Decoupled Voltage and Frequency Controller for Isolated Asynchronous Generators Feeding Three-Phase Four-Wire Loads

This paper deals with a decoupled voltage and frequency controller (DVFC) for an isolated asynchronous generator (IAG), also known as the self-excited induction generator (SEIG), used in constant power applications such as pico hydro uncontrolled turbine driven IAG for feeding three-phase four-wire loads. The proposed controller is used to control the voltage and frequency at the generator terminal independently. The proposed decoupled controller is a combination of a STATic synchronous COMpensator (STATCOM) for regulating the voltage and an electronic load controller (ELC) for controlling the power which in turn maintains the system frequency constant. The STATCOM is realized using a 4-leg insulated gate bipolar transistor (IGBT)-based current controlled voltage-sourced converter (CC-VSC) and a self-supporting dc bus, while the ELC consists of a three-phase diode bridge rectifier, a chopper switch and an auxiliary load. The proposed generating system is modeled and simulated in MATLAB along with Simulink and power system blockset (PSB) toolboxes. The simulated results are presented to demonstrate the capability of an isolated generating system for feeding three-phase four-wire loads with the neutral current compensation.