Mode switching method, device and equipment of converter, storage medium and program product

Abstract

The invention relates to a mode switching method and device of a converter, equipment, a storage medium and a program product. The method comprises the following steps: acquiring a three-phase AC voltage and a three-phase AC current of a grid-connected system port; performing phase-locked loop conversion on the three-phase alternating voltage and a preset system rotation angle to obtain a target system rotation angle and a power angle; switching the mode of a target converter from a first mode to a second mode according to the target system rotation angle and the power angle; and obtaining a current reference value of the target converter in the second mode, and obtaining a switch control signal of the target converter based on the current reference value, the three-phase alternating current, the direct current bus voltage and a triangular wave signal, so as to realize alternating current and direct current conversion based on the switch control signal. By adopting the method, the steady-state switching of the converter can be realized.

Description

Technical Field

[0001] This application relates to the field of electrical system technology, and in particular to a mode switching method, apparatus, device, storage medium, and program product for a converter. Background Technology

[0002] Under the current grid situation characterized by a high proportion of renewable energy integration, the volatility of renewable energy generation has brought unprecedented challenges to the grid. Simultaneously, the widespread application of numerous power electronic devices has exacerbated the decoupling between renewable energy generation and grid frequency, significantly worsening system stability.

[0003] Against this backdrop, new energy equipment is subject to higher requirements. It must not only achieve efficient energy conversion but also possess auxiliary service capabilities such as inertial response, primary frequency regulation response, and suppression of various oscillations, thereby actively participating in the power and frequency stability regulation process of the power grid. In the process of new energy grid integration, the control modes of power electronic converters mainly include grid-following control and grid-connecting control. Among them, the grid-following control mode has advantages such as mature technology, abundant product types, and relatively low cost, and has dominated past new energy grid-connection applications. In contrast, the converter in the grid-connecting control mode exhibits voltage source characteristics externally. It generates voltage amplitude and phase angle through unique power control equations, thus cleverly avoiding the use of phase-locked loops that rely on grid synchronization.

[0004] With the increasing demands for grid stability and new energy utilization efficiency, single grid-following or grid-building control is no longer sufficient to meet the complex and ever-changing grid requirements. Hybrid grid-following and grid-building control can significantly improve grid stability while ensuring strong power tracking control capabilities. The basic principle of hybrid grid-following and grid-building control is to allow grid-connected converters to adopt grid-following mode control under strong grid conditions to fully leverage their power tracking advantages, and switch to grid-building mode control under weak grid conditions to enhance their support capabilities for the grid.

[0005] However, the current converter mode switching method suffers from poor stability. Summary of the Invention

[0006] Therefore, it is necessary to provide a converter mode switching method, apparatus, equipment, storage medium, and program product that can improve the stability of converter mode switching, thereby addressing the aforementioned technical problems.

[0007] Firstly, this application provides a mode switching method for a converter, including:

[0008] Obtain the three-phase AC voltage and three-phase AC current at the grid-connected system port;

[0009] A phase-locked loop transformation is performed on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle. The power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system. The target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system.

[0010] Based on the target system's rotation angle and power angle, the target converter's mode is switched from the first mode to the second mode;

[0011] The current reference value of the target converter in the second mode is obtained, and based on the current reference value, three-phase AC current, DC bus voltage and triangular wave signal, the switching control signal of the target converter is obtained, so as to realize AC-DC conversion based on the switching control signal.

[0012] In one embodiment, where the first mode is a grid-connected control mode and the second mode is a grid-following control mode, obtaining the current reference value of the target converter in the second mode includes:

[0013] The active power and reactive power are determined based on the three-phase AC voltage, three-phase AC current and preset system rotation angle;

[0014] The current reference value is determined based on the active power, active power reference value, reactive power, reactive power reference value, and power angle.

[0015] In one embodiment, where the first mode is a grid-following control mode and the second mode is a grid-connecting control mode, obtaining the current reference value of the target converter in the second mode includes:

[0016] Determine the internal potential reference value based on the reactive power and the reactive power reference value;

[0017] The current reference value is determined based on the internal potential reference value, the three-phase AC voltage, and the grid-connected current vector.

[0018] In one embodiment, determining the active power and reactive power based on the three-phase AC voltage, three-phase AC current, and a preset system rotation angle includes:

[0019] Determine the two-phase voltage in the synchronous rotating coordinate system based on the three-phase AC voltage and the preset system rotation angle;

[0020] Based on the three-phase AC current and the preset system rotation angle, determine the two-phase current in the synchronous rotating coordinate system;

[0021] The active power and reactive power are determined based on the two-phase voltage and the two-phase current.

[0022] In one embodiment, determining the current reference value based on active power, active power reference value, reactive power, reactive power reference value, and power angle includes:

[0023] The active power deviation between the active power and the active power reference value, the reactive power deviation between the reactive power and the reactive power reference value, and the power angle are rotated and transformed to obtain the transformed active power and the transformed reactive power.

[0024] The transformed active power and the transformed reactive power are input to the PI regulator to obtain the current reference value.

[0025] In one embodiment, the switching control signal of the target converter, obtained based on the current reference value, three-phase AC current, DC bus voltage, and triangular wave signal, includes:

[0026] Determine the duty cycle based on the current reference value and the three-phase AC current;

[0027] Determine the valve-side control voltage based on the duty cycle and DC bus voltage;

[0028] The valve-side control voltage is converted into a three-phase voltage to obtain a three-phase voltage quantity;

[0029] Based on the three-phase voltage and triangular wave, the switching control signal of the target converter is obtained.

