Oscillation suppression methods for grid-connected inverters, computer equipment, readable storage media, and software products

Abstract

This application relates to an oscillation suppression method, computer device, readable storage medium, and program product for a grid-type inverter. It is applied to a power synchronization control module in the control device of a grid-type inverter. The power synchronization control module is used to suppress subsynchronous oscillations of the grid-type inverter by adjusting the virtual inertia of the inverter through a time-varying virtual inertia function when triggered by external disturbances. 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 an attenuation coefficient. Furthermore, the initial value of the time-varying virtual inertia remains unchanged even when the time-varying coefficient or the attenuation coefficient changes. This method can suppress subsynchronous oscillations of the grid-type inverter while preserving its original frequency support capability and power-frequency droop characteristics.

Description

Technical Field

[0001] This 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 Technology

[0002] In recent years, distributed generation units have received increasing attention in order to address environmental problems and the energy crisis. As the interface between distributed generation units and the grid and loads, the inverter's control strategy is crucial for the safe, stable, and efficient operation of power systems and microgrids. Currently, an increasing number of low-inertia, weakly damped grid-connected inverters are being integrated into power systems, leading to serious frequency stability issues. Therefore, various grid-connected inverter control technologies have been proposed. Due to their ability to provide functions and external characteristics similar to synchronous generators, they have been extensively studied and are considered solutions with great application potential.

[0003] However, grid-connected inverters not only possess similar functions and external characteristics to synchronous machines, but also inherit the complex electromechanical characteristics of synchronous machines, leading to severe subsynchronous oscillations under external disturbances. Furthermore, grid-connected inverters lack the good transient overcurrent capability of synchronous machines, and their power switching devices can be damaged or fail under severe subsynchronous power frequency oscillations, thus limiting the application of grid-connected inverters. Summary of the Invention

[0004] Therefore, it is necessary to provide an oscillation suppression method, computer equipment, computer-readable storage medium, and computer program product for grid-type inverters to address the subsynchronous oscillation problem existing in the above-mentioned grid-type inverters.

[0005] In a first aspect, this application provides an oscillation suppression method for a grid-connected inverter. The system topology of the grid-connected inverter includes a constant voltage DC source, a three-phase inverter, a filter circuit, line impedance, and a power grid. The filter circuit includes an inverter-side filter inductor, a filter capacitor, and a grid-side filter inductor. The line impedance includes a line inductance and a line resistance. The control device of the grid-connected 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 based on 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 the inverter based on 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 the current control signal based on 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 the PWM control signal based on 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 based on the PWM control signal and apply it to the three-phase inverter to control the three-phase inverter to chop the DC voltage;

[0007] 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 triggered by external disturbances, so as to suppress the subsynchronous 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 the initial value of the time-varying virtual inertia remains unchanged when the time-varying coefficient or the attenuation coefficient changes.

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

[0009] ;

[0010] Where A is the time-varying coefficient, B is the decay coefficient, and J is the virtual inertia. This 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 while 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 embodiment, the time-varying virtual inertia function is further used to enable the grid-type inverter to first increase the time-varying virtual inertia under external disturbances to increase the frequency change rate; and before the frequency reaches the maximum frequency deviation, to exponentially reduce the time-varying virtual inertia to reduce the frequency change rate.

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

[0015] The method of adjusting the virtual inertia of the grid-type inverter through a time-varying virtual inertia function to suppress the subsynchronous oscillation of the grid-type inverter includes:

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

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

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

[0019] ;

[0020] in, ;

[0021] ;

[0022] ;

[0023] ;

[0024] ;

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

[0026] Secondly, this application also provides a computer device. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps described in the above method.

[0027] Thirdly, this application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, implements the steps described in the above method.

[0028] Fourthly, this application also provides a computer program product. The computer program product includes a computer program that, when executed by a processor, implements the steps described in the above method.

