Photovoltaic power generation system network construction control method

Abstract

The invention discloses a grid construction control method for a photovoltaic power generation system. The control method comprises the following steps: calculating a first virtual inertia when the frequency of a power grid is reduced and a second virtual inertia when the frequency of the power grid is increased based on characteristic parameters of the photovoltaic power generation system; selecting the first virtual inertia or the second virtual inertia as a value of the virtual inertia of the current photovoltaic power generation system; based on the characteristic parameters of the photovoltaic power generation system and the value of the virtual inertia of the current photovoltaic power generation system, respectively obtaining a reference voltage phase angle and a reference voltage amplitude; calculating a d-axis reference voltage and a q-axis reference voltage according to the reference voltage phase angle and the reference voltage amplitude; a modulation signal Ed is obtained through calculation based on the d-axis reference voltage, and a modulation signal Eq is obtained through calculation based on the q-axis reference voltage; the modulation signals Ed and Eq are converted through abc / dq to generate PWM drive signals, the PWM drive signals are input to switch tubes of a photovoltaic inverter, and network construction control of the photovoltaic power generation system is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic control, and in particular to a photovoltaic power generation system network control method. Background Art

[0002] Renewable energy sources are increasingly replacing traditional thermal and hydroelectric units in the power system. Photovoltaic power generation has seen rapid growth in installed capacity in recent years, driven by mature technology and rapidly declining costs. Renewable energy sources are integrated into the grid via power electronic converters. Most existing systems employ grid-following control, which lacks inertia characteristics and exhibits extremely fast response times. This leads to significant frequency fluctuations during power conversion or line faults, exacerbating system instability in weak grid scenarios. Furthermore, renewable energy sources are highly susceptible to weather, and the output of photovoltaic power generation systems varies significantly under different environmental conditions. Traditional control methods pose significant challenges to the security and stability of the power system. To enhance the support provided by renewable energy sources for the grid, grid-building control technologies have been proposed.

[0003] Grid control technology simulates the mechanical characteristics of synchronous generators, independently of the external grid, to exhibit voltage source characteristics. This provides inertia and damping for the system, offering strong voltage support in weak grids or remote areas while also suppressing sub-supersynchronous oscillations. However, fixed-parameter or fixed-inertia designs in grid control struggle to adapt to diverse scenarios. When the grid short circuit is high, the large virtual inertia creates significant operational stress. However, when the short circuit is low, the provided inertia is insufficient to ensure reliable operation, resulting in widespread grid disconnections. The core of the grid control system is to provide virtual inertia support during sudden voltage and frequency fluctuations. This is achieved by briefly injecting large amounts of power into the grid to prevent sudden frequency dips and spikes. Photovoltaic systems are all connected to the grid through power electronics or filter capacitors and lack inherent mechanical rotational inertia. Weather also significantly impacts photovoltaic power generation. Insufficient sunlight can significantly reduce the power capacity of photovoltaic systems. Furthermore, large-scale photovoltaic systems are typically deployed in deserted areas, where temperatures can be high even when sunlight is high, significantly reducing the power capacity they can provide. When the designed virtual inertia control parameters are too large, exceeding the actual physical capacity of the photovoltaic system, the virtual inertia characteristics of the grid control will fail, and there may even be a risk of DC voltage instability.

[0004] Existing grid-based control methods fail to consider the varying limits of PV's ability to provide virtual inertia under varying environmental conditions, nor do they enable timely adjustment of key grid-based control parameters based on various environmental conditions, effectively leveraging the diverse support provided by PV systems to the grid. Furthermore, when multiple PV panels are connected to the grid, there remains a lack of solutions for designing real-time grid-based control parameters that reflect the power characteristics of PV panels at different times, taking into account the power generation capabilities of different components and environmental awareness. Furthermore, distributed control of multiple PV panels, enabling them to adjust virtual inertia in real time, leveraging local environmental conditions and power generation capabilities without the involvement of higher-level energy management systems, remains a challenge. Summary of the Invention

[0005] In view of the above-mentioned prior art, the present invention provides a photovoltaic power generation system grid control method, which mainly solves the technical problems existing in the above-mentioned background technology.

