Zero-voltage transition full-bridge non-isolated photovoltaic grid-connected inverter

Abstract

The invention provides a non-isolated photovoltaic grid-connected inverter capable of performing high-frequency soft switching operation, with low leakage current, and a switching control time sequence thereof. The non-isolated photovoltaic grid-connected inverter comprises voltage-dividing capacitance branch (1), a high-frequency main switch unit (2), a resonance network (3), a clamping branch (4) and a low-frequency reversing switching unit (5). The non-isolated photovoltaic grid-connected inverter has the advantages that two controllable switching tubes, a diode and two inductance-capacitance branches are respectively added on the basis of a single-phase six-switch full-bridge inverter circuit (known as 'H6' topology) to form the resonance network to provide zero-voltage switching operating conditions for the main switch unit, the soft switching operation of a high-frequency switch is realized, and the switch loss can be greatly reduced; common mode voltage can also be ensured to be a constant voltage value at a power transmission stage, a resonance stage and a continuous current stage through the switching time sequence, so that the leakage current of the non-isolated grid-connected inverter is eliminated; and the non-isolated photovoltaic grid-connected inverter can realize high frequency, and is beneficial to greatly reducing the volume, the weight and the cost.

Description

technical field [0001] The invention relates to the technical field of high-efficiency grid-connected inverter topology, in particular to a soft switching technology of a non-isolated photovoltaic grid-connected inverter. Background technique [0002] Compared with the isolated structure, the non-isolated photovoltaic grid-connected inverter has the advantages of high efficiency, small size, light weight and low cost. However, due to the existence of the parasitic capacitance of the solar panel to the ground, the switching action of the switching device of the grid-connected inverter may generate a high-frequency time-varying voltage to act on the parasitic capacitance, and the leakage current induced by this may exceed the allowable range. The generation of high-frequency leakage current will bring conduction and radiation interference, increase the harmonics and loss of the incoming current, and even endanger the safety of equipment and personnel. [0003] Bipolar SPWM fu...

AI Technical Summary

Problems solved by technology

However, at the current technical level, these inverters generally work at a switching frequency of 10~20kHz, and relatively large filter inductors and filter capacitors are required, which not only increases the volume and weight of the grid-connected inverter, but also increases the cost

[0004] The main factor limiting the increase of the switching frequency of non-isolated grid-connected inverters is the switching loss of high-frequency switches. With the increase of the switching frequency of the inverter, the switching loss increases significantly, resulting in a rapid decline in inverter efficiency and the need for a larger heat sink

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