[0029] The aforementioned oscillation suppression method, computer equipment, storage medium, and computer program product for grid-connected inverters utilize time-varying coefficients and attenuation coefficients to construct a time-varying virtual inertia function. This introduces an exponentially decaying component into the existing power synchronization control loop architecture of the grid-connected inverter. Upon external disturbance triggering, the virtual inertia of the grid-connected inverter itself is dynamically adjusted via the time-varying virtual inertia function to regulate its output power and suppress subsynchronous oscillations. This approach preserves the original frequency support capability and power-frequency droop characteristics of the grid-connected inverter while suppressing subsynchronous oscillations, thereby promoting the widespread application of grid-connected inverters. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the system topology of a grid-type inverter in one embodiment;

[0031] Figure 2 This is a schematic diagram of the overall control architecture of a grid-type inverter in one embodiment;

[0032] Figure 3 This is a flowchart illustrating an oscillation suppression method for a grid-connected inverter in one embodiment;

[0033] Figure 4 This is a schematic diagram representing the time-varying virtual inertia strategy in the core power synchronization control loop of a grid-type inverter in one embodiment;

[0034] Figure 5 This is a flowchart illustrating the oscillation suppression method for a grid-connected inverter in another embodiment;

[0035] Figure 6 This is a schematic diagram showing the experimental results of a conventional grid-type inverter in one embodiment;

[0036] Figure 7 This is a schematic diagram of the experimental results of the subsynchronous oscillation suppression method for grid-type inverters based on time-varying virtual inertia proposed in this application in one embodiment;

[0037] Figure 8 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0039] In related technologies, solutions to the subsynchronous oscillation problem in grid-connected inverters mainly fall into two categories: First, improving the phase margin of the power control loop of the grid-connected inverter through frequency domain analysis; second, suppressing subsynchronous oscillations by dynamically adjusting parameters such as the virtual inertia of the grid-connected inverter. However, the second type of method alters the characteristics supported by the grid, thus limiting its effectiveness to the parameter tuning range.

[0040] To address the aforementioned issues, this application proposes a method for suppressing subsynchronous oscillations in grid-connected inverters based on exponential time-varying virtual inertia. This method significantly suppresses power-frequency subsynchronous oscillations in grid-connected inverters without altering their original grid characteristics.

[0041] To facilitate understanding of this application, the structure and principle of the grid-connected inverter will be explained below.

[0042] refer to Figure 1 This is a schematic diagram of the system topology of a grid-type inverter provided in one embodiment. Figure 1 As shown, the system includes: a constant voltage DC source (to provide a constant DC voltage), a three-phase inverter (to receive control signals and chop the DC voltage), a filter circuit, line impedance, and the power grid. The filter circuit mainly consists of a filter inductor on the inverter side. Filter capacitor C and grid-side filter inductor Composition; Line impedance is composed of line inductance and line resistance constitute.

[0043] refer to Figure 2This is a schematic diagram of the overall control architecture of a grid-connected inverter provided in one embodiment. The principle is as follows: The power calculation module calculates the output power of the grid-connected inverter based on the grid-side filter inductor current and filter capacitor voltage in the filter circuit, and outputs the calculation result to the power synchronization control module. The power synchronization control module controls the inverter based on 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 based on the voltage control signal and the filter capacitor voltage, and generates a current control signal for the current control module. The current control module calculates based on 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 based on the PWM control signal. Finally, the drive signal is applied to... Figure 1 The three-phase inverter in the system controls the three-phase inverter to chop the DC voltage.

[0044] In one embodiment, such as Figure 3 As shown, an oscillation suppression method for a grid-connected inverter is provided and applied to a power synchronization control module. In this embodiment, the method includes the following steps:

[0045] Step S310: Determine the time-varying coefficient and the attenuation coefficient;

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

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

[0048] In practical implementation, the time-varying coefficient and attenuation coefficient are used to adjust the virtual inertia of the grid-connected inverter. Considering that the core virtual inertia parameter of the grid-connected inverter is a constant limited by the maximum rate of frequency change, and that existing methods for suppressing subsynchronous oscillations by dynamically adjusting virtual inertia alter the characteristics of the rate of frequency change, this application proposes a method for suppressing subsynchronous oscillations in grid-connected inverters based on time-varying virtual inertia. This method aims to suppress subsynchronous oscillations in grid-connected inverters while preserving their original frequency support capability and power-frequency droop characteristics.

