A New Method for Placement of DG Units in Distribution Networks

Topics: Electricity distribution, Electricity generation, Electric power transmission Pages: 13 (3723 words) Published: June 8, 2012
A New Method for Placement of DG Units in Distribution Networks H.Hedayati, S.A.Nabaviniaki, Senior Member, IEEE, and A.Akbarimajd

Abstract-- In this paper a new method for placement of DG (distributed generation) units in distribution networks has been presented. This method is based on two factors: analysis of power flow continuation and determination of the most sensitive voltage buses to collapse voltage. This method has been executed on a typical 34-Bus test system. Efficiency of proposed method in improvement of voltage profile and reduction of power losses is verified by analytical and simulation results. Also the method may cause to increase of capacity saving, maximum loadability voltage stability margin. Index terms -- DG, capacity saving , collapse voltage, maximum loadability , CPF , voltage stability.

Different methods are used for locating. Lagrange method and two degrees gradiant and sensivity analysis method has been employed for placement [4]-[5]-[6]-[7]. This paper presents a new method for placement of DG units in distribution networks. This method is based on the analysis of power flow continuation and determination of voltage buses that are most sensitive to collapse voltage [8]. Subsequently, by selecting a objective function and using an iterative algorithm, DG units with known capacity will be installed on previously determined voltage buses. In iterative algorithm, the method of continuation power flow is used for determination of maximum loadability, thus it is needed to study the impact of different DG technologies on static voltage stability. This method will be executed on a typical 34-Bus test system. II-The impact of different DG technologies on Voltage Stability A. Synchronous Generator Conventional synchronous generators are capable of both generating and absorbing reactive power. Therefore, the use of DG’s utilizing overexcited synchronous generators will allow on-site production of reactive power. The local generation of reactive power reduces its import from the feeder, thus reduces the associated losses, and improves the voltage profile. As a consequence, the voltage security is also improved. P-V curves have been traditionally used as a graphical tool for studying voltage stability in electric power systems. Fig. 1 shows conceptually the impact of a synchronous generator on voltage stability of a hypothetic node. As can be seen in the figure, installation of a distributed generator of shifts the operation point from point A to point B on the corresponding P-V curve. This event results in VDG-V0 volts raise in the node voltage also it results in voltage security enhancement i.e. the stability margin increases from m0 to mDG. An immediate conclusion to be drawn here is that the installation of a distributed generation will most likely enhance the voltage stability of the network as long as the DG rating is smaller than twice of the local loading level. This conclusion has been confirmed by computer simulations reported in [9].

I.Introduction Newly introduced distributed or decentralized generation units, connected to local distribution systems, in general are not dispatchable by a central operator. These units may apply significantly large impacts on power flow, voltage profile, stability, continuity and quality of electricity suppliers and the power delivered to customers [1]. Exact output power of some DGs such as photovoltaic energy converters and wind turbines depends on the weather conditions and then it is difficult to anticipate it accurately. Due to the locally available resources and the small scale, in general, DG units are connected at distribution level. When the penetration of DG is high, the generated power of DG units alters not only the power flow in the distribution system, but also that in the transmission system. Consequently, the connection of distributed generation to the network may influence the stability of the power system, i.e. angle, frequency and...
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