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Neutral point clamped H-bridge photovoltaic inverter and method for inhibiting common mode leakage current

A photovoltaic inverter, common mode suppression technology, applied in photovoltaic power generation, AC power input conversion to DC power output, electrical components and other directions, can solve common mode voltage fluctuations, personal safety hazards, common mode leakage current and other problems, Achieve common mode leakage current suppression, improve efficiency, and improve output power quality.

Inactive Publication Date: 2015-03-11
SHANDONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The common-mode leakage current generated by the non-isolated photovoltaic inverter system will seriously endanger personal safety, especially in the traditional single-phase full-bridge inverter, if the unipolar switching modulation strategy is adopted, the common-mode Large fluctuations in voltage, which in turn cause serious common-mode leakage current problems

Method used

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  • Neutral point clamped H-bridge photovoltaic inverter and method for inhibiting common mode leakage current
  • Neutral point clamped H-bridge photovoltaic inverter and method for inhibiting common mode leakage current
  • Neutral point clamped H-bridge photovoltaic inverter and method for inhibiting common mode leakage current

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Embodiment 1

[0044] figure 2The common-mode leakage current suppression circuit in the inverter structure shown is based on the traditional single-phase full-bridge inverter circuit by adding two switch tubes S5, S6 and four diodes D1 to D4, and the added two switches The function of the tubes S5 and S6 is to provide a freewheeling circuit for the current during the high-frequency switching operation to ensure that the common-mode voltage of the system is constant during the high-frequency switching operation. Two of the four added diodes are used to provide In the freewheeling circuit, the other two diodes are used to clamp the common-mode voltage to half of the DC voltage during the freewheeling process, thereby further suppressing the magnitude of the common-mode leakage current.

[0045] The modulation mode of the switch is divided into four stages in one cycle of the grid voltage, namely mode 1 to mode 4:

[0046] In mode 1 of the positive half cycle of the grid voltage, the inverte...

Embodiment 2

[0049] image 3 The common-mode leakage current suppression circuit in the inverter structure shown is based on the traditional H4 bridge inverter circuit by adding four switch tubes S5 to S8 and two diodes D1 and D2, in which during the entire power frequency cycle image 3 The switching modulation strategy of S1 to S6 in the four switching states of mode 1 to mode 4 of the shown inverter is the same as that of S1 to S6 in the first embodiment, image 3 The two switches S7 and S8 in the shown inverter are complementary to S1 and S4 in the positive half cycle of the grid voltage, and complementary to S2 and S3 in the negative half cycle.

[0050] In this way, during the whole cycle of the grid voltage, the common mode voltage of the inverter remains at U dc / 2, so the common-mode leakage current I cm =C PV U cm / dt will be greatly suppressed, thereby eliminating the danger of personal or equipment leakage current.

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Abstract

The invention discloses a neutral point clamped H-bridge photovoltaic inverter and method for inhibiting a common mode leakage current. The photovoltaic inverter comprises a photovoltaic cell panel, a DC side filter circuit, a single-phase full-bridge inverter circuit and an AC side filter circuit which are connected in series with one another in sequence, wherein a common mode leakage current inhibiting circuit is connected in series between the DC side filter circuit and the single-phase full-bridge inverter circuit; during the whole period of the grid voltage, by controlling the action of switches in the single-phase full-bridge inverter circuit and the common mode leakage current inhibiting circuit, the common mode voltage of the photovoltaic inverter is always kept Udc / 2 under the high-frequency action of the switches, so that the intensity of the common mode leakage current is inhibited, and the switch modulation strategy of the photovoltaic inverter can avoid current waveform distortion caused by the fluctuation influence of the grid power or operation at non-unit power factors.

Description

technical field [0001] The invention relates to a non-isolated photovoltaic grid-connected inverter, in particular to a midpoint-clamped H-bridge photovoltaic inverter for suppressing common-mode leakage current and a working method thereof. Background technique [0002] In recent years, with the continuous consumption of fossil fuels worldwide, the problem of energy shortage has become increasingly serious. Therefore, the research on renewable energy has attracted more and more attention from all over the world. Solar photovoltaic power generation technology is an important field of renewable energy applications. The photovoltaic inverter is a key part of the grid-connected photovoltaic power generation system. Its main function is to convert the direct current generated by photovoltaic panels into alternating current that is synchronized with the grid. In the solar photovoltaic grid-connected system, the traditional photovoltaic grid-connected inverter generally installs a...

Claims

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Application Information

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IPC IPC(8): H02M7/487H02M1/12
CPCH02M7/487H02M1/123Y02E10/56
Inventor 高峰周立为
Owner SHANDONG UNIV