[0006] To achieve the above object, the technical solution of the present invention is implemented as follows: a photovoltaic power generation system grid control method, the control method comprising the following steps: Acquiring characteristic parameters of the photovoltaic power generation system, and calculating a first virtual inertia and a second virtual inertia based on the characteristic parameters, wherein the characteristic parameters of the photovoltaic power generation system include an open circuit voltage, a short circuit current, a fill factor, a power temperature coefficient, a total power generation efficiency, a current temperature, an irradiance, a current photovoltaic power generation system power, a DC capacitor, a DC rated voltage, a grid rated angular frequency, and a grid angular frequency; According to the direction of the grid frequency change, the first virtual inertia or the second virtual inertia is selected as the current virtual inertia of the photovoltaic power generation system; Based on the characteristic parameters of the photovoltaic power generation system and the current virtual inertia, the reference voltage phase angle and reference voltage amplitude are obtained respectively; The three-phase voltage of the inverter is synthesized according to the reference voltage phase angle and the reference voltage amplitude, and the d-axis reference voltage and the q-axis reference voltage are obtained through abc / dq transformation; The modulation signal Ed is calculated based on the d-axis reference voltage, and the modulation signal Eq is calculated based on the q-axis reference voltage; The modulation signals Ed and Eq are converted into PWM drive signals after abc / dq conversion, and the PWM drive signals are input into each switch tube of the photovoltaic inverter to complete the grid control of the photovoltaic power generation system.

[0007] Optionally, the first virtual inertia is calculated based on the characteristic parameters of the photovoltaic power generation system, specifically including: calculating the first virtual inertia when the grid frequency is reduced according to the open circuit voltage, short circuit current, fill factor, power temperature coefficient, total power generation efficiency of the photovoltaic power generation system, as well as the current temperature, irradiance, current photovoltaic power generation system power, DC capacitance, DC rated voltage, grid rated angular frequency, and grid angular frequency.

[0008] Optionally, the second virtual inertia is calculated based on the characteristic parameters of the photovoltaic power generation system, specifically including: calculating the second virtual inertia when the grid frequency increases based on the current photovoltaic power generation system power, DC capacitance, DC rated voltage, grid rated angular frequency, and grid angular frequency.

[0009] Optionally, based on characteristic parameters of the photovoltaic power generation system and the value of the virtual inertia of the current photovoltaic power generation system, a reference voltage phase angle and a reference voltage amplitude are obtained, specifically including: Calculating the output inverter angular frequency according to the preset active reference power, actual active power, virtual inertia of the current photovoltaic power generation system, damping coefficient, and rated angular frequency of the grid, and integrating the inverter angular frequency to obtain a reference voltage phase angle; The reference voltage amplitude is calculated based on the preset reactive reference power, actual reactive power, voltage coefficient, and grid rated voltage amplitude.

[0010] Optionally, the modulation signal Ed is obtained by calculation based on the d-axis reference voltage, specifically including: The deviation between the d-axis reference voltage and the d-axis voltage output by the inverter is calculated, and the deviation calculation result is input into the d-axis voltage controller for superposition with the q-axis capacitor cross-coupling term to output the d-axis current reference value; The deviation between the d-axis current reference value and the d-axis current output by the inverter is calculated, and the deviation calculation result is input into the d-axis current controller and superimposed with the q-axis inductance cross-coupling compensation term to generate the modulation signal Ed.

[0011] Optionally, the modulation signal Eq is obtained by calculation based on the q-axis reference voltage, specifically including: The deviation between the q-axis reference voltage and the q-axis voltage output by the inverter is calculated, and the deviation calculation result is input into the q-axis voltage controller, superimposed with the d-axis capacitance cross-coupling term, and then the d-axis current reference value is output; The deviation between the q-axis current reference value and the q-axis current output by the inverter is calculated, and the deviation calculation result is input into the q-axis current controller and superimposed with the d-axis inductance cross-coupling term to generate the modulation signal Eq.

