WO2012032547A2

WO2012032547A2 - Mechanism for blade pitch control for wind turbine

Info

Publication number: WO2012032547A2
Application number: PCT/IN2011/000617
Authority: WO
Inventors: Raghunathan V.Rajagopal
Original assignee: V Rajagopal Raghunathan
Priority date: 2010-09-10
Filing date: 2011-09-09
Publication date: 2012-03-15
Also published as: WO2012032547A3

Abstract

According to the present invention for controlling the turbine, there is provided as system comprises electromechanical means of coupler arrangement driven by motor shaft with pretension spring installed between arms of the coupler arrangement. During start mode, the spacer engages between arms of the coupler arrangement and until sustainable speed, the spacer is driven outwards from the arrangement (running mode). Once rotational speed exceeds cut-off, torque is not transmitted from airfoil blades to couplers; the pretension spring elongates results angular displacement of coupler1(6) which displaces push rod linearly and airfoil blades are brought to feathered condition which stops turbine by change in angle of attack. As additional embodiment to this invention, the position of air foil blade can be controlled by triggering effect of motor in which the pushrod gets activated by rotation of spider airfoil blade while motor becomes generator or dynamic brake (or) while it loses its load.

Description

Title of the Invention

MECHANISM FOR BLADE PITCH CONTROL FOR WIND TURBINE FIELD OF THE INVENTION

This invention relates to wind turbines with unique feature of pitch control. When the wind turbine driven by wind rotates more than operating speed it needs to be stopped for safety of the system. The existing wind turbine utilizes separate actuator with hydraulic controls for starting and stopping the turbine which is not reliable. The present invention relates to the wind turbine which does not require any separate hydraulic means for the above said purpose and instead it serves the purpose by exploiting the energy from the wind through a mechanical coupling or motor arrangement (additional embodiment) which is highly reliable than existing systems.

BACKGROUND AND PRIOR ART OF THE INVENTION

In recent years, it has become apparent that conventional methods of generating electricity will soon be insufficient to meet the world's ever-growing need for electric power. Serious concerns about the environmental and safety hazards of fossil fuel and nuclear energy are driving the development for clean alternative sources of energy. Such clean alternatives include hydroelectric, biomass, solar, and wind power. Since high wind areas are limited, there is a need to improve the efficiency of wind turbines to enable electric power generation in low wind speed conditions.

A search of the internet, literature and patent documents reveal that several technological advances have been made to improve the performance of both large and small wind turbines over the past two decades. Previously, problems included inefficient operation at low wind speeds and unsafe operation at high wind speeds. It is known that rotor blade aerodynamic efficiency and cut-in wind speed are related to the blade angle of incidence and the optimal angle of blade setting varies according to wind speed. Therefore, in order to maximize energy production for a wind turbine exposed to variable wind speeds, it is necessary to adjust the pitch of the blades as the wind speed changes, so that the blade always operates at an optimal angle of incidence with respect to the relative wind speed. Thus, the resulting lift to drag ratio maximizes energy production at low wind speeds, which occurs with the highest probability in most areas. At high wind speeds, it becomes necessary to control the load on the blades to prevent damage to the structure itself. This can be achieved by adjusting the pitch of the blades such that the load on the blades is minimized while still extracting rated power.

When the rotor is stationary, the turbine is essentially in a stalled state and all sections of the blade from root to tip are facing the wind at a high angle of incidence. The drag forces at tip sections oppose any torque generated at the root sections. Consequently, there is not enough torque to overcome the generator bearing friction and its magnetic cogging-torque and thus small turbines fail to self-start in low wind speed conditions. The existing wind turbines in the market utilizes separate actuator with either hydraulic or mechanical controls for stopping the turbine which is not efficient and also very unreliable for providing safety to the system.

