Power supply system and control method thereof

Abstract

The invention provides a power supply system and a control method thereof, the power supply system comprises a control device and at least one power conversion device, the output end of the power conversion device and an alternating current power grid are connected to a grid-connected point, and the control device is connected with the power conversion device. And the control equipment controls disturbance signal injection of the power conversion equipment so as to trigger the power conversion equipment to output disturbance alternating current to the alternating current power grid. Under the condition that the disturbance signal is injected, the alternating current parameter at the grid-connected point is smaller than or equal to a first disturbance threshold value. After the disturbance signal of the power conversion equipment is controlled to be injected, the control equipment collects a first voltage signal and a first current signal at the grid-connected point, and controls the power conversion equipment to adjust the output alternating current based on the first voltage signal and the first current signal. According to the invention, adjustment can be carried out according to the control method of the power change equipment when the AC power grid is in different working conditions, so that stable operation of the AC power grid in different working conditions can be ensured.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and particularly to a power supply system and its control method. Background Art

[0002] With the continuous development of new energy technologies, DC power sources such as new energy devices and energy storage devices are widely connected to the power grid for use. The DC power source is connected to the power grid through a power conversion device, and the DC power is converted into AC power through the power conversion device to supply power to the power grid. However, since the output current of the power conversion device often has strong fluctuations and weak support for the grid voltage, the DC power source supplying power to the power grid through the power conversion device will reduce the stability of the power grid. Therefore, how to ensure the stability of the power grid under different operating conditions of the power conversion device when it is connected to the grid in the scenario of using the power conversion device to supply power to the power grid is one of the technical problems that those skilled in the art urgently need to solve.

[0003] The inventors of this application found in the process of research and practice that the existing technology is based on the scenario where a power conversion device is incorporated into a power grid composed of a fixed impedance and a voltage source with a fixed frequency and voltage, and designs, models, and analyzes the grid connection control strategy of the power conversion device. The fixed grid connection control strategy of the power conversion device ignores the actual situation that the grid parameters change continuously with the grid operating conditions, and cannot adapt to the complex and time-varying power grid to achieve the optimal control effect. Summary of the Invention

[0004] This application provides a power supply system and its control method. When the power supply system is incorporated into an AC power grid through a power conversion device, it can identify the grid parameters of the AC power grid and adjust the control strategy of the power conversion device, thereby ensuring the stable operation of the AC power grid under different operating conditions.

[0005] In a first aspect, the present application provides a power supply system. The power supply system includes a control device and at least one power conversion device. The output end of the at least one power conversion device is connected to an AC power grid at a point of common coupling. The control device is connected to the at least one power conversion device. Among them, the control device controls the injection of a disturbance signal of the power conversion device. The disturbance signal is used to trigger the power conversion device to output a disturbed alternating current to the AC power grid, and when the disturbance signal is injected, the AC power parameters at the point of common coupling are less than or equal to a first disturbance threshold. The AC power parameters include at least one of the voltage harmonic fluctuation amplitude, the current harmonic fluctuation amplitude, or the power fluctuation amplitude. After the control device controls the injection of the disturbance signal of the power conversion device, it collects a first voltage signal and a first current signal at the point of common coupling, and controls the power conversion device to adjust the alternating current output to the AC power grid based on the first voltage signal and the first current signal. In the present application, by controlling the injection of the disturbance signal of the power conversion device, the control device can make the AC power parameters at the point of common coupling less than or equal to the first disturbance threshold when the disturbance signal is injected. The disturbance of the disturbed alternating current output by the power conversion device to the AC power grid is relatively small, and it will not impact the AC power grid, ensuring the working stability of the AC power grid. Further, the control device can collect the first voltage signal and the first current signal at the point of common coupling when the disturbance signal is injected, and control the power conversion device to adjust the alternating current output to the AC power grid according to the first voltage signal and the first current signal, so that the AC power grid operates stably. Thus, it can be seen that in the present application, the control device can adjust the output of the power conversion device based on the first voltage signal and the first current signal collected at the point of common coupling, so as to adaptively adjust the control of the output of the power conversion device when the AC power grid is in different working conditions, ensuring that the AC power grid can operate stably under different working conditions, with high power supply stability, flexible operation, and strong applicability.

[0006] Combined with the first aspect, in a first possible implementation manner, the grid parameter is the grid impedance. The control device adjusts the phase-locked loop bandwidth or the current loop control parameter of the power conversion device based on the grid impedance of the AC power grid to control the power conversion device to adjust the alternating current output to the AC power grid based on the adjusted phase-locked loop bandwidth or current loop control parameter. In the present application, the control device can collect the first voltage signal and the first current signal at the point of common coupling when the disturbance signal is injected, and identify the grid impedance of the AC power grid according to the first voltage signal and the first current signal. The control device can adjust the phase-locked loop bandwidth or the current loop control parameter of the power conversion device based on the grid impedance to control the power conversion device to adjust the alternating current output to the AC power grid based on the adjusted phase-locked loop bandwidth or current loop control parameter, thereby ensuring the stability margin of the AC power grid.

[0007] In combination with the first aspect, in the second possible implementation manner, the grid parameter is the grid impedance. The control device adjusts the control mode of the power conversion device to the grid-following control mode or the grid-forming control mode based on the grid impedance of the AC grid, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted control mode. In this application, the control device can collect the first voltage signal and the first current signal at the grid connection point under the condition of injecting a disturbance signal, and identify the grid impedance of the AC grid according to the first voltage signal and the first current signal. The control device can adjust the power conversion device to the grid-following control mode or the grid-forming control mode based on the grid impedance, so as to make the AC grid operate stably.

[0008] In combination with the first aspect, in the third possible implementation manner, the grid parameter is the grid inertia parameter. The control device adjusts the inertia time constant of the power conversion device based on the grid inertia parameter of the AC grid, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted inertia time constant. In this application, the control device can collect the first voltage signal and the first current signal at the grid connection point under the condition of injecting a disturbance signal, and identify the grid inertia parameter of the AC grid according to the first voltage signal and the first current signal. The control device can adjust the inertia time constant of the power conversion device based on the grid inertia parameter, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted inertia time constant, thereby improving the frequency support ability of the power conversion device.

[0009] In combination with the first aspect, in the fourth possible implementation manner, the grid parameter is the grid damping parameter. The control device adjusts the virtual impedance parameter or the current loop control parameter of the power conversion device based on the grid damping parameter of the AC grid, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted virtual impedance parameter or the current loop control parameter. In this application, the control device can collect the first voltage signal and the first current signal at the grid connection point under the condition of injecting a disturbance signal, and identify the grid damping parameter of the AC grid according to the first voltage signal and the first current signal. The control device can adjust the virtual impedance parameter or the current loop control parameter of the power conversion device based on the grid damping parameter, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted inertia time constant or the current loop control parameter, thereby ensuring the stable operation of the AC grid.

[0010] In combination with the first aspect, in the fifth possible implementation manner, the grid parameter is the grid damping parameter. The control device adjusts the control mode of the power conversion device to a grid-following control mode or a grid-forming control mode based on the grid damping parameter of the AC grid, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted control mode. In this application, the control device can collect the first voltage signal and the first current signal at the grid connection point under the condition of disturbance signal injection, and identify the grid impedance of the AC grid according to the first voltage signal and the first current signal. The control device can adjust the power conversion device to a grid-following control mode or a grid-forming control mode based on the grid impedance, so as to make the AC grid operate stably.

[0011] In combination with any one of the first possible implementation manner to the fifth possible implementation manner of the first aspect, in the sixth possible implementation manner, when the power conversion device outputs alternating current to the AC grid, the control device obtains a trigger signal for identifying the grid parameter based on the operating parameter and the prediction parameter of the AC grid. When the control device obtains the trigger signal for identifying the grid parameter, it controls the injection of the disturbance signal of the power conversion device. In this application, the control device can collect the operating parameter of the AC grid after obtaining the prediction parameter of the AC grid, and judge whether the grid parameter of the AC grid has changed according to the comparison result of the prediction parameter and the operating parameter of the AC grid. When the grid parameter of the AC grid changes, the control device can obtain the trigger signal for identifying the grid parameter, and control the injection of the disturbance signal of the power conversion device based on the trigger signal, which can improve the detection timeliness of the AC grid fluctuation and perform active response, with more timely response and stronger applicability.

[0012] In combination with any one of the first possible implementation manner to the fifth possible implementation manner of the first aspect, in the seventh possible implementation manner, when the preset measurement time period arrives, the control device obtains a trigger signal for identifying the grid parameter. When the control device obtains the trigger signal for identifying the grid parameter, it controls the injection of the disturbance signal of the power conversion device. In this application, the control device can obtain the trigger signal according to the preset measurement time period, and control the injection of the disturbance signal of the power conversion device according to the trigger signal, so as to identify the grid parameter regularly. The control device adjusts the control method of the power conversion device according to the identified grid parameter to ensure the stable operation of the AC grid under different working conditions.

[0013] In combination with any one of the first possible implementation manner to the seventh possible implementation manner of the first aspect, in the eighth possible implementation manner, when the control device obtains the trigger signal for identifying the grid parameter, it generates a disturbance signal of the power conversion device and injects the disturbance signal into the power conversion device to control the injection of the disturbance signal of the power conversion device.

[0014] Combined with any one of the first to seventh possible implementation manners of the first aspect, in the ninth possible implementation manner, the power conversion device includes a controller and a conversion circuit. When the control device obtains a trigger signal for identifying grid parameters, it triggers the controller to generate a disturbance signal of the conversion circuit and injects the disturbance signal into the conversion circuit to control the injection of the disturbance signal of the power conversion device.

[0015] Combined with the first aspect, in the tenth possible implementation manner, the power supply system includes n power conversion devices, where n is a positive integer. When the control device obtains a trigger signal for identifying grid parameters, it controls the injection of disturbance signals of m power conversion devices among the n power conversion devices, and the disturbance signals are used to trigger the m power conversion devices to output disturbance alternating current to the AC grid; m is a positive integer less than n. Among them, the capacity of any one of the m power conversion devices is greater than the capacity of any one of the remaining power conversion devices other than the m power conversion devices among the n power conversion devices. In this application, when the power supply system includes multiple power conversion devices, the control device can avoid affecting the stable operation of other power conversion devices with smaller capacities among the multiple power conversion devices by controlling the injection of disturbance signals of at least one power conversion device with a larger capacity among the multiple power conversion devices and outputting disturbance alternating current. In addition, by controlling multiple power conversion devices to simultaneously output multiple disturbance alternating currents to the AC grid, the output of disturbance alternating current by one or more power conversion devices can be reduced, ensuring the stable operation of the power conversion devices.

[0016] Combined with any one of the first to tenth possible implementation manners of the first aspect, in the eleventh possible implementation manner, the AC parameter is the voltage harmonic fluctuation amplitude, and the first disturbance threshold is obtained from the voltage harmonic fluctuation amplitude of the first voltage signal and a preset voltage harmonic fluctuation amplitude threshold. In this application, when the power conversion device outputs disturbance alternating current to the AC grid through the grid connection point, the voltage harmonic fluctuation amplitude at the grid connection point is less than or equal to the first disturbance threshold, indicating that the disturbance of the disturbance alternating current is relatively small, and thus it will not cause an impact on the AC grid when outputting the disturbance alternating current to the AC grid, ensuring the stable operation of the AC grid.

[0017] Combined with any one of the first to tenth possible implementation manners of the first aspect, in the twelfth possible implementation manner, the AC parameter is the current harmonic fluctuation amplitude, and the first disturbance threshold is obtained from the current harmonic fluctuation amplitude of the first current signal and a preset current harmonic fluctuation amplitude threshold. In this application, when the power conversion device outputs disturbed alternating current to the AC power grid through the grid connection point, if the current harmonic fluctuation amplitude at the grid connection point is less than or equal to the first disturbance threshold, it indicates that the disturbance of the disturbed alternating current is relatively small, and thus it will not cause an impact on the AC power grid when outputting the disturbed alternating current to the AC power grid, ensuring the stable operation of the AC power grid.

[0018] Combined with any one of the eleventh or twelfth possible implementation manners of the first aspect, in the thirteenth possible implementation manner, the first disturbance threshold is 2%. In this application, when the current harmonic fluctuation amplitude and the voltage harmonic fluctuation threshold at the grid connection point are less than or equal to 2%, the disturbed alternating current will not cause an unacceptable impact on the AC power grid when output to the AC power grid, ensuring the stable operation of the AC power grid.

