Oscillation suppression method of network-forming inverter, computer equipment, readable storage medium and program product

Abstract

The invention relates to an oscillation suppression method of a network-building type inverter, computer equipment, a readable storage medium and a program product, and is applied to a power synchronization control module in a control device of the network-building type inverter, and the power synchronization control module is used for suppressing oscillation of the network-building type inverter under the condition of external disturbance triggering. Adjusting the virtual inertia of the network-building type inverter through a time-varying virtual inertia function so as to suppress the subsynchronous oscillation of the network-building type inverter; the time-varying virtual inertia function is a function for adjusting the virtual inertia of the network-forming inverter according to time and comprises a time-varying coefficient and the attenuation coefficient, and the initial value of the time-varying virtual inertia is kept unchanged under the condition that the time-varying coefficient or the attenuation coefficient changes. By adopting the method, the subsynchronous oscillation of the network-building type inverter can be suppressed while the original frequency supporting capability and the power-frequency droop characteristic of the network-building type inverter are kept.

Description

Technical Field

[0001] The present application relates to the field of inverter control technology, and in particular to an oscillation suppression method for a grid-type inverter, a computer device, a computer-readable storage medium, and a computer program product. Background Art

[0002] In recent years, in order to solve environmental problems and energy crises, distributed generators have attracted more and more attention. As the interactive interface between distributed generators and power grids and loads, the control strategy of the inverter is crucial for the safe, stable and efficient operation of power systems and microgrids. At present, more and more low-inertia, weakly damped grid-following inverters are connected to the power system, which brings serious frequency stability problems. For this reason, various grid-following inverter control technologies have been proposed one after another. Because they can provide functions and external characteristics similar to synchronous generators, they have been widely studied and are also considered to be solutions with great application prospects.

[0003] However, the grid-type inverter not only has similar functions and external characteristics as the synchronous machine, but also inherits the complex electromechanical characteristics of the synchronous machine. Under external disturbances, severe subsynchronous oscillations will occur. However, the grid-type inverter does not have the good transient overcurrent capability of the synchronous machine, and its power switching devices will be damaged or fail in severe subsynchronous power frequency oscillations, thus limiting the application of the grid-type inverter. Summary of the invention

[0004] Based on this, it is necessary to provide an oscillation suppression method for a grid-type inverter, a computer device, a computer-readable storage medium and a computer program product to address the subsynchronous oscillation technical problem existing in the above-mentioned grid-type inverter.

[0005] In the first aspect, the present application provides an oscillation suppression method for a grid-type inverter. The system topology of the grid-type inverter includes a constant voltage DC source, a three-phase inverter, a filter circuit, a line impedance and a grid, wherein the filter circuit includes an inverter-side filter inductor, a filter capacitor and a grid-side filter inductor, and the line impedance includes a line inductor and a line resistor; the control device of the grid-type inverter includes a power calculation module, a power synchronization control module, a voltage control module, a current control module and a PWM generation module;

[0006] The power calculation module is used to calculate the output power of the grid-type inverter according to the grid-side filter inductor current and filter capacitor voltage in the filter circuit, and output the calculation result to the power synchronization control module; the power synchronization control module is used to control according to the set output active power and the received output power, and output a voltage control signal to the voltage control module, the voltage control module is used to calculate according to the voltage control signal and the filter capacitor voltage, generate a current control signal and output it to the current control module; the current control module is used to calculate according to the current control signal and the inverter-side filter inductor current, generate a PWM control signal and output it to the PWM generation module; the PWM generation module is used to generate a drive signal according to the PWM control signal, and act on the three-phase inverter to control the three-phase inverter to chop the DC voltage;

[0007] Among them, the power synchronization control module is used to adjust the virtual inertia of the grid-type inverter through a time-varying virtual inertia function when an external disturbance is triggered, so as to suppress the sub-synchronous oscillation of the grid-type inverter; the time-varying virtual inertia function is a function that adjusts the virtual inertia of the grid-type inverter according to time, including a time-varying coefficient and the attenuation coefficient, and when the time-varying coefficient or the attenuation coefficient changes, the initial value of the time-varying virtual inertia remains unchanged.