[0012] Optionally, if the grid frequency change rate is less than 0, the first virtual inertia is selected as the current virtual inertia of the photovoltaic power generation system; if the grid frequency change rate is greater than 0, the second virtual inertia is selected as the current virtual inertia of the photovoltaic power generation system.

[0013] The beneficial effects of the present invention are as follows: by dynamically sensing the grid operating conditions and the real-time environmental conditions of the photovoltaic system, the key control parameters of the virtual inertia for grid-forming control are calculated, thereby significantly improving the active support capability of the photovoltaic power generation system for the grid: on the one hand, the virtual inertia parameters can be adaptively adjusted according to the direction of grid frequency change and the actual carrying capacity of the photovoltaic system, ensuring that the inertia support provided to the grid accurately matches the real-time demand, avoiding both voltage and frequency instability caused by insufficient virtual inertia and system instability or DC faults caused by excessive virtual inertia, thus achieving a dynamic balance between active support capability and system safety in grid-forming control; on the other hand, the control logic based on the key parameters can quickly respond to grid frequency fluctuations, enhance the grid-forming effect on frequency changes through real-time adaptive inertia output, improve the stability of the new energy supply to the grid, and significantly improve the timeliness and accuracy of grid-forming control.

[0014] At the same time, when multiple photovoltaic groups adopt this method, each photovoltaic group can independently adjust the key parameters of virtual inertia based on the local grid conditions and its own power generation capacity, without relying on the centralized coordination of the upper-level energy management system. While reducing the overall control calculation amount, it achieves the optimal configuration of network resources across the entire network through distributed collaboration, further enhancing the active support capability of the power grid in the multi-photovoltaic grid-connected scenario, and ensuring that the grid frequency can still maintain an efficient and stable dynamic balance under complex conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the flow of the photovoltaic power generation system network control method in the embodiment of the present application; Figure 2 This is a control logic block diagram in an embodiment of the present application. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further elaborated in detail below in conjunction with the drawings and specific embodiments of the specification. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In the following description, reference is made to "some embodiments", which describes a subset of all possible embodiments, but it should be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0017] In the following description, numerous specific details are provided to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without one or more of these details. In other instances, certain technical features well known in the art are not described to avoid confusion with the present invention.

[0018] It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments proposed herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. And the purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "comprising" and / or "comprising" when used in this specification determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0019] It should also be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "inner," "outer," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0020] In order to fully understand the present invention, a detailed structure will be provided in the following description to illustrate the technical solution proposed by the present invention. Optional embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other implementations.

[0021] Please refer to the attached Figure 1-Figure 2 The present application provides a photovoltaic power generation system grid control method, the control method comprising the following steps: S1. Acquire characteristic parameters of a photovoltaic power generation system, and calculate a first virtual inertia and a second virtual inertia based on the characteristic parameters of the photovoltaic power generation system; S2. Determine the direction of change of the grid frequency change rate, and select the first virtual inertia or the second virtual inertia as the value of the virtual inertia of the current photovoltaic power generation system based on the change direction; S3, based on the characteristic parameters of the photovoltaic power generation system and the value of the virtual inertia of the current photovoltaic power generation system, respectively obtain a reference voltage phase angle and a reference voltage amplitude; S4, synthesizing the inverter three-phase voltage according to the reference voltage phase angle and the reference voltage amplitude, and obtaining the d-axis reference voltage and the q-axis reference voltage through abc / dq transformation; S5. Calculate and obtain a modulation signal Ed based on the d-axis reference voltage, and calculate and obtain a modulation signal Eq based on the q-axis reference voltage; S6. The modulation signals Ed and Eq are converted into PWM drive signals after abc / dq conversion. The PWM drive signals are input to each switch tube of the photovoltaic inverter to complete the grid control of the photovoltaic power generation system.