[0019] Combined with any one of the first to tenth possible implementation manners of the first aspect, in the fourteenth possible implementation manner, the AC parameter is the power fluctuation amplitude, and the first disturbance threshold is obtained from the power fluctuation amplitudes of the first voltage signal and the first current signal, and a preset power fluctuation amplitude threshold. In this application, when the power conversion device outputs disturbed alternating current to the AC power grid through the grid connection point, if the power fluctuation amplitude at the grid connection point is less than or equal to the first disturbance threshold, it indicates that the disturbance of the disturbed alternating current is relatively small, and thus it will not cause an impact on the AC power grid when outputting the disturbed alternating current to the AC power grid, ensuring the stable operation of the AC power grid.

[0020] Combined with the fourteenth possible implementation manner of the first aspect, in the fifteenth possible implementation manner, the first disturbance threshold is 5%. In this application, when the power fluctuation amplitude at the grid connection point is less than or equal to 5%, the disturbed alternating current will not cause an impact on the AC power grid when output to the AC power grid, ensuring the stable operation of the AC power grid.

[0021] Combined with any one of the first to fifteenth possible implementation manners of the first aspect, in the sixteenth possible implementation manner, the disturbance signal is any one of a Gaussian white noise signal or a pseudo-random binary sequence signal. In this application, when the disturbance signals injected by multiple power conversion devices in the power supply system are Gaussian white noise signals or pseudo-random binary sequence signals, the multiple disturbed alternating currents output by the multiple power conversion devices will not produce a cancellation effect due to the same frequency, thus avoiding mutual interference between the multiple disturbed alternating currents output by the multiple power conversion devices.

[0022] Combined with any one of the first to fifteenth possible implementation manners of the first aspect, in the seventeenth possible implementation manner, the disturbance signal is a Gaussian white noise signal with an expected value equal to 0 and a variance equal to 0.001. In the present application, when the disturbance signal injected by the power conversion device is a Gaussian white noise signal with an expected value equal to 0 and a variance equal to 0.001, the energy of the Gaussian white noise signal is small, so the interference of the disturbance alternating current output by the power conversion device controlled by the control device based on the disturbance signal is also small, and thus it will not impact the AC power grid, and the stable operation of the AC power grid can be ensured while the disturbance alternating current is injected into the AC power grid.

[0023] In a second aspect, the present application provides a control method for a power supply system. The power supply system includes at least one power conversion device, and the output end of the at least one power conversion device is connected to the AC power grid at a grid connection point. The method includes: controlling the injection of a disturbance signal of the power conversion device, where the disturbance signal is used to trigger the power conversion device to output disturbance alternating current to the AC power grid, and when the disturbance signal is injected, the AC power parameters at the grid connection point are less than or equal to a first disturbance threshold, and the AC power parameters include at least one of the voltage harmonic fluctuation amplitude, the current harmonic fluctuation amplitude, or the power fluctuation amplitude. After controlling the injection of the disturbance signal of the power conversion device, collecting a first voltage signal and a first current signal at the grid connection point, and controlling the power conversion device to adjust the alternating current output to the AC power grid based on the first voltage signal and the first current signal.

[0024] Combined with the second aspect, in the first possible implementation manner, the grid parameter is the grid impedance. Based on the grid parameter of the AC power grid, controlling the power conversion device to adjust the alternating current output to the AC power grid includes: based on the grid impedance of the AC power grid, adjusting the phase-locked loop bandwidth or the current loop control parameter of the power conversion device, so as to control the alternating current output by the power conversion device to the AC power grid based on the adjusted phase-locked loop bandwidth or the current loop control parameter.

[0025] Combined with the second aspect, in the second possible implementation manner, the grid parameter is the grid impedance. Based on the grid impedance of the AC power grid, adjusting the control mode of the power conversion device to a grid-following control mode or a grid-forming control mode, so as to control the alternating current output by the power conversion device to the AC power grid based on the adjusted control mode.

[0026] Combined with the second aspect, in the third possible implementation manner, the grid parameter is the grid inertia parameter. Based on the grid parameter of the AC power grid, controlling the power conversion device to adjust the alternating current output to the AC power grid includes: the control device is further configured to, based on the grid inertia parameter of the AC power grid, adjust the inertia time constant of the power conversion device, so as to control the alternating current output by the power conversion device to the AC power grid based on the adjusted inertia time constant.

[0027] Combined with the second aspect, in the fourth possible implementation manner, the grid parameter is the grid damping parameter. Based on the grid parameters of the AC grid, controlling the power conversion device to adjust the alternating current output to the AC grid includes: based on the grid damping parameter of the AC grid, adjusting the virtual impedance parameter or the current loop control parameter of the power conversion device, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted virtual impedance parameter or current loop control parameter.

[0028] Combined with the first aspect, in the fifth possible implementation manner, the grid parameter is the grid damping parameter. Based on the grid damping parameter of the AC grid, adjusting the control mode of the power conversion device to the grid-following control mode or the grid-forming control mode, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted control mode.

[0029] Combined with any one of the first possible implementation manner to the fifth possible implementation manner of the second aspect, in the sixth possible implementation manner, when the power conversion device outputs alternating current to the AC grid, based on the working parameters and prediction parameters of the AC grid, obtaining a trigger signal for identifying the grid parameter. When obtaining the trigger signal for identifying the grid parameter, controlling the injection of the disturbance signal of the power conversion device.

[0030] Combined with any one of the first possible implementation manner to the fifth possible implementation manner of the second aspect, in the seventh possible implementation manner, when a preset measurement time period arrives, obtaining a trigger signal for identifying the grid parameter. When obtaining the trigger signal for identifying the grid parameter, controlling the injection of the disturbance signal of the power conversion device.

[0031] Combined with any one of the first possible implementation manner to the seventh possible implementation manner of the second aspect, in the eighth possible implementation manner, when obtaining the trigger signal for identifying the grid parameter, controlling the injection of the disturbance signal of the power conversion device includes: when obtaining the trigger signal for identifying the grid parameter, generating a disturbance signal of the power conversion device and injecting the disturbance signal into the power conversion device, so as to control the injection of the disturbance signal of the power conversion device.

[0032] Combined with any one of the first possible implementation manner to the seventh possible implementation manner of the second aspect, in the ninth possible implementation manner, the power conversion device includes a controller and a conversion circuit. When obtaining the trigger signal for identifying the grid parameter, controlling the injection of the disturbance signal of the power conversion device includes: when obtaining the trigger signal for identifying the grid parameter, triggering the controller to generate a disturbance signal of the conversion circuit and injecting the disturbance signal into the conversion circuit, so as to control the injection of the disturbance signal of the power conversion device.

[0033] In combination with the second aspect, in the tenth possible implementation manner, the power supply system includes n power conversion devices, where n is a positive integer. When obtaining a trigger signal for identifying grid parameters, controlling the injection of disturbance signals of the power conversion devices includes: when obtaining a trigger signal for identifying grid parameters, controlling the injection of disturbance signals of m power conversion devices among the n power conversion devices, where the disturbance signals are used to trigger the m power conversion devices to output disturbance alternating current to the AC grid; m is a positive integer less than n. The capacity of any one of the m power conversion devices is greater than the capacity of any one of the remaining power conversion devices among the n power conversion devices except for the m power conversion devices.

[0034] In combination with any one of the first possible implementation manner to the tenth possible implementation manner of the second aspect, in the eleventh possible implementation manner, the AC parameter is the voltage harmonic fluctuation amplitude, and the first disturbance threshold is obtained from the voltage harmonic fluctuation amplitude of the first voltage signal and a preset voltage harmonic fluctuation amplitude threshold.

[0035] In combination with any one of the first possible implementation manner to the tenth possible implementation manner of the second aspect, in the twelfth possible implementation manner, the AC parameter is the current harmonic fluctuation amplitude, and the first disturbance threshold is obtained from the current harmonic fluctuation amplitude of the first current signal and a preset current harmonic fluctuation amplitude threshold.

[0036] In combination with any one of the eleventh possible implementation manner or the twelfth possible implementation manner of the second aspect, in the thirteenth possible implementation manner, the first disturbance threshold is 2%.

[0037] In combination with any one of the first possible implementation manner to the tenth possible implementation manner of the second aspect, in the fourteenth possible implementation manner, the AC parameter is the power fluctuation amplitude, and the first disturbance threshold is obtained from the power fluctuation amplitude of the first voltage signal and the first current signal, and a preset power fluctuation amplitude threshold.

[0038] In combination with the fourteenth possible implementation manner of the second aspect, in the fifteenth possible implementation manner, the first disturbance threshold is 5%.

[0039] In combination with any one of the first possible implementation manner to the fifteenth possible implementation manner of the second aspect, in the sixteenth possible implementation manner, the disturbance signal is any one of a Gaussian white noise signal or a pseudo-random binary sequence signal.

[0040] In combination with any one of the first possible implementation manner to the fifteenth possible implementation manner of the second aspect, in the seventeenth possible implementation manner, the disturbance signal is a Gaussian white noise signal with an expected value equal to 0 and a variance equal to 0.001.

[0041] It should be understood that the implementation and beneficial effects of the above-mentioned multiple aspects of this application can be referred to each other. Description of the Drawings

[0042] Figure 1 It is a schematic structural diagram of a new energy power station provided by an embodiment of this application;

[0043] Figure 2 It is a schematic structural diagram of a power supply system provided by an embodiment of this application;

[0044] Figure 3 It is another schematic structural diagram of a power supply system provided by an embodiment of this application;

[0045] Figure 4a It is a schematic diagram of the grid impedance of an AC power grid provided by an embodiment of this application;

[0046] Figure 4b It is a schematic diagram of the virtual inertia parameters of a power supply system provided by an embodiment of this application;

[0047] Figure 5a It is a schematic diagram of the power fluctuation of a conventional power supply system;

[0048] Figure 5b It is a schematic diagram of the power fluctuation of a power supply system provided by an embodiment of this application;

[0049] Figure 6 It is a schematic flowchart of a control method for a power supply system provided by this application. Detailed Embodiments

[0050] It should be noted that in a traditional power system, a synchronous generator is connected to an AC power grid through a connection point, and can adjust the voltage of the AC power grid when the voltage of the AC power grid fluctuates greatly, ensuring that the AC power grid can provide a stable voltage to the load. Among them, the above-mentioned power system can be a national power system, a household power grid, an enterprise power grid or other AC power systems, which are not limited in this application.

[0051] With the continuous development of renewable energy, new energy power supply systems and energy storage power supply systems, etc. have gradually replaced traditional synchronous generators. Compared with traditional synchronous generators, new energy power supply systems or energy storage power supply systems, etc. need to be connected to the grid through power conversion equipment. Among them, the power conversion equipment can convert the direct current output by the power supply system (i.e., the new energy power supply system or the energy storage power supply system) into alternating current and then output it for use by the AC power grid. However, the alternating current output by the power conversion equipment fluctuates greatly, which will cause the voltage of the AC power grid to fluctuate greatly, thereby affecting the stability of the AC power grid to supply power to the load.

[0052] Therefore, in order to ensure the stability of the AC power grid, generally, for the scenario of integrating a power conversion model into a conventional power grid model, modeling design, simulation, and analysis can be carried out to determine the control strategy of the power conversion device. Further, based on this control strategy, the alternating current output by the power conversion device to the AC power grid can be controlled to achieve stable power supply to the AC power grid. Exemplarily, the conventional power grid model represents the AC power grid with a fixed impedance and a voltage source (infinite power source) with a fixed frequency and voltage. And in the scenario of integrating the power conversion device into this AC power grid, the design of the grid connection control strategy, model modeling, and analysis are carried out to determine the control strategy of the power conversion device. However, since the grid parameters of the AC power grid will change with different operating conditions, the above-mentioned way of representing the AC power grid in the conventional power grid model is not applicable to the AC power grid under different operating conditions, and the fixed control strategy of the power conversion device determined based on this power grid model cannot adapt to the AC power grid under different operating conditions either. It should be noted that the above-mentioned fixed control strategy of the power conversion device can be understood as the control strategy of the power conversion device obtained by carrying out modeling design, simulation, and analysis with the scenario of integrating the power conversion device into a fixed power grid model. The above-mentioned grid parameters of the AC power grid can be understood as the parameters used to characterize the characteristics of the AC power grid. When the AC power grid is in different operating conditions, the grid parameters will also change. Therefore, the grid parameters of the AC power grid can be used to reflect different operating conditions of the AC power grid.

