Real-time analysis of voltage and frequency regulation of self-excited induction generator based micro hydro plant using generalized impedance controller

Abstract

– The self-excited induction generator (SEIG) is well accepted for application in micro hydropower plants. However, in the edge-of-grid application it exhibits a limitation in its capacity to sustain the desired terminal voltage along with the frequency of variations in the prime mover's speed and load. Terminal voltage and frequency regulation are significant concerns for such schemes, and many such techniques are available to regulate the same. This paper presents a closed-loop control technique based on a generalized impedance controller (GIC) responsible for the impedance-controlled functioning of the pulse width variation voltage source converter (PWM-VSC) to regulate frequency and terminal voltage of machine with various loading conditions. A coupling transformer is connected between GIC and SEIG, and the ratings of GIC and transformer should be the same as SEIG, as GIC must compensate for the entire SEIG output. Three phase, 2.2 kW, 415 V, 4.8 A, 50 Hz SEIG, and a three IGBT-based voltage-sourced inverter with coupling transformer, are modelled in MATLAB environment. SEIG frequency and voltage effects in response to the GIC modulation index and phase angle are investigated in the real-time environment using the OPAL-RT (ver. OP4510) environment. The voltage and frequency are controlled using the proposed SEIG-GIC scheme, and the simulation results achieved from MATLAB/Simulink were validated with real-time observations.

Keywords

• Self-excited induction generator
• Phase lock loop
• Generalized impedance controller
• Voltage source converter
• Proportional-integral