Shotaro Murakami

Development of a large static VAr generator using self-commutated inverters for improving power system stability

A static VAr generator (SVG) using self-commutated inverters of 80 MVA capacity was developed and successfully applied to an annual 154 KV power system to stabilize the power system. The SVG consists of 48 pulse multiple inverters whereby gate turn-off (GTO) thyristors are applied. After installing it at a power system site, a field test was conducted to confirm the system stabilizing effect. The test results displayed the expected performance, and the SVG was proven to be effective power system stabilizer. The outline of the 80 MVA SVG, technical features, and the test results are described. >

Control and performance of a self-commutated GTO converter operating in parallel with line-commutated thyristor converters

Recently, static var generators (SVGs) or static synchronous compensators based on self-commutated converters have been put into practical use for the purpose of compensation for reactive power, power swings damping, and/or voltage control in power systems. The SVGs have also been applied to reduce voltage fluctuations appearing at high-speed train substations. When parallel resonance occurs between passive filters installed at a point of common coupling (PCC) and the power-system impedance existing upstream of the PCC, voltage/current harmonics are significantly amplified in the power system. This paper describes the control and performance for a self-commutated gate-turn-off (GTO) converter operating in parallel with conventional line-commutated thyristor converters. This hybrid power conversion system rated at more than dozens of MVA has an inductive load at the dc side. A bank of passive filters is connected not only for harmonic compensation of the line-commutated converters, but also as a constant leading reactive-power source. The GTO converter can control either leading or lagging reactive power so as to achieve unity power factor operation. In addition, it has the capability of damping out parallel resonance between the passive filters and the power-system impedance. This paper confirms the viability and effectiveness of the hybrid system by means of theory and computer simulation.

Development of a three‐phase unbalanced voltage fluctuation compensating system using a self‐commutated static var compensator

This paper describes a self-commutated static var compensator for suppressing voltage fluctuations caused by an ac electric railway (Shinkansen, or new trunk line). The ac electric railway is a single-phase load with large changes of reactive power and it causes large voltage fluctuations and power imbalances among the three phases in the power system. The authors have developed a new voltage fluctuation compensating system using a self-commutated static var compensator. This system has the functions of reactive power compensation and negative-phase-sequence current absorption. It can suppress rapidly changing voltage fluctuations and reduce the three-phase power imbalance caused by the ac electric railway effectively. This compensating system, with a capacity of 40 MVA, was put to practical use for the first time in the world in 1993. The test results at the site show that the system has excellent performance characteristics. A theoretical analysis of the characteristics of voltage fluctuations with or without the compensating system and an evaluation of test results, including a comparison between the theoretical and measured values, are also reported.