A Single-Stage Grid Connected Inverter Topology for Solar PV Systems With Maximum Power Point Tracking

This paper proposes a high performance, single-stage inverter topology for grid connected PV systems. The proposed configuration can not only boost the usually low photovoltaic (PV) array voltage, but can also convert the solar dc power into high quality ac power for feeding into the grid, while tracking the maximum power from the PV array. Total harmonic distortion of the current, fed into the grid, is restricted as per the IEEE-519 standard. The proposed topology has several desirable features such as better utilization of the PV array, higher efficiency, low cost and compact size. Further, due to the very nature of the proposed topology, the PV array appears as a floating source to the grid, thereby enhancing the overall safety of the system. A survey of the existing topologies, suitable for single-stage, grid connected PV applications, is carried out and a detailed comparison with the proposed topology is presented. A complete steady-state analysis, including the design procedure and expressions for peak device stresses, is included. Necessary condition on the modulation index "M" for sinusoidal pulsewidth modulated control of the proposed inverter topology has also been derived for discontinuous conduction mode operation. All the analytical, simulation and experimental results are presented.

I. Introduction

High initial investment and limited life span of a photovoltaic (PV) array makes it necessary for the user to extract maximum power from the PV system. The nonlinear i–v characteristics of the PV array [1] and the rotation and revolution of the earth around the sun, further necessitate the application of maximum power point tracking (MPPT) [2] to the system. in this context, grid connected PV systems have become very popular because they do not need battery back-ups to ensure MPPT. Stand alone systems can also achieve MPPT, but they would need suitable battery back-ups for this purpose.