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The railway power conditioner-based energy storage system (RPC-based ESS) is a promising technology to improve the regenerative braking energy (RBE) utilization and power quality of ac direct-fed (25 kV) and AT-fed (2 × 25 kV) railway power systems. However, despite its benefits from the technical perspective, economic viability must be concerned in industrial applications. The capacity is one of the critical issues affecting ESS performance in technical and economic aspects. Therefore, this paper presents a comprehensive approach to designing the capacity for the RPC-based ESS by considering multiple objectives, including the RBE utilization rate, power quality standard, and net lifetime benefit. The proposed approach develops a technical-economic model for the RPC-based ESS based on variables such as the system capacity for RBE utilization and power quality improvement, lifetime cost, and electric charge-based benefits. Moreover, the master-slave control strategy is employed to control the RPC-based ESS to implement the capacity design objectives. Finally, the correctness and effectiveness of the proposed method are validated by sufficient tests based on field load data of a Chinese traction substation. [ABSTRACT FROM AUTHOR]

The hybrid dc circuit breaker (HDCCB) is one of the most promising solutions for the dc interruption. But the power electronics-based load commutation switch (LCS) in the main current path causes the high on-state loss and cost, which inhibits the application of the HDCCB. In this paper, a novel hybrid dc circuit breaker is proposed, in which the vacuum interrupter with the external transverse magnetic field (ETMF) is designed to improve the arc voltage and thus enhance the current commutation to power electronics. The ETMF-based vacuum interrupter achieves the fast current commutation instead of the LCS, which realizes the low on-state loss and cost while preserving the short commutation and interruption time. The arc voltage characteristic with ETMF is analyzed, and the influence of the different factors on the commutation time and di/dt before current zero are investigated in detail. Based on the calculation results, a 10 kV dc breaker prototype based on the proposed topology is developed with the breaking current of 15.5 kA. Finally, the application of the proposed scheme in HVdc grids is discussed. [ABSTRACT FROM AUTHOR]