[0049] More specifically, in an exemplary embodiment, constructing a time-varying virtual inertia function based on time-varying coefficients and attenuation coefficients includes: constructing a time-varying virtual inertia function according to the condition that the time-varying coefficients are positively correlated with the adjustment results and the attenuation coefficients are negatively correlated with the adjustment results.

[0050] In constructing the 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 construct the time-varying virtual inertia function together with the time-varying coefficient, the attenuation coefficient and the rated angular frequency.

[0051] Let the time-varying coefficient be A, the attenuation coefficient be B, the virtual inertia be J, and the rated angular frequency be... Based on 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 constructed time-varying virtual inertia function can be expressed as:

[0052] (1)

[0053] in, It can be considered as a component based on exponential decay.

[0054] Meanwhile, regardless of how the time-varying coefficient A and the attenuation coefficient B change, the initial value of the time-varying virtual inertia remains unchanged at the instant of external disturbance. This means that the time-varying virtual inertia will not change the original maximum frequency change rate and inertial support characteristics.

[0055] In the aforementioned oscillation suppression method for grid-connected inverters, a time-varying virtual inertia function is constructed using time-varying coefficients and attenuation coefficients. This introduces an exponentially decaying component into the existing power synchronization control loop architecture of the grid-connected inverter. Upon external disturbance triggering, the virtual inertia of the grid-connected inverter itself is dynamically adjusted via the time-varying virtual inertia function to regulate its output power and suppress subsynchronous oscillations. This method preserves the original frequency support capability and power-frequency droop characteristics of the grid-connected inverter while suppressing subsynchronous oscillations, thereby promoting the widespread application of grid-connected inverters.

[0056] In one 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; furthermore, 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, while the minimum value remains unchanged; furthermore, 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 this 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] Increasing the attenuation coefficient B in the time-varying virtual inertia function increases the attenuation rate of the time-varying virtual inertia, while the minimum value of the time-varying virtual inertia remains unchanged. Simultaneously, as the attenuation coefficient B increases, the power overshoot and maximum frequency offset in the subsynchronous oscillation of the grid-type inverter decrease. However, an excessively large B leads to an increased attenuation rate of the time-varying virtual inertia, resulting in a decreased rate of frequency change and a reduced active power response rate during transient responses.

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

[0060] In an exemplary embodiment, the aforementioned time-varying virtual inertia function is further used to enable the grid-type inverter to first increase the time-varying virtual inertia under external disturbances to increase the frequency change rate; and before the frequency reaches the maximum frequency deviation, to exponentially reduce the time-varying virtual inertia to reduce the frequency change rate.

[0061] In this embodiment, the time-varying virtual inertia enables the grid-connected inverter to initially employ a larger time-varying virtual inertia under external disturbances, thereby achieving a larger frequency change rate. This helps to adjust the power angle between the grid-connected inverter and the grid, accelerating active power and frequency response. Then, before the frequency reaches its maximum frequency deviation, the time-varying virtual inertia is exponentially reduced to decrease the frequency change rate, which helps suppress frequency oscillations. Finally, it decays to a set constant value, completing the entire disturbance process.

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

[0063] The above step S330 adjusts the virtual inertia of the grid-type inverter through a time-varying virtual inertia function to suppress the subsynchronous 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; and controlling the output power based on the active power control transfer function, the integral element and the power transmission model to suppress the subsynchronous oscillation of the grid-type inverter.

[0064] refer to Figure 4This is a schematic diagram illustrating the time-varying virtual inertia strategy in the core power synchronization control loop of a grid-connected inverter, as shown in one embodiment. In the diagram, Pset is the set output active power of the grid-connected inverter, D is the power allocation coefficient of the grid-connected inverter, 1 / s is the integral element inherent in the power synchronization control loop of the grid-connected inverter, and Pout is the output active power of the grid-connected inverter.

