Inverter control method, control device and inverter

Abstract

The present application provides an inverter control method, a control device and an inverter, which relate to inverter technology; wherein the method comprises: during the startup process of the inverter, adjusting the output signal of the inverter by using a proportional feedforward control method; when the inverter startup is completed, switching the proportional feedforward control method to a high-pass filter feedforward control method, and adjusting the output signal by using a high-pass filter feedforward control method. The method of the present application can effectively improve the stability of the inverter during use.

Description

Technical Field

[0001] The present application relates to inverter technology, and in particular to an inverter control method, a control device and an inverter. Background Art

[0002] With the increase in the scale of new energy installations and the withdrawal of traditional thermal power, the short circuit ratio (SCR) of the power grid has decreased. Under low SCR conditions, the disturbance injected by the inverter is easily amplified, so it is particularly important to maintain the steady-state voltage operation of the inverter, achieve transient fault ride-through, and maintain power quality.

[0003] At present, when the inverter is connected to the power grid, in order to effectively ensure its dynamic performance, a feedforward control strategy is usually adopted. Among them, proportional feedforward control is widely used as a common method to adjust the output signal of the inverter. Proportional feedforward control can improve the response speed and anti-interference ability of the inverter to a certain extent by introducing a feedforward compensation link related to the input signal of the power grid.

[0004] However, in the above process, as the grid impedance increases, the phase margin will gradually decrease, which is not conducive to ensuring the stability of the inverter. Summary of the invention

[0005] The present application provides an inverter control method, a control device and an inverter, so as to improve the stability of the inverter when it is applied to a power grid.

[0006] In a first aspect, the present application provides an inverter control method, the method comprising:

[0007] During the startup process of the inverter, the output signal of the inverter is adjusted by using a proportional feedforward control method;

[0008] When the inverter is started up, the proportional feedforward control mode is switched to a high-pass filter feedforward control mode, and the output signal is adjusted using the high-pass filter feedforward control mode.

[0009] In another possible implementation, switching the proportional feedforward control mode to a high-pass filter feedforward control mode, and using the high-pass filter feedforward control mode to adjust the output signal includes:

[0010] Within a preset time after the inverter is powered on, the proportional feedforward control mode is switched to the high-pass filter feedforward control mode, and within the preset time, the proportional feedforward control mode and the high-pass filter feedforward control mode are simultaneously used to adjust the output signal;

[0011] After the preset time, the output signal is adjusted using the high-pass filter feedforward control method.

[0012] In another possible implementation, the simultaneously adopting the proportional feedforward control method and the high-pass filter feedforward control method to adjust the output signal includes:

[0013] The control ratio of the proportional feedforward control method is gradually reduced, and the control ratio of the high-pass filter feedforward control method is gradually increased.

[0014] In another possible implementation, the simultaneously adopting the proportional feedforward control method and the high-pass filter feedforward control method to adjust the output signal includes:

[0015] The control ratio of the proportional feedforward control method and the control ratio of the high-pass filter feedforward control method change at the same rate of change.

[0016] In another possible implementation, the simultaneously adopting the proportional feedforward control method and the high-pass filter feedforward control method to adjust the output signal includes:

[0017] The control ratio of the proportional feedforward control method is reduced from 1 to 0, and the control ratio of the high-pass filter feedforward control method is increased from 0 to 1, and the sum of the control ratio of the proportional feedforward control method and the control ratio of the high-pass filter feedforward control method is always 1.

[0018] In another possible implementation, the preset time is the duration that can achieve the highest stability of the inverter among the different durations corresponding to multiple groups of experiments; other experimental conditions of the multiple groups of experiments are consistent, and the other experimental conditions include the change rate of the proportional feedforward control method, the change rate of the high-pass filter feedforward control method, the control ratio of the proportional feedforward control method, and the control ratio of the high-pass filter feedforward control method.

[0019] In another possible implementation, the output signal is an output voltage, and the proportional feedforward control mode is a grid voltage proportional feedforward control mode; the method of adjusting the output signal of the inverter by using the proportional feedforward control mode includes:

[0020] Acquiring a current input voltage of a power grid to which the inverter is applied;

[0021] The grid voltage proportional feedforward control method is adopted to adjust the output voltage according to the current input voltage.

[0022] In another possible implementation, the output signal is an output voltage, and the high-pass filter feedforward control method is a high-pass filter voltage feedforward control method; the high-pass filter feedforward control method is used to adjust the output signal, including:

[0023] Acquiring a current input voltage of a power grid to which the inverter is applied;

[0024] The high-pass filter voltage feed-forward control method is adopted to adjust the output voltage according to the current input voltage.

