Leakage current suppression method and apparatus for photovoltaic inverter, inverter, and photovoltaic system

Abstract

The present application is applicable to the technical field of photovoltaic power generation, and provides a leakage current suppression method and apparatus for a photovoltaic inverter, an inverter, and a photovoltaic system. The method comprises: acquiring a first common-mode injection voltage and a three-phase differential mode carrier voltage of an inverter; superposing the first common-mode injection voltage onto the three-phase differential mode carrier voltage; performing notch filtering to a preset harmonic number on the superposed three-phase differential mode carrier voltage, to obtain a target carrier voltage, the preset harmonic number being a harmonic number at which the proportion of a peripheral frequency of a resonance point exceeds a preset threshold value when using a power grid frequency as a fundamental wave calculation parameter; comparing the target carrier voltage with a modulation voltage, and then driving a three-level circuit to output. The present application can eliminate a voltage amount to suppress a leakage current, and uses an open-loop control mode, such that control failure caused by problems such as control delay is avoided, while waveform changes before and after a notch are small, and the clamping of a switch transistor will not be affected in a DPWM modulation mode.

Description

Photovoltaic inverter leakage current suppression method, device, inverter and photovoltaic system

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on November 22, 2023, with application number 202311569026.3 and application name “Photovoltaic inverter leakage current suppression method, device, inverter and photovoltaic system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of photovoltaic power generation technology, and in particular to a method and device for suppressing leakage current of a photovoltaic inverter, an inverter, and a photovoltaic system. Background Art

[0003] Photovoltaic power generation is a renewable energy source. In household string-type photovoltaic systems, PV panels are directly connected to the grid via a non-isolated inverter. Parasitic capacitance exists between the PV panels and the grounded metal frame. When the inverter is grid-connected, a common-mode loop forms between the ground, PV panels, inverter, and grid, generating a common-mode oscillating current, also known as leakage current. This leakage current can reduce system stability. Excessive leakage current can easily exceed the protection threshold of the inverter's ground fault circuit interrupter (GFCI), falsely triggering a GFCI over-limit fault.

[0004] The magnitude of leakage current is mainly related to the parasitic capacitance and common-mode voltage of the PV module. Among them, the parasitic capacitance is related to factors such as the area of ​​the PV module, the distance to the ground, the photovoltaic material, and the ambient humidity, and is not controlled by the inverter. The common-mode voltage is mainly related to the common-mode voltage injected by the inverter. Modulation methods such as SVPWM (Space Vector Pulse Width Modulation) and DPWM (Discontinuous-PWM, five-segment PWM) improve the bus voltage utilization rate by injecting common-mode voltage at the inverter voltage. The inverter can control the leakage current by changing the amount of common-mode voltage injection.

[0005] There are currently several methods for controlling leakage current. The first is to connect a damping resistor in series in the common-mode loop. This method is simple and reliable, but it will reduce system efficiency. The second is to connect an active damper in series in the common-mode loop through closed-loop control. However, when high-frequency leakage current exists in the system, the delay of the closed-loop control will seriously affect the control effect. The third is to reduce the common-mode voltage injection when the leakage current increases. This method can control the leakage current to not exceed the threshold, but it will reduce the bus voltage utilization rate. At the same time, when the modulation mode is DPWM, reducing the common-mode voltage will make the switch tube unable to clamp, making DPWM modulation lose its advantages.

[0006] Application Contents

[0007] The embodiment of the present application provides a method for suppressing leakage current of a photovoltaic inverter, which aims to solve the problems of low system efficiency, control failure, low bus voltage utilization, and inability to clamp the switch tube under DPWM modulation mode in traditional leakage current control methods.