[0022] Specifically, the photovoltaic power generation system grid control method adopted in the present application obtains the characteristic parameters of the photovoltaic power generation system, and calculates the first virtual inertia when the grid frequency decreases and the second virtual inertia when the grid frequency increases. The calculation of the first virtual inertia needs to be combined with the open-circuit voltage, short-circuit current, fill factor, power temperature coefficient, total power generation efficiency, and current temperature, irradiance, current photovoltaic power generation system power, DC capacitance, DC rated voltage, grid rated angular frequency, and grid angular frequency of the photovoltaic power generation system. The calculation of the second virtual inertia is based on the current photovoltaic power generation system power, DC capacitance, DC rated voltage, grid rated angular frequency, and grid angular frequency. Through this differentiated calculation, the provided virtual inertia can be adjusted according to the direction of grid frequency change and the real-time carrying capacity of the photovoltaic system, which effectively avoids voltage and frequency instability caused by insufficient inertia, and prevents system instability or DC faults caused by excessive inertia, solving the problem of traditional fixed virtual inertia in support The dilemma between insufficient support and excessive support is solved, which broadens the boundaries of safe and stable operation of the system. Subsequently, the direction of change of the grid frequency change rate is determined, and the corresponding virtual inertia is selected as the virtual inertia value of the current photovoltaic power generation system based on the change direction. Based on the characteristic parameters of the photovoltaic power generation system and the currently selected virtual inertia value, the reference voltage phase angle and the reference voltage amplitude are respectively determined. The three-phase voltage of the inverter is synthesized according to the reference voltage phase angle and the reference voltage amplitude, and abc / dq coordinate transformation is performed in sequence to obtain the d-axis reference voltage and the q-axis reference voltage. The modulation signal Ed is calculated based on the d-axis reference voltage, and the modulation signal Eq is calculated based on the q-axis reference voltage. The modulation signals Ed and Eq are input into the PWM modulation module after abc / dq coordinate transformation. The corresponding PWM drive signal is generated based on the modulation signal, and the PWM drive signal is input to each switch tube of the photovoltaic inverter, thereby realizing grid control of the photovoltaic power generation system. This method dynamically adjusts the virtual inertia parameters and combines coordinate transformation and PWM modulation technology. Its control logic can quickly respond to grid frequency disturbances, improve the inertia response speed and support adjustment accuracy, enhance the network control capability and grid frequency stability, enable the photovoltaic power generation system to actively participate in grid frequency and voltage support, and improve the stability and reliability of the power system.

[0023] In a further embodiment, the photovoltaic panels in the photovoltaic power generation system of the present application are connected through the line impedance X p , DC capacitor C pConnected to the DC side of the inverter, the output voltage and current of the AC side of the inverter pass through the filter inductor and filter capacitor and are connected to the AC grid through the grid connection point.

[0024] In a further embodiment, the characteristic parameters of the photovoltaic power generation system include the fill factor and fill coefficient of the photovoltaic modules, the open circuit voltage of the photovoltaic power generation system under standard test conditions STC, the short circuit current of STC, the power temperature coefficient, the total power generation efficiency, as well as the current temperature, irradiance, the current photovoltaic power generation system power, DC capacitance, DC rated voltage, and grid rated angular frequency.

[0025] In a further embodiment, the first virtual inertia is calculated based on the characteristic parameters of the photovoltaic power generation system, specifically including: calculating the first virtual inertia when the grid frequency decreases according to the open circuit voltage, short circuit current, fill factor, power temperature coefficient, and total power generation efficiency of the photovoltaic power generation system, as well as the current temperature, irradiance, current photovoltaic power generation system power, DC capacitance, DC rated voltage, grid rated angular frequency, and grid angular frequency. The specific calculation expression is:

[0026] Where FF is the fill factor of the photovoltaic module, is the STC open circuit voltage, is the STC short-circuit current, is the power temperature coefficient, At 25°C, is the current temperature, G is the surface irradiance, and the grid rated angular frequency , grid angular frequency , the current photovoltaic power generation system power , η is the total power generation efficiency of the photovoltaic system, is the DC side capacitor of the photovoltaic power generation system, It is the rated voltage of the photovoltaic power generation system.

