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Title:
MODULAR GENERATOR SYSTEM FOR WIND TURBINES
Document Type and Number:
WIPO Patent Application WO/2010/083590
Kind Code:
A1
Abstract:
A modular generator system for wind turbines having a plurality of generators, and that may be configured to mechanically and/or electronically adjust the load according to wind conditions, to provide some intentional slip between the wind turbine and the modular generator to accommodate fluctuating wind conditions, and to use one or more of the modular generator components as motors to provide supplemental power to the wind turbine such that the apparent wind is closer to ideal conditions thereby increasing the efficiency of the wind turbine.

Inventors:
HARRISON HOWARD (CA)
Application Number:
CA2010/000068
Publication Date:
July 29, 2010
Filing Date:
January 22, 2010
Export Citation:
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Assignee:
HARRISON HOWARD (CA)
International Classes:
H02K7/18; F03D9/00; H02J15/00; H02K7/10; H02K16/00; H02P9/04
Domestic Patent References:
WO2008078342A12008-07-03
Foreign References:
US20050280264A12005-12-22
DE19652673A11998-06-25
US4464579A1984-08-07
GB2447630A2008-09-24
US20020070558A12002-06-13
Attorney, Agent or Firm:
RIDOUT & MAYBEE LLP (10th FloorToronto, Ontario M5V 3M2, CA)
Download PDF:
Claims:
Claims:

1. A generator system for a wind turbine, comprising:

a) a primary generator operably connected to a turbine shaft of the wind turbine, such that rotation of the turbine shaft is transformed into electrical energy by the primary generator;

b) at least one secondary generator;

wherein the generator system can be switched between two configurations, a first configuration wherein the secondary generator is operably connected to said turbine shaft so that rotation of the turbine shaft is transformed into electrical energy by the secondary generator, and a second configuration wherein the secondary generator is not operably connected to the turbine shaft and rotation of the turbine shaft is not transformed into electrical energy by the secondary generator.

2. The generator system of claim 1 further comprising a braking system offering a user-selectable resistance and utilized for switching between the two configurations, such that, when the brakes are activated, the generator system is in the first configuration, and when the brakes are not activated, the generator system is in the second configuration.

3. A generator system for a wind turbine having a primary shaft and a coaxial secondary shaft, comprising:

a) a primary generator operably connected to the primary shaft, such that rotation of the primary shaft is transformed into electrical energy by the primary generator; b) at least one secondary generator operably connected to the secondary shaft, such that rotation of the secondary shaft is transformed into electrical energy by the at least one secondary generator.

4. A generator system for a wind turbine having a primary shaft and a coaxial secondary shaft, comprising:

a) a primary generator operably connected to the primary shaft, such that rotation of the primary shaft is transformed into electrical energy by the primary generator;

b) at least one secondary generator;

wherein the system can be switched between two configurations, a first configuration wherein the secondary generator is operably connected to said secondary shaft such that rotation of the secondary shaft is transformed into electrical energy by the at least one secondary generator, and a second configuration wherein the secondary generator is not operably connected to the secondary shaft and rotation of the turbine shaft is not transformed into electrical energy by the secondary generator.

5. The generator system of claim 4 further comprising a braking system offering a user-selectable resistance and utilized for switching between the two configurations, such that, when the brakes are activated, the generator system is in the first configuration, and when the brakes are not activated, the generator system is in the second configuration.

6. The generator system of any one of claims 1-5 wherein the primary generator and the secondary generator have different generating capacities.

7. The generator system of any one of claims 1-6 wherein the primary generator is geared and configured to operate at peak efficiency under lighter wind conditions than the secondary generator.

8. The generator system of any one of claims 1 -7 wherein the secondary generator can be utilized as a motor to provide rotational energy to the turbine shaft.