[0053] Exemplarily, in some application scenarios, when the AC power grid does not meet the assumption of an infinite power source, if the above-mentioned fixed control strategy of the power conversion device is still used to control the power conversion device, the optimal control effect cannot be achieved, and the stable operation of the AC power grid cannot be controlled.

[0054] Generally speaking, since the conventional control strategy of the power conversion device is designed with the scenario of integrating the power conversion device into a fixed power grid model, this fixed power grid model cannot accurately represent the AC power grid with changing grid parameters under different operating conditions. Therefore, the conventional control strategy of the power conversion device is only applicable to the AC power grid with unchanged grid parameters and cannot be adaptively adjusted when the grid parameters of the AC power grid change, resulting in poor stability of the AC power grid under different operating conditions.

[0055] Based on the above-mentioned technical problems, the embodiments of the present application provide a power supply system that can ensure the stable operation of the AC power grid under different operating conditions when integrated into the AC power grid.

[0056] The power supply system provided by this application can be applied to various application fields such as new energy intelligent microgrid field, power transmission and distribution field, new energy field (such as photovoltaic grid-connected field, wind power grid-connected field), photovoltaic power generation field, energy storage power generation field, wind power generation field, flexible power transmission field, etc. Exemplarily, the power supply system provided by this application can be a new energy power station, an energy storage power station, a flexible power transmission system or a microgrid, etc., which is applicable to different application scenarios. For example, photovoltaic power supply scenarios (including large-scale photovoltaic power station scenarios, small and medium-sized distributed photovoltaic power station scenarios and user photovoltaic system scenarios, etc.), energy storage power supply scenarios (including large-scale energy storage power station scenarios, small and medium-sized distributed energy storage power station scenarios and user photovoltaic and energy storage power generation system scenarios, etc.), Uninterrupted Power Supply (UPS) power supply scenarios, etc. For ease of understanding, the following takes the power supply system as a new energy power station and the application scenario as a photovoltaic power supply scenario as an example for illustration.

[0057] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of the new energy power station provided by an embodiment of this application. Figure 1 The new energy power station 100 shown includes a photovoltaic array 110, a photovoltaic inverter 120, and a control device 130. The output end of the above photovoltaic array 110 can be connected to the input end of the photovoltaic inverter 120 (or the DC end of the photovoltaic inverter 120), and the output end of the photovoltaic inverter 120 (or the AC end of the photovoltaic inverter 120) is connected to the AC power grid. Among them, the AC power grid refers to an AC network composed of substations and power transmission and distribution lines of various voltages, which can provide industrial frequency alternating current for loads. This AC power grid can be a single-phase AC power grid or a three-phase AC power grid, and the embodiments of this application do not make specific limitations on this.

[0058] In Figure 1 the new energy power station 100 shown, the above photovoltaic array 110 can be composed of one or more photovoltaic strings connected in parallel, and one photovoltaic string can be obtained by connecting one or more photovoltaic modules in series. The photovoltaic array 110 can convert light energy into electrical energy and transmit the generated electrical energy to the input end of the photovoltaic inverter 120 in the form of direct current, or transmit it to the energy storage battery for storage.

[0059] Furthermore, the control device 130 in the new energy power station 100 can control the photovoltaic inverter 120 to invert the direct current input at its input end into alternating current, and provide the alternating current obtained after inversion to the AC power grid, and then can supply power to loads (which can be electrical equipment such as storage batteries, communication base stations or household equipment).

[0060] Meanwhile, in the new energy power station 100 provided by the embodiments of the present application, when the grid parameters of the AC grid change, the control device 130 can trigger the injection of a disturbance signal into the photovoltaic inverter 120, so that the photovoltaic inverter 120 converts the direct current provided by the photovoltaic array 110 into a disturbed alternating current based on the disturbance signal and outputs it to the AC grid through the grid connection point. In the case of injecting the disturbance signal, the AC parameters at the grid connection point are less than or equal to the first disturbance threshold, that is, the disturbance of the disturbed alternating current output by the photovoltaic inverter 120 to the AC grid is relatively small and will not impact the AC grid. Further, the control device 130 can collect the first voltage signal and the first current signal at the grid connection point in the case of injecting the disturbance signal, and identify the grid parameters of the AC grid according to the first voltage signal and the first current signal. The control device 130 can control the photovoltaic inverter 120 to adjust the alternating current output to the AC grid based on the identified grid parameters of the AC grid, so that the AC grid operates stably. At the same time, the control device 130 can adjust the control strategy of the photovoltaic inverter 120 based on the identified grid parameters of the AC grid, so as to adaptively adjust the control strategy of the photovoltaic inverter 120 when the AC grid is in different working conditions, and ensure that the AC grid can operate stably under different working conditions.

[0061] It should be noted that in some application scenarios, the control device and the photovoltaic inverter can be independent devices, and the control device can be arranged inside or outside the photovoltaic inverter. Or, in some other cases, the control device can also be a relevant control device inside the photovoltaic inverter, such as an integrated circuit (IC), etc. The above control device 130 can be a digital signal processing (DSP) unit, a field programmable gate array (FPGA), a microcontroller unit (MCU), or other devices with computing and control functions.

[0062] The above is only an example of the application scenario of the power supply system provided by the present application, rather than an exhaustive list, and the present application does not limit the application scenario.

[0063] The following Figures 2 to 5b is an example to illustrate the working principle of the power supply system provided by the present application.

[0064] Please refer to Figure 2 , Figure 2 which is a schematic structural diagram of the power supply system provided by the embodiments of the present application. As Figure 2As shown, the power supply system 200 includes a DC power supply 210, a power conversion device 220, and a control device 230. Among them, the input terminal i1 of the power conversion device 220 is used to connect to the DC power supply 210, and the output terminal i2 is connected to the AC power grid at the grid connection point. This grid connection point can be understood as the connection point between the power conversion device 220 and the AC power grid. The control device 230 in the power supply system 200 can control the power conversion device 220 to invert and convert the DC power input from the input terminal i1 into AC power, and output the AC power to the AC power grid through the output terminal i2, so as to realize the power supply of the power supply system 200 to the AC power grid.

[0065] It should be noted that in the photovoltaic power supply scenario, the power supply system 200 provided by the present application can be Figure 1 the new energy power station 100 shown in the figure. Then, the DC power supply 210 in the power supply system 200 can be Figure 1 the photovoltaic array 110 shown in the figure. In other alternative application scenarios, the above DC power supply 210 can also be a wind power DC source or a storage battery, etc. The present application does not list them one by one here.

[0066] The above power conversion device 220 can be an inverter (including string inverters and centralized inverters), a rectifier, an energy storage converter, a modular multilevel power converter, or other power converters, which are not limited in the present application. Exemplarily, in the photovoltaic power supply scenario, the above power conversion device 220 can be Figure 1 the photovoltaic inverter 120 shown in the figure. In addition, if the DC power supply 210 connected to the power conversion device 220 is a storage battery, the power conversion device 220 can also be an energy storage converter.

[0067] It should be noted that in some application scenarios, the control device and the power conversion device can be independent devices, and the control device can be arranged inside or outside the power conversion device. Or, in some other cases, the control device can also be a relevant control device inside the power conversion device, such as an integrated circuit (IC), etc. Exemplarily, in the case where the power supply system includes multiple power conversion devices, the above control device is the main control device of the power supply system, which is independent of the power conversion device and is arranged outside the power conversion device. In the case where the power supply system includes one power conversion device, the above control device is a relevant control device inside the power conversion device.

[0068] In some feasible embodiments, the power supply system 200 provided by the embodiments of the present application can adjust the alternating current output to the AC power grid when the grid parameters of the AC power grid change, that is, when the grid parameters of the AC power grid change, and then can adjust the grid parameters of the AC power grid to make the AC power grid operate stably. To facilitate understanding of the working principle of the power supply system, the following content first introduces the adjustment process of the power supply system to the AC power grid.

[0069] In some feasible embodiments, when the AC power grid supplies power to a load, since the load usually has a rated operating voltage and operating frequency, in order to ensure the stable operation of the load, the AC power grid can supply the load with alternating current that meets the rated operating voltage and rated operating frequency of the load, and maintain the voltage and frequency stable during power supply. Exemplarily, assuming that the rated operating voltage of the load is 220V and the rated operating frequency is 50Hz, then the voltage of the AC power grid when supplying power to the load is 220V and the frequency is 50Hz, which can make the load operate stably. When the grid parameters of the AC power grid change, the voltage and frequency of the AC power grid supplying power to the load will both fluctuate. At this time, if the voltage fluctuation range or frequency fluctuation range of the AC power grid supplying power to the load exceeds the tolerance range of the load, it will cause the load to be unable to operate stably. For this reason, in addition to converting the direct current output by the DC power supply into alternating current through the power conversion device 220 to supply power to the AC power grid, the power supply system 200 provided by the embodiments of the present application can also adjust the voltage or frequency of the alternating current output to the AC power grid when the grid parameters of the AC power grid change, and then adjust the voltage or frequency of the AC power grid, etc., to ensure the stability of the AC power grid supplying power to the load.

[0070] In some feasible embodiments, the power supply system 200 can control the power conversion device 220 through the control device 230 to achieve the adjustment of the output alternating current. Specifically, the control device 230 can control the power conversion device 220 to adjust the voltage, current, or power of the output alternating current, etc. Further, when the power conversion device 220 inputs the adjusted alternating current into the AC power grid through the grid connection point, since the voltage, current, or power of the alternating current input into the AC power grid has been adjusted, the voltage, current, or power of the AC power grid will also be adjusted.

[0071] Exemplarily, when the voltage of the AC power grid drops, the control device 230 can control the power conversion device 220 to increase the voltage of the output AC power when the power conversion device 220 performs an inversion conversion on the DC power. Then the voltage of the AC power input to the AC power grid increases, and thus the voltage drop of the AC power grid can be supported, so that the voltage of the AC power grid is maintained within a certain voltage range. Similarly, when the current of the AC power grid drops, the control device 230 can control the power conversion device 220 to increase the current of the output AC power when the power conversion device 220 performs an inversion conversion on the DC power. Then the current of the AC power input to the AC power grid increases, and thus the current drop of the AC power grid can be controlled, so that the current of the AC power grid is maintained within a certain current range. Similarly, when the frequency of the AC power grid increases, the control device 230 can control the power conversion device 220 to decrease the frequency of the output AC power when the power conversion device 220 performs an inversion conversion on the DC power. Then the frequency of the AC power input to the AC power grid drops, and thus the frequency of the AC power grid can be controlled, so that the frequency of the AC power grid is stabilized within a certain frequency range.

[0072] It should be noted that when the above control device 230 controls the power conversion device 220 to adjust the voltage, current or power of the AC power grid to be maintained within a certain range, the specific range of the voltage, current or power can be adjusted according to the actual application scenario, and the present application does not limit this. Exemplarily, assuming that the rated operating voltage of the AC power grid supplying power to the load is 220V, the control device 230 can control the power conversion device 220 to adjust the voltage of the AC power grid to be maintained at 220V. Assuming that the rated operating frequency of the AC power grid supplying power to the load is 50Hz, the control device 230 can control the power conversion device 220 to adjust the frequency of the AC power grid to be maintained at 50Hz. Generally speaking, when the grid parameters of the AC power grid change, the power supply system 200 can control the power conversion device 220 through the control device 230 to adjust the voltage, current or power of the output AC power, etc., to ensure the stability of the AC power grid.

[0073] In some feasible embodiments, the control device 230 provided in the embodiments of the present application can control the power conversion device 220 by adopting different control strategies for the AC power grid under different working conditions. That is to say, for the AC power grid under different working conditions, the control strategy for the control device 230 to control the power conversion device 220 in the embodiments of the present application can be adaptively adjusted, so that the AC power grid can be accurately regulated when the grid parameters of the AC power grid change. It should be noted that when the grid parameters of the AC power grid change, the operating state of the AC power grid also changes. Therefore, in order to ensure the stable operation of the AC power grid under different working conditions, the control device 230 can detect whether the operating state of the AC power grid has changed, and then, when the operating state of the AC power grid changes, it can be determined that the grid parameters of the AC power grid have changed, and then the control strategy for the power conversion device 220 can be adjusted.

