Principal Research Results

Development of Loop Power Flow Controller for Autonomous Demand
Area Power System−Demonstration and Estimation of Distributed Control Using Local Information−
BackgroundTo smooth introduction of distributed generation, we proposed the loop or mesh structure for distribution systems using loop
power flow controller (LPC) at the opened switch which can connect the adjoining feeder. LPC can optimize control for distribution
systems in the points of reducing voltage rise, voltage fluctuation and loss minimum power flow control, and so on, with acquisition ofdistribution system status. Adapting to areas that cannot use communication systems, in consideration of power quality for the transition phenomena and limitation of fault area, we also required distributed control using local voltage information for the LPC.

Objectives
The purposes of this paper are to demonstrate basic functions of LPC and to estimate the control method using simulation
analysis.

Principal Results(1) Demonstration of basic functions
We added functions (PQ cont.) of loop power flow and reactive power control by voltage drops of the feeders to the originalcontrol ＊ 1 (P cont.). The change of the control method aims to cooperate with voltage controller at substation transformers and improve the voltage stability. The basic functions of PQ control were demonstrated by the Demand Area Power System HybridDemonstration Facility (Fig. 1) located at Akagi testing center in CRIEPI.
Power flow control functions: We confirmed the voltage control function that restrains the voltage rise from 4% to under
1% occurrence by power generation and increase of the load. For transition of power generation, the LPC responded within 2 cycles(Solid curve of Fig. 1 upper-left) and restrained the voltage rise compared with the radial distribution system (Broken curve of Fig. 1upper-left).
Fault area limiting functions: We proposed a basic function to separate the fault section required in loop operation anddemonstrated the function of LPC for fault control in the cases with observation V0 ＊ 2 and without (Fig. 1 lower-left).
(2) Efficacy of distributed control
We compared the voltage rise, voltage fluctuation and total line losses for radial distribution system, distributed control withLPC and optimal control with LPC (Fig. 2). The voltage rise and the voltage fluctuation became the same as optimal control. The totalline loss was little increased compared with optimal control, but the loss was half of the radial distribution system.

Future Developments
We will consider cooperation with existing facilities such as tap control of distribution substations and SVR control.
Main Researcher: Naotaka Okada,
Research Scientist, Customer Systems Sector, System Engineering Research Laboratory
Reference
Development of loop power flow controller for autonomous demand area power system -Demonstration and estimation of distributedcontrol using local information-, No. T03050(2004-4)＊1：Komae Reserch Lab. Rep. : Development of Loop Power Flow Controller for Demand Area Power System -Autonomous

Control in Transition Period-, No. T00045(2001-4)＊2： Zero phase voltage that was observed in case of line-to-ground fault.

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B. Creation of integrated energy service

Fig.1 Demonstration of basic functions(Rad.:Radial distribution system, P cont.: Loop power flow control, PQ cont.: Loop power flow and reactive power control,
ML:Optimal control for minimum line loss, MV: Optimal control for minimum voltage error)

Fig.2 Comparison of control method

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