C. Ermis

Design and Implementation of a 154-kV

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/m3, 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.

\pm

A medium power Current Source Converter (CSC) based 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. For this purpose, four CSC based APF units 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 natural 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 (SHAM) 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.

50-Mvar Transmission STATCOM Based on 21-Level Cascaded Multilevel Converter

In this research work, design and implementation of a 154 kV, ± 50 MVAr Transmission STATCOM (T-STATCOM) has 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 (HB) in each phase, thus resulting in 21-level line-to-line voltages. Due to modularity and flexibility of implemented HBs, a CMC module power density of 250kVAr/m3 is reached, 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 and put into service have shown that the steady-state and transient responses of the system are quite satisfactory.

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

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.

Design and implementation of a 154 kV, ±50 MVAr Transmission STATCOM based on 21-level Cascaded Multilevel Converter

Design and implementation of a unified, relocatable static VAr compensator (SVC) meeting reactive power compensation needs of various coal enterprises of Turkey for open-cast lignite mining have been presented. Design and sizing of SVCs are based on mains data for all possible connection points, load bus data recorded in the field, monthly electric bills and simulations carried out on PSCAD/EMTDC, SPICE and MATLAB. In addition to standard AC/DC converter and motor tools used in the modeling of electric excavators, actual load characteristics obtained from data collected in the field by means of a data acquisition system have been processed in PSCAD/EMTDC to rind out reactive power demand of each load bus, and to optimize sizing of SVC within the power factor penalty limits imposed by electricity authorities. The SVC component ratings have been based upon the suitability to all possible loads under worst operating conditions, thus making sure that they can be operated for different loading conditions, minimizing stock requirements, and inspection and maintenance costs. The implemented systems are flexible and extendable in order to meet the future needs of coal enterprises.

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

This paper describes the solution of power quality problems arising from 12-pulse smelter converters in the ETI Aluminum Works, Seydis

A unified relocatable SVC for open-cast lignite mining in Turkey

80ehir, Turkey. The design work is based on practical data collected in the field as well as on the results of detailed simulation studies obtained by EMTDC/PSCAD, SPICE, and MATLAB. The main design objective is to meet both present regulations and harmonic standards by using robust, reliable, and cost-effective systems with a long life expectancy. The shunt-connected passive reactive power compensation system is composed of a damped 11th harmonic filter and a make-up filter tuned to the 5th harmonic with optional damping resistor. Such a system exhibits nearly transient-free switching and series-resonance proof characteristics owing to damping resistors. A close correlation has been obtained between theoretical results and field data.

Power quality solutions for 12-pulse smelter converters in ETI aluminum works

A medium power Current Source Converter (CSC) based 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. For this purpose, four CSC based APF units 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 natural 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 (SHAM) 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.

A Current Source Converter based Active Power Filter for mitigation of harmonics at the interface of distribution and transmission systems

This paper is devoted to the design and implementation of a 12-pulse thyristor controlled reactor (TCR) system, which constitutes a low-cost solution to the reactive power compensation problem of a ladle furnace in Iskenderun iron and steel plant (ISDEMIR). Design objectives and elimination of 5th and 7th harmonic current components produced by 6-pulse TCRs are met by connecting two sets of 6 kV, 6 MVAr TCRs to the 34.5 kV ladle furnace bus by the use of two separate converter transformers with delta- and wye-connected secondaries. The effects of dissimilarities between the two sets of 6-pulse TCRs on the harmonic current content of the resulting 12-pulse TCR system are also presented in this paper. Both reactive power compensation and power system redundancy objectives are met by using two separate and dissimilar transformers instead of a single transformer with identical /spl Delta/-and Y-connected secondaries for connection to 6-pulse TCRs, resulting in a two-folded design. One of these transformers is chosen as a sufficiently large unit with two identical /spl Delta/-connected secondaries to supply the ladle furnace in emergency or during maintenance periods of main transformer. In normal operation mode of the resulting ladle furnace power system, the 12-pulse TCR implemented in the project gives quite satisfactory results in reactive power compensation and nearly meets harmonic standards currently used in the country.

Two-folded implementation of a 12-pulse TCR with dissimilar transformers for a ladle furnace: reactive power compensation and power system redundancy

In this paper, the combination of a Thyristor Switched shunt Reactor (TSR) and a Current Source Converter (CSC) based Active Power Filter (APF) has been proposed for mitigation of power quality problems of Light Rail public Transportation Systems (LRTS) 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 power quality problems of LRTS. Conventional power quality solutions have also been assessed, and the corresponding theoretical results are given in comparison with the proposed system.