Design of a phase synchronous inverter for micro-grid systems

Abstract

Nowadays, micro-grid power system is becoming popular for utilizing renewable energy. Generally, electronic inverter and switching system are used to convert the source’s DC supply into the AC supply for the micro-grid line. However, the converted AC supply suffers many problems such as, poor quality of waveform, synchronization problem, high unexpected voltage, etc. The power quality is a significant concern in all sectors that are utilizing electrical power. Therefore, the challenges are to make the AC waveform free from higher harmonic distortion and synchronized with the grid line frequency to improve the power quality and efficiency of the inverter. A three phase, phase synchronous inverter (PSI) circuit has been designed for the micro-grid system. Lowpass LC filters are utilized to reduce the higher harmonic in both input and output sides in the design. Switching and logic networks have generated the pulse width modulation (PWM) signal and a zero crossing sampling is used to precisely synchronize with grid line frequency. A balanced resistive load of star configuration (RL = 40 Ω), and also the input DC voltage ± 35V are considered in this design. The overall conversion efficiency of the PSI is 96.1% and phase synchronization error for each phase is about 0.50 degrees. The results show that the design has better performance and can be utilized efficiently in the micro-grid system.