Solid - State On Load Tap - Changer for Transformer Using Microcontroller

The on-load tap changing (OLTC) regulators have been widely used since the introduction of electrical energy. They ensure a good regulation of the output voltage in presence of large variations of the input voltage with typical response time from several mili-seconds to several seconds. Earlier mechanical type of on load tap changers were into practice. But they had considerable limitations and drawbacks like arcing, high maintenance, service costs and slow reaction times. In order to overcome these limitations and drawbacks electronic (or solid-state) tap-changers were developed. The continuous growth of power semiconductor devices, such as the insulated gate bipolar transistor (IGBT), triac, thyristor, has allowed the development of quick operating OLTC regulators which is also helpful in fixing other problems in the ac mains, like flicker and sags. The major idea in the solid-state-assisted tap changer is that solid-state switches with more controllability, operates during the tapchanging process instead of mechanical switches which helps in reducing the arcing phenomena during the tapchanging process. In this paper implementation of a fast OLTC regulator is presented. The control strategy is Microcontroller-based, ensuring flexibility in programming the control algorithms. The experimental results demonstrate that the fast OLTC is able to correct several disturbances of the ac mains besides, the long duration in variation in time is much lower than the one corresponding to the traditional regulators.