Programmable multilevel inverter with optimally tuned controller for photovoltaic connected systems

Abstract

The Multilevel Inverter (MLI) topology has been a trending research topic, due to its vital role in medium and high power application systems. Renewable energy sources such as Photo Voltaic (PV), wind, and fuel cells can be easily interfaced with MLI. To resolve issues related to integration of PV panels and multilevel inverters, this research work proposes a Programmable MLI capable of integrating low voltage power sources and generating higher number of programmable levels using single Direct Current (DC) source input and lower component count. The Programmable MLI is composed of a front end Hybrid Boost Resonant Converter (HBRC) and Resonant Voltage Multiplier Rectifier (RVMR). Phase shift control Pulse Width Modulation (PWM) scheme and Programmable Duty Ratio Adjustment (PDRA) algorithm are implemented in a Fuzzy Logic Controller (FLC) unit for adjusting the duty ratio of these converter circuits to obtain regulated output voltage. The fuzzy tracker provided efficiency around 94% under PV oscillations under uniform irradiance, but suffers from peak oscillations while tracking. The proposed inverter has been simulated and experimentally verified. An experimental model with a 300W PV panel is used to validate functionalities of the design. The simulated model and experimental results provided a better scope for real time integration. Consecutively, an Interval Type-2 Fuzzy Fractional order Proportional Integral Derivative (IT2FO-FPID) Controller has been designed with optimal gain parameters. The IT2FO-FPID is capable of regulating the system faster under dynamic oscillation. This controller exhibits minimal oscillation and settling time. Grasshopper Optimization Algorithm (GOA) and Enhanced Grasshopper Optimization Algorithm (EGOA) are used to optimize the gain parameters of the controller. Among the controllers, EGOA tuned IT2FO-FPID provided a better tracking efficiency of around 98.9%. The performance of the proposed programmable MLI has been evaluated as driver for single phase induction motor. Among the controllers presented in the previous works, the better controller is EGOA-IT2FO-FPID and it is utilized with the motor connected system. Selective Harmonic Elimination (SHE) is implemented for reducing the THD. The controller adjusts the duty ratio of the switches present in the H-bridge. The angles, that selectively eliminate harmonics, are optimally computed using EGOA. The simulation results evaluating the THD and the speed characteristics are observed newline