[0030] In one embodiment, the above-mentioned phase-locked loop transformation of the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle includes:

[0031] The three-phase AC voltage and the preset system rotation angle are rotated to obtain the x-axis voltage and y-axis voltage;

[0032] The x-axis voltage is input to the first phase-locked loop for calculation to obtain the rotation angle of the target system.

[0033] The y-axis voltage is input to the second phase-locked loop for calculation to obtain the power angle.

[0034] Secondly, this application also provides a mode switching device for a converter, comprising:

[0035] The acquisition module is used to acquire the three-phase AC voltage and three-phase AC current at the grid-connected system port;

[0036] The conversion module is used to perform phase-locked loop conversion on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle. The power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system. The target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system.

[0037] The switching module is used to switch the mode of the target converter from the first mode to the second mode according to the rotation angle and power angle of the target system.

[0038] The determination module is used to obtain the current reference value of the target converter in the second mode, and based on the current reference value, three-phase AC current, DC bus voltage and triangular wave signal, obtain the switching control signal of the target converter, so as to realize AC-DC conversion based on the switching control signal.

[0039] Thirdly, this application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0040] Obtain the three-phase AC voltage and three-phase AC current at the grid-connected system port;

[0041] A phase-locked loop transformation is performed on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle. The power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system. The target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system.

[0042] Based on the target system's rotation angle and power angle, the target converter's mode is switched from the first mode to the second mode;

[0043] The current reference value of the target converter in the second mode is obtained, and based on the current reference value, three-phase AC current, DC bus voltage and triangular wave signal, the switching control signal of the target converter is obtained, so as to realize AC-DC conversion based on the switching control signal.

[0044] Fourthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the following steps:

[0045] Obtain the three-phase AC voltage and three-phase AC current at the grid-connected system port;

[0046] A phase-locked loop transformation is performed on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle. The power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system. The target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system.

[0047] Based on the target system's rotation angle and power angle, the target converter's mode is switched from the first mode to the second mode;

[0048] The current reference value of the target converter in the second mode is obtained, and based on the current reference value, three-phase AC current, DC bus voltage and triangular wave signal, the switching control signal of the target converter is obtained, so as to realize AC-DC conversion based on the switching control signal.

[0049] Fifthly, this application also provides a computer program product, including a computer program that, when executed by a processor, performs the following steps:

[0050] Obtain the three-phase AC voltage and three-phase AC current at the grid-connected system port;

[0051] A phase-locked loop transformation is performed on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle. The power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system. The target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system.

[0052] Based on the target system's rotation angle and power angle, the target converter's mode is switched from the first mode to the second mode;

[0053] The current reference value of the target converter in the second mode is obtained, and based on the current reference value, three-phase AC current, DC bus voltage and triangular wave signal, the switching control signal of the target converter is obtained, so as to realize AC-DC conversion based on the switching control signal.

[0054] The aforementioned converter mode switching method, device, equipment, storage medium, and program product monitor the grid-connected port voltage and current in real time, accurately calculate the power angle and system rotation angle between the target converter and the grid using a phase-locked loop, and smoothly switch the operating mode accordingly. In the new mode, it integrates current reference, DC bus voltage, and triangular wave signal to generate optimized switching control signal, achieving efficient AC-DC conversion. This significantly improves the synchronization accuracy, operational stability, and power conversion efficiency of the system grid connection, while reducing the impact and losses caused by phase angle deviation. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 This is a diagram illustrating the application environment of a converter mode switching method in one embodiment.

[0057] Figure 2 This is a flowchart illustrating a mode switching method for a converter in one embodiment;

[0058] Figure 3 This is a flowchart illustrating the mode switching method of the converter in another embodiment;

[0059] Figure 4 This is a flowchart illustrating the mode switching method of the converter in another embodiment;

[0060] Figure 5 This is a flowchart illustrating the mode switching method of the converter in another embodiment;

[0061] Figure 6 This is a flowchart illustrating the mode switching method of the converter in another embodiment;

[0062] Figure 7 This is a flowchart illustrating the mode switching method of the converter in another embodiment;

[0063] Figure 8 This is a flowchart illustrating the mode switching method of the converter in another embodiment;

[0064] Figure 9 This is a schematic diagram of the internal structure of the control system in one embodiment;

[0065] Figure 10 This is a schematic diagram of coordinates and main vectors in one embodiment;

[0066] Figure 11 This is a schematic diagram of the simulation results of the network switching control in one embodiment;

[0067] Figure 12 This is a schematic diagram of the simulation results for network switching control in another embodiment;

[0068] Figure 13 This is a schematic diagram of the simulation results for network switching control in another embodiment;

[0069] Figure 14This is a schematic diagram of the simulation results for network switching control in another embodiment;

[0070] Figure 15 This is a schematic diagram of the simulation results for network switching control in another embodiment;

[0071] Figure 16 This is a schematic diagram of the simulation results for network switching control in another embodiment;

[0072] Figure 17 This is a schematic diagram of the simulation results for network switching control in another embodiment;

[0073] Figure 18 This is a structural block diagram of the mode switching device of a converter in one embodiment;

[0074] Figure 19 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0075] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0076] With the vigorous promotion and application of clean energy globally, the proportion of renewable energy generation in the power system is increasing daily. In traditional power systems, synchronous generators, thanks to their strong electromechanical coupling characteristics, can quickly adjust their speed through torque changes when the system experiences active power imbalances, thereby maintaining system frequency stability and ensuring the reliable operation of the entire power grid. However, under the current situation of high-proportion renewable energy grids, the volatility of renewable energy generation has brought unprecedented challenges to the power grid. Simultaneously, the widespread application of numerous power electronic devices has exacerbated the decoupling between renewable energy generation and the grid frequency, significantly worsening system stability. For example, in some regional power grids dominated by wind and solar power, excessively large frequency fluctuations and deteriorating voltage stability frequently occur, severely impacting the reliability and stability of the power grid.