[0074] In some feasible embodiments, the control device 230 can determine whether the operating state of the AC power grid has changed according to the comparison result between the predicted parameters of the AC power grid and the working parameters of the AC circuit actually collected. Among them, the working parameters of the AC power grid can be understood as the voltage parameters, current parameters or power parameters, etc. of the AC power grid when the AC power grid is operating normally. The predicted parameters of the AC power grid refer to the voltage parameters, current parameters or power parameters, etc. of the AC power grid at different future moments predicted by the control device 230. Exemplarily, when the control device 230 includes a grid model, the control device 230 can predict the future working parameters of the AC power grid based on this grid model, and then obtain the predicted parameters of the AC power grid at different future moments. Among them, the above grid model can be pre-established by the control device 230 according to the historical parameters of the AC power grid. The historical parameters of this AC power grid can be understood as the working parameters of the AC power grid at different past moments. Or, this grid model can also be a model calculated and matched by the control device 230 according to the current working parameters of the AC power grid when the AC power grid is operating. It should be noted that in addition to the above grid model, the control device 230 can also obtain the predicted parameters of the AC power grid according to other feasible prediction methods. The above is only an example and does not constitute a limitation to the embodiments of the present application.

[0075] It can be understood that if the AC power grid operates stably, the operating parameters of the AC power grid at different future times will be consistent with the predicted parameters at the corresponding times. For this reason, after obtaining the predicted parameters of the AC power grid at different future times, the control device 230 can collect the operating parameters of the AC power grid during the operation of the AC power grid and compare the collected operating parameters with the predicted parameters at the corresponding times. It can be understood that when the collected operating parameters are consistent with the predicted parameters at the corresponding times, it indicates that the AC power grid is in a stable operating state, that is, the operating state of the AC power grid has not changed. On the contrary, when the collected operating parameters are inconsistent with the predicted parameters at the corresponding times, it indicates that the AC power grid is in an unstable operating state, that is, the operating state of the AC power grid has changed.

[0076] It should be noted that the specific implementation of the control device 230 to determine whether the operating parameters of the AC power grid are consistent with the predicted parameters according to the comparison result of the operating parameters and the predicted parameters of the AC power grid can be adjusted according to the requirements of the application scenario, and the embodiments of the present application do not limit this. Exemplarily, in some application scenarios, assuming that the collected operating parameters of the AC power grid are equal to the predicted parameters, it can be considered that the operating parameters of the AC power grid are consistent with the predicted parameters. Or, assuming that the difference between the collected operating parameters of the AC power grid and the predicted parameters is small, it can also be considered that the operating parameters of the AC power grid are consistent with the predicted parameters. Similarly, assuming that the difference between the collected operating parameters of the AC power grid and the predicted parameters is large, it can be considered that the operating parameters of the AC power grid are inconsistent with the predicted parameters. Or, assuming that the difference between the collected operating parameters of the AC power grid and the predicted parameters is small but not equal, it can also be considered that the operating parameters of the AC power grid are inconsistent with the predicted parameters. It can be understood that the above are only examples and do not constitute a limitation to the embodiments of the present application.

[0077] Furthermore, in order to enable the control device 230 to respond in a timely manner when the operating state of the AC power grid changes, in the embodiments of the present application, the control device 230 can collect the operating parameters of the AC power grid at regular intervals and determine whether the operating state of the AC power grid has changed when it detects that the operating parameters of the AC power grid are inconsistent with the predicted parameters. Specifically, the control device 230 can obtain the operating parameters of the AC power grid by collecting parameters such as voltage and current at the grid connection point where the power conversion device 220 is connected to the AC power grid. Or, the control device 230 can also be communicatively connected to a collection device, and the collection device can collect parameters such as voltage and current at the grid connection point and send the collected voltage, current and other parameters to the control device 230, so that the control device 230 can obtain the operating parameters of the AC power grid based on the voltage, current and other parameters at the grid connection point. It can be understood that the above are only examples and do not constitute a limitation to the embodiments of the present application.

[0078] Exemplarily, assume that the operating parameters of the above AC power grid include the voltage signal of the AC power grid. Based on the power grid model, the control device 230 can obtain the predicted parameters of the AC power grid from the current moment to a future time period, and the predicted parameter is the predicted voltage signal of the AC power grid. Starting from the current moment, the control device 230 can collect the voltage of the AC power grid and compare the collected voltage signal with the above predicted voltage signal. If the voltage signal collected by the control device 230 is 210V, and the predicted voltage signal at the corresponding moment of this voltage signal is also 210V, that is, the voltage signal of the AC power grid is consistent with the predicted voltage signal. At this time, the control device 230 can determine that the operating state of the AC power grid has not changed, or the change generated is small and will not affect the stability of the AC power grid. On the contrary, if the voltage signal collected by the control device 230 is 180V, and the predicted voltage signal at the corresponding moment of this voltage signal is 220V, that is, the voltage signal of the AC power grid is inconsistent with the predicted voltage signal and the difference is large. At this time, the control device 230 can determine that the operating state of the AC power grid has changed and the stability of the AC power grid is affected. In some application scenarios, the above operating parameters and predicted parameters of the AC power grid can also be other types of parameters, such as the current signal or power signal of the AC power grid, etc., and the embodiments of the present application will not list them one by one here.

[0079] In some feasible implementation manners, when the control device 230 determines whether the operating state of the AC power grid has changed according to the comparison result of the operating parameters and predicted parameters of the AC power grid, it can simultaneously compare multiple types of operating parameters and their corresponding predicted parameters, rather than being limited to comparing only one type of operating parameter and predicted parameter. For example, the control device 230 can simultaneously determine whether the operating state of the AC power grid has changed according to the comparison result of the voltage signal and predicted voltage signal of the AC power grid, and the comparison result of the current signal and predicted current signal. It can be understood that the above is only an example and does not constitute a limitation to the embodiments of the present application.

[0080] In some feasible implementation manners, as can be seen from the above content, the control device 230 can detect whether the operating state of the AC power grid has changed. Further, when the operating state of the AC power grid changes, the control device 230 can determine that the grid parameters of the AC power grid have changed and the control strategy of the power conversion device 220 needs to be adjusted to ensure the stability of the AC power grid. It can be understood that the grid parameters of the AC power grid can be used to characterize the AC power grid in different working conditions. Therefore, when the operating state of the AC power grid changes, the control device 230 can first identify the grid parameters of the AC power grid.

[0081] It can be understood that in order for the control device 230 to identify the grid parameters of the AC power grid when the operating state of the AC power grid changes, when the operating state of the AC power grid changes, the control device 230 can obtain a trigger signal and, triggered by this trigger signal, identify the grid parameters. The above trigger signal can be understood as a signal for triggering the control device 230 to identify the grid parameters.

[0082] Exemplarily, after the control device 230 determines that the operating state of the AC power grid has changed based on the working parameters and predicted parameters of the above AC power grid, the control device 230 can generate a trigger signal, obtain the grid parameters for identifying the AC power grid according to this trigger signal, and adjust the control strategy of the power conversion device 220 based on the identified grid parameters, thereby ensuring the stable operation of the AC power grid under different working conditions.

[0083] Generally speaking, the control device 230 can collect the working parameters of the AC power grid and compare these working parameters with the predicted parameters to determine whether the operating state of the AC power grid has changed. When the operating state of the AC power grid changes, in order for the control device 230 to adjust the control strategy of the power conversion device 220 based on the grid parameters of the AC power grid, the control device 230 can obtain a trigger signal for identifying the grid parameters to trigger the identification of the grid parameters of the AC power grid.

[0084] In some feasible implementation manners, as can be seen from the above, the grid parameters of the AC power grid can be used to represent the AC power grid in different working conditions. Then, the control device 230 can judge whether the operating state of the AC power grid has changed according to the grid parameters of the AC power grid and adjust the control strategy of the power conversion device 220 when the operating state of the AC power grid changes. Specifically, after the power supply system 200 and the AC power grid start to work, the control device 230 can periodically generate a trigger signal, trigger the identification of the grid parameters of the AC power grid based on this trigger signal, and judge whether the operating state of the AC power grid has changed according to the identified grid parameters.

[0085] In some feasible embodiments, the control device 230 may generate a trigger signal at regular intervals according to a preset measurement time period to trigger the identification of the grid parameters of the AC power grid. Herein, the above-mentioned measurement time period can be understood as the time length from the current moment when the control device 230 identifies the grid parameters to the next time when the control device 230 identifies the grid parameters. Exemplarily, assuming that the above-mentioned measurement time period is half an hour, then after the power supply system 200 and the AC power grid start to operate, every half an hour, the control device 230 will generate a trigger signal once, and trigger the identification of the grid parameters of the AC power grid based on this trigger signal. Similarly, assuming that the above-mentioned measurement time period is one hour, then after the power supply system 200 and the AC power grid start to operate, every hour, the control device 230 will generate a trigger signal once, and trigger the identification of the grid parameters of the AC power grid based on this trigger signal. Similarly, assuming that the above-mentioned measurement time period is one day, then after the power supply system 200 and the AC power grid start to operate, every 24 hours, the control device 230 will generate a trigger signal once, and trigger the identification of the grid parameters of the AC power grid based on this trigger signal. It can be understood that the above are only examples and do not constitute a limitation to the embodiments of the present application.

[0086] Generally speaking, the control device 230 may determine whether the operating state of the AC power grid has changed according to the comparison result between the operating parameters and the predicted parameters of the AC power grid, and then may generate a trigger signal when the operating state of the AC power grid changes to trigger the control device to identify the grid parameters of the AC power grid. Or, the control device may generate a trigger signal when the measurement time period arrives, that is, generate a trigger signal at regular intervals, to trigger the control device to identify the grid parameters of the AC power grid.

[0087] In some feasible embodiments, the control device 230 may identify the grid parameters of the AC power grid under the condition that the AC power grid generates interference. For this purpose, after the control device obtains the trigger signal, first, the control device 230 may control the injection of the disturbance signal of the power conversion device 220, so that the power conversion device 220 converts the direct current provided by the DC power supply 210 into a disturbance alternating current based on this disturbance signal. It can be understood that this disturbance alternating current can be understood as the alternating current output by the power conversion device 220 when the disturbance signal is injected. Further, the power conversion device 220 may transmit this disturbance alternating current to the AC power grid through the above-mentioned grid connection point, thereby causing interference to the AC power grid.

[0088] In some feasible embodiments, the power supply system may only include one power conversion device and one control device. For example, as Figure 2The power supply system 200 shown includes a power conversion device 220 and a control device 230. At this time, the control device 230 can be understood as the relevant control device within the power conversion device, such as an IC, etc. When the control device 230 obtains a trigger signal, the control device 230 can generate the above-mentioned disturbance signal and inject the disturbance signal into the power conversion device 220.

[0089] In some feasible embodiments, the power supply system may include multiple power conversion devices and one control device. At this time, the specific implementation of the power supply system can be as Figure 3 shown. Specifically, please refer to Figure 3 , Figure 3 which is another schematic structural diagram of the power supply system provided by the embodiments of the present application. Figure 3 The power supply system 300 shown includes a control device 330 and multiple DC power supplies: DC power supply 310a, DC power supply 310b,... and DC power supply 310n. It also includes multiple power conversion devices 320a, power conversion device 320b,... and power conversion device 320n. Among them, the input end i11 of the power conversion device 320a is connected to the DC power supply 310a, and the output end i12 of the power conversion device 320a is connected to the AC power grid at the grid connection point. The input end i21 of the power conversion device 320b is connected to the DC power supply 310b, and the output end i22 of the power conversion device 320b is connected to the AC power grid at the grid connection point. The input end in1 of the power conversion device 320n is connected to the DC power supply 310n, and the output end in2 of the power conversion device 320n is connected to the AC power grid at the grid connection point. The control device is connected to the above-mentioned power conversion devices 320a, power conversion device 320b, and power conversion device 320n.

[0090] It should be noted that Figure 3 the control device 330 shown can be understood as the main control device of the power supply system, which is independent of the power conversion device and is arranged outside the power conversion device.

[0091] The above-mentioned power conversion device 320a includes a controller 321a and a conversion circuit 322a. One end of the conversion circuit 322a is connected to the above-mentioned input terminal i11, the other end of the conversion circuit 322a is connected to the above-mentioned output terminal i12, and the controller 321a is connected to the conversion circuit 322a. The above-mentioned power conversion device 320b includes a controller 321b and a conversion circuit 322b. One end of the conversion circuit 322b is connected to the above-mentioned input terminal i21, the other end of the conversion circuit 322b is connected to the above-mentioned output terminal i22, and the controller 321b is connected to the conversion circuit 322b. The above-mentioned power conversion device 320n includes a controller 321n and a conversion circuit 322n. One end of the conversion circuit 322n is connected to the above-mentioned input terminal in1, the other end of the conversion circuit 322n is connected to the above-mentioned output terminal in2, and the controller 321n is connected to the conversion circuit 322n. Among them, the controller in each of the above-mentioned power conversion devices is used to control the conversion circuit to invert and convert direct current into alternating current.

