On Load Tap Changer of Transformer using Microcontroller

On-load tap-change transformers (OLTCs) are widely used since the introduction of electric power. They provide good control of the output voltage in the presence of large variations of the input voltage with a typical response time of a few milliseconds to a few seconds. An earlier mechanical type of load tap changers was in practice. But they had significant limitations and disadvantages, such as arcs, high maintenance, service costs and slow response times. To overcome these limitations and disadvantages were electronic (or solid state) tap changers developed. The continuous growth of power semiconductor devices, such as the bipolar transistor with isolated gate (IGBT), triac, thyristor, has made the OLTC rapid-action transformer development possible, which is also useful in correcting other problems in the power line, such as flicker and sags. The main idea in the solid state assisted tap changer, is that semiconductor switches operate with more controllability during the tap change process instead of mechanical switches, which helps in reducing the arcing phenomena during the tap-changing process. This project presents the implementation of a fast OLTC transformer. The control strategy is based on the microcontroller and provides flexibility in the programming of the control algorithms. The experimental results show that the switch under fast OLTC is able to correct various distortions of the AC. In addition, the long duration in the time difference is much smaller than that corresponding to the traditional transformer.