電圧型変換器を用いた直流送電系統の直流線路電流振動抑制

抄録

Conventional converter used in an HV DC system needs line volatge to turn off the current flowing through a thyristor or a mercury-arc valve. Hence HV DC system cannot supply electric power to the system which has no AC source, such as a generator or a synchronous condenser, or HV DC system has some difficulties to operate with the weak system. Conventional solution of avoiding these problems is installation of large capacity synchronous condensers, which needs considerable costs of construction and maintenance. Another solution is application of forced commutation converter. The recent development of high power and high frequency semiconductor devicees with fast gate turn-off ability (e. g. GTO's and SI thyristors) suggests the application of voltage source type forced commutation converter (VSFC) to an HV DC system. To ensure the promising characteristics of overall system, more investigation is, of course, necessary. We have been investigated performance of DC transmission into remote load-only system without AC source by means of computer simulation. In many runs of simulation program of HV DC system using VSFC, we noticed that long sutaining oscillation of DC line current and DC voltage occurs when large disturbance is applied. And the performance is worse when series DC reactance (DCL) is installed to suppress higher harmonics of DC line current. For improving the performance of HV DC system using VSFC, we investigated to install the L-R parallel damper circuit in series of DC transmission line. Simulation results when DCL and L-R damper are installed in series show that suppression of higher harmonics is as effective as installation of DCL only and the damping of oscillation is also substantial to improve the dynamic performance of whole system.