Power Flow and Loss Allocation for Deregulated (1)

Power flow and loss allocation for deregulated transmission systems Jen-Hao Teng * Department of Electrical Engineering, I-Shou University, 1, Section 1, Hsueh-Cheng Rd. Ta-Hsu Hsiang, Kaohsiung County 840, Taiwan, ROC Received 9 December 2002; revised 25 November 2004; accepted 29 December 2004 Abstract This paper proposes a systematic method to allocate the power flow and loss for deregulated transmission systems. The proposed method is developed based on the ba sic circuit theories, equivalent curr ent injection and equivalent impedance. Four steps are used to trace the voltages, currents, power flows, and losses contributed by each generator sequentially. Using this method, the real and reactive power on each transmission lines and their sources and destinations can be calculated. The loss allocation of each line, which is produced by each generator, can also be obtained. Test results show that the proposed method can satisfy the power flow equation, the power balance equation and the basic circuit theories. Comparisons with previous methods are also provided to demonstrate the contributions of the proposed method. q 2005 Elsevier Ltd. All rights reserved. Keywords: Deregulation; Power flow and loss allocation; Kirchhoff’s current law; Kirchhoff’s voltage law; Superposition law; Equivalent current injection; Equivalent impedance 1. Introduction Nowadays, the electric power industry is under dereg- ula tion in res ponse to cha nge s in the law, tec hno logy, market and competition. Deregulated power systems cannot bundle the generation, transmission, distribution and retail activities, which were traditionally carried out by vertically integrated utilities; therefore, different pricing policies will exist between different power companies. With the separate pricing of generation, transmission and distribution, it is necessary to find the capacity usage of different transactions happe ni ng at the same time so that a fair use-of- tra nsmissi on- sys tem cha rge can be giv en to indivi dua l customer separately. Then the transparency in the operation of deregulated power systems can be achieved. In additi onal, the capac ity usage is another impor tant issue for transmission congestion manageme nts; therefore, the power produced by each generator and consumed by each load through the network should be traced. In these aspects, problems arise because all transactions have to share the same transmission network simultaneously. Those problems inc ludi ng ‘Which genera tors are sup plying thi s loa d?’ ‘Which generator or load is making the biggest usage of this tra nsmissi on line ?’ and ‘Which genera tor or loa d is producing loss of this transmission line?’ etc., need to have acceptable sol uti ons in a fai r deregulated power sys tem [1,2]. To solve these pr oblems, an al gor ithm, which can all oca te the contri but ion s of pow er flow and los s from individual generator through the transmission system to the loads, is needed. This is both an essential and challenging task. Some methods [3–13] have been proposed to trace the power flow and loss in deregulated environments. The use of the predetermined factors to allocate the loss is the most commonly used method. The losses allocated are based on the bus gener ation or load, but not on their relative locati on within the network [3]. Los s allocation bas ed on inc re- mental transmission loss (ITL) coefficients was proposed by Schweppe et al. [4]. The method based on the ITL that can be used to handle large changes in operating conditions was proposed in Ref. [5]. Gross and Tao proposed a physical- flow-bas ed approac h to allo cate tran smi ssio n loss [6]. Quadratic loss approximation formulas and some assump- tions, such as bus voltage magnitude and bus voltage angle, Electrical Power and Energy Systems 27 (2005) 327–333 www.elsevier.com/locate/ijepes 0142-0615/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijepes.2004.12.005 * Tel.: C886 7 6577711x6613; fax: C886 7 6577205. E-mail address: [email protected].

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Power Flow and Loss Allocation for Deregulated (1)