Zero current switching full-bridge type non-isolated photovoltaic grid-connected inverter

Abstract

The invention provides a non-isolated photovoltaic grid-connected inverter and switch control timing sequence thereof, wherein the non-isolated photovoltaic grid-connected inverter enables high-frequency soft switching work to be achievable and is low in leakage current. The non-isolated photovoltaic grid-connected inverter comprises a voltage division capacitance branch (1), a high-frequency master switch unit (2), a resonance network (3), a clamping branch (4) and a low-frequency change-over switch unit (5). According to the non-isolated photovoltaic grid-connected inverter and the switch control timing sequence thereof, two controllable switching tubes, a diode and two groups of inductor and capacitor series branches are added to a one-phase six-switch full bridge inversion circuit (also know as 'H6' topology) to form the resonance network to provide the zero current switching work condition for the master switch unit, and therefore the soft switching work of high-frequency switching is achieved, and switching loss can be reduced greatly; common-mode voltage values at a power transmission stage, at a resonance stage and at a follow current stage are enabled to be identical and constant by matching with the switch control timing sequence, and therefore the leakage current of the non-isolated photovoltaic grid-connected inverter is eliminated; and high frequency of the non-isolated photovoltaic grid-connected inverter is achieved, and size, weight and cost of a grid-connected inverter can be reduced greatly.

Description

technical field [0001] The invention relates to a soft switching technology of a non-isolated photovoltaic grid-connected inverter, and belongs to the technical field of high-efficiency grid-connected inverter topology. 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 full...

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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