Low voltage ride through capability enhancement of grid connected PV system by SDBR

Penetration of Photovoltaic (PV) power to the grid is increasing very rapidly. Energy regulatory body is imposing much stricter grid code due to this high penetration of the PV power. Grid connected PV system encounters different types of abnormalities during grid faults. When the fault appears in the grid side, the point of common coupling (PCC) voltage will go very low which will cause the DC link voltage very high for power balancing. This high DC link voltage may damage the inverter. Also, the voltage sag will force the PV system to be disconnected from the grid according to grid code. And shutdown of large PV plant may have adverse effect in power system operation. This study proposes series dynamic braking resistor (SDBR) to counteract the effect of faults in the grid side and hence prevents the voltage sag in grid side. Improving voltage sag by the proposed method will enhance the low voltage ride through (LVRT) capability of the PV plant. The effectiveness of the proposed method is verified by applying the most severe fault (three-phase-to-ground fault). The terminal voltage obtained with proposed protection scheme maintains the grid code, and hence the PV systems need not to be disconnected from the grid during fault.