through a phase-locked loop (PLL) to adjust the active and reactive power injected into the grid.

[0077] Grid-Forming (GFM): refers to an inverter control mode that can autonomously establish voltage and frequency to simulate the characteristics of a synchronous generator. This mode does not require any calculations and can directly generate a voltage reference signal through an internal algorithm. Its purpose is to regulate voltage amplitude and frequency and provide inertial support and short-circuit capacity.

[0078] Grid-connected inverters: Power electronic devices used to convert direct current (DC) to alternating current (AC) and connect it to the public grid. The DC power can be generated by photovoltaics or energy storage batteries. Their core mission is to ensure grid-compatible energy transmission.

[0079] In the prior art, when switching the control mode of a grid-connected inverter, the method adopted is: using replacement switching control to establish switching criteria for grid-following and grid-forming control according to the strength of the grid; and using an integrator, voltage and synchronization, and a state follower to realize the switching of the grid-connected inverter.

[0080] However, in the prior art, when switching, the state tracking method is used to force the current reference value to follow each other between the two modes, and the state tracker needs to be continuously run; and when switching between the following and building control modes, the transition is performed using the value obtained by strong following, resulting in the existence of phase angle jumps and waveform distortion problems, which leads to the technical problem of low smoothness of control mode switching in the prior art.

[0081] In response to the above technical problems, the present application proposes the following technical concepts: when a control mode switching signal of a grid-connected inverter is obtained, the control mode switching direction of the grid-connected inverter is determined based on the switching signal; when the switching direction indicates that the control mode is switched from the grid-following type to the grid-forming type, the phase angle value of the phase-locked loop in the grid-following type mode needs to be obtained, and the phase angle value is used as the initial value of the integrator of the power synchronization loop in the grid-forming type mode; at the same time, the switching from the grid-following type to the grid-forming type is achieved based on a first preset path and a step-by-step switching method; when the switching direction indicates that the control mode is switched from the grid-forming type to the grid-following type, the steady-state power output value in the grid-forming type mode needs to be obtained, and the value is used as the power reference value in the grid-following type mode, and at the same time, the mode switching is achieved by using a step-by-step switching method in combination with a second preset path. Compared with the prior art, the present application achieves seamless switching of the control mode by obtaining parameter values ​​and following the assignment when switching the control mode, avoiding the phase angle conditions and waveform distortion problems that exist in the process of switching the control mode, thereby achieving the technical effect of improving the smoothness of the control mode switching.

[0082] The following specific embodiments describe in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0083] Figure 1 Schematic diagram of the process of switching the control mode of the grid-connected inverter provided in this application Figure 1 ,like Figure 1 As shown, the method includes:

[0084] S101 : Acquire a control mode switching signal of a grid-connected inverter, and determine a switching direction of the control mode based on the switching signal.

[0085] In this step, the control mode switching signal for the grid-connected inverter is issued by an external controller, and the issuance of the switching signal is related to the grid status. Real-time monitoring can be used to obtain the operating status data of the target grid to which the grid-connected inverter is connected, as well as the operating status data of the grid-connected inverter itself. Based on the corresponding operating status data of the target grid and the grid-connected inverter, it is determined whether there are data mutations or faults in the target grid and the grid-connected inverter, thereby determining whether a control mode switch needs to be triggered.

[0086] Exemplarily, one possible way to determine the switching direction is:

[0087] S1011. Use sensors or monitoring systems to obtain operating status data of the target power grid, including but not limited to voltage data, current data, and frequency data; and obtain output parameters and status information of the grid-connected inverter.

[0088] S1012: Process the operating status data of the target power grid, the output parameters of the grid-connected inverter, and the status information to obtain stable data after processing.

[0089] S1013 : Generate a control mode switching signal based on the stable data and preset determination conditions.

[0090] In this step, the preset judgment conditions may be: voltage exceeding a set range, load change, target grid fault, and black start caused by a fault.

[0091] S1014: Determine the control mode to be switched to based on the switching signal, and generate a switching direction in combination with the current control mode of the grid-connected inverter.

[0092] It should be noted that the control mode switching method caused by the black start in this step is as follows Figure 2 Further explanation is given in the embodiment shown and no redundant description is given here.

[0093] S102. When the current control mode is the grid-following GFL mode and the switching direction indicates that the current control mode is switched from the GFL mode to the grid-forming GFM mode, obtain a phase angle value of a phase-locked loop corresponding to the GFL mode, set an initial value of an integrator of a power synchronization loop of the GFM mode to the phase angle value; and switch the control mode from the GFL mode to the GFM mode based on a first preset path and a step-by-step switching method.

[0094] It should be noted that in this embodiment, the control structure of the current loop used in the GFL mode and the GFM mode is the same. The GFL mode consists of a phase-locked loop, a power loop, and a current loop, while the GFM mode consists of a power synchronization loop, an excitation loop, a voltage loop, and a current loop.

