Mitigation of Lower Order Harmonics in a Grid Connected Single Phase Pv-Inverter by Fuzzy Controller

Abstract

Generally the Power circuit topology of the 1 − φ PV system will be a good choice for low-rated PV inverters of rating less than a kilowatt. But the disadvantage would be the relatively larger size of the interface transformer compared to topologies with a high-frequency link transformer. This system will not have any lower order harmonics in the ideal case. However, some factors result in lower order harmonics in the system such as on-state voltage drops on the switches, and the distortion in the grid voltage itself etc. This dc injection into the transformer primary will result in even harmonics being drawn from the grid, again contributing to a lower power quality.

In this project, a simple single-phase grid-connected photovoltaic (PV) inverter topology consisting of a boost section, a low-voltage single-phase inverter with an inductive filter, and a step-up transformer interfacing the grid is considered. A novel design of inverter current control that mitigates lower order harmonics is presented in this project. An adaptive harmonic compensation technique and its design are proposed for the lower order harmonic compensation The proposed method uses an LMS adaptive filter to estimate a particular harmonic in the grid current that needs to be attenuated. The estimated current is converted into an equivalent voltage reference using a proportional controller and added to the inverter voltage reference. To avoid dc biasing of the transformer, a novel PRI controller has been proposed and its design has been presented.