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

Abstract

The embodiment of the invention discloses an inverter control method based on a virtual synchronous generator and related equipment thereof, and belongs to the technical field of electrical control. When the voltage of the power grid is abnormal, active power output of an inverter is controlled to be zero, and the reactive power control process of the virtual synchronous generator is switched from a reactive power ring of the virtual synchronous generator to a voltage abnormity control ring; in the voltage abnormity control loop, based on the current reactive current output by the virtual synchronous generator and the limited maximum current of the virtual synchronous generator, the excitation voltage of the virtual synchronous generator is gradually increased by taking the current power grid voltage as an initial value; the output voltage amplitude of the grid-connected point of the inverter is gradually increased, and the difference value between the output voltage amplitude of the grid-connected point and the voltage amplitude of the power grid is gradually increased, so that the reactive current output by the inverter is increased, and the inverter can output the required reactive current on the basis of not exceeding the limited maximum current so as to realize reactive support for the power grid. The power grid stability is ensured.

Description

[0001] This application claims the priority of the Chinese patent application filed with the China Patent Office on September 20, 2024, with application number 202411318028.X and invention name “Inverter control method based on virtual synchronous generator and related equipment”, the entire contents of which are incorporated by reference in this application. Technical Field

[0002] The embodiments of the present application relate to the field of electrical control technology, and in particular to an inverter control method based on a virtual synchronous generator and related equipment. Background Art

[0003] With the application of distributed new energy systems, more and more inverters are connected to the power grid, resulting in a significant reduction in the total damping and total inertia provided by traditional generators in the power grid, which makes the frequency change faster and the anti-interference ability decrease when the power grid faces disturbances. In order to solve this problem, the concept of virtual synchronous generator (VSG) control technology is proposed. This control technology can imitate the operation mechanism of synchronous generators, suppress the fluctuation of frequency and output power, and enable the grid-connected inverter corresponding to the virtual synchronous generator to have grid support, inertia response and damping characteristics, thereby improving the voltage amplitude and frequency fluctuation of the power grid.

[0004] Virtual synchronous generator control technology is a voltage source inverter control technology. The control target is the grid-connected point voltage of the inverter. Short-circuit faults and high-low wear in the power grid can easily cause abnormal grid voltage. At this time, the grid-connected point voltage feedback voltage is abnormal, which can easily lead to overcurrent of reactive current output by the inverter, causing the inverter to be disconnected from the grid and affecting the stability of the power grid. Summary of the invention

[0005] The embodiments of the present application provide an inverter control method based on a virtual synchronous generator and related equipment thereof, which can enable the inverter to output the required reactive current without exceeding the maximum current limit to achieve reactive support for the grid and ensure grid stability when the grid voltage is abnormal.

[0006] The embodiment of the present application provides an inverter control method based on a virtual synchronous generator, wherein the inverter is in a grid-connected state, comprising:

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

[0008] When a grid voltage anomaly 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 anomaly control loop;

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

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

[0011] The active power set value in the active 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 further comprises:

[0013] Detecting 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, it is determined whether the grid voltage is abnormal.

[0015] Further, the terminal voltage of the virtual synchronous generator includes a terminal positive sequence 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 machine end of the virtual synchronous generator is less than the grid low-through fault detection voltage threshold, or the positive sequence voltage value at the machine end of the virtual synchronous generator is greater than the grid high-through fault detection voltage threshold, it is determined that the grid voltage is abnormal;

[0018] If the positive sequence voltage value at the machine end of the virtual synchronous generator is greater than the grid low-through fault detection voltage threshold and less than the grid high-through fault detection voltage threshold, it is determined that the grid voltage is normal.