[0095] In this step, before the step-by-step switching, the initial value of the integrator of the power synchronization loop in the GFM mode needs to be set. The specific setting method is:

[0096] a1. When it is determined that the switching direction indicates switching from the GFL mode to the GFM mode, a phase angle value of the phase-locked loop in the current control mode is obtained.

[0097] a2. Set the initial value of the integrator of the power synchronization loop in the GFM mode to the phase angle value.

[0098] The purpose of this step is to initialize the phase angle of the GFM mode virtual synchronizer to the phase angle currently locked by the phase-locked loop, thereby ensuring phase continuity and avoiding phase jumps during switching. The GFM mode virtual synchronizer refers to the integrator of the power synchronization loop.

[0099] It should be noted that the purpose of the power synchronization loop in the GFM mode is to simulate the rotor motion equation of the synchronous generator, adjust the frequency and phase of the grid-connected inverter output through the active power deviation, and provide inertia and damping support. The power synchronization loop is expressed using the swing equation as shown in Formula 1:

[0100]

[0101] Among them, J refers to the virtual quantity, D refers to the damping coefficient, Refers to the angular frequency output by the grid-connected inverter; Refers to the angular frequency of the target grid corresponding to the grid-connected inverter; Refers to the phase angle of the grid-connected inverter output; Pref refers to the active power reference value, and Pe refers to the actual active power value; dωvsg / dt and dθvsg / dt are the differential of the grid-connected inverter angular frequency and the differential of the grid-connected inverter phase angle, respectively.

[0102] Optionally, a possible implementation of switching the control mode from the GFL mode to the GFM mode is:

[0103] S1021. When the control enable switch of the excitation loop of the grid-connected inverter is in an on state, switch the signal selection switch of the grid synchronization module in the grid-connected inverter from the output end of the phase-locked loop to the output end of the power synchronization loop.

[0104] Before switching, first ensure that the excitation loop is inactive, meaning its control enable switch is on. Then, switch the grid synchronization signal from the phase-locked loop output to the power synchronization loop output. The grid synchronization module provides the phase angle. In GFL mode, the phase angle comes from the phase-locked loop, while in GFM mode, the phase angle comes from the power synchronization loop. Different phase angle sources are selected by switching the grid synchronization module's signal selection switch.

[0105] S1022. Switch the reference source selection switch of the current loop in the grid-connected inverter from the power loop output end to the voltage loop output end.

[0106] In this step, the purpose of switching the reference source selection switch is to switch the reference source of the current loop from the power loop output to the voltage loop output, where the power loop output refers to the current reference value generated by the power loop in the GFL mode, and the voltage loop output refers to the current reference value generated by the voltage loop in the GFM mode.

[0107] The calculation method of the current reference value output by the power loop in the GFL mode is shown in Formula 2:

[0108]

[0109] Among them, k PPQ and k iPQ are the proportional coefficient and integral coefficient of the proportional-integral controller of the power loop respectively; P ref and Q ref P is the reference value of active power and reactive power output by the grid-connected inverter; e and Q e are respectively the actual output active power and reactive power of the grid-connected inverter; i* GFLd and i* GFLq where is the d-axis and q-axis reference values ​​of the power loop output in GFL mode, and s is the Laplace transform operator. This formula converts the error between the reference power value and the actual power value into a current reference value for current loop tracking control.

[0110] In order to track the benchmark set by the power loop, it is necessary to use the current loop to adjust the current of the grid-connected inverter. The relationship between the output of the current loop corresponding to the current loop and the current reference value calculated by formula 2 is shown in formula 3:

[0111]

[0112] Among them, k Pc and k ic are the proportional coefficient and integral coefficient corresponding to the proportional-integral controller of the current loop; i d and i qis the output current of the grid-connected inverter side, ω g is the target grid angular frequency; L f is the filter inductor; u Pccd and u Pccq are the d-axis and q-axis components of the grid-connected point voltage respectively; u d and u q Refers to the voltage d-axis and q-axis reference values ​​output by the current loop; i* GFLd and i* GFLq where is the d-axis and q-axis reference values ​​of the power loop current in GFL mode; s is the Laplace transform operator. The grid connection point refers to the common connection point of the grid-connected inverter, which is used to connect to the external public grid.

[0113] Accordingly, in GFM mode, the reference source of the current loop is the output of the voltage loop. Accordingly, in GFM mode, the current reference value output by the voltage loop is calculated as shown in Formula 4:

[0114]

[0115] Among them, i dref and i qref k is the output current reference value of the grid-connected inverter side; Pu and k iu are the proportional coefficient and integral coefficient corresponding to the proportional-integral controller of the voltage loop; u Pccdref is the reference value of the d-axis component of the grid-connected point voltage, and the reference value of the q-axis component is 0; C f is the filter capacitor; ω g is the target grid angular frequency; s is the Laplace transform operator, u Pccd and u Pccq The voltage loop generates a current reference value through a proportional-integral controller based on the error between the voltage reference value and the actual value, and transmits it to the current loop.