[0025] In a second aspect, the present application provides an inverter control device, the device comprising:

[0026] A first control module, used for adjusting the output signal of the inverter by using a proportional feedforward control method during the startup process of the inverter;

[0027] The second control module is used to switch the proportional feedforward control mode to a high-pass filter feedforward control mode when the inverter is powered on, and use the high-pass filter feedforward control mode to adjust the output signal.

[0028] In a third aspect, the present application provides a control device, comprising: at least one processor and a memory;

[0029] The memory stores computer-executable instructions;

[0030] The at least one processor executes the computer-executable instructions stored in the memory, so that the at least one processor performs the method as described in any one of the first aspects above.

[0031] In a fourth aspect, the present application provides an inverter, wherein the inverter comprises the control device as described in the third aspect.

[0032] In a fifth aspect, the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a central processing unit, they are used to implement the method described in any one of the first aspects above.

[0033] In a sixth aspect, the present application provides a computer program product, including a computer program, which, when executed by a central processing unit, implements the method described in any one of the first aspects.

[0034] The present application provides an inverter control method, a control device and an inverter, wherein the method of the present application proposes to use a proportional feedforward control method to adjust the output signal of the inverter during the startup process of the inverter, and after the inverter is started, the proportional feedforward control method is switched to a high-pass filter feedforward control method, and the output signal is adjusted by the high-pass filter feedforward control method. Since the high-pass filter feedforward can greatly improve the phase of the output impedance in the low-frequency band, the low-frequency resonance is suppressed, and the stability of the inverter is improved. In addition, adjusting the output signal of the inverter in a proportional feedforward control method during the startup process of the inverter can effectively guarantee the response time, thereby effectively suppressing the error accumulation caused by the inability to respond to input changes in a timely manner, and thus it is also beneficial to maintain the accuracy and stability of the output signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0036] Figure 1A Schematic diagram 1 of an S-domain control block diagram of an inverter provided in an embodiment of the present application;

[0037] Figure 1B A schematic diagram of the effect of a proportional feedforward control provided in an embodiment of the present application;

[0038] Figure 1C A schematic diagram of the effect of a high-pass filter feedforward control provided in an embodiment of the present application;

[0039] Figure 2 A schematic diagram of an application scenario of an inverter control method provided in an embodiment of the present application;

[0040] Figure 3 A flowchart of an inverter control method provided in an embodiment of the present application is shown in FIG1 ;

[0041] Figure 4A A schematic diagram of a process of an inverter control method provided in an embodiment of the present application Figure 2 ;

[0042] Figure 4B A schematic diagram of an S-domain control block diagram of an inverter provided in an embodiment of the present application Figure 2 ;

[0043] Figure 5 An example diagram of a process of an inverter control method provided in an embodiment of the present application;

[0044] Figure 6 A comparison diagram of effects of different inverter control methods provided in an embodiment of the present application;

[0045] Figure 7 A schematic diagram of the structure of an inverter control device provided in an embodiment of the present application;

[0046] Figure 8 A schematic diagram of the structure of a control device provided in an embodiment of the present application.

[0047] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0048] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0049] The basic assumption of inverter power generation is that a stable power grid is required to provide a voltage reference for grid-connected power generation. As the installed capacity of new energy sources increases and old thermal power plants are gradually phased out, the short circuit ratio (SCR) will decrease. Under low SCR conditions, any disturbance injected by the inverter will be amplified by the weak power grid. Therefore, it is very important to maintain the voltage of the inverter in steady state operation, complete transient fault ride-through, and maintain power quality.

[0050] The traditional control strategy of the inverter draws on the active damping method of the LCL filter, introduces voltage or current feedback in the control, realizes active adjustment of the closed-loop output impedance, and thus improves the phase margin of the system and enhances the system stability and performance.

[0051] However, with the continuous improvement of the power system's requirements for inverter performance, it is difficult to meet the increasingly complex working conditions by relying solely on this traditional control method. For example, after using the traditional voltage or current feedback, the inverter control strategy has a small stability margin under the condition of a weak power grid, and is easily affected by external interference and disconnected from the grid. Or, the inverter is prone to oscillation when it is close to full load, resulting in the output power being out of control and disconnected from the grid. For some power stations in marginal areas, the SCR fluctuation is not only affected by the startup method of the synchronous generator, but also the SCR may suddenly halve after the grid disconnects the return line. Therefore, considering only one weak power grid condition is not enough to fully respond to risks, and the grid adaptability of the inverter must be guaranteed under strong and weak grids, no-load and full-load conditions.