[0077] Against this backdrop, new energy equipment is being given higher requirements. It must not only achieve efficient energy conversion, but also provide inertial response, primary frequency regulation response, and auxiliary services to suppress various oscillations, so as to actively participate in the power and frequency stability regulation process of the power grid.

[0078] In the process of integrating new energy sources into the power grid, the control modes of power electronic converters mainly include two types: grid-connected control and grid-building control. These two control modes are described below:

[0079] (1) Grid-following control: In this mode, the converter exhibits current source characteristics. To achieve synchronous operation with the grid, the converter typically employs phase-locked loop (PLL) technology. The PLL monitors the voltage and phase information of the grid in real time, thereby precisely controlling the output current of the converter to closely follow changes in the grid. For example, most common photovoltaic inverters use grid-following control when operating in grid-connected mode. After converting the DC power generated by the photovoltaic array into AC power, it is injected into the grid according to the grid's requirements. This control mode has advantages such as mature technology, a wide variety of products, and relatively low cost, and has dominated the past applications of new energy grid connection. However, grid-following control has weak grid support capabilities, especially in weak grid environments. When the grid experiences disturbances such as voltage drops and frequency fluctuations, grid-following converters, due to their high dependence on the voltage and phase signals of the grid for operation control, often can only passively respond to these changes. In extreme cases, grid disconnection may even occur, failing to provide effective support to the grid and further exacerbating grid instability. For example, in some remote areas with weak power grids, when the power generation of new energy sources suddenly changes significantly, the grid-connected wind power converters may trip because they cannot adapt to the fluctuations in the grid in time, resulting in a large number of wind power plants being unable to connect to the grid smoothly, which seriously affects the stability and reliability of the power supply.

[0080] (2) Grid-based control: In this mode, the converter exhibits voltage source characteristics. It generates voltage amplitude and phase angle through a unique power control equation, thus cleverly avoiding the use of phase-locked loops that rely on grid synchronization. Taking Virtual Synchronous Generator (VSG) control as an example, this is one of the most widely used grid-based control methods. In the active power loop, the phase angle is directly generated; the reactive power loop is responsible for generating the amplitude, and then a stable output is achieved through corresponding modulation techniques. Theoretically, this control method can adapt to grid operation conditions with up to 100% electronic equipment penetration, has a strong ability to form a network autonomously, and has good adaptability to the modern grid form dominated by new energy sources. For example, in some microgrid projects, energy storage converters using grid-based control can autonomously establish stable voltage and frequency in off-grid conditions, providing reliable power supply to the loads in the microgrid. Although grid-based control has significant advantages in improving grid support capabilities, it is relatively weak in power point tracking control capabilities. During the switching process from islanded to grid-connected or vice versa, the control algorithm needs to readjust its internal parameters to adapt to the new operating state, which can easily lead to insufficient control precision. This can cause significant voltage and current surges during the switching process, severely impacting system stability and shortening equipment lifespan.

[0081] With increasingly stringent requirements for grid stability and renewable energy utilization efficiency, single grid-following or grid-building control methods are no longer sufficient to meet the complex and ever-changing demands of the power grid. Research indicates that hybrid grid-following and grid-building control can significantly improve grid stability while maintaining strong power point tracking (PPT) capabilities. Among these, switching-mode hybrid control is a common approach. Its basic principle is to allow the grid-connected converter to use grid-following mode control under strong grid conditions to fully leverage its PPT advantages; and to switch to grid-building mode control under weak grid conditions to enhance its support for the grid. However, current converter mode switching methods suffer from poor stability. Therefore, this application provides a converter mode switching method to address these issues.

[0082] Having described the background of the converter mode switching method provided in this application, we can also introduce the implementation environment of the converter mode switching method provided in this application. The converter mode switching method provided in this embodiment can be applied to, for example, Figure 1 The implementation environment shown includes: a new energy grid-connected system 102 and a control system 104. The new energy grid-connected system 102 includes a DC bus (DC voltage U) connected in sequence. dc ), converter, grid-connected reactor (resistor R) s Inductor L s The control system 104 is connected to the grid connection port between the transformer and the grid-connected converter in the new energy grid-connected system 102, as well as between the converters. The control system 104 can obtain the three-phase AC voltage U from the grid connection port. abc and three-phase alternating current I abc And the three-phase AC voltage U abc and three-phase alternating current I abc The signal is processed to obtain the converter switching control signal, which is used to realize AC-DC conversion and control the grid-connected active power P and reactive power Q.

[0083] In one embodiment, such as Figure 2 As shown, a mode switching method for a converter is provided, which can be applied to... Figure 1 Taking the control system 104 as an example, the following steps are included:

[0084] S201. Obtain the three-phase AC voltage and three-phase AC current at the grid-connected system port.

[0085] In this embodiment, the control system first acquires the three-phase AC voltage U at the grid-connected system port. abc and three-phase alternating current I abc .

[0086] S202. Perform a phase-locked loop transformation on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle; the power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system; the target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system.

[0087] Among them, the preset system rotation angle In the network fabrication (GFM) mode In GFL (Global Follower) mode .

[0088] In this embodiment, the three-phase AC voltage U is obtained as described above. abc Then, based on the three-phase AC voltage U abc The target system rotation angle and power angle are obtained by performing a phase-locked loop transformation with the preset system rotation angle.

[0089] Optionally, a method for determining the rotation angle and power angle of the target system is provided below; see [link to relevant documentation]. Figure 3 The aforementioned S202 includes:

[0090] S2021. Rotate the three-phase AC voltage and the preset system rotation angle to obtain the x-axis voltage and y-axis voltage.

