Inverter control method based on virtual synchronous generator and related device thereof

Abstract

This application discloses an inverter control method and related equipment based on a virtual synchronous generator, applicable to the field of electrical control technology. When the grid voltage is abnormal, the active power output of the inverter is controlled to zero, and the reactive power control process of the virtual synchronous generator is switched from the virtual synchronous generator's reactive power loop to a voltage anomaly control loop. In the voltage anomaly control loop, based on the current reactive current output by the virtual synchronous generator and its maximum current limit, the excitation voltage of the virtual synchronous generator is gradually increased, starting from the current grid voltage. This causes the amplitude of the inverter's grid connection point output voltage to gradually increase, and the difference between the grid connection point output voltage amplitude and the grid voltage amplitude to gradually increase, thereby increasing the reactive current output by the inverter. This allows the inverter to output the required reactive current without exceeding the maximum current limit, thus providing reactive power support to the grid and ensuring grid stability.

Description

[0001] This application claims priority to Chinese Patent Application No. 202411318028.X, filed on September 20, 2024, entitled "Inverter Control Method and Related Equipment Based on Virtual Synchronous Generator", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electrical control technology, and in particular to an inverter control method and related equipment based on a virtual synchronous generator. Background Technology

[0003] With the application of distributed renewable energy systems, more and more inverters are being connected to the grid, resulting in a significant reduction in the total damping and inertia provided by traditional generators in the grid. This causes the grid to experience faster frequency changes and a decrease in its anti-interference capability when facing disturbances. To address this issue, the concept of virtual synchronous generator (VSG) control technology has been proposed. This control technology can mimic the operating mechanism of a synchronous generator, suppress frequency and output power fluctuations, and enable the grid-connected inverter corresponding to the virtual synchronous generator to possess grid support, inertial response, and damping characteristics, thereby improving grid voltage amplitude and frequency fluctuations.

[0004] Virtual synchronous generator control technology is a voltage source inverter control technology. The control target is the grid connection point voltage of the inverter. However, short circuit faults and high-low voltage switching can easily cause abnormal grid voltage. At this time, the abnormal feedback voltage of the grid connection point voltage can easily lead to overcurrent of reactive current output by the inverter, causing the inverter to disconnect from the grid and affecting the stability of the grid. Summary of the Invention

[0005] This application provides an inverter control method and related equipment based on a virtual synchronous generator. When the grid voltage is abnormal, the inverter can output the required reactive current without exceeding the maximum current limit to provide reactive power support to the grid and ensure grid stability.

[0006] This application provides an inverter control method based on a virtual synchronous generator, wherein the inverter is in a grid-connected state, including:

[0007] When the grid voltage is normal, the reactive power control process of the virtual synchronous generator is set as the reactive power loop of the virtual synchronous generator, and the excitation voltage of the virtual synchronous generator is output in the reactive power loop of the virtual synchronous generator; the excitation voltage is used to control the grid connection point output voltage of the inverter.

[0008] When an abnormal grid voltage is detected, the active power output of the inverter is controlled to be zero, and the reactive power control process of the virtual synchronous generator is switched from the reactive power loop of the virtual synchronous generator to the voltage abnormality control loop.

[0009] In the voltage anomaly control loop, based on the current reactive current output by the virtual synchronous generator and the maximum current limit of the virtual synchronous generator, the excitation voltage of the virtual synchronous generator is gradually increased starting from the current grid voltage.

[0010] Furthermore, controlling the active power in the active loop of the virtual synchronous generator to zero includes:

[0011] The active power setpoint in the active power loop of the virtual synchronous generator is controlled to be zero, so as to control the active power output of the inverter to be zero.

[0012] Furthermore, the method also includes:

[0013] Detect the reactive current of the virtual synchronous generator and / or the terminal voltage of the virtual synchronous generator;

[0014] Based on the current variation trend of the reactive current, and / or based on the terminal voltage of the virtual synchronous generator, determine whether the grid voltage is abnormal.

[0015] Furthermore, the terminal voltage of the virtual synchronous generator includes the positive sequence terminal voltage value of the virtual synchronous generator;

[0016] Determining whether the grid voltage is abnormal based on the terminal voltage of the virtual synchronous generator includes:

[0017] If the positive sequence voltage value at the generator terminal of the virtual synchronous generator is less than the low-voltage detection voltage threshold of the power grid, or if the positive sequence voltage value at the generator terminal of the virtual synchronous generator is greater than the high-voltage detection voltage threshold of the power grid, then the power grid voltage is determined to be abnormal.

