Yener Akkaya

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

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

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.

Electrical Power Quality of Iron and Steel Industry in Turkey

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.

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

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

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.

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

In this paper, the National Power Quality Monitoring System, which is designed to monitor the power quality (PQ) of the Turkish Electricity Transmission System is presented. The National PQ Monitoring System consists of three main parts: PQ monitors, which are installed all over the country; a monitoring center, which collects the data sent by the power quality monitors in a database and provides assessment facilities; and a client software for remote connection to the center and analysis of the collected PQ data. PQ monitors compute the PQ parameters according to the IEC-Standard-61000-4-30. The PQ monitoring center is located in the TEIAS Ankara Bahcelievler campus and it has a huge digital light processing (DLP) display to observe the PQ events on the map of Turkey as soon as the event occurs. The client software provides remote connection from universities, research institutes and TEIAS offices to the monitoring center to analyse the collected PQ data. This is a three-year project which started in March 2006 To date, PQ monitor design has been completed. 9 monitors have been installed at various transformer substations in Turkey and the monitoring center is now collecting and displaying PQ data continously. 150 PQ monitors will have been installed by the end of the project all over the country and the PQ of the whole electricity transmission system will be monitored. Some measurement results obtained upto now are also presented in this paper.