Power imbalance control method of common direct-current bus cascade type photovoltaic inverter

Abstract

The invention discloses a power imbalance control method of a common direct-current bus cascade type photovoltaic inverter, and belongs to the technical field of photovoltaic power generation in the field of electrical engineering. The objective of the invention is to solve the problem of power imbalance of a common direct current bus cascade type photovoltaic inverter. The method comprises the following steps: controlling the voltage of each direct-current bus in the three-phase cascaded H-bridge inverter, enabling a photovoltaic array corresponding to each common direct-current bus to work at a maximum power point, obtaining a grid-connected current active component reference value, and performing grid-connected current control according to the active component reference value and a reactive component reference value; and performing third harmonic compensation according to the three-phase modulation voltage obtained in the previous step, and calculating the working mode of each H-bridge converter according to the modulation voltage after the third harmonic compensation. Compared with the prior art, the linear modulation range of the common direct-current bus cascade type photovoltaic inverter is further expanded, and the capacity of the common direct-current bus cascade type photovoltaic inverter for coping with power imbalance is improved.

Description

technical field [0001] The invention belongs to the photovoltaic power generation technology in the field of electrical engineering, and in particular relates to a power unbalance control method of a common DC bus cascading photovoltaic inverter. Background technique [0002] Due to the limitation of semiconductor switching devices, it is difficult for traditional centralized inverters to further increase the rated power in high-voltage and high-power photovoltaic systems. At the same time, in order to realize the medium voltage grid connection, the traditional centralized inverter needs a bulky power frequency transformer, which increases the volume of the inverter. The cascading photovoltaic inverter adopts a modular design, which can realize high-voltage output through the cascade of many modules, and realize high-voltage grid connection without the need of a power frequency transformer; at the same time, the isolated DC in the cascading inverter The / DC circuit enables ...

AI Technical Summary

Problems solved by technology

[0009] 1) The improved MPPT algorithm can effectively solve the problem of H-bridge power imbalance, but it will greatly reduce the efficiency of the inverter

[0010] 2) The reactive power compensation strategy can deal with severe power imbalance, but this method will reduce the system power factor

[0011] 3) The third harmonic compensation strategy improves the linear modulation range of the H-bridge converter to 1.155, but its ability to deal with power imbalance is still weak and cannot deal with more serious power imbalance situations

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