[0052] It is understandable that when the inverter is connected to the grid, it usually cannot be connected to the grid at the location closest to the transformer, or the park where it is located needs to pass through multiple transformers when connected to the grid, resulting in a significant increase in the power system impedance of the inverter output connection point, making the grid fragile. In this case, the control loop of the inverter may become unstable due to the existence of grid impedance, and in severe cases, it may even cause the inverter to explode.

[0053] Therefore, it is proposed to use a feedforward control strategy to ensure the dynamic performance of the inverter when it is connected to the grid. Figure 1A Schematic diagram 1 of an S-domain control block diagram of an inverter provided in an embodiment of the present application, wherein i* 1 (s) is the current command received by the inverter, G i (s) is the current loop regulator, 1 / T s G is the sampling link. d (s) is the digital delay, G h (s) is the zero-order holder, K PWM is the inverter control gain, 1 / L 1 s is the LCL inverter inductor, 1 / Cs is the LCL capacitor, 1 / L 2 s is the grid-side inductance, K is the active damping coefficient of the capacitor current, Q(s) is the grid voltage feedforward, i 1 (s) is the output current of the inverter inductor, I c is the current of the filter capacitor, U c is the capacitor voltage of the filter capacitor, i 2 (s) is the grid current, e s (s) is the grid voltage, u L1 is the inductor current. In this control block diagram, when the current command (i* 1 (s)) is sampled and controlled by each link in the control block diagram, and finally a stable inverter inductor current (i 1 (s)).

[0054] It should be understood that, based on the above control block diagram, the impedance transfer function of the inverter is expressed as: In this function, Q(s) is used as the numerator. Changing Q(s) can change the inverter output impedance Z. o (s).

[0055] When proportional feedforward control is used to adjust the output signal of the inverter, Q(s) is specifically the transfer function of the proportional feedforward control. The proportional feedforward control can improve the response speed and anti-interference ability of the inverter to a certain extent by introducing a feedforward compensation link related to the input signal of the power grid.

[0056] However, Figure 1BA schematic diagram of the effect of a proportional feedforward control provided in an embodiment of the present application, wherein: Figure 1B In (1), the red curve is used to represent the inverter output impedance Z o The relationship between the amplitude and frequency, the blue curve is used to represent the grid impedance Z s The relationship curve between amplitude and frequency. Figure 1B The phase curve shown in (2) is used to represent Z o With Z s The amplitude of the intersection point corresponds to Z o The relationship between phase and frequency. Figure 1B As shown in the figure, when proportional feedforward control is adopted, as the grid impedance Z s The increase in phase margin (i.e., Z o With Z s The amplitude of the intersection point Z o The phase of the phase curve (the difference from -90° in the phase curve) will gradually decrease, and at the crossover frequency (that is, Z o With Z s The voltage resonance is easy to occur at the intersection of the amplitude of Z, which is not conducive to ensuring the stability of the inverter. s / Z o is the open loop transfer function.

[0057] Therefore, the present application provides an inverter control method, a control device and an inverter to solve the above problems. Specifically, the inverter control method of the present application proposes that after the inverter is powered on, the proportional feedforward control mode is switched to the high-pass filter feedforward control mode, and the output voltage of the inverter is adjusted by the high-pass filter feedforward control mode, so as to improve the phase of the output impedance in the low-frequency band, thereby suppressing the low-frequency resonance, effectively improving the defect of the proportional feedforward control mode that voltage resonance is prone to occur, and thus being conducive to effectively ensuring the stability of the inverter while ensuring the dynamic performance of the inverter.

[0058] Specifically, Figure 1C A schematic diagram of the effect of a high-pass filter feedforward control provided in an embodiment of the present application is shown in FIG. Figure 1C As shown in the figure, the high-pass filter voltage feedforward control method can greatly improve the phase of the output impedance in the low-frequency band, thereby suppressing the low-frequency resonance. Figure 1C In (1), the red curve is used to represent the inverter output impedance Z o The relationship between the amplitude and frequency, the blue curve is used to represent the grid impedance Z s The relationship curve between amplitude and frequency. Figure 1C The phase curve shown in (2) is used to represent Z o With Z s The amplitude of the intersection point corresponds to Z oThe relationship between phase and frequency. Figure 1C As shown, Z at the crossover frequency o The phase is 1.93°, and Figure 1B Z at mid-crossover frequency o The phase is -74.3°; obviously Figure 1C The phase margin (1.93°-(-90°)) is better than Figure 1B The mid-phase margin (-74.3° - (-90°)) is large, achieving suppression of low-frequency resonance.

