Power Balance Control Method for Reducing DC Voltage Fluctuation of Cascaded H-Bridge Inverters

Abstract

The invention discloses a power balance control method for reducing DC voltage fluctuations of cascaded H-bridge inverters. The purpose is to solve the problem of system power generation reduction caused by large DC side voltage fluctuations. The method includes the following steps: total DC side voltage control, It is used to realize the DC side voltage of each H-bridge unit to track its maximum power point voltage, and to obtain the system active current command value; the decoupling control of the grid side current can realize the independent control of active current and reactive current, and at the same time generate the inverter total Modulated wave voltage; inter-unit power balance control, by sorting the DC side voltage errors of each H-bridge unit, determine the correct switching state of each H-bridge unit to achieve power balance control between each H-bridge unit and the maximum of each H-bridge unit power tracking. This method can better adapt to various working conditions, not only can realize the stable operation of the cascaded H-bridge photovoltaic inverter in a large range, but also can reduce the voltage fluctuation of the DC side and increase the power generation of the system.

Description

Technical field [0001] The invention relates to a power balance control method for reducing DC voltage fluctuations of cascaded H-bridge photovoltaic inverters, and belongs to the technical field of power balance control of cascaded H-bridge photovoltaic grid-connected inverters. Background technique [0002] Grid-connected photovoltaic power generation has attracted attention due to its clean energy and environmental friendliness. Faced with the problems of how to improve the efficiency of photovoltaic systems and reduce the cost of power generation, cascaded H-bridge multilevel inverters have become an advantage due to their modularity, easy expansion, high system efficiency, and small total harmonic distortion (THD) of grid-connected currents. Research hotspots. In addition, each power unit of the cascaded H-bridge multi-level inverter requires an independent DC power supply, which is just in line with the characteristics of photovoltaic module power generation, making it pos...

AI Technical Summary

Problems solved by technology

[0008] (1) The existing technology can improve the power imbalance problem of the cascaded H-bridge photovoltaic inverter to a certain extent, but the adjustment range is small. When the system is seriously unbalanced, the system cannot run stably

[0009] (2) The power unbalance problem of the cascaded H-bridge photovoltaic inverter can be suppressed by compensating reactive power, but when the system is seriously unbalanced, the power factor of the inverter will be too low to meet the grid-connected requirements

[0010] (3) The hybrid modulation strategy can effectively expand the stable operating range of the system, but it will cause large fluctuations in the DC side voltage, making the photovoltaic panels deviate from the maximum power point and reducing the power generation of the photovoltaic panels

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