[0116] When calculating the current reference value output by the voltage loop in Formula 4, it is necessary to track the voltage amplitude reference value set by the excitation loop. The calculation method of the voltage amplitude reference value is shown in Formula 5:

[0117]

[0118] Among them, k q and k u are the integral coefficient and the droop coefficient respectively; U N and u Pcc are the rated voltage amplitude and the grid connection point voltage amplitude, u Pccref is the reference value of the grid-connected point voltage amplitude; Q ref and Q eare the reactive power reference value and actual value, respectively. The purpose of this formula is to achieve reactive power-voltage droop control through the integrator, so that the inverter can adjust the output voltage to maintain reactive power balance and voltage stability.

[0119] In order to track the reference set by the voltage loop, the current loop needs to be used to adjust the current of the grid-connected inverter. The relationship between the output of the current loop corresponding to the current loop and the current reference value calculated by formula 4 is shown in formula 6:

[0120]

[0121] Among them, i* GFMd =i dref and i* GFMq =i qref They are the d-axis and q-axis reference values ​​of the current output by the voltage loop in the GFM mode respectively; the explanations of the remaining parameters refer to Formula 3 and are not repeated here.

[0122] S1023. When the grid-connected inverter is in a stable state, switch the control enable switch of the excitation loop of the grid-connected inverter to a closed state.

[0123] In this step, switching the control enable switch of the excitation loop of the grid-connected inverter to a closed state refers to activating the excitation loop. The purpose of activating the excitation loop when the grid-connected inverter is in a stable state is to delay activation of the voltage droop control of the GFM mode.

[0124] For example, when the grid-connected inverter is in a stable state, the control enable switch of the excitation loop of the grid-connected inverter is switched to a closed state in the following manner:

[0125] b1. Obtain the operating status data of the target power grid corresponding to the grid-connected inverter.

[0126] b2. When the voltage fluctuation in the operating status data is less than 5%, the control enable switch of the excitation loop of the grid-connected inverter is switched to a closed state.

[0127] The purpose of this step is to activate the excitation ring in a stable state to avoid system failure caused by switching transient voltage shock.

[0128] S103. When the current control mode is the GFM mode and the switching direction indicates that the current control mode is switched from the GFM mode to the GFL mode, obtain a steady-state power output value of the GFM mode, set a power reference value of the GFL mode to the steady-state power output value; and switch the control mode from the GFM mode to the GFL mode based on a second preset path and a step-by-step switching manner.

[0129] In this step, in order to ensure that the steady-state operating point before and after the transition from GFM mode to GFL mode is consistent, the active power output and reactive power output of the GFL mode should be consistent with the active power output and reactive power output of the GFM mode in steady-state operation.

[0130] Optionally, a possible implementation of switching the control mode from the GFM mode to the GFL mode is:

[0131] S1031. Obtain the active power output by the grid-connected inverter within a first preset time period, and calculate an average value of the active power.

[0132] In this step, active power refers to the active power output in the GFM mode, and the average active power refers to the average active power output in the GFM mode in a steady state.

[0133] Exemplarily, the first preset time period refers to 5 unit time periods, sampling is performed for each unit time period to obtain five active power output values, and the average of the five active power output values ​​is calculated to obtain the active power average.

[0134] S1032: Obtain the real-time voltage amplitude of the grid-connected inverter, and calculate the reactive power output value of the grid-connected inverter based on the preset reactive power reference value and the real-time voltage amplitude.

[0135] In this step, due to the regulation of the excitation circuit corresponding to the excitation ring, during steady-state operation, the voltage and reactive power at the grid connection point show a drooping relationship, which is specifically expressed as shown in Formula 7:

[0136]

[0137] Among them, k u Refers to the droop coefficient of reactive power relative to voltage; Q ref Refers to the preset reactive power reference value; Q e Refers to the reactive power output value; U Pcc Refers to the real-time voltage amplitude; U N Refers to the rated voltage.

[0138] When the grid connection point voltage deviates from the rated grid voltage, the reactive power output value in GFM mode will not track the preset reactive power reference value in GFL mode. This will result in a difference in the steady-state operating point when transitioning from GFM to GFL mode. To avoid this problem, this step uses Equation 2 to calculate the steady-state value of reactive power output in GFM mode.

[0139] S1033. Determine a steady-state power output value based on the active power mean value and the reactive power output value.

[0140] In this step, the active power mean value and the reactive power output value are combined to obtain a steady-state power output value.

[0141] S1034: Set the power reference value of the GFL mode as the steady-state power output value.

[0142] In this step, the power reference value of the GFL mode is set to the steady-state power output value by setting the active power output value of the GFL mode to the active power mean value of the GFM mode; and setting the reactive power output value of the GFL mode to the reactive power output value of the GFM mode.