[0059] As an example, Figure 2 A schematic diagram of an application scenario of an inverter control method provided in an embodiment of the present application, such as Figure 2 As shown, the inverter control method of the present application can be applied to any inverter used to supply power to a power grid. Figure 2 As shown, the output end of the inverter is connected to the power grid, and the input end is connected to the DC generator, which is used to convert the electric energy generated by the DC generator into AC electric energy and then transmit it to the power grid. Specifically, the inverter includes a control device, which is used to adjust the output signal of the inverter in a proportional feedforward control mode during the startup process, and after the startup is completed, the proportional feedforward control mode is switched to a high-pass filter feedforward control mode, and the output signal of the inverter is controlled in the high-pass filter feedforward control mode.

[0060] It is understandable that the control device of the inverter is also used to collect the input signal of the inverter input power grid, and adjust the output signal of the inverter in combination with the input signal and the corresponding feedforward control method.

[0061] In the above settings, the proportional feedforward control method is used during the startup process, which can quickly establish the output signal, thereby effectively ensuring the response time of the inverter. The high-pass filter feedforward control method is used after the startup is completed, which can improve the phase margin, thereby effectively ensuring the stability of the inverter during and after the startup process.

[0062] It can be understood that the method of the present application can also be executed by any other electronic device, as long as the electronic device can collect the signal of the inverter input to the power grid and control the output signal of the inverter, etc. For example, it can interact with the control device of the inverter to obtain the signal of the inverter input to the power grid and control the output signal of the inverter. This is not limited in this embodiment.

[0063] In the following, some embodiments of the present application are described in detail in conjunction with the accompanying drawings. In the case where the embodiments do not conflict with each other, the following embodiments and features in the embodiments can be combined with each other.

[0064] The present application provides an inverter control method, which is specifically executed by a control device of the inverter. Figure 3A flowchart of an inverter control method provided in an embodiment of the present application is shown in FIG. Figure 3 As shown, the method provided in this embodiment includes:

[0065] S301, during the startup process of the inverter, the output signal of the inverter is adjusted by using a proportional feedforward control method.

[0066] It can be understood that the core of the proportional feedforward control method is to obtain a control signal for adjusting the output signal of the inverter by multiplying the grid signal input to the grid by the proportional gain.

[0067] On this basis, in this embodiment, the control device first initializes and loads necessary parameters during the startup process of the inverter to determine the proportional gain of the proportional feedforward control method, which is configured in advance by the user in a designated storage location of the inverter. Then the control device collects the grid signal input from the inverter to the grid, and uses the grid signal and the proportional feedforward control method to adjust the output signal of the inverter to achieve the target output. Among them, the control device can control the amplitude and frequency of the output signal by adjusting the on and off time of the switching element of the inverter.

[0068] It is understandable that during the startup process of the inverter, the control device continuously monitors the grid signal and compares it with the target output. If there is a deviation, the control device can compensate by adjusting the proportional gain or other parameters to ensure the stability and accuracy of the output signal.

[0069] In this embodiment, the output signal is specifically an output voltage, and accordingly, the proportional feedforward control method is specifically a grid voltage proportional feedforward control method. On this basis, the specific process of the control device using the proportional feedforward control method to adjust the output signal of the inverter is: obtaining the current input voltage of the grid to which the inverter is applied; and using the voltage proportional feedforward control method to adjust the output voltage according to the current input voltage.

[0070] More specifically, the current input voltage of the power grid may be obtained through current sampling or power sampling, which is not limited in this embodiment.

[0071] S302, when the inverter is started up, the proportional feedforward control mode is switched to the high-pass filter feedforward control mode, and the output signal is adjusted by the high-pass filter feedforward control mode.

[0072] In this embodiment, the control device determines that the inverter startup is completed after receiving the preset time of the startup instruction. The preset time is specifically determined based on the historical startup time of the inverter. In practical applications, the control device can indicate the completion of the startup process by setting a flag bit or a status signal, for example, through the internal logic of the control device, when a specific condition is met, the status signal or flag bit is set to "startup completed", and the control device determines whether the inverter startup is completed by reading the status signal or flag bit.

[0073] In this embodiment, when the control device switches to the high-pass filter feedforward control mode, the control device loads the corresponding filter parameters and gain settings. Similarly, these parameters and settings are stored in a designated location of the inverter, and the control device obtains these parameters and settings by accessing the designated location.

[0074] In this embodiment, when the control device adjusts the output signal in a high-pass filter feedforward control mode, the grid signal of the inverter input to the grid is first processed by a high-pass filter to obtain a filtered signal, and then the filtered signal is multiplied by the control gain of the high-pass filter feedforward control mode to obtain an adjusted control signal, and finally the output signal of the inverter is adjusted by the control signal. Similarly, the control device achieves the adjustment by adjusting the on and off time of the inverter switch element.