9. The generator system of any one of claims 1-8 further comprising a controller which: a) measures an amount of energy generated from the primary generator; b) directs the electricity generated from the secondary generator based on (a); wherein the electricity generated from the secondary generator is directed to a power line also used to transmit the energy generated from the primary generator when the amount measured in (a) is below a certain threshold, and the electricity generated from the second generator is directed to another power line or to a battery when the amount measured in (a) is above said threshold.

10. The generator system of any one of claims 1 -9 further comprising a controller which: a) measures an amount of energy generated from the primary generator; b) switches the generator system from the first configuration to the second configuration where the amount measured in (a) is above a certain threshold.

11. The generator system of claim 2 wherein said braking system with user selectable resistance allows for intentional slip.

12. The generator system for a wind turbine having a primary shaft and a coaxial secondary shaft of claim 3, wherein the relative rotational positions of said primary shaft and said secondary shaft may be adjusted during operation.

13. The generator system for a wind turbine having a primary shaft and a coaxial secondary shaft of claim 3, wherein the load on said primary shaft is approximately equal to the load on said secondary shaft when the relative rotational positions of said primary shaft and said secondary shaft are being adjusted.

14 The generator system of any one of claims 1-7 wherein the secondary generator can be utilized as a motor to provide rotational energy to the turbine shaft during start-up.

15. The generator system of any one of claims 1 -7 wherein the secondary generator can be utilized as a motor to provide rotational energy to the turbine shaft during normal operation.

16. The generator system of any one of claims 1-8 further comprising a controller which: a) measures an amount of energy generated from the primary generator; b) directs the operation of a secondary generator based on (a); wherein the electricity generated from the secondary generator is directed to a n energy storage device when the amount measured in (a) is above a certain threshold, and the energy stored in said energy storage device is directed to drive said secondary generator as a motor when the amount measured in (a) is below a certain threshold.

17. The generator system of claim 16 wherein said energy storage device is alternatively charged with supplementary generator, wherein said supplementary generator is not a wind generator.

18. A generator system for a wind turbine having a primary shaft, a secondary coaxial shaft, a primary rotating generator component, a secondary rotating generator component, and a stationary generating component, wherein said said primary shaft is operably connected to said primary rotating generator component and said secondary shaft is operably connected to said secondary rotating component, and wherein said primary and secondary rotating components induce electrical currents in said stationary generating component.

19. The generator system as claimed in claim 18 wherein the relative positions of said primary shaft and said secondary shaft may be adjusted.

20. The generator system as claimed in claim 18 wherein said primary rotating component and said secondary rotating component are counter rotating.

21. The generator system as claimed in claim 18 wherein said stationary generating component contains a plurality of windings, wherein said windings are of different capacities.

22. The generator system as claimed in claim 18 wherein said stationary generating component contains a plurality of windings, wherein said windings are selectively activated and de-activated.

Description:
Modular Generator System for Wind Turbines

Cross Reference to Related Application This application claims priority from US 61/146,343, filed January 22, 2009, which is included herein by reference.

Field of the Invention

The invention pertains to the field of generator systems for wind turbines.

Background of the Invention

Wind turbines allow the generation of electrical energy from wind. Essentially, a wind turbine typically comprises a set of blades on a shaft. Wind passing across the blades creates rotational displacement of the shaft. The shaft is connected to a generator, whereby the rotational displacement is translated into electrical energy.

Brief description of the Figures

Figure 1 is a side view of the modular generator system according to one aspect of the present invention.

Figure 2 is a schematic of an alternative configuration of the modular generator system according to a further aspect of the present invention.

Figure 3 provides an alternate side view of an alternate embodiment of the invention, a modular generator system for a wind turbine, adapted for use with wind turbines that have two co-axial shafts. Figure 4 is a front view of a modular generator system for wind turbines configured for use as a composite generator system, according to another embodiment of the invention.

Figure 5 is a front view of an asymmetrical modular generator system for wind turbines according to another embodiment of the invention.

Figure 6 shows a simple control algorithm according to another embodiment of the invention.

Figure 7 shows a counter rotating modular generator according to another aspect of the present invention.

