Medium-Voltage AC Static Switch Solution to Feed Neutral Section in a High-Speed Railway System

Abstract

A high-speed train (HST) is a single-phase load supplied by a three-phase AC grid. The HST produces unbalanced three-line currents affecting the power quality of the grid. To balance the asymmetries on average, railway feeding sections are supplied that rotate the three phases of the grid. An electric isolation segment, called the neutral section (NS), between different sections is necessary. The HST must pass through this 1.6 km NS without power supply. In this paper, a medium-voltage AC static switch solution to feed the high-speed train in the NS is proposed. Thyristor technology is selected to design the 25 KVAC static switch. A medium-voltage power electronics procedure design is proposed to ensure proper operation in the final application. An NS operation is analyzed to identify impacts within the electric system and solution requirements are developed. Then, a low-scale prototype is used to experimentally validate the solution based on thyristor technology and the medium-voltage AC static switch is designed. Limitations on power and voltage at the Mondragon University Medium-Voltage Laboratory do not allow testing of the AC static switch at nominal conditions. A partial test procedure to test sections of the AC static switch is proposed and applied to validate the solution. Finally, experimental results for the Cordoba–Malaga (Spain) high-speed railway in real conditions with an HST crossing the NS at 300 km/h are shown.

An Optimized Regulation Scheme of Improving the Effective Utilization of the Regenerative Braking Energy of the Whole Railway Line

“…When the regenerative braking power in a certain power supply sector needs to be transferred and the adjacent power supply sectors on both sides are in the state of power consumption, the utilization rate of the RBE can be improved regardless of which side the RBE is transmitted to. However, the unbalanced three-phase current in the TS input side would cause a great threat to the safe operation of the utility grid [12,30,31]. The main reason is the power difference between two power supply sectors in the same TS.…”

“…, 2n−1), the active power of the right side of the ETC l is −ηp l ; when p l < 0, the active power of the right side of the ETC l is − p l /η. However, the unbalanced three-phase current in the TS input side would cause a great threat to the safe operation of the utility grid [12,30,31]. The main reason is the power difference between two power supply sectors in the same TS.…”

Special Issue “Intelligent Control in Energy Systems”

“…A static switch in order to feed a High-Speed Train (HST) through the Neutral Section (NS) was proposed by Canales, Aizpuru, Iraola et al [17]. An NS operation was analyzed to identify impacts within the electric system and solution requirements were developed.…”

Integrated optimisation model for neutral section location planning and energy‐efficient train control in electrified railways

“…Neutral sections (NSs), also referred to as the ‘phase separation sections’ or ‘dead zone’, are the electrical isolation segment between sections. In electrified railways, each phase feeds the catenary for about 30–40 km and NS between each phase is important for isolation and balancing load voltage between phases [3].…”

“… Typical schematic diagram of electrical railway power supply system with NSs. Each phase feeds the catenary for a distance of 20–60 km and the length of NS may vary ranging from a few hundreds metres to more than one thousand metres depending on different systems [3, 4]. NS provides phase separations between different sections …”