[0008] In one embodiment, the relationship of the time-varying virtual inertia function is:

[0009] ;

[0010] Among them, A is the time-varying coefficient, B is the attenuation coefficient, J is the virtual inertia, is the rated angular frequency.

[0011] In one embodiment, when the time-varying coefficient is increased, the rate of change of the time-varying virtual inertia decreases and the minimum value increases; and as the time-varying coefficient increases, the power overshoot in the subsynchronous oscillation of the grid-type inverter increases and the maximum frequency offset increases;

[0012] When the attenuation coefficient is increased, the attenuation rate of the time-varying virtual inertia increases, and the minimum value remains unchanged; and as the attenuation coefficient increases, the power overshoot in the subsynchronous oscillation of the grid-type inverter decreases, and the maximum frequency offset decreases.

[0013] In one of the embodiments, the time-varying virtual inertia function is also used to enable the grid-type inverter to first increase the time-varying virtual inertia under the action of external disturbance to increase the frequency change rate; before the frequency reaches the maximum frequency deviation, the time-varying virtual inertia is reduced in an exponential form to reduce the frequency change rate.

[0014] In one embodiment, the power synchronization control module also includes the power allocation coefficient, the integral link and the power transmission model of the grid-type inverter;

[0015] The step of adjusting the virtual inertia of the grid-connected inverter by a time-varying virtual inertia function to suppress the subsynchronous oscillation of the grid-connected inverter comprises:

[0016] Based on the time-varying virtual inertia function and the power allocation coefficient, an active power control transfer function is obtained;

[0017] Based on the active power control transfer function, the integral link and the power transmission model, the output power is controlled to suppress the subsynchronous oscillation of the grid-connected inverter.

[0018] In one embodiment, the power transfer model is expressed as:

[0019] ;

[0020] in, ;

[0021] ;

[0022] ;

[0023] ;

[0024] ;

[0025] in, represents the total equivalent line resistance, represents the total equivalent line inductance, represents the total equivalent line inductance, E represents the output voltage amplitude of the grid-type inverter, represents the grid voltage amplitude, δ represents the phase difference between the output voltage of the grid-connected inverter and the grid voltage, K represents the reactive power control coefficient, Represents the reactive power droop coefficient.

[0026] In a second aspect, the present application further provides a computer device, wherein the computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the above method are implemented.

[0027] In a third aspect, the present application further provides a computer-readable storage medium, wherein a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps of the above method are implemented.

[0028] In a fourth aspect, the present application further provides a computer program product, wherein the computer program product comprises a computer program, and when the computer program is executed by a processor, the steps of the above method are implemented.

[0029] The oscillation suppression method, computer device, storage medium and computer program product of the above-mentioned grid-type inverter construct a time-varying virtual inertia function through time-varying coefficients and attenuation coefficients, and introduce a component based on exponential decay on the architecture of the original power synchronization control loop of the grid-type inverter. After the external disturbance is triggered, the virtual inertia of the grid-type inverter itself is dynamically adjusted through the time-varying virtual inertia function to adjust the output power of the grid-type inverter and suppress the sub-synchronous oscillation in the output power. It is possible to suppress the sub-synchronous oscillation of the grid-type inverter while retaining the original frequency support capability and power-frequency droop characteristics of the grid-type inverter, thereby improving the promotion and application of the grid-type inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a schematic diagram of a system topology of a grid-type inverter in one embodiment;

[0031] FIG2 is a schematic diagram of the overall control architecture of a grid-type inverter in one embodiment;

[0032] FIG3 is a schematic flow chart of an oscillation suppression method for a grid-type inverter according to an embodiment;

