Loop distribution system with LPC and its planning method

Loop Power Controller (LPC) is a looping device at the adequate point in a distribution system which is usually operated with the radial configuration. It can achieve various power quality improvements such as system voltage control when incorporating distributed generations (DG), balancing control of distribution feeder loadings and high speed compensation of voltage sag. LPC is a promising device to form loop distribution systems without any increase in short-circuit current. In this paper, we demonstrate a control method of LPC and a determination method of the control coefficients with experimental results of proposed control. Practical application of loop distribution system with LPC first requires economic justification. A system planning method to optimize LPC location and capacity has been developed for evaluating the marginal cost of LPC application. 6.6kV overhead distribution systems are currently formed in Japan as radial networks which is alias called open loop configuration. A loop system can be easily formed by closing a coupled switch. Therefore, we considered the coupled switch to be the installing points of LPC. The basic concept of the loop distribution system using the LPC we propose is as follows. A) Aim is free access of DG. B) System responds flexibly to unbalanced load between feeders, and makes effective use of equipment. C) To enable this, the system is formed in the shape of a loop from a radial. D) A loop distribution system is provided without altering existing systems such as the protection system, except for loop points. To accomplish all this, we used VSC BTB (back to back) system as the LPC. Adapting to the area that cannot use communication system, points of view at the power quality for the transition phenomena and limiting the fault area, we also required the distributed control using local voltage information for the LPC control. In this paper, a method of determining the control coefficients that combines the optimum power-flow calculation and the least-squares method was proposed. Verification of the distributed control method by the proposed method was performed by field test using a 6.6kV-100kVA LPC and the demand area power system (DAPS) simulator at the Akagi testing center of Central Research Institute of Electric Power Industry (CRIEPI). To realize a practical distribution system with LPC, it is needed to prove quantitatively the economic validity of LPC application as a solution to the distribution system related problems. Various uncertainties should be considered in these discussions. Therefore, an efficient planning method to optimize LPC location and capacity has been developed to identify the minimum LPC cost. The method can take multiple load condition simultaneously into account. Using the method, economical benefit of LPC application to cope with a local demand increase is verified comparing with a general measure of distribution line and transformer expansion. In this evaluation, the effect of the uncertainties of demand increase in location, quantity and time pattern has been widely discussed through parametric analyses.