[0019] Further, based on the current reactive current output by the virtual synchronous generator and the limited maximum current of the virtual synchronous generator, gradually increasing the excitation voltage of the virtual synchronous generator with the current grid voltage as the starting value includes:

[0020] Subtracting the current reactive current of the virtual synchronous generator from the limited maximum current of the virtual synchronous generator to obtain a current difference;

[0021] Taking the amplitude of the current grid voltage as the starting value, integrating the current difference and superimposing it on the amplitude of the current grid voltage, and returning to execute: subtracting the current reactive current of the virtual synchronous generator from the limited maximum current of the virtual synchronous generator to obtain the current difference step, until the current reactive current is equal to the limited maximum current, 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: The excitation voltage E of the virtual synchronous generator is gradually increased, wherein: is the current grid voltage after superposition, where |U| is the amplitude of the current grid voltage, K is the adjustment coefficient, and I max is the maximum current limit of the virtual synchronous generator, I fdb is the current reactive current of the virtual synchronous generator, U rated is the rated voltage of the virtual synchronous generator, and min represents the minimum value.

[0025] Furthermore, the method further comprises:

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

[0027] The embodiment of the present application further provides an inverter control device based on a virtual synchronous generator, wherein the inverter is in a grid-connected state, comprising:

[0028] A first control unit is used to set the reactive power control process of the virtual synchronous generator to the reactive 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 loop of the virtual synchronous generator; the excitation voltage is used to control the grid-connected point output voltage of the inverter;

[0029] When the grid voltage is abnormal, the second control unit controls the active power output of the inverter to be 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 to gradually increase the excitation voltage of the virtual synchronous generator in the voltage anomaly control loop based on the current reactive current output by the virtual synchronous generator and the limited maximum current of the virtual synchronous generator, taking the current grid voltage as the starting value.

[0031] The embodiment of the present application further provides an inverter control device based on a virtual synchronous generator, comprising:

[0032] CPU, memory, input and output interface, wired or wireless network interface, power supply;

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

[0034] The central processor is configured to communicate with the memory, and execute the instruction operation in the memory on the control plane function entity to perform the above method.

[0035] An embodiment of the present application further provides a computer-readable storage medium, wherein the computer-readable storage medium includes instructions. When the instructions are executed on a computer, the computer executes the method described above.

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

[0037] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0038] In an embodiment of the present application, 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, and for the reactive output part of the inverter, the reactive power control process of the virtual synchronous generator is switched from the reactive loop of the virtual synchronous generator to the voltage abnormality control loop; in the voltage abnormality control loop, based on the current reactive current output by the virtual synchronous generator and the limited maximum current of the virtual synchronous generator, the excitation voltage of the virtual synchronous generator is gradually increased with the current grid voltage as the starting value, and the excitation voltage is used to control the grid-connected point output voltage of the inverter, so that the grid-connected point output voltage amplitude of the inverter gradually increases and the difference between the grid-connected point output voltage amplitude and the grid voltage amplitude gradually increases, thereby increasing the reactive current output by the inverter, so that the inverter can output the required reactive current on the basis of not exceeding the limited maximum current to achieve reactive support for the grid, ensure the stability of the grid, and effectively avoid the problem of the inverter being disconnected from the grid due to overcurrent of the reactive current output by the inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0040] Figure 1 A structural block diagram of a virtual synchronous generator disclosed in an embodiment of the present application;

[0041] Figure 2 An inverter control flow chart based on a virtual synchronous generator disclosed in an embodiment of the present application;

[0042] Figure 3 A structural block diagram of adding a voltage abnormality control loop disclosed in an embodiment of the present application;

[0043] Figure 4 An abnormal waveform diagram of a remote voltage zero penetration disclosed in an embodiment of the present application;

[0044] Figure 5 It is another abnormal waveform diagram of remote voltage zero penetration disclosed in the embodiment of the present application;

[0045] Figure 6 A diagram of an inverter control device based on a virtual synchronous generator disclosed in an embodiment of the present application;

[0046] Figure 7 This is a diagram of another inverter control device based on a virtual synchronous generator disclosed in an embodiment of the present application. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0048] In the description of the embodiments of the present application, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the embodiments of the present application.

