Hybrid modulation strategy based power balance control method for cascade H-bridge inverter

Abstract

The invention discloses a hybrid modulation strategy based power balance control method for a cascade H-bridge inverter and aims to solve a problem of incapability of stable operation of a system due to input power imbalance of a photovoltaic battery panel on a DC side of the photovoltaic inverter. The method includes steps of 1, master DC side voltage control used for realizing maximal power point voltage tracking by H-bridge unit DC side voltages and obtaining a system active current command value; 2, grid side current decoupling control capable realizing independent control of active current and reactive current and generating inverter total modulation wave voltage; 3, inter-unit power balance control including determining the correct switching states of each H-bridge unit so as to realize the power balance control among the H-bridge units and the maximal power tracking of the H-bridge units through DC side voltage error ranking of the H-bridge units. The method can be suitable for different kinds of working conditions. By adopting the method, stable operation of the cascade H-bridge photovoltaic inverter in a comparatively large range and system power generation capacity can be guaranteed.

Description

technical field [0001] The invention relates to a power balance control method of a single-phase cascaded H-bridge photovoltaic grid-connected inverter, and belongs to the technical field of power balance control of cascaded photovoltaic grid-connected inverters. Background technique [0002] Photovoltaic grid-connected power generation has attracted much attention because it provides clean energy and is environmentally friendly. Facing the problems of how to improve the efficiency of photovoltaic system and reduce the cost of power generation, the cascaded H-bridge multilevel inverter has become a popular choice due to its modularization, easy expansion, high system efficiency, and low total harmonic distortion (THD) of grid-connected current. research hotspot. In addition, each power unit of the cascaded H-bridge multi-level inverter needs an independent DC power supply, which is just in line with the characteristics of photovoltaic module power generation, making MPPT co...

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Problems solved by technology

[0011] The problem to be solved by the present invention is to overcome the limitations of the above-mentioned solutions, aiming at the problem that the power imbalance of cascaded H-bridge photovoltaic inverters causes the system to be unable to operate stably, and proposes a cascaded H-bridge photovoltaic grid-connected system based on a hybrid modulation strategy Inverter Power Balance Control Method

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