[0075] It is understandable that when the control device adjusts the output signal through the high-pass filter feedforward control method, it continuously monitors the output signal and compares it with the target output. If there is a deviation, it is compensated by adjusting the high-pass filter parameters or the feedforward gain.

[0076] As a specific implementation method, the output signal can be the output voltage of the power grid, that is, the input voltage of the power grid of the inverter. Correspondingly, the high-pass filter feedforward control method is a high-pass filter voltage feedforward control method. On this basis, the specific process of the control device using the high-pass filter feedforward control method to adjust the output signal is: obtaining the current input voltage of the power grid to which the inverter is applied; using the high-pass filter voltage feedforward control method to adjust the output voltage according to the current input voltage. In another embodiment, the LCL filter capacitor voltage can be obtained and feedforward control can be performed after high-pass filtering.

[0077] In actual application, the output signal may also be an output current, and accordingly, the high-pass filter feedforward control method is specifically a high-pass filter current feedforward control method. The output signal may also be an electrical parameter such as output power, as long as the target output and the high-pass filter feedforward control method are adaptively adjusted, which is not limited in this embodiment.

[0078] In the method provided in this embodiment, during the startup process of the inverter, the output signal of the inverter is adjusted by a proportional feedforward control method, and the grid signal of the inverter input to the grid is directly multiplied by the proportional gain to generate a control signal for adjusting the output signal, which can quickly adjust the output signal of the inverter, so that the inverter can quickly enter a stable state. After the inverter is started, the proportional feedforward control method is switched to a high-pass filter feedforward control method, and the output signal of the inverter is adjusted by the high-pass filter feedforward control method, which can effectively filter out low-frequency interference in the grid signal of the inverter input to the grid, especially low-frequency harmonics that may exist in the grid, thereby helping to improve the quality of the inverter output and effectively ensure the stability of the inverter.

[0079] In one possible design, Figure 4A A schematic diagram of a process of an inverter control method provided in an embodiment of the present application Figure 2 Based on the above embodiment, this embodiment describes in detail the process of switching the proportional feedforward control mode to the high-pass filter feedforward control mode in the above embodiment. Figure 4A As shown, the method of this embodiment includes:

[0080] S401, during the startup process of the inverter, the output signal of the inverter is adjusted by using a proportional feedforward control method.

[0081] In this embodiment, the output signal specifically refers to the output voltage of the inverter, and the proportional feedforward control method is specifically a voltage proportional feedforward control method. The control device generates a control signal according to the voltage proportional feedforward control method, combining the grid signal of the inverter input grid and the target output voltage, and adjusts the output signal of the inverter through the control signal.

[0082] S402, within a preset time after the inverter is started up, the proportional feedforward control mode is switched to the high-pass filter feedforward control mode, and the proportional feedforward control mode and the high-pass filter feedforward control mode are simultaneously used to adjust the output signal.

[0083] In this embodiment, the control device completes the switching between the proportional feedforward control mode and the high-pass filter feedforward control mode within a preset time after the inverter is turned on. Specifically, within the preset time, the control device simultaneously uses the two modes to adjust the output signal. It can be understood that Figure 4B A schematic diagram of an S-domain control block diagram of an inverter provided in an embodiment of the present application Figure 2 ,like Figure 4B As shown, the transfer function of the feedforward control includes Q 1 (s) and Q 2 (s), are used to represent the proportional feedforward control mode and the high-pass filter feedforward control mode respectively.

[0084] As a preferred example, within a preset time, the control ratio of the proportional feedforward control method is gradually reduced, and the control ratio of the high-pass filter feedforward control method is gradually increased.

[0085] Specifically, the control ratio of the proportional feedforward control mode is reduced from 1 to 0, and the control ratio of the high-pass filter feedforward control mode is increased from 0 to 1, and the sum of the control ratios of the proportional feedforward control mode and the high-pass filter feedforward control mode is always 1. More specifically, if Figure 4B As shown, when the control ratio of the proportional feedforward control method is represented by k, the control ratio of the high-pass filter feedforward control method is 1-k.

[0086] In this example, by gradually reducing the control ratio of the limited proportional feedforward control method and gradually increasing the control ratio of the high-pass filter feedforward control method, and keeping the total control strength constant, the sudden change of the output signal and the sudden change of the control strength can be effectively avoided, which is beneficial to ensuring the stability of the inverter.

[0087] As a further design, in this example, the control ratio of the proportional feedforward control mode and the control ratio of the high-pass filter feedforward control mode change at the same rate of change. It can be understood that the rate of change refers to the speed at which the control ratio changes over time.

