Dynamic voltage sag correction

A method for correcting a voltage sag condition, comprising the steps of:

• (a) connecting an AC load to a source of AC line voltage;
• (b) storing energy from the AC line voltage;
• (c) detecting a voltage sag condition wherein a voltage level of the AC line voltage drops below a selected low line voltage threshold level and detecting a termination of the voltage sag condition;
• and
• (d) providing an AC output voltage signal to the AC load at approximately a pre-voltage sag condition voltage level by adding the stored energy to the AC line voltage in response to the detection of a voltage sag condition and terminating the providing of the AC output voltage signal to the AC load in response to the termination of the voltage sag condition.

A dynamic voltage sag corrector, comprising:

• (a) input terminals;
• (b) output terminals;
• (c) a power conversion and storage module connected between the input terminals and the output terminals, wherein the power conversion and storage module includes an energy storage device and an inverter responsive to inverter control signals to provide an AC signal from energy stored in the energy storage device;
• and
• (d) system controller means for detecting a voltage sag condition when an AC line voltage signal provided to the input terminals drops below a selected low line voltage threshold level, for providing inverter control signals to the inverter to control the inverter to provide an AC output voltage signal at approximately a pre-voltage sag condition voltage level to the output terminals in response to the detection of a voltage sag condition, for detecting a termination of the voltage sag condition when the AC line voltage signal returns to approximately a pre-voltage sag condition voltage level, for terminating the providing of inverter control signals to the inverter in response to the detected termination of the voltage sag condition, and for limiting a duration for which inverter control signals may be provided to less than a selected maximum operating duration.

A method for correcting a voltage sag condition, comprising the steps of:

• (a) connecting an AC load to a source of AC line voltage;
• (b) detecting a voltage sag condition wherein a voltage level of the AC line voltage drops below a selected low line voltage threshold level and detecting a termination of the voltage sag condition;
• (c) controlling an inverter to provide an AC output voltage signal to the AC load at approximately a pre-voltage sag condition voltage level in response to the detection of a voltage sag condition and terminating the providing of the AC output voltage signal to the AC load in response to the termination of the voltage sag condition;
• and
• (d) limiting the controlling of the inverter to provide the AC output voltage signal to less than a selected maximum operating duration.

A dynamic voltage sag corrector, comprising:

• (a) input terminals;
• (b) output terminals;
• (c) a power conversion and storage module connected to provide an AC signal in series between the input terminals and the output terminals, wherein the power conversion and storage module includes a rectifier connected to the input terminals for rectifying power available at the input terminals, an energy storage device for storing the rectified power, and an inverter responsive to inverter control signals to provide an AC signal from energy stored in the energy storage device in series between the input terminals and the output terminals;
• (d) an additional switching device connected in parallel with and between the rectifier and the storage device and responsive to an additional switching device control signal;
• and
• (e) a system controller means for providing inverter control signals to control the inverter to provide an AC output voltage signal to the output terminals and for providing the additional switching device control signal to close the additional switching device if there is a break in an AC line voltage signal provided to the input terminals.