Detailed Description

Disclosed is a modular generator system for wind turbines that may be configured to mechanically and/or electronically adjust the load according to wind conditions, to provide some intentional slip between the wind turbine and the modular generator to accommodate fluctuating wind conditions, and to use one or more of the modular generator components as motors to provide supplemental power to the wind turbine such that the apparent wind is closer to ideal conditions thereby increasing the efficiency of the wind turbine.

Figure 1 provides a side view of modular generator system for wind turbines 1. Main turbine shaft 2 may be in mechanical communication with primary generator 4, such that primary generator 4 will generate electrical power when main turbine shaft 2 is rotated at sufficient rpm.

Main turbine shaft 2 may also be in mechanical communication with brake housings 8a and 8b, which may be further configured with brake pads 10a and iθb. Brake pads iOa and 10b may be de-activated to release flywheel 6, thereby allowing flywheel 6 to remain stationary while main turbine shaft 2 is rotating. Alternatively brake pads 10a and 10b may be activated such that flywheel 6 is in mechanical communication with main turbine shaft 2, causing flywheel 6 to rotate with main turbine shaft 2. Flywheel 6 may be further configured with gear teeth on the perimeter to interoperate with gear shafts 14a and 14b, such that a rotation of flywheel 6 will cause secondary generators 12a and 12b to generate electrical power. It follows that primary generator 4 and secondary generators 12a and 12b will all generate electrical power when brake pads iOa and 10b are activated and when main turbine shaft 2 is rotated at sufficient rpm.

Brake pads 10a and 10b may be configured with a sufficient coefficient of static friction, relative to the mating surfaces of flywheel 6, to retain flywheel 6 and main turbine shaft 2 in mechanical communication under relatively constant wind and electrical load conditions. Further, the coefficient of static friction may be adjusted to accommodate different wind speeds, for example by varying the pressure between brake pads 10a and 10b and the mating surfaces of flywheel 6, which in turn will facilitate the transfer of different levels of torque to flywheel 6. However the coefficient of static friction may also be configured to allow some intentional slip between flywheel 6 and main turbine shaft 2 under variable electrical load and wind speed conditions, thereby reducing wear and tear on gear shafts 14a and 14b or any other means of power transmission that may be configured between flywheel 6 and secondary generators 12a and 12b.

In some applications brake pads 10a and 10b may be normally activated such that primary generator 4 and secondary generators 12a and 12b are normally in mechanical communication with main turbine shaft 2. In these applications the generators may be connected or disconnected to the electrical grid through electronic switching. It should be noted that the controlled and intentional slip characteristics of brake pads 10a and iOb may be retained in this configuration, preventing the excess wear and tear of transmission components under adverse and variable wind or load conditions as previously described. The electronic switching of primary generator 4 and secondary generators 12a and 12b allows for greater flexibility and greater efficiency under a wide range of wind conditions. As an example, secondary generators 12a and 12b may be configured to run at a higher rpm than main turbine shaft 2, hence generating electrical power more efficiently under low wind conditions than primary generator 4. In this configuration one or both of secondary generators 12a and 12b may be switched on under low wind conditions, primary generator 4 may switched on in favour of secondary generators 12a and 12b under mid-range wind conditions, and all generators may be switched on under high speed wind conditions. Several other control algorithms are possible to optimize the overall efficiency of modular generator system for wind turbines 1.

One or both of secondary generators 12a and 12b may be configured to be electronically connected to localized loads to dissipate excess power when wind speeds are high, thereby increasing the upper range of operation and delaying the turning of the wind turbine off the wind and the application of a main shaft brake (not shown). The localized loads may be power "dumps" such as heaters and boilers, or energy storage devices such as batteries or elevated water reservoirs. In the latter case the stored energy may be converted to electrical power, if necessary, and transmitted at a later point in time.