[0088] By adjusting the control ratio of the two control modes at the same rate of change, the system can achieve a smooth transition between the two control modes. This smooth transition helps to avoid sudden changes or instability in the output signal.

[0089] In addition, through the setting of this example, on the one hand, the control device can realize flexible conversion or adjustment of the two control strategies through the value of the control ratio of one of the control strategies. For example, within the preset time after the inverter is started up, the control ratio of the proportional feedforward control mode only needs to be set to 0.4, and the control ratio of the high-pass filter feedforward control mode can be automatically adjusted to 0.6. On the other hand, during the startup process of the inverter, the control device realizes that the control ratio of the high-pass filter feedforward control mode is 0 by setting the control ratio of the feedforward control mode to 1, that is, there is no need to use the high-pass filter feedforward control mode at this time, but the control device has sufficient time to load the parameters and settings required for the high-pass filter feedforward control mode before the high-pass filter feedforward control mode is needed, so that when the high-pass filter feedforward control mode is needed to adjust the output signal of the inverter, it can respond in time.

[0090] In this embodiment, the preset time is the time length that can make the applied inverter most stable among the different time lengths corresponding to multiple groups of experiments; other experimental conditions of the multiple groups of experiments are consistent, and the other experimental conditions include the change rate of the proportional feedforward control method, the change rate of the high-pass filter feedforward control method, the control ratio of the proportional feedforward control method, and the control ratio of the high-pass filter feedforward control method.

[0091] Specifically, the preset time in this embodiment is obtained through multiple groups of experiments. Specifically, in each group of experiments, other experimental conditions except the duration are consistent, such as the change rate of the proportional feedforward control mode and the high-pass filter feedforward control mode, and the control ratio of the proportional feedforward control mode and the high-pass filter feedforward control mode. On this basis, multiple groups of experiments are carried out, and each group of experiments uses a different duration. Specifically, the duration can range from a few milliseconds to a few seconds. In each group of experiments, the output signal of the inverter is recorded, and special attention is paid to the response and stability of the system before and after the switching point.

[0092] Furthermore, the stability indicators of each group of experiments, such as the standard deviation of the output signal, the maximum deviation, the harmonic distortion rate, etc., are calculated, and then the stability indicators under different time lengths are compared, and the time length that can make the inverter most stable is selected as the preset time.

[0093] In this embodiment, multiple repeated experiments are further performed on the selected preset time to verify its stability and consistency.

[0094] S403, after a preset time, the output signal is adjusted by a high-pass filter feedforward control method.

[0095] Specifically, in this embodiment, after a preset time, the control device uses a high-pass filter voltage feedforward control method to adjust the output voltage of the inverter in combination with the grid voltage of the inverter input grid and the target output voltage.

[0096] In the method provided in this embodiment, the preset time and the switching process of the two control strategies within the preset time are specifically defined, so that a smooth transition can be achieved within the preset time, so that the system can effectively avoid sudden changes in the output signal and improve the stability of the system.

[0097] In addition, in the method provided in this embodiment, the control device can flexibly adjust the control ratio of the two control strategies to adapt to different operating conditions, and quickly switch to the high-pass filter feedforward control mode when necessary.

[0098] From the above content, it can be seen that when the grid voltage proportional feedforward control method is adopted, as the grid impedance increases, the phase margin gradually decreases, and voltage resonance is likely to occur at the crossover frequency. Removing the grid voltage proportional feedforward control method can improve the stability of the weak grid. When the grid voltage high-pass filter feedforward control method is adopted, the phase of the output impedance in the low-frequency band can be greatly improved, thereby suppressing low-frequency resonance.

[0099] However, since the high-pass filter feedforward control mode responds slowly and cannot adjust the output signal of the inverter in time, the inverter control method of the present application proposes to use a soft start strategy when starting up. That is, the grid voltage proportional feedforward control mode is adopted when starting up, and the grid voltage proportional feedforward control mode is gradually exited within a preset time after the successful startup, and the grid voltage high-pass filter feedforward control mode is gradually put into operation simultaneously. Specifically, within a preset time after the successful startup, the control ratio of the grid voltage proportional feedforward control mode gradually decreases, and the control ratio of the grid voltage high-pass filter feedforward control mode gradually increases. Through this setting, on the one hand, the response time can be effectively guaranteed, and on the other hand, the stability of the inverter can be guaranteed.

[0100] As an example, Figure 5 This is a process example diagram of an inverter control method provided by an embodiment of the present application. Specifically, Figure 5 The horizontal axis represents time, and the vertical axis represents the control ratio. Figure 5 As shown, the preset time is specifically 1 second. The control device completes the switching between the proportional feedforward control mode and the high-pass filter feedforward control mode within 1 second, and within this 1 second, the change rates of the control proportions of the two control strategies are the same.