[0049] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0050] Existing grid-connected inverters often use virtual synchronous generator control, and the control target is the grid-connected point voltage of the inverter. However, due to short-circuit faults and high-low wear in the power grid, the grid voltage is easily abnormal. At this time, the grid-connected point voltage feedback voltage is abnormal, which can easily cause the reactive current output by the inverter to overcurrent, causing the inverter to be disconnected from the grid, affecting the stability of the power grid. Therefore, the embodiment of the present application provides an inverter control method based on a virtual synchronous generator, which can enable the inverter to output the required reactive current on the basis of not exceeding the maximum current limit to achieve reactive support for the power grid and ensure the stability of the power grid, such as Figure 2 As shown, the specific steps are as follows:

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

[0052] In the embodiment of the present application, the inverter is controlled based on the 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 the reactive loop of the virtual synchronous generator, and the excitation voltage of the virtual synchronous generator is output in the reactive 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 loop and a reactive loop. Frequency regulation control is performed in the active loop, and voltage regulation control is performed in the reactive loop. The control equation of the corresponding power loop is:

[0053]

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

[0055] Among them, the excitation voltage E of the virtual synchronous generator is used to control the grid-connected 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-connected point reference voltage of the inverter can be obtained by the excitation voltage E and the phase angle of the active loop output. The grid-connected 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). Then, closed-loop control can be performed based on the grid-connected point reference voltage to make the actual grid-connected point voltage of the inverter approach or be equal to the grid-connected point reference voltage.

[0056] It is understandable that when there is a short circuit fault in the power grid and the power grid voltage is abnormal due to high and low voltage penetration, the reactive power can be obtained as follows:

[0057]

[0058] Among them, V A is the terminal voltage of the virtual synchronous generator, V B is the remote voltage of the virtual synchronous generator (i.e., the grid voltage), Q A is the reactive power, δ is the power angle, R and X are the grid impedance and inductive reactance. It can be seen that when the grid voltage is abnormal, the reactive power will increase suddenly, causing the reactive current of the inverter to over-flow and the grid to become unstable.

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

[0060]

[0061] P A is the active power. It can be seen that when the grid voltage is abnormal, the same active power requires a larger power angle. At this time, if it is not restricted, it is easy to cause the power angle to become unstable, resulting in machine disconnection (that is, the grid-connected inverter is disconnected from the grid).

[0062] In the embodiment of the present application, the following steps 202 and 204 are performed to ensure the stability of the power grid when the power grid voltage is abnormal.

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

[0064] In the embodiment of the present application, the inverter is in a grid-connected state, and when an abnormal grid voltage is detected, the active power output of the inverter can be controlled to be 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; when the grid voltage is abnormal, the reactive power control process of the virtual synchronous generator can be stably crossed from the reactive loop to the voltage abnormality control loop, so that the virtual synchronous generator has the ability to stably cross.

[0065] Specifically, Figure 3 As shown, the active power set value in the active loop of the virtual synchronous generator can be controlled to zero, and the difference between the phase angle output by the active loop 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 abnormality control loop.

[0067] In an embodiment of the present application, a voltage anomaly control loop is added to the structure of the virtual synchronous generator. The final outputs of the voltage anomaly control loop and the reactive 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 support for the power grid through the reactive current output by the virtual synchronous generator when the power grid voltage is abnormal.

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

[0069] 204. Based on the current reactive current output by the virtual synchronous generator and the limited maximum current of the virtual synchronous generator, the excitation voltage of the virtual synchronous generator is gradually increased with the current grid voltage as a starting value.

[0070] In the voltage anomaly control loop, the current grid voltage, the current reactive current output by the virtual synchronous generator and the limited maximum current of the virtual synchronous generator can be input. Based on the current reactive current output by the virtual synchronous generator and the limited maximum current of the virtual synchronous generator, the excitation voltage of the virtual synchronous generator is gradually increased with the current grid voltage as the starting value, that is, the excitation voltage of the virtual synchronous generator output by the voltage anomaly control loop is gradually increased to increase the grid-connected point output voltage of the inverter, thereby increasing the reactive current output by the inverter, so that the inverter can output the required reactive current without exceeding the limited maximum current to achieve reactive support for the grid.