A few patents are typical of the known prior art attempting to improve on earlier efforts to harness wind energy. For example, U.S Pat. No. 4408958 to Schacle discloses a wind turbine blade with substantially curved (highly cambered) airfoil near leading and trailing edges at root sections of the blade. Although this invention can help generate some torque at low wind speeds, the outboard sections do facilitate an easy-start and the rotor is likely to remain at a stalled condition at very low wind speeds.

While U.S Pat. No. 4427897 to Migliori discloses a fixed pitch wind turbine system, which utilizes aerodynamic stall to minimize air load on the blades in high wind conditions. But, this approach does not help self-start in low wind speed conditions. U.S Pat. No. 6609889 to Vilsboll discloses a method and device for adjusting the blade pitch and stopping the rotation of the blades at high wind speed conditions using a motor driven mechanism. U.S Pat. No. 5506453 issued to McCombs, also describes a passively pitchable device which involves an extremely complex system. The S-like cam groove aligned nearly in the axial direction can only swivel the blade in one direction like any other torsion spring controlled mechanical devices. To control the blade loading in high winds, McCombs suggests a separate device as described therein where a high pressure hydraulic servo-control is used. This invention has not yet been reduced to practice and it may be impractical or uneconomical for implementation in low cost small wind turbines. But none of the prior art documents disclose a wind turbine comprising the system for the control and regulation of the rotational speed of the blades and the rotors irrespective of the wind energy.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a system of the wind power generation system with the aid of the electromechanical and hydraulic control mechanism for the pitch control of the system. The wind turbine comprises of coupling arrangement for starting and stopping the rotational speed of the turbine by bringing the airfoil blades from ln-wind position to feathered position and vice versa. A spacer arrangement engages and disengages with the couplers based on the centrifugal force corresponding to the rotational speed of the wind turbine. The position of spacer controls the operational mode of the turbine by means of suitable sensor to sense its position. The push rod connected at trail end^' of the blades control the amount of wind incident on the airfoil blades by bringing the air foil blades to feathered or ln-wind position thereby stopping or starting the turbine as required. The centrifugal mass stops the turbine while the transmission of torque exists and rotational speed goes beyond the operating speed. As an additional embodiment to the above said invention, the position of air foil blade can be controlled by triggering effect of motor in which the pushrod gets activated by the rotation of spider airfoil blade while the motor becomes generator or dynamic brake (or) while it loses its load.

OBJECT OF THE INVENTION

It is an object of the invention to provide a simple and economical wind turbine system which effectively achieves easy-starting and easy stopping, controlled performance at high wind speeds and system cut off beyond the high speed conditions.

It is an object of the present invention to provide a wind turbine with a passive pitching system governed by the centrifugal force of the spacer and the mass and the resisting force of the spring. It is also an object of the present invention to utilize the wind energy through proper coupling arrangement for regulating the speed of the rotor.

It is yet another object of the present invention to provide a closed loop digital control system for tracking the position of the spacer and the airfoil blades of the wind turbine.

It is yet another object of the present invention to provide a centrifugal mass to control the position of the airfoil blades at high speed condition. It is yet another object of the present invention to control the position of the airfoil blades by providing a triggering effect by means of motor.

STATEMENT OF THE INVENTION A wind power generation system with electromechanical means of start and stop control comprising

A. The airfoil blade (2) connected by arm to the assembly for generating the power from the wind.

B. The arm (1) connecting the blade to the hub for structural support of the blades.

C. The Pushrod (3) for bringing the airfoil blades from feathered to In-Wind position and vice versa.

D. The Spacer (4) engages and disengages with the couplers (6, 7) to control the operational mode of the turbine.

E. The spring (5) connected between the couplers (6, 7) with predetermined tension for holding and turning the coupler according to the rotational speed.

F. The pair of couplers (6, 7) for transmitting the torque from the motor to the airfoil blades whose one end is connected to the drive line and the other end is connected to the arm (1) and the air foil blades (2).

G. The centrifugal mass (8) for bringing the airfoil blade to feathered condition while the rotational speed exceeds the operating speed.