[0018] If the positive sequence voltage value at the generator terminal of the virtual synchronous generator is greater than the low-voltage detection voltage threshold of the power grid and less than the high-voltage detection voltage threshold of the power grid, then the power grid voltage is determined to be normal.

[0019] Furthermore, the step of gradually increasing the excitation voltage of the virtual synchronous generator based on the current reactive current output by the virtual synchronous generator and the maximum current limit of the virtual synchronous generator, starting from the current grid voltage, includes:

[0020] The current difference is obtained by subtracting the current reactive current of the virtual synchronous generator from its maximum limiting current.

[0021] Starting with the amplitude of the current grid voltage, the current difference is integrated and superimposed on the amplitude of the current grid voltage, and then the process is returned to execute: the step of subtracting the current reactive current of the virtual synchronous generator from the maximum current limit of the virtual synchronous generator to obtain the current difference is repeated until the current reactive current is equal to the maximum current limit, or the amplitude of the superimposed current grid voltage is equal to the rated voltage of the virtual synchronous generator.

[0022] Based on the amplitude of the superimposed current grid voltage, the excitation voltage of the virtual synchronous generator is gradually increased.

[0023] Furthermore, the step of gradually increasing the excitation voltage of the virtual synchronous generator based on the amplitude of the superimposed current grid voltage includes:

[0024] Based on the formula: Gradually increase the excitation voltage E of the virtual synchronous generator, where, The summation is the current grid voltage, where |U| is the amplitude of the current grid voltage, K is the adjustment coefficient, and I... max I is the maximum limiting current of the virtual synchronous generator. fdb U represents the current reactive current of the virtual synchronous generator. rated The rated voltage of the virtual synchronous generator is denoted by 'min', which indicates taking the minimum value.

[0025] Furthermore, the method also includes:

[0026] When the reactive current output by the virtual synchronous generator is the maximum current limit, and the grid voltage still does not return to normal after a preset output time, the inverter is controlled to switch from grid-connected state to grid-off state.

[0027] This application embodiment also provides an inverter control device based on a virtual synchronous generator, wherein the inverter is in a grid-connected state, including:

[0028] The first control unit is used to set the reactive power control process of the virtual synchronous generator as the reactive power loop of the virtual synchronous generator when the grid voltage is normal, and output the excitation voltage of the virtual synchronous generator in the reactive power loop of the virtual synchronous generator; the excitation voltage is used to control the grid connection point output voltage of the inverter.

[0029] When the second control unit detects an abnormal grid voltage, it controls the active power output of the inverter to zero and switches the reactive power control process of the virtual synchronous generator from the reactive power loop of the virtual synchronous generator to the voltage abnormality control loop.

[0030] The regulating unit is used in the voltage anomaly control loop to gradually increase the excitation voltage of the virtual synchronous generator, starting from the current grid voltage, based on the current reactive current output by the virtual synchronous generator and the maximum current limit of the virtual synchronous generator.

[0031] This application also provides an inverter control device based on a virtual synchronous generator, including:

[0032] Central processing unit, memory, input / output interface, wired or wireless network interface, power supply;

[0033] The memory is either a short-term storage memory or a persistent storage memory;

[0034] The central processing unit is configured to communicate with the memory and execute instructions in the memory on a control plane functional entity to perform the methods described above.

[0035] This application also provides a computer-readable storage medium including instructions that, when executed on a computer, cause the computer to perform the method described above.

[0036] This application embodiment also provides a grid-connected inverter. When the grid-connected inverter is in grid-connected state, the above-mentioned inverter control method based on virtual synchronous generator is used to control the grid-connected inverter.

