Circulating-current restraining method for three-phase inverter in droop control process

Abstract

The invention relates to a circulating-current restraining method for a three-phase inverter in the droop control process, in particular to a circulating-current restraining method when the three-phase inverter adopts droop control for parallel operation. The circulating-current restraining method includes the following steps that (1) the type of the required equivalent impedance difference is determined according to the difference of adopted droop control equations; (2) the equivalent resistance difference or the equivalent reactance difference which enables the circulating current of the inverter to be zero is calculated according to a relationship between the equivalent impedance difference and the circulating current; and (3) the equivalent impedance difference which enables the inverter circulating current to be zero is used as virtual impedance to be introduced into a system to achieve restraint of the circulating current. The circulating-current restraining method solves the problems that in a traditional virtual impedance introduction method, the impedance is difficult to measure in the parallel circulating-current restraining process of the inverter and the restraining capability is limited, real-time adjustment of the virtual impedance is realized, and the restraint of the circulating current under different working conditions can be realized.

Description

technical field [0001] The invention relates to the fields of power conversion devices and distributed power sources, in particular to a method for suppressing circulating current of three-phase inverters during parallel operation. Background technique [0002] A microgrid usually contains multiple distributed power sources, and the spatial distribution of distributed power sources is decentralized, and the line impedance from each inverter to the load is usually inconsistent, resulting in circulating currents between the inverters, making the output of each inverter Unequal distribution of power. When the circulating current is severe, it may even cause the inverter to limit the protection and stop running, which will cause a chain reaction. Therefore, the inverter parallel system is required to have a good current sharing effect. [0003] Droop control controls the inverter by simulating the frequency and amplitude droop characteristics of the external characteristics of ...

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Problems solved by technology

[0005] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a three-phase inverter in the droop control process that can solve the problem that the traditional virtual impedance has limited ability to suppress the circulating current in the parallel operation of the inverter. Circulation Suppression Method

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