DESIGN AND TESTING OF ELC FOR HYDRO POWER PLANT

Abstract

This dissertation work includes the designing and testing of electronic load controller. As we all know that the exploitation of renewable energy sources to augment power generation as a necessity is an established fact, in remote areas where such sources mainly exists establishment of grid has been found to be uneconomical and not feasible. Therefore a standalone autonomous unit to feed local consumers using such renewable energy sources is the choice -left but this power generated is directly feed to the consumers if there is a variation in the load then it will affect the generator/turbine and other equipments connected to them. To solve this problem number of sophisticated control system are available in power application but they are expensive and inappropriate for small hydro. One solution concept which is widely adopted is the load controller. Load controller maintains the generator output voltage and frequency, irrespective of the amount of load connected to the generator. It does it by automatically dissipating any surplus power produced by the generator in additional load known as ballast load. The operating point of the generator is fixed such that it gives rated output at the rated conditions of voltage, current and speed. Now the variation in the consumer load connected is neutralised by the controller diverting the extra power to a dump load. In this dissertation work the power delivered to a load is regulated by phase angle regulation technique. For phase angle regulation, we used triacs and thyristors as power element. Thyristors can conduct only in one direction so two thyristors would be needed to steer one dump load. These electronic devices can be switched on by a short trigger pulse on their 'gate' connection and then remain conducting for the remainder of that half period. By then, generator voltage drops to zero, current through the dump load and triac or thyristor drops to 0 and they stop conducting or 'extinguish' by themselves. In this scheme, the principle of phase angle control of back to back thyristor is used. A thyristor is fired at a specific delay angle relative to the zero voltage crossing of the sine wave. The thyristor commutates at next zero crossing. Switching occurs a twice the frequency and generates total harmonic distortion as high as 35-40% in current with added reactive power burden. This scheme can continuously vary the dump power over nearly the entire range from zero to full load as the delay angle varies from 180 to 0 degree