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With the rapid development of high‐speed railway, the auto‐transformer traction network (ATN) is also expanding. However, due to the improved performance of electric multiple units (EMUs) and the non‐linear relationship between impedance and ground fault distance, distance protection has limited coverage and cannot accurately locate the fault distance by measuring impedance. This paper presents a model of the ATN considering the presence of EMUs, which effectively demonstrates the characteristics of current distribution under the ground faults. Furthermore, a ground fault identification method based on multi‐terminal currents is proposed to enhance the accuracy of fault identification and differentiate faults and EMUs. The mapping relationship between current distribution and fault location is derived, and an accurate fault location method is proposed. Compared to existing methods, this method is not affected by EMUs and AT parameters. The fault identification and location scheme for ATN employs multi‐terminal synchronous information. Finally, through simulation and experimental setups, case studies have been conducted to verify the accuracy and robustness of the proposed method in various fault scenarios. Certainly, this research has significant application prospects in fault analysis and detection for HSR. [ABSTRACT FROM AUTHOR]

To recycle regenerative braking energy (RBE) while reducing demand charge in electrified railway, a co‐phase power supply system with hybrid energy storage system (HESS) is implemented. However, the dynamical degradation characteristic of battery is necessary to be considered in optimal operation of HESS. A bi‐level model considering battery degradation is proposed to obtain optimal sizing and operation of HESS. The proposed model includes a novel real‐time energy management strategy (EMS) using average power as thresholds, to effectively reduce the demand charge and energy consumption charge. Thresholds are dynamically adjusted with the consideration of battery capacity degradation. A real measured load profile from Beijing‐Shanghai high speed railway is studied. The results demonstrate that the proposed EMS performs better than previous EMS in cost saving. The dynamically adjusted thresholds of EMS are proved to be essential under the consideration of battery degradation. With the optimal sizing of the HESS, the traction substation can achieve 8.69% annual saving of demand charge and recycle 52.33% of the RBE. The results also show that a traction substation equipped with the HESS yields higher economic benefit than the energy storage systems equipped with only a battery or a supercapacitor. [ABSTRACT FROM AUTHOR]

The characteristics of traction network (TN) of the three‐phase 3‐kV traction power supply system (TPSS) are: three‐phase conductors are flat layout (layout‐1, layout‐2); the material and cross‐section of conductors are ferromagnetic and irregular, respectively. So the phase impedance matrix (PIM) is unbalanced and the closed‐form formula for conductor impedance is hard to get. To address these issues, firstly, the PIM is derived, and the cause of unbalance is revealed. From the perspective of structure optimization, a new flat layout (layout‐3) and an equilateral triangle layout (layout‐4) is proposed. Then, to calculate the wideband frequency self‐ and mutual impedances of the special phase conductors, a frequency‐ and current‐dependent closed‐form formula based on 4‐parameters equivalent tubular conductor (ETC) model is proposed. Furthermore, an equivalent TN circuit model at 50 Hz is established to calculate the receiving‐end voltage and its negative sequence voltage unbalance factor (NSVUF). Finally, using these two indexes, the performances of the layout‐1 to 4 are evaluated and compared. The results show that the conductor spacing and power supply frequency affect the two indexes much while the dimension of the power supply rail (PSR) not; layout‐4 can completely balance the receiving‐end voltage and improve its magnitude which can enhance the power supply capability. [ABSTRACT FROM AUTHOR]

With the large‐scale increasing demand for passenger transportation, the alternating current (AC) 25 kV traction power supply system (TPSS) of electrified railway is introduced into the construction of urban rail transit in China instead of the direct current (DC) TPSS. In order to suppress the negative sequence current and cancel the neutral section at the exit of traction substation of the AC TPSS, a novel AC integrated power supply system (IPSS) of the urban rail transit based on single‐phase static var generator (SVG) is proposed, which the capacity of SVGs can be further reduced. The topology of the novel AC IPSS is introduced. By defining the constraint factors of negative sequence current and reactive power compensated, the comprehensive compensation model of negative sequence current and reactive power of the novel system is established based on the corresponding standards, which the full compensation and satisfactory compensation can be achieved. The method of determining the compensation scheme and the control strategy are proposed. Taking the actual data as an example, the effectiveness of the compensation scheme is proved. In addition, the correctness of the control strategy proposed is proved by simulation and experiment. [ABSTRACT FROM AUTHOR]

Cascaded H‐bridge inverter (CHBI) is widely used in the industry application for its outstanding features. However, CHBI needs a large number of isolated DC sources. If some of the DC sources are out of work, the DC voltage cannot maintain the desired value and even decreases to zero, thus degrading the quality of the output voltage of the CHBI. Thus, a soft‐switching modulation strategy based on the carrier phase shift SPWM is proposed in this paper to cope with the DC source failure. The strategy is proposed to achieve two goals: 1) one is to adjust the DC voltage of faulty cells back to the normal; 2) the other one is to make the pulse width modulation (PWM) pulses of each cell change without cell voltage level‐skip. The correction and efficiency are verified by a prototype of three‐cell CHBI built in the laboratory. [ABSTRACT FROM AUTHOR]

An advanced combined co‐phase traction power supply system is proposed by combining a single‐phase traction transformer and an active power flow controller (PFC) in an electrified railway. In the new system, the power quality problems caused by single‐phase traction load are solved in the grid side and continuous power can be provided to electric trains without neutral sections in the traction side. The mathematic model of the new system is built by power transformation analysis. The compensation currents of the PFC are calculated based on the power balance principle. According to the power quality standard in China, the optimised partial compensation algorithm is presented to replace the existing full compensation one. Moreover, the capacity of the PFC adopting the proposed algorithm is much less than those in the previous studies with the same outcome. The validity of the compensation algorithm and the control method are demonstrated by the simulation results and the effectiveness of the proposed system is verified by the case studies. [ABSTRACT FROM AUTHOR]