Further, one or both of secondary generators 12a and 12b may be configured to operate as motors when power is applied to the (normal) output. This would allow one or both of secondary generators 12a and 12b to selectively apply supplementary torque to main turbine shaft 2, causing the turbine blades affixed to main turbine shaft 2 to rotate faster than they normally would under certain wind conditions. This may be used to achieve and/or maintain more favourable apparent wind conditions for the turbine blades, thereby increasing the overall efficiency of the wind turbine. Alternatively the supplementary torque may be used to keep turbine shaft 2 rotating at a constant speed under fluctuating wind conditions, increasing the efficiency of primary generator 4 and improving the stability of the output power.

As an example, power may be applied to secondary generator 12a when wind speeds are below the specified cut-in speed for the turbine, causing the turbine blades to start rotating. This will change the apparent wind to a more favourable angle relative to the now rotating blades, thereby causing the blades to continue rotating with the available wind, at below cut-in wind speeds. The power applied to secondary generator 12a may be reduced and possibly removed as the rotating blades approach steady state. This approach will add to the overall efficiency of the wind turbine provided that the energy required to start and/or maintain the rotation of the blades does not exceed the energy produced by the rotating blades for a given period of time. The energy required to start and/or maintain the rotation of the blades may be supplied by a local battery array or some other means of energy storage. It should be noted that this approach may reduce the overall cost of a wind turbine so configured, as much of the cost of existing turbines is allocated to specialized blades that are configured to reduce cut-in speeds.

Figure 2 presents a schematic of an alternative configuration which may be used to reduce the size of the transmission line 60 used to connect primary generator 4 to power grid 62, thereby reducing the cost of connecting the wind turbine to the grid. In a traditional configuration transmission lines 60 may be sized to accommodate the maximum power generated by a wind turbine, for example 1.5 Megawatts. However wind turbines rarely generate power at the maximum rate and most usually generate power at substantially less than the maximum rate. In many cases the average power generated by a wind turbine may be as low as 30% to 40% of the maximum rate, as evidenced by "normal" capacity factors in this range. Transmission line 60 may be sized to accommodate a portion, for example 40%, of the total rated power of primary generator 4 plus secondary generators 12a and 12b. In higher than average wind conditions the power generated by primary generator 4, which might represent 40% of the total rated power of primary generator 4 plus secondary generators 12a and 12b, may be safely delivered to power grid 62 by transmission line 60. In these conditions controller 64 may be configured to use the excess power generated by secondary generators 12a and 12b to charge battery 66. Battery 66 may be any energy storage device such as a bank of lead acid batteries or an elevated water reservoir with the associated pumps and turbine generators. In regions with favourable geothermal conditions battery 66 may be based on or supplemented by geothermal energy. Further, in such cases the efficiency of the stored geothermal energy may be increased through the use of heat pumps.

In average wind conditions secondary generators 12a and 12b may be disconnected from main shaft 2, as previously described, and the power generated by primary generator 4 may be safely delivered to power grid 62 by transmission line 60. Alternatively controller 66 may be used to electronically disconnect secondary generators 12a and 12b from the load, as previously described, and the power generated by primary generator 4 may be safely delivered to power grid 62 by transmission line 60.

In lower than average wind conditions secondary generators 12a and 12b may be used as motors to deliver supplementary torque to main shaft 2, as previously described. Under these conditions controller 66 will obtain the power required to drive secondary generators 12a and 12b, when used as motors, from battery 66. If the wind speed is so low that the rated capacity of transmission line 60 may not be efficiently generated by primary generator 4, as supplemented by supplementary torque from secondary generators 12a and 12b, then controller 64 may deliver incremental power from battery 66 to transmission line 66 through incremental power line 70. In certain situations where the energy stored by battery 66 falls below a threshold level, controller 64 may engage supplementary generator 68 to charge battery 66. Supplementary generator 68 may use gasoline, natural gas, or some other source of energy to generate the required electricity. In persistent low or zero wind speed conditions the power generated by supplementary generator 68 may be more directly and more efficiently delivered to transmission line 60 through supplementary power line 70

