Stand-alone wind turbine system, apparatus, and method suitable for operating the same

• US 20070246943A1
• Filed: 04/25/2006
• Published: 10/25/2007
• Est. Priority Date: 04/25/2006
• Status: Active Grant

• Current Assignee: University of New Brunswick
• Original Assignee: University of New Brunswick
• Inventors: Chang, Liuchen, Lian, Jiyong
• Granted Patent: US 7,476,987 B2
• Time in Patent Office: Days
• US Class Current: 290/44
• CPC Class Codes: F03D 9/11 storing electrical energy
• CPC Class Codes: F03D 9/25 the apparatus being an electrical generator F03D9/22 takes precedence
• CPC Class Codes: H02J 2300/10 The dispersed energy generation being of fossil origin, e.g. diesel generators
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/28 The renewable source being wind energy
• CPC Class Codes: H02J 2300/40 wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously
• CPC Class Codes: H02J 3/28 Arrangements for balancing of the load in a network by storage of energy
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/388 Islanding, i.e. disconnection of local power supply from the network
• CPC Class Codes: H02J 7/1415 with a generator driven by a prime mover other than the motor of a vehicle
• CPC Class Codes: H02J 7/1492 by means of controlling devices between the generator output and the battery
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects
• CPC Class Codes: Y02E 70/30 Systems combining energy storage with energy generation of non-fossil origin

Abstract

This invention provides a wind turbine-battery-dump load stand-alone renewable energy system and an optimal control of the same. The system may include both power conversion and control units. In one embodiment, the power conversion unit features a wind-turbine-driven three-phase induction generator, a diode rectifier, a battery charger, a boost dc/dc converter, a battery bank (48V), and a dc/ac inverter. A dump load is also used to dissipate excess power that is not required for either the battery charging or for the load. The integrated control unit may use the TMS320LF2407A DSP microcontroller from Texas Instruments, which allows operations of the wind power system and the battery storage system to be merged into a single package under a master controller. An embodiment of the control system features battery-charging control, battery voltage-boost control, dump load control, PWM inverter control, and system protection. It enables the use of renewable energy resources, while at the same time facilitating an efficient management of energy dispatch. This integrated control system offers remote villages the potential to fully supply their electrical power needs.

Claims

1. A renewable energy power conversion apparatus suitable for generating electrical power at an output to drive a load using power obtained from a renewable energy source, the electrical power at the output of the apparatus provided at a substantially pre-determined output voltage level despite variations in the availability of the renewable energy source, the apparatus comprising:

(a) a power generator having a generator output, said power generator adapted to convert energy from the renewable energy source into a generated power at a generated voltage level that varies subject to the availability of the renewable energy source, the power generator rated for a pre-determined nominal generator voltage level;

(b) a buck-boost power flow channel coupling the generator output of said power generator to the output of the apparatus, said buck-boost power flow channel adapted to provide a first portion of the output power at the output of the apparatus by regulating a first portion of the generated power to a regulated voltage level and by boosting the first portion of the generated power to a voltage level which is substantially compatible with the pre-determined output voltage level; and

(c) a bypass power flow channel coupling the generator output of said power generator to the output of the apparatus, said bypass power flow channel adapted to operate in parallel with said buck-boost power flow channel to provide a second portion of the output power by passing the second portion of the generated power directly to the output of the apparatus at a voltage level which is substantially equal to the generated voltage level;

wherein most of the generated power flows from the output of said power generator to the output of the apparatus via said bypass power flow channel when the generated voltage level rises substantially above the nominal generator voltage level.

2. The apparatus as recited in claim 1, wherein the renewable energy source is a wind energy source, and wherein said power generator is a wind turbine power generator.

3. The apparatus as recited in claim 1, wherein most of the generated power flows from the output of said power generator to the output of the apparatus via said buck-boost power flow channel when the generated voltage level falls substantially below the nominal generator voltage.

4. The apparatus as recited in claim 1, further comprising a power storage system for storing a third portion of the output power, wherein the third portion of the generated power is stored in said power storage system when the generated power substantially exceeds the power requirements of the load, and wherein said power storage system provides the third portion of the output power when the power requirements of the load substantially exceed the generated power.

5. The apparatus as recited in claim 4, wherein the power storage system is a battery-bank.

6. The apparatus as recited in claim 4, further comprising a dump-load for disposing of a fourth portion of the generated power when said battery-bank is at a full state-of-charge and the generated power substantially exceeds the power requirements of the load.

7. The apparatus as recited in claim 4, further comprising a boost chopper coupled to said power storage system to receive the fourth portion of generated power, said boost chopper further coupled to the output of the apparatus to condition the fourth portion of generated power to a voltage level that is compatible with the output voltage.

8. The apparatus as recited in claim 4, wherein the power storage system is an electrolyzer coupled to a genset.

9. The apparatus as recited in claim 1, further comprising a boost power source, wherein said boost power source provides a third portion of the output power when the power requirements of the load substantially exceed the generated power.

10. The apparatus as recited in claim 9, wherein the boost power source is selected from the group comprising:

battery-bank, genset, photovoltaic array, and grid power.

