VSCF induction generation in stand-alone micro-hydro generating systems

Small-scale hydroelectric power generation is contributing substantially to the conservation of oil and fossil fuels and the prevention of deforestation in the mountainous areas of Nepal and Northern Pakistan. Villages can be electrified and tourist hotels powered from renewable energy. The main factors that determine generating potential are the flow rate and head of water. Generally the head remains fairly constant but the flow rate depends upon seasonal factors. Flow rate variations tend to be seasonal, day to day fluctuations being significant only in extreme weather conditions. Most installations are stand-alone because of the geographical remoteness, but the severe transient conditions of wind-generation systems are unlikely to be encountered. A cage-induction generator offering robustness and virtually maintenance free operation has great potential for micro-hydro systems if stable operation can be achieved. This paper describes and contrasts the strategies used by the present authors for induction generator stabilisation