[0008] The embodiment of the present application is implemented as follows: a method for suppressing leakage current of a photovoltaic inverter, comprising:

[0009] Obtaining a first common-mode injection voltage and a three-phase differential-mode carrier voltage of the inverter;

[0010] superimposing the first common-mode injection voltage on the three-phase differential-mode carrier voltage;

[0011] The superimposed three-phase differential mode carrier voltage is notched filtered with a preset harmonic order to obtain a target carrier voltage, wherein the preset harmonic order is the harmonic order whose proportion of the frequency around the resonance point exceeds a preset threshold value based on the grid frequency as the fundamental wave calculation parameter;

[0012] The target carrier voltage is compared with the modulation voltage and then drives the three-level circuit output.

[0013] Furthermore, the calculation method of the preset harmonic order includes:

[0014] The resonant frequency of the target point is calculated based on the common-mode equivalent circuit of the inverter and the transfer function of the leakage current and common-mode voltage;

[0015] The preset resonance number is calculated based on the resonance frequency of the target point and the prefabricated second common-mode injection voltage.

[0016] Furthermore, the three-phase differential-mode carrier voltage is obtained by the inverter through differential-mode current control.

[0017] Furthermore, the step of obtaining a first common-mode injection voltage of the inverter includes:

[0018] Get the pulse width modulation mode of the inverter;

[0019] The first common-mode injection voltage is calculated according to the pulse width modulation method.

[0020] In a second aspect, the present application further provides a photovoltaic inverter leakage current suppression device, comprising:

[0021] An information acquisition module, configured to acquire a first common-mode injection voltage and a three-phase differential-mode carrier voltage of the inverter;

[0022] A voltage superposition module, configured to superimpose the first common-mode injection voltage onto the three-phase differential-mode carrier voltage;

[0023] A frequency component filtering module is used to perform notch filtering of a preset harmonic order on the superimposed three-phase differential mode carrier voltage to obtain a target carrier voltage, wherein the preset harmonic order is the harmonic order whose proportion of the frequency around the resonance point exceeds a preset threshold value based on the grid frequency as the fundamental wave calculation parameter;

[0024] The carrier modulation module is used to drive the three-level circuit output after comparing the target carrier voltage with the modulation voltage.

[0025] Furthermore, the device further comprises:

[0026] A resonant frequency calculation unit, configured to calculate the resonant frequency of a target point based on the common-mode equivalent circuit of the inverter combined with a transfer function of leakage current and common-mode voltage;

[0027] The resonance number calculation unit is used to calculate the preset resonance number according to the resonance frequency of the target point and the prefabricated second common mode injection voltage.

[0028] Furthermore, the three-phase differential-mode carrier voltage is obtained by the inverter through differential-mode current control.

[0029] Furthermore, the information acquisition module includes:

[0030] A modulation mode determination submodule is used to obtain the pulse width modulation mode of the inverter;

[0031] The common-mode injection voltage calculation submodule is used to calculate and obtain the first common-mode injection voltage according to the pulse width modulation method.

[0032] In a third aspect, the present application further provides an inverter, which includes the photovoltaic inverter leakage current suppression device as described above.

[0033] In a fourth aspect, the present application also provides a photovoltaic system comprising the inverter as described above.

[0034] The beneficial effects achieved by the present application are as follows: a first common-mode injection voltage and a three-phase differential-mode carrier voltage of the inverter are obtained, the first common-mode injection voltage is superimposed on the three-phase differential-mode carrier voltage, and the superimposed three-phase differential-mode carrier voltage is notched and filtered with a preset harmonic order to obtain a target carrier voltage; finally, the target carrier voltage is compared with the modulation voltage and the three-level circuit output is driven; since the preset harmonic order is the harmonic order whose proportion of the frequency around the resonance point exceeds a preset threshold value with the grid frequency as the fundamental wave calculation parameter, the voltage component can be eliminated when the common-mode voltage is injected to suppress leakage current; an open-loop control method is adopted, and control failure will not be caused by problems such as control delay; at the same time, the waveform change before and after the notch is small, and the switch tube clamping will not be affected under the DPWM modulation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a flow chart of an embodiment of a method for suppressing leakage current of a photovoltaic inverter provided by the present application;

