Smart Control Strategy for Conversion Efficiency Enhancement of Parallel Inverters at Light Loads

Abstract

The limited capacity of a single inverter has encouraged the usage of parallel inverters for the interconnection of renewable energy generation system. The current-sharing control is one of the commonly used operating strategies for parallel inverters; however, the conversion efficiency using conventional current sharing is low at light loads. Therefore, a smart control strategy for conversion efficiency enhancement of parallel inverters is proposed in this paper. The proposed control strategy is based on the conversion efficiency curve of a single inverter, where a particle swarm optimization based algorithm is utilized to find the optimal conversion efficiency of parallel inverters. Integration of the proposed control strategy into a photovoltaic generation system (PVGS) with a rated output power of 20 kW interconnected by ten inverters with rated output powers of 2 kW is simulated in this paper. Simulation results demonstrate that the proposed smart control strategy can effectively enhance the conversion efficiency of parallel inverters at light loads and increase the electrical energy output of PVGSs. A fully digitally controlled single-phase inverter with a rated output voltage of 220 V and a rated output power of 2 kW is also implemented in this paper. Two implemented inverters are used to validate the performance of the proposed smart control strategy for parallel inverters. Experimental results show that the proposed control strategy can enhance the conversion efficiency of parallel inverters at light loads.