[0092] It should be noted that Figure 3 The controller shown can be understood as a relevant control device within the power conversion device, such as an IC, etc., which is provided inside the power conversion device.

[0093] In some feasible embodiments, since the capacities of different power conversion devices can be different, the abilities of different power conversion devices to invert and convert direct current into perturbed alternating current based on a perturbation signal are different. Among them, the capacity of the power conversion device can be understood as the maximum power of the power conversion device. It can be understood that the larger the maximum power of the power conversion device, the larger the capacity of the power conversion device. When inverting and converting direct current into perturbed alternating current of the same power based on the perturbation signal, the impact on the stable operation of the power conversion device is smaller. On the contrary, it can be understood that the smaller the maximum power of the power conversion device, the smaller the capacity of the power conversion device. When inverting and converting direct current into perturbed alternating current of the same power based on the perturbation signal, the impact on the stable operation of the power conversion device is greater. Therefore, in order to ensure the stable operation of the power conversion device, when Figure 3 In the case where the power supply system 300 shown includes multiple power conversion devices, the control device 330 can select at least one power conversion device with a larger capacity among the multiple power conversion devices to inject a perturbation signal and output perturbed alternating current, thereby avoiding affecting the stable operation of the power conversion devices with smaller capacities among the multiple power conversion devices.

[0094] It can be understood that in the power supply system 300 as shown in Figure 3 The control device 330 can obtain the capacity of each power conversion device and sort the multiple power conversion devices in descending order based on the capacity of the power conversion devices.

[0095] Further, when the control device 330 obtains a trigger signal for identifying grid parameters, the control device 330 may send the trigger signal to the controller of the power conversion device with a larger capacity among the above-mentioned multiple power conversion devices. The controller that receives the trigger signal may generate a disturbance signal and inject it into the conversion circuit of the power conversion device. It can be understood that the conversion circuit may invert the direct current provided by the corresponding DC power supply into a disturbed alternating current based on the injected disturbance signal and transmit it to the AC grid through the above-mentioned grid connection point. It should be noted that other controllers that do not receive the trigger signal will not generate a disturbance signal and inject it into the corresponding conversion circuit, so the alternating current output by the conversion circuit is an undisturbed alternating current.

[0096] Exemplarily, assume that the capacity of the above-mentioned power conversion device 320a is a1, the capacity of the power conversion device 320b is a2, and the capacity of the power conversion device 320n is an, and a1 > a2 > an. Then the control device 330 may sort the above three power conversion devices to obtain: the power conversion device 320a, the power conversion device 320b with a capacity of a2, and the power conversion device 320n. Further, when the control device 330 obtains a trigger signal for identifying grid parameters, the control device 330 may, based on the capacity order of the above three power conversion devices, send the trigger signal to the power conversion device 320a with the largest capacity among the above. After receiving the trigger signal, the controller 321a in the power conversion device 320a may generate a disturbance signal and inject it into the conversion circuit 322a of the power conversion device 320a. At this time, the controllers of the power conversion device 320b and the power conversion device 320n do not inject a disturbance signal into the conversion circuit because they do not receive the trigger signal.

[0097] Alternatively, when the control device 330 obtains a trigger signal for identifying grid parameters, the control device 330 may, based on the capacity order of the above three power conversion devices, send the trigger signal to the power conversion device 320a and the power conversion device 320b with a larger capacity among the above. At this time, after receiving the trigger signal, the controller 321a in the power conversion device 320a may generate a disturbance signal and inject it into the conversion circuit 322a of the power conversion device 320a. At the same time, after receiving the trigger signal, the controller 321b in the power conversion device 320b may generate a disturbance signal and inject it into the conversion circuit 322b of the power conversion device 320b. At this time, the controller 321n of the power conversion device 320n does not inject a disturbance signal into the conversion circuit 322n because it does not receive the trigger signal.

[0098] Alternatively, when the control device 330 obtains a trigger signal for identifying grid parameters, the control device 330 may send the trigger signal to the power conversion device 320a, the power conversion device 320b, and the power conversion device 320n. At this time, after receiving the trigger signal, the controller 321a in the power conversion device 320a may generate a disturbance signal and inject it into the conversion circuit 322a of the power conversion device 320a. At the same time, after receiving the trigger signal, the controller 321b in the power conversion device 320b may generate a disturbance signal and inject it into the conversion circuit 322b of the power conversion device 320b. At the same time, after receiving the trigger signal, the controller 321n in the power conversion device 320n may generate a disturbance signal and inject it into the conversion circuit 322n of the power conversion device 320n.

[0099] That is to say, the control device 330 may send the trigger signal to the power conversion device with a larger capacity among multiple power conversion devices to control at least one power conversion device to inject a disturbance signal. Alternatively, the trigger signal may also be sent to all the power conversion devices among the multiple power conversion devices to control all the power conversion devices to inject a disturbance signal. Specifically, the number of disturbance signals injected by the control device 330 to control the power conversion device may be adjusted according to actual service requirements, and the embodiments of the present application do not limit this.

[0100] In some feasible embodiments, when the capacities of multiple power conversion devices included in the power supply system are the same, the control device 330 may select one or more power conversion devices from the multiple power conversion devices to inject a disturbance signal according to actual service requirements, and the embodiments of the present application do not limit this.

[0101] Exemplarily, it is assumed that the capacities of the above-mentioned multiple power conversion devices are the same. In some feasible embodiments, the control device 330 may send the trigger signal to the power conversion device 320a, and then the controller 321a of the power conversion device 320a may inject the disturbance signal into the conversion circuit 322a. The conversion circuit 322a may invert the direct current into a disturbed alternating current based on the disturbance signal and transmit it to the AC grid. At this time, all the disturbances in the AC grid come from the power conversion device 320a that injects the disturbance signal. That is, the power conversion device 320a undertakes all the power of the disturbed alternating current.

[0102] In some feasible embodiments, the control device 330 may send a trigger signal to the power conversion device 320a and the power conversion device 320b. Then, the controller 321a of the power conversion device 320a may inject a disturbance signal into the conversion circuit 322a. The conversion circuit 322a may invert direct current into disturbed alternating current based on the disturbance signal and transmit it to the AC power grid. At the same time, the controller 321b of the power conversion device 320b may inject a disturbance signal into the conversion circuit 322b. The conversion circuit 322b may invert direct current into disturbed alternating current based on the disturbance signal and transmit it to the AC power grid. At this time, the disturbance in the AC power grid comes from the power conversion device 320a and the power conversion device 320b that inject the disturbance signal. That is, the power conversion device 320a and the power conversion device 320b jointly bear all the power of the disturbed alternating current. It can be seen that, compared with only controlling the power conversion device 320a to inject the disturbance signal, the control device controls the power conversion device 320a and the power conversion device 320b to jointly inject the disturbance signal, which can make the power of the disturbed alternating current output by the power conversion device 320a and the power conversion device 320b smaller respectively, and avoid affecting the normal operation of the power conversion device 320a and the power conversion device 320b.

[0103] In some feasible embodiments, the control device may apply the disturbance signal to the current reference value of the current control loop of the power conversion device, or to the power reference value of the power control loop, or directly to the modulation voltage of the power conversion device, so as to inject the disturbance signal into the power conversion device. It can be understood that the specific implementation manner of the control device for controlling the injection of the disturbance signal of the power conversion device can be adjusted according to the requirements of the actual application scenario, and the embodiments of the present application do not limit this.

[0104] It should be noted that, as can be seen from the above content, in order to identify the grid parameters, the control device may first output disturbed alternating current to the AC power grid through the power conversion device, so as to cause disturbance in the AC power grid. In this regard, in a conventional power supply system, the disturbance signal injected into the power conversion device is usually a high-frequency signal with a specific frequency. When the control device controls the injection of the disturbance signals of multiple power conversion devices, since the disturbance signals injected by the multiple power conversion devices are all high-frequency signals with the same frequency, the disturbances generated between the multiple disturbed alternating currents output by the multiple power conversion devices based on the disturbance signals with the same frequency will produce a cancellation effect. At this time, after the multiple disturbed alternating currents output by the multiple power conversion devices are transmitted to the AC power grid, due to the cancellation effect, the AC power grid will not generate obvious disturbance, and the control device cannot identify the grid parameters, resulting in poor applicability.

[0105] Compared with the above-mentioned conventional power supply system, in the power supply system 300 provided by the embodiments of the present application, the disturbance signal injected into the power conversion device is a Gaussian white noise signal or a pseudo-random binary sequence signal. It should be noted that, as random signals, Gaussian white noise signals or pseudo-random binary sequence signals do not have specific frequencies. Therefore, when the control device controls multiple power conversion devices to inject Gaussian white noise signals or pseudo-random binary sequence signals, the multiple disturbance alternating currents obtained by the direct current inversion conversion based on the Gaussian white noise signals or pseudo-random binary sequence signals by the multiple power conversion devices will not produce a cancellation effect due to the same frequency. Thus, mutual interference between the multiple disturbance alternating currents output by the multiple power conversion devices can be avoided, and further, obvious disturbances will not occur in the AC power grid, so that the control device can identify the grid parameters.

[0106] It should be noted that, in the above-mentioned conventional power supply system, the disturbance signal injected by the control device to control the power conversion device is a specific high-frequency signal. Then, the disturbance alternating current output by the power conversion device to the AC power grid does not have broadband characteristics. The control device can only obtain the grid parameters of the entire frequency band of the AC power grid by changing the frequency of the disturbance signal injected by the power conversion device during multiple grid parameter identification processes. Thus, it can be seen that in the conventional power supply system, the test period required for the control device to identify the grid parameters in different frequency bands of the AC power grid is long.

[0107] In contrast, in the above-mentioned power supply system (power supply system 300 or power supply system 200), when the control device controls the power conversion device to inject a Gaussian white noise signal or a pseudo-random binary sequence signal, since the Gaussian white noise signal or the pseudo-random binary sequence signal is a random signal and has a relatively wide frequency spectrum, therefore, the disturbance alternating current output by the power conversion device to the AC power grid has broadband characteristics. Further, at this time, the grid parameters identified by the control device also have broadband characteristics. Thus, it can be seen that in the power supply system, the test period required for the control device to identify the grid parameters in different frequency bands of the AC power grid is short, which can avoid injecting disturbances into the AC power grid multiple times and for a long time, and reduce the impact on the stable operation of the AC power grid.

[0108] In some feasible embodiments, as can be seen from the above content, in order to identify the grid parameters, the control device can first output disturbance alternating current to the AC power grid through the power conversion device. It can be understood that the input of the disturbance alternating current will generate interference in the AC power grid. When the interference of the disturbance alternating current is too large, it will also cause an impact on the AC power grid and affect the stable operation of the AC power grid. Therefore, in order to avoid the impact on the AC power grid caused by the output of the disturbance alternating current to the AC power grid, the control device in the embodiments of the present application can reduce the energy of the injected disturbance alternating current.

[0109] In some feasible embodiments, in the power supply system (power supply system 300 or power supply system 200), when the control device controls the disturbance signal injected by the power conversion device to be a Gaussian white noise signal, further, the expected value of the Gaussian white noise signal is equal to 0, and the variance is equal to 0.001. It should be noted that when the expected value of the Gaussian white noise signal is equal to 0 and the variance is equal to 0.001, the energy of the Gaussian white noise signal is small, so the interference of the disturbance alternating current output by the control device controlling the power conversion device based on this disturbance signal is also relatively small, and thus it will not impact the AC power grid. It can ensure the stable operation of the AC power grid while injecting the disturbance alternating current into the AC power grid.

[0110] In some feasible embodiments, when the power conversion device in the embodiment of the present application outputs disturbance alternating current to the AC power grid through the point of common coupling, since the disturbance signal injected by the power conversion device is a Gaussian white noise signal or a pseudo-random binary sequence signal with small energy, the disturbance of the disturbance alternating current to the AC power parameters at the above-mentioned point of common coupling is also relatively small. Specifically, in the case of injecting the disturbance signal of the power conversion device, the AC power parameters at the point of common coupling are less than or equal to the first disturbance threshold. Among them, the above-mentioned AC power parameters at the point of common coupling may include the voltage harmonic fluctuation amplitude, the current harmonic fluctuation amplitude, or the power fluctuation amplitude.

