Efficiency Enhancements to a Linear AC Voltage Regulator: Multiwinding Versus Multitransformer Design

Electricity distribution companies are required to supply electric power, which conforms to accepted standards, that place limits on voltage fluctuations beyond nominal values. However, it is common for these fluctuations to exceed the specified standards. One solution to this problem is to install stand-alone root mean square (RMS) voltage regulators at the consumer site. Commonly available ac regulators typically have limitations such as slow response time, flattened sine wave output, low efficiency, and limited operating range. The linear ac voltage regulator is a relatively new type of solid-state, single-phase ac regulator for consumer-end, which addresses most of the above-mentioned issues. It is based on a series transistor-array coupled with a line-frequency transformer that works seamlessly from boost-to buck-mode in the range of 0.8-1.1 per-unit values of line voltage, without a need of any transformer configuration changes. However, previous prototypes exhibited reduced efficiency when the line voltage exceeded the nominal value. This article presents two alternative designs that achieve efficiencies of 90-95%, usually required in commercial implementation. Analytical and experimental results of a multiwinding versus multitransformer-based prototypes of 300 VA output capacity are presented.