An independent active and reactive power control of an isolated asynchronous generator in 3-phase 4-wire applications

This paper deals with an investigation on a controller, which regulates the voltage and frequency of an isolated asynchronous generator (IAG) driven by an uncontrolled pico hydro turbine to feed 3-phase 4-wire loads. The proposed controller is having capability to regulate the voltage and frequency in decoupled manner. A STATCOM (static synchronous compensator) is used to control the reactive power to regulate the voltage, while frequency regulation is achieved by active power control through an electronic load controller (ELC). The voltage regulator (VR) consists of an IGBT (insulated gate bipolar junction transistor) based three single-phase voltage source converters (VSCs), which are connected to each phase of the generator through three single-phase transformers. An advantage of this three-phase four wire topology is that DC link voltage can be maintained at optimum level. Frequency regulator (FR) consists of a diode bridge rectifier with a chopper switch and an auxiliary load. The proposed controller with an IAG system is modeled and simulated in MATLAB using power system block set (PSB) and Simulink toolboxes. Simulated results have demonstrated that proposed voltage and frequency controller for an IAG driven by uncontrolled pico hydro turbine offers the functioning as a harmonic eliminator, a load balancer and a neutral current compensator.