Research For Power Loss Control In Distribution Systems By UPFC

With the rapid development of national economy and the increasing of electricity load, the line loss issue has become a major challenge power supply enterprises faced. Not only does it affect the economic efficiency of power supply enterprises, but also reflects the power grid structure and the rationality of operation mode, and the power supply enterprise management and technical level. Thus reducing the loss is one of the most important goals to strive for power supply enterprises. There are many loss links in the power grid, in which the line loss indicators of power distribution network outstanding especially due to low voltage, complex network, large degree of old equipments, and far conveying distance of individual transmission line. How to reduce such a large and complex line loss of power distribution network has become a topic of current electricity workers actively involved in research.Flexible AC Transmission System (FACTS) technology is the combination of power electronic technology, modern control technology and computer technology and the electric power system. By controlling the bus voltage, transmission line reactance and phase angle of the transmission system, it rapidly realize the adjustment of the line active and reactive power flow and the rational allocation of transmission power that can reduce power consumption and cost of power generation, and improve the stability of the exchange system and the transmission capacity of traditional AC transmission system to meet the targets of the power system security, reliability and economic operation.As one the most powerful member of Flexible AC Transmission System family, unified power flow controller (UPFC) is characteristic of multi-function control capacity and powerful flexibility to adjust active power and reactive power of the system quickly and flexibly. Investment and successful operation of the world’s first unified power flow controller device in the United States Inez substation in1998not only proved the correctness in theory and the feasibility in practice of the unified power flow controller, also proved the capability of the unified power flow controller to reduce line loss effectively, which brought enormous economic benefits to the electricity system. This paper studies the influence of the UPFC device on the line loss of power distribution network, and the main work can be roughly divided into two parts.The first part of this paper is to analysis the principle of UPFC, using the simulation software PSCAD/EMTDC to establish the detailed dynamic model based on the conventional PI control system-level control and the model of electric power system of stand-alone by the double circuit line to infinite power system. Analyse the UPFC simulation of active power and reactive power regulation in steady-state power system, as well as the simulation of the UPFC influence on electric power system flow, voltage, and oscillation when three phase short circuit occurs.The second part analyses the method to reduce the line losses of distribution network, focusing on the analysis of reactive power compensation methods, identifying the compensation capacity, compensation effects and so on,as well as the comparative analysis of the loss reduction characteristics of the UPFC. In the simulation software PSCAD/EMTDC environment, establish the detailed dynamic model of the UPFC access the annular distribution network. Simulation analysis of the UPFC impact on the line loss of annular distribution network, compared to the line loss of power distribution network excluding UPFC, verify that it has a good performance of reducing the distribution grid line loss. The establishment of two machine5-node system, conclude that the best installed position of UPFC with the lowest network loss through the simulation.