[0143] S1035 : Based on the second preset path and the step-by-step switching method, switch the control mode from the GFM mode to the GFL mode.

[0144] Alternatively, based on the second preset path and the step-by-step switching method, a possible implementation method of switching the control mode from the GFM mode to the GFL mode is:

[0145] A1. When the power loop of the grid-connected inverter is in an open-loop holding mode, the reference source selection switch of the current loop in the grid-connected inverter is switched from the voltage loop output end to the power loop output end.

[0146] In this step, when switching the control mode, it is necessary to first ensure that the power loop of the grid-connected inverter is in open-loop hold mode. This means that the power loop's integrator is frozen. This ensures that the operating point remains consistent before and after the control mode transition. Switching from the voltage loop output to the power loop output means switching the current loop's reference source from the voltage loop to the power loop.

[0147] A2. Switch the signal selection switch of the grid synchronization module in the grid-connected inverter from the output end of the power synchronization loop to the output end of the phase-locked loop.

[0148] In this step, the grid synchronization signal is switched from the power synchronization loop output to the phase-locked loop output. The grid synchronization module is responsible for providing the phase angle, and different phase angle sources are selected by switching the signal selection switch of the grid synchronization module. This is consistent with the switching purpose in step S1021.

[0149] A3. When the grid-connected inverter is in a stable state, switch the power loop from the open-loop holding mode to the closed-loop regulation mode.

[0150] In this step, after A1 and A2 are completed, the inverter still uses the power reference value corresponding to the open-loop holding mode to operate. When it is detected that the actual output power is stable within a certain range, the power loop can be switched to the closed-loop regulation mode.

[0151] Exemplarily, when it is detected that the difference between the actual output power and the power reference value corresponding to the open-loop holding mode is less than 3%, the power loop may be switched to the closed-loop regulation mode.

[0152] The purpose of this step is to activate the closed-loop control of the power loop after the system is stable, so that the grid-connected inverter completely enters the GFL mode.

[0153] An embodiment of the present application provides a method for switching a control mode of a grid-connected inverter. The method determines a control mode switching direction of the grid-connected inverter by acquiring a control mode switching signal of the grid-connected inverter. When the current control mode is the GFL mode, if the switching direction indicates switching from the GFL mode to the GFM mode, a phase angle value of a phase-locked loop in the GFL mode is acquired, the phase angle value is used as an initial value of an integrator of a power synchronization loop in the GFM mode, and the control mode is switched from the GFL mode to the GFM mode based on a first preset path and a step-by-step switching manner. When the current control mode is the GFM mode and the switching direction indicates switching from the GFM mode to the GFL mode, a steady-state power output value in the GFM mode is acquired, the steady-state power output value is used as a power reference value for the GFL mode, and the control mode is switched from the GFM mode to the GFL mode based on a second preset path and a step-by-step switching manner. Compared with the prior art, the present application adopts a step-by-step switching method during the control mode switching process, avoiding the phase mutation problem caused by the smooth switching of the control mode. At the same time, when switching from the GFM mode to the GFL mode, the steady-state value of the GFM mode is used as the power reference value of the GFL mode to avoid reactive step-over during the switching process. At the same time, the same current loop internal control structure is used in the two modes to eliminate the influence of the disturbance source, thereby achieving the technical effect of improving the smoothness of the control mode switching.

[0154] Figure 2 Schematic diagram of the process of switching the control mode of the grid-connected inverter provided in this application Figure 2 ,like Figure 2 As shown, the method includes:

[0155] S201: Acquire operating status data of a target power grid corresponding to a grid-connected inverter.

[0156] In this step, the target grid refers to the AC grid to which the grid-connected inverter is connected. Operational status data includes, but is not limited to: voltage, which refers to the voltage amplitude at the grid connection point; frequency, which refers to the fundamental frequency of the target grid; voltage harmonics, which refers to the total harmonic distortion; and grid impedance, which refers to the equivalent impedance of the grid.

[0157] For example, when collecting operating data, operating data of a time period is collected, and different sampling frequencies can be set for each type of operating data. For example, a sampling frequency of 10 kHz can be used when collecting voltage values, and a sampling frequency of once every 100 milliseconds can be used when collecting impedance.

[0158] S202: When the operating status data meets a first preset condition and the control mode of the grid-connected inverter is the GFL mode, switch the control mode of the grid-connected inverter to the GFM mode.

[0159] In this step, the first preset condition refers to that the voltage value in the operating status data is continuously lower than the first preset threshold value within the second preset time period, and the fluctuation range of the frequency value in the operating status data exceeds the preset range.