[0111] In some feasible embodiments, when the AC power parameter at the above-mentioned point of common coupling is the voltage harmonic fluctuation amplitude, this voltage harmonic fluctuation amplitude can be understood as the total harmonic distortion (THD) of the voltage signal at the point of common coupling, that is, the ratio of the root mean square value of the harmonic content in the voltage signal at the point of common coupling to the root mean square value of its fundamental component. It can be understood that the larger the THD of the voltage signal at the point of common coupling, the greater the interference of the voltage signal, and the greater the interference to the AC power grid. In the embodiment of the present application, the THD of the voltage signal at the point of common coupling is less than or equal to the first disturbance threshold. That is to say, in the embodiment of the present application, the control device can reduce the THD of the voltage signal at the point of common coupling and thus reduce the interference to the AC power grid by controlling the disturbance signal of the power conversion device to be a Gaussian white noise signal or a pseudo-random binary sequence signal with small energy. Among them, the above-mentioned first disturbance threshold can be understood as the maximum value of the THD of the voltage signal at the point of common coupling when the disturbance alternating current output by the power conversion device to the AC power grid does not affect the stable operation of the AC power grid.

[0112] Generally speaking, in the embodiment of the present application, the control device can make the THD of the voltage signal at the point of common coupling less than or equal to the first disturbance threshold by controlling the disturbance signal injected by the power conversion device to be a Gaussian white noise signal or a pseudo-random binary sequence signal, and thus will not impact the AC power grid when outputting the disturbance alternating current to the AC power grid.

[0113] In some feasible embodiments, the above first perturbation threshold is 2%, that is, when a perturbation signal is injected into the power conversion device and the THD of the voltage signal at the grid connection point is less than or equal to 2%, the perturbed alternating current output by the power conversion device will not affect the stable operation of the AC power grid.

[0114] In some feasible embodiments, when the AC parameter at the above grid connection point is the amplitude of current harmonic fluctuation, this amplitude of current harmonic fluctuation can be understood as the total harmonic distortion (THD) of the current signal at the grid connection point, that is, the ratio of the root mean square value of the harmonic content in the current signal at the grid connection point to the root mean square value of its fundamental wave component. It can be understood that the larger the THD of the current signal at the grid connection point, the greater the interference represented by the current signal, and the greater the interference caused to the AC power grid. In the embodiments of the present application, the THD of the current signal at the grid connection point is less than or equal to the first perturbation threshold. That is to say, in the embodiments of the present application, the control device can reduce the THD of the current signal at the grid connection point and further reduce the interference to the AC power grid by controlling the perturbation signal of the power conversion device to be a Gaussian white noise signal or a pseudo-random binary sequence signal with relatively small energy. Among them, the above first perturbation threshold can be understood as the maximum value of the THD of the current signal at the grid connection point when the perturbed alternating current output by the power conversion device to the AC power grid does not affect the stable operation of the AC power grid.

[0115] Generally speaking, in the embodiments of the present application, the control device can make the THD of the current signal at the grid connection point less than or equal to the first perturbation threshold by controlling the perturbation signal injected by the power conversion device to be a Gaussian white noise signal or a pseudo-random binary sequence signal, so as to avoid impacting the AC power grid when the perturbed alternating current is output to the AC power grid.

[0116] In some feasible embodiments, the above first perturbation threshold is 2%, that is, when a perturbation signal is injected into the power conversion device and the THD of the current signal at the grid connection point is less than or equal to 2%, the perturbed alternating current output by the power conversion device will not affect the stable operation of the AC power grid.

[0117] In some feasible embodiments, when a perturbation signal is injected into the power conversion device, the THD of the voltage signal and the THD of the current signal at the above grid connection point are both less than or equal to the first perturbation threshold, that is, the THD of the voltage signal at the grid connection point is less than or equal to 2%, and at the same time, the THD of the voltage signal at the grid connection point is less than or equal to 2%. At this time, the perturbed alternating current output by the power conversion device will not affect the stable operation of the AC power grid.

[0118] In some feasible embodiments, when the AC parameters at the above grid connection point are the power fluctuation amplitude, this power fluctuation amplitude can be understood as the fluctuation amplitude of the power parameters at the grid connection point, that is, the ratio of the change value of the power parameters at the grid connection point to the basic value of the power parameters. It can be understood that the larger the power fluctuation amplitude at the grid connection point, the greater the fluctuation of the power parameters, and the greater the interference caused to the AC power grid. In the embodiments of the present application, the power fluctuation amplitude at the grid connection point is less than or equal to the first disturbance threshold. That is to say, in the embodiments of the present application, the control device can reduce the power parameter fluctuation amplitude at the grid connection point and thus reduce the interference to the AC power grid by controlling the disturbance signal of the power conversion device to be a Gaussian white noise signal with small energy or a pseudo-random binary sequence signal. Among them, the above first disturbance threshold can be understood as the maximum value of the power parameter fluctuation amplitude at the grid connection point when the disturbance alternating current output by the power conversion device to the AC power grid does not affect the stable operation of the AC power grid.

[0119] Generally speaking, in the embodiments of the present application, the control device can make the power parameter fluctuation amplitude at the grid connection point less than or equal to the first disturbance threshold by controlling the disturbance signal injected by the power conversion device to be a Gaussian white noise signal or a pseudo-random binary sequence signal, so as not to cause an impact on the AC power grid when the disturbance alternating current is output to the AC power grid.

[0120] In some feasible embodiments, the above first disturbance threshold is 5%. That is, when the disturbance signal is injected into the power conversion device, if the power parameter fluctuation amplitude at the grid connection point is less than or equal to 5%, the disturbance alternating current output by the power conversion device will not affect the stable operation of the AC power grid.

[0121] In some feasible embodiments, the power parameters at the above grid connection point may include active power parameters and reactive power parameters. Then, when the disturbance signal is injected into the power conversion device, the active power fluctuation amplitude at the above grid connection point is less than or equal to 5%, and the reactive power fluctuation amplitude at the above grid connection point is also less than or equal to 5%. At this time, the disturbance alternating current output by the power conversion device will not affect the stable operation of the AC power grid.

[0122] In some feasible embodiments, it can be seen from the above that when the power conversion device outputs disturbance alternating current to the AC power grid, this disturbance alternating current will cause disturbance to the AC power grid, and thus will also cause disturbance to the voltage signal and current signal at the above grid connection point. It can be understood that at this time, the disturbance generated by the voltage signal and current signal at the grid connection point is related to the grid parameters of the AC power grid. Therefore, when the disturbance signal is injected into the power conversion device, the control device can collect the voltage signal and current signal at the grid connection point to identify the grid parameters of the AC power grid.

[0123] Specifically, after the power supply system provided by the embodiments of the present application controls the injection of disturbance signals of one or more power conversion devices through a control device, converts direct current into alternating current based on the injected disturbance signals, and outputs the alternating current to the AC grid through the point of common coupling, the control device can collect the voltage signal and current signal at the above-mentioned point of common coupling to obtain a first voltage signal and a first current signal. It can be understood that the first voltage signal can be understood as the voltage signal at the point of common coupling when the power conversion device outputs disturbance alternating current to the AC grid. The first current signal can be understood as the current signal at the point of common coupling when the power conversion device outputs disturbance alternating current to the AC grid. Further, the control device can identify the grid parameters of the AC grid based on the collected first voltage signal and first current signal.

[0124] In some feasible embodiments, the above grid parameters can be grid impedance, that is, the control device can identify the grid impedance of the AC grid based on the collected first voltage signal and first current signal. Further, after the control device identifies the grid impedance of the AC grid, it can control the power conversion device to adjust the alternating current output to the AC grid based on the grid impedance to enable the stable operation of the AC grid.

[0125] Exemplarily, after the control device identifies the grid impedance of the AC grid, it can obtain the power frequency impedance of the AC grid, which can be understood as the grid impedance of the AC grid at the operating frequency. Further, the control strategy of the power conversion device can be adjusted according to the power frequency impedance and a preset impedance threshold. Specifically, when the power frequency impedance of the AC grid is less than or equal to the preset impedance threshold, it indicates that the grid strength of the AC grid is strong at this time, and the control device can adjust the control strategy of the power conversion device to a grid-following control mode, and then can control the power conversion device to adjust the alternating current output to the AC grid, so that the AC grid can maintain a sufficient stability margin.

[0126] Or, when the power frequency impedance of the AC grid is greater than the preset impedance threshold, it indicates that the grid strength of the AC grid is weak at this time, and the control device can adjust the control strategy of the power conversion device to a grid-forming control mode, and then can control the power conversion device to adjust the alternating current output to the AC grid to enable the stable operation of the AC grid. Further, when the control strategy of the power conversion device is adjusted to the grid-forming control mode, when the control device identifies again that the power frequency impedance of the AC grid is greater than the power frequency impedance obtained in the previous identification, it indicates that the grid strength of the AC grid changes from strong to weak. At this time, the control device can adjust the phase-locked loop bandwidth of the power conversion device to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted phase-locked loop bandwidth, so as to strengthen the grid strength of the AC grid and maintain stable operation.

[0127] Alternatively, the control strategy of the above power conversion device may further include: the control device adjusts the current loop control parameters of the power conversion device based on the identified grid impedance, and then adjusts the alternating current output by the power conversion device to the AC grid, so that the AC grid operates stably. It can be understood that the above control strategies regarding the grid parameter being the grid impedance are all examples. The control device can also control the power conversion device according to the requirements of the actual application scenario by using other control strategies, which are not exemplified one by one in the embodiments of the present application.

[0128] In some feasible embodiments, the above grid parameter may also be a grid inertia parameter, that is, the control device can identify the grid inertia parameter of the AC grid based on the collected first voltage signal and first current signal. Further, after the control device identifies the grid inertia parameter of the AC grid, it can control the power conversion device to adjust the alternating current output to the AC grid based on the grid inertia parameter, so as to make the AC grid operate stably.

[0129] Exemplarily, after the control device identifies the grid inertia parameter of the AC grid, it can adjust the control strategy of the power conversion device according to the grid inertia parameter and a preset inertia threshold. The preset inertia threshold can be understood as the maximum value when the grid inertia of the AC grid is insufficient. Then when the grid inertia parameter of the AC grid is less than or equal to the inertia threshold, it indicates that the grid inertia of the AC grid is insufficient. Therefore, in the embodiments of the present application, when the control device identifies that the grid inertia parameter of the AC grid at the current moment is less than or equal to the preset inertia threshold, the control device can adjust the control strategy of the power conversion device based on the grid inertia parameter, control the power conversion device to adjust the alternating current output to the AC grid, and thus can improve the grid inertia and frequency support ability of the AC grid.

[0130] In some feasible embodiments, the above grid parameter may also be a grid damping parameter, that is, the control device can identify the grid damping parameter of the AC grid based on the collected first voltage signal and first current signal. Further, after the control device identifies the grid damping parameter of the AC grid, it can control the power conversion device to adjust the alternating current output to the AC grid based on the grid damping parameter, so as to make the AC grid operate stably.

[0131] Exemplarily, after identifying the grid damping parameter of the AC grid, the control device can adjust the control strategy of the power conversion device according to the grid damping parameter and the preset damping threshold range. When the grid damping parameter of the AC grid is greater than or less than the damping threshold range, in the embodiments of the present application, the control device can adjust the control strategy of the power conversion device based on the grid damping parameter, control the power conversion device to adjust the alternating current output to the AC grid, and then the grid damping parameter of the AC grid can be adjusted to the above-mentioned preset damping threshold range, so that the AC grid operates stably.

[0132] Alternatively, the control strategy of the above power conversion device may further include: the control device adjusts the control mode of the power conversion device based on the identified grid damping parameter. Specifically, the control mode of the power conversion device can be adjusted to a grid-following control mode or a grid-forming control mode. Further, the alternating current output by the power conversion device to the AC grid can be adjusted to make the AC grid operate stably. It can be understood that the above control strategies regarding the grid parameter as the grid damping parameter are all examples, and the control device can also control the power conversion device using other control strategies according to the requirements of the actual application scenario, and the embodiments of the present application do not list them one by one here.

[0133] Alternatively, the control strategy of the above power conversion device may further include: the control device adjusts the current loop control parameter of the power conversion device based on the identified grid damping parameter, and then adjusts the alternating current output by the power conversion device to the AC grid to make the AC grid operate stably. It can be understood that the above control strategies regarding the grid parameter as the grid damping parameter are all examples, and the control device can also control the power conversion device using other control strategies according to the requirements of the actual application scenario, and the embodiments of the present application do not list them one by one here.

[0134] It should be noted that the damping threshold range, inertia threshold, impedance threshold, etc. predicted by the control device above can be adjusted according to the requirements of the actual service scenario, and the embodiments of the present application do not limit this. In addition, the control device can simultaneously identify the grid impedance, grid inertia parameter, and grid damping parameter of the AC grid based on the first voltage signal and the first current signal, or other types of grid parameters, and the embodiments of the present application do not list them one by one here.

