Study and Design of Different Controllers for Capacitive- and Hybrid-Coupling Grid-Connected Inverters for Power Quality Conditioning and PV Energy Generation

Abstract

For modern smart grid development, the power filters and renewable energy sources (RES) grid connected inverters have been found widespread application. In recent years, many researchers combined the power quality compensation and photovoltaic (PV) power generation together as they have the same grid-connected inverter structure. The capacitive-coupling grid-connected inverter (CGCI) and hybrid-coupling grid-connected inverter (HGCI) are recently proposed to transfer the active power and achieve power quality compensation simultaneously with low DC-link operating voltage. Hysteresis controller is conventionally applied on them because of its simplicity and fast dynamic response. However, it yields a wide and variable switching frequency, thus either generating large output current ripple or increasing the filtering circuit cost. Moreover, it will induce significant steady-state errors, which affect the system performances. This thesis aims to design different controllers for CGCI and HGCI to significantly reduce the output current ripple and steady-state errors, so as to enhance the power quality conditioning and PV energy injection performance. To prove the effectiveness of controllers, simulation platform and an 110V-5kVA three-phase four-wire CGCI and three-phase three-wire HGCI experimental prototype are developed and built. Different controllers are tested and compared to verify their performance about non-active power compensation and active power injection. Key words: Capacitive-coupling grid-connected inverter, power quality conditioning, active power, renewable energy, hybrid grid-connected inverter, deadbeat controller, Multi-Quasi-PR controller, thyristor controlled LC-coupling, PI controller.