Indian Journal of Science and Technology

Abstract

Grid interfacing of multi-megawatt photovoltaic inverters is getting a closer attention in recent past. It is always a hard and challenging task for the engineers as there are certain priorities to be taken while interfacingPV cells to grid without which there will bean unsatisfactory operation of the system will taken. Somehow for high power and medium voltage grid invertersthe priorities like IEEE and IEC standards, satisfaction of grid codes and switching losses are to be strictly considered. Mitigation of switching losses is the active area of research for the PV systems. To meet such requirements weare using the traditional and conventional modulation strategy like SHE (Selective Harmonic Elimination). This paper focus on the reduction of switching losses with the help of new implementation technique for SHE that uses the third harmonics to have the switching angles over 90°, which also increases the modulation index. The Selective harmonic elimination strategy can allow the grid connected inverters to operate using a switching frequency less than 1 KHz while it is still able to provide satisfactory operation like simplicity in operation, independent control of active and reactive powers which is not possible in other cases. To validate potential benefits of SHE, it is compared with THI PWM which is controlled with an operating frequency of 2 KHz.
Keywords: Grid Interfaced PV Inverters, Pulse Width Modulations (PWMs), Selective Harmonic Elimination (SHE), Switching Losses, THI PWM (Third harmonic injection PWM)