[0091] In this embodiment, the following formula (1) can be used to perform rotation transformation on the three-phase AC voltage and the preset system rotation angle to obtain the x-axis voltage and y-axis voltage:

[0092] (1).

[0093] S2022. Input the x-axis voltage to the first phase-locked loop for calculation to obtain the rotation angle of the target system.

[0094] In this embodiment, the x-axis voltage U x The data is fed into the first phase-locked loop for calculation to obtain the rotation angle of the target system. The process is described in the following formula (2):

[0095] (2);

[0096] In the formula, The system angular frequency, For differential operators, This is the proportional gain of the phase-locked loop. U represents the integral coefficient of the phase-locked loop. q That is, the x-axis voltage U x .

[0097] S2023. Input the y-axis voltage to the second phase-locked loop for calculation to obtain the power angle.

[0098] In this embodiment, the y-axis voltage U can also be... y The power angle is obtained by feeding the data into the second phase-locked loop for calculation. See formula (3) below:

[0099]

[0100] Since GFM=0 in the grid-following control mode and GFM=1 in the grid-building mode, the second phase-locked loop is only effective in the grid-building mode, while the output remains unchanged in the grid-following mode.

[0101] At this point, the attack angle has been determined. Rotation angle of the target system .

[0102] S203. Based on the rotation angle and power angle of the target system, switch the mode of the target converter from the first mode to the second mode.

[0103] In this embodiment, after determining the target system rotation angle and power angle, the mode of the target converter can be switched from the first mode to the second mode based on the target system rotation angle and power angle.

[0104] S204. Obtain the current reference value of the target converter in the second mode, and based on the current reference value, three-phase AC current, DC bus voltage and triangular wave signal, obtain the switching control signal of the target converter, so as to realize AC-DC conversion based on the switching control signal.

[0105] In this embodiment, after switching the target converter from the first mode to the second mode, the current reference value of the target converter in the second mode can be obtained, and based on the current reference value, the three-phase AC current, the DC bus voltage and the triangular wave signal, the switching control signal of the target converter can be obtained, so as to realize AC-DC conversion based on the switching control signal.

[0106] Optionally, the following provides a specific implementation method for obtaining the switching control signal of the target converter based on the current reference value, three-phase AC current, DC bus voltage, and triangular wave signal. See [link to relevant documentation]. Figure 4 The aforementioned S204 includes:

[0107] S2041. Determine the duty cycle based on the current reference value and the three-phase AC current.

[0108] In this embodiment, the three-phase AC voltage and the preset system rotation angle can be rotated to obtain the x-axis current and y-axis current. The process is described in the following formula (4):

[0109] (4);

[0110] Furthermore, the duty cycle d is determined based on the current reference value, the x-axis current, and the y-axis current. dq The process is described in the following formula (5):

[0111] (5);

[0112] In the formula, i d yref and i q yref All are current reference values, i d Let i be the x-axis current. q The current is along the y-axis. k is the integral coefficient of the current loop. ip This refers to the proportional gain of the current loop.

[0113] S2042. Determine the valve-side control voltage based on the duty cycle and DC bus voltage.

[0114] In this embodiment, a method V for determining the valve-side control voltage based on the duty cycle and the DC bus voltage is provided. xy See the following formula (6):

[0115] (6);

[0116] In the formula, U dc d is the DC bus voltage. x That is, d in the above formula (5) d d y That is, d in the above formula (5) q min(·) is the function that takes the minimum value.

[0117] S2043. Convert the valve-side control voltage into a three-phase voltage to obtain a three-phase voltage quantity.

[0118] In this embodiment, the valve-side control voltage V is obtained as described above. xy Then, the valve-side control voltage V can be... xy Three-phase electricity conversion is performed to obtain three-phase voltage quantities. The process is shown in the following formula (7):

[0119] (7);

[0120] In the formula, V d That is, V in the above formula (6) x V q That is, V in the above formula (6) y V a V b Vc This refers to the three-phase voltage.

[0121] S2044. Based on the three-phase voltage and triangular wave, obtain the switching control signal of the target converter.

[0122] In this embodiment, after obtaining the three-phase voltage, the three-phase voltage can be compared with the triangular wave to obtain the switching control signal of the target converter.

[0123] The converter mode switching method provided in this embodiment monitors the grid-connected port voltage and current in real time, uses a phase-locked loop to accurately calculate the power angle and system rotation angle between the target converter and the grid, and smoothly switches the operating mode accordingly. In the new mode, it integrates current reference, DC bus voltage and triangular wave signal to generate optimized switching control signal, realizes efficient AC-DC conversion, significantly improves the synchronization accuracy, operating stability and power conversion efficiency of the system grid connection, and reduces the impact and loss caused by phase angle deviation.

[0124] In this embodiment, in the above Figure 2 Based on the illustrated embodiment, with the first mode being grid-connected control mode and the second mode being grid-following control mode, this embodiment will explain in detail the process of obtaining the current reference value of the target converter in the second mode. In an exemplary embodiment, such as Figure 5 As shown, the above S204 includes:

[0125] S301. Determine the active power and reactive power based on the three-phase AC voltage, three-phase AC current and preset system rotation angle.

[0126] In this embodiment, the two-phase voltage and two-phase current can be determined first based on the three-phase AC voltage, three-phase AC current and preset system rotation angle, combined with the above formulas (1) and (4).

[0127] Furthermore, the active power P and reactive power Q can be determined by combining the following formula (8) based on the two-phase voltage and two-phase current:

[0128] (8).

[0129] S302. Determine the current reference value based on the active power, active power reference value, reactive power, and reactive power reference value.