[0037] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:

[0038] In this embodiment, when the grid voltage is abnormal, the active power output of the inverter is controlled to zero, so that the inverter only outputs reactive power. Furthermore, for the reactive power output of the inverter, the reactive power control process of the virtual synchronous generator is switched from the virtual synchronous generator's reactive power loop to a voltage anomaly control loop. In the voltage anomaly control loop, based on the current reactive current output by the virtual synchronous generator and its maximum current limit, the excitation voltage of the virtual synchronous generator is gradually increased, starting from the current grid voltage. This excitation voltage is used to control the inverter's grid connection point output voltage, causing the amplitude of the inverter's grid connection point output voltage to gradually increase, and the difference between the grid connection point output voltage amplitude and the grid voltage amplitude to gradually increase. This increases the reactive current output by the inverter, enabling it to output the required reactive current without exceeding the maximum current limit, thus providing reactive power support to the grid, ensuring grid stability, and effectively preventing the inverter from disconnecting from the grid due to overcurrent of the reactive current output. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0040] Figure 1 This is a structural block diagram of a virtual synchronous generator disclosed in an embodiment of this application;

[0041] Figure 2 This is a flowchart of an inverter control based on a virtual synchronous generator disclosed in an embodiment of this application;

[0042] Figure 3 This is a structural block diagram of an embodiment of the present application that includes an added voltage anomaly control loop;

[0043] Figure 4 This is an abnormal waveform diagram of zero-crossing of a far-end voltage disclosed in an embodiment of this application;

[0044] Figure 5 This is another abnormal waveform diagram of zero-crossing of the far-end voltage disclosed in an embodiment of this application;

[0045] Figure 6 This is a diagram of an inverter control device based on a virtual synchronous generator disclosed in an embodiment of this application;

[0046] Figure 7 This is a diagram of another inverter control device based on a virtual synchronous generator disclosed in an embodiment of this application. Detailed Implementation

[0047] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0048] In the description of the embodiments of this application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0049] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0050] Existing grid-connected inverters often employ virtual synchronous generator control, with the control target being the inverter's grid connection point voltage. However, short-circuit faults and high-low voltage switching can easily cause grid voltage anomalies. In such cases, abnormal grid connection point voltage feedback can lead to overcurrent of reactive current output by the inverter, causing it to disconnect from the grid and affecting grid stability. Therefore, this application provides an inverter control method based on a virtual synchronous generator, enabling the inverter to output the required reactive current without exceeding the maximum current limit, thus providing reactive power support to the grid and ensuring grid stability. Figure 2 As shown, the specific steps are as follows:

[0051] 201. When the grid voltage is normal, the reactive power loop based on the virtual synchronous generator outputs the excitation voltage of the virtual synchronous generator.

[0052] In this embodiment, an inverter is controlled based on a virtual synchronous generator, and the inverter is in a grid-connected state. When the grid voltage is normal, the reactive power control process of the virtual synchronous generator is set as a reactive power loop of the virtual synchronous generator, and the excitation voltage of the virtual synchronous generator is output in the reactive power loop of the virtual synchronous generator. Specifically, the structure of the virtual synchronous generator is as follows: Figure 1 As shown, the power loop of the virtual synchronous generator includes an active power loop and a reactive power loop. Frequency regulation control is performed in the active power loop, and voltage regulation control is performed in the reactive power loop. The corresponding control equations for the power loop are:

[0053]

[0054] Among them, P ref and P e Q represents the active power command (i.e., the given active power) and the actual active power output of the virtual synchronous generator; ref and Q e These are the reactive power command (i.e., the given reactive power) output by the virtual synchronous generator and the actual reactive power output, respectively; ω o ω n U n and U oThese are the voltage frequency value and rated voltage frequency value output by the virtual synchronous generator, the grid output voltage amplitude and the grid rated voltage amplitude, respectively; D, J, k q k u These are the frequency damping coefficient, virtual inertia coefficient, voltage droop coefficient, and reactive inertia coefficient of the virtual synchronous generator, respectively; θ ref E is the phase angle of the active loop output; E is the excitation voltage of the reactive loop output of the virtual synchronous generator; and E0 is the no-load electromotive force.

[0055] The excitation voltage E of the virtual synchronous generator is used to control the grid connection point voltage of the inverter. It can be understood that the excitation voltage E of the virtual synchronous generator is a reference voltage. The grid connection point reference voltage of the inverter can be obtained through the excitation voltage E and the phase angle output by the active power loop. The grid connection point reference voltage is: ua_ref=E*sin(θ) ref ), ub_ref=E*sin(θ) ref -2 / 3π), uc_ref=E*sin(θ) ref +2 / 3π). Next, closed-loop control can be performed based on the grid connection point reference voltage to make the actual grid connection point voltage of the inverter approach or equal to that grid connection point reference voltage.