[0033] FIG4 is a schematic diagram of a time-varying virtual inertia strategy in a core power synchronization control loop of a grid-type inverter according to an embodiment;

[0034] FIG5 is a schematic flow chart of an oscillation suppression method for a grid-type inverter in another embodiment;

[0035] FIG6 is a schematic diagram of experimental results of a conventional grid-type inverter in one embodiment;

[0036] FIG7 is a schematic diagram of experimental results of a method for suppressing subsynchronous oscillation of a grid-type inverter based on time-varying virtual inertia proposed in the present application in one embodiment;

[0037] FIG. 8 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0039] In the related art, the solutions to the subsynchronous oscillation problem of grid-type inverters are mainly divided into two types: first, improving the phase margin of the power control loop of the grid-type inverter through frequency domain analysis; second, dynamically adjusting parameters such as the virtual inertia of the grid-type inverter to achieve the purpose of suppressing subsynchronous oscillation. However, the second type of method will change the characteristics of the grid support, thus being limited by the parameter setting range.

[0040] In response to the above problems, the present application proposes a method for suppressing sub-synchronous oscillations of a grid-type inverter based on exponential time-varying virtual inertia. This method greatly suppresses the power-frequency sub-synchronous oscillations of the grid-type inverter without changing the original grid-type characteristics.

[0041] To facilitate understanding of the present application, the structure and principle of the grid-connected inverter are first described below.

[0042] Refer to Figure 1, which is a schematic diagram of the system topology of a grid-type inverter provided in an embodiment. As shown in Figure 1, the system includes: a constant voltage DC source (used to provide a constant DC voltage), a three-phase inverter (used to receive a control signal to chop the DC voltage), a filter circuit, a line impedance, and a power grid. Among them, the filter circuit is mainly composed of an inverter side filter inductor. , filter capacitor C and grid-side filter inductor The line impedance is composed of the line inductance and line resistance constitute.

[0043] Referring to FIG2, a schematic diagram of the overall control architecture of a grid-type inverter provided in an embodiment is provided, and its principle is as follows: the power calculation module calculates the output power of the grid-type inverter according to the grid-side filter inductor current and the filter capacitor voltage in the filter circuit, and outputs the calculation result to the power synchronization control module. The power synchronization control module controls according to the set output active power and the calculated output power, and outputs a voltage control signal to the voltage control module. The voltage control module calculates according to the voltage control signal and the filter capacitor voltage, and generates a current control signal to the current control module. The current control module calculates according to the current control signal and the inverter-side filter inductor current, generates a PWM (Pulse Width Modulation) control signal, and outputs it to the PWM generation module. The PWM generation module generates a drive signal according to the PWM control signal. Finally, the drive signal acts on the three-phase inverter in FIG1 to control the three-phase inverter to chop the DC voltage.

[0044] In one embodiment, as shown in FIG3 , a method for suppressing oscillation of a grid-type inverter is provided and applied to a power synchronization control module. In this embodiment, the method includes the following steps:

[0045] Step S310, determining a time-varying coefficient and an attenuation coefficient;

[0046] Step S320, constructing a time-varying virtual inertia function based on the time-varying coefficient and the attenuation coefficient; the time-varying virtual inertia function is a function that adjusts the virtual inertia of the grid-connected inverter according to time; and when the time-varying coefficient or the attenuation coefficient changes, the initial value of the time-varying virtual inertia remains unchanged;

[0047] Step S330: When an external disturbance is triggered, the virtual inertia of the grid-connected inverter is adjusted by a time-varying virtual inertia function to suppress the subsynchronous oscillation of the grid-connected inverter.

