스코트 변압기 적용 3상 계통의 불평형 전류보상 기법 연구

Abstract

This paper presents a control algorithm using a Scott transformer to solve the imbalance problem in the three-phase system. Due to the imbalance of the three-phase system, the power system has a deterioration in quality. Here, a power compensation system is designed according to the actual driving environment of railway vehicles. The received three-phase AC power is converted into two single-phase power with a phase difference of 90 degrees through the Scott transformer, and the two loads are connected through a back-to-back converter. In order to minimize the power loss in the system, the back-to-back converter adopts a single three-level NPC converter. This compensation system uses the single-phase current on the secondary side of the Scott transformer for control. In order to solve the problem of voltage distortion caused by the notch phenomenon and phase tracking caused by the leakage inductance of the transformer when directly measuring the voltage on the single-phase side, an observer is cited. In order to verify the performance of the proposed current compensation system, simulations and experiments are carried out under the conditions of switching frequency of 600Hz, M-phase 5kW and T-phase 1kW imbalanced load. The experimental results show that the three-phase current unbalance rate after the current compensator is running has dropped from 67.99% to 0.58%, which fully verifies the excellent performance of the current compensator proposed in this paper.