Seven-level circuit, grid-connected inverter and modulation method and device for grid-connected inverter

Abstract

The invention provides a seven-level circuit. The seven-level circuit comprises a direct current boosted circuit and a symmetrical double Buck circuit, wherein the direct current boosted circuit comprises: a fourth capacitor and a direct current chopper are connected with a direct current power supply in parallel, and an eighth switch tube is connected between the common terminal of a second switch tube and a second diode and the common terminal of the direct current chopper and a fourth capacitor; the symmetrical double Buck circuit comprises: a first capacitor and a second capacitor are connected in series and then are connected with the two sides of the direct current power supply in parallel, a first diode and a second diode are connected in series and then are connected with the direct current power supply in parallel, a first switch tube is arranged between the first capacitor and the first diode, and a second switch tube is arranged between the second diode and the second capacitor; a first inductor is arranged between the first diode and the output end of the seven-level circuit; a second inductor is arranged between the common terminal of the second switch tube and the second diode and the output end of the seven-level circuit; and the common point of the first capacitor and the second capacitor is connected with the common point of the first diode and the second diode. The invention provides the seven-level circuit, a grid-connected inverter and a modulation method and a modulation device for the grid-connected inverter, which takes leakage current and high efficiency into consideration.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a seven-level circuit, a grid-connected inverter and a modulation method and device thereof. Background technique [0002] The classification of inverters is generally divided into off-grid inverters and grid-connected inverters according to the different application occasions and control methods of the inverters. It can be divided into transformer-isolated inverters and transformerless inverters. [0003] Due to the advantages of simple system structure, high efficiency, small size and low cost, the transformerless inverter has been developed rapidly. [0004] However, since the transformerless inverter cannot realize the electrical isolation between the DC input source and the AC load, the leakage current problem is one of the key indicators of its reliability. [0005] In order to obtain higher efficiency, a unipolar modulation strategy is often used, and the tradi...

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Problems solved by technology

[0004] However, since the transformerless inverter cannot realize the electrical isolation between the DC input source and the AC load, the leakage current problem is one of the key indicators of its reliability.

[0005] In order to obtain higher efficiency, a unipolar modulation strategy is often used, and the traditional H4 topology can no longer take into account leakage current and high efficiency at the same time

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