Grid-connected PV inverter with harmonic compensation

Abstract

Grid-Connected Photovoltaic (PV) Inverter systems have become a very attractive means of power generation and the number of these systems are always increasing. Therefore it is important to limit the harmonics generated by these inverters to minimise adverse effects on the grid power quality. The design of these inverters should follow harmonic limits set by IEEE and European IEC standards which suggest limits for the current total harmonic distortion (THO) factor and also for the magnitude of each harmonic. The aim of this research was to test different current controllers and apply harmonic compensation to obtain an inverter output current as clean from harmonics as much as possible. A 3kW single-phase grid-connected PV inverter was designed and built for this work. The tests using the single-phase grid-connected inverter were divided into three groups. Firstly, two different current controllers, namely, Proportional Integral (PI) and Proportional Resonant (PR) current controllers were designed, tested and compared. Secondly, the harmonics generated from the inverter itself due to the switching devices' non-linearities were investigated, and novel compensation techniques based on the current flowing through the switching devices were formulated and tested. Finally, selective harmonic compensators which act on specific current harmonics were designed and tested. The techniques implemented obtained excellent results which made the inverter compliant to the harmonic limits set by the IEEE and IEC standards.