H. Motor(9) for transmitting the torque at start up condition to the arms & blades and during power generation stage it functions as generator(which is an additional embodiment) I. Motor shaft (10) for coupling the motor with the drive line.

J. Spider (11) for transmitting the torque from the motor (9) to the airfoil blades (2) through arms 0)·

In case of wind turbine the rotational speed of the airfoil blades should fall within the operating speed to prevent the runaway condition for generating the desired output and it should be started or stopped by means of pitch control.

Pitch control: Blade pitch control is the system which monitors and adjusts the inclination angle of the blades and thus controls the rotation speed of the blades. At lower wind speeds, the pitching system leads to an acceleration of the hub rotation speed, while at higher speeds, blade pitch control reduces the wind load on the blades and structure of the turbine. Over a certain wind speed the blade pitch control starts to rotate the blades out of the wind, thereby slowing and stopping the blades to avoid complete damage.

Runaway condition:

When the grid connection is lost, there is no back electromechanical force at the generator and the generator will run at no load condition. The energy received from wind during the course of time will cause the rotor to pick up more rotational speed. The increased rotational speed in turn will increase the energy captured from the wind. There is an upward spiral action that cumulatively increases the rotational speed to go beyond the rated speed over the time. If this condition is not stopped, this eventually will lead to catastrophic failure of rotor system.

Working conditions:

The present invention of wind turbine comprises of two modes of operation which controls the torque transmitted to the blades.

A. Feathered condition B. In wind condition

Feathered condition:

As shown in Fig 3(c) or Fig 3(d) or Fig 5(a) or Fig 5(c) when the leading edge of the airfoil blades is turned by a certain degree, the angle of attack at which it faces the approaching wind is changed. Angle of attack is a predominant factor in causing the airfoil blades to rotate at desired speed. In the feathered condition the position of blades resists the approaching wind to pass by which retards the rotation of blades thereby stopping the generating power.

In wind condition:

As shown in the Fig 3(a) or Fig 3(b) or Fig 5(b) when the leading edge of the airfoil blades faces the approaching wind, it passes over its profile smoothly making the airfoil blades to rotate at operating speed. The angle of attack of the airfoil blades at Inwind position favors rotation thereby generating power from the rotation of the air foil blades.

Operational modes:

In the present invention, three modes of operation can be mapped to the air foil blade position which is shown in Fig 1 or Fig 4(additional embodiment)

Start Mode:

The start mode as mentioned in Sl.no.1 of Fig 1 refers to the state where the airfoil blades are brought to the In-Wind condition as shown in Fig 3(a) or Fig 3(b) or Fig 5(b) by the engagement of spacer(4) between the arms of the couplers(6,7) by rotating the motor shaft in reverse direction. The airfoil blades are brought to Inwind position by the angular displacement of couplerl (6) which triggers linear movement of pushrod and the centrifugal mass is pulled by the couplers.

In the case of additional embodiment, the start mode as mentioned in Sl.no.1 of Fig 5 refers to the state where the airfoil blades are in feathered condition Fig 3(c) or Fig 3(d) or Fig 5(a) or Fig 5(c) while the spring is in ground state. Running Mode:

The Running mode as mentioned in Sl.no.2 of Fig 1 refers to the state where the spacer latched between the arms of the couplers is driven outwards from the coupling arrangement and the airfoil blades are still in In-Wind position Fig 3(a) or Fig 3(b) or Fig 5(b). Also the centrifugal mass retains its position as that of start mode. As soon as the system reaches the sustainable speed the centrifugal force on the spacer drives it outwards from the couplers. In the case of additional embodiment, the running mode as mentioned in Sl.no.2 of Fig 5 refers to the state where the airfoil blades are brought to ln-wind position and the spring is compressed by the rotation of spider.

