Reactive power exchange method and system for photovoltaic grid-connected CHB of fault module

Abstract

The invention discloses a reactive power exchange method and system for a photovoltaic grid-connected CHB of a faulty module. The method comprises the steps that: a plurality of faulty CHB units are detected, bypass switches of the faulty CHB units are switched on, and the faulty CHB units are short circuited through the bypass switches; after the plurality of faulty CHB units are short-circuited, the magnitude and phase of zero-sequence voltage needing to be injected into the photovoltaic grid-connected CHB are calculated according to active power and reactive power exchanged between the photovoltaic grid-connected CHB and a power grid; the relation between the phase cluster voltage effective value of the photovoltaic grid-connected CHB and the active power and reactive power of the photovoltaic grid-connected CHB is calculated; the photovoltaic grid-connected CHB injects the zero-sequence voltage into the power grid, and a control system adopts PWM clamping control to track the magnitude and phase of the zero-sequence voltage. The method can be used for expanding the reactive power exchange capacity of the CHB units and the power grid in the fault state, balancing the current of the power grid after a converter has a fault module, preventing the overmodulation of the CHB units, and facilitating the equalization of the active power and reactive power of each phase of the photovoltaic grid-connected CHB.

Description

technical field [0001] The present invention relates to the field of photovoltaic grid-connected technology, in particular to a reactive power exchange method and system for photovoltaic grid-connected CHB of a faulty module Background technique [0002] In recent years, solar photovoltaic grid-connected power generation technology has been more and more widely used in the field of renewable energy. Today, solar photovoltaic power generation not only provides active power to the grid, but also exchanges reactive power with the grid, such as reactive power compensation, power quality improvement, etc. The cascaded H-bridge (CHB) multilevel converter has become one of the most attractive topologies for large-scale medium-voltage solar photovoltaic power plants, which can be directly connected to the grid. Due to the large number of switches in this converter, the probability of switch failure is high. After a CHB converter fails, its operation can be improved by bypassing the...

AI Technical Summary

Problems solved by technology

A small number of authors have recently proposed different types of zero-sequence injection voltage methods for grid-connected solar PV, however, these papers only discuss the unbalanced active power generation within the module, and do not discuss the operation of CHB and reactive power exchange with the grid when a module fails

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