Design of Thin AC Converters (TACCS) using Dual Virtual Quadrature Source Concept

Abstract

Conventional grid control has been based on static assets that are switched in or out for a considerable long time. Traditionally excitation control of generators has provided continuous control in the grid system. Recently, dynamic grid control has been achieved by the use of FACTS devices, i.e. TCR, STATCOM and UPFC, etc. These FACTS devices are expensive and reliability, maintainability are the main problems. For STATCOM devices, the need to provide continuous VAR support in the presence of asymmetrical system faults, dictates the energy storage needed to provide the desired VAR injection. This has the drawback of high customization, high cost and duplication of basic asset functionality therefore the existing grid assets remain ‘dumb’ and the cost would not be effectively reduced. A STATCOM is required at system fault that causes the system to potentially unstable boundaries produces maximum stress on the grid, and non-availability of the dynamically controllable asset can results in a potential catastrophic cascading failure. Due to the above drawbacks conversion of existing ‘dumb’ grid assets into ‘smart and controllable’ assets is required. This can be achieved by the concept of Thin AC Converters (TACC), which can result in significant cost reduction and increased system reliability. The technique is scalable to high power levels using Multi- Level AC Converter. TACCs can convert shunt VAR capacitors into STATCOMs, and can use load tap changing transformers for controlling network voltages and currents.

Keywords: AC Converter, compensating capacitor, IGBT, Mat Lab