A. Acik

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.

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The iron and steel industry has been growing increasingly in Turkey in the last decade. Today, its electricity demand is nearly one tenth of the installed generation capability of 40 GW in the country. In this paper, power quality (PQ) investigations based on the arc furnace installations of the iron and steel plants using field measurements according to the international standard IEC 61000-4-30 are documented. Interharmonics and voltage flicker problems occurring both at the common-coupling points of those plants and at the arc furnace and static VAr compensator (SVC) systems of the plants themselves are determined with the use of GPS receiver synchronization modules attached to the mobile PQ measurement systems. It has been observed that flicker and interharmonic problems are dominant at the points of common couplings where arc furnace installations are supplied. Based on the field measurements obtained with collaborative work of five arc furnace plants, it is possible to say that contemporary SVC systems cause interharmonic amplification problems around the second harmonic, and novel methods are required to solve this problem.

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

This paper deals with the development and implementation of a current-source-converter-based static synchronous compensator (CSC-STATCOM) applied to the volt-ampere-reactive (VAR) compensation problem of coal mining excavators. It is composed of a plusmn750-kVAR full-bridge CSC with selective harmonic elimination, a low-pass input filter tuned to 200 Hz, and a Delta/Y-connected coupling transformer for connection to medium-voltage load bus. Each power semiconductor switch is composed of an asymmetrical integrated gate commutated thyristor (IGCT) connected in series with a reverse-blocking diode and switched at 500 Hz to eliminate 5th, 7th, 11th, and 13th current harmonics produced by the CSC. Operating principles, power stage, design of dc link, and input filter are also described in this paper. It has been verified by field tests that the developed STATCOM follows rapid fluctuations in nearly symmetrical lagging and leading VAR consumption of electric excavators, resulting in nearly unity power factor on monthly basis, and the harmonic current spectra in the lines of CSC-STATCOM at the point of common coupling comply with the IEEE Std. 519-1992

Electrical Power Quality of Iron and Steel Industry in Turkey

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.

Reactive-Power Compensation of Coal Mining Excavators by Using a New-Generation STATCOM

An active-clamped, zero-voltage switched forward power converter equipped with a soft-switched synchronous rectifier is designed and implemented for low output voltage applications where maximized efficiency is of utmost importance. The power converter efficiency is maximized due to the soft-switching of the main active clamp and the synchronous rectifier MOSFET switches. Experimental results are presented for a power converter with a DC input voltage of 48 V, an output voltage of 5 V and a DC electronic load up to 10 A. The measured efficiency was 92% for an output power of 50 W.

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

This work is devoted to taking nationwide power quality (PQ) snapshots of the Turkish electricity transmission system, via field measurements carried out by application specific mobile monitoring equipment. This project is carried out as a subproject of the national power quality project of Turkey, and is aimed at investigating the general status of electric power quality and reactive power flows in the electricity transmission system all over the country. Critical points will then be selected to place permanent PQ monitors, and to carry out troubleshooting projects on the system. This paper describes the mobile monitoring system established, and the methodology used to obtain power quality snapshots of the Turkish electricity transmission system. Some sample outputs of the mobile monitoring system are also given in the paper.

Active clamped ZVS forward converter with soft-switched synchronous rectifier for maximum efficiency operation

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.

Mobile Monitoring System to Take PQ Snapshots of Turkish Electricity Transmission System

This paper discusses feasibility of conventional and fully static reactive power compensation techniques used in the solution of power quality problems of coal conveyor belt drives and also describes the features and field performance of the distribution type static synchronous compensator (D-STATCOM) prototypes in such applications. They are composed of 2-level, 3-leg voltage/current source converters (VSC/CSC), low-pass input filters and Delta/Y connected coupling transformers to allow their connection to medium voltage load bus. Reactive power is controlled in both capacitive and inductive regions by phase-shift-angle control. Dominant voltage/current harmonics of VSC/CSC are eliminated by selective harmonic elimination method (SHEM). Developed D-STATCOMs are shown to comply with IEEE Std 519-1992 even for the weakest supply. Viability of D-STATCOM in reactive power compensation of conveyor belts has been proven in the field.

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

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.

Reactive Power Compensation of Coal Conveyor Belt Drives by Using D-STATCOMs

This paper deals with the development and implementation of a current-source converter based static synchronous compensator (CSC-STATCOM) applied to VAr compensation problem of coal mining excavators. It is composed of a /spl plusmn/750 kVAr full-bridge current source converter with selective harmonic elimination, a low-pass input filter tuned to 200 Hz, and a /spl delta//Y connected coupling transformer for connection to medium voltage load bus. Each power semiconductor switch is composed of an asymmetrical IGCT connected in series with a reverse blocking diode and switched at 500 Hz to eliminate 5/sup th/, 7/sup th/, 11/sup th/, and 13/sup th/ current harmonics produced by CSC. Operating principles, power stage, and design of DC link, and input filter are also described in the paper. It has been verified by field tests that the developed STATCOM follows rapid fluctuations in nearly symmetrical lagging and leading VAr consumption of electric excavators, resulting in nearly unity pf on monthly basis, and the harmonic current spectra in the lines of CSC-STATCOM at the point of common coupling comply with IEEE Std. 519-1992.