[0036] FIG2 is a flow chart of another embodiment of a method for suppressing leakage current of a photovoltaic inverter provided by the present application;

[0037] FIG3 is a flow chart of another embodiment of a method for suppressing leakage current of a photovoltaic inverter provided by the present application;

[0038] FIG4 is a module schematic diagram of an embodiment of a photovoltaic inverter leakage current suppression device provided by the present application;

[0039] FIG5 is a schematic diagram of a circuit topology used in a string inverter according to an embodiment of a method for suppressing leakage current of a photovoltaic inverter provided by the present application;

[0040] FIG6 is a common-mode equivalent schematic diagram corresponding to the circuit topology used by the string inverter of FIG5 ;

[0041] FIG7 is a schematic diagram of a Bode diagram of an embodiment of a method for suppressing leakage current of a photovoltaic inverter provided by the present application;

[0042] FIG8 is a schematic diagram of a common-mode injection voltage waveform according to an embodiment of a photovoltaic inverter leakage current suppression method provided by the present application;

[0043] FIG9 is a schematic diagram of a Bode diagram after notch filtering according to an embodiment of a method for suppressing leakage current of a photovoltaic inverter provided in the present application;

[0044] FIG10 is a schematic diagram of an implementation method of an embodiment of a photovoltaic inverter leakage current suppression method provided by the present application;

[0045] FIG11 is a schematic diagram showing the proportion of the frequencies f1 and f2 with a fundamental wave of 150 Hz in accordance with an embodiment of a method for suppressing leakage current of a photovoltaic inverter provided by the present application. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0047] In this application, since the preset harmonic order is the harmonic order whose proportion of the frequency around the resonance point exceeds the preset threshold value based on the grid frequency as the fundamental wave calculation parameter, the voltage component can be eliminated when the common-mode voltage is injected to suppress the leakage current. The open-loop control method is adopted, and control failure will not be caused by problems such as control delay. At the same time, the waveform change before and after the notch is small, and it will not affect the clamping of the switch tube under the DPWM modulation method.

[0048] Example 1

[0049] As shown in FIG1 to FIG11 , this embodiment provides a method for suppressing leakage current of a photovoltaic inverter, including:

[0050] S1100, obtaining a first common-mode injection voltage and a three-phase differential-mode carrier voltage of the inverter;

[0051] During implementation, the photovoltaic inverter leakage current suppression method provided by the present application is applied to a photovoltaic system, specifically, to an inverter. In other words, the steps of the photovoltaic inverter leakage current suppression method provided by the present application are executed by the inverter or the processor in the inverter. The processor can be an actual processor set in the inverter or a virtual cloud processor, without limitation.

[0052] Alternatively, the circuit topology of the string inverter is shown in FIG5 , where PV represents a photovoltaic module, which is the input of the system, and C pv The PV module is connected to a T-type three-level transformer via the DC busbar and capacitors C1 and C2. The output of the T-type three-level transformer is connected to the three-phase grid through an LCL filter. The common point N1 of the LCL capacitor is connected to the neutral point O of the three-level transformer, and the neutral point N on the grid side is connected to the ground.

[0053] Optionally, as shown in FIG10 , the inverter obtains a three-phase differential mode carrier voltage U by differential mode control. a , U b , U c .

[0054] Example 2

[0055] As shown in FIG2 , the first common-mode injection voltage is related to the modulation mode, and the step of obtaining the first common-mode injection voltage of the inverter includes:

[0056] S1101, obtaining a pulse width modulation mode of the inverter;

[0057] S1102: Calculate and obtain a first common-mode injection voltage according to a pulse width modulation method.

[0058] First, the pulse width modulation mode adopted by the inverter is obtained. The system can adopt the DPWM modulation mode or the SVPWM modulation mode. Then, the first common-mode injection voltage under the DPWM modulation mode or the SVPWM modulation mode is calculated.

