Fast acting linear AC voltage regulator for consumer applications: Implementation options

RMS line voltage fluctuation is a very well-known problem in AC power conditioning. Traditional techniques to handle this power quality issue are (i) motor-driven variacs, (ii) ferro-resonant regulators, (iii) transformer tap changers, (iv) solid-state regulators. Each of these techniques has disadvantages such as (a) flattened-top output and low efficiency, (b) bulky and slow response, (c) switch change-over related issues, (d) output waveform distortion due to RFI/EMI respectively. Linear AC regulator technique covered under a new US patent is a fifth method to solve this RMS voltage fluctuation issue, based on a power semiconductor array. One disadvantage was the low efficiency when the input line voltage exceeds the nominal value. While developing a 2kVA commercial prototype, the authors were able to come-up with two cost-saving design options by using (i) two smaller low-cost transformers combined in series and a (ii)multi-winding transformer with two primaries combined in a novel topology. This paper discusses the design concepts and implementation aspects of these new techniques, comparing their unique advantages as opposed to a single buck-boost transformer.