[0056] It is understandable that when there is a short-circuit fault in the power grid and voltage anomalies caused by high-voltage switching and low-voltage switching, the reactive power can be obtained as follows:

[0057]

[0058] Among them, V A V is the terminal voltage of the virtual synchronous generator. B Q is the remote voltage (i.e., grid voltage) of the virtual synchronous generator. A Let δ be the reactive power, R be the power angle, and X be the grid impedance and inductive reactance. It can be seen that when the grid voltage is abnormal, the reactive power will suddenly increase, causing overcurrent in the inverter and grid instability.

[0059] Similarly, for active power, we can obtain:

[0060]

[0061] P A Given the active power, it can be seen that when the grid voltage is abnormal, the same active power requires a larger power angle. If this is not limited, it is easy to cause power angle instability, leading to tripping (i.e., the grid-connected inverter disconnects from the grid).

[0062] In this embodiment of the application, the stability of the power grid will be ensured when the power grid voltage is abnormal through the following steps 202 and 204.

[0063] 202. When an abnormal grid voltage is detected, the active power output of the inverter is controlled to be zero.

[0064] In this embodiment, the inverter is in grid-connected mode. When an abnormal grid voltage is detected, the active power output of the inverter can be controlled to zero. It can be understood that when the grid voltage is abnormal, by controlling the active power output of the inverter to zero, the inverter only outputs reactive power. This allows the reactive power control process of the virtual synchronous generator to stably transition from the reactive power loop to the voltage anomaly control loop when the grid voltage is abnormal, thus enabling the virtual synchronous generator to have stable transition capability.

[0065] Specifically, such as Figure 3 As shown, the active power setpoint in the active power loop of the virtual synchronous generator can be controlled to zero, and the difference between the phase angle of the active power loop output and the phase angle of the grid is zero, so as to control the active power output of the inverter to zero and avoid power angle instability.

[0066] 203. Switch the reactive power control process of the virtual synchronous generator from the reactive power loop to the voltage anomaly control loop.

[0067] In this embodiment of the application, a voltage anomaly control loop is added to the structure of the virtual synchronous generator. The final output of the voltage anomaly control loop and the reactive power loop of the virtual synchronous generator are both the excitation voltage of the virtual synchronous generator. The voltage anomaly control loop is used to provide reactive power support to the power grid through the reactive current output by the virtual synchronous generator when the grid voltage is abnormal.

[0068] When an abnormal grid voltage is detected, the reactive power control process of the virtual synchronous generator is switched from the reactive power loop to the voltage abnormality control loop, that is, the excitation voltage of the virtual synchronous generator is switched to be output by the voltage abnormality control loop.

[0069] 204. Based on the current reactive current output by the virtual synchronous generator and the maximum current limit of the virtual synchronous generator, gradually increase the excitation voltage of the virtual synchronous generator starting from the current grid voltage.

[0070] In the voltage anomaly control loop, the current grid voltage, the current reactive current output by the virtual synchronous generator, and the maximum current limit of the virtual synchronous generator can be input. Based on the current reactive current output by the virtual synchronous generator and the maximum current limit of the virtual synchronous generator, the excitation voltage of the virtual synchronous generator is gradually increased starting from the current grid voltage. That is, the excitation voltage of the virtual synchronous generator output by the voltage anomaly control loop is gradually increased to increase the grid connection point output voltage of the inverter, thereby increasing the reactive current output by the inverter. This allows the inverter to output the required reactive current without exceeding the maximum current limit to achieve reactive power support for the grid.

[0071] Specifically, the current difference can be obtained by subtracting the current reactive current of the virtual synchronous generator from its maximum current limit. Starting with the amplitude of the current grid voltage, the current difference is integrated and added to the amplitude of the current grid voltage. This process is repeated until the current reactive current equals the maximum current limit, or the amplitude of the current grid voltage equals the rated voltage of the virtual synchronous generator. In other words, starting from the current grid voltage, the current difference (subtracting the current reactive current from the maximum current limit) is integrated and added to the amplitude of the current grid voltage until the current reactive current equals the maximum current limit, or the amplitude of the current grid voltage equals the rated voltage of the virtual synchronous generator. For various grid voltage anomalies such as short-circuit faults and high / low voltage crossovers, the inverter's reactive current can be quickly limited, with a fast current-limiting response, effectively preventing the inverter from disconnecting from the grid due to overcurrent of reactive current.