[0048] In the specific implementation, the time-varying coefficient and the attenuation coefficient are the coefficients for adjusting the virtual inertia of the grid-type inverter. Considering that the core virtual inertia parameter of the grid-type inverter is a constant limited by the maximum frequency change rate, the existing subsynchronous oscillation suppression method of dynamically adjusting the virtual inertia will change the characteristics of the frequency change rate. In this regard, the present application proposes a method for suppressing the subsynchronous oscillation of the grid-type inverter based on time-varying virtual inertia, so as to achieve the purpose of suppressing the subsynchronous oscillation of the grid-type inverter while retaining the original frequency support capability and power-frequency droop characteristics of the grid-type inverter.

[0049] More specifically, in an exemplary embodiment, a time-varying virtual inertia function is constructed based on the time-varying coefficient and the attenuation coefficient, including: constructing the time-varying virtual inertia function under the condition that the time-varying coefficient is positively correlated with the adjustment result and the attenuation coefficient is negatively correlated with the adjustment result.

[0050] Among them, when constructing a time-varying virtual inertia function based on the time-varying coefficient and the attenuation coefficient, it is also necessary to introduce the rated angular frequency of the rotor in the grid-type inverter, and jointly construct the time-varying virtual inertia function according to the time-varying coefficient, the attenuation coefficient and the rated angular frequency.

[0051] If the time-varying coefficient is A, the attenuation coefficient is B, the virtual inertia is J, and the rated angular frequency is , then according to the conditions that the time-varying coefficient is positively correlated with the adjustment result and the attenuation coefficient is negatively correlated with the adjustment result, the constructed time-varying virtual inertia function can be expressed as:

[0052] (1)

[0053] in, Can be viewed as an exponentially decaying component.

[0054] At the same time, no matter how the time-varying coefficient A and the attenuation coefficient B change, at the moment of external disturbance, the initial value of the time-varying virtual inertia remains unchanged, which means that the time-varying virtual inertia will not change the original maximum frequency change rate and inertial support characteristics.

[0055] In the oscillation suppression method of the above-mentioned grid-type inverter, a time-varying virtual inertia function is constructed by using a time-varying coefficient and an attenuation coefficient, and a component based on exponential decay is introduced into the architecture of the power synchronization control loop of the original grid-type inverter. Therefore, after the external disturbance is triggered, the virtual inertia of the grid-type inverter itself is dynamically adjusted by the time-varying virtual inertia function to adjust the output power of the grid-type inverter and suppress the subsynchronous oscillation in the output power. It is possible to suppress the subsynchronous oscillation of the grid-type inverter while retaining the original frequency support capability and power-frequency droop characteristics of the grid-type inverter, thereby improving the promotion and application of the grid-type inverter.

[0056] In an exemplary embodiment, when the time-varying coefficient is increased, the rate of change of the time-varying virtual inertia decreases and the minimum value increases; and as the time-varying coefficient increases, the power overshoot in the subsynchronous oscillation of the grid-type inverter increases and the maximum frequency offset increases. When the attenuation coefficient is increased, the attenuation rate of the time-varying virtual inertia increases and the minimum value remains unchanged; and as the attenuation coefficient increases, the power overshoot in the subsynchronous oscillation of the grid-type inverter decreases and the maximum frequency offset decreases.

[0057] Specifically, the time-varying virtual inertia strategy of the present application also has the following characteristics: when the time-varying coefficient A in the time-varying virtual inertia function is increased, the rate of change of the time-varying virtual inertia decreases, and the minimum value of the time-varying virtual inertia increases. At the same time, as the time-varying coefficient A increases, the power overshoot in the subsynchronous oscillation of the grid-type inverter increases, and the maximum frequency offset also increases.

[0058] When the attenuation coefficient B in the time-varying virtual inertia function is increased, the attenuation rate of the time-varying virtual inertia increases, and the minimum value of the time-varying virtual inertia remains unchanged. At the same time, as the attenuation coefficient B increases, the power overshoot in the subsynchronous oscillation of the grid-type inverter decreases, and the maximum frequency offset decreases. However, an excessively large B will increase the attenuation rate of the time-varying virtual inertia, resulting in a decrease in the frequency change rate during the transient response process and a decrease in the active power response rate.