[0071] Specifically, the current difference can be obtained by subtracting the current reactive current of the virtual synchronous generator from the limited maximum current of the virtual synchronous generator; taking the amplitude of the current grid voltage as the starting value, the current difference is integrated and superimposed on the amplitude of the current grid voltage, and the execution is returned to: the step of subtracting the current reactive current of the virtual synchronous generator from the limited maximum current of the virtual synchronous generator to obtain the current difference, until the current reactive current is equal to the limited maximum current, or the amplitude of the superimposed current grid voltage is equal to the rated voltage of the virtual synchronous generator. That is, starting from the current grid voltage, the current difference of the limited maximum current minus the current reactive current is integrated and superimposed on the amplitude of the current grid voltage, until the current reactive current is equal to the limited maximum current, or the amplitude of the superimposed current grid voltage is equal to the rated voltage of the virtual synchronous generator. For various grid voltage anomalies such as short circuit faults and grid high and low penetration, the reactive current of the inverter can be quickly limited, and the current limiting response speed is fast, which effectively avoids the problem of the inverter being disconnected from the grid due to overcurrent of the reactive current output by the inverter.

[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 corresponding to the voltage abnormality control loop is:

[0074]

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

[0076] It can be seen that in the embodiment of the present application, 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, and for the reactive output part of the inverter, the reactive power control process of the virtual synchronous generator is switched from the reactive loop of the virtual synchronous generator to the voltage abnormality control loop; in the voltage abnormality control loop, based on the current reactive current output by the virtual synchronous generator and the limited maximum current of the virtual synchronous generator, the excitation voltage of the virtual synchronous generator is gradually increased with the current grid voltage as the starting value, and the excitation voltage is used to control the grid-connected point output voltage of the inverter, so that the grid-connected point output voltage amplitude of the inverter gradually increases and the difference between the grid-connected point output voltage amplitude and the grid voltage amplitude gradually increases, thereby increasing the reactive current output by the inverter, so that the inverter can output the required reactive current on the basis of not exceeding the limited maximum current to achieve reactive support for the grid, ensure the stability of the grid, and effectively avoid the problem of the inverter being disconnected from the grid due to overcurrent of the reactive current output by the inverter.

[0077] It can be understood that when the grid voltage is normal, the excitation voltage of the virtual synchronous generator can be directly output through the reactive loop of the virtual synchronous generator, which has no effect on the virtual synchronous generator and does not affect the overall control process of the virtual synchronous generator; the control idea is clear and the system resource occupation is small. During the voltage abnormality process, the grid-connected inverter corresponding to the virtual synchronous generator can still maintain the voltage source characteristics of the virtual synchronous generator, does not change the overall system control properties corresponding to the virtual synchronous generator, and can provide overload reactive support for the grid without changing the voltage source.

[0078] Further, in the embodiment of the present application, when the grid voltage is abnormal (i.e., the remote voltage of the virtual synchronous generator is abnormal), two situations may occur at this time: the reactive current of the virtual synchronous generator increases, and the machine-end voltage of the virtual synchronous generator is abnormal. In general, sampling can only collect the reactive current and machine-end voltage of the virtual synchronous generator; at this time, the reactive current of the virtual synchronous generator and / or the machine-end voltage of the virtual synchronous generator can be detected; based on the current change trend of the reactive current and / or, based on the machine-end voltage of the virtual synchronous generator, determine 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 the preset rise threshold, and / or the machine-end voltage is outside the grid crossing range, it is determined that the grid voltage is abnormal; wherein, the preset rise threshold can be an average current increment of 15A or 20A per second, which is not specifically limited here; the machine-end voltage is outside the grid crossing range, that is, the machine-end positive sequence voltage value is less than the grid low-through fault detection voltage threshold, or the machine-end positive sequence voltage value is greater than the grid high-through fault detection voltage threshold.

[0079] Specifically, the machine-end voltage of the virtual synchronous generator includes the machine-end positive-sequence voltage value of the virtual synchronous generator; based on the machine-end voltage of the virtual synchronous generator, determining whether the grid voltage is abnormal can be: if the machine-end positive-sequence voltage value of the virtual synchronous generator is less than the grid low-through fault detection voltage threshold, or the machine-end positive-sequence voltage value of the virtual synchronous generator is greater than the grid high-through fault detection voltage threshold, that is, the grid voltage is determined to be abnormal, then the reactive power control process of the virtual synchronous generator is switched from the reactive loop to the voltage abnormality control loop, so as to provide reactive support for the grid while crossing the grid voltage abnormality. If the machine-end positive-sequence voltage value of the virtual synchronous generator is greater than the grid low-through fault detection voltage threshold, and less than the grid high-through fault detection voltage threshold, that is, the grid voltage is determined to be normal, then the reactive power control process of the virtual synchronous generator is switched to the reactive loop.