[0065] like Figure 4 As shown, the time-varying virtual inertia and power allocation coefficients form a loop. Therefore, they can be equivalently processed first. Based on the time-varying virtual inertia function and power allocation coefficients, the active power control transfer function is obtained. Further, based on the active power control transfer function, the integral element, and the power transfer model, the output power is controlled to suppress the subsynchronous oscillation of the grid-connected inverter. In other words, the core power synchronization control of the grid-connected inverter can be equivalent to a small-signal model to suppress the subsynchronous oscillation of the grid-connected inverter. This equivalent small-signal model can be expressed as:

[0066] (2)

[0067] in, (3)

[0068] in, This represents the open-loop transfer function of the equivalent small-signal model. Let represent the active power control transfer function composed of the time-varying virtual inertia function and the power distribution coefficient, where 1 / s represents the integral element and s characterizes the Laplace operator. This represents a power transfer model, where... Characterizes the reactive power control transfer function.

[0069] In this embodiment, an active power control transfer function is obtained based on a time-varying virtual inertia function and a power allocation coefficient. Furthermore, based on the active power control transfer function, an integral element, and a power transmission model, the output power is controlled, which can effectively reduce the amplitude of subsynchronous oscillations and suppress subsynchronous oscillations in grid-type inverters. In the active power control process, combined with an integral element, more precise adjustment of the system frequency can be achieved.

[0070] In an exemplary embodiment, it is set Characterized by the total equivalent line resistance, mainly composed of line resistance. And the parasitic resistance of the filter network; The total equivalent line inductance is mainly composed of grid-side filter inductance and line inductance. E represents the total equivalent line reactance, and E represents the output voltage amplitude of the grid-connected inverter. The voltage amplitude is represented by δ, and the phase difference between the output voltage of the grid-connected inverter and the grid voltage is represented by δ. This constitutes the power transfer model. , , , , They can be expressed by the following formulas respectively:

[0071] (4)

[0072] (5)

[0073] Where 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 transfer model is constructed using the equivalent line resistance, equivalent line inductance, equivalent line reactance, and output voltage amplitude of the grid inverter, as well as the grid voltage amplitude and the phase difference between the output voltage of the grid inverter and the grid voltage. This allows for accurate power control through the power transfer model, thereby improving the suppression effect on the subsynchronous oscillation of the grid inverter.

[0078] In one embodiment, such as Figure 5 The diagram shown is a flowchart illustrating an oscillation suppression method for a grid-connected inverter according to another embodiment. This embodiment includes the following steps:

[0079] Step S510: Determine the time-varying coefficient and the attenuation coefficient;

[0080] Step S520: Based on 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, a time-varying virtual inertia function is constructed; the time-varying virtual inertia function is a function of adjusting the virtual inertia of the grid-type inverter according to time; and, the initial value of the time-varying virtual inertia remains unchanged when the time-varying coefficient or the attenuation coefficient changes.

[0081] Step S530: Based on the time-varying virtual inertia function and power allocation coefficient, the active power control transfer function is obtained;

[0082] In step S540, under the triggering of external disturbance, the output power is controlled based on the active power control transfer function, integral element and power transmission model to suppress the subsynchronous oscillation of the grid-type inverter.

[0083] This method constructs a time-varying virtual inertia function using time-varying coefficients and attenuation coefficients. It introduces an exponentially decaying component into the existing power synchronization control loop architecture of the grid-type inverter. Upon external disturbance triggering, the virtual inertia of the grid-type inverter is dynamically adjusted through the time-varying virtual inertia function to regulate its output power and suppress subsynchronous oscillations. This method preserves the original frequency support capability and power-frequency droop characteristics of the grid-type inverter while suppressing subsynchronous oscillations, thereby promoting the widespread application of grid-type inverters.

[0084] refer to Figure 6 This is a schematic diagram showing the experimental results of a traditional grid-type inverter. Figure 6 It is evident that traditional grid-connected inverters exhibit severe subsynchronous resonance in both output current and output power under external command disturbances, with power and current overshoot reaching 70%. (Reference) Figure 7 The figure shows the experimental results of the subsynchronous oscillation suppression method for grid-type inverters based on time-varying virtual inertia proposed in this application. As can be seen from the figure, after adopting the method of this application, the subsynchronous oscillation of output power and output current is greatly suppressed, with an overshoot of only 15.6%. This shows that the application has a good suppression effect.

