Variable speed drive with a battery
Embodiments of the present disclosure relate to a heating, ventilating, air conditioning, and refrigeration (HVAC&R) system that includes a variable speed drive (VSD) configured to supply power to a motor configured to drive a compressor of the HVAC&R system, a rectifier of the VSD configured to receive alternating current (AC) power from an AC power source and convert the AC power to direct current (DC) power, a DC bus of the VSD electrically coupled to the rectifier, an inverter of the VSD electrically coupled to the DC bus, where the inverter is configured to convert the DC power to output AC power, the output AC power has a variable voltage and a variable frequency, and the output AC power is directed to the motor, and a battery electrically coupled to the DC bus, where the battery is configured to provide auxiliary DC power to the VSD.
1. A heating, ventilating, air conditioning, and refrigeration (HVAC&R) system, comprising:
a variable speed drive configured to supply power to a motor, wherein the motor is configured to drive a compressor of the HVAC&R system;
a rectifier of the variable speed drive configured to receive alternating current (AC) power from an AC power source and convert the AC power to direct current (DC) power;
a DC bus of the variable speed drive electrically coupled to the rectifier, wherein the DC bus is configured to modify the DC power received from the rectifier;
an inverter of the variable speed drive electrically coupled to the DC bus, wherein the inverter is configured to convert the DC power from the DC bus to output AC power, wherein the output AC power comprises a variable voltage and a variable frequency, wherein the output AC power is directed to the motor, wherein the rectifier and the inverter are active and enable current flow through the rectifier and the inverter in a first direction and in a second direction, and wherein the first direction is opposite the second direction; and
a battery electrically coupled to the DC bus of the variable speed drive, wherein the battery is configured to provide auxiliary DC power to the variable speed drive.
2. The system of claim 1 , wherein the rectifier comprises a first plurality of transistors, and wherein the inverter comprises a second plurality of transistors.
3. The system of claim 1 , wherein the motor is configured to provide DC power to the battery to charge the battery.
4. The system of claim 1 , comprising a charger coupled to the battery and the AC power source, wherein the charger is configured to receive and condition AC power from the AC power source and supply DC power to the battery.
5. The system of claim 4 , comprising a switch, wherein the switch is configured to open when a voltage of the AC power from the AC power source reaches a threshold.
6. The system of claim 5 , comprising a diode disposed between the battery and the DC bus, wherein the diode is configured to block current from flowing from the DC bus to the battery.
7. The system of claim 1 , wherein the DC bus is configured to amplify a voltage of the DC power, or reduce a voltage of the DC power, or both.
8. The system of claim 1 , wherein the AC power from the AC power source comprises three-phase AC power.
9. The system of claim 1 , wherein the battery is configured to supply between 500 kW and 25,000 kW of DC power to the variable speed drive.
10. A variable speed drive for a heating, ventilating, air conditioning, and refrigeration (HVAC&R) system, comprising:
a rectifier of the variable speed drive configured to receive alternating current (AC) power from an AC power source and convert the AC power to direct current (DC) power;
a DC bus of the variable speed drive electrically coupled to the rectifier, wherein the DC bus is configured to amplify or reduce a voltage of the DC power received from the rectifier;
an inverter of the variable speed drive electrically coupled to the DC bus, wherein the inverter is configured to convert the DC power from the DC bus to output AC power, wherein the output AC power comprises a variable voltage and a variable frequency, and wherein the output AC power is directed to the motor;
a battery electrically coupled to the DC bus of the variable speed drive, wherein the battery is configured to provide auxiliary DC power to the variable speed drive;
a switch configured to open when a voltage of the AC power from the AC power source reaches a threshold; and
a charger electrically coupled to the AC power source and the battery, wherein the charger is configured to receive AC power from the AC power source and provide DC power to the battery.
11. The system of claim 10 , comprising a diode disposed between the battery and the DC bus, wherein the diode is configured to block current from flowing from the DC bus to the battery.
12. The system of claim 10 , wherein the rectifier comprises a plurality of diodes configured to convert the AC power to DC power.
13. The system of claim 10 , wherein the AC power from the AC power source comprises three-phase AC power.
14. The system of claim 10 , wherein the battery is configured to supply between 500 kW and 25,000 kW of DC power to the variable speed drive.
15. A method, comprising:
monitoring a voltage of alternating current (AC) power directed from an AC power source to a variable speed drive;
using the AC power from the AC power source to operate a motor with the variable speed drive when the AC power is above a threshold; and
directing power to the variable speed drive from a battery to operate the motor with the variable speed drive when the AC power is at or below the threshold.
16. The method of claim 15 , comprising monitoring a speed of the motor receiving power from the variable speed drive, or monitoring a discharge pressure of a compressor driven by the motor, or both.
17. The method of claim 16 , comprising selectively supplying power from the AC power source and the battery based on the speed of the motor, or the discharge pressure of the compressor, or both.
18. The method of claim 15 , comprising receiving power in a charger from the AC power source.