[0130] In this embodiment, after obtaining the active power P and reactive power Q, the current reference value can be determined based on the active power P, the active power reference value, the reactive power Q, and the reactive power reference value.

[0131] Optionally, the following provides a specific implementation method for determining the current reference value based on the active power P, the active power reference value, the reactive power Q, and the reactive power reference value. See [link to implementation details]. Figure 6 The aforementioned S302 includes:

[0132] S3021. Perform rotational transformation on the active power deviation between the active power and the active power reference value, and the reactive power deviation between the reactive power and the reactive power reference value, to obtain the transformed active power and the transformed reactive power.

[0133] In this embodiment, the process of obtaining the transformed active power and the transformed reactive power can be referred to the following formula (9):

[0134] (9);

[0135] Among them, P ref This refers to the active power reference value, Q. ref This refers to the reactive power reference value. It refers to the angle of attack. It refers to the transformed active power. It refers to the reactive power after transformation.

[0136] S3022. Input the transformed active power and the transformed reactive power to the PI regulator to obtain the current reference value.

[0137] In this embodiment, after obtaining the transformed active power and the transformed reactive power, the transformed active power and the transformed reactive power can be input to the PI regulator to obtain the current reference value. The process is described in the following formula (10):

[0138] (10);

[0139] in, This is the power loop proportional coefficient. i is the power loop integral coefficient. xref GFL This refers to the current reference value along the x-axis, i yref GFL This refers to the current reference value along the y-axis.

[0140] It should be noted that when switching between grid-connected and grid-connected control modes, the state variables of the integrator inside the voltage regulator will be updated, and the initial value of the update is the current setpoint at the time of switching.

[0141] In this embodiment, active and reactive power are directly calculated by instantaneous voltage and current sampling, and a current reference is generated by combining the respective reference values ​​and power angle in a closed loop. This enables real-time linkage between power regulation and phase error, achieving precise independent control of active and reactive power while automatically compensating for power deviation caused by power angle offset. This significantly improves the system's dynamic tracking speed of power commands, steady-state accuracy, and resistance to grid disturbances, while reducing overcurrent risk and ensuring efficient, safe, and reliable operation of the converter during grid connection.

[0142] In this embodiment, in the above Figure 2 Based on the illustrated embodiment, with the first mode being grid-following control mode and the second mode being grid-connecting control mode, this embodiment will explain in detail the process of obtaining the current reference value of the target converter in the second mode. In an exemplary embodiment, such as Figure 7 As shown, the above S204 includes:

[0143] S401. Determine the internal potential reference value based on the reactive power and the reactive power reference value.

[0144] In this embodiment, a process for determining the internal potential reference value E based on reactive power and reactive power reference value is provided, as shown in the following formula (11):

[0145] (11);

[0146] In this context, the subscript ref indicates a reference value. This is the proportionality coefficient. The integral coefficient is... It is a differential operator.

[0147] S402. Determine the current reference value based on the internal potential reference value, the three-phase AC voltage, and the grid-connected current vector.

[0148] In this embodiment, after obtaining the internal potential reference value as described above, the current reference value can be determined based on the internal potential reference value, the three-phase AC voltage, and the grid-connected current vector, as shown in the following formula (12):

[0149] (12);

[0150] Among them, i xref GFM This refers to the current reference value along the x-axis, i yref GFM This refers to the y-axis current reference value, the internal potential reference value E, real() is the function taking the real part of the complex number, imag() is the function taking the imaginary part of the complex number, and I is the grid-connected current vector. The synchronization angular frequency, For differential operators, This is the voltage loop proportionality coefficient. R is the voltage loop integral coefficient, and R is the grid resistance.

[0151] It should be noted that when switching between grid-connected and grid-connected control modes, the state variables of the integrator inside the voltage regulator will be updated, and the initial value of the update is the current setpoint at the time of switching.

[0152] In this embodiment, the reactive power deviation is used as input to generate an internal potential reference in real time. Then, the current reference is solved by combining the grid voltage and grid-connected current vector closed loop, so that reactive power regulation is directly mapped to the accurate correction of the internal potential. This avoids the reactive power steady-state error caused by parameter mismatch in the traditional power-current dual loop, significantly improving the reactive power response speed and steady-state accuracy. At the same time, it takes into account voltage support capability and current limiting constraint, ensuring that the converter can still quickly provide reactive power compensation, maintain grid connection point voltage stability, and reduce overcurrent risk in weak grid or voltage fluctuation scenarios, thus achieving safer, more efficient, and flexible grid-connected operation.

[0153] In one embodiment, see Figure 8 A method for switching the mode of a converter is also provided, including:

[0154] T1. Obtain the three-phase AC voltage and three-phase AC current at the grid-connected system port;

[0155] T2. Rotate the three-phase AC voltage and the preset system rotation angle to obtain the x-axis voltage and y-axis voltage;

[0156] T3. Input the x-axis voltage into the first phase-locked loop for calculation to obtain the rotation angle of the target system;

[0157] T4. Input the y-axis voltage to the second phase-locked loop for calculation to obtain the power angle; the power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system; the target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system;

[0158] T5. Based on the target system's rotation angle and power angle, switch the target converter's mode from the first mode to the second mode;

[0159] T6. Determine the two-phase voltage in the synchronous rotating coordinate system based on the three-phase AC voltage and the preset system rotation angle;

[0160] T7. Determine the two-phase current in the synchronous rotating coordinate system based on the three-phase AC current and the preset system rotation angle;

[0161] T8. Determine the active power and reactive power based on the two-phase voltage and two-phase current;

[0162] T9. Perform rotational transformation on the active power deviation between the active power and the active power reference value, the reactive power deviation between the reactive power and the reactive power reference value, and the power angle to obtain the transformed active power and the transformed reactive power.