[0160] Exemplarily, the first preset threshold is set to 20% of the rated voltage of 380V, that is, 76V; the length of the second preset time period is 3 seconds; the preset range corresponding to the frequency fluctuation is -1 Hz to 1 Hz; when the voltage values ​​in the currently measured operating status data are all lower than 76V within 3 seconds, and the frequency value fluctuation exceeds 1 Hz or -1 Hz, it is determined that the first preset condition is met.

[0161] In this step, the purpose of the first preset condition is to ensure that the conventional GFL mode cannot operate due to the grid voltage in a black start scenario, and it is necessary to switch to GFM mode to maintain the normal operation of the grid-connected inverter. Black start scenarios refer to extremely weak grid conditions, islanding scenarios, or grid collapse scenarios.

[0162] It should be noted that when the switching is triggered here, when switching from the GFL mode to the GFM mode, the phase angle value used is the phase angle value of the phase-locked loop recorded last time.

[0163] S203 : When the operating status data meets a second preset condition and the control mode of the grid-connected inverter is the GFM mode, switch the control mode of the grid-connected inverter to the GFL mode.

[0164] In this step, the second preset condition refers to that the voltage harmonic rate in the operating status data is less than the second preset threshold, and the change value of the grid impedance value in the operating status data exceeds the third preset threshold.

[0165] Exemplarily, this step aims to switch from GFM mode to GFL mode when a sudden drop in grid impedance is detected or when the voltage harmonic component stabilizes. Specifically, the second preset threshold is set to 3%, and the third preset threshold is set to 50%. When the rate of change of the grid impedance is detected to be greater than 50% and the voltage harmonic component is less than 3%, the mode is switched from GFM mode to GFL mode. For the specific switching process, refer to step S103 of the above embodiment.

[0166] Figure 3 The schematic diagram of the grid-connected inverter circuit topology provided in this application is as follows: Figure 3 As shown, the grid-connected inverter includes: a voltage source inverter, an LC filter and a power grid.

[0167] In a voltage source inverter, u dc Refers to the DC bus voltage, which provides DC power input for the inverter; Q1, Q2, Q3, Q4, Q5, and Q6 refer to power semiconductor switches that convert DC power into AC power through high-frequency switching. ia, ib, and ic refer to the three-phase current output by the inverter.

[0168] In the LC filter, L f Refers to the filter inductor on the inverter side, which is used to suppress high-frequency harmonic current; C f Refers to filter capacitors, which are used to eliminate high-frequency harmonics, provide impedance paths, and reduce harmonics injected into the power grid.

[0169] U Pcca 、U Pccb 、U Pccc Refers to the real-time value of the grid voltage, which is used for the phase-locked loop synchronization control of the inverter; i ca 、i cb 、i cc Refers to the three-phase current after preliminary filtering, i ca 、i cb 、i cc Refers to the three-phase current that is ultimately injected into the grid; Zg refers to the line inductance on the grid side; PCC refers to the physical connection point between the inverter and the grid, i.e., the point of common connection.

[0170] Figure 4 The schematic diagram of seamless switching of the control mode of the grid-connected inverter provided in this application is based on Figure 3 The grid-connected inverter is shown in the following figure: Figure 4 As shown, the grid-connected inverter includes: a grid synchronization module, a power calculation module power loop, a current loop and an excitation loop.

[0171] The grid synchronization module includes a phase-locked loop and a power synchronization loop. The input of the phase-locked loop is the three-phase voltage u at the grid connection point. Pcca 、u Pccb 、u Pccc , output the phase angle value θ of the phase-locked loop Pll ; The input of the power synchronization loop is the active power reference value P ref Or the actual value P e , output phase angle value θ vsgThe signal selection switch of the grid synchronization module is used to switch between the phase-locked loop output terminal 1 and the power synchronization loop output terminal 2.

[0172] The input of the current loop is the current command output from the power loop or voltage loop. The current command can be the current d-axis and q-axis reference values ​​i* output by the power loop. GFLd and i* GFLq , or the current d-axis and q-axis reference values ​​i* output by the voltage loop GFMd and i* GFMq ; Output is voltage d-axis and q-axis reference value u d and u q The reference source selection switch of the current loop is used to switch between the power loop output terminal 1 and the voltage loop output terminal 2.

[0173] The input of the power loop is the reactive power reference value Q ref or Q e0 , and the actual value Q e and active power reference value P ref Or the actual value P e ; Output is the current d-axis and q-axis reference value i* GFLd and i* GFLq The power loop switch is used to switch between open-loop holding mode 3 and closed-loop regulation mode 4.

[0174] The input of the excitation ring is the reference value u of the d-axis component of the grid voltage Pccdref , the d-axis and q-axis components of the grid-connected point voltage u Pccd and u Pccq , the output is the current d-axis and q-axis reference value i* GFMd and i* GFMq .

