AC power supply apparatus and methods providing output control based on estimated instantaneous reactive power

An AC power supply, comprising:

• an output;
• means for generating a reference signal representative of a desired voltage waveform at a node connected to the output;
• means for generating a compensated reference signal from the reference signal responsive to an estimate of instantaneous reactive power transferred between the output and the node;
• and
• means for controlling current transfer between a power source and the node via the output responsive to the compensated reference signal.

An uninterruptible power supply (UPS), comprising:

• a DC voltage generating circuit configured to connect to an AC power source and to an auxiliary power source and operative to produce a DC voltage circuit at a DC bus from the AC power source and/or the auxiliary power source;
• a controlled inverter coupled to the DC bus and operative to produce an AC voltage at an output thereof from the DC voltage on the DC bus responsive to a signal applied to a reference input of the controlled inverter;
• a reference signal generator circuit operative to generate a reference signal representative of a desired voltage waveform at a node connected to the output of the controlled inverter;
• a power determiner circuit operative to generate an estimate of instantaneous reactive power transferred between the output of the inverter and the node;
• and
• a reference signal compensator circuit responsive to the reference signal generator circuit and to the power determiner circuit and operative to generate a compensated reference signal at the reference input of the controlled inverter from the reference signal responsive to the estimate of instantaneous reactive power.

A method of operating an AC power supply, the method comprising:

• generating a reference signal representative of a desired voltage waveform at a node connected to an output of the AC power supply;
• modifying the reference signal responsive to an estimate of instantaneous reactive power transferred between the output and the node to generate a compensated reference signal;
• and
• controlling current transfer between the output and the node responsive to the compensated reference signal.