Stop Mode: The stop mode as mentioned in Sl.no.3 of Fig.1 refers to the state where the airfoil blades are brought to the feathered condition. In the feathered condition as shown in Fig 3(c) or Fig 3(d) or Fig 5(a) or Fig 5(c) the position of blades resists the approaching wind to pass by which retards the rotation of blades thereby stopping the generating power and spacer is still in the outward position. The centrifugal mass is pushed away by the angular displacement of coupler. In the case of additional embodiment, the stop mode as mentioned in Sl.no.3 of Fig 5 refers to the state where the airfoil blades are brought to feathered position and the spring returns back to the ground state.

The method of starting and stopping the wind turbine by electromechanical means of coupling arrangement comprises of:

A. Airfoil blade (2) are brought to the Inwind condition from feathered condition by rotating the motor in reverse direction

B. Torsional (or) linear springs (5) installed between the couplers (6, 7) are compressed by the arms of the coupler and centrifugal mass (8) is pulled toward the hub.

C. Spacer (4) is positioned between the arms of the coupler and it is sensed by the sensor through a closed loop digital control system. D. Turbine is rotated in normal direction and power is generated from the turbine by the approaching wind

E. Centrifugal force on the spacer (4) drives it outwards from the couplers (6,7) while the turbine reaches sustainable speed and the position of spacer (4) is sensed by suitable sensor.

F. Void space is created between the arms of the couplers (6, 7).

G. Spring (5) remains in ihe compressed state due to transmission of torque from airfoil blades which is due to sustainable speed of the turbine.

H. Power generation is stopped while the turbine rotates beyond the cut-off speed with the absence of torque transmission thereby the Spring (5) is elongated and the airfoil blades are brought to feathered condition by linear movement of push rod (3).

(Or)

I. When the rotational speed exceeds the operating speed but transmission of torque exists, the centrifugal mass (8) slides away thereby turning the one end of the couplers (6, 7) and the airfoil blades (2) are brought to feathered condition by linear movement of push rod (3).

The method of starting and stopping the wind turbine (in additional embodiment) by providing a triggering effect by means of motor comprises of:

A. The spring (5) loaded with predetermined tension is in ground state while airfoil blade (2) is in feathered condition and it remains in the ground state at the startup condition.

B. The spring (5) gets compressed while the motor (9) become generator or a dynamic brake.

C. Push rod (3) gets activated by the rotation of spider (11).

D. The air foil blades (2) are to in-wind position by the linear movement of pushrod (3).

E. The airfoil blade (2) is in in-wind position as long as the load in the generator (9) continues.

F. The spring (5) will come back to ground state once the generator (9) losses the load.

G. The airfoil blades (2) are brought to the feathered position by the rotation of spider (11) which activates the linear movement of pushrod (3). BRIEF DESCRIPTION OF THE DRAWINGS

Fig.1 illustrates the various modes of operation of the turbine and airfoil blade position in each of the conditions.

Fig.2 illustrates the functional block diagram of the system during the operation condition of the turbine. Fig.3 a, b, c, d illustrates the operational modes of the present invention of wind turbine and the corresponding position of the spacer, spring and centrifugal mass in each mode.

Fig.4 illustrates a block diagram showing the steps involved in start and stop of the wind turbine by electromechanical means.

Fig.5 illustrates the various modes of operation of the turbine in the additional embodiment to the present invention and airfoil blade position and spring condition in each mode.

Fig.5 a, b, c illustrate the pictorial representation of the three modes of operational condition of wind turbine in the additional embodiment to the present invention and the corresponding position of the spring and airfoil blades in startup, running, stop mode respectively.

Fig.6 illustrates a block diagram of additional embodiment to the present invention showing the steps involved in start and stop of the wind turbine by triggering effect of motor.

DETAILED DESCRIPTION OF THE DRAWINGS

The other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure. It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.

Fig.1 illustrates the various modes of operation of the turbine comprising of electromechanical means for starting and stopping the turbine. The operational mode of the turbine and their corresponding airfoil blade (2) position are shown in the figure. At the start and running mode, airfoil blade (2) is in ln-wind position and in the stop mode the airfoil blade (2) is in feathered position. The operational modes and the position of airfoil blades (2) are explained below.