[0135] Generally speaking, after the control device in the embodiment of the present application collects the above first voltage signal and first current signal, it can identify grid parameters such as the grid impedance, grid inertia parameter, and grid damping parameter of the AC grid based on the first voltage signal and the first current signal. Further, the control device can adjust the control strategy of the power conversion device based on the above grid parameters, and then can control the power conversion device to adjust the alternating current output to the AC grid. It can be understood that while the control device adjusts the control strategy of the power conversion device, since the alternating current output by the power conversion device to the AC grid has been adjusted, the virtual impedance, virtual inertia parameter, and virtual damping parameter of the power supply system have also been adjusted. Among them, the virtual impedance of the power supply system can be understood as the impedance shown by the power supply system relative to the AC grid when it is incorporated into the AC grid. Similarly, the virtual inertia parameter of the power supply system can be understood as the inertia parameter shown by the power supply system relative to the AC grid when it is incorporated into the AC grid. The virtual damping parameter of the power supply system can be understood as the damping parameter shown by the power supply system relative to the AC grid when it is incorporated into the AC grid.

[0136] It can be seen that when the grid parameters of the AC grid change, the control device can control the power conversion device to adjust the alternating current output to the AC grid by adjusting the control strategy of the power conversion device, and then can adjust the virtual parameters of the power supply system (that is, the above virtual impedance, virtual inertia parameter, or virtual damping parameter). Further, after the power supply system with adjusted virtual parameters is incorporated into the AC grid, it can play a role in adjusting the grid parameters of the AC grid, and then can make the AC grid operate stably.

[0137] To facilitate understanding of the adjustment process of the power supply system provided in the embodiment of the present application, the present application will be briefly described in the following content in combination with Figure 4a Appendix Figure 4b Appendix Figure 5a Appendix Figure 5b and Appendix Figure 4a Appendix Figure 4b Appendix Figure 5a Appendix Figure 5b . Figure 4a FIG. Figure 4b is a schematic diagram of a grid impedance of the AC grid provided in the embodiment of the present application, Figure 5a FIG. Figure 5b is a schematic diagram of a power fluctuation of a conventional power supply system,

[0138] As shown in Figure 4aAs shown, in the embodiment of the present application, the control device identifies the grid impedance of the AC grid at the 5th second. Compared with the grid impedance identified last time, there is a significant decrease and fluctuation, which indicates that the operating state of the AC grid has changed. Further, the control device can control the power conversion device to adjust the alternating current output to the AC grid based on the grid impedance of the AC grid identified at the 5th second. Then, at the 5.7th second, the virtual inertia parameter of the power supply system is reduced (such as Figure 4b as shown). It can be understood that after the above adjustment, Figure 4a the grid impedance of the AC grid and the virtual inertia parameter of the power supply system as shown are both stable. That is to say, in the embodiment of the present application, the control device adjusts the control strategy of the power conversion device through the identified grid impedance, thereby controlling the power conversion device to adjust the alternating current output to the AC grid, which can make both the AC grid and the power supply system operate stably.

[0139] For example, Figure 5a as shown, in a conventional power supply system, the control device can guide the active power of the AC grid through the active power command and guide the reactive power of the AC grid through the reactive power command. However, starting from the 5th second as shown in Figure 5a the active power and reactive power of the AC grid have fluctuated greatly, and the adjustment effect of the active power command and the reactive power command is not significant. In contrast, as shown in Figure 5b in the power supply system provided in the embodiment of the present application, starting from the 5th second, the active power and reactive power of the AC grid also have fluctuated greatly. However, the power supply system in the embodiment of the present application can be adjusted through the control device, and then can be readjusted to a stable state after the active power and reactive power of the AC grid fluctuate (from the 8th second to the 10th second as shown in Figure 5b ). That is to say, the power supply system provided in the embodiment of the present application can ensure the stable operation of the AC grid after being incorporated into the AC grid through the power conversion device.

[0140] In the embodiment of the present application, when the operating state of the AC power grid changes, the control device in the power supply system triggers the injection of a disturbance signal into the power conversion device, so that the power conversion device converts the direct current provided by the DC power supply into a disturbed alternating current based on the disturbance signal and outputs it to the AC power grid through the grid connection point. When the disturbance signal is injected, the AC parameters at the grid connection point are less than or equal to the first disturbance threshold, that is, the disturbance of the disturbed alternating current output by the power conversion device to the AC power grid is relatively small and will not cause an impact on the AC power grid. Further, the control device can collect the first voltage signal and the first current signal at the grid connection point when the disturbance signal is injected, and identify the grid parameters of the AC power grid according to the first voltage signal and the first current signal. The control device can control the power conversion device to adjust the alternating current output to the AC power grid based on the identified grid parameters of the AC power grid, so that the AC power grid operates stably. At the same time, the control device can adjust the control strategy of the power conversion device based on the identified grid parameters of the AC power grid, so as to adaptively adjust the control strategy of the power conversion device when the AC power grid is in different working conditions, ensure that the AC power grid can operate stably under different working conditions, with high power supply stability, flexible operation and strong applicability.

[0141] Please refer to Figure 6 , Figure 6 which is a schematic flow chart of the control method for the power supply system provided by the present application. The control method for the power supply system provided by the embodiment of the present application is applicable to Figure 3 , Figure 4a and Figure 4b the power supply systems shown. It should be noted that the control method for the power supply system provided by the present application can also be understood as the control strategy of the power conversion device. Specifically, the control method for the power supply system may include the steps of:

[0142] S101. Control the injection of the disturbance signal of the power conversion device.

[0143] It should be noted that the control method provided by the embodiment of the present application can accurately adjust the AC power grid when the grid parameters of the AC power grid change. Therefore, in order to ensure the stable operation of the AC power grid under different working conditions, the control device can detect whether the operating state of the AC power grid has changed, and then adjust the control strategy of the power conversion device 220 when the operating state of the AC power grid changes.

[0144] In some feasible embodiments, the control device may determine whether the operating state of the AC power grid has changed based on the comparison result between the predicted parameters of the AC power grid and the actually collected operating parameters of the AC circuit. Alternatively, after the power supply system and the AC power grid start operating, the control device may periodically generate a trigger signal, trigger the identification of the grid parameters of the AC power grid based on the trigger signal, and determine whether the operating state of the AC power grid has changed according to the identified grid parameters. Further, when the operating state of the AC power grid changes, in order to enable the control device to adjust the control strategy of the power conversion device based on the grid parameters of the AC power grid, the control device may obtain the trigger signal for identifying the grid parameters to trigger the identification of the grid parameters of the AC power grid.

[0145] In some feasible embodiments, after obtaining the trigger signal for identifying the grid parameters, the control device may control the injection of the disturbance signal of the power conversion device based on the trigger signal. The power conversion device may output a disturbed alternating current to the AC power grid based on the disturbance signal. It can be understood that in the case of injecting the disturbance signal, the AC parameters at the grid connection point are less than or equal to the first disturbance threshold, and the AC parameters include at least one of the voltage harmonic fluctuation amplitude, the current harmonic fluctuation amplitude, or the power fluctuation amplitude. It can be understood that the AC parameters at the grid connection point being less than or equal to the first disturbance threshold indicates that the interference of the disturbed alternating current output by the power conversion device is small, and thus will not cause an impact on the AC power grid. The specific implementation manner of the above S101 may refer to the implementation manner executed by the control device in the above Figure 2 and Figure 3 and will not be elaborated herein in the embodiments of the present application.

[0146] S102. After controlling the injection of the disturbance signal of the power conversion device, collect the first voltage signal and the first current signal at the grid connection point, and control the power conversion device to adjust the alternating current output to the AC power grid based on the first voltage signal and the first current signal.

[0147] In some feasible embodiments, when the power conversion device outputs a disturbed alternating current to the AC power grid, the disturbed alternating current will cause a disturbance to the AC power grid, and thus will also cause a disturbance to the voltage signal and the current signal at the above grid connection point. It can be understood that at this time, the disturbance generated by the voltage signal and the current signal at the grid connection point is related to the grid parameters of the AC power grid. Therefore, in the case of injecting the disturbance signal into the power conversion device, the control device may collect the voltage signal and the current signal at the grid connection point to identify the grid parameters of the AC power grid.

[0148] It can be seen that in the case of injecting a disturbance signal, the control method provided by the embodiments of the present application can collect the first voltage signal and the first current signal at the grid connection point through the control device, and identify the grid parameters of the AC power grid based on the first voltage signal and the first current signal.

[0149] In some feasible implementation manners, the control method provided by the embodiments of the present application can control the power conversion device by using different control strategies for the AC power grid under different working conditions. That is, for the AC power grid under different working conditions, the control strategy for the control device to control the power conversion device in the embodiments of the present application can be adaptively adjusted. Specifically, the control device can adjust the control strategy of the power conversion device based on the identified grid parameters of the AC power grid, so as to adaptively adjust the control of the output of the power conversion device when the AC power grid is in different working conditions, ensure that the AC power grid can operate stably under different working conditions, have high power supply stability, flexible operation, and strong applicability.

[0150] For the specific implementation manner of the above S102, reference can be made to the implementation manner executed by the control device in the above Figure 2 and Figure 3 The embodiments of the present application will not be elaborated herein.

[0151] In an alternative implementation manner, the grid parameter is the grid impedance. Based on the grid parameters of the AC power grid, controlling the power conversion device to adjust the alternating current output to the AC power grid includes: based on the grid impedance of the AC power grid, adjusting the phase-locked loop bandwidth of the power conversion device to control the power conversion device to adjust the alternating current output to the AC power grid based on the adjusted phase-locked loop bandwidth.

[0152] It can be understood that the control device can collect the first voltage signal and the first current signal at the grid connection point in the case of injecting a disturbance signal, and identify the grid impedance of the AC power grid according to the first voltage signal and the first current signal. The control device can adjust the phase-locked loop bandwidth of the power conversion device based on the grid impedance to control the power conversion device to adjust the alternating current output to the AC power grid based on the adjusted phase-locked loop bandwidth, thereby ensuring the stability margin of the AC power grid.

[0153] In another alternative implementation manner, the grid parameter is the grid inertia parameter. Based on the grid parameters of the AC power grid, controlling the power conversion device to adjust the alternating current output to the AC power grid includes: the control device is further configured to adjust the inertia time constant of the power conversion device based on the grid inertia parameter of the AC power grid to control the power conversion device to adjust the alternating current output to the AC power grid based on the adjusted inertia time constant.

[0154] It can be understood that the control device can collect the first voltage signal and the first current signal at the grid connection point under the condition of disturbance signal injection, and identify the grid inertia parameter of the AC grid according to the first voltage signal and the first current signal. The control device can adjust the inertia time constant of the power conversion device based on the grid inertia parameter, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted inertia time constant, and thus can improve the frequency support ability of the power conversion device.

[0155] In another alternative embodiment, the grid parameter is the grid damping parameter. Based on the grid parameter of the AC grid, controlling the power conversion device to adjust the alternating current output to the AC grid includes: adjusting the virtual impedance parameter of the power conversion device based on the grid damping parameter of the AC grid, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted virtual impedance parameter.

[0156] It can be understood that the control device can collect the first voltage signal and the first current signal at the grid connection point under the condition of disturbance signal injection, and identify the grid damping parameter of the AC grid according to the first voltage signal and the first current signal. The control device can adjust the virtual impedance parameter of the power conversion device based on the grid damping parameter, so as to control the power conversion device to adjust the alternating current output to the AC grid based on the adjusted inertia time constant, and thus can ensure the stable operation of the AC grid.

[0157] In another alternative embodiment, when the power conversion device outputs alternating current to the AC grid, based on the operating parameter and the prediction parameter of the AC grid, a trigger signal for identifying the grid parameter is obtained, and when the trigger signal for identifying the grid parameter is obtained, the disturbance signal injection of the power conversion device is controlled.

[0158] It can be understood that after the control device obtains the prediction parameter of the AC grid, it can collect the operating parameter of the AC grid, and judge whether the operating state of the AC grid has changed according to the comparison result of the prediction parameter and the operating parameter of the AC grid. When the operating state of the AC grid changes, the control device can obtain a trigger signal for identifying the grid parameter, which can improve the detection timeliness of the operating state of the AC grid and perform an active response, with a more timely response and stronger applicability.

