Eight-switch-tube transformerless type photovoltaic grid-connected inversion circuit and control method

Abstract

The invention discloses an eight-switch-tube transformerless type photovoltaic grid-connected inversion circuit and a control method and belongs to the power electronics field. An inverter controls the motions of eight switch tubes in the inversion circuit through a given switch tube driving signal and forms a zero-level follow current loop through the motions of the switch tubes and diodes D1 andD2 in a follow current phase. The voltage of the follow current loop can be half of an input voltage in the follow current phase. The common mode voltage of the inverter always maintains Udc / 2. The high frequency pulsation of the common mode voltage can be eliminated and an earth leakage current is effectively restrained. Through constructing the new follow current loop, a follow current path ischanged so that the follow current path does not pass through a body diode with a large conduction loss and the conduction loss is reduced. Simultaneously, compared with other midpoint clamping modes,in a topology, there is no switch tube which is always in a high frequency work state, switch losses are reduced and efficiency is increased. The method possesses advantages that a topology structureis simple; the efficiency is high; and a modulation strategy is simple and so on.

Description

technical field [0001] The invention belongs to the technical field of power electronic photovoltaic grid-connected power generation, and specifically relates to an eight-switch tube transformerless photovoltaic grid-connected inverter circuit and a control method. Background technique [0002] With the depletion of traditional energy sources, it is imminent to seek new energy sources. Solar energy has become the first choice for new energy workers due to its endless and safe and reliable features. The single-phase non-isolated photovoltaic grid-connected inverter has the advantages of small size, light weight, low cost, simple structure and improved system efficiency because the transformer is removed, and it has become one of the mainstreams of research on photovoltaic grid-connected power generation systems. [0003] However, due to the removal of the transformer, the parasitic capacitance of the inverter to the ground and various filter inductors and filter capacitors i...

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Problems solved by technology

[0005] Aiming at the problem of large ground leakage current in single-phase non-isolated photovoltaic grid-connected inverters, the present invention proposes a high-efficiency, low-leakage current non-isolated eight-switch tube transformerless photovoltaic grid-connected inverter circuit

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