[0059] S1200, superimposing the first common-mode injection voltage on the three-phase differential-mode carrier voltage;

[0060] After obtaining the first common-mode injection voltage and the three-phase differential-mode carrier voltage, the first common-mode injection voltage is superimposed on the three-phase differential-mode carrier voltage.

[0061] S1300: Perform notch filtering of a preset harmonic order on the superimposed three-phase differential mode carrier voltage to obtain a target carrier voltage, wherein the preset harmonic order is a harmonic order whose proportion of the frequency around the resonance point exceeds a preset threshold value using the grid frequency as a fundamental wave calculation parameter;

[0062] The superimposed result is notch filtered, and the harmonic order is pre-stored in the inverter. Optionally, the harmonic order can be obtained through several experimental measurements. The experimental measurement shows that there is a certain numerical harmonic within a certain grid frequency range. When the common mode voltage is injected, eliminating the frequency component corresponding to the certain numerical harmonic has a significant effect on suppressing leakage current. The certain numerical harmonic can be recorded and saved in the processor.

[0063] Optionally, the harmonic order may be multiple. In other words, eliminating the frequency components corresponding to the multiple harmonics when injecting the common mode voltage has the best effect on suppressing the leakage current.

[0064] Example 3

[0065] As shown in FIG3 , the calculation method of the preset harmonic order includes:

[0066] S1201. Calculate the resonant frequency of the target point based on the common-mode equivalent circuit of the inverter and the transfer function of the leakage current and the common-mode voltage;

[0067] S1202: Calculate a preset resonance number according to the resonance frequency of the target point and a preset second common-mode injection voltage.

[0068] The common-mode equivalent circuit of the inverter is shown in Figure 6, which can be obtained by analyzing the circuit topology of the string inverter. The common-mode equivalent circuit of the inverter is composed of the common-mode voltage 3u cm The common mode current i cm It is divided into two branches, in which the branch through the parasitic capacitance of the PV module forms a leakage current i cmg , and no leakage current will be generated in the branch through the LCL capacitor.

[0069] The transfer function of leakage current and common-mode voltage is shown below:

[0070] For example, this application uses C f =32μF, C pv =10μF, L=100μH, L g = 1000 μH for analysis, in some other embodiments, C f 、C pv ,L,L g Other parameter values ​​may also be used without limitation.

[0071] Substituting the above parameters into the transfer function, a Bode diagram (logarithmic frequency characteristic curve) is drawn as shown in FIG7 .

[0072] The logarithmic frequency characteristic curve includes two curves: the logarithmic amplitude-frequency characteristic and the logarithmic phase-frequency characteristic. The abscissa of the logarithmic amplitude-frequency characteristic curve represents frequency, scaled according to lgω (logarithmically), and the unit is radian / second (rad / s). The ordinate represents the logarithmic amplitude-frequency characteristic function value, scaled according to a linear scale, and the unit is decibel (dB). The abscissa of the logarithmic phase-frequency characteristic curve represents frequency, scaled according to lgω (logarithmically), and the unit is radian / second (rad / s). The ordinate represents the phase-frequency characteristic function value, scaled according to a linear scale, and the unit is degree.

[0073] From the Bode diagram, we can see that the transfer function has two resonant points. These two resonant points are the target points. The resonant frequencies of these two resonant points are calculated as follows:

[0074] Substituting the above parameters, we obtain f1 = 3042.74 Hz and f2 = 1802.38 Hz, which indicates that the impedance of the impedance network in Figure 7 is minimum at these two resonant frequencies. In other words, when the input common-mode voltage has AC components at these two frequencies and frequencies near them, oscillations are likely to occur in the output leakage current.