[0072] Next, the excitation voltage of the virtual synchronous generator can be gradually increased based on the amplitude of the superimposed current grid voltage. Specifically, the amplitude of the superimposed current grid voltage can be compared with the rated voltage of the virtual synchronous generator, and the minimum value can be taken as the excitation voltage of the virtual synchronous generator.

[0073] Correspondingly, the control equation for the voltage anomaly control loop is:

[0074]

[0075] Where E is the excitation voltage of the virtual synchronous generator. The summation of the current grid voltage, |U| represents the amplitude of the current grid voltage, K is the adjustment coefficient, and I... max I is the maximum current limit for the virtual synchronous generator. fdb U represents the current reactive current of the virtual synchronous generator. rated The rated voltage of the virtual synchronous generator is given by 'min', which represents the minimum value. Based on the control equations corresponding to the voltage anomaly control loop, the excitation voltage E of the virtual synchronous generator is gradually increased.

[0076] As can be seen, in this embodiment, when the grid voltage is abnormal, the active power output of the inverter is controlled to zero, so that the inverter only outputs reactive power. Furthermore, for the reactive power output of the inverter, the reactive power control process of the virtual synchronous generator is switched from the virtual synchronous generator's reactive power loop to a voltage anomaly control loop. In the voltage anomaly control loop, based on the current reactive current output by the virtual synchronous generator and the maximum current limit of the virtual synchronous generator, the excitation voltage of the virtual synchronous generator is gradually increased, starting from the current grid voltage. This excitation voltage is used to control the inverter's grid connection point output voltage, causing the amplitude of the inverter's grid connection point output voltage to gradually increase, and the difference between the amplitude of the grid connection point output voltage and the grid voltage amplitude to gradually increase. This increases the reactive current output by the inverter, enabling the inverter to output the required reactive current without exceeding the maximum current limit to achieve reactive power support for the grid, ensuring grid stability, and effectively preventing the inverter from disconnecting from the grid due to overcurrent of the reactive current output by the inverter.

[0077] Understandably, when the grid voltage is normal, the excitation voltage of the virtual synchronous generator can be directly output through the reactive power loop of the virtual synchronous generator without affecting the virtual synchronous generator itself or its overall control process. The control approach is clear, and system resource consumption is low. During periods of voltage anomalies, the grid-connected inverter corresponding to the virtual synchronous generator can still maintain the voltage source characteristics of the virtual synchronous generator, without changing the overall system control attributes. This allows it to provide overload reactive power support to the grid without altering the voltage source.

[0078] Furthermore, in this embodiment, when the grid voltage is abnormal (i.e., the remote voltage of the virtual synchronous generator is abnormal), two situations may occur: an increase in the reactive current of the virtual synchronous generator and an abnormal terminal voltage of the virtual synchronous generator. Generally, sampling can only collect the reactive current and terminal voltage of the virtual synchronous generator. At this time, the reactive current and / or terminal voltage of the virtual synchronous generator can be detected. Based on the current change trend of the reactive current and / or based on the terminal voltage of the virtual synchronous generator, it is determined whether the grid voltage is abnormal. That is, when the current change trend of the reactive current is that the current rise rate is greater than a preset rise threshold, and / or the terminal voltage is outside the grid crossing range, the grid voltage is determined to be abnormal. The preset rise threshold can be an average current increment of 15A or 20A per second, which is not limited here. The terminal voltage being outside the grid crossing range means that the positive sequence voltage value of the terminal is less than the grid low-pass fault detection voltage threshold, or the positive sequence voltage value of the terminal is greater than the grid high-pass fault detection voltage threshold.

[0079] Specifically, the terminal voltage of the virtual synchronous generator includes its positive-sequence voltage value. Based on the virtual synchronous generator's terminal voltage, determining whether the grid voltage is abnormal can be as follows: If the virtual synchronous generator's positive-sequence voltage value is less than the grid low-voltage fault detection voltage threshold, or greater than the grid high-voltage fault detection voltage threshold, indicating a grid voltage anomaly, the reactive power control process of the virtual synchronous generator is switched from the reactive power loop to the voltage anomaly control loop, enabling it to provide reactive power support to the grid while navigating through the grid voltage anomaly. If the virtual synchronous generator's positive-sequence voltage value is greater than the grid low-voltage fault detection voltage threshold but less than the grid high-voltage fault detection voltage threshold, indicating a normal grid voltage, the reactive power control process of the virtual synchronous generator is switched to the reactive power loop.

