Zero-voltage switching Heric type non-isolated photovoltaic grid-connected inverter

Abstract

The invention discloses a full-bridge non-isolated photovoltaic grid-connected inverter and a switching control timing sequence of the full-bridge non-isolated photovoltaic grid-connected inverter which can achieve zero-voltage turning-on and zero-voltage turning-off of high-frequency switching tubes and is high in efficiency and high in reliability. The full-bridge non-isolated photovoltaic grid-connected inverter comprises a capacitor branch 1, a high-frequency master switching unit 2 and a resonance network 3. According to the full-bridge non-isolated photovoltaic grid-connected inverter, the two controllable high-frequency switching tubes, four controllable low-frequency switching tubes, a diode, two inductors and four capacitor elements are additionally arranged based on a one-phase four-switch full-bridge inversion circuit to form the resonance network to achieve zero-voltage turning-on and zero-voltage turning-off of the master switching unit, and therefore switching losses can be greatly reduced. The full-bridge non-isolated photovoltaic grid-connected inverter is high in frequency and high in efficiency, and the size, the weight and the cost of the grid-connected inverter can be substantially reduced.

Description

technical field [0001] The invention relates to a zero-voltage switch Heric type non-isolated photovoltaic grid-connected inverter, which 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. Such as patent EP 1369985 A2 (referred to as Heric topology), patent US 7411802 B2 (referred to as H5 topology), patent CN101814856A, etc., the high-frequency switching tubes in these patented technologies are all running on hard switches. In order to achieve high conversion efficiency, these inverters The converter generally works at a switching frequency of 10-20kHz. Therefore, 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. [0...

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Problems solved by technology

[0003] 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

It can be seen that if the switching loss of the existing non-isolated grid-connected inverter can be reduced and the soft switching operation of high-frequency switching can be realized, the operating frequency of the grid-connected inverter can be greatly increased and the filter volume can be reduced, such as patents 201310135312.9 and The patent 201310134383.7 realizes the soft switching operation of the high-frequency switch of the non-isolated grid-connected inverter. However, since the power circuit needs to flow through more switch tubes, there is a large conduction loss

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