Ali Nezih Guven

Congestion-Driven Transmission Planning Considering the Impact of Generator Expansion

This paper presents a multi-year transmission expansion planning (TEP) model which considers the transmission congestion and the impact of generation investment cost in the planning horizon. The Benders decomposition approach is utilized which decomposes TEP into a master problem and two subproblems representing security and optimal operation. The operation cost due to congestion (OCC) is considered in the proposed model given that the congestion level is a proper criterion for measuring the degree of competitiveness in an electricity market. The model evaluates sensitivity of the optimal TEP to congestion level, planning horizon, and financial constraints. Regulators can utilize the proposed results to provide long-term TEP to market players and to develop incentive mechanisms to trigger generation investments. The proposed approach is applied to a hypothetical system and Turkish power system.

Damping measures against prospective oscillations between Turkish grid and ENTSO-E System

After the synchronous interconnection of Turkish Power System to ENTSO-E CESA (former UCTE) System, inter-area oscillations in the range of 0.15 Hz are prone to occur, according to simulation studies. Therefore, some preventive measures should be considered in order to ensure stable operation of the network after the interconnection. This study summarizes the effects of following measures based on computer simulations: 1) Retuning of power system stabilizers (PSS) of the important power plants in Turkey, 2) Controller modification of static VAR compensators (SVC) existing in steel melting arc furnaces that are supplied directly from the transmission system, 3) Controller modification of ±50 MVAR STATCOM which is designed for voltage regulation, 4) Application of breaking resistors as a backup measure in case of malfunctioning of the other solutions. In addition to individual analysis of each measure, their combined contribution is also analyzed. A load flow scenario, in which Turkey exports 900 MW to ENTO-E CESA System, is utilized as a reference scenario. In simulations, Turkish grid is represented in detail and a reduced representation of ENTSO-E CESA network, which consists of 75 nodes and 133 lines, is utilized. The results show positive contribution of each measure to system damping performance. The study includes comparison of each preventive measures contribution level and conclusive recommendations.

Promoting the Investment on IPPs for Optimal Grid Planning

This paper presents a transmission expansion planning (TEP) model which coordinates investment decisions in monopolistic transmission and decentralized generator sectors. The proposed planning approach gauges transmission congestion and security constraints with respect to transmission investments while promoting investments on independent power produces (IPPs) through incentive payments. The paper includes discussions on incentive mechanisms and prioritization among qualified IPPs for several planning scenarios. Such incentives might be necessary to trigger investments on IPPs earlier than those projected by the decentralized generation system, when the power system security is threatened. The proposed planning approach would optimize the sum of transmission investments, incentive payments to IPPs, and congestion costs along the planning horizon. The case studies illustrate how the proposed planning algorithm could be utilized in order to determine incentive payments to candidate generators when necessary, and prioritize such incentives among multiple IPP candidates.

Assessment of the effect of hydroelectric power plants' governor settings on low frequency inter area oscillations

This paper deals with the specific problems of the electromechanical systems of large size hydroelectric power plants regarding low frequency inter area oscillations, which are prone to occur once the interconnected operation of Turkish Power System with the ENTSO-E CESA (former UCTE) System is established. The expected frequency of inter area oscillations is close to 0.15Hz, which is in the frequency range of interest of speed governing structures of turbines, as shown in the first and second parts of the paper. In the proceeding part, the governor parameter tuning study with regard to the defined objectives considering the contingency handling and system stability is explained and the effect of retuned governor settings of the sample hydroelectric power plant on the multi machine system is shown. In the final part, conclusions are made regarding the operation and dispatch of hydroelectric power plants in synchronous interconnected operation of the Turkish Power System and the ENTSO-E CESA System.

A geographical zoning methodology for nodal transmission use-of-system tariffs

Power systems are generally separated into transmission use-of-tariff (TUoT) zones to simplify the tariff mechanism, particularly for large grids. Each zone is an aggregation of neighboring nodes with similar tariffs that are determined based on long-run marginal cost (LRMC) calculations. This paper proposes a zoning methodology which ensures diversification of zonal tariffs while geographically aggregating the nodal TUoTs by weighted average approach. Investment cost-related pricing (ICRP) and DC-load-flow pricing (DCLFP) methods are utilized in computing the LRMC based nodal tariffs. Performance of the LMRC based pricing methods, sensitivity of the economical parameters on the results, and the proposed zoning approach are investigated for a simple 12-bus generic power system. Given the satisfactory results, TUoT zones of Turkish power network are determined with the proposed zoning algorithm for the tariff period of 2012-2014.