[0080] The corresponding governing equations are:

[0081]

[0082]

[0083] Among them, U d_pos This is the positive sequence voltage value at the machine terminal; U LVRT U is the voltage threshold for detecting low-voltage faults in the power grid. HVRT This is the voltage threshold for detecting high-voltage faults in the power grid. When the power grid voltage is abnormal, it can quickly adapt to the terminal voltage of the virtual synchronous generator (i.e., the corresponding grid-connected inverter port voltage), and control the overcurrent phenomenon under abnormal power grid voltage conditions through voltage self-adaptation, thereby achieving the purpose of supporting the power grid under abnormal power grid voltage conditions.

[0084] Furthermore, the control process of the virtual synchronous generator mentioned in the embodiments of this application can be simulated on the three-phase energy storage converter, and the virtual synchronous generator can be fully loaded and connected to the grid. The remote voltage zero-breakdown test can be performed under the conditions of short-circuit capacity ratio of SCR2.0 and SCR10.0 respectively. The zero-breakdown voltage fault lasts for three minutes to test the control performance.

[0085] When the short-circuit capacity ratio is SCR2.0, the power grid is relatively weak. At this time, within the allowable current capacity of the virtual synchronous generator, it is sufficient to support the generator terminal voltage to the rated voltage. When the power grid voltage becomes abnormal, the virtual synchronous generator outputs reactive current according to reactive power demand, which can support the power grid voltage to its rated value. The reactive current output by the virtual synchronous generator, not exceeding its maximum current, can support the power grid voltage; that is, the reactive current output by the inverter can support the power grid voltage. For example... Figure 4 As shown in the figure, line 1 represents the positive sequence voltage value at the generator terminal, line 2 represents the reactive power, line 3 represents the active power, and line 4 represents the reactive current value.

[0086] Specifically, when the virtual synchronous generator's terminal voltage cannot be supported to its rated voltage within its allowable current capacity, and the grid voltage becomes abnormal, the reactive current output by the virtual synchronous generator will be the maximum limited current. If the reactive current output by the virtual synchronous generator is the maximum limited current, and the grid voltage still does not return to normal after a preset output time, the inverter will be switched from grid-connected state to grid-off state (i.e., inverter protection shutdown). This ensures the reactive current support capacity of the grid-connected virtual synchronous generator (grid-connected inverter) under abnormal grid voltage conditions, corresponding to the preset output time. The preferred preset output time is 10 seconds.

[0087] For example, when the short-circuit capacity ratio is SCR2.0, such as Figure 5 As shown in the diagram, line 1 represents the positive sequence voltage value at the generator terminal, line 2 represents reactive power, line 3 represents active power, and line 4 represents reactive current. When the short-circuit capacity ratio is SCR2.0, the grid is relatively strong. Under abnormal grid voltage conditions, more reactive current is needed to support the grid voltage. The reactive current output by the virtual synchronous generator will exceed the maximum current limit, and the virtual synchronous generator cannot support the grid voltage. At this time, the reactive current output by the virtual synchronous generator is the maximum current limit (where the maximum current limit is 3 times the rated current). If the grid voltage has not recovered after 10 seconds of output, the inverter is controlled to disconnect from the grid. This achieves the reactive current support capability for 10 seconds under abnormal grid voltage conditions when the grid-connected inverter is in grid-connected state. When the grid voltage cannot be supported, the maximum power output capability of the grid-connected inverter can be maintained, ensuring the maximum grid support capability that the grid-connected inverter can obtain.

[0088] This application also provides an inverter control device based on a virtual synchronous generator, wherein the inverter is in a grid-connected state, such as... Figure 6 As shown, it includes:

[0089] The first control unit 601 is used to set the reactive power control process of the virtual synchronous generator as the reactive power loop of the virtual synchronous generator when the grid voltage is normal, and output the excitation voltage of the virtual synchronous generator in the reactive power loop of the virtual synchronous generator; the excitation voltage is used to control the grid connection point output voltage of the inverter.

