A single-stage grid-connected inverter with wide range reactive power compensation using energy storage system (ESS)

This paper presents a single-stage grid-connected inverter with energy storage system (ESS) for small distributed power generation (DG) system application. A reactive power allocation (RPA) strategy is developed so the proposed inverter can provide real and reactive power in wide range. In particular, the ESS can provide not only harmonic compensation but also reactive power to enhance the system stability. An appropriate reactive power allocation coefficient is designed to avoid duty cycle saturation and over modulation in order to maintain good power quality. Furthermore, a control system, including proportional resonant control, capacitor voltage balance control and RPA control, is developed in grid-connected mode. Finally, a 3.5 kW single-stage grid-connected inverter with proposed control strategy is implemented in the laboratory. Both simulation and experimental results are presented to verify the validity of the proposed technology.