[0163] T10. Input the transformed active power and the transformed reactive power into the PI regulator to obtain the current reference value.

[0164] T11. In the first mode, which is grid-following control mode, and the second mode, which is grid-building control mode, the internal potential reference value is determined based on the reactive power and the reactive power reference value.

[0165] T12. Determine the current reference value based on the internal potential reference value, the three-phase AC voltage, and the grid-connected current vector;

[0166] T13. Determine the duty cycle based on the current reference value and the three-phase AC current;

[0167] T14. Determine the valve-side control voltage based on the duty cycle and DC bus voltage;

[0168] T15. Convert the valve-side control voltage into a three-phase voltage;

[0169] T16. Based on the three-phase voltage and triangular wave, obtain the switching control signal of the target converter, and realize AC-DC conversion based on the switching control signal.

[0170] It should be noted that the descriptions of T1-T16 above can be found in the relevant descriptions in the above embodiments, and their effects are similar, so they will not be repeated here.

[0171] In one embodiment, see Figure 9 Furthermore, a schematic diagram of the internal structure of the control system is provided. The operation process of the internal structure of the control system has been described in detail in the above embodiments and will not be described in detail here.

[0172] See Figure 10 It also provides a coordinate and main vector diagram. After measuring the power angle using a second phase-locked loop, the dq coordinate system, which is usually oriented based on the terminal voltage U, can be changed to an xy coordinate system oriented based on the internal potential E. In grid-following mode, consistency between the internal variables of grid-following and grid-building control is achieved, and bumpless switching is realized in conjunction with the initialization technology of the PI regulator during switching.

[0173] In addition, this application provides simulation results of network-to-network handover control, see [link / reference]. Figures 11-17 As can be seen, the network switching method provided in this application greatly improves the stability of network switching.

[0174] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0175] Based on the same inventive concept, this application also provides a converter mode switching device for implementing the converter mode switching method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more converter mode switching device embodiments provided below can be found in the limitations of the converter mode switching method described above, and will not be repeated here.

[0176] In one exemplary embodiment, such as Figure 18 As shown, a mode switching device for a converter is provided, comprising: an acquisition module 10, a conversion module 11, a switching module 12, and a determination module 13, wherein:

[0177] The acquisition module 10 is used to acquire the three-phase AC voltage and three-phase AC current at the grid-connected system port.

[0178] The transformation module 11 is used to perform phase-locked loop transformation on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle; the power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system; the target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system.

[0179] The switching module 12 is used to switch the mode of the target converter from the first mode to the second mode according to the rotation angle and power angle of the target system.

[0180] The determination module 13 is used to obtain the current reference value of the target converter in the second mode, and based on the current reference value, three-phase AC current, DC bus voltage and triangular wave signal, obtain the switching control signal of the target converter, so as to realize AC-DC conversion based on the switching control signal.

[0181] In an exemplary embodiment, when the first mode is network construction control mode and the second mode is network tracking control mode, the determining module 13 includes:

[0182] The first determining unit is specifically used to determine the active power and reactive power based on the three-phase AC voltage, three-phase AC current and preset system rotation angle;

[0183] The second determining unit is specifically used to determine the current reference value based on the active power, active power reference value, reactive power, reactive power reference value, and power angle.

[0184] In an exemplary embodiment, when the first mode is a network tracking control mode and the second mode is a network construction control mode, the determining module 13 includes:

[0185] The third determining unit is specifically used to determine the internal potential reference value based on the reactive power and the reactive power reference value.

[0186] The fourth determining unit is specifically used to determine the current reference value based on the internal potential reference value, the three-phase AC voltage, and the grid-connected current vector.

[0187] In an exemplary embodiment, the first determining unit is further configured to determine the two-phase voltage in the synchronous rotating coordinate system based on the three-phase AC voltage and the preset system rotation angle; determine the two-phase current in the synchronous rotating coordinate system based on the three-phase AC current and the preset system rotation angle; and determine the active power and reactive power based on the two-phase voltage and the two-phase current.

[0188] In an exemplary embodiment, the second determining unit is further configured to perform rotational transformation on the active power deviation between the active power and the active power reference value, the reactive power deviation between the reactive power and the reactive power reference value, and the power angle to obtain the transformed active power and the transformed reactive power; and input the transformed active power and the transformed reactive power to the PI regulator to obtain the current reference value.

[0189] In an exemplary embodiment, the determining module 13 further includes:

[0190] The fifth determining unit is specifically used to determine the duty cycle based on the current reference value and the three-phase AC current;

[0191] The sixth determining unit is specifically used to determine the valve-side control voltage based on the duty cycle and the DC bus voltage;

[0192] The conversion unit is specifically used to convert the valve-side control voltage into a three-phase voltage;

[0193] The seventh determining unit is specifically used to obtain the switching control signal of the target converter based on the three-phase voltage and the triangular wave.

[0194] In an exemplary embodiment, the transformation module 11 includes:

[0195] The transformation unit is specifically used to perform rotational transformation on the three-phase AC voltage and the preset system rotation angle to obtain the x-axis voltage and y-axis voltage.

[0196] The first calculation unit is specifically used to input the x-axis voltage into the first phase-locked loop for calculation to obtain the rotation angle of the target system.

[0197] The second calculation unit is specifically used to input the y-axis voltage into the second phase-locked loop for calculation to obtain the power angle.

[0198] The modules in the mode switching device of the aforementioned converter can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0199] In one exemplary embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 19 As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores AC power data. The I / O interfaces are used for exchanging information between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When executed by the processor, the computer program implements a mode switching method for a converter.

