A Transformerless Photovoltaic System Employing a Cubic Cell Boost Converter for Low Voltage Application

Abstract

A photovoltaic (PV) system is commonly used to satisfy the power demand of the utility. This paper investigates the utilization of a high voltage gain Cubic Cell Boost Converter (CCBC) in a transformerless photovoltaic (PV) system for low voltage applications. The proposed system is a combination of a CCBC and a three-phase inverter creating a two-stage three-phase PV system. The CCBC is linked with the low-scale PV sources to step up its input DC voltage and maintain a constant DC bus voltage by employing the Perturb and Observe (P&O) Maximum Power Point Tracking (MPPT) control algorithm. The DC bus is further connected to an LCL filter based three-phase inverter using a synchronous reference frame (dq) control scheme to power the three-phase utility. The proposed combination is validated by simulating in MATLAB/ SIMULINK environment for a 5.5 kW PV source and achieved an efficiency of 91% with 1.91% of inverter Total Harmonic Distortion (THD) at unity power factor. In the proposed system, CCBC with P&O MPPT control provides a high step-up DC bus voltage with less input current ripple and output voltage ripple and maintains a constant DC bus under variable solar irradiance. This work does not account for the common leakage current that is often produced in a transformerless PV system.