Multi-topology-Mode Grid-Connected Inverter to Improve Comprehensive Performance of Renewable Energy Source Generation System

The multi-inverter-based configuration is usually adopted in the renewable energy source grid-connected generation system (RES-GGS) to obtain a wide operational range and independent output power control of the renewable energy sources (RESs). The complicated configuration inevitably reduces the European efficiency. This paper proposes a multi-topology-mode inverter suitable for RES-GGS, which possesses five equivalent topology modes. When the output voltage and power of the RESs increase gradually, the system transforms its actual topology mode from the complicated ones to the simpler ones to increase the European efficiency. Furthermore, a system-level control strategy that can achieve the independent generation power control of each RES and the grid current closed-loop control is proposed. By online transforming the system among the five topology modes, the characteristics of wide operational range, independent output power control of each RES and high European efficiency are all achieved. The detailed experimental results verify the feasibility and advantages of the proposed multi-topology-mode grid-connected inverter.

I. Introduction

Due to the challenge of the energy shortage and environmental pollution and because of its advantages of consuming no fossil fuels, infinite reserves, and harmlessness for the environment, the renewable energy source grid-connected generation system (RES-GGS) has attracted more and more attention [1] –[3]. At present, the initial investment cost of the RES-GGS is still high and the competitive edge of the RES-GGS is reduced. Therefore, how to enhance the power extraction ability and increase the utilization rate of the RES is a key issue in the RES-GGS. The solution is helpful to shorten the payback period and the competition of the RES-GGS will be enhanced significantly.