[0200] Those skilled in the art will understand that Figure 19 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0201] In one exemplary embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0202] Obtain the three-phase AC voltage and three-phase AC current at the grid-connected system port;

[0203] A phase-locked loop transformation is performed on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle. The power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system. The target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system.

[0204] Based on the target system's rotation angle and power angle, the target converter's mode is switched from the first mode to the second mode;

[0205] The current reference value of the target converter in the second mode is obtained, and based on the current reference value, three-phase AC current, DC bus voltage and triangular wave signal, the switching control signal of the target converter is obtained, so as to realize AC-DC conversion based on the switching control signal.

[0206] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0207] The active power and reactive power are determined based on the three-phase AC voltage, three-phase AC current and preset system rotation angle;

[0208] The current reference value is determined based on the active power, active power reference value, reactive power, reactive power reference value, and power angle.

[0209] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0210] Determine the internal potential reference value based on the reactive power and the reactive power reference value;

[0211] The current reference value is determined based on the internal potential reference value, the three-phase AC voltage, and the grid-connected current vector.

[0212] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0213] Determine the two-phase voltage in the synchronous rotating coordinate system based on the three-phase AC voltage and the preset system rotation angle;

[0214] Based on the three-phase AC current and the preset system rotation angle, determine the two-phase current in the synchronous rotating coordinate system;

[0215] The active power and reactive power are determined based on the two-phase voltage and the two-phase current.

[0216] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0217] The active power deviation between the active power and the active power reference value, the reactive power deviation between the reactive power and the reactive power reference value, and the power angle are rotated and transformed to obtain the transformed active power and the transformed reactive power.

[0218] The transformed active power and the transformed reactive power are input to the PI regulator to obtain the current reference value.

[0219] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0220] Determine the duty cycle based on the current reference value and the three-phase AC current;

[0221] Determine the valve-side control voltage based on the duty cycle and DC bus voltage;

[0222] The valve-side control voltage is converted into a three-phase voltage to obtain a three-phase voltage quantity;

[0223] Based on the three-phase voltage and triangular wave, the switching control signal of the target converter is obtained.

[0224] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0225] The three-phase AC voltage and the preset system rotation angle are rotated to obtain the x-axis voltage and y-axis voltage;

[0226] The x-axis voltage is input to the first phase-locked loop for calculation to obtain the rotation angle of the target system.

[0227] The y-axis voltage is input to the second phase-locked loop for calculation to obtain the power angle.

[0228] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, the computer program performing the following steps when executed by a processor:

[0229] Obtain the three-phase AC voltage and three-phase AC current at the grid-connected system port;

[0230] A phase-locked loop transformation is performed on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle. The power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system. The target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system.

[0231] Based on the target system's rotation angle and power angle, the target converter's mode is switched from the first mode to the second mode;

[0232] The current reference value of the target converter in the second mode is obtained, and based on the current reference value, three-phase AC current, DC bus voltage and triangular wave signal, the switching control signal of the target converter is obtained, so as to realize AC-DC conversion based on the switching control signal.

[0233] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0234] The active power and reactive power are determined based on the three-phase AC voltage, three-phase AC current and preset system rotation angle;

[0235] The current reference value is determined based on the active power, active power reference value, reactive power, reactive power reference value, and power angle.

[0236] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0237] Determine the internal potential reference value based on the reactive power and the reactive power reference value;

[0238] The current reference value is determined based on the internal potential reference value, the three-phase AC voltage, and the grid-connected current vector.

[0239] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0240] Determine the two-phase voltage in the synchronous rotating coordinate system based on the three-phase AC voltage and the preset system rotation angle;

[0241] Based on the three-phase AC current and the preset system rotation angle, determine the two-phase current in the synchronous rotating coordinate system;

[0242] The active power and reactive power are determined based on the two-phase voltage and the two-phase current.

[0243] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0244] The active power deviation between the active power and the active power reference value, the reactive power deviation between the reactive power and the reactive power reference value, and the power angle are rotated and transformed to obtain the transformed active power and the transformed reactive power.

[0245] The transformed active power and the transformed reactive power are input to the PI regulator to obtain the current reference value.

[0246] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0247] Determine the duty cycle based on the current reference value and the three-phase AC current;

[0248] Determine the valve-side control voltage based on the duty cycle and DC bus voltage;

[0249] The valve-side control voltage is converted into a three-phase voltage to obtain a three-phase voltage quantity;

[0250] Based on the three-phase voltage and triangular wave, the switching control signal of the target converter is obtained.

[0251] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0252] The three-phase AC voltage and the preset system rotation angle are rotated to obtain the x-axis voltage and y-axis voltage;

[0253] The x-axis voltage is input to the first phase-locked loop for calculation to obtain the rotation angle of the target system.

[0254] The y-axis voltage is input to the second phase-locked loop for calculation to obtain the power angle.

[0255] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, performs the following steps:

[0256] Obtain the three-phase AC voltage and three-phase AC current at the grid-connected system port;

[0257] A phase-locked loop transformation is performed on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle. The power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system. The target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system.

[0258] Based on the target system's rotation angle and power angle, the target converter's mode is switched from the first mode to the second mode;

[0259] The current reference value of the target converter in the second mode is obtained, and based on the current reference value, three-phase AC current, DC bus voltage and triangular wave signal, the switching control signal of the target converter is obtained, so as to realize AC-DC conversion based on the switching control signal.

[0260] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0261] The active power and reactive power are determined based on the three-phase AC voltage, three-phase AC current and preset system rotation angle;

[0262] The current reference value is determined based on the active power, active power reference value, reactive power, reactive power reference value, and power angle.

