Analysis of Three Phase Four Wire Inverter for UPS Fed Unbalanced Star Connected Load

A Three phase inverter with a neutral connection i.e., three phase four wire inverter is proposed. The UPS system is fed by three phase four wire inverter and the load neutral point voltage is low to meet the requirement of the system. The four leg inverters effectively provide the neutral connection in three phase four wire system. They are used in many applications to handle the neutral current caused by the unbalanced and non-linear load. The unbalanced load becomes non-linear where the neutral of the loads are accessible. The four leg inverter produces the three output voltages independently with one additional leg. The main feature of a three phase inverter with an additional neutral leg is its ability to deal with load unbalance in a system. The goal of the three phase four leg inverter is to maintain the desired sinusoidal output voltage waveform for all loading conditions and transients. The neutral connection is present to handle the ground current due to unbalanced loads. The feasibility of the proposed modulation technique is verified by Matlab/Simulink.