[0080] The corresponding control equation is:

[0081]

[0082]

[0083] Among them, U d_pos is the positive sequence voltage value at the machine end; U LVRT is the voltage threshold for detecting low-voltage faults in the power grid; U HVRT It is the voltage threshold for detecting high-voltage faults in the power grid. When the power grid voltage is abnormal, the terminal voltage of the virtual synchronous generator (i.e. the corresponding grid-connected inverter port voltage) can be quickly adapted, and the overcurrent phenomenon under abnormal power grid voltage can be controlled through voltage adaptation, so as to achieve the purpose of supporting the power grid under abnormal power grid voltage.

[0084] Furthermore, the control process of the virtual synchronous generator mentioned in the embodiment of the present application can be simulated on a three-phase energy storage inverter, and the virtual synchronous generator can be operated at full load and connected to the grid; a remote voltage zero penetration test can be performed when the short-circuit capacity ratio is SCR2.0 and SCR10.0, respectively, and the zero penetration voltage fault lasts for three minutes to detect the control performance.

[0085] Among them, 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 terminal voltage of the virtual synchronous generator to the rated voltage of the virtual synchronous generator. At this time, after the grid voltage is abnormal, the virtual synchronous generator outputs reactive current according to the reactive demand, which can support the grid voltage to the rated value. The reactive current output by the virtual synchronous generator that is not greater than the maximum current can support the grid voltage, that is, the reactive current output by the inverter can support the grid voltage. Figure 4 As shown in the figure, line 1 represents the positive sequence voltage value at the machine end, line 2 is the reactive power, line 3 is the active power, and line 4 is the reactive current value.

[0086] Among them, when the terminal voltage of the virtual synchronous generator cannot be supported to the rated voltage of the virtual synchronous generator within the current capacity allowed by the virtual synchronous generator, and the grid voltage is abnormal at this time, the reactive current output by the virtual synchronous generator is the maximum current limit; when the reactive current output by the virtual synchronous generator is the maximum current limit, and the grid voltage has not returned to normal after the preset output time, the inverter is controlled to switch from the grid-connected state to the off-grid state (i.e., the inverter is shut down for protection); so as to realize the reactive current support capability corresponding to the preset output time of the grid-connected virtual synchronous generator (grid-building inverter) when the grid voltage is abnormal. The preset output time is preferably 10 seconds.

[0087] For example, when the short-circuit capacity ratio is SCR2.0, Figure 5 As shown in the figure, line 1 represents the positive sequence voltage value at the machine end, line 2 is reactive power, line 3 is active power, and line 4 is reactive current value. When the short-circuit capacity ratio is SCR2.0, the power grid is relatively strong. When the power grid voltage is abnormal, more reactive current is needed to support the power 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 power 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). After 10s of output, if the power grid voltage has not recovered, the inverter is controlled to disconnect from the grid, so as to realize the reactive current support capability of 10s when the grid-connected inverter is in the grid-connected state under the condition of abnormal power grid voltage. When the power grid voltage cannot be supported, the maximum power capacity output of the grid-connected inverter can be maintained to ensure the maximum power grid support capability that the grid-connected inverter can obtain.

[0088] The embodiment of the present 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, including:

[0089] The first control unit 601 is used to set the reactive power control process of the virtual synchronous generator to the reactive 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 loop of the virtual synchronous generator; the excitation voltage is used to control the grid-connected point output voltage of the inverter;

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

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

[0092] The embodiment of the present 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 the embodiment of the present application may include one or more central processing units (CPU) 701 and a memory 702 , in which one or more application programs or data are stored.

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

[0094] The inverter control device 700 may also include one or more power supplies 705, one or more wired or wireless network interfaces 704, one or more input and output interfaces 703, and / or one or more operating systems, such as Windows ServerTM, Mac OS XTM, UnixTM, LinuxTM, FreeBSDTM, etc.

[0095] The central processing unit 701 can execute the operations performed by any of the aforementioned specific method embodiments, and the details will not be repeated here.

