Transformerless full bridge neutral point clamped inverter topology for renewable energy sources

Abstract

Transformerless inverters are becoming popular, especially in the field of renewable energy systems because of their compactness in size and higher efficiency. However these topologies are suffering from leakage currents and they can be reduced by clamping the neutral point during freewheeling modes. Two types of basic switching cells are introduced to build the proposed topology. They are positive neutral point clamping cell and negative neutral point clamping cell. Using these two cells proposed topology is clearly explained. In this paper unipolar sinusoidal pulse width modulation (UPSPWM) which is already existing and modified unipolar sinusoidal pulse width modulation (MUPSPWM) which is proposed to these topologies for getting an improved result. These two types used for creating switching pulse pattern for all topologies and then obtained results are compared in respect of THD. Existing topologies like OH5 and full bridge dc bypass (FB-DCBP) are also simulated with both PWM techniques and their results are compared to proposed topology in respect of total harmonic distortion (T.H.D) and number of switches. Results showing in this paper are validated by simulating with MATLAB.