Fig.2 illustrates the digital control system used along with electromechanical means for starting and stopping the turbine. Digital Control system (DCS):

The Digital Control System (DCS) as shown in Fig 2 has

❖ Pulse Width Modulated -Voltage Source Inverter (PWM-VSI) control (A)

❖ Line sync UPF Control (B)

❖ Configuration selector and driver control interface (C)

❖ The Spacer Position Interface. (D)

❖ Inverter and Driver (E)

❖ Battery and Charger(F) A. The Pulse Width Modulated -Voltage Source Inverter (PWM-VSh control:

This section is primarily used when the turbine is operated in standalone mode. The function of this section is that the DC voltage from the inverter DC side section is compared with the internal reference and the inverter frequency and direction are set as required.

B. Line svnc UPF Control:

This section is primarily used when the turbine is connected to the grid. The prime function of this section is to control the inverter in parallel with the power grid line, to pump required excess current and withdraw the available excess current from grid/load in synchronization with the power grid voltage level. The required instantaneous additional power is taken from the battery source by the inverter and the excess power available is subsequently used to charge back and the battery acts as a load to consume the additional power available. By this action the current waveform is made in sync with the voltage and thus obtaining the near unity power factor. This achievement of unity power factor ensures the efficient power transfer to grid and usage by the loads.

C. Configuration selector and driver control interface: The objective of this section is to monitor the availability of grid power, wind speed and loads to be powered. According to the prevailing inputs the mode of operation is selected and to control the turbine operation to the maximum efficiency possible.

D. The Spacer Position Interface:

The spacer position interface is scaled to the proper level to be interfaced with the Digital Control System.

E. Inverter and Driver:

The Power devices are used as the switching components in the inverter. The inverter is driven by the configuration/ Driver control section. The signals are opto-isolated and fed to the power switching devices through the driver circuitry. The inverter is capable of handling the power requirements of the Induction Generator (IG) and the Load current.

F. Battery and Charger:

The Battery is the DC source which is used for

A. For the startup of the turbine when it is operated in without Grid supply conditions.

B. With Grid connected condition, to supply the required power to the inverter for current control in sync with the power line voltage to obtain near unity Power factor The charger is used to charge the batteries from the supply available at the DC side of the inverter during the standalone mode and from the excess power available during the current control in sync with the power line voltage when Grid power is available. Fig.3 (a) illustrates a wind turbine (VAWT) in start mode condition with electromechanical means for start and stop of the wind turbine. The airfoil blades (2) will be in feathered condition initially which should be brought to ln-wind condition for the operation of turbine. The present invention utilizes couplers (6,7) with one end directly coupled to the drive line and the other connected to the arm (1) of the assembly. The couplerl (6) connected to the drive line is coupled to coupler2 (7) by means of spring (5) at predetermined locations between the arms of the couplers (6, 7).The centrifugal mass (8) is connected to the coupler (6)· by means of link. The torque of the driving motor shaft is transmitted to airfoil blades (2) through the said couplers (6, 7) and the arm (1).

By rotating the motor shaft in reverse direction, the Spring (5) is compressed by the angular displacement of couplerl (6) thereby the spacer (4) latches between the arms of the couplers (6, 7) and the airfoil blades (2) are brought to ln-wind condition by the linear displacement of push rod (3) which is said to be the start mode of the turbine. The centrifugal mass is slide towards the hub by the angular displacement of couplerl (6).The position of spacer (4) is sensed by a suitable sensor mechanism through a closed loop digital control system.

