Method and apparatus to solve PFC capacitor reduction of line AFLC ripple without passive filters
Audio Frequency Load Control (AFLC) signal processing electronics added to a power factor correction (PFC) unit allowing the AFLC system to operate without the need of large and heavy passive bypass or blocking filters at the PFC installations. The AFLC signal processing electronics a first group of additional electronics tuned to the AFLC frequency for detecting the AFLC carrier signal; and a second group of additional electronics for driving an AFLC impedance switch that is connected in parallel with an AFLC impedance. The AFLC impedance is connected in series with the PFC capacitors, and is sufficiently large to offer significant impedance in series with the PFC capacitors that allows the AFLC signal to bypass the PFC unit.
1. An apparatus for Audio Frequency Load Control (AFLC) in an electrical power distribution network installed with a power factor correction (PFC) unit, comprising:
a first electronic circuitry for detecting one or more AFLC carrier signals in the electrical power distribution network mains load current and/or voltage waveform at an input of the first electronic circuitry;
a second electronic circuitry for receiving an output of the first electronic circuitry indicating a presence or absence of AFLC signal and driving a AFLC impedance switch;
the AFLC impedance switch connected in parallel with an AFLC impedance;
the AFLC impedance connected in series with one or more PFC capacitors in the PFC unit, wherein the AFLC impedance being sufficiently large to allow an AFLC signal to bypass the PFC unit when switched in;
wherein the AFLC impedance switch being opened during the presence of AFLC signal, as such switching in the AFLC impedance.
2. The apparatus of claim 1 , wherein the first electronic circuitry comprising:
an amplifier for amplifying the AFLC carrier signal;
a tuned filter for filtering the amplified AFLC carrier signal and being tuned to the AFLC carrier signal frequency; and
a phase lock loop for suppressing signal noise in the filtered and amplified AFLC carrier signal and indicating the presence of AFLC carrier signal.
3. The apparatus of claim 1 , further comprising a current transformer (CT) for measuring the electrical power distribution network mains load current waveform to be fed to the first electronic circuitry.
4. The apparatus of claim 1 , wherein the AFLC impedance comprising a resistor.
5. The apparatus of claim 1 , wherein the first electronic circuitry, the second electronic circuitry, and the AFLC impedance switch comprising fast response electronic components such that the AFLC impedance is switched in within 50 milliseconds from detection of a start pulse of an AFLC signal.
6. The apparatus of claim 1 , wherein the first electronic circuitry further comprising:
one or more filters for filtering the AFLC carrier signals and being tuned to the AFLC carrier signal frequency;
a multiplexer for selecting the filtered AFLC carrier signals;
an analog to digital converter for converting the selected AFLC carrier signal into digital signals; and
a signal processor for sampling and transforming the digitized AFLC carrier signals into frequency domain to identify frequency components of the AFLC carrier signals.