Lasantha B. Perera

Multi-level current reinjection in double-bridge self-commutated current source conversion

A new self-commutated current source converter is proposed, based on the reinjection of multi-level dc current pulses via a GTO-switched multi-tapped interphase reactor. The ideal reinjection waveform for complete elimination of the harmonic content of the ac system side current is derived and a practical approximation proposed to increase the pulse number of the double-bridge converter to any multiple of twelve. A 48-pulse configuration is analyzed in detail to show the new concept effectiveness on both the ac and dc sides of the converter.

A Novel Load Transfer Scheme for Peak Load Management in Rural Areas

This paper proposes a novel peak load management scheme for rural areas. The scheme transfers certain customers onto local nonembedded generators during peak load periods to alleviate network under voltage problems. This paper develops and presents this system by way of a case study in Central Queensland, Australia. A methodology is presented for determining the best location for the nonembedded generators as well as the number of generators required to alleviate network problems. A control algorithm to transfer and reconnect customers is developed to ensure that the network voltage profile remains within specification under all plausible load conditions. Finally, simulations are presented to show the performance of the system over a typical maximum daily load profile with large stochastic load variations.

Application of the DC-ripple reinjection concept to forced-commutated conversion

A DC-ripple reinjection concept, described in the literature with reference to the line-commutated current source converter, is applied in this paper to the self-commutated current source converter. This is achieved by means of a reinjection converter fed, via a single-phase transformer, from the triple frequency ripple signal. It is shown that the three-phase bridge can be made to operate effectively at any multiple of the six-pulse number and, thus, presents an effective alternative to the use of AC and DC side filters

Harmonic reduction in the double bridge parallel converter by multi-level dc-voltage reinjection

A new double bridge parallel, voltage source converter is proposed, based on reinjection of dc voltage via the neutral point of the standard 12-pulse converter. The ideal reinjection waveform for complete elimination of harmonic content is derived and a practical approximation is proposed, which converts standard 12-pulse into a 60-pulse configuration, which meets strictest voltage and current harmonic standards without the assistance of filters or PWM.

Insulation coordination study for a 50 kV traction feeder station

The heavy haul rail network in Queensland Australia generally adopts a lightning impulse withstand voltage rating of 250 kV for the switchgear and autotransformers within its 50 kV ac traction feeder stations. The aging switchgear across a number of feeder stations in this network are undergoing upgrade and the rail network operator is considering the possibility of using 200 kV rating for the upgraded switchgear. This paper investigates the lightning over-voltages that could occur at the feeder stations under review. Fast front transient models of the feeder stations and the associated traction corridors are developed in PSCAD/EMTDC software. Simulations are conducted to evaluate the likely over-voltages under various scenarios and the results are presented. Finally, the required lightning impulse withstand voltage rating for the switchgear is determined based on the simulation results.