Interior structure of UPQC‐type QCC at the low‐voltage side in the FRIENDS

Abstract

SUMMARYRecently, the worldwide deregulation of the electric power industry is progressing. Further, it is expected that a many distributed generation facilities and energy storage systems will be installed at the end point of the power systems. Therefore, the future power system must be able to cope with these various qualities of power in the deregulated situation. The authors have proposed the FRIENDS (Flexible, Reliable, and Intelligent ENergy Delivery System) concept as a new distribution system that copes with a new framework of the electric power business in the near future. The most typical aspect of FRIENDS is the introduction of new equipment; Quality Control Centers (QCC) between distribution substations and customers. In this paper, the authors propose a concrete interior structure and investigate some control methods for realizing unbundling power quality supply and power conditioning using the proposed UPQC-type QCC. The effectiveness of the proposed method is confirmed through the instantaneous value analysis using PSCAD/EMTDC.

Reliability evaluation considering customized power quality supply in FRIENDS

“…In a system supply failure, power from the DG is supplied preferentially to the high-quality loads, and any excess power is allocated to standard-quality loads. In addition, in the UPS-type QCC [5] and UPQCtype QCC [6] assumed in this study, two AC/DC converters are installed on the QCC low-voltage side with their DC circuits connected to the DG. Here, however, the influence of the converters on supply reliability is ignored for simplicity.…”

“…As regards network switching, in the conventional system, several seconds to several minutes is required until recovery, for example, by means of reclosure. On the other hand, in FRIENDS, switching can be completed within 100 ms [6] by using information exchange between the QCCs over communication lines, and high-speed static circuit breakers. As regards short-term failures related to DG switching, the DG start-up time must be considered.…”

“…A high-voltage distribution line with a cross section of 100 mm 2 and a capacity of 250 A is assumed [6,7]. The highest power at a voltage of 22 kV is calculated in the following way:…”

“…Here a line cross section of 325 mm 2 [6] and a capacity of 400 A [7] are assumed. The highest power at 400 V is that is, 280 kW.…”