Power equilibrium control method for reducing DC voltage fluctuation of cascaded H-bridge inverter

Abstract

The invention discloses a power equilibrium control method for reducing DC voltage fluctuation of a cascaded H-bridge inverter, and aims to solve the problem that power generation quantity is reduced caused by relatively large DC-side voltage fluctuation. The power equilibrium control method comprises the following steps of controlling a total DC-side voltage to achieve tracking of a maximum power point voltage of the DC-side voltage of each H-bridge unit and obtain an active current instruction value of a system; controlling decoupling of a network-side current, where independent control on an active current and reactive current can be achieved, and meanwhile, a total modulation wave voltage of the inverter is generated; and performing power equilibrium control between units, an accurate on-off state of each H-bridge unit is determined and power equilibrium control of each H-bridge unit and maximum power tracking of each H-bridge unit are achieved by sequencing an error of the DC-side voltage of each H-bridge unit. By the method, various working conditions can be adapted, stable running of the cascaded H-bridge photovoltaic inverter within a relatively large range can be achieved, moreover, the DC-side voltage fluctuation can be reduced, and the power generation quantity of the system is improved.

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] 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 generatio...

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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