[0175] The power calculation module includes active power and reactive power, as shown in Formula 8:

[0176]

[0177] Among them, u d Refers to the d-axis component u of the grid connection point voltage Pccd 、u q Refers to the q-axis component u of the grid connection point voltage Pccq ,i d Refers to the d-axis component i of the grid-connected point current gd ,i q Refers to the q-axis component i of the grid-connected current gq The output of the power calculation module is the actual value of active power output P e And the actual value of reactive power output Q eThe Low Pass Filter (LPF) in the power calculation module is used to smooth the power signal. The excitation ring control enable switch is used to switch between the open state (5) and the closed state (6).

[0178] Figure 5 The control mode seamless switching flow chart of the grid-connected inverter provided in this application is Figure 4 The process of seamless switching of control modes is further explained based on the switching diagram shown in FIG. Figure 5 As shown in the figure, the switching process includes:

[0179] B1. Detect the switching signal.

[0180] B2. Determine whether the switching signal indicates switching from the GFL mode to the GFM mode. If so, jump to B3; otherwise, jump to B9.

[0181] B3. Initialize the integrator of the GFM mode power synchronization loop to the output phase θ of the GFL mode phase-locked loop.

[0182] B4. Confirm that the excitation ring switch is in the "5" position.

[0183] B6. Switch the signal selection switch of the grid synchronization module and the reference source selection switch of the current loop from position "1" to position "2".

[0184] B7: Determine whether the system has reached a steady state. If so, proceed to B8; otherwise, proceed to B7 and continue determining.

[0185] B8. Switch the control enable switch of the excitation ring to the "6" position to complete the conversion.

[0186] B9: Determine whether the switching signal indicates switching from GFM mode to GFL mode. If yes, jump to B10; otherwise, jump to B1.

[0187] B10. Initialize the power reference value of the GFL mode to the power output steady-state value of the GFM mode.

[0188] B11. Confirm that the power ring switch is in the "3" position.

[0189] B12. Switch the signal selection switch of the grid synchronization module and the reference source selection switch of the current loop from position "2" to position "1".

[0190] B13. Determine whether the system has reached a steady state. If so, proceed to B14; otherwise, proceed to B13 and continue determining.

[0191] B14. Switch the power ring to position "4".

[0192] Figure 6The voltage and current comparison diagram of the grid-connected inverter provided in this application before and after the seamless switching method is adopted, such as Figure 6 As shown in Figure 1, it includes two parts (a) and (b). In part (a), the grid connection point voltage is observed. When the seamless switching method is used, the grid connection point voltage shows a stable periodic change, that is, the waveform is stable; no other fluctuations occur when the control mode switches. When the seamless switching method is not used, the grid connection point voltage experiences a voltage jump when switching between GFM mode and GFL mode. In part (b), the inverter current is observed. When the seamless switching method is used, the inverter current shows a stable periodic change, that is, the waveform is stable; no other fluctuations occur when the control mode switches. When the seamless switching method is not used, the inverter current shows a continuous deviation in the current curve when switching between GFM mode and GFL mode.

[0193] Figure 7 This is a schematic diagram of the structure of the grid-connected inverter control mode switching device provided in this application, as shown in Figure 7 As shown, the grid-connected inverter control mode switching device provided in this embodiment includes:

[0194] The acquisition module 701 is configured to acquire a control mode switching signal of the grid-connected inverter and determine a switching direction of the control mode based on the switching signal.

[0195] The first processing module 702 is configured to, when the current control mode is the GFL mode and the switching direction indicates that the current control mode is switched from the GFL mode to the GFM mode, obtain a phase angle value of a phase-locked loop corresponding to the GFL mode, set an initial value of an integrator of a power synchronization loop in the GFM mode to the phase angle value, and switch the control mode from the GFL mode to the GFM mode based on a first preset path and a step-by-step switching method.

[0196] The second processing module 703 is configured to, when the current control mode is GFM and the switching direction indicates that the current control mode is switched from the GFM mode to the GFL mode, obtain the steady-state power output value of the GFM mode, set the power reference value of the GFL mode to the steady-state power output value; and switch the control mode from the GFM mode to the GFL mode based on the second preset path and the step-by-step switching method.

[0197] Among them, in the GFL mode and the GFM mode, the control structure inside the current loop is consistent.

[0198] In a possible implementation, the first processing module 702 is further configured to:

[0199] When the control enable switch of the excitation loop of the grid-connected inverter is in the open state, the signal selection switch of the grid synchronization module in the grid-connected inverter is switched from the output end of the phase-locked loop to the output end of the power synchronization loop.

[0200] Switch the reference source selection switch of the current loop in the grid-connected inverter from the power loop output end to the voltage loop output end.

[0201] When the grid-connected inverter is in a stable state, the control enable switch of the excitation loop of the grid-connected inverter is switched to a closed state.

[0202] In a possible implementation, the second processing module 703 is further configured to:

[0203] The active power output by the grid-connected inverter within a first preset time period is obtained, and an average value of the active power is calculated.

