Research On The Zero Sequence Current And The Loss Of The Three-level Inverter In UPS

People’s demand for reliable, high-quality power is dramatically increasing with therapid development of industrial, medical, public services and other industries,.High-capacity, high power density studies inverter parallel system became the focus ofattention. With a small footprint, high energy conversion efficiency, Modular UPSparallel inverter has improved system reliability and redundancy, made system upgradeseasier and expanded characteristics. Since the circuit has a three-level voltage stress, highoverall efficiency, the output current ripple value has greater advantages in high powerdensity power supplies. In this paper, three-level suppression and loss issues were exploredfor the parallel system circulation.Based on three-level inverter circuit high power density, modular inverter parallelsystem. Firstly, widely used topology diode clamp three-level inverter circuit will beintroduced, working principle and modulation, which focuses on the modulation of theprinciple of the three-level space vector (SVPWM) and zero-sequence by superimposingPWM carrier component method of implementation.Secondly, the system analyzes the causes of the parallel circulation of zero sequenceestablished circulation of zero sequence equivalent circuit model, and zero-sequencecirculation in accordance with its causes are classified. Then for the zero-sequenceCirculation different causes, and proposed the corresponding suppression methods.Circulation for the high frequency of zero-sequence based primarily on SVPWM vectormodulation small role of common-mode voltage, an improved19-vector method to reducethe zero-sequence excitation, and gives two methods were compared derivative.Containing power devices loss and loss of three-level circuit filters were mathematicalmodeling and computational analysis in this article, comparing the loss of use of the deviceparameters loss and mathematical analysis was obtained to verify its validity, and thethree-level circuit with two-level circuit losses comparative analysis demonstrates theadvantages of three-level circuits to improve system efficiency and its shortcomings.