It follows that the primary function of controller 64 is to maintain the power transmitted through transmission line 60 at a level that is as close as possible to the rated capacity of transmission line 60, which may indeed be similar to the capacity factor of primary generator 4 plus secondary generators 12a and 12b, at all times. Excess power generated by primary generator 4 plus secondary generators 12a and 12b may be delivered to and stored by battery 66. Alternatively, a shortage of power generated by primary generator 4 plus secondary generators 12a and 12b may be supplemented by battery 66 and / or supplementary generator 68. The combined system forms a type of hybrid generator that delivers a constant and predictable supply of power to grid 62 through transmission line 60.

Figure 3 provides an alternate side view of modular generator system for wind turbines 1 , adapted for use with wind turbines that have two co-axial shafts; main turbine shaft 2 and secondary turbine shaft 20. Secondary turbine shaft 20 may be in mechanical communication with flywheel 6, such that secondary turbine shaft 20 and main turbine shaft 2 may be in simultaneous mechanical communication with flywheel 6 when brake pads 10a and 10b are engaged with flywheel 6. It follows that secondary turbine shaft 20 may be rotated relative to main turbine shaft 2 when brake pads iOa and iOb are partially or fully released, allowing for an adjustment of the angular displacement between turbine blades that may be affixed to secondary turbine shaft 20 and main turbine shaft 2. Several other mechanisms for changing the angular displacement between turbine blades that may be affixed to secondary turbine shaft 20 and main turbine shaft 2 are possible. Regardless of the mechanism, it is important to note that an approximately equal distribution of he generator load between secondary turbine shaft 20 and main turbine shaft 2 reduces the torque differential between secondary turbine shaft 20 and main turbine shaft 2, and hence makes it easier to change the angular displacement between secondary turbine shaft 20 and main turbine shaft 2. In this case angular displacement may be defined as the number of angular degrees by which the blades affixed to main turbine shaft 2 lead the blades affixed to secondary turbine shaft 20, in the direction of rotation.

Figure 4 provides a front view of a modular generator system for wind turbines configured for use as composite generator system 30. In this configuration main turbine shaft 2 may be in mechanical communication with generator hub 32, being further configured with a plurality of coils 34 that rotate around the perimeter of generator hub 32. In this example main shaft 2 and generator hub 32 may rotate in a clockwise direction.

Composite generator system 30 may also be configured such that main turbine shaft 2 is in mechanical communication with extended flywheel 36, which may be further configured with internal gear ring 38, which interoperates with activator shafts 40a, 40b, 40c, and 4Od to cause generator activators 42a, 42b, 42c and 42d to rotate in a clockwise direction when turbine shaft 2 rotates in a clockwise direction, albeit at a faster rate of rotational speed. Generator activators 42a, 42b, 42c and 42d may be further configured with a plurality of permanent magnets 44 that rotate around their inside perimeters. Other configurations are possible, for example coils 34 may be permanent magnets and permanent magnets 44 may be coils, with a similar generator effect. Based on this configuration the clockwise rotation of main turbine shaft 2 would cause the clockwise rotation of coils 34 and further cause the faster clockwise rotation of permanent magnets 44. This will cause permanent magnets 44 to pass by coils 34 (i) in an opposing direction and (ϋ) at an increased rate of speed. It follows that a composite generator system 30 so configured with relatively few components would simulate the performance of a traditional generator connected to main turbine shaft 2 through a complex transmission designed to increase the rotational speed of the traditional generator relative to the rotational speed of main turbine shaft 2.

Composite generator system 30 may also be configured with a secondary shaft 20 connected to extended flywheel 36, with reference to Figure 3 in which secondary shaft 20 was connected to flywheel 6.

Figure 5 provides a front view of asymmetrical modular generator system for wind turbines 50. In this configuration primary generator 4, small secondary generator 52, medium secondary generator 54 and large secondary generator 56 may be of different or asymmetrical capacities to allow for greater flexibility of loading and supplementary power applications.

