Cascaded H bridge multilevel converter and control method thereof

Abstract

A cascaded H bridge multilevel converter and a control method thereof are provided. The converter includes two passive DC buses and a conversion circuit of which the three phases are of the same structure. The conversion circuit includes n cascaded inverter modules of the same structure. Each inverter module includes a photovoltaic sub module and an H bridge unit. Each photovoltaic sub module is a three-port interleaved parallel Boost LLC DC converter. Of the two input ports on the primary side of each photovoltaic sub module, one input port is connected with the output end of a solar photovoltaic power generation module, and the other input port is connected across the two DC buses. The output port of each photovoltaic sub module is connected with the input port of the corresponding H bridge unit. In each phase of conversion circuit, the output ports of the n H bridge units are cascaded to form an output port of the phase of conversion circuit. Photovoltaic module maximum power point tracking and LLC DC converter output voltage control are realized by controlling the duty ratio and switching frequency of a switching tube. Therefore, the problem that the intra-phase and inter-phase output power of the cascaded H bridge converters in a large-scale photovoltaic grid-connected power generation system is imbalanced is solved.

Description

Technical field [0001] The invention relates to the technical field of power electronic converters, and is a cascaded H-bridge multilevel converter for large-scale photovoltaic systems and a control method thereof. Background technique [0002] The rapid development of economy and society has led to the continuous growth of human demand for energy. The development and utilization of renewable energy is essential to the sustainable development of a country, and photovoltaics are considered to be the most promising renewable energy technology. one. In recent years, the application of large-scale photovoltaic grid-connected power generation systems has shown an increasing trend worldwide. In order to connect photovoltaic units, improve photovoltaic energy utilization, and improve photovoltaic system reliability, the development of power electronic converters suitable for photovoltaic systems has become Research hotspots at home and abroad. [0003] The grid-connected converter is a ...

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Problems solved by technology

[0004] Purpose of the invention: In order to solve the problem of unbalanced output power between the phases and phases of the cascaded H-bridge converter in the large-scale photovoltaic grid-connected power generation system, the present invention proposes a cascaded H-bridge multi-level converter and its control method

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