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A method for effective utilization of power distribution apparatus in an industrial park by looping distribution lines is proposed. The proposed method uses a series type Back-To-Back (BTB) converter in loop distribution line. This method solves the problem of heavily-loaded and lightly-loaded lines condition in distribution line autonomously. The problem of heavily-loaded and lightly- loaded lines results in lower utilization of transformers and increases losses in electricity system of the industrial park. By employing this proposed method, effective utilization of apparatus is realized by minimizing circulating current and balancing power of transformers in loop distribution line. One of the major characteristics of the proposed scheme is that the required converter capacity is small and it can be installed close to the transformers in loop distribution line. Analysis and simulation results to validate the proposed method are presented in this paper.

It is necessary to develop the new power generation system using the unused low temperature thermal energy around 100 degrees C from a viewpoint of global warming prevention. Even if a shape memory alloy is bent in normal temperature, when it is warmed, it has the character which returns to the original straight form. Using this character of a shape memory alloy, unused thermal energy will be able to transform into rotation energy, and finally it can change into electric energy. We solved this energy conversion mechanism and the validity of this theory was indirectly verified by experiment. Furthermore, the power generation characteristic of the Shape Memory Alloy Engine was obtained by experiment.

In this paper, the novel standby mode operation of series type SMES (Superconducting Magnetic Energy Storage) for voltage sag compensation is presented. In the proposed control scheme for standby mode, the power losses are minimized and voltage drop is mitigated. The series type SMES is bypassed during the normal weather. During the adverse weather, the series type SMES can compensate voltage sags instantaneously. Simulations of standby mode operation and voltage sag compensation demonstrated the validation of the proposed control scheme.

This paper proposes a multi-agent approach to maintenance scheduling in restructured power systems. The restructuring of electric power industry has resulted in market-based approaches for unbundling a multitude of service provided by self-interested entities such as power generating companies (GENCOs), transmission providers (TRANSCOs) and distribution companies (DISCOs). The Independent System Operator (ISO) is responsible for the security of the system operation. The schedule submitted to ISO by GENCOs and TRANSCOs should satisfy security and reliability constraints.The proposed method consists of several GENCO Agents (GAGs), TARNSCO Agents (TAGs) and a ISO Agent(IAG). The IAG’s role in maintenance scheduling is limited to ensuring that the submitted schedules do not cause transmission congestion or endanger the system reliability. From the simulation results, it can be seen the proposed multi-agent approach could coordinate between generation and transmission maintenance schedules.

The increased renewable energy utilization, especially photovoltaic panels using solar energy or wind turbine generators (WTGs) using wind energy, has been expected in recent years from view point of CO2 gas emission reduction and environmental conservation. However, the generated power is always fluctuating because the WTGs are driven by fluctuating wind. Therefore, an energy storage system should be installed to compensate these fluctuating elements. The energy capacitor system (ECS) which combined the electric double-layer capacitor (EDLC) and the electronic circuits are now under development. In this paper, control system configuration for active and reactive output power simultaneous control and the bi-directional inverter using current source EDLC are proposed. Moreover, we discusse control methods required in generating-power leveling for WTGs, and show the effectiveness of the proposed system through simulations.

The present study examines the breaking capability of a hybrid fault current-limiting circuit breaker (FCLCB) when a fault occurs at a distance l of 0, 1, 4 and 8km away from the terminals of the FCLCB. This hybrid FCLCB is composed of an air circuit breaker unit connected in series with a resistive or an inductive fault current limiter (FCL). In the model of the inductive FCL, a capacitance Cp is connected in parallel with the limiting coil to simulate a coil stray capacitance and a necessary additional capacitance. By means of Mayr equation, the time variation of the arc conductance in the air circuit breaker unit was estimated to find out the result of the current interruption (successful or failure interruption) for the hybrid FCLCB. The minimum limiting impedance required to allow the hybrid FCLCB to attain a successful interruption was found to be 5 and 7Ω for a resistive FCL unit and an inductive FCL unit with Cp=5nF, respectively. Further, in the presence of an inductive FCL unit with Cp=50 and 100nF, the limiting impedance needed to interrupt the fault current successfully for all fault locations was proved to be 3Ω or above. From the results of this study, it can be said that (1) the insertion of the FCL unit should be done on the basis of a coordination between the circuit breaker unit and the FCL unit and (2) connecting a circuit breaker in series with fault current limiters may enable us to use non-greenhouse gas as quenching medium for interrupting large currents.

This paper proposes a multi-agent approach to decentralized power system restoration for a distribution system network. The proposed method consists of several Feeder Agents (FAGs) and Load Agents (LAGs). LAG corresponds to the customer load, while a FAG is developed to act as a manager for the decision process. From the simulation results, it can be seen the proposed multi-agent system could reach the right solution by making use of only local information. This means that the proposed multi-agent restoration system is a promising approach to more large-scale distribution networks.

Electric power generation using non-conventional sources is receiving considerable attention throughout the world. Wind energy is one of the available non-conventional energy sources. Electrical power generation using wind energy is possible in two ways, viz. constant speed operation and variable speed operation using power electronic converters. Variable speed power generation is attractive, because maximum electric power can be generated at all wind velocities. However, this system requires a rotor speed sensor, for vector control purpose, which increases the cost of the system. To alleviate the need of rotor speed sensor in vector control, we propose a new sensor-less control of PMSG (Permanent Magnet Synchronous Generator) based on the flux linkage. We can estimate the rotor position using the estimated flux linkage. We use a first-order lag compensator to obtain the flux linkage. Furthermore‚we estimate wind velocity and rotation speed using a observer. The effectiveness of the proposed method is demonstrated thorough simulation results.

This paper presents a method of amplitude control and unbalance compensation of the load voltage using a series–shunt power converter. The series power converter works to obtain a constant balanced sinusoidal load voltage. The shunt converter regulates the DC link voltage and compensates for the reactive current of the source within the rated current of the converter. To design the required capacity for the series–shunt power converter, the relation between the converter capacity and the load power factor at constant compensation voltage is introduced. The required capacity of the series–shunt power converter is reduced by more than 50% compared with that of a conventional series power converter. The effectiveness of the proposed load voltage compensation technique using the series–shunt power converter is verified by experiments. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 39–48, 2001

Recently, power systems have become larger and more complex. Particularly, the looping of power systems is becoming highly desirable to improve the stability. The main features of such looped power systems are: (i) comparatively fewer losses; and (ii) improved angle stability as well as voltage stability. However, these systems have demerits, such as, in case of route off fault in a loop power system, power disturbances increase more and more, etc. If these demerits are overcome, the loop power systems are going to be more beneficial. In an attempt to obtain a solution to such problems, this paper describes several results of applying a high-speed phase shifter in the control system of a loop power system.