[0075] Since the common-mode voltage is mainly injected by the inverter, eliminating the voltage components of the above frequencies when injecting the common mode can avoid the generation of leakage current. Taking the above transfer function with two resonant points as an example, the resonant frequencies of the target points are f1 and f2 respectively. At this time, the common-mode injection voltage is modulated as the second common-mode injection voltage. For example, taking the DPWM modulation method as an example, Figure 8 shows the DPWM modulation method when the grid frequency is 50Hz. The common-mode injection voltage with a modulation ratio of 0.8 is the second common-mode injection voltage. Then, an FFT (Fast Fourier Transformation) is performed on the voltage to obtain the component proportions of frequencies near f1 and f2 with a fundamental wave of 150Hz, as shown in Figure 11.

[0076] By analyzing FIG11, the harmonic order whose proportion relative to the fundamental wave exceeds the preset threshold is screened out. For example, the analysis of FIG11 shows that among the 33rd to 69th harmonics (corresponding to 1650 to 3450 Hz), the 39th, 51st, and 63rd harmonics account for the largest proportion. Eliminating the components of these three frequencies when injecting common-mode voltage has a good effect on suppressing leakage current. Therefore, 39, 51, and 63 are the preset resonance orders.

[0077] It should be noted that the above-mentioned 39th, 51st, and 63rd harmonics are distance descriptions of an embodiment of the present application, rather than specific limitations on the present application. In some other embodiments, the number of selected harmonics and the order of harmonics can also use other numbers or values. For example, if the preset threshold is 0.5%, then 39 and 51 are confirmed as the preset harmonic orders without limitation.

[0078] In some possible embodiments, a notch filter is generally used to eliminate a certain frequency component in the frequency domain. The transfer function of the notch filter is:

[0079] When the grid frequency is 50 Hz, the Bode diagram of the notch filter with 39, 51, and 63 orders superimposed is shown in FIG9 .

[0080] In some possible embodiments, since the notch filter uses the grid frequency as the fundamental wave calculation parameter, the notch filter parameters need to be updated in a timely manner when the grid frequency changes to ensure that the notch filter operates under optimal parameters.

[0081] S1400 , comparing the target carrier voltage with the modulation voltage and then driving the three-level circuit output.

[0082] Carrier modulation is performed after the target carrier voltage is obtained. Specifically, the target carrier voltage can be compared with the modulation voltage to output a driving signal to a three-level circuit to drive the three-level circuit output.

[0083] During implementation, the three-level circuit is the T-type three-level circuit in Figure 5. By way of example, taking the high and low levels of the driving signal as an example, when the target carrier voltage is higher than the modulation voltage, a high-level driving signal is output, and when the target carrier voltage is lower than the modulation voltage, a low-level driving signal is output to control the on and off of each IGBT in the three-level circuit, thereby realizing the output function of driving the three-level circuit.

[0084] It should be noted that the high-level signal in the embodiment of the present application means that in the digital logic circuit, the low level represents 0 and the high level represents 1. From the perspective of the signal level, the low level is generally stipulated to be 0~0.25V and the high level is 3.5~5V.

[0085] The present application obtains a first common-mode injection voltage and a three-phase differential-mode carrier voltage of the inverter, then superimposes the first common-mode injection voltage on the three-phase differential-mode carrier voltage, and then performs notch filtering of a preset harmonic order on the superimposed three-phase differential-mode carrier voltage to obtain a target carrier voltage. Finally, the target carrier voltage is compared with the modulation voltage and the three-level circuit output is driven. Since the preset harmonic order is the harmonic order whose proportion of the frequency around the resonance point exceeds a preset threshold value based on the grid frequency as the fundamental wave calculation parameter, the voltage component can be eliminated when the common-mode voltage is injected to suppress leakage current. An open-loop control method is adopted, and control failure due to problems such as control delay will not occur. At the same time, the waveform change before and after the notch is small, and the clamping of the switch tube will not be affected under the DPWM modulation method.