[0059] In this embodiment, the appropriate time-varying coefficient A and attenuation coefficient B can be selected through the above-mentioned time-varying virtual inertia strategy to find the best balance between improving system stability, preventing overshoot and controlling frequency offset.

[0060] In an exemplary embodiment, the above-mentioned time-varying virtual inertia function is also used to enable the grid-type inverter to first increase the time-varying virtual inertia under the action of external disturbance to increase the frequency change rate; before the frequency reaches the maximum frequency deviation, the time-varying virtual inertia is reduced in an exponential form to reduce the frequency change rate.

[0061] In this embodiment, the time-varying virtual inertia enables the grid-type inverter to first use a larger time-varying virtual inertia under the action of external disturbance to obtain a larger frequency change rate, which helps the power angle between the grid-type inverter and the power grid to change and accelerate the active power and frequency response. Then, before the frequency reaches the maximum frequency deviation, the time-varying virtual inertia is reduced in an exponential form to reduce the frequency change rate, which is conducive to suppressing frequency oscillation. Finally, it decays to the set constant value to complete the entire disturbance process.

[0062] In an exemplary embodiment, the time-varying virtual inertia function is configured in a power synchronization control loop of a grid-type inverter, and the power synchronization control module also includes a power allocation coefficient, an integral link, and a power transmission model of the grid-type inverter;

[0063] The above step S330 adjusts the virtual inertia of the grid-type inverter through the time-varying virtual inertia function to suppress the sub-synchronous oscillation of the grid-type inverter, including: obtaining the active power control transfer function based on the time-varying virtual inertia function and the power distribution coefficient; based on the active power control transfer function, the integral link and the power transmission model, controlling the output power to suppress the sub-synchronous oscillation of the grid-type inverter.

[0064] Referring to Figure 4, a schematic diagram of a time-varying virtual inertia strategy in a core power synchronization control loop of a grid-type inverter is shown in an embodiment. In the figure, Pset is the set output active power of the grid-type inverter, D is the power allocation coefficient of the grid-type inverter, 1 / s is the integral link inherent in the power synchronization control loop of the grid-type inverter, and Pout is the output active power of the grid-type inverter.

[0065] As shown in Figure 4, the time-varying virtual inertia and the power allocation coefficient form a loop. Therefore, they can be treated equivalently first, and the active power control transfer function can be obtained based on the time-varying virtual inertia function and the power allocation coefficient. Further, based on the active power control transfer function, the integral link and the power transmission model, the output power is controlled to suppress the subsynchronous oscillation of the grid-forming inverter. In other words, the core power synchronous control of the grid-forming inverter can be equivalent to a small signal model to achieve the suppression of the subsynchronous oscillation of the grid-forming inverter. The equivalent small signal model can be expressed as:

[0066] (2)

[0067] in, (3)

[0068] in, represents the open-loop transfer function of the equivalent small-signal model, represents the active power control transfer function composed of the time-varying virtual inertia function and the power allocation coefficient, 1 / s represents the integral link, s represents the Laplace operator, represents the power transfer model, where Characterize the reactive power control transfer function.

[0069] In this embodiment, based on the time-varying virtual inertia function and the power distribution coefficient, the active power control transfer function is obtained, and the output power is further controlled based on the active power control transfer function, the integral link and the power transmission model, which can effectively reduce the amplitude of the subsynchronous oscillation to suppress the subsynchronous oscillation of the grid-connected inverter; in the active power control process, combined with the integral link, more precise adjustment of the system frequency can be achieved.

[0070] In an exemplary embodiment, Characterizes the total equivalent line resistance, mainly composed of line resistance And the parasitic resistance composition of the filter network; Characterizes the total equivalent line inductance, which is mainly composed of grid-side filter inductance and line inductance. represents the total equivalent line inductance, E represents the output voltage amplitude of the grid-type inverter, represents the grid voltage amplitude, and δ represents the phase difference between the output voltage of the grid-connected inverter and the grid voltage. , , , , They can be expressed by the following formulas:

[0071] (4)

[0072] (5)

[0073] Among them, K represents the reactive power control coefficient, Characterizes the reactive power droop coefficient.

