Power quality improvement in grid connected system using four leg VSI

This paper suggests a new method that consists of a four leg inverter that is capable of simultaneously compensating problems like power factor, current imbalance and current harmonics, and also of injecting the energy generated by renewable energy power sources. The fourth leg of inverter is used to compensate the neutral current of load. The grid interfacing inverter can thus be utilized as: 1) power converter to inject power generated from RES to the grid, and 2) shunt APF to compensate current unbalance, load current harmonics and load reactive power demand. The inverter is actively controlled in such a way that it draws/supplies fundamental active power from/to the grid. All of these functions may be accomplished either individually or simultaneously. This new control concept is demonstrated with extensive MATLAB/Simulink simulation studies.