Method and apparatus for energy harvesting from a current source
An energy harvesting circuit for harvesting energy from a medium voltage power line. The energy harvesting circuit includes an input capacitor electrically coupled to the power line and storing power therefrom, and a flyback converter including a primary coil and a secondary coil. The harvesting circuit further includes a switching circuit electrically coupled in series with the primary coil and being operable to electrically connect and disconnect the input capacitor to and from the primary coil, where the switching circuit includes an input voltage regulation feedback circuit for regulating an input voltage provided to the switching circuit from the input capacitor. The harvesting circuit also includes an output capacitor electrically coupled to the secondary coil and the actuator, where the output capacitor is charged by the secondary coil when the switching circuit is closed to provide power to an actuator to close a vacuum interrupter.
1. An energy harvesting circuit for harvesting energy from a power line to provide power to an actuator to close a vacuum interrupter, the energy harvesting circuit comprising:
an input capacitor electrically coupled to the power line and storing energy therefrom;
a power converter including a primary coil and a secondary coil;
a switching circuit electrically coupled in series with the primary coil and the combination of the primary coil and the switching circuit being electrically coupled in parallel with the input capacitor, the switching circuit being operable to electrically connect and disconnect the input capacitor to and from the primary coil, the switching circuit including an input voltage regulation feedback circuit for regulating an input voltage provided to the switching circuit from the input capacitor, the input voltage regulation feedback circuit including an integrated circuit having a feedback pin, a first switch, a pulse width modulation (PWM) controller and a comparator, wherein when a feedback voltage provided to the feedback pin is below a reference voltage, a high signal is generated at an output of the comparator, which triggers the PWM controller to generate a PWM signal that turns on the first switch so that power is provided to the primary coil from the input capacitor, and when the feedback voltage at the feedback pin is above the reference voltage, the PWM signal is stopped; and
an output capacitor electrically coupled to the secondary coil and the actuator, the output capacitor being charged by the secondary coil when the switching circuit is closed to provide power to the actuator to close the vacuum interrupter, wherein the input voltage regulation feedback circuit further includes a first set of series-connected transient voltage suppression (TVS) diodes that are electrically coupled in parallel with the input capacitor and a second switch, the first set of series-connected TVS diodes controlling an input voltage regulation setpoint at the feedback pin to be equal to the series breakdown voltage of the first set of series-connected TVS diodes, wherein when the input voltage across the input capacitor is higher than the overall breakdown voltage of the first set of series-connected TVS diodes, the second switch will turn on which pulls down the feedback pin, which triggers the PWM controller.
2. The energy harvesting circuit according to claim 1 wherein the switching circuit further includes a second set of series-connected TVS diodes that have a lower breakdown voltage than the first set of series-connected TVS diodes and that is equal to a desired minimum value of the input voltage, and includes two optoisolator switches each having a phototransistor and an LED, wherein when the input capacitor is charged to a voltage higher than the sum of the breakdown voltages of the first set of series-connected TVS diodes, the phototransistor in one of the optoisolator switches conducts providing a path for current to flow in the LED in the other optoisolator switch, the phototransistor in the other optoisolator switch provides a latch for the LED in the one optoisolator switch, which drives the second switch.
3. The energy harvesting circuit according to claim 1 wherein the first and second switches are MOSFET switches.
4. The energy harvesting circuit according to claim 1 wherein the switching circuit further includes an output voltage regulation feedback circuit for regulating the output voltage on the output capacitor, the output feedback circuit including an optoisolated transistor coupled to the feedback pin, the optoisolated transistor including a bipolar junction transistor and an LED, wherein when the output voltage on the output capacitor begins to exceed a predetermined setpoint, the bipolar junction transistor will begin to conduct, which turns off the power transfer from the primary coil to the secondary coil by completely discharging the input capacitor.
5. The energy harvesting circuit according to claim 1 further comprising a voltage clamp circuit for controlling the output voltage of the output capacitor, the voltage clamp circuit including a MOSFET switch and a microcontroller, wherein when the sensed output voltage of the output capacitor reaches a predetermined setpoint, the microcontroller turns on the MOSFET switch, which prevents the power converter from further charging the output capacitor.
6. The energy harvesting circuit according to claim 1 wherein the power converter is a flyback converter.
7. The energy harvesting circuit according to claim 1 wherein the input and output capacitors are film capacitors.
8. The energy harvesting circuit according to claim 1 wherein the energy harvesting circuit and the vacuum interrupter are part of a recloser.
9. The energy harvesting circuit according to claim 8 wherein the recloser is a cut-out mounted recloser.
10. The energy harvesting circuit according to claim 8 wherein the recloser is a single phase self-powered magnetically actuated recloser.
