A New Highly Efficient Three-Phase Transformer-Less Hbzvr for Grid Operating System.

Abstract

Single-phase transformer less inverter is widely used in low-power grid-connected systems due to its small size, high efficiency and low cost. The galvanic isolation can be achieved via dc-decoupling or ac-decoupling, for isolation on the dc- or ac-side of the inverter, respectively. It has been shown that the latter provides lower losses due to the reduced switch count in conduction path. Common-mode voltage (CMV) appears in motor drives due to working principles of the pulse width modulation (PWM) inverters. This voltage is the main source of many unwanted problems in AC drive systems. In this Project, several recently proposed transformers less inverters with different galvanic isolation methods and CMV clamping technique are analyzed and compared. A simple modified H-bridge zero-voltage state rectifier is also proposed, to combine the benefits of the low-loss ac-decoupling method and the complete leakage current elimination of the CMV clamping method. The performances of different topologies, in terms of CMV, leakage current, total harmonic distortion, losses and efficiencies are compared. The proposed concept is further connected to three-phase system and is implemented using HBZVR concept. A safety issue is the main concern for the transformer less systems due to high leakage current. Without galvanic isolation, a direct path can be formed for the leakage current to flow from the source to the grid by In extension the proposed concept can be implemented for three-phase configuration by using MATLAB/SIMULATION software.