Five-level inverter

Abstract

The invention provides a five-level inverter. The five-level inverter comprises a first energy storage device, a second energy storage device, a direct-current boosting circuit, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first diode, a second diode, a first anti-reflux tube and a second anti-reflux tube, wherein the first diode and the second diode are connected in series on a first branch circuit, the second diode and the fifth switch tube are connected in series on a second branch circuit, the first diode enables current flow of the first branch circuit to flow from a first terminal to a second terminal of the first branch circuit, and the second diode enables current flow of the second branch circuit to flow from a first terminal to a second terminal of the second branch circuit. The high-frequency leakage current of the five-level inverter is zero, and compared with a three-level inverter, the voltage efficiency of the five-level inverter is high.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a five-level inverter. Background technique [0002] Inverters can be divided into off-grid inverters and grid-connected inverters according to different application occasions and control methods. In grid-connected inverters, they can be divided into transformer-isolated inverters according to whether they have a transformer or not. transformers and transformerless inverters. Due to the advantages of simple system structure, high efficiency, small size and low cost, the transformerless inverter has been developed rapidly. It has become the mainstream of photovoltaic medium and small power. [0003] However, since the transformerless inverter cannot achieve electrical isolation between the DC input source and the AC grid, making the high-frequency leakage current zero is a key indicator to ensure the stability of the transformerless inverter. figure 1 It is a transfor...

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Problems solved by technology

[0003] However, since the transformerless inverter cannot achieve electrical isolation between the DC input source and the AC grid, making the high-frequency leakage current zero is a key indicator to ensure the stability of the transformerless inverter.

figure 1 It is a transformerless inverter with H6 topology. When the inverter is in the first working mode, the switches S2, S4 and S5 are turned on, and the common-mode voltage is V, where V is the output of the DC voltage input Voltage value, in the second working mode, the switch tube S4 is turned on, and the common-mode voltage is V; in the third working mode, the switch tubes S1, S3 and S6 are turned on, and the common-mode voltage is V, it can be seen that , figure 1 The common-mode voltage of the inverter shown is a constant V, so the high-frequency leakage current is zero, which ensures the stability of the inverter, but the inverter is a three-level inverter, so the efficiency is very low

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