11. The energy harvesting circuit according to claim 8 wherein the recloser is associated with a distribution transformer.
12. An energy harvesting circuit for harvesting energy from a power line to provide power to an actuator to close a vacuum interrupter associated with a recloser, the energy harvesting circuit comprising:
an input capacitor electrically coupled to the power line and storing power therefrom;
a flyback converter including a primary coil and a secondary coil;
a switching circuit electrically coupled in series with the primary coil and the combination of the primary coil and the switching circuit being electrically coupled in parallel with the input capacitor, the switching circuit being operable to electrically connect and disconnect the input capacitor to and from the primary coil, the switching circuit including an input voltage regulation feedback circuit for regulating an input voltage provided to the switching circuit from the input capacitor;
an output capacitor electrically coupled to the secondary coil and the actuator, the output capacitor being charged by the secondary coil when the switching circuit is closed to provide power to the actuator to close the vacuum interrupter;
wherein the input voltage regulation feedback circuit includes an integrated circuit having a feedback pin, a first MOSFET switch, a pulse width modulation (PWM) controller and a comparator, wherein when a feedback voltage provided to the feedback pin is below a reference voltage, a high signal is generated at an output of the comparator, which triggers the PWM controller to generate a PWM signal that turns on the first switch so that power is provided to the primary coil from the input capacitor, and when the feedback voltage at the feedback pin is above the reference voltage, the PWM signal is stopped; and
wherein the input voltage regulation feedback circuit further includes a first set of series-connected transient voltage suppression (TVS) diodes that are electrically coupled in parallel with the input capacitor and a second switch, the first set of series-connected TVS diodes controlling an input voltage regulation setpoint at the feedback pin to be equal to the series breakdown voltage of the first set of series-connected TVS diodes, wherein when the input voltage across the input capacitor is higher than the overall breakdown voltage of the first set of series-connected TVS diodes, the second switch will turn on which pulls down the feedback pin, which triggers the PWM controller.
13. The energy harvesting circuit according to claim 12 wherein the switching circuit further includes a second set of series-connected TVS diodes that have a lower breakdown voltage than the first set of series-connected TVS diodes and that is equal to a desired minimum value of the input voltage, and includes two optoisolator switches each having a phototransistor and an LED, wherein when the input capacitor is charged to a voltage higher than the sum of the breakdown voltages of the first set of series-connected TVS diodes, the phototransistor in one of the optoisolator switches conducts providing a path for current to flow in the LED in the other optoisolator switch, the phototransistor in the other optoisolator switch provides a latch for the LED in the one optoisolator switch, which drives the second MOSFET switch.
14. The energy harvesting circuit according to claim 12 wherein the switching circuit further includes an output voltage regulation feedback circuit for controlling the output voltage of the output capacitor, the output feedback circuit including an optoisolated transistor coupled to the feedback pin, the optoisolated transistor including a bipolar junction transistor and an LED, wherein when the output voltage on the output capacitor begins to exceed a predetermined setpoint, the bipolar junction transistor will begin to conduct, which turns off the power transfer from the primary coil to the secondary coil by completely discharging the input capacitor.
15. The energy harvesting circuit according to claim 12 further comprising a voltage clamp circuit for controlling the output voltage of the output capacitor, the voltage clamp circuit including a MOSFET switch and a microcontroller, wherein when the sensed output voltage of the output capacitor reaches a predetermined setpoint, the microcontroller turns on the MOSFET switch, which prevents the power converter from further charging the output capacitor.
16. The energy harvesting circuit according to claim 12 wherein the input and output capacitors are film capacitors.
17. An energy harvesting circuit for harvesting energy from a power line to provide power to an actuator to close a vacuum interrupter, the energy harvesting circuit comprising:
an input film capacitor electrically coupled to the power line and storing power therefrom;
a flyback converter including a primary coil and a secondary coil;
a switching circuit electrically coupled in series with the primary coil and the combination of the primary coil and the switching circuit being electrically coupled in parallel with the input capacitor, the switching circuit being operable to electrically connect and disconnect the input capacitor to and from the primary coil, the switching circuit including an input voltage regulation feedback circuit for regulating an input voltage provided to the switching circuit from the input capacitor;
an output film capacitor electrically coupled to the secondary coil and the actuator, the output capacitor being charged by the secondary coil when the switching circuit is closed to provide power to the actuator to close the vacuum interrupter; and
a voltage clamp circuit for controlling the output voltage of the output capacitor, the voltage clamp circuit including a MOSFET switch and a microcontroller, wherein when the sensed output voltage of the output capacitor reaches a predetermined setpoint, the microcontroller turns on the MOSFET switch, which prevents the power converter from further charging the output capacitor.