A non-isolated five-level inverter for suppressing system leakage current

Abstract

A non-isolated five-level inverter for suppressing system leakage current is provided. The non-isolated five-level inverter includes a first circuit, a second circuit, a freewheeling circuit and a full bridge circuit. The first end of the first circuit is connected to the positive electrode of the battery, and the second end thereof is connected to the first end of the freewheeling circuit. The first end of the second circuit is connected with the second end of the freewheeling circuit, and the second end of the second circuit is connected with the negative electrode of the battery. The firstterminal and the third terminal of the full bridge circuit are respectively connected with the first circuit and the second circuit, and the second terminal and the fourth circuit of the full bridge circuit are connected with the AC system side. After the switching devices in the first circuit, the second circuit, the freewheeling circuit and the full-bridge circuit are turned on in each operationstate, the current path formed can keep the common-mode voltage of the non-isolated five-level inverter constant. This embodiment can solve the voltage balance problem of the clamping capacitor. In one switching cycle, the clamping capacitor charge-discharge time is equal, so that the common-mode voltage of the five-level inverter is guaranteed to be constant.

Description

technical field [0001] The invention relates to the field of control technology, in particular to a non-isolated five-level inverter for suppressing system leakage current. Background technique [0002] At present, in the photovoltaic grid-connected system, the photovoltaic inverter plays an important role in the process of electric energy conversion. As an important interface between photovoltaic cells and the grid, photovoltaic grid-connected inverters can be divided into isolated inverters and non-isolated inverters according to whether the inverter system contains an isolation transformer. In an isolated inverter system, a high-frequency transformer is usually installed on the DC side or a low-frequency transformer is installed on the low-frequency side. The transformer not only boosts the DC voltage of the photovoltaic cell, but also isolates the DC side and the AC side, so that there is no DC loop between the two. However, the existence of the transformer increases t...

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Problems solved by technology

In this topology, the switching tubes S1-S4 bear most of the switching loss, and also share the conduction loss in the active state

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