Low Voltage Ride Through (LVRT) Strategies for Single Phase Grid Connected PV Fed Cascaded Multilevel Inverter

In this paper, cascaded multilevel inverter based PV (CMIPV) system performance is investigated under perturbing voltage condition at PCC, viz, voltage sag by robust multi mode control, demonstrating low voltage ride through (LVRT) capability. The decoupled d-q based methodology provides an efficient and independent control of individual H-bridges for active/reactive power. The controller is design to regulate the individual DC link voltages according to the voltage dictated by maximum power point (MPP) algorithm or guided by grid codes keeping the capacity of the inverter system fixed. As per the condition of PCC voltage the controller displaces the operating point from MPP to other lower power to accommodate reactive power as per grid code. The performance of the proposed configuration and control is investigated both through MATLAB simulation and experimentation.