[0090] The second control unit 602 is used to control the active power output of the inverter to zero when an abnormal grid voltage is detected, and to switch the reactive power control process of the virtual synchronous generator from the reactive power loop of the virtual synchronous generator to the voltage abnormality control loop.

[0091] The regulating unit 603 is used in the voltage anomaly control loop to gradually increase the excitation voltage of the virtual synchronous generator, starting from the current grid voltage, based on the current reactive current output by the virtual synchronous generator and the maximum current limit of the virtual synchronous generator.

[0092] This application also provides an inverter control device 700 based on a virtual synchronous generator, such as... Figure 7 As shown, the inverter control device 700 of this application embodiment may include one or more central processing units (CPUs) 701 and a memory 702, wherein the memory 702 stores one or more application programs or data.

[0093] The memory 702 can be volatile or persistent storage. The program stored in the memory 702 can include one or more modules, each module including a series of instruction operations on the electronic device. Furthermore, the central processing unit 701 can be configured to communicate with the memory 702 and execute the series of instruction operations in the memory 702 on the inverter control device 700.

[0094] The inverter control unit 700 may also include one or more power supplies 705, one or more wired or wireless network interfaces 704, one or more input / output interfaces 703, and / or one or more operating systems, such as Windows Server™, Mac OS X™, Unix™, Linux™, FreeBSD™, etc.

[0095] The central processing unit 701 can perform the operations performed in any of the aforementioned specific method embodiments, which will not be described in detail here.

[0096] This application embodiment also provides a grid-connected inverter. When the grid-connected inverter is in grid-connected state, the above-mentioned inverter control method based on virtual synchronous generator is used to control the grid-connected inverter.

[0097] This application also provides a computer-readable storage medium including instructions that, when executed on a computer, cause the computer to perform the method described above.

[0098] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0099] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0100] The units described as separate components may or may not be physically separate. The 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 the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0101] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0102] If the integrated unit 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 this application, in essence, or the part that contributes to the prior art, or all or part 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 to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

Claims

1. An inverter control method based on a virtual synchronous generator, wherein the inverter is in a grid-connected state, characterized in that, include: When the grid voltage is normal, the reactive power control process of the virtual synchronous generator is set as the reactive power loop of the virtual synchronous generator, and the excitation voltage of the virtual synchronous generator is output in the reactive power loop of the virtual synchronous generator; the excitation voltage is used to control the grid connection point output voltage of the inverter. When an abnormal grid voltage is detected, the active power output of the inverter is controlled to be zero, and the reactive power control process of the virtual synchronous generator is switched from the reactive power loop of the virtual synchronous generator to the voltage abnormality control loop. In the voltage anomaly control loop, based on the current reactive current output by the virtual synchronous generator and the maximum current limit of the virtual synchronous generator, the excitation voltage of the virtual synchronous generator is gradually increased starting from the current grid voltage. The step of gradually increasing the excitation voltage of the virtual synchronous generator, starting from the current grid voltage, based on the current reactive current output by the virtual synchronous generator and the maximum current limit of the virtual synchronous generator, includes: The current difference is obtained by subtracting the current reactive current of the virtual synchronous generator from its maximum limiting current. Starting with the amplitude of the current grid voltage, the current difference is integrated and superimposed on the amplitude of the current grid voltage, and then the process is returned to execute: the step of subtracting the current reactive current of the virtual synchronous generator from the maximum current limit of the virtual synchronous generator to obtain the current difference is repeated until the current reactive current is equal to the maximum current limit, or the amplitude of the superimposed current grid voltage is equal to the rated voltage of the virtual synchronous generator. Based on the amplitude of the superimposed current grid voltage, the excitation voltage of the virtual synchronous generator is gradually increased; The step of gradually increasing the excitation voltage of the virtual synchronous generator based on the amplitude of the superimposed current grid voltage includes: Based on the control equations corresponding to the voltage anomaly control loop: Gradually increase the excitation voltage of the virtual synchronous generator. ,in, The summation represents the current grid voltage, where... Where K is the amplitude of the current grid voltage, and K is the adjustment coefficient. The maximum current limit for the virtual synchronous generator. The current reactive current of the virtual synchronous generator. The rated voltage of the virtual synchronous generator is denoted by 'min', which indicates taking the minimum value.

