Yoshifumi Mochinaga

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.