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Implementation of ZVS Concept in Four Wire Inverter for UPS Fed (Unbalanced) Star Connected Load


R.Senthil Kumarm, Jovitha Jerome


Vol. 12  No. 7  pp. 112-120


A novel method of output voltage control of a 3 phase uninterruptible power supply (UPS) System with four leg inverter is proposed. This paper presents the feedback loop control scheme for a soft switched four wire voltage source inverter with filter for UPS system. The use of a four wire inverter increases the quality of the output whereas the implementation of soft switching technique increases the overall efficiency of the inverter by reducing switching losses. Further, in order to respond to the load variations a feedback loop is constructed with a PI controller to realize closed loop control. 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 four leg inverter produces the three output voltages independently. The ability to deal with voltage imbalance in a 3 phase system is the main feature of three phase four wire inverter. 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 computer simulation. The experimental analysis of the four wire inverter is also discussed in this paper.


Four wire inverter, PLL, Soft Switching, THD, UPS