In one configuration, with a total generating capacity of 12 power units, primary generator 4, small secondary generator 52, medium secondary generator 54 and large secondary generator 56 may have generating capacities of 6, 1 , 2, and 3 units, respectively. Further, small secondary generator 52, medium secondary generator 54 and large secondary generator 56 may be geared and configured to operate at higher efficiency under low speed wind conditions than primary generator 4. It follows that a simple control algorithm may be developed to deliver 1 to 12 units of power, in 1 unit increments, as summarized in Figure 6. The indicated generator or combination of modular generators may be activated to provide the total capacity in the left column of the table in Figure 6. It should be noted that this range of power and load options may be achieved more simply with four asymmetrical modular generators so configured than with a greater number of similar capacity or symmetrical modular generators. Further, it should be noted that all of the aforementioned features of the modular generator system for wind turbines may be implemented with the asymmetrical modular generator system for wind turbines 50. These include, but are not limited to, the use of intentional slip brake pads to absorb the impact of fluctuating wind conditions, the use of universal generators / motors to apply power to main turbine shaft 2, thereby changing the apparent wind and increasing the overall efficiency of the wind turbine, and the use of multiple turbine shafts.

Figure 7 illustrates counter rotating modular generator 80. In this configuration main turbine shaft 2 may be in mechanical communication with main rotating generator component 82 such that main rotating generator component 82 rotates in a counter clockwise direction, and secondary turbine shaft 20 may be in mechanical communication with secondary rotating generator component 84 rotates in a clockwise direction, as indicated. The use of two independent turbine shafts connected to two independent rotating generator components allows modular generator 80 to absorb wind gust fluctuations with a reduced amount of mechanical wear and tear.

Main rotating generator component 82 may be configured with a plurality of main permanent magnets 92, and secondary rotating generator component 84 may be configured with a plurality of secondary permanent magnets 94. Stationary generator ring 86 may be configured with a plurality of generator coils 96. Main permanent magnets 92 will excite a current in generator coils 96 as they pass generator coils 96 in the counter clockwise direction, and secondary permanent magnets 94 will excite a further current in generator coils 96 as they pass generator coils 96 in the clockwise direction. The rate of change of the fluctuating magnetic fields will increase due to the counter rotating primary and secondary generator components 80 and 90, thereby increasing the efficiency of counter rotating modular generator at slower turbine speeds. In some cases the efficiency may be further increased by configuring main rotating generator component 82 and / or secondary rotating generator component 84 with gears to increase the differential in rotational speeds.

Of note is the fact that stationary generator ring 86 remains stationary, simplifying the wiring required to deliver the power generated by generator coils 96 to an alternate location. Further, one or more of generator coils 96 may be switched off to accommodate varying wind conditions, as previously described. Further, generator coils 96 may be of different asymmetrical sizes to facilitate the matching of the load to varying wind conditions with fewer generator coils 96, as previously described. Generator coils 96 may alternatively be connected to a grid or a battery to allow for a smaller than maximum capacity grid connection, as previously illustrated in Figure 2.

In an alternate embodiment main rotating generator component 82 and secondary rotating generator component 84 may be configured to rotate in the same direction. In these cases stationary generator component 86 may remain stationary or may alternatively be configured to rotate in a direction opposite to that of main rotating generator component 82 and secondary rotating generator component 84.

The modular generator system for wind turbines of the present invention allows for many applications. Although reference is made to the embodiments listed above, it should be understood that these are only by way of example and to identify the preferred use of the invention known to the inventors at this time. It is believed that the modular generator system for wind turbines has many additional uses that will become obvious once one is familiar with the fundamental principles of the invention. These additional uses include, but are not limited to, (i) the use of a symmetrical or asymmetrical modular generator system for wind turbines to increase the overall efficiency of a traditional three blade upstream wind turbine and (ii) the use of a symmetrical or asymmetrical modular generator system for wind turbines to increase the overall efficiency of wind turbines configured with dual shafts and rotors.