[0085] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0086] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 8As shown, the computer device includes a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When executed by the processor, the computer program implements an oscillation suppression method for a grid-type inverter. The display screen can be an LCD screen or an e-ink display screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

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

[0088] In one embodiment, a computer device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above method embodiments.

[0089] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon that, when executed by a processor, implements the steps in the above method embodiments.

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

[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, data stored, data displayed, 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 related data must comply with the relevant laws, regulations and standards of the relevant countries and regions.

[0092] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media 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), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0093] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for suppressing oscillations in 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, line impedance, and a power grid. The filter circuit includes an inverter-side filter inductor, a filter capacitor, and a grid-side filter inductor. The line impedance includes a line inductance and a line resistance. 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 based on 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 the inverter based on 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 the current control signal based on 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 the PWM control signal based on 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 based on the PWM control signal and apply it to the three-phase inverter to control the three-phase inverter to chop the DC voltage; The power synchronization control module is used to adjust the virtual inertia of the grid-type inverter through a time-varying virtual inertia function in the event of an external disturbance, thereby suppressing the subsynchronous 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 an attenuation coefficient. Furthermore, the initial value of the time-varying virtual inertia remains unchanged even when the time-varying coefficient or the attenuation coefficient changes. The relationship of the time-varying virtual inertia function is as follows: Where A is the time-varying coefficient, B is the attenuation coefficient, J is the virtual inertia, ω0 is the rated angular frequency, and t is time; 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 while 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.

2. The method according to claim 1, characterized in that, The time-varying virtual inertia function is also used to enable the grid-type inverter to first increase the time-varying virtual inertia under external disturbances to increase the frequency change rate; and before the frequency reaches the maximum frequency deviation, to exponentially reduce the time-varying virtual inertia to reduce the frequency change rate.

3. The method according to claim 1, characterized in that, The power synchronization control module also includes the power distribution coefficient, integral element, and power transmission model of the grid-type inverter.

4. The method according to claim 3, characterized in that, The method of adjusting the virtual inertia of the grid-type inverter through a time-varying virtual inertia function to suppress the subsynchronous oscillation of the grid-type inverter includes: Based on the time-varying virtual inertia function and the power allocation coefficient, the active power control transfer function is obtained; Based on the active power control transfer function, the integral element, and the power transmission model, the output power is controlled to suppress the subsynchronous oscillation of the grid-type inverter.

5. The method according to claim 4, characterized in that, The power transfer model is represented as follows: in, Among them, R g L represents the total equivalent line resistance. g X represents the total equivalent line inductance. g U represents the total equivalent line reactance, E represents the output voltage amplitude of the grid-connected inverter, and U represents the total equivalent line reactance. g δ represents the grid voltage amplitude, K represents the phase difference between the output voltage of the grid-connected inverter and the grid voltage, and D represents the reactive power control coefficient. q denoted by droop coefficient, and s denotes the Laplace operator.

6. The method according to claim 5, characterized in that, The method of controlling the output power based on the active power control transfer function, the integral element, and the power transfer model to suppress the subsynchronous oscillation of the grid-connected inverter includes: Based on the active power control transfer function, the integral element, and the power transmission model, a signal model is obtained; the signal model is an equivalent model for realizing the synchronous control of the core power of the grid-type inverter. The output power is controlled by the signal model to suppress the subsynchronous oscillation of the grid-type inverter.

7. The method according to claim 6, characterized in that, The signal model is represented as follows: in, G OP1 G represents the open-loop transfer function of the signal model. cp1 Let 1 / s represent the active power control transfer function, 1 / s represent the integral element, and s characterize the Laplace operator. The power transmission model is represented by J, where J is the virtual inertia, ω0 is the rated angular frequency, A is the time-varying coefficient, B is the attenuation coefficient, and D is the power distribution coefficient of the grid-type inverter.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the oscillation suppression method for the grid-type inverter as described in any one of claims 1 to 7.

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

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

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