[0074] (6)

[0075] (7)

[0076] (8)

[0077] In this embodiment, a power transmission model is constructed by using the equivalent line resistance, equivalent line inductance, equivalent line reactance, output voltage amplitude of the grid-type inverter, the grid voltage amplitude of the power grid, and the phase difference between the output voltage of the grid-type inverter and the grid voltage. Accurate power control can be performed through the power transmission model to improve the suppression effect of subsynchronous oscillation of the grid-type inverter.

[0078] In one embodiment, as shown in FIG5 , it is a flow chart of an oscillation suppression method of a grid-connected inverter provided in another embodiment. In this embodiment, the following steps are included:

[0079] Step S510, determining a time-varying coefficient and an attenuation coefficient;

[0080] Step S520, constructing a time-varying virtual inertia function according to the condition that the time-varying coefficient is positively correlated with the adjustment result and the attenuation coefficient is negatively correlated with the adjustment result; the time-varying virtual inertia function is a function that adjusts the virtual inertia of the grid-type inverter according to time; and when the time-varying coefficient or the attenuation coefficient changes, the initial value of the time-varying virtual inertia remains unchanged;

[0081] Step S530, obtaining an active power control transfer function based on the time-varying virtual inertia function and the power allocation coefficient;

[0082] Step S540, when an external disturbance is triggered, the output power is controlled based on the active power control transfer function, the integral link and the power transmission model to suppress the subsynchronous oscillation of the grid-connected inverter.

[0083] The method constructs a time-varying virtual inertia function through a time-varying coefficient and an attenuation coefficient, and introduces a component based on exponential decay on the architecture of the power synchronization control loop of the original grid-forming inverter. Therefore, after an external disturbance is triggered, the virtual inertia of the grid-forming inverter itself is dynamically adjusted through the time-varying virtual inertia function to adjust the output power of the grid-forming inverter and suppress subsynchronous oscillations in the output power. The method can suppress the subsynchronous oscillations of the grid-forming inverter while retaining the original frequency support capability and power-frequency droop characteristics of the grid-forming inverter, thereby improving the promotion and application of the grid-forming inverter.

[0084] Referring to FIG6 , which is a schematic diagram of the experimental results of a traditional grid-type inverter, it can be clearly observed from FIG6 that the output current and output power of the traditional grid-type inverter both exhibit severe subsynchronous resonance under the disturbance of external commands, and the power and current overshoots reach 70%. Referring to FIG7 , which is a schematic diagram of the experimental results of the subsynchronous oscillation suppression method of the grid-type inverter based on time-varying virtual inertia proposed in the present application, it can be seen from the figure that after adopting the method of the present application, the subsynchronous oscillation of the output power and output current is greatly suppressed, showing only 15.6% overshoot, which shows that the present application has a good suppression effect.

[0085] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0086] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be shown in FIG8. The computer device includes a processor, a memory, a communication interface, a display screen, and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be implemented through WIFI, a mobile cellular network, NFC (near field communication) or other technologies. When the computer program is executed by the processor, an oscillation suppression method for a meshed inverter is implemented. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covered on the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0087] Those skilled in the art will understand that the structure shown in FIG. 8 is merely a block diagram of a partial structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0088] In one embodiment, a computer device is further provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above method embodiments when executing the computer program.

[0089] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0090] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0091] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant laws, regulations and standards of relevant countries and regions.

[0092] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but are not limited to this.

