Phase angle function generator for static var control

Abstract

A reference timing generator for a phase locked loop including a phase comparator, a filter, and a VCO. The basic generator utilizes a prefilter in conjunction with a squaring circuit which provides a signal concurrently to a ripple cancelling digital phase detector and a lock-in monitor. The outputs of the last two apparatus are provided to a dual mode amplifier filter. The output of the amplifier filter is provided to a voltage controlled oscillator which provides a signal frequency which is related to the input signal. Reference timing generator signals are provided in one embodiment of the invention to a discretely varying function generator for calculating a thyristor firing angle (.alpha.). The function generator provides an analog signal related to a desired function (.pi./2 - .alpha. - 1/2 sin 2 .alpha.) for utilization in a static VAR generator control circuit. The function generator utilizes switched parallel resistors and a capacitor to generate the required function. In another embodiment, reference timing generator signals are provided to a read only memory. The digital output of the read only memory is provided to a digital to analog converter. The output value of the digital to analog converter which is additionally related to an applied reference signal is provided to a filter for smoothing. The output of the filter provides the desired function.