11. The apparatus as recited in claim 1, further comprising a rectifier coupled to said power generator for providing the generated power as a direct current.

12. The apparatus as recited in claim 1, wherein the renewable energy source is a solar energy source, and wherein said power generator is a photovoltaic generator.

13. The apparatus as recited in claim 1, further comprising an inverter coupled to the output for providing the output voltage as an alternating current.

14. The apparatus as recited in claim 1, wherein said bypass channel comprises a bypass diode.

15. The apparatus as recited in claim 1, wherein at least one component of the apparatus is switched off when most of the generated power flows from the output of said power generator to the output of the apparatus via said bypass power flow channel thereby increasing the efficiency of the apparatus.

16. The apparatus as recited in claim 15, further comprising a boost chopper.

17. The apparatus as recited in claim 16, wherein the boost chopper one of the at least one component of the apparatus which is switched off.

18. A method suitable for controlling a power conversion apparatus, the method comprising the steps of:

(a) selectively operating the power conversion apparatus in a selected mode, the selected mode selected from a group of modes comprising;

(i) a buck-boost mode whereat all of the output power flows through the buck-boost channel; and

(ii) a bypass mode whereat all of the output power flows through the bypass channel; and

(b) switching off at least one component of the power conversion apparatus that is not required to operate the power conversion apparatus in the selected mode.

19. The method as recited in claim 18, further comprising the step of switching on at least one component of the power conversion apparatus that is required to operate the power conversion apparatus in the selected mode.

20. The method as recited in claim 18, wherein the power conversion apparatus further comprises a battery, wherein the group of modes further comprises a battery only mode whereat all of the output power is provided by the battery.

21. The method as recited in claim 20, further comprising the step of measuring a battery current.

22. The method as recited in claim 21, further comprising the step of determining that the battery is in a discharging mode upon determining the condition that the battery current is substantially not greater than zero.

23. The method as recited in claim 22, further comprising the step of determining a state-of-charge (SOC) of the battery.

24. The method as recited in claim 23, wherein the power conversion apparatus further comprises a boost chopper.

25. The method as recited in claim 24, wherein the method further comprises the step of switching off the boost chopper upon determining the condition that the battery is in a discharging mode and the SOC is substantially less than or equal to a minimum charge SOC set point.

26. The method as recited in claim 22 wherein the power conversion unit further comprises a battery charger.

27. The method as recited in claim 26, further comprising the step of determining that the battery is in a charging mode upon determining the condition that the battery current is substantially greater than zero.

28. The method as recited in claim 27, further comprising the step of switching off the battery charger upon determination of the condition that the battery is in the charging mode and the SOC is substantially greater than or equal to a maximum charge SOC set point.

29. The method as recited in claim 27, wherein the method further comprises the step of operating the battery charger for bulk charge upon the condition that the battery is in charging mode and that the SOC is substantially less than a maximum charge SOC set point and that the SOC is substantially greater or equal to a charge mode SOC set point, the charge mode SOC set point having a value which is less than the maximum charge SOC set point.

30. The method as recited in claim 27, wherein the method further comprises the step of operating the battery charger for float charge upon the condition that the battery is in charging mode and that the SOC is substantially less than a maximum charge SOC set point and that the SOC is substantially less than a charge mode SOC set point, the charge mode SOC set point having a value which is less than the maximum charge SOC set point.

31. The method as recited in claim 23, wherein the SOC is determined using ampere-hour (Ah) balancing.

32. The method as recited in claim 23, wherein the SOC is determined using specific gravity.

33. The method as recited in claim 23, wherein the SOC is determined using terminal voltage measurement.

34. A computer program product for controlling a power conversion apparatus, comprising:

a computer usable medium having computer readable program code embodied in said medium for avoiding traffic events, said computer program product having;

selectively operating the power conversion apparatus in a selected mode, the selected mode selected from a group of modes comprising;

a buck-boost mode whereat all of the output power flows through the buck-boost channel; and

a bypass mode whereat all of the output power flows through the bypass channel; and

switching off at least one component of the power conversion apparatus that is not required to operate the power conversion apparatus in the selected mode.

35. An integrated power conversion apparatus suitable for operating a wind turbine, the apparatus comprising:

(a) the power conversion apparatus;

(b) an interfacing board coupled to the power conversion apparatus;

(c) a DSP-based microcontroller coupled to the power conversion apparatus via the interfacing board; and

(d) a computer program product coupled to the DSP-based microcontroller, wherein said DSP-based microcontroller executes said computer program product to control said power conversion apparatus via said interfacing board.

36. A method for converting energy from a renewable energy source, the method comprising the steps of:

(a) generating an irregular AC voltage;

(b) rectifying the AC voltage to produce an irregular DC voltage;

(c) regulating the irregular DC voltage to produce a constant DC voltage;

(d) stepping up the constant DC voltage to produce a stepped up DC voltage; and

(e) converting the stepped up DC voltage into a sinusoidal AC voltage.

37. The method as recited in claim 36, further comprising the step of bypassing the steps of regulating and stepping up under the condition that the rectified irregular DC voltage is compatible with the step of converting, and wherein the irregular DC voltage is used instead of the stepped up DC voltage in the converting step.