A Phase-shifter for Regulating Circulating Power Flow in a Parallel-feeding AC Traction Power System

Abstract

-A parallel-feeding AC traction power system increases the power supply capacity and decreases voltage fluctuations, but the circulating power flow caused by the phase difference between the traction substations prevents the system from being widely used. A circuit analysis shows that the circulating power flow increases almost linearly as the phase difference increases, which adds extra load to the system and results in increased power dissipation and load unbalance. In this paper, we suggest a phase shifter for the parallel-feeding AC traction power system. The phase shifter regulates the phase difference and the circulating power flow by injecting quadrature voltage which can be obtained directly from the Scott-connection transformer in the traction substation. A case study involving the phase shifter applied to the traction power system of a Korean high-speed rail system shows that a three-level phase shifter can prevent circulating power flow while the phase difference between substations increases up to 12 degrees, mitigate the load unbalance, and reduce power dissipation.

Compensation of negative sequence for a novel AC integrated power supply system of urban rail transit

“…The value of TPVU can be calculated by Equation (19) under the premise of three-phase symmetrical external power supply [31]. According to Equations ( 8) and (19), Equation ( 20) can be obtained.…”

“…As is shown in Figure 2, UA , UB and UC are the three-phase voltage of the equivalent power supply system, and UA1 , UB1 and UC1 are the three-phase voltage at PCC, and Zs is the equivalent impedance of the system. The value of TPVU can be calculated by Equation (19) under the premise of three-phase symmetrical external power supply [31]. According to Equations ( 8) and (19), Equation ( 20) can be obtained.…”

“…Germany and other countries adopt the converter method to realize the interconnected co‐phase power supply, which can both solve the problem of negative sequence and neutral section, but the higher cost limits its applications [5]. Parallel bilateral power supply is mainly used by Russia to eliminate the neutral section between the substations, but the negative sequence problem caused by the train has not been solved [19]. At the same time, there is extra power flow in the TPSS, which will lead to the increase of electricity metering [5].…”

Vulnerability of high-speed rail grid-connected system on branch potential energy transfer entropy

“…High-speed rail load will pose a serious threat to the security of the power equipment because of its nonlinear, intermittent and impulsive characteristics [1,2]. The problem will be particularly prominent in the gridconnected system of Sichuan-Tibet railway, which plans to adopt the bilateral power supply mode [3,4]. And the group traction substations will be connected to the power system to deal with the problem of the long and steep slopes in Sichuan-Tibet railway, which will undoubtedly increase the capacity and fluctuation of the single-point load.…”