Alçak Gerilim Ekspres Fider Uygulaması ile Sezonsal Yüklenme Farkları Yüksek Olan Dağıtım Transformatörlerin Boşta Kayıplarının Azaltılması

Bu calismada, Akdeniz’de kiyisi olan isletmelerde yazliklarin yogun oldugu bolgelerde, yaz sezonu puant yuklenme seviyelerine gore kapasiteleri secilen dagitim transformatorlerin, sezon harici donemlerdeki teknik kayiplarinin minimize edilmesine yonelik tasarlanan alcak gerilim ekspres fider (AGEF) uygulamasinin teknik-ekonomik fizibilite analizleri ve sahada pilot uygulamasi aciklanmistir. AGEF uygulamasi, birbirine yakin iki dagitim transformatorunun AG ana baralarinin kablo ile birbirine baglamasi suretiyle, transformatorlerden biri devre disi iken diger transformator uzerinden her iki transformatorun de yuklerinin beslenmesi prensibine dayanir. Uygulamada onemli olan husus, guvenlik nedeniyle transformatorlerin AGEF uzerinden paralel calismasinin onlenmesidir. Calismada bu amacla bir kilitleme mekanizmasi da tasarlanmistir. Teknik analizler kapsamindaki gerilim dusumu ve teknik kayip analizleri DIgSILENT PowerFactory™ sebeke analiz yazilimi ile gerceklestirilmistir. AGEF uygulamasinda one cikan transformatorler onceliklendirme gostergeleri ile belirlenmistir. Elde edilen bulgular isiginda, Akdeniz Bolgesinde elektrik dagitim faaliyeti gosteren Toroslar Elektrik Dagitim A.Ş.’nin (EDAŞ) sorumluluk bolgesinde bulunan Karatas Ilcesinde, yazliklarin yogun oldugu ve dolayisiyla sezonsal yukun buyuk olcude degisiklik gosterdigi bir bolgede pilot uygulama gerceklestirilmistir.

Feasibility of distributing electric power through single-phase transformers at rural regions of Turkey based on rural characteristic indices

Single-phase (1-phase) transformers have been utilized in some countries to supply rural distribution regions which particularly have relatively low load densities (farms, villages, etc.). Leading countries include US, Canada, Mexico, New Zealand, and Australia. However, utilization of 1-phase transformers is very limited (almost negligible) at European countries. Turkey is among those countries in which electric is supplied through three-phase transformers regardless of the load density of the region to be supplied. The main objective of this paper is to quantify the technical and financial benefits of installing 1-phase transformers instead of three-phase transformers at the distribution network of Yeşilırmak Distribution Company (YEDAS) which shows very high rural characteristic in Turkey. Single- and three-phase transformer alternatives are compared technically based on computer simulations including voltage drop, technical losses and reliability. Pilot regions are defined considering their prevailing rural characteristics based on some metrics defined in this paper. The results show that distribution of power through 1-phase transformers by either single-wire-earth-return (SWER) or double-phase techniques are promising for YEDAS particularly for the rural regions which have highly rural characteristics.

Optimization of long-term investments of electric distribution systems considering planning metrics

This paper presents a dynamic planning algorithm methodology which optimizes long-term primary electric distribution network investments considering planning metrics. An algorithm which calculates a representative primary network model of distribution grids, whose primary and secondary networks are intricate, is developed. It is aimed to facilitate assessment of primary distribution network investment requirements and thereby defining grid investment candidates effectively. A planning algorithm, which considers representative primary network model and candidate planning investments as inputs, is developed based on a mixed integer programming (MIP) technique. Some planning metrics are defined in order to technically and economically assess optimum investments along the planning horizon. DIgSILENT PowerFactory (PF) software is utilized in technical analysis to assess impacts of candidate grid investments on technical constraints. The algorithms and planning metrics developed in the study are tested satisfactorily on pilot regions of Akdeniz Electric Distribution Company in Turkey.

Theoretical and practical aspects of implementing a low voltage express feeder between nearby distribution transformers to reduce annual losses

Capacity of distribution transformers is usually determined based on peak demand forecasted along a planning period. Peak demand actualizes at different seasons depending on the load characteristics of the transformers. For example, transformers at coastal towns essentially experience peak demand during summer periods. Although such transformers are loaded up to their capacities at summer seasons, their loading level reduces drastically during the off-season periods. This study addresses technical losses of such transformers and presents a solution to reduce the total transformer losses by means of implementing a low voltage express feeder (LVEF) between transformers close by. Total load of two nearby transformers is supplied by only one of the transformers through the LVEF while the other transformer is de-energized during off-season period. Depending on the criteria addressed in this study, this approach enables a decrease in the annual total loss of the system. Study includes a pilot implementation on-site.

Congestion-driven transmission planning considering the impact of generator expansion

This paper presents a multi-year transmission expansion planning (TEP) model which considers the transmission congestion and the impact of generation investment cost in the planning horizon. The Benders decomposition approach is utilized which decomposes TEP into a master problem and two subproblems representing security and optimal operation. The operation cost due to congestion (OCC) is considered in the proposed model given that the congestion level is a proper criterion for measuring the degree of competitiveness in an electricity market. The model evaluates sensitivity of the optimal TEP to congestion level, planning horizon, and financial constraints. Regulators can utilize the proposed results to provide long-term TEP to market players and to develop incentive mechanisms to trigger generation investments. The proposed approach is applied to a hypothetical system and Turkish power system.