Power quality improvement in Y/Δ electric traction system using a Railway Power Conditioner

Power Quality Conditioners for Railway Traction—a Review

“…This type of conditioner is used for unbalanced loads, reactive power compensation and to maintain the terminal voltage. It can be configured as multilevel [77,81,122,124], single-phase [78,79,121,123,125,126,127] and three-phase [80] UPQC and hence, this type of power quality conditioner can be considered as an A hybrid filter, a combination of shunt active and passive filter is shown in Fig.5. [129].…”

“…Single phase conditioners can be developed in multilevel [122] composing two single phase with DC capacitors. Different kinds of transformers like Scott, Woodbridge and impedance-matching-transformers to connect three phase supply to two phase traction load system are discussed and found that Y/∆ transformers are more effective [125].…”

Comprehensive study on the power rating of a railway power conditioner using thyristor switched capacitor

“…Buchholz and Depenbrock improved this method and labelled it the 'FBD-method' [15]. Referring to [25], a control system based on FBD-method is needed to generate the proper compensating currents for RPC. Moreover, a hysteresis controller and a proportional-integral controller are implemented in RPC control system to track the RPC reference currents properly, and to stabilise the DC-link capacitor voltage, respectively.…”

“…RPC configuration strongly depends on the connection type of traction transformer. Different types of traction transformers have been compared with each other according to transformer utilisation factor (TUF), line utilisation factor and NSC index in [25, 26]. The results showed that the max TUF of the V / V connection would be higher than the Y /Δ and Scott connections (TUF V / V = 100%, TUF Y /Δ = 75.6% and TUF Scott = 92.8%); in addition, TUF is an important consideration for selecting traction transformers, because the power of the locomotives are usually huge; hence, it will decrease the cost to adopt traction transformers with a high TUF [20].…”

“…The results showed that the max TUF of the V / V connection would be higher than the Y /Δ and Scott connections (TUF V / V = 100%, TUF Y /Δ = 75.6% and TUF Scott = 92.8%); in addition, TUF is an important consideration for selecting traction transformers, because the power of the locomotives are usually huge; hence, it will decrease the cost to adopt traction transformers with a high TUF [20]. However, if the NSC was compensated by RPC, and the traction transformer became a symmetrical three‐phase transformer from the utility grid's point, the selecting parameters would change considerably [9, 25]. In this case, the TUF of Scott transformer remained the same (TUF Scott = 92.8%); whereas the TUF of the Y /Δ transformer was improved to 100%, because the Y /Δ transformer is inherently a three‐phase balanced transformer; however, the TUF of the V / V transformer declined to 87%.…”