[0086] Example 4

[0087] As shown in FIG4 , the present application also provides a photovoltaic inverter leakage current suppression device, comprising:

[0088] An information acquisition module 2100 is configured to acquire a first common-mode injection voltage and a three-phase differential-mode carrier voltage of the inverter;

[0089] A voltage superposition module 2200 is configured to superimpose the first common-mode injection voltage onto the three-phase differential-mode carrier voltage;

[0090] The frequency component filtering module 2300 is configured to perform notch filtering of a preset harmonic order on the superimposed three-phase differential mode carrier voltage to obtain a target carrier voltage, wherein the preset harmonic order is the harmonic order whose proportion of the frequency around the resonance point exceeds a preset threshold using the grid frequency as the fundamental wave calculation parameter;

[0091] The carrier modulation module 2400 is used to drive the three-level circuit output after comparing the target carrier voltage with the modulation voltage.

[0092] The present application obtains a first common-mode injection voltage and a three-phase differential-mode carrier voltage of the inverter, then superimposes the first common-mode injection voltage on the three-phase differential-mode carrier voltage, and then performs notch filtering of a preset harmonic order on the superimposed three-phase differential-mode carrier voltage to obtain a target carrier voltage. Finally, the target carrier voltage is compared with the modulation voltage and the three-level circuit output is driven. Since the preset harmonic order is the harmonic order whose proportion of the frequency around the resonance point exceeds a preset threshold value based on the grid frequency as the fundamental wave calculation parameter, the voltage component can be eliminated when the common-mode voltage is injected to suppress leakage current. An open-loop control method is adopted, and control failure due to problems such as control delay will not occur. At the same time, the waveform change before and after the notch is small, and the clamping of the switch tube will not be affected under the DPWM modulation method.

[0093] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the structure and implementation principle of the photovoltaic inverter leakage current suppression device described above can refer to the corresponding structures and implementation principles in the aforementioned embodiments one to three, and will not be repeated here.

[0094] Furthermore, the photovoltaic inverter leakage current suppression device provided by the present application also includes:

[0095] A resonant frequency calculation unit, configured to calculate the resonant frequency of a target point based on the common-mode equivalent circuit of the inverter combined with a transfer function of leakage current and common-mode voltage;

[0096] The resonance number calculation unit is used to calculate the preset resonance number according to the resonance frequency of the target point and the prefabricated second common mode injection voltage.

[0097] Furthermore, the three-phase differential-mode carrier voltage is obtained by the inverter through differential-mode current control.

[0098] Furthermore, the information acquisition module includes:

[0099] A modulation mode determination submodule is used to obtain the pulse width modulation mode of the inverter;

[0100] The common-mode injection voltage calculation submodule is used to calculate and obtain the first common-mode injection voltage according to the pulse width modulation method.

[0101] Example 5

[0102] In some possible embodiments, the present application further provides an inverter, which includes the photovoltaic inverter leakage current suppression device as described above.

[0103] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the structure and implementation principle of the inverter described above can refer to the corresponding structures and implementation principles in the aforementioned embodiments one to four, and will not be repeated here.

[0104] Example 6

[0105] In some possible embodiments, the present application also provides a photovoltaic system, including the inverter as described above.

[0106] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the structure and implementation principle of the photovoltaic system described above can refer to the corresponding structures and implementation principles in the aforementioned embodiments one to five, and will not be repeated here.

[0107] The present application obtains a first common-mode injection voltage and a three-phase differential-mode carrier voltage of the inverter, then superimposes the first common-mode injection voltage on the three-phase differential-mode carrier voltage, and then performs notch filtering of a preset harmonic order on the superimposed three-phase differential-mode carrier voltage to obtain a target carrier voltage. Finally, the target carrier voltage is compared with the modulation voltage and the three-level circuit output is driven. Since the preset harmonic order is the harmonic order whose proportion of the frequency around the resonance point exceeds a preset threshold value based on the grid frequency as the fundamental wave calculation parameter, the voltage component can be eliminated when the common-mode voltage is injected to suppress leakage current. An open-loop control method is adopted, and control failure due to problems such as control delay will not occur. At the same time, the waveform change before and after the notch is small, and the clamping of the switch tube will not be affected under the DPWM modulation method.

