On-load tap changing (OLTC) regulators are widely used to maintain a constant voltage. However, the typical response time of an OLTC varies from 100 ms to several seconds. The development of modem power devices allows to implement new types of OLTC regulators with a faster response in order to correct other perturbances like flicker, noise and 0-7803-5692-6/00/$10.00 (c) 2000 IEEE
The main function of the on-load tap changing (OLTC) regulators consists in maintaining a constant voltage in order to feed critical loads despite the load changes or voltage changes in the ac mains. The traditional regulators are still used nowadays, but present several disadvantages, like a slow response, which reaches from 100 ms to several seconds. These drawbacks can be overcome if the OLTC regulators would have shorter response time, commuting several times every cycle of the mains. There are two basic topologies for fast OLTC regulators, the first one consists of several taps and uses hard switching. The second one consists of two main switches commuting at high frequency, using soft-switching in order to reduce the power losses. The present topology is of the second type. This paper presents a mathematical model of the power stage of the proposed regulator. It includes the parasitic resistances and the leakage inductances in order to obtain a better comprehension of the regulator operation. A parametric analysis has been done in order to observer the influence of the parasitic elements in the performance of the main parameters of the topology.
The on-load tap changing (OLTC) regulators have been widely used since the introduction of electric energy. They ensure a good regulation of the output voltage in presence of large variations of the input voltage with typical response time from 100 ms to several seconds. On the other hand, the continuous growth of power semiconductor devices, such as the Insulated Gate Bipolar Transistor (IGBT), permits the development of Fast OLTC Regulators, being able to fix other problems in the ac mains, like the sags, flicker and harmonic distortion. This paper reports the design and implementation of a Fast OLTC Regulator, including the power and control stages, and presents several experimental results.
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