Modeling and characterization of operating modes of a self-excited induction generator for micro-hydropower applications

Abstract

This paper investigates the static and dynamic operating modes of a self-excited induction generator (SEIG) used in autonomous micro-hydropower plants (Micro-HPPs). A dq-axis saturation-aware model is formulated to capture voltage build-up, steady-state regulation under load variations, and speed perturbations associated with turbine head fluctuations. The model couples the machine equations with the excitation capacitor bank and load to determine the operating point. For the static regime, we present an iterative algorithm that solves for terminal voltage, frequency, reactive power balance, and torque–speed characteristics using both the classical equivalent circuit and a saturation coefficient to emulate the nonlinear magnetization curve. For the dynamic regime, time-domain simulations examine voltage build-up transients, load steps, and rotor-speed disturbances; key metrics include settling time, voltage regulation, frequency deviation, and power-factor response. A 0.75-kW, ~1000-r/min laboratory SEIG is used as a reference case. Results show that inclusion of magnetic saturation improves torque prediction by 5–8% in the moderate-load region and that combined LC compensation can reduce steady-state voltage deviation under 20–80% load from ~10–12% to ~3–5% without active electronics. The study provides design charts (capacitance vs. speed, voltage regulation vs. load) and practical sizing guidelines for Micro-HPP deployment in weak-grid or off-grid contexts.