[0108] It is understandable that those skilled in the art can, under the guidance of the above embodiments, combine various implementation methods in the above embodiments, for example, combine Example 1 with Example 2 to obtain technical solutions with multiple implementation methods.

[0109] The above disclosure is only a preferred embodiment of the present application, and certainly cannot be used to limit the scope of rights of the present application. Therefore, equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A method for suppressing leakage current of a photovoltaic inverter, characterized in that: include: Obtaining a first common-mode injection voltage and a three-phase differential-mode carrier voltage of the inverter; superimposing the first common-mode injection voltage on the three-phase differential-mode carrier voltage; The superimposed three-phase differential mode carrier voltage is subjected to notch filtering of a preset harmonic order to obtain a target carrier voltage, wherein the preset harmonic order is a harmonic order whose proportion of the frequency around the resonance point exceeds a preset threshold value with the grid frequency as the fundamental wave calculation parameter; The target carrier voltage is compared with the modulation voltage and then driven to output a three-level circuit.

2. The photovoltaic inverter leakage current suppression method according to claim 1, characterized in that: The method for calculating the preset harmonic order includes: The resonant frequency of the target point is calculated based on the common-mode equivalent circuit of the inverter combined with the transfer function of the leakage current and the common-mode voltage; The preset resonance number is calculated according to the resonance frequency of the target point and the prefabricated second common mode injection voltage.

3. The photovoltaic inverter leakage current suppression method according to claim 1, characterized in that: The three-phase differential mode carrier voltage is obtained by the inverter through differential mode current control.

4. The photovoltaic inverter leakage current suppression method according to claim 1, characterized in that: The step of obtaining a first common-mode injection voltage of the inverter comprises: Get the pulse width modulation mode of the inverter; The first common-mode injection voltage is calculated according to the pulse width modulation method.

5. A photovoltaic inverter leakage current suppression device, characterized in that: include: An information acquisition module, used to acquire a first common-mode injection voltage and a three-phase differential-mode carrier voltage of the inverter; A voltage superposition module, used for superimposing the first common-mode injection voltage on the three-phase differential-mode carrier voltage; A frequency component filtering module, used for performing notch filtering of a preset harmonic order on the superimposed three-phase differential mode carrier voltage to obtain a target carrier voltage, wherein the preset harmonic order is a harmonic order whose proportion of the frequency around the resonance point exceeds a preset threshold value with the grid frequency as the fundamental wave calculation parameter; The carrier modulation module is used to drive the three-level circuit output after comparing the target carrier voltage with the modulation voltage.

6. The photovoltaic inverter leakage current suppression device according to claim 5, characterized in that: The device also includes: A resonant frequency calculation unit, used to calculate the resonant frequency of the target point according to the common-mode equivalent circuit of the inverter combined with the transfer function of the leakage current and the common-mode voltage; The resonance number calculation unit is used to calculate the preset resonance number according to the resonance frequency of the target point and the prefabricated second common mode injection voltage.

7. The photovoltaic inverter leakage current suppression device according to claim 5, characterized in that: The three-phase differential mode carrier voltage is obtained by the inverter through differential mode current control.

8. The photovoltaic inverter leakage current suppression method according to claim 5, characterized in that: The information acquisition module includes: A modulation mode determination submodule is used to obtain a pulse width modulation mode of the inverter; The common-mode injection voltage calculation submodule is used to calculate the first common-mode injection voltage according to the pulse width modulation method.

9. An inverter, characterized in that: The inverter comprises the photovoltaic inverter leakage current suppression device according to any one of claims 5 to 8.

10. A photovoltaic system, characterized in that: The photovoltaic system comprises the inverter according to claim 9.

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