[0093] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for suppressing oscillation of a grid-connected inverter, characterized in that: The system topology of the grid-type inverter includes a constant voltage DC source, a three-phase inverter, a filter circuit, a line impedance and a grid, wherein the filter circuit includes an inverter-side filter inductor, a filter capacitor and a grid-side filter inductor, and the line impedance includes a line inductor and a line resistor; the control device of the grid-type inverter includes a power calculation module, a power synchronization control module, a voltage control module, a current control module and a PWM generation module; The power calculation module is used to calculate the output power of the grid-type inverter according to the grid-side filter inductor current and filter capacitor voltage in the filter circuit, and output the calculation result to the power synchronization control module; the power synchronization control module is used to control according to the set output active power and the received output power, and output a voltage control signal to the voltage control module, the voltage control module is used to calculate according to the voltage control signal and the filter capacitor voltage, generate a current control signal and output it to the current control module; the current control module is used to calculate according to the current control signal and the inverter-side filter inductor current, generate a PWM control signal and output it to the PWM generation module; the PWM generation module is used to generate a drive signal according to the PWM control signal, and act on the three-phase inverter to control the three-phase inverter to chop the DC voltage; Among them, the power synchronization control module is used to adjust the virtual inertia of the grid-type inverter through a time-varying virtual inertia function when an external disturbance is triggered, so as to suppress the sub-synchronous oscillation of the grid-type inverter; the time-varying virtual inertia function is a function that adjusts the virtual inertia of the grid-type inverter according to time, including a time-varying coefficient and the attenuation coefficient, and when the time-varying coefficient or the attenuation coefficient changes, the initial value of the time-varying virtual inertia remains unchanged.

2. The method according to claim 1, characterized in that The relationship between the time-varying virtual inertia function is: ； Among them, A is the time-varying coefficient, B is the attenuation coefficient, J is the virtual inertia, is the rated angular frequency.

3. The method according to claim 2, characterized in that When the time-varying coefficient is increased, the rate of change of the time-varying virtual inertia decreases and the minimum value increases; and as the time-varying coefficient increases, the power overshoot in the subsynchronous oscillation of the grid-type inverter increases and the maximum frequency offset increases.

4. The method according to claim 2, characterized in that: When the attenuation coefficient is increased, the attenuation rate of the time-varying virtual inertia increases, and the minimum value remains unchanged; and as the attenuation coefficient increases, the power overshoot in the subsynchronous oscillation of the grid-type inverter decreases, and the maximum frequency offset decreases.

5. The method according to claim 2, characterized in that: The time-varying virtual inertia function is also used to increase the time-varying virtual inertia of the grid-type inverter under the action of external disturbance to increase the frequency change rate; and before the frequency reaches the maximum frequency deviation, reduce the time-varying virtual inertia in an exponential form to reduce the frequency change rate.

6. The method according to claim 1, characterized in that The power synchronization control module also includes the power allocation coefficient, integral link and power transmission model of the grid-type inverter; The step of adjusting the virtual inertia of the grid-connected inverter by a time-varying virtual inertia function to suppress the subsynchronous oscillation of the grid-connected inverter comprises: Based on the time-varying virtual inertia function and the power allocation coefficient, an active power control transfer function is obtained; Based on the active power control transfer function, the integral link and the power transmission model, the output power is controlled to suppress the subsynchronous oscillation of the grid-connected inverter.

7. The method according to claim 6, characterized in that The power transfer model is expressed as: ； in, ; ； ； ； ； in, represents the total equivalent line resistance, represents the total equivalent line inductance, represents the total equivalent line inductance, E represents the output voltage amplitude of the grid-type inverter, represents the grid voltage amplitude, δ represents the phase difference between the output voltage of the grid-connected inverter and the grid voltage, K represents the reactive power control coefficient, Represents the reactive power droop coefficient.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the oscillation suppression method of the grid-type inverter according to any one of claims 1 to 7 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the oscillation suppression method of a grid-type inverter according to any one of claims 1 to 7 are implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the oscillation suppression method of the grid-type inverter according to any one of claims 1 to 7 are implemented.

Images