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SUMMARYThis paper presents a new concept for back-to-back (BTB) dc systems. The main feature of the proposed BTB is referred to as massively parallel. This massively parallel BTB system consists of a number of small-or mediumcapacity inverter units that are connected in parallel. The concept of transmission power control using the massively parallel BTB is investigated using MATLAB for a case where a fault occurs. In addition, a method for modeling the proposed BTB in EMTP is investigated. The work presented in this paper shows that the proposed BTB system is very promising for large power system applications because the losses of the system are very small compared to conventional BTB using VSC (voltage source converter). The massively parallel BTB can keep operating even if an inverter unit fails, thus improving overall power transmission capability. © 2001 Scripta Technica, Electr Eng Jpn, 138(3) : 3442, 2002

We have newly developed an 80MVA GCT STATCOM for the Kanzaki substation of the Kansai Electric Power Co., Inc. It has been started commercial operation in June, 2004. The main purpose of the STATCOM is to maintain voltage during single circuit connection of source to the substation resulting from an AC system fault in order not to break down load system of the substation. The developed STATCOM has three distinctive features: (1) a high-efficient, compact and AC filter-less system using multistage three-level GCT converter and customized PWM; (2) a coordinated voltage regulator with tap control of main transformers; and (3) a continuous operation from a single phase-ground fault through reclosing of the faulted circuit by limiter adjustments of the reactive current reference. This paper describes characteristics of the coordinated voltage and validity the continuous operation during AC system faults using data of commercial operations and the simulation results.

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