Power Quality Solutions for Light Rail Public Transportation Systems Fed by Medium-Voltage Underground Cables

In this paper, the combination of a thyristor-switched shunt reactor and a current source converter-based active power filter has been proposed for mitigation of power quality (PQ) problems of Light Rail public Transportation Systems (LRTSs) fed by long medium-voltage underground cables. A case study has been carried out on a typical LRTS to assess the performance of the proposed solution for both capacitive reactive power compensation of underground cables and harmonic filtering of 12-pulse catenary rectifiers. It has been shown by extensive field tests carried out that this solution meets the requirements satisfactorily, thus constituting a complete solution to the PQ problems of LRTS. Conventional PQ solutions have been also assessed, and the corresponding theoretical results are given in comparison with the proposed system

Full-Scale Physical Simulator of All SiC Traction Motor Drive With Onboard Supercapacitor ESS for Light-Rail Public Transportation

This article deals with the design and laboratory implementation of a full-scale physical simulator of an all-silicon carbide (SiC) traction motor drive for light-rail transit systems (LRTS) with onboard supercapacitor energy storage system (ESS). It consists of a pulsewidth modulation (PWM) rectifier representing the 750 V dc catenary line, a three-phase two-level PWM traction inverter to drive a three-phase squirrel-cage traction motor, a flywheel coupled to the motor shaft to represent the dynamic behavior of the transportation vehicle, a loading generator connected to the grid via a dc-link converter with active front-end, and a supercapacitor ESS containing a bidirectional dc-dc converter supplied from the common dc link. The PWM rectifier, a traction inverter, and a bidirectional dc-dc converter are all SiC power MOSFET-based converters for high efficiency and high power density. A physical simulator is a valuable tool in the design and testing of all SiC converters. It is equipped with software programs for a catenary model, rail track model, and vehicle model, and permits the performance verification of various control, modulation, and energy-saving strategies. The physical simulator system developed in this article also allows the performance verification of a vehicle formation on a prespecified real track and evaluation of benefits of the onboard supercapacitor ESS in real time

A Current Source Converter-Based Active Power Filter for Mitigation of Harmonics at the Interface of Distribution and Transmission Systems

A medium-power current source converter (CSC)-based shunt active power filter (APF) system is designed and implemented to suppress the amplification of low-order harmonics at the medium-voltage (MV) interface bus between the distribution and transmission systems, owing to the presence of large shunt capacitor banks installed only for reactive power compensation. Four CSC-based APF modules designed at 1.0 kV are operated in parallel and connected to the 31.5-kV MV bus via a specially designed coupling transformer. In each APF module, a specially designed LC-type input filter eliminates the switching ripples, and active damping method embedded into the control software suppresses harmonic frequencies around the corner frequency of the input filter. The resulting system can operate at relatively high frequencies in the range from 2.0 to 3.0 kHz, depending upon which selected harmonics among 5th, 7th, 11th, and 13th are to be eliminated. Furthermore, in order to reduce the installed capacity of CSCs, selective harmonic amplification method is applied to the APF system described in the paper. MV APF system has been built as a mobile system for temporary connection to a problematic MV interface bus until a permanent solution is found for that location in the distribution system

Design and Implementation of a 154-kV +/- 50-Mvar Transmission STATCOM Based on 21-Level Cascaded Multilevel Converter

In this research work, the design and implementation of a 154-kV +/- 50-Mvar transmission static synchronous compensator (T-STATCOM) have been carried out primarily for the purposes of reactive power compensation and terminal voltage regulation and secondarily for power system stability. The implemented T-STATCOM consists of five 10.5-kV +/- 12-Mvar cascaded multilevel converter (CMC) modules operating in parallel. The power stage of each CMC is composed of five series-connected H-bridges (HBs) in each phase, thus resulting in 21-level line-to-line voltages. Due to modularity and flexibility of implemented HBs, each CMC module has reached a power density of 250 kvar/m(3), thus making the mobility of the system implementable. DC-link capacitor voltages of HBs are perfectly balanced by means of the modified selective swapping algorithm proposed. The field tests carried out at full load in the 154-kV transformer substation where T-STATCOM is installed have shown that the steady-state and transient responses of the system are quite satisfactory