An optimal and efficient PV system using two 2-level cascaded 3-level inverter for Centrifugal pump

Abstract

In this paper a three-phase single-stage integrated multilevel inverter PhotoVoltaic (PV) fed Induction Motor (IM) pump drive system is presented. The proposed system uses two 2-level cascaded H-bridge inverters for the 3-level output which is fed from two independent PV sources. Usage of cascaded inverter configuration eliminates the problem of neutral point fluctuations, does not require fast recovery neutral clamping diodes & high value capacitor when compared with conventional multilevel inverter configurations like 3-level Neutral-Point Clamped [NPC] inverter and Flying Capacitor (FC) inverter. Further, it requires only two isolated DC power sources in comparison with 3-level H-bridge configuration which demands three sources. The given system uses both the PV sources efficiently which may help in optimal sizing of PV source with respect motor load requirements. Further, for optimal utilization of PV source a Maximum Power Point Tracking [MPPT] algorithm is also employed. This paper also gives a detailed yet simple mathematical model for the cascaded inverter and its integration with PV module for simulation in Matlab-Simulink Also a simple Sinusoidal Pulse Width Modulation [SPWM] technique is used for switching of the inverter. The proposed system has the advantages of simple V/f control integrated with MPPT algorithm. V/f control retains maximum torque capability of the motor which further helps in optimum utilization of the PV-source and the IM. The simulation results of the proposed system under various environmental conditions has been discussed and presented in the paper.