Matrix converter application to FACTS and embedded generation
Power electronics is the key technology for connecting flexible ac transmission system devices and renewable power generation to the ac grid. Among the ac to ac converters, the matrix converter represents a promising alternative power electronics technology to back to back converters. It does not incorporate any storage elements which minimises the size and weight of the converter. In addition, with the introduction of the reverse blocking insulated gate bipolar transistor, its efficiency can surpass that of back to back converters. A new approach in controlling the matrix converter output current is introduced. The approach depends mainly on logic circuitry and facilitates power system applications using the matrix converter. Furthermore, it can provide sinusoidal output current under asymmetry voltage conditions. The output current quality is at the expense of the input current in this case. Both sinusoidal input and output currents cannot be achieved under asymmetry voltage conditions due to the lack of any storage elements. Matrix converter suitability to power system applications such as flexible ac transmission and embedded generation, is investigated particularly under asymmetrical ac supply conditions. The effect of the absence of an intermediate storage element, on the output power and current quality is considered. The utilization of the proposed control technique in a unified power flow controller, which is the most versatile flexible ac transmission system device, is investigated. The restriction on unified power flow controller operation due to the absence of any intermediate storage element in the matrix converter is also studied. Special attention is given to asymmetry ac voltage condition effects and how to mitigate this problem for embedded generation. Extraction of the positive and negative sequence components is essential in obtaining non-oscillatory output power, and a dual current controller is used to this end.