Shigeyuki Sugimoto

Principle and characteristics of a fault current limiter with series compensation

A power system fault current limiter with series compensation, which is composed of a compensation capacitor and a limiting reactor in series, is proposed. A solid-state switch connected in parallel with the capacitor controls either the ordinal series compensation or fault current limitation. A feasibility study of the current limiter by simulation analysis is presented and the effectiveness of the current limiter is evaluated from the viewpoints of transient stability improvement and device capacity. The current limiter is a useful protection device for large, high power transmission systems.

Development and testing of prototype models for a high-performance 300 MW self-commutated AC/DC converter

A technical project is under way in Japan to develop a high-performance self-commutated power converter for future HVDC transmission and DC interconnection applications. In the first stage of the project, prototype power converter models for a 300 MW self-commutated converter were developed. The models were subjected to factory testing to verify the technology for series connection of a large number of gate turn-off thyristors (GTOs), a gate power supply from the high voltage main circuit and energy regeneration using snubber circuits. Satisfactory results were obtained.

Development of a control system for a high-performance self-commutated AC/DC converter

A self-commutated AC/DC converter composed of controlled turn-off devices to be applied to future system interconnection is described. The advantages of a control system for this type of converter are: (1) commutation does not fail when the system voltage is decreased or distorted by a power system fault; (2) it needs no equipment for reactive power supply, such as static capacitors or synchronous rotating condensers, when used in a low short-circuit capacity power system; and (3) it can independently control active power through DC lines and reactive power from each terminal. The proposed back-to-back (BTB) control system using the voltage margin method was verified with a simulator, and the results demonstrated the excellent features of the high-performance self-commutated converter.

Thyristor controlled ground fault current limiting system for ungrounded power distribution systems

A thyristor controlled ground fault current limiting system (TGCL) was proposed to prevent one-line ground fault current rises due to increased capacitance to ground. Basic components of the TGCL are a main ground fault current limiter, which rapidly adjusts a compensating reactor level for the capacitance to ground, and the TGCLs controller. Control is ensured by an in-phase control method for zero-phase sequence voltage and current. The method determines the direction of ground faults and the compensating reactor level. The fast control which can be realized shows the TGCL is a valuable protecting system for high ground fault current distribution systems.

Application of Series Type BTB Converter for Minimizing Circulating Current and Balancing Power Transformers in Loop Distribution Lines

A method for minimizing circulating current and balancing power transformer in loop distribution line of an industrial park is proposed. The proposed method uses a series type back-to-back (BTB) converter in loop distribution line of industrial park. Loop distribution line is formed by tying end of two radial lines by a looping wire. Looping wire has a re-closer circuit breaker to localize fault inside loop. Operation of the circuit breaker depends on the zero sequence voltage and current detection of series type BTB converter. This proposed method solves the problem of heavily loaded and lightly-loaded lines condition in distribution line autonomously, which 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. Analysis and simulation results to validate the proposed method are presented in this paper.

Output Power Leveling of Wind Turbine Generator by Pitch Angle Control Using H/sub /spl infin// Control

Effective utilization of renewable energies such as wind energy is expected instead of the fossil fuels. Wind energy is not constant and windmill output is proportional to the cube of wind speed, which causes fluctuating power of wind turbine generator (WTG). In order to reduce the fluctuating power of WTG, this paper presents an output power leveling technique of WTG by pitch angle control using Hinfin control, and the control input of WTG linear model is separated from the disturbance. The simulation results using actual detailed model for WTG show the effectiveness of the proposed method

Uninterruptible Power Supply System Utilizing Electric Double-Layer Capacitors

Recently the electric double-layer capacitor (EDLC) which is rapidly charged and discharged and offers long life, maintenance-free, has been developed as a new energy storage element. Therefore, we developed the uninterruptible power supply system utilizing EDLC. This paper describes the outline of this system and the instantaneous voltage sag compensation result.

Bi-directional Zero-Current-Switching Approach Applied for Energy Storage System Using Electric Double Layer Capacitor

We have proposed the current-source energy capacitor system (CS-ECS) in our previous work, which consists of an electric double-layer capacitor (EDLC), current-source inverter, and bi-directional DC-DC converter (four-quadrant DC-DC converter). However, this system has low efficiency due to hard-switching losses. Improvements of efficiency and performance are indispensable to implement the proposed system. This paper proposes the soft-switched four-quadrant DC-DC converter with an simple L-C resonant circuit for CS-ECS. High efficiency of the proposed system is achieved based on zero-current switching (ZCS) since a insulated gate bipolar transistors (IGBTs) of that converter softly turns on and turns off by using current-mode resonance. In order to illustrate the operating principle of the proposed system, we analyze in detail through a theoretical approach and computer simulations with MATLAB/SIMULINK.

Practical evaluations for three-phase soft-switching inverter with high-frequency pulse-current transformer

In this paper, a prototype of the auxiliary resonant commutated snubber circuit (ARCS) incorporating a pulse-current feedback high-frequency transformer with power regeneration loop is described for three-phase inverter from a practical point of view. For three-phase voltage-fed soft-switching inverter, soft-switching active power filter and active PFC rectifier, the soft-switching inverter topology treated here has significant advantages of effective power loss reduction in the auxiliary active switching power devices in the ARCS. In addition, this paper presents a DSP-based digitally-control space vector-modulated three-phase voltage-fed inverter with high-frequency pulse-current transformer (HFPT) assisted ARCS, which can efficiently operate under a stable condition of a zero voltage soft-switching commutation. The steady-state operating circuit analysis of the new ARCS has the salient features and the practical design procedure of this resonant snubber are illustrated and discussed on the basis of simulation and experimental results. The operating performance of this soft-switching inverter using IGBT power modules and its evaluations in the steady-state are actually discussed as compared with the conventional three-phase voltage-fed space vector modulated hard-switching inverter.

Fault current limiting system for 500‐kV power systems

Recently, expansion in the scale of power systems and development of localized power sources are leading to an increase in fault current of 500-kV systems. In the future, it is quite likely that the fault current at the interconnection of such power systems may exceed the rated short-time current of existing electric power facilities. As one of the solutions of this problem, a thyristor-controlled series-resonant-type fault current limiter (FCL) is proposed to restrain the fault current. This paper deals with the FCL system configuration, the placement method of the FCL in power systems, the outline of the FCLs specification, and the operation method of the protective relay in the multimachine system. Finally, the effectiveness of the FCL is evaluated from the viewpoints of limiting the fault current by simulation analysis. The FCL is shown to be a useful protection device for large, high-capacity power systems.