Bi-directional multi-frequency ripple control system

Claim 2

In a ripple control system for an alternating current electric power distribution system which comprises a transmitter for transmitting a code and a receiver for receiving said code, said transmitter being coupled to the electric power distribution system to superimpose a signal on the power frequency waveform as a sequence of waveform distortions, the improvements comprising: frequency control means to accurately generate closely spaced frequencies in the transmitter to enable the use of multifrequency codes, an input detector circuit in said receiver having two lock-in amplifiers driven ninety degrees out of phase with each other, means for squaring and summing the lock-in amplifier outputs to form a combined non-phase sensitive output, discrimination means comprising a microcomputer so coupled to the output of each said lock-in amplifier that a flag of the microcomputer is a threshold flag responsive to said lock-in amplifier combined non-phase sensitive output magnitude and two other flags thereof are responsive to zero crossings of each said lock-in amplifier output such that signal rejection occurs when (a) said signal magnitude is below a set threshold, and (b) when said magnitude exceeds that set threshold and the time between successive zero crossings of either said output is less than a set minimum.

Claim 3

Improvements in a ripple control system according to claim 1 further comprising a transmitter transformer, said transmitter being coupled by that transformer to the distribution system to derive power therefrom and generate signals by means of sequences of waveform distortions, a phase-locked loop multiplier synthesising the frequencies of said signals and locking those frequencies to the power frequency.

Claim 4

In a ripple control system for an alternating current electric power distribution system which comprises a transmitter for transmitting a code and a receiver for receiving said code, said transmitter being coupled to the electric power distribution system to superimpose a signal on the power frequency waveform as a sequence of waveform distortions, the improvements comprising: an inductance in series with a capacitance in said transmitter, a pair of thyristors connected in inverse parallel and arranged to be fired by a transmitter control unit in a pattern, a transformer also in said transmitter and coupling the signals generated by said firing to the power system, said transmitter being coupled by that transformer to the distribution system to derive power therefrom and generate signals by means of sequences of waveform distortions, a phase-locked loop multiplier synthesising the frequencies of said signals and locking those frequencies to the power frequency, said receiver comprising an input detector circuit having two lock-in amplifiers driven ninety degrees out of phase with each other, means for squaring and summing the outputs of those said amplifiers to forma combined non-phase sensitive output, and discrimination means comprising a microcomputer so coupled to each of said amplifiers as to logically examine zero crossings of the two said lock-in amplifier outputs as to produce rejection of incoming signals when the period between said zero crossings of either said output is less than a set minimum.

Claim 5

In a ripple control system for an alternating current electric power distribution system which comprises a transmitter for transmitting a code and a receiver for receiving said code, said transmitter being coupled to the electric power distribution system to superimpose a signal on the power frequency waveform as a sequence of waveform distortions, the improvements comprising: an inductance in series with a capacitance in said transmitter, a pair of thyristors connected in inverse parallel and arranged to be fired by a transmitter control unit in a pattern, a transformer also in said transmitter and coupling the signals generated by said firing to the power system, said transmitter being coupled by that transformer to the distribution system to derive power therefrom and generate signals by means of sequences of waveform distortions, a phase-locked loop multiplier synthesising the frequencies of said signals and locking those frequencies to the power frequency, said receiver comprising an input detector circuit having two lock-in amplifiers driven ninety degrees out of phase with each other, means for squaring and summing the outputs of those said amplifiers to forma combined non-phase sensitive output, and discrimination means comprising a microcomputer so coupled to each of said amplifiers as to logically examine zero crossings of the two said lock-in amplifier outputs as to produce rejection of incoming signals when the period between said zero crossings of either said output is less than a set minimum.

Claim 6

Improvements in a ripple control system according to a claim 3 wherein said inductance capacitance combination has a resonant frequency higher than said signal frequency and said transmitter control unit is arranged to fire the thyristors at the signal frequency resulting in gaps of zero current following each half cycle of oscillation current.