[0101] Through the above process, the control strategy is switched within 1 second at the same rate of change, and the system can achieve smooth transition, maintain stability, improve robustness, and demonstrate good dynamic adjustment capabilities. This design not only improves the performance of the system, but also enhances its adaptability and flexibility, making it suitable for use in a variety of application scenarios.

[0102] As an illustration, Figure 6 This is a comparison diagram of the effects of different inverter control methods provided in the embodiments of the present application. Specifically, Figure 6 The comparison diagram of the effects of proportional feedforward control, no feedforward control, and high-pass filter feedforward control is given in detail. Figure 6As shown, the phase margin of proportional feedforward gradually decreases with the increase of frequency, and the phase margin of high-pass filter feedforward control mode gradually increases before the cut-off frequency. As the cut-off frequency of the high-pass filter increases, in the low phase margin region, the phase angle of the output impedance gradually decreases, gradually approaching the phase characteristics of the no feedforward control mode. Therefore, the present application proposes that after the inverter is started up, the proportional feedforward control mode is switched to the high-pass filter feedforward control mode, which can effectively improve the stability of the inverter.

[0103] It is understandable that in the control design of the grid-connected inverter, the cutoff frequency of the high-pass filter can be selected according to specific system parameters and phase margin, so that the system can obtain a higher phase angle in a wide frequency range as much as possible.

[0104] The above-mentioned embodiment introduces an inverter control method from the perspective of method flow, and the following embodiment introduces an inverter control device from the perspective of a virtual module or a virtual unit. Please refer to the following embodiment for details.

[0105] The embodiment of the present application provides an inverter control device, Figure 7 A schematic diagram of the structure of an inverter control device provided in an embodiment of the present application is shown in FIG. Figure 7 As shown, the device comprises:

[0106] The first control module 71 is used to adjust the output signal of the inverter by using a proportional feedforward control method during the startup process of the inverter;

[0107] The second control module 72 is used to switch the proportional feedforward control mode to the high-pass filter feedforward control mode when the inverter is started up, and use the high-pass filter feedforward control mode to adjust the output signal.

[0108] In another possible implementation of the embodiment of the present application, the second control module 72 is specifically configured to:

[0109] Within a preset time after the inverter is started up, the proportional feedforward control mode is switched to the high-pass filter feedforward control mode, and within the preset time, the proportional feedforward control mode and the high-pass filter feedforward control mode are simultaneously used to adjust the output signal;

[0110] After a preset time, the output signal is adjusted using a high-pass filter feed-forward control method.

[0111] In another possible implementation of the embodiment of the present application, the second control module 72 is specifically configured to:

[0112] The control ratio of the proportional feedforward control method is gradually reduced, and the control ratio of the high-pass filter feedforward control method is gradually increased.

[0113] In another possible implementation of the embodiment of the present application, the second control module 72 is specifically configured to:

[0114] The control ratio of the proportional feedforward control method changes at the same rate as the control ratio of the high-pass filter feedforward control method.

[0115] In another possible implementation of the embodiment of the present application, the second control module 72 is specifically configured to:

[0116] The control ratio of the proportional feedforward control method decreases from 1 to 0, and the control ratio of the high-pass filter feedforward control method increases from 0 to 1, and the sum of the control ratios of the proportional feedforward control method and the high-pass filter feedforward control method is always 1.

[0117] Another possible implementation method of the embodiment of the present application is that the preset time is the duration that can make the applied inverter most stable among the different durations corresponding to multiple groups of experiments; other experimental conditions of the multiple groups of experiments are consistent, and the other experimental conditions include the change rate of the proportional feedforward control method, the change rate of the high-pass filter feedforward control method, the control ratio of the proportional feedforward control method, and the control ratio of the high-pass filter feedforward control method.

[0118] In another possible implementation of the embodiment of the present application, the output signal is an output voltage, and the proportional feedforward control mode is a grid voltage proportional feedforward control mode; the first control module 71 is specifically used for:

[0119] Obtain the current input voltage of the power grid to which the inverter is applied;

[0120] The grid voltage proportional feed-forward control method is adopted to adjust the output voltage according to the current input voltage.

[0121] In another possible implementation of the embodiment of the present application, the output signal is an output voltage, and the high-pass filter feedforward control mode is a high-pass filter voltage feedforward control mode; the second control module 72 is specifically used for:

[0122] Obtain the current input voltage of the power grid to which the inverter is applied;

[0123] A high-pass filter voltage feed-forward control method is used to adjust the output voltage according to the current input voltage.

