High speed power factor controller

A power factor correction system comprising:

• a voltage sensor having an input coupled across a first and second alternating current power lines;
• a current sensor having an input coupled to one of said first and second power lines;
• a digital microprocessor;
• circuitry for coupling signals from said voltage sensor to said microprocessor;
• circuitry for coupling signals from said current sensor to said microprocessor:
• said microprocessor including programming means for determining a phase difference between a sensed voltage and a sensed current;
• incrementally adjustable power factor correction circuitry absorbing current from said power line during a portion of each cycle of the alternating current and for supplying current to said power line during another portion of said cycle of the alternating current;
• switching circuitry including a plurality of switching devices, coupling said power factor correction circuitry to said power line;
• said microprocessor being coupled to said switching circuitry to change the state of said switching devices to change the power factor of said system toward unity;
• said microprocessor supplying updated switching signals to said switching circuitry at least several times each second;
• and
• said microprocessor further including first, second, third and fourth switching outputs responsive to said phase difference for applying said outputs to said switching circuitry.

A power factor correction system, comprising:

• a load having a variable reactive impedance;
• a source of alternating current (AC) power;
• alternating current power lines coupling said source of AC power to said load;
• a voltage sensor having an input coupled to said AC power lines;
• a current sensor having an input coupled to said AC power lines;
• a digital microprocessor;
• circuitry for coupling signals from said voltage sensor to said microprocessor;
• circuitry for coupling signals from said current sensor to said microprocessor;
• said microprocessor including programming means for determining a phase difference between a sensed voltage and a sensed current;
• incrementally adjustable power factor correction circuitry absorbing current from one of said power lines during a portion of each cycle of the alternating current and for supplying current to one of said power lines during another portion of said cycle of the alternating current;
• switching circuitry including a plurality of switching devices, coupling said power factor correction circuitry to said power lines;
• said microprocessor being coupled to said switching circuitry to change the state of said switching devices to change the power factor of said system toward unity;
• said microprocessor supplying updated switching signals to said switching circuitry at least once each second;
• and
• wherein said power factor correction circuitry is a capacitive network, including a plurality of capacitors, and said switching devices selectively couple said capacitors to the power line.

A method for correcting a power factor, in a power distribution system, having a load coupled thereto, comprising:

• monitoring a phase line voltage in the power distribution system;
• determining the cyclic period of said phase line voltage;
• monitoring a phase line current in the power distribution system;
• determining a phase difference between said phase line voltage and said phase line current;
• storing a current charge generated during one cyclic period of said phase line current;
• and
• rapidly releasing incrementally during another cyclic period of said phase line current, said current charge to the load coupled to the power distribution system;
• said releasing step being synchronized at a determined frequency to correct the power factor relative to said phase line voltage and said phase line current in the power distribution system.

A apparatus for correcting a power factor in a power distribution system having a load coupled thereto, comprising:

• monitoring means for sensing a phase line voltage and a phase line current in the power distribution system;
• programmable means for determining a phase difference between said phase line voltage and said phase line current;
• charge storage means responsive to said programmable means for storing a current charge during one cyclic period of said phase line current;
• and
• rapid switch means coupled to said charge storage means and responsive to said programmable means for rapidly releasing incrementally said current charge to the load during another cyclic period of said phase line current;
• said releasing of the stored charge being synchronized at a frequency determined by said programmable means to correct the power factor relative to said phase line voltage and said phase line current in the power distribution system.