Parallel inverters control strategy based on adaptive virtual impedance

Abstract

In the low-voltage microgrid, the connection lines between parallel inverters are different due to the different length and loss, and the active power of the parallel inverters cannot be evenly distributed under the conventional droop control. Aiming at this problem, an adaptive control strategy based on virtual impedance was proposed. Firstly, based on the inverter power transmission characteristics and the resistive droop control equation, the reason of the uneven power distribution of parallel inverters when the line was resistive was analyzed. Then, based on the traditional fixed virtual impedance, the virtual impedance was constructed by introducing the output power difference of the parallel inverters, and the line impedance difference was compensated adaptively, so that the power sharing can be realized without obtaining the local line impedance parameters. Finally, the simulation model of parallel inverters system was established on the MATLAB/Simulink simulation platform for verification and analysis. The results show that the proposed method can effectively realize the sharing of active and reactive power among inverters, and is also suitable for different local loads. The control strategy based on adaptive virtual impedance improves the level of power sharing among parallel inverters, which provides some reference for the optimal design of power control of parallel inverters in low-voltage microgrid.

Keywords

• power electronic technology; adaptive virtual impedance; droop control; parallel inverters; power sharing; low-voltage microgrid