Seven-level circuit, a grid-connected inverter and modulation method and device of seven-level circuit

Abstract

The invention relates to a seven-level circuit, a grid-connected inverter and a modulation method and device of the seven-level circuit. The seven-level circuit comprises a DC boosted circuit and a symmetric dual-Buck circuit; the DC boosted circuit comprises a DC chopper and a fourth capacitor which are connected in series; an eighth switching tube is connected between the common terminal of the DC chopper and the fourth capacitor and the common terminal of a first switching tube and a first diode; the symmetric dual-Buck circuit comprises the following structures that a first capacitor and a second capacitor are connected in series and then connected to two sides of a DC power supply in parallel, the first diode and a second diode are connected in series and then connected with the DC power supply in parallel, the first switching tube is arranged between the first capacitor and the second diode, and a second switching 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, and a second inductor is arranged between the common terminal of the second switching tube and the second diode and the output end of the seven-level circuit; and a common point of the first capacitor and the second capacitor is connected with a common point of the first diode and the second diode. The seven-level circuit, the grid-connected inverter and a control method and device of the grid-connected inverter give consideration to two aspects of current and high efficiency.

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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