초록 ▼

A flywheel energy storage system for preventing power interruptions to a load from interruptions of primary power includes a flywheel supported for rotation about an axis on a bearing system, and a motor-generator having a rotor coupled with the flywheel, and having a stator with multiple armature w

A flywheel energy storage system for preventing power interruptions to a load from interruptions of primary power includes a flywheel supported for rotation about an axis on a bearing system, and a motor-generator having a rotor coupled with the flywheel, and having a stator with multiple armature windings and a field coil. The field coil generates flux that passes through the armature windings as the rotor rotates to produce torque for accelerating the flywheel during charging, and produces electrical power from the flywheel during discharge. The armature windings are energized by a DC buss that is supplied by a rectifier connected to primary power. The flywheel system provides instantaneous full power capability along with output control for extracting more energy from the flywheel. The field coil is oversized and is powered in standby operation to produce an armature back emf that is at least 75% of the DC buss voltage. The current to the field coil remains substantially constant during a period including immediately before an interruption and immediately after and interruption of primary power. The flywheel system uniquely utilizes an extremely large field coil, which is preferably 25-50% of the weight of the flywheel. The increased field coil size allows for both full standby energization without overheating and also reduces the armature reaction such that full power is available during a power interruption without requiring instantaneous increasing of the field coil current. In one embodiment, the field controller has a speed sensor for monitoring rotational speed of the flywheel and for varying electrical power to the field coil, without monitoring the primary power for interruptions. The field controller varies electrical current to the field coil approximately inverse linearly with the rotational speed of the flywheel during both standby and discharging operation to govern power to the field coil during standby operation such that the back emf of the armature remains substantially constant during an interruption of power.

대표청구항 ▼

What is claimed is: 1. A flywheel energy storage system for preventing power interruptions to a load from interruptions of primary power, comprising: a flywheel that is supported for rotation about an axis on a bearing system, and a motor-generator having a stator and a rotor coupled with said flyw

What is claimed is: 1. A flywheel energy storage system for preventing power interruptions to a load from interruptions of primary power, comprising: a flywheel that is supported for rotation about an axis on a bearing system, and a motor-generator having a stator and a rotor coupled with said flywheel, said motor-generator has multiple stationary armature windings and a field coil; said field coil generates flux that passes through said armature windings as said rotor rotates; a rectifier connected to said primary power for delivering rectified primary power to a DC buss; an inverter connected to said DC buss for converting power from said DC buss to output power to said load; a synchronous inverter for delivering synchronized power to excite said armature windings during recharging of said flywheel; a field controller for maintaining power to said field coil during standby operation such that the current to said field coil remains substantially constant during a period including immediately before an interruption of primary power and immediately after an interruption of primary power. 2. A flywheel energy storage system as described in claim 1 wherein: said field controller includes a speed sensor for monitoring rotational speed of said flywheel and varying electrical power to said field coil to maintain a substantially constant back emf in said armature windings during an interruption of said primary power. 3. A flywheel energy storage system as described in claim 2 wherein: said field controller varies electrical current to said field coil approximately inverse linearly with said rotational speed of said flywheel. 4. A flywheel energy storage system as described in claim 1 wherein: said field coil has a weight Wfc in pounds, and said flywheel has a weight Wfw in pounds, wherein Wfc/Wfw>0.25. 5. A flywheel energy storage system as described in claim 1 wherein: said armature windings are located in a magnetic air gap formed between two surfaces of said rotor that rotate together. 6. A flywheel energy storage system as described in claim 5 wherein: said flux crosses only a single magnetic airgap in said motor/generator. 7. A flywheel energy storage system as described in claim 1 wherein: said field coil has a weight Wfc in pounds, and said flywheel energy storage system has a 15 second output power capability P in kilowatts, wherein Wfc/P>0.60. 8. A flywheel energy storage system as described in claim 1 wherein: said field coil has an inductance Ifc, and said armature windings has an individual phase inductance Iap, wherein Ifc/Iap>25, 000. 9. A flywheel energy storage system for preventing power interruptions to a load from interruptions of primary power, comprising a flywheel that is supported for rotation about an axis on a bearing system, and a motor-generator having a rotor coupled with said flywheel, and a stator; said motor-generator has multiple stationary armature windings and a field coil; said field coil generates flux that passes through said armature windings as said rotor rotates; said armature windings are excited by a synchronous inverter connected to a DC buss that receives rectified primary power from a rectifier connected to said primary power; an inverter connected to said DC buss converts power from said DC buss to output power to said load; whereby, said field controller maintains power to said field coil when said primary power is not interrupted such that the back emf of said armature windings is equal to at least 75% of the voltage of said DC buss. 10. A flywheel energy storage system as described in claim 9 wherein: said field controller includes a speed sensor for monitoring rotational speed of said flywheel and varying electrical power to said field coil to maintain a substantially constant back emf in said armature windings during an interruption of primary power. 11. A flywheel energy storage system as described in claim 9 wherein: said field coil has a weight Wfc in pounds, and said flywheel energy storage system has a 15 second output power capability P in kilowatts, wherein Wfc/P>0.60. 12. A flywheel energy storage system as described in claim 9 wherein: said field coil has a weight Wfc in pounds, and said flywheel has a weight Wfw in pounds, wherein Wfc/Wfw>0.25. 13. A flywheel energy storage system as described in claim 9 wherein: said armature windings are located in a magnetic air gap formed between two surfaces of said rotor that rotate together. 14. A flywheel energy storage system as described in claim 9 wherein: said field coil has an inductance Ifc, and said armature windings has an individual phase inductance Iap, wherein Ifc/Iap>25, 000. 15. A flywheel energy storage system for preventing power interruptions to a load from interruptions of primary power, comprising a flywheel that is supported for rotation about an axis on a bearing system, and a motor-generator having a rotor coupled with said flywheel, and a stator; said motor-generator has multiple stationary armature windings and a field coil; said field coil generates flux that passes through said armature windings as said rotor rotates; said armature windings are excited by a synchronous inverter connected to a DC buss that receives rectified primary power from a rectifier connected to said primary power; an inverter connected to said DC buss converts power from said DC buss to output power to said load; whereby, said field coil has an inductance Ifc, and said armature windings has an individual phase inductance Iap, wherein Ifc/Iap>25,000. 16. A flywheel energy storage system as described in claim 15 wherein: said field coil has an inductance Ifc, and said armature windings has an individual phase inductance Iap, wherein Ifc/Iap>100, 000. 17. A flywheel energy storage system as described in claim 15 wherein: said field coil has a weight Wfc in pounds, and said flywheel has a weight Wfw in pounds, wherein Wfc/Wfw>0.25. 18. A flywheel energy storage system as described in claim 15 wherein: said armature windings are located in a magnetic air gap formed between two surfaces of said rotor that rotate together. 19. A flywheel energy storage system as described in claim 15 wherein: said field controller includes a speed sensor for monitoring rotational speed of said flywheel and varying electrical power to said field coil to maintain a substantially constant back emf in said armature windings during an interruption of primary power. 20. A flywheel energy storage system as described in claim 15 wherein: said field coil has a weight Wfc in pounds, and said flywheel energy storage system has a 15 second output power capability P in kilowatts, wherein Wfc/P>0.60.