[0159] In another alternative embodiment, when a preset measurement time period arrives, a trigger signal for identifying the grid parameter is obtained, and when the trigger signal for identifying the grid parameter is obtained, the disturbance signal injection of the power conversion device is controlled.

[0160] It can be understood that the control device can identify the power grid parameters regularly according to a preset measurement time period, so as to adjust the control method of the power conversion device according to the identified power grid parameters, and ensure the stable operation of the AC power grid under different working conditions.

[0161] In another optional implementation manner, when obtaining a trigger signal for identifying power grid parameters, controlling the injection of a disturbance signal of the power conversion device includes: when obtaining a trigger signal for identifying power grid parameters, generating a disturbance signal of the power conversion device and injecting the disturbance signal into the power conversion device to control the injection of the disturbance signal of the power conversion device.

[0162] In another optional implementation manner, the power conversion device includes a controller and a conversion circuit. When obtaining a trigger signal for identifying power grid parameters, controlling the injection of a disturbance signal of the power conversion device includes: when obtaining a trigger signal for identifying power grid parameters, triggering the controller to generate a disturbance signal of the conversion circuit and injecting the disturbance signal into the conversion circuit to control the injection of the disturbance signal of the power conversion device.

[0163] In another optional implementation manner, the power supply system includes n power conversion devices, where n is a positive integer. When obtaining a trigger signal for identifying power grid parameters, controlling the injection of a disturbance signal of the power conversion device includes: when obtaining a trigger signal for identifying power grid parameters, controlling the injection of a disturbance signal of m power conversion devices among the n power conversion devices, and the disturbance signal is used to trigger the m power conversion devices to output disturbance alternating current to the AC power grid; m is a positive integer less than n. The capacity of any one of the m power conversion devices is greater than the capacity of any one of the remaining power conversion devices other than the m power conversion devices among the n power conversion devices.

[0164] It can be understood that in the case where the power supply system includes multiple power conversion devices, the control device can avoid affecting the stable operation of other power conversion devices with smaller capacities among the multiple power conversion devices by controlling the injection of a disturbance signal of at least one power conversion device with a larger capacity among the multiple power conversion devices and outputting disturbance alternating current. In addition, by controlling multiple power conversion devices to output multiple disturbance alternating currents to the AC power grid simultaneously, the power borne by one power conversion device for outputting disturbance alternating current can be reduced, ensuring the stable operation of the power conversion device.

[0165] In another optional implementation manner, the AC parameter is the voltage harmonic fluctuation amplitude, and the first disturbance threshold is obtained from the voltage harmonic fluctuation amplitude of the first voltage signal and a preset voltage harmonic fluctuation amplitude threshold.

[0166] It can be understood that when the power conversion device outputs disturbing alternating current to the AC power grid through the grid connection point, the voltage harmonic fluctuation amplitude at the grid connection point is less than or equal to the first disturbance threshold, indicating that the disturbance of the disturbing alternating current is relatively small, and thus it will not cause an impact on the AC power grid when outputting the disturbing alternating current to the AC power grid, ensuring the stable operation of the AC power grid.

[0167] In another alternative embodiment, the AC parameter is the current harmonic fluctuation amplitude, and the first disturbance threshold is obtained from the current harmonic fluctuation amplitude of the first current signal and a preset current harmonic fluctuation amplitude threshold.

[0168] It can be understood that when the power conversion device outputs disturbing alternating current to the AC power grid through the grid connection point, the current harmonic fluctuation amplitude at the grid connection point is less than or equal to the first disturbance threshold, indicating that the disturbance of the disturbing alternating current is relatively small, and thus it will not cause an impact on the AC power grid when outputting the disturbing alternating current to the AC power grid, ensuring the stable operation of the AC power grid.

[0169] In another alternative embodiment, the first disturbance threshold is 2%.

[0170] It can be understood that when the current harmonic fluctuation amplitude and the voltage harmonic fluctuation threshold at the grid connection point are less than or equal to 2%, the disturbing alternating current will not cause an impact on the AC power grid when output to the AC power grid, ensuring the stable operation of the AC power grid.

[0171] In another alternative embodiment, the AC parameter is the power fluctuation amplitude, and the first disturbance threshold is obtained from the power fluctuation amplitudes of the first voltage signal and the first current signal, and a preset power fluctuation amplitude threshold.

[0172] It can be understood that when the power conversion device outputs disturbing alternating current to the AC power grid through the grid connection point, the power fluctuation amplitude at the grid connection point is less than or equal to the first disturbance threshold, indicating that the disturbance of the disturbing alternating current is relatively small, and thus it will not cause an impact on the AC power grid when outputting the disturbing alternating current to the AC power grid, ensuring the stable operation of the AC power grid.

[0173] In another alternative embodiment, in the thirteenth possible embodiment, the first disturbance threshold is 5%.

[0174] It can be understood that when the power fluctuation amplitude at the grid connection point is less than or equal to 5%, the disturbing alternating current will not cause an impact on the AC power grid when output to the AC power grid, ensuring the stable operation of the AC power grid.

[0175] In another alternative embodiment, the disturbance signal is any one of a Gaussian white noise signal or a pseudo-random binary sequence signal.

[0176] It can be understood that when the disturbance signals injected by multiple power conversion devices in the power supply system are Gaussian white noise signals or pseudo-random binary sequence signals, the multiple disturbed alternating currents output by the multiple power conversion devices will not produce a cancellation effect due to the same frequency, thereby avoiding interference between the multiple disturbed alternating currents output by the multiple power conversion devices.

[0177] In another alternative embodiment, the disturbance signal is a Gaussian white noise signal with an expected value equal to 0 and a variance equal to 0.001.

[0178] It can be understood that when the disturbance signal injected by the power conversion device is a Gaussian white noise signal with an expected value equal to 0 and a variance equal to 0.001, the energy of the Gaussian white noise signal is small, so the interference of the disturbed alternating current output by the control device controlling the power conversion device based on this disturbance signal is also relatively small, and thus will not cause an impact on the AC power grid, and the stable operation of the AC power grid can be ensured while the disturbed alternating current is injected into the AC power grid.

[0179] In specific implementation, more operations performed by the control device in the control method of the power supply system provided in this application can be referred to Figure 2 and Figure 3 the implementation manners performed by the control device shown, which will not be elaborated here.

[0180] In the embodiment of this application, the control device in the power supply system triggers the injection of the disturbance signal of the power conversion device when the operating state of the AC power grid changes, so that the power conversion device converts the direct current provided by the DC power supply into a disturbed alternating current based on this disturbance signal and outputs it to the AC power grid through the grid connection point. In the case of disturbance signal injection, the AC parameters at the grid connection point are less than or equal to the first disturbance threshold, that is, the disturbance of the disturbed alternating current output by the power conversion device to the AC power grid is relatively small and will not cause an impact on the AC power grid. Further, the control device can collect the first voltage signal and the first current signal at the grid connection point in the case of disturbance signal injection, and identify the grid parameters of the AC power grid according to the first voltage signal and the first current signal. The control device can control the power conversion device to adjust the alternating current output to the AC power grid based on the identified grid parameters of the AC power grid, so that the AC power grid operates stably. It can be seen that the control device can adjust the control method of the power conversion device based on the identified grid parameters of the AC power grid, so as to adaptively adjust the control method of the power conversion device when the AC power grid is in different working conditions, and ensure that the AC power grid can operate stably under different working conditions.

[0181] The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A power supply system, characterized in that, The power supply system includes a control device and at least one power conversion device. The output end of the at least one power conversion device is connected to an AC power grid at a point of common coupling. The control device is connected to the at least one power conversion device; The control device is configured to control the injection of a disturbance signal of the power conversion device. The disturbance signal is used to trigger the power conversion device to output a disturbed alternating current to the AC power grid, and when the disturbance signal is injected, the AC parameters at the point of common coupling are less than or equal to a first disturbance threshold. The AC parameters include at least one of a voltage harmonic fluctuation amplitude, a current harmonic fluctuation amplitude, or a power fluctuation amplitude; The control device is further configured to, after controlling the injection of the disturbance signal of the power conversion device, collect a first voltage signal and a first current signal at the point of common coupling, and control the power conversion device to adjust the alternating current output to the AC power grid based on the first voltage signal and the first current signal.

2. The power supply system according to claim 1, characterized in that, The AC parameter is a voltage harmonic fluctuation amplitude, and the first disturbance threshold is obtained from the voltage harmonic fluctuation amplitude of the first voltage signal and a preset voltage harmonic fluctuation amplitude threshold.

3. The power supply system according to claim 1, wherein The AC parameter is a current harmonic fluctuation amplitude, and the first disturbance threshold is obtained from the current harmonic fluctuation amplitude of the first current signal and a preset current harmonic fluctuation amplitude threshold.

4. The power supply system according to claim 1, wherein The AC parameter is a power fluctuation amplitude, and the first disturbance threshold is obtained from the power fluctuation amplitudes of the first voltage signal and the first current signal, and a preset power fluctuation amplitude threshold.

5. The power supply system according to any one of claims 1-4, characterized in that, The disturbance signal is any one of a Gaussian white noise signal or a pseudo-random binary sequence signal.

6. The power supply system according to any one of claims 1-5, characterized in that, The control device is further configured to, when the power conversion device outputs alternating current to the AC power grid, obtain a trigger signal for identifying grid parameters based on the operating parameters and prediction parameters of the AC power grid; The control device is further configured to, when obtaining the trigger signal for identifying grid parameters, control the injection of the disturbance signal of the power conversion device.

7. The power supply system according to any one of claims 1-5, characterized in that, The control device is further configured to obtain a trigger signal for identifying grid parameters when a preset measurement time period arrives; The control device is further configured to, when obtaining the trigger signal for identifying grid parameters, control the injection of the disturbance signal of the power conversion device.

8. The power supply system according to claim 6 or 7, characterized in that, The control device is further configured to, when obtaining the trigger signal for identifying grid parameters, generate a disturbance signal of the power conversion device and inject the disturbance signal into the power conversion device to control the injection of the disturbance signal of the power conversion device.

9. The power supply system according to claim 6 or 7, characterized in that, The power conversion device includes a controller and a conversion circuit; The control device is further configured to, when obtaining the trigger signal for identifying grid parameters, trigger the controller to generate a disturbance signal of the conversion circuit and inject the disturbance signal into the conversion circuit to control the injection of the disturbance signal of the power conversion device.

10. The power supply system according to claim 6 or 7, characterized in that, The power supply system includes n power conversion devices, where n is a positive integer; The control device is further configured to control the injection of disturbance signals of m power conversion devices among the n power conversion devices when a trigger signal for identifying grid parameters is obtained, where the disturbance signals are used to trigger the m power conversion devices to output disturbed alternating current to the AC grid; m is a positive integer less than n; The capacity of any one of the m power conversion devices is greater than the capacity of any one of the remaining power conversion devices among the n power conversion devices other than the m power conversion devices.

11. A control method for a power supply system, characterized in that, The power supply system includes at least one power conversion device, and an output end of the at least one power conversion device is connected to the AC grid at a grid connection point. The method includes: Controlling the injection of disturbance signals of the power conversion device, where the disturbance signals are used to trigger the power conversion device to output disturbed alternating current to the AC grid, and in the case of the injection of the disturbance signals, the alternating current parameters at the grid connection point are less than or equal to a first disturbance threshold, and the alternating current parameters include at least one of a voltage harmonic fluctuation amplitude, a current harmonic fluctuation amplitude, or a power fluctuation amplitude; After controlling the injection of the disturbance signals of the power conversion device, collecting a first voltage signal and a first current signal at the grid connection point, and controlling the power conversion device to adjust the alternating current output to the AC grid based on the first voltage signal and the first current signal.

12. The control method according to claim 11, characterized in that, The alternating current parameter is a voltage harmonic fluctuation amplitude, and the first disturbance threshold is obtained from the voltage harmonic fluctuation amplitude of the first voltage signal and a preset voltage harmonic fluctuation amplitude threshold.

13. The control method according to claim 11, characterized in that, The alternating current parameter is a current harmonic fluctuation amplitude, and the first disturbance threshold is obtained from the current harmonic fluctuation amplitude of the first current signal and a preset current harmonic fluctuation amplitude threshold.

14. The control method according to claim 11, wherein The alternating current parameter is a power fluctuation amplitude, and the first disturbance threshold is obtained from the power fluctuation amplitudes of the first voltage signal and the first current signal, and a preset power fluctuation amplitude threshold.

15. The control method according to claim 11, wherein The disturbance signal is any one of a Gaussian white noise signal or a pseudo-random binary sequence signal.

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