Dynamic voltage sag correction
First Claim
1. A dynamic voltage sag corrector, comprising:
- (a) input terminals;
(b) output terminals;
(c) a bypass switch connected between the input terminals and the output terminals and responsive to bypass switch control signals to open and close the bypass switch;
(d) a power conversion and storage module connected in parallel with the bypass switch between the input terminals and the output terminals, wherein the power conversion and storage module includes a rectifier 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 parallel with the bypass switch; and
(e) 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 a bypass switch control signal to the bypass switch to open the bypass switch in response to the detection of a voltage sag condition, 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 the voltage sag condition by adding a voltage level of the storage device to a voltage level of the AC line voltage signal, 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 providing a bypass switch control signal to the bypass switch to close the bypass switch in response to the detected termination of the voltage sag condition.
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Accused Products
Abstract
A low cost, small size, light weight, and highly effective system and method for providing dynamic power line voltage sag correction is provided. A dynamic voltage sag corrector includes a static bypass switch and a regulator/storage module connected together in parallel between input terminals and output terminals. Under normal operating conditions, the static bypass switch is closed, and a normal line voltage level is provided directly from the input terminals to the output terminals via the static bypass switch. When a voltage sag condition is indicated, the static bypass switch is opened, and the regulator/storage module is controlled to provide a near normal output voltage signal to the output terminals. The regulator/storage module includes a power conversion circuit which is controlled to provide the desired output voltage signal by adding a voltage level on storage capacitors to the available input line voltage signal. The components of the dynamic voltage sag corrector are selected to provide voltage sag correction for a duration sufficient to provide correction of 90-95% of voltage sag/drop conditions which are likely to be encountered. The size, cost, and weight of the dynamic voltage sag corrector is thereby reduced. The dynamic voltage sag corrector may also provide surge condition correction, may be configured to provide extended duration voltage sag correction to a priority portion of a load, may provide support to a load even if there is a complete break in an input power line, and may be employed in single or multi-phase applications.
166 Citations
64 Claims
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1. A dynamic voltage sag corrector, comprising:
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(a) input terminals; (b) output terminals; (c) a bypass switch connected between the input terminals and the output terminals and responsive to bypass switch control signals to open and close the bypass switch; (d) a power conversion and storage module connected in parallel with the bypass switch between the input terminals and the output terminals, wherein the power conversion and storage module includes a rectifier 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 parallel with the bypass switch; and (e) 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 a bypass switch control signal to the bypass switch to open the bypass switch in response to the detection of a voltage sag condition, 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 the voltage sag condition by adding a voltage level of the storage device to a voltage level of the AC line voltage signal, 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 providing a bypass switch control signal to the bypass switch to close the bypass switch in response to the detected termination of the voltage sag condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A method for correcting a voltage sag condition, comprising the steps of:
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(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. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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51. A dynamic voltage sag corrector, comprising:
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(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. - View Dependent Claims (52, 53, 54, 55)
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56. A method for correcting a voltage sag condition, comprising the steps of:
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(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. - View Dependent Claims (57, 58, 59, 60)
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61. A dynamic voltage sag corrector, comprising:
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(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. - View Dependent Claims (62, 63, 64)
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Specification