Claim 7

Improvements in a ripple control system according to claim 3 wherein said inductance capacitance combination has a resonant frequency higher than said signal frequency and said transmitter control unit is arranged to fire the thyristors at the signal frequency but comprises control means additionally controlling firing of the thyristors such that when a logic signal of the frequency of the electric power distribution system, but phase shifted from that frequency, is logic HIGH then oscillation current is continuous from the positive half cycle to the negative half cycle with a gap of zero current following the negative half cycle, and when such logic signal is LOW oscillation current is continuous from the negative half cycle to the positive half cycle with a gap of zero current following the negative half cycle.

Claim 8

Improvements in a ripple control system according to claim 3 wherein said inductance capacitance combination has a resonant frequency near said signal frequency and said transmitter control unit is arranged to fire the thyristors at the signal frequency, but said control unit additionally controls firing of the thyristors, such that when a logic signal of mains frequency, but phase shifted from the mains, is logic HIGH then oscillation current is continuous until the logic signal changes to LOW whereupon following the first positive half cycle of oscillation current a gap of zero current ensues for one full signal frequency period, and when said logic signal changes from LOW to HIGH then following the first negative half cycle a gap of zero current ensues for one full signal frequency period.

Claim 9

Improvements in a ripple control system according to claim 3 wherein said inductance capacitance combination has a resonant frequency near said signal frequency and said transmitter control unit fires the thyristors basically at the signal frequency but additionally controls firing of the thyristors, such that when a logic signal of mains frequency, but phase shifted from the mains, is logic HIGH then oscillation current is continuous from the positive half cycle to the negative half cycle with a gap of zero current for one full signal period following the negative half cycle, and when the logic signal is LOW oscillation current is continuous from the negative half cycle to the positive half cycle with a gap of zero current for one full signal period following the positive half cycle, with an extra oscillation half cycle immediately following each logic transition.

Claim 10

Improvements in a ripple control system according to claim 3 wherein said code transmitted by said transmitter comprises a START bit consisting of a signal frequency being transmitted for a set period of time followed by a set period of no transmission followed by the transmission of at least one CODE comprising the transmission of a second frequency for a set period of time.

Claim 11

Improvements in a ripple control system according to claim 6 wherein said code is identified by the START bit duration and frequency, period between START bit and the first CODE bit, and each CODE bit duration and frequency.

Claim 12

Improvements in a ripple control system according to claim 6 further comprising phase reversal means by which each said bit is terminated by reversing the phase of the transmitted signal for sufficient time to achieve a sharp cut-off in the received signal.

Claim 13

Improvements in a ripple control system according to claim 3 wherein said phase-locked loop frequency multiplier synthesises said frequency control means to control the lock-in amplifiers in the receiver and thyristor firing in the transmitter control unit, from the power mains frequency of the electric distribution system firstly by fixed frequency multiplication of the power frequency, and a variable divider divides the multiplexed fixed frequency to produce a plurality of control frequencies.

Claim 14

Improvements in a ripple control system according to claim 3 wherein said power distribution has a power supply end and consumer ends, said transmitter being at the power supply end and the signal being transmitted by said distribution system to a said consumer end as a voltage signal.

Claim 15

Improvements in a ripple control system according to claim 3 wherein said power distribution has a power supply end and consumer ends, said transmitter being at a said consumer end of said distribution system and the signal is transmitted by said distribution system to the power supply end as a current signal.

Claim 16

Improvements in a ripple control system according to claim 13 further comprising a current transformer and impedance at said power supply end isolating and transforming said current signal to a voltage signal which is directed into said receiver.

Claim 17

Improvements in a ripple control system according to claim 1 further comprising a transmitter transformer, said transmitter being coupled by that transformer to the distribution system to derive power therefrom and generate signals by means of sequences of waveform distortions, and a crystal controlled oscillator so coupled to the transmitter as to superimpose said signal on the power frequency waveform as a sequence of waveform distortions which are at a frequency derived from the crystal oscillator.

Claim 18

Improvements in a ripple control system according to claim 1 wherein said frequency control means to control the lock-in amplifiers in the receiver and the thryistor firing in the transmitter control unit is derived from respective crystal controlled oscillators generating a base frequency followed by a variable divider to produce a plurality of control frequencies.

Claim 19

Improvements in a ripple control system according to claim 4 further comprising an additional inductor in parallel with said inductance capacitance combination, said additional inductor cooperating with said inductance capacitance combination to control and increase the level of current oscillation in the circuit.