A Zig-Zag Transformer and Three-leg VSC Based DSTATCOM for a Diesel Generator Based Microgrid

The distribution systems are facing severe power quality problems due to the uncontrolled use of different types of linear and non-linear loads such as solid state controllers which will draw harmonics and reactive currents from ac mains. It may lead to poor power quality at ac sources such as sag, swell, notch, flicker, unbalance etc. The installation of the diesel generator set is widely used in practice to feed power to some crucial equipments and in remote areas. DG sets used for these purposes may be loaded with unbalanced, reactive and non-linear loads such as power supplies in telecommunication system and medical equipments. A Zig-Zag Transformer and three-leg VSC based DSTATCOM is used here to compensate the neutral current, harmonic current, reactive power and unbalanced load. The insulated gate bipolar transistor (IGBT) based VSC is supported by a capacitor and is controlled for the compensation required in the load current. The dc bus voltage of the VSC is regulated during varying load conditions. In this paper, a Synchronous Reference Frame (SRF) controlled three-leg voltage source converter (VSC) based DSTATCOM with a Zig-Zag transformer is used for reactive power, harmonics, unbalanced load current and neutral current compensation in grid connected and islanded mode.