[0263] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0264] Determine the internal potential reference value based on the reactive power and the reactive power reference value;

[0265] The current reference value is determined based on the internal potential reference value, the three-phase AC voltage, and the grid-connected current vector.

[0266] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0267] Determine the two-phase voltage in the synchronous rotating coordinate system based on the three-phase AC voltage and the preset system rotation angle;

[0268] Based on the three-phase AC current and the preset system rotation angle, determine the two-phase current in the synchronous rotating coordinate system;

[0269] The active power and reactive power are determined based on the two-phase voltage and the two-phase current.

[0270] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0271] The active power deviation between the active power and the active power reference value, the reactive power deviation between the reactive power and the reactive power reference value, and the power angle are rotated and transformed to obtain the transformed active power and the transformed reactive power.

[0272] The transformed active power and the transformed reactive power are input to the PI regulator to obtain the current reference value.

[0273] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0274] Determine the duty cycle based on the current reference value and the three-phase AC current;

[0275] Determine the valve-side control voltage based on the duty cycle and DC bus voltage;

[0276] The valve-side control voltage is converted into a three-phase voltage to obtain a three-phase voltage quantity;

[0277] Based on the three-phase voltage and triangular wave, the switching control signal of the target converter is obtained.

[0278] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0279] The three-phase AC voltage and the preset system rotation angle are rotated to obtain the x-axis voltage and y-axis voltage;

[0280] The x-axis voltage is input to the first phase-locked loop for calculation to obtain the rotation angle of the target system.

[0281] The y-axis voltage is input to the second phase-locked loop for calculation to obtain the power angle.

[0282] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0283] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0284] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A mode switching method for a converter, characterized in that, The method includes: Obtain the three-phase AC voltage and three-phase AC current at the grid-connected system port; A phase-locked loop transformation is performed on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle; the power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system; the target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system; Based on the target system rotation angle and the power angle, the mode of the target converter is switched from the first mode to the second mode; Obtain the current reference value of the target converter in the second mode, and based on the current reference value, the three-phase AC current, the DC bus voltage and the triangular wave signal, obtain the switching control signal of the target converter, so as to realize AC-DC conversion based on the switching control signal.

2. The method according to claim 1, characterized in that, In the first mode being a grid-connected control mode and the second mode being a grid-following control mode, obtaining the current reference value of the target converter in the second mode includes: The active power and reactive power are determined based on the three-phase AC voltage, the three-phase AC current and the preset system rotation angle. The current reference value is determined based on the active power, the active power reference value, the reactive power, the reactive power reference value, and the power angle.

3. The method according to claim 2, characterized in that, In the first mode being grid-connected control mode and the second mode being grid-connected control mode, obtaining the current reference value of the target converter in the second mode includes: Based on the reactive power and the reactive power reference value, determine the internal potential reference value; The current reference value is determined based on the internal potential reference value, the three-phase AC voltage, and the grid-connected current vector.

4. The method according to claim 2, characterized in that, The determination of active power and reactive power based on the three-phase AC voltage, the three-phase AC current, and the preset system rotation angle includes: Based on the three-phase AC voltage and the preset system rotation angle, determine the two-phase voltage in the synchronous rotating coordinate system; Based on the three-phase AC current and the preset system rotation angle, determine the two-phase current in the synchronous rotating coordinate system; The active power and the reactive power are determined based on the two-phase voltage and the two-phase current.

5. The method according to claim 2, characterized in that, The step of determining the current reference value based on the active power, the active power reference value, the reactive power, the reactive power reference value, and the power angle includes: The active power deviation between the active power and the active power reference value, the reactive power deviation between the reactive power and the reactive power reference value, and the power angle are rotated and transformed to obtain the transformed active power and the transformed reactive power. The transformed active power and the transformed reactive power are input to the PI regulator to obtain the current reference value.

6. The method according to claim 1, characterized in that, The process of obtaining the switching control signal of the target converter based on the current reference value, the three-phase AC current, the DC bus voltage, and the triangular wave signal includes: The duty cycle is determined based on the current reference value and the three-phase AC current. The valve-side control voltage is determined based on the duty cycle and DC bus voltage. The valve-side control voltage is converted into a three-phase voltage to obtain a three-phase voltage quantity; Based on the three-phase voltage and the triangular wave, the switching control signal of the target converter is obtained.

7. The method according to claim 1, characterized in that, The step of performing a phase-locked loop transformation on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and power angle includes: The three-phase AC voltage and the preset system rotation angle are rotated to obtain the x-axis voltage and y-axis voltage; The x-axis voltage is input to the first phase-locked loop for calculation to obtain the rotation angle of the target system. The y-axis voltage is input to the second phase-locked loop for calculation to obtain the power angle.

8. A mode switching device for a converter, characterized in that, The device includes: The acquisition module is used to acquire the three-phase AC voltage and three-phase AC current at the grid-connected system port; The transformation module is used to perform a phase-locked loop transformation on the three-phase AC voltage and the preset system rotation angle to obtain the target system rotation angle and the power angle; the power angle is used to characterize the phase angle difference between the voltage vector of the target converter and the voltage vector in the grid-connected system; the target system rotation angle is used to characterize the reference alignment angle between the initial spatial position of the voltage vector of the target converter and the position of the voltage vector in the grid-connected system; The switching module is used to switch the mode of the target converter from the first mode to the second mode according to the rotation angle of the target system and the power angle. The determination module is used to obtain the current reference value of the target converter in the second mode, and based on the current reference value, the three-phase AC current, the DC bus voltage and the triangular wave signal, obtain the switching control signal of the target converter, so as to realize AC-DC conversion based on the switching control signal.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

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