[0204] The real-time voltage amplitude of the grid-connected inverter is obtained, and the reactive power output value of the grid-connected inverter is calculated based on the preset reactive power reference value and the real-time voltage amplitude.

[0205] The steady-state power output value is determined based on the active power average value and the reactive power output value.

[0206] Set the power reference value of the GFL mode to the power steady-state output value;

[0207] Based on the second preset path and the step-by-step switching method, the control mode is switched from the GFM mode to the GFL mode.

[0208] In a possible implementation, the second processing module 703 is further configured to:

[0209] When the power loop of the grid-connected inverter is in an open-loop holding mode, a reference source selection switch of a current loop in the grid-connected inverter is switched from a voltage loop output end to a power loop output end.

[0210] Switch the signal selection switch of the grid synchronization module in the grid-connected inverter from the output end of the power synchronization loop to the output end of the phase-locked loop.

[0211] When the grid-connected inverter is in a stable state, the power loop is switched from the open-loop holding mode to the closed-loop regulation mode.

[0212] In a possible implementation, the apparatus further includes a third processing module 704, configured to:

[0213] Obtain the operating status data of the target power grid corresponding to the grid-connected inverter.

[0214] When the operating status data meets the first preset condition and the control mode of the grid-connected inverter is the GFL mode, the control mode of the grid-connected inverter is switched to the GFM mode.

[0215] The first preset condition refers to that the voltage value in the operating status data is continuously lower than the first preset threshold value within the second preset time period, and the fluctuation range of the frequency value in the operating status data exceeds the preset range.

[0216] In a possible implementation, the third processing module 704 is further configured to:

[0217] When the operating status data meets the second preset condition and the control mode of the grid-connected inverter is the GFM mode, the control mode of the grid-connected inverter is switched to the GFL mode.

[0218] The second preset condition refers to that the voltage harmonic rate in the operating status data is less than a second preset threshold, and the change value of the grid impedance value in the operating status data exceeds a third preset threshold.

[0219] The device provided in this embodiment can execute the method provided in the above method embodiment. Its implementation principle and technical effects are similar and will not be described in detail in this embodiment.

[0220] Figure 8 This is a schematic diagram of the structure of the electronic device provided in this application. Figure 8 As shown, the electronic device provided in this embodiment includes: at least one processor 801 and a memory 802. Optionally, the device further includes a communication component 803. The processor 801, the memory 802, and the communication component 803 are connected via a bus 804.

[0221] In a specific implementation process, at least one processor 801 executes the computer-executable instructions stored in the memory 802, so that the at least one processor 801 executes the above-mentioned grid-connected inverter control mode switching method or methods.

[0222] The specific implementation process of the processor 801 can be found in the above method embodiment. Its implementation principle and technical effects are similar and will not be repeated here in this embodiment.

[0223] In the above embodiments, it should be understood that the processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASICs), etc. A general-purpose processor may be a microprocessor or any conventional processor. The steps of the method disclosed in the present invention may be directly executed by a hardware processor or by a combination of hardware and software modules within the processor.

[0224] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage.

[0225] A bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus. Buses can be categorized as address buses, data buses, and control buses. For ease of illustration, the buses in the drawings of this application are not limited to just one bus or just one type of bus.

[0226] The present application also provides a computer program product, including a computer program, which implements the above method when executed by a processor.

[0227] The present application also provides a computer-readable storage medium, in which computer-executable instructions are stored. When a processor executes the computer-executable instructions, the above method is implemented.

[0228] The readable storage medium may be implemented by any type of volatile or non-volatile memory device, or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium may be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0229] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Alternatively, the readable storage medium may be an integral part of the processor. The processor and readable storage medium may reside in an application-specific integrated circuit (ASIC). Alternatively, the processor and readable storage medium may reside in a device as discrete components.

[0230] The division of units is merely a logical functional division; actual implementations may employ alternative divisions, such as combining or integrating multiple units or components into another system, or omitting or disabling certain features. Furthermore, any coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between devices or units, whether electrical, mechanical, or otherwise, through some interface.

[0231] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0232] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0233] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the various embodiments of the method of the present invention. The aforementioned storage medium includes various media that can store program code, such as USB flash drives, mobile hard drives, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical disks.

[0234] Those skilled in the art will appreciate that all or part of the steps in the above-described method embodiments can be implemented using hardware associated with program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0235] Finally, it should be noted that those skilled in the art will readily identify other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art not disclosed herein. The present invention is not limited to the precise structure described above and illustrated in the accompanying drawings, and various modifications and variations may be made without departing from the scope thereof. The scope of the present invention is limited solely by the appended claims.