[0027] In a further embodiment, the second virtual inertia is calculated based on the characteristic parameters of the photovoltaic power generation system, specifically including: calculating the second virtual inertia when the grid frequency increases based on the photovoltaic power generation system power, DC capacitance, DC rated voltage, grid rated angular frequency, and grid angular frequency, wherein the specific calculation expression is:

[0028] In a further embodiment, the direction of the grid frequency change is determined, and the first virtual inertia or the second virtual inertia is selected as the value of the virtual inertia of the current photovoltaic power generation system based on the change direction. Specifically, if the grid frequency change rate is less than 0, the first virtual inertia is selected as the value of the virtual inertia of the current photovoltaic power generation system; if the grid frequency change rate is greater than 0, the second virtual inertia is selected as the value of the virtual inertia of the current photovoltaic power generation system.

[0029] In a further embodiment, based on the characteristic parameters of the photovoltaic power generation system and the value of the virtual inertia of the current photovoltaic power generation system, a reference voltage phase angle and a reference voltage amplitude are obtained respectively, specifically including: According to the preset active reference power , actual active power , the value of the virtual inertia J of the current photovoltaic power generation system, the damping coefficient D, the rated angular frequency of the grid , output the inverter angular frequency ω according to the following formula, and integrate it to get the reference voltage phase angle θ. The specific calculation formula is:

[0030] According to the preset reactive reference power , actual reactive power , voltage coefficient , grid rated voltage amplitude , calculate the reference voltage amplitude , its specific calculation expression is:

[0031] In a further embodiment, according to the reference voltage phase angle θ, the reference voltage amplitude U ref The three-phase voltages Ea, Eb, and Ec of the synthesized inverter are converted into the reference voltage U by abc / dq transformation. dref , U qref , the expressions of Ea, Eb, and Ec are:

[0032] In a further embodiment, the modulation signal Ed is obtained by calculation based on the d-axis reference voltage, specifically including: The deviation between the d-axis reference voltage and the d-axis voltage output by the inverter is calculated, and the deviation calculation result is input into the d-axis voltage controller and superimposed with the q-axis capacitor cross-coupling term to output the d-axis current reference value. The q-axis capacitor cross-coupling compensation term is calculated based on the q-axis feedback voltage, grid angular frequency and filter capacitance. The deviation between the d-axis current reference value and the d-axis current output by the inverter is calculated. The deviation calculation result is input into the d-axis current controller and superimposed with the q-axis inductance cross-coupling compensation term to generate a modulation signal Ed, where the q-axis inductance cross-coupling compensation term is calculated based on the q-axis feedback current, the grid angular frequency and the filter inductance.

[0033] A further implementation method is to calculate and obtain the modulation signal Eq based on the q-axis reference voltage, specifically including: The deviation between the q-axis reference voltage and the q-axis voltage output by the inverter is calculated. The deviation calculation result is input into the q-axis voltage controller, superimposed with the d-axis capacitor cross-coupling term, and then the d-axis current reference value is output. The q-axis capacitor cross-coupling compensation term is calculated based on the d-axis feedback voltage, the grid angular frequency and the filter capacitor.

[0034] The deviation between the q-axis current reference value and the q-axis current output by the inverter is calculated, and the deviation calculation result is input into the q-axis current controller and superimposed with the d-axis inductance cross-coupling compensation term to generate a modulation signal Eq, where the d-axis inductance cross-coupling compensation term is calculated based on the d-axis feedback current, the grid angular frequency and the filter inductance.

[0035] It should be noted that the above-mentioned d-axis voltage controller, current controller and q-axis voltage controller, current controller are all PI controllers, and the superposition processing process in this application is common knowledge in the control field, and will not be described in detail in this embodiment.

