VU limit pre‐assessment for high‐speed railway considering a grid connection scheme

Abstract

Single-phase 25-kV AC traction power supply systems (TPSSs) are widely used in high-speed railways (HSRs), leading to an increasingly prominent problem of voltage unbalance (VU) in the power grid. To fairly regulate the system VU level, implementing VU limit pre-assessment is an urgent need. A grid connection scheme, including traction transformer selection and exchange phase connection (EPC) design, is a vital part of TPSS design that obviously affects the voltage unbalance factor (VUF) of power systems. A uniform mathematical model is established using Thevenin's theorem, which reveals the impact of multiple grid connection schemes on the VU propagation behaviour of a three-phase grid. Afterwards, under the requirements of IEC/TR 61000-3-13, an improved VU limit pre-assessment process is proposed, which correlates mapping between the grid connection scheme and VU limit. The unbalance compensation calculation is given, adopting the allocation limit; furthermore, the optimal design of the grid connection scheme with minimized compensation capacity as an object is presented. The correctness of the model and the rationality of the pre-assessment process are verified by a case study.

Optimal planning of hybrid energy storage systems in traction power supply system with railway power conditioner

“…κ U is the voltage unbalance upper limit specified in the power quality standard. The derivation of negative sequence current is as follows 33 :…”

Energy storage traction power supply system and control strategy for an electrified railway

“…It is assumed that the traction power is set as P L , the powers through the TT and α phase converter of the PFC are set as P T and P α , respectively, and the allowable three-phase unbalance factor u θ and system short-circuit capacity S d are known. According to (2) and (3), the power through the TT should satisfy:…”

“…On the other hand, the high-speed electric multiple units (EMUs) have been widely applied in China's high-speed railway (HSR), which possess the high power factor (PF) and huge traction power. For example, the traction power of CRH380AL has arrived at 20 MW, and the PF is closed to 1 [2,3]). As a result, a large negative sequence (NS) current will be injected into the threephase system, arouses severe challenges for the economy and reliability of TPSS.…”

Voltage Unbalance, Power Factor and Losses Optimization in Electrified Railways Using an Electronic Balancer

“…The adoption of STATCOM solutions to mitigate these issues has been reviewed in [25]. In [26] is presented a three-stage pre-assessment process taking into consideration the grid connection scheme, towards an evaluation for the need of a compensator in the TPSS. In [27] is studied the integration of wind farms and the HSR power system, when both geographically coexist in weak power grids of remote areas.…”