GB830624A - Improvements in or relating to the production of a control value dependent on the deviations of power and frequency from their reference values in an alternating-currentsystem - Google Patents

Abstract

830,624. Automatic control systems for power and frequency. PATELHOLD PATENTVERWERTUNGS & ELEKTROHOLDING A.G. April 17, 1957 [April 18, 1956], No. 12547/57. Class 38 (4). In an arrangement for producing a control value depending on the deviation from a reference value of the power and frequency in an A.C. system, the power is represented by the frequency of an auxiliary voltage, this frequency and the system frequency being counted and compared with reference numbers. The differences are used to produce the control value. Each frequency is separately fed through a circuit such as that of Fig. 1, which is for the system frequency. The two circuits operate intermittently and alternately. The input frequency (e.g. 50 c/s.) is multiplied at V and the output (e.g. 50 kc/s.) fed to a counting circuit R which produces a single pulse output after 50,000 cycles. At N a stable oscillator (e.g. 100 kc/s.) feeds a divider T which produces a pulse output after 1 sec. The time and frequency count pulses are applied to a discriminator D and the difference output, representing frequency error, is applied to gating circuits W+ or W - according to sign. Also applied to these circuits is a train of pulses from variable frequency divider K so that the number of pulses in the gated output at either Z + or Z - represents frequency error. In Fig. 2 the train of pulses is applied to circuit elements Sf or Sp (for the frequency representing power) comprising pulse formers, amplifiers and lowpass filters. The output levels are set by resistors Wf, Wp and the channels give a combined D.C. output at C. Also added at C is a component proportional to the integral control function of the sum of the errors. The output at C is the required control value, which may be used in the control of turbines.