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With the rapid development of high-speed and high-power railway system in China, power quality such as the negative sequence current and harmonic current caused by electric locomotives becomes more and more critical. This paper proposes a half-bridge-converter-based railway static power conditioner (RPC) (HBRPC) which consists of two half-bridge converters connected by two capacitors in series. Compared with the traditional RPC, the HBRPC requires only a pair of power switch legs and two capacitors. Under the premise of accomplishing the same function of RPC, the proposed conditioner can reduce half of the power switches, which can make it with lower cost and hardware complexity. A double-loop control is proposed for HBRPC to keep the dc-link voltage stable and achieve the dynamic tracking of the current reference signals, while a balanced voltage control is proposed to eliminate the error of two capacitor voltages and maintain the normal operation of HBRPC. Finally, simulation and experiment results have verified the proposed structure and its control method effectively. [ABSTRACT FROM PUBLISHER]

Two types of pulsed power supply, a modular 12 MJ/25 kV capacitor bank and a 100 MVA flywheel pulsed generator, are under construction for the pulsed high magnetic field facility at the Huazhong University of Science and Technology (HUST) in Wuhan, China. The capacitor bank consists of 11 independent 1 MJ modules with a short circuit current of 40 kA each and 2 independent 0.5 MJ modules for 50 kA each. The bank is used to energize coils for magnetic fields in the 50–80 T range with pulse duration from 15 to 200 ms. The pulsed flywheel-alternator is used to energize a 50 T/100 ms long-pulse magnet via two 12-pulse power converter modules. Each converter module is designed to operate in the 95 to 66 Hz frequency operation range of the generator and can provide a no-load voltage of 4.6 kV and a full-load voltage of 3.4 kV at the rated current of 20 kA. In this paper the design of these two types of power supply is presented. [ABSTRACT FROM AUTHOR]

• Free variables are selected based on mathematical model of hybrid cascaded MTDC. • System security operating range is analyzed to determine the free variables values. • An operation point calculation method for the hybrid cascaded MTDC is proposed. • The hybrid MTDC system operational dispatching and scheduling strategy is proposed. A hybrid cascaded Multi-terminal HVDC (MTDC) system involving both series and parallel-connected converters, which combines the advantages of line commutated converter based (LCC) and voltage source converter based (VSC) HVDC for ultra-high voltage, large-capacity and flexible power transmission, is proposed and is to be implemented in a real project in China. Due to complexity of operational control and difficulty of operational scheduling brought by the hybrid cascaded MTDC system and the lack of prior related research works, this paper establishes the mathematical model of the hybrid cascaded MTDC system and then proposes a system operational dispatching and scheduling strategy, which includes: 1) feasible coordinated operational control strategies investigation; 2) security operating range of the whole hybrid cascaded MTDC system analysis; 3) operating points of the hybrid cascaded MTDC system calculation. Simulations results based on PSCAD/EMTDC are used to validate the proposed system operational dispatching and scheduling strategy. [ABSTRACT FROM AUTHOR]

On the background of the peculiar technology problems with the external insulation of UHV dc equipment in China, caused by high altitude and heavy pollution, this paper presents the pollution flashover performance of full-scale ?800 kV converter station post insulators at actual high altitude area. The tests were carried out according to the solid layer method, and the 50% withstand voltage (U50%) was determined by the up-and-down method. The artificial contamination test results indicated that the shed configuration and the rod diameter had a significant influence on the flashover voltages. Shed parameters of one big and one small alternating shed composite post insulator which had superior dc pollution flashover performance had been recommended. The relationship between U50% and insulation height was approximately linear at actual high altitude area for post insulators. It was found that partial discharges occurred at the top section firstly and partial arcs easily appeared at the parts nearby the connecting fittings during the flashover process. And arc floating phenomenon was significantly serious in actual high altitude area. Furthermore, comparison was made between the U50% values of composite post insulators in fog and in rain. The U50% values in fog of composite post insulators were generally higher than that in rain. Thus, the outdoor insulation design of composite post insulators should primarily consider the U50% value in fog. This work thus provides useful reference for the design, operation and maintenance of UHV dc converter stations outdoor insulators in China. [ABSTRACT FROM PUBLISHER]