Research On Cophase Power Supply Technology Based On V Connection Transformer

Unbalanced three phases, reactive and harmonics are the characteristics of traction power supply system because of single phase AC load. Phase rotation of traction transformers are set to reduce influence of unbalanced three phases, which causes different voltages of each supply section. Neutral sections are necessary, but are the weak link of supply, and limit locomotive current got smooth and continuous, restrict improvement of railway high speed and over loading. Cophase power supply of substation doesn't need phase rotation and neutral sections. In this paper, V connection transformers are chosen;cophase power supply systems based on active filter and V connection are studied. By controlling filter with real time detecting methods balances three phases, filter reactive and harmonic currents.Different structures of cophase supply are designed due to booster transformer (BT) supply (or direct supply), and auto transformer (AT) supply. One structure of using V/v connection and three phase three leg converter under direct or BT supply, one structure of using two single phase converter and V/x connection under AT supply are both researched and simulated detailed. Balance transforms are discussed;power relations, capacity and capacity availability of system are analyzed;methods on detecting reference currents and controlling filters are researched.These two proposed systems are modeled and simulated under MATLAB/SIMULINK. Simulation results show that current waveforms of electric power system are symmetric and pure sine curve, reactive and harmonic are compensated. Balance transforms, detecting methods and proposed cophase power supply are verified to be true and feasible.