Claims

1. A method for switching control modes of a grid-connected inverter, characterized in that: include: Acquire a control mode switching signal of the grid-connected inverter, and determine a switching direction of the control mode based on the switching signal; When the current control mode is a grid-following GFL mode and the switching direction indicates that the current control mode is switched from the GFL mode to the grid-forming GFM mode, obtaining a phase angle value of a phase-locked loop corresponding to the GFL mode, setting an initial value of an integrator of a power synchronization loop of the GFM mode to the phase angle value; and switching the control mode from the GFL mode to the GFM mode based on a first preset path and a step-by-step switching manner; When the current control mode is the GFM mode and the switching direction indicates that the current control mode is switched from the GFM mode to the GFL mode, obtaining a steady-state power output value of the GFM mode, and setting a power reference value of the GFL mode as the steady-state power output value; and switching the control mode from the GFM mode to the GFL mode based on a second preset path and a step-by-step switching method; Among them, in the GFL mode and the GFM mode, the control structure inside the current loop is consistent.

2. The method according to claim 1, characterized in that The step of switching the control mode from the GFL mode to the GFM mode based on the first preset path and the step-by-step switching method includes: When the control enable switch of the excitation loop of the grid-connected inverter is in an open state, switching the signal selection switch of the grid synchronization module in the grid-connected inverter from the output end of the phase-locked loop to the output end of the power synchronization loop; Switching the reference source selection switch of the current loop in the grid-connected inverter from the power loop output end to the voltage loop output end; When the grid-connected inverter is in a stable state, a control enable switch of the excitation loop of the grid-connected inverter is switched to a closed state.

3. The method according to claim 1, characterized in that The obtaining of the steady-state power output value of the GFM mode and setting the power reference value of the GFL mode as the steady-state power output value; Based on the second preset path and the step-by-step switching method, the control mode is switched from the GFM mode to the GFL mode, including: Obtaining the active power output by the grid-connected inverter within a first preset time period, and calculating an average active power; Obtaining a real-time voltage amplitude of the grid-connected inverter, and calculating a reactive power output value of the grid-connected inverter based on a preset reactive power reference value and the real-time voltage amplitude; Determining the steady-state power output value based on the active power mean value and the reactive power output value; Setting the power reference value of the GFL mode as the power steady-state output value; Based on a second preset path and a step-by-step switching approach, the control mode is switched from the GFM mode to the GFL mode.

4. The method according to claim 3, characterized in that The step of switching the control mode from the GFM mode to the GFL mode based on the second preset path and the step-by-step switching method includes: When the power loop of the grid-connected inverter is in an open-loop holding mode, switching a reference source selection switch of a current loop in the grid-connected inverter from a voltage loop output end to a power loop output end; Switching the signal selection switch of the grid synchronization module in the grid-connected inverter from the output end of the power synchronization loop to the output end of the phase-locked loop; When the grid-connected inverter is in a stable state, the power loop is switched from an open-loop holding mode to a closed-loop regulation mode.

5. The method according to claim 1, characterized in that The method further comprises: Obtaining operating status data of a target power grid corresponding to the grid-connected inverter; When the operating status data meets a first preset condition and the control mode of the grid-connected inverter is a GFL mode, switching the control mode of the grid-connected inverter to a GFM mode; The first preset condition refers to that the voltage value in the operating status data is continuously lower than the first preset threshold value within a second preset time period, and the fluctuation range of the frequency value in the operating status data exceeds a preset range.

6. The method according to claim 5, characterized in that The method further comprises: When the operating status data meets a second preset condition and the control mode of the grid-connected inverter is the GFM mode, switching the control mode of the grid-connected inverter to the GFL mode; The second preset condition refers to that the voltage harmonic rate in the operating status data is less than a second preset threshold, and the change value of the grid impedance value in the operating status data exceeds a third preset threshold.

7. A grid-connected inverter control mode switching device, characterized in that: include: an acquisition module, configured to acquire a control mode switching signal of the grid-connected inverter, and determine a switching direction of the control mode based on the switching signal; a first processing module configured to, when a current control mode is a GFL mode and the switching direction indicates that the current control mode is switched from the GFL mode to the GFM mode, obtain a phase angle value of a phase-locked loop corresponding to the GFL mode, set an initial value of an integrator of a power synchronization loop in the GFM mode to the phase angle value; and switch the control mode from the GFL mode to the GFM mode based on a first preset path and a step-by-step switching method; a second processing module, configured to, when the current control mode is the GFM mode and the switching direction indicates that the current control mode is switched from the GFM mode to the GFL mode, obtain a steady-state power output value of the GFM mode, and set a power reference value of the GFL mode as the steady-state power output value; and switching the control mode from the GFM mode to the GFL mode based on a second preset path and a step-by-step switching method; Among them, in the GFL mode and the GFM mode, the control structure inside the current loop is consistent.

8. An electronic device, characterized in that: include: Memory, processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory, so that the processor performs the method according to any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 6 when executed by a processor.

10. A computer program product, characterized in that The invention comprises a computer program, which implements the method according to any one of claims 1 to 6 when the computer program is executed by a processor.

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