[0124] An inverter control device provided in an embodiment of the present application is applicable to the above-mentioned method embodiment and will not be described in detail here.

[0125] A control device is provided in an embodiment of the present application. Figure 8 A schematic diagram of the structure of a control device provided in an embodiment of the present application is shown in FIG. Figure 8 As shown, Figure 8The control device shown includes: a processor 81 and a memory 82. The processor 81 and the memory 82 are connected, such as through a bus 83. Optionally, the control device may also include a transceiver 84. It should be noted that in actual applications, the transceiver 84 is not limited to one, and the structure of the control device does not constitute a limitation on the embodiments of the present application.

[0126] The processor 81 may be a central processing unit (CPU), a general processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. It may implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. The processor 81 may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc.

[0127] The bus 83 may include a path to transmit information between the above components. The bus 83 may be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The bus 83 may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 8 Only one thick line is used in the figure, but it does not mean that there is only one bus 83 or only one type of bus 83.

[0128] The memory 82 can be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, a random access memory (RAM) or other types of dynamic storage devices that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital versatile discs, Blu-ray discs, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited to these.

[0129] The memory 82 is used to store the application code for executing the solution of the present application, and the execution is controlled by the processor 81. The processor 81 is used to execute the application code stored in the memory 82 to implement the contents shown in the above method embodiment.

[0130] The present application also provides an inverter, which includes the control device of the above embodiment. The specific structure can be referred to Figure 2 , I will not go into details here.

[0131] The present application also provides a computer-readable storage medium, which may include: a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, and other media that can store program codes. Specifically, the computer-readable storage medium stores program instructions, and the program instructions are used to implement the methods in the above-mentioned embodiments.

[0132] A computer program product is also provided in an embodiment of the present application, including a computer program. When the computer program is executed by a processor, the technical solution of the above-mentioned method embodiment is implemented. The implementation principle and technical effect are similar and will not be repeated here.

[0133] An off-grid system is also provided in an embodiment of the present application. The off-grid system includes a power generation component, an energy storage component, a load component, and the electronic device in the aforementioned embodiment.

[0134] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the claims.

[0135] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. An inverter control method, characterized in that: The method comprises: During the startup process of the inverter, the output signal of the inverter is adjusted by using a proportional feedforward control method; Within a preset time after the inverter is started up, the proportional feedforward control mode is switched to a high-pass filter feedforward control mode, and within the preset time, the control ratio of the proportional feedforward control mode is gradually reduced, and the control ratio of the high-pass filter feedforward control mode is gradually increased; After the preset time, the output signal is adjusted using the high-pass filter feedforward control method.

2. The method according to claim 1, characterized in that The control ratio of the proportional feedforward control method and the control ratio of the high-pass filter feedforward control method change at the same rate of change.

3. The method according to claim 1, characterized in that The control ratio of the proportional feedforward control method is reduced from 1 to 0, and the control ratio of the high-pass filter feedforward control method is increased from 0 to 1, and the sum of the control ratio of the proportional feedforward control method and the control ratio of the high-pass filter feedforward control method is always 1.

4. The method according to claim 1, characterized in that: The preset time is the duration that can achieve the highest stability when applying the inverter among the different durations corresponding to multiple groups of experiments; other experimental conditions of the multiple groups of experiments are consistent, and the other experimental conditions include the change rate of the proportional feedforward control method, the change rate of the high-pass filter feedforward control method, the control ratio of the proportional feedforward control method, and the control ratio of the high-pass filter feedforward control method.

5. The method according to claim 1, characterized in that The output signal is an output voltage, and the proportional feedforward control mode is a grid voltage proportional feedforward control mode; The adopting proportional feedforward control method to adjust the output signal of the inverter comprises: Acquiring a current input voltage of a power grid to which the inverter is applied; The grid voltage proportional feedforward control method is adopted to adjust the output voltage according to the current input voltage.

6. The method according to claim 1, characterized in that The output signal is an output voltage, and the high-pass filter feedforward control mode is a high-pass filter voltage feedforward control mode; and the high-pass filter feedforward control mode is used to adjust the output signal, including: Acquiring a current input voltage of a power grid to which the inverter is applied; The high-pass filter voltage feed-forward control method is adopted to adjust the output voltage according to the current input voltage.

7. A control device, characterized in that: include: at least one processor and memory; The memory stores computer-executable instructions; The at least one processor executes the computer-executable instructions stored in the memory, so that the at least one processor performs the method according to any one of claims 1 to 6.

8. An inverter, characterized in that: The inverter comprises the control device according to claim 7.

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