Rms transducer and voltage regulating system employing the same

Abstract

A voltage regulating system for an AC electrical power system includes a reactive converter having fixed capacitors and fixed inductors. Static switching devices are provided and include gating circuits for controlling the conduction angle of the switching devices so as to control the magnitude of the reactive current traversing the fixed inductors. RMS transducer circuitry is provided for generating an electrical signal representative of the RMS value of the voltage waveform at a critical point in the AC power system at which good voltage regulation is desired. Circuitry is provided for generating an electrical signal representative of a desired RMS value. Comparison components are provided for comparing these two electrical signals and generating an output signal for use in controlling the conduction angle of the switching devices so as to regulate the magnitude of the voltage waveform at the critical point in the AC power system. The RMS transducer circuitry employs a squaring function for generating a signal representative of the squared value of the voltage waveform. The RMS transducer circuitry also employs the positive and negative zero crossings of the waveform in combination with integrating components for operating on the squared value of the waveform for generating a signal representative of the squared RMS value of the waveform. Additional signal processing components provide an output signal therefrom which is representative of the RMS value of the voltage waveform over its last complete cycle. In one preferred embodiment, the value of the RMS over the last complete cycle of the voltage waveform is completely updated after each one half cycle. In this preferred embodiment, even and/or odd harmonics in the voltage waveform present no difficulties.