2. The inverter control method according to claim 1, characterized in that, The step of controlling the active power in the active loop of the virtual synchronous generator to zero includes: The active power setpoint in the active power loop of the virtual synchronous generator is controlled to be zero, so as to control the active power output of the inverter to be zero.

3. The inverter control method according to claim 1, characterized in that, The method further includes: Detect the reactive current of the virtual synchronous generator and / or the terminal voltage of the virtual synchronous generator; Based on the current variation trend of the reactive current, and / or based on the terminal voltage of the virtual synchronous generator, determine whether the grid voltage is abnormal.

4. The inverter control method according to claim 3, characterized in that, The terminal voltage of the virtual synchronous generator includes the positive sequence terminal voltage value of the virtual synchronous generator; Determining whether the grid voltage is abnormal based on the terminal voltage of the virtual synchronous generator includes: If the positive sequence voltage value at the generator terminal of the virtual synchronous generator is less than the low-voltage detection voltage threshold of the power grid, or if the positive sequence voltage value at the generator terminal of the virtual synchronous generator is greater than the high-voltage detection voltage threshold of the power grid, then the power grid voltage is determined to be abnormal. If the positive sequence voltage value at the generator terminal of the virtual synchronous generator is greater than the low-voltage detection voltage threshold of the power grid and less than the high-voltage detection voltage threshold of the power grid, then the power grid voltage is determined to be normal.

5. The inverter control method according to claim 1, characterized in that, The method further includes: When the reactive current output by the virtual synchronous generator is the maximum current limit, and the grid voltage still does not return to normal after a preset output time, the inverter is controlled to switch from grid-connected state to grid-off state.

6. An inverter control device based on a virtual synchronous generator, wherein the inverter is in a grid-connected state, characterized in that, include: The first control unit is used to set the reactive power control process of the virtual synchronous generator as the reactive power loop of the virtual synchronous generator when the grid voltage is normal, and output the excitation voltage of the virtual synchronous generator in the reactive power loop of the virtual synchronous generator; the excitation voltage is used to control the grid connection point output voltage of the inverter. The second control unit is used to control the active power output of the inverter to zero when an abnormal grid voltage is detected, and to switch the reactive power control process of the virtual synchronous generator from the reactive power loop of the virtual synchronous generator to the voltage abnormality control loop. The regulating unit is used in the voltage anomaly control loop to gradually increase the excitation voltage of the virtual synchronous generator, starting from the current grid voltage, based on the current reactive current output by the virtual synchronous generator and the maximum current limit of the virtual synchronous generator. The regulating unit is specifically used to subtract the current reactive current of the virtual synchronous generator from the maximum current limit of the virtual synchronous generator to obtain the current difference; Starting with the amplitude of the current grid voltage, the current difference is integrated and superimposed onto the amplitude of the current grid voltage, and the process returns to execute: the step of subtracting the current reactive current of the virtual synchronous generator from its maximum limiting current to obtain the current difference, until the current reactive current equals the maximum limiting current, or the amplitude of the superimposed current grid voltage equals the rated voltage of the virtual synchronous generator; based on the amplitude of the superimposed current grid voltage, the excitation voltage of the virtual synchronous generator is gradually increased; wherein, the adjustment unit is further used to, Based on the control equations corresponding to the voltage anomaly control loop: Gradually increase the excitation voltage of the virtual synchronous generator. ,in, The summation represents the current grid voltage, where... Where K is the amplitude of the current grid voltage, and K is the adjustment coefficient. The maximum current limit for the virtual synchronous generator. The current reactive current of the virtual synchronous generator. The rated voltage of the virtual synchronous generator is denoted by 'min', which indicates taking the minimum value.

7. An inverter control device based on a virtual synchronous generator, characterized in that, include: Central processing unit, memory, input / output interface, wired or wireless network interface, power supply; The memory is either a short-term storage memory or a persistent storage memory; The central processing unit is configured to communicate with the memory and execute instructions in the memory on a control plane functional entity to perform the method described in any one of claims 1 to 5.

8. A grid-connected inverter, characterized in that, When the grid-connected inverter is in grid-connected state, the inverter control method based on a virtual synchronous generator as described in any one of claims 1 to 5 is used to control the grid-connected inverter.

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