Patent GB-1032194-A (GB)
Title: Equipment for regulating the power transmitted between interconnected alternating current networks
IPC: H02J3/36
Filed: 1963-03-26
Abstract: 1,032,194. Automatic control of power. ALLMANNA SVENSKA ELEKTRISKA A.B. March 26, 1963 [April 3, 1962],No. 11850/63. Heading G3R. [Also in Division H2 Equipment for regulating the power transmitted between two A.C. networks 1, 2, which networks each comprise a load 3, 5 and a power generator 4, 6, which determine the frequency of the network, and which networks are connected together via a link which permits the frequencies of the networks to be varied independently of one another, said link comprising two interconnected converters 7, 8 each connected to one network, is characterized in that at least one of the converters is provided with a regulator 9 which controls the power transmitted by the link under the influence of a time operand of the relative difference in frequency between the two networks. By relative difference in frequency is meant f 1 /f 10  - F 2 /F 20  where f 1 , f 2  are the actual and f 10 ,f 20  are the desired frequencies. By time operand is meant the quantity itself, its integral value, its derivative, or any quantity derived by a time operator. Preferably the link is for direct current transmission, and Fig. 2 shows the converter 7 and control features in greater detail. Single phase equipment is shown, although polyphase working is also envisaged. Converter equipment comprising a transformer 11 and rectifying valve 15 rectifies the frequency f 1 , providing D.C. which is transmitted through the link and choke 14 to the converter 8 and thence to the network 2. The frequencies f 1 , f 2  are also fed to a comparator 35 (if necessary this may be effected by radio link, or carrier frequency on the D.C. line), providing a D.C. signal representative of the relative frequency difference which signal is fed across a resistor 42 to an amplifier 28. The amplified output is fed to a control pulse generator 24 (e.g.a transistor flip-flop circuit) and varies the phase of these pulses which are supplied to control grids 19, 20 so that in consequence the output (i.e. transmitted) power of the converter is dependent on the relative frequency difference. In addition an arrangement for providing automatic regulation of the transmitted power is provided. A measure of the current flowing is derived through a transducer 18 and applied to a Hall device 39. A measure of the voltage is derived across a winding 40 of the Hall device and the output of the Hall device which is a measure of the power is compared with a reference voltage 32 by means of resistors 29, 30, the error signal being applied to the amplifier 28. A capacitor 67 enables the integral of the error signal also to be applied to amplifier 28. Limitation to a maximum permissible transmission current is provided by a transductor 17 providing a signal which is added to a reference signal 46 and applied to the amplifier 28. If large enough this signal over-rides the other signals. The comparator 35 may be a pair of synchronous motors each feeding a D.C. generator, these generators being connected in series opposition and arranged so that the D.C. output is a measure of the relative frequency difference or the integral of this (Figs. 3 and 4, not shown).