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

[0097] An embodiment of the present application further provides a computer-readable storage medium, wherein the computer-readable storage medium includes instructions. When the instructions are executed on a computer, the computer executes the method described above.

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

[0099] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0100] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0101] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0102] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially 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, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, read-only memory), random access memory (RAM, random access memory), disk or optical disk and other media that can store program code.

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 loop of the virtual synchronous generator, and the excitation voltage of the virtual synchronous generator is output in the reactive loop of the virtual synchronous generator; the excitation voltage is used to control the grid-connected point output voltage of the inverter; When a grid voltage anomaly 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 anomaly control loop; In the voltage anomaly control loop, based on the current reactive current output by the virtual synchronous generator and the limited maximum current of the virtual synchronous generator, the excitation voltage of the virtual synchronous generator is gradually increased with the current grid voltage as the starting value.

2. The inverter control method according to claim 1, characterized in that: The controlling the active power in the active loop of the virtual synchronous generator to be zero comprises: The active power set value in the active 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 comprises: Detecting 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, it is determined 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 terminal positive sequence 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 machine end of the virtual synchronous generator is less than the grid low-through fault detection voltage threshold, or the positive sequence voltage value at the machine end of the virtual synchronous generator is greater than the grid high-through fault detection voltage threshold, it is determined that the grid voltage is abnormal; If the positive sequence voltage value at the machine end of the virtual synchronous generator is greater than the grid low-through fault detection voltage threshold and less than the grid high-through fault detection voltage threshold, it is determined that the grid voltage is normal.

5. The inverter control method according to claim 1, characterized in that: 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 limited maximum current of the virtual synchronous generator with the current grid voltage as the starting value comprises: Subtracting the current reactive current of the virtual synchronous generator from the limited maximum current of the virtual synchronous generator to obtain a current difference; Taking the amplitude of the current grid voltage as the starting value, integrating the current difference and superimposing it on the amplitude of the current grid voltage, and returning to execute: subtracting the current reactive current of the virtual synchronous generator from the limited maximum current of the virtual synchronous generator to obtain the current difference step, until the current reactive current is equal to the limited maximum current, 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.

6. The inverter control method according to claim 5, characterized in that: 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 equation corresponding to the voltage anomaly control loop: The excitation voltage E of the virtual synchronous generator is gradually increased, wherein: is the current grid voltage after superposition, where |U| is the amplitude of the current grid voltage, K is the adjustment coefficient, and I max is the maximum current limit of the virtual synchronous generator, I fdb is the current reactive current of the virtual synchronous generator, U rated is the rated voltage of the virtual synchronous generator, and min represents the minimum value.

7. The inverter control method according to claim 1, characterized in that: The method further comprises: When the reactive current output by the virtual synchronous generator is the limited maximum current and the grid voltage has not returned to normal after the preset output time, the inverter is controlled to switch from the grid-connected state to the grid-off state.

8. An inverter control device based on a virtual synchronous generator, wherein the inverter is in a grid-connected state, characterized in that: include: A first control unit is used to set the reactive power control process of the virtual synchronous generator to the reactive 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 loop of the virtual synchronous generator; the excitation voltage is used to control the grid-connected point output voltage of the inverter; A second control unit is used to control the active power output of the inverter to be zero and switch the reactive power control process of the virtual synchronous generator from the reactive loop of the virtual synchronous generator to the voltage abnormality control loop when an abnormal grid voltage is detected; The regulating unit is used to gradually increase the excitation voltage of the virtual synchronous generator in the voltage anomaly control loop based on the current reactive current output by the virtual synchronous generator and the limited maximum current of the virtual synchronous generator, taking the current grid voltage as the starting value.

9. An inverter control device based on a virtual synchronous generator, characterized in that: include: CPU, memory, input and output interface, wired or wireless network interface, power supply; The memory is a short-term storage memory or a persistent storage memory; The central processor is configured to communicate with the memory, and execute instruction operations in the memory on a control plane function entity to perform the method according to any one of claims 1 to 7.

10. A grid-connected inverter, characterized in that: When the grid-connected inverter is in a grid-connected state, the inverter control method based on a virtual synchronous generator according to any one of claims 1 to 7 is used to control the grid-connected inverter.

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