[0036] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. The scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A photovoltaic power generation system grid control method, characterized in that: The control method comprises the following steps: Acquiring characteristic parameters of the photovoltaic power generation system, and calculating a first virtual inertia and a second virtual inertia based on the characteristic parameters, wherein the characteristic parameters of the photovoltaic power generation system include an open circuit voltage, a short circuit current, a fill factor, a power temperature coefficient, a total power generation efficiency, a current temperature, an irradiance, a current photovoltaic power generation system power, a DC capacitor, a DC rated voltage, a grid rated angular frequency, and a grid angular frequency; According to the direction of the grid frequency change, the first virtual inertia or the second virtual inertia is selected as the current virtual inertia of the photovoltaic power generation system; Based on the characteristic parameters of the photovoltaic power generation system and the current virtual inertia, the reference voltage phase angle and reference voltage amplitude are obtained respectively; The three-phase voltage of the inverter is synthesized according to the reference voltage phase angle and the reference voltage amplitude, and the d-axis reference voltage and the q-axis reference voltage are obtained through abc / dq transformation; The modulation signal Ed is calculated based on the d-axis reference voltage, and the modulation signal Eq is calculated based on the q-axis reference voltage; The modulation signals Ed and Eq are converted into PWM drive signals after abc / dq conversion, and the PWM drive signals are input into each switch tube of the photovoltaic inverter to complete the grid control of the photovoltaic power generation system.

2. The photovoltaic power generation system grid control method according to claim 1, characterized in that: Calculating a first virtual inertia based on characteristic parameters of the photovoltaic power generation system specifically includes calculating the first virtual inertia when the grid frequency decreases based on the open-circuit voltage, short-circuit current, fill factor, power temperature coefficient, and total power generation efficiency of the photovoltaic power generation system, as well as the current temperature, irradiance, current photovoltaic power generation system power, DC capacitance, DC rated voltage, grid rated angular frequency, and grid angular frequency.

3. The photovoltaic power generation system grid control method according to claim 2, characterized in that: Calculating the second virtual inertia based on the characteristic parameters of the photovoltaic power generation system specifically includes: calculating the second virtual inertia when the grid frequency increases based on the current photovoltaic power generation system power, DC capacitance, DC rated voltage, grid rated angular frequency, and grid angular frequency.

4. The photovoltaic power generation system grid control method according to claim 3, characterized in that: Based on the characteristic parameters of the photovoltaic power generation system and the value of the virtual inertia of the current photovoltaic power generation system, the reference voltage phase angle and reference voltage amplitude are obtained respectively, specifically including: Calculating the output inverter angular frequency according to the preset active reference power, actual active power, virtual inertia of the current photovoltaic power generation system, damping coefficient, and rated angular frequency of the grid, and integrating the inverter angular frequency to obtain a reference voltage phase angle; The reference voltage amplitude is calculated based on the preset reactive reference power, actual reactive power, voltage coefficient, and grid rated voltage amplitude.

5. The photovoltaic power generation system grid control method according to claim 4, characterized in that: The modulation signal Ed is obtained based on the d-axis reference voltage calculation, specifically including: The deviation between the d-axis reference voltage and the d-axis voltage output by the inverter is calculated, and the deviation calculation result is input into the d-axis voltage controller for superposition with the q-axis capacitor cross-coupling term to output the d-axis current reference value; The deviation between the d-axis current reference value and the d-axis current output by the inverter is calculated, and the deviation calculation result is input into the d-axis current controller and superimposed with the q-axis inductance cross-coupling compensation term to generate the modulation signal Ed.

6. The photovoltaic power generation system grid control method according to claim 5, characterized in that: The modulation signal Eq is obtained based on the q-axis reference voltage calculation, specifically including: The deviation between the q-axis reference voltage and the q-axis voltage output by the inverter is calculated, and the deviation calculation result is input into the q-axis voltage controller, superimposed with the d-axis capacitance cross-coupling term, and then the d-axis current reference value is output; The deviation between the q-axis current reference value and the q-axis current output by the inverter is calculated, and the deviation calculation result is input into the q-axis current controller and superimposed with the d-axis inductance cross-coupling term to generate the modulation signal Eq.

7. The photovoltaic power generation system grid control method according to claim 1, characterized in that: If the grid frequency change rate is less than 0, the first virtual inertia is selected as the current virtual inertia of the photovoltaic power generation system; if the grid frequency change rate is greater than 0, the second virtual inertia is selected as the current virtual inertia of the photovoltaic power generation system.

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