Fig.3 (b) illustrates a wind turbine (VAWT) in Running-lnwind condition with electromechanical means for start and stop of the wind turbine. The system is rotated in normal direction as soon as the airfoil blades (2) are brought to ln-wind condition. When the turbine reaches sustainable speed, the centrifugal force on the spacer (4) which is latched between the arms of the couplers (6, 7) as said in start mode condition of turbine are driven outwards from the couplers (6, 7) thereby creating a void space between the arms of the couplers (6, 7) which is said to be the running mode of the turbine. The spring (5) remains in the compressed state and the centrifugal mass (8) also remains in the same position and as mentioned earlier. The position of spacer(4) is sensed by a suitable sensor mechanism through a closed loop digital control system. Fig.3(c) illustrates a wind turbine (VAWT) in stop mode at no torque condition with electromechanical means for start and stop of the wind turbine. When the system goes beyond the cutoff speed, power generation is stopped by control system thereby the system goes to no-load condition. The torque from the airfoil blades (2) will not be transferred thereby the Spring (5) is elongated due to the creation of void space creating an angular displacement of couplerl (6) thereby the airfoil blades (2) are brought to the feathered position by the linear movement of push rod (3).

Fig.3(d) illustrates a wind turbine (VAWT) in stop mode at torque condition where the rotational speed goes beyond the rated speed and the transmission of torque persists thereby the centrifugal mass is slided away since the centrifugal force of the corresponding speed exceeds the centrifugal force of centrifugal mass (8). So, the airfoil blades (2) are brought to the feathered position by the linear movement of push rod (3).

Fig.4 is a block diagram showing the steps involved in start and stop of the wind turbine.

B. Springs (5) installed between the arms of the couplers (6, 7) are compressed and centrifugal mass (8) is pulled toward the hub.

C. Spacer (4) is positioned between the arms of the couplers (6, 7) and it is sensed by the sensor through a closed loop digital control system.

D. Turbine is rotated in normal direction and power is generated from the turbine by the approaching wind

E. Centrifugal force on the spacer (4) drives it outwards from the couplers (6, 7) while the turbine reaches sustainable speed and the position of spacer (4) is sensed by suitable sensor.

F. Void space is created between the arms of the couplers (6, 7).

G. Spring (5) remains in the compressed state due to transmission of torque from airfoil blades which is due to sustainable speed of the turbine.

H. Power generation is stopped while the turbine rotates beyond the cut-off speed with the absence of torque transmission thereby the Spring (5) is elongated and the airfoil blades are brought to feathered condition by linear movement of push rod (3). (Or)

I. When the rotational speed exceeds the operating speed but transmission of torque exists, the centrifugal mass (8) slides away thereby turning the couplerl and the airfoil blades are brought to feathered condition by linear movement of push rod (3).

The operation of the wind turbine with start and stop control using pitch control mechanism is explained as follows:

While starting, the airfoil blades (2) will be in feathered condition which should be brought to the In-Wind condition for the operation of turbine. The couplers (6, 7) with one end connected to the drive line and the other end connected to the arms (1) and airfoil blades (2). The motor shaft is connected to couplerl (6) at the inner periphery of the hub of the assembly. At the outer periphery the coupler2 (7) is coupled to couplerl (6) for transmitting the torque from the motor. Springs (5) are connected between the arms of the couplers (6, 7) which control the rotation of coupler 1 under normal operation and in the condition of pitch control. The centrifugal mass (8) is connected to couplerl (6) by means of link. By rotating the couplerl (6) in reverse direction using the system as shown in Fig 2, the Spring (5) is compressed and the airfoil blade (2) is positioned by the movement of push rod (3) which paves the way for the spacer (4) to accommodate between the arms of the couplers (6, 7) (Fig 3), referred as start mode of turbine where the airfoil blades (2) are brought to the In-Wind condition. The centrifugal mass (8) is pulled towards the hub by the angular displacement of the coupler (1). The position of the spacer (4) as per the start mode or position of the airfoil blades (2) is sensed by a suitable sensor mechanism through a closed loop digital control system.

Once the airfoil blades (2) reach the In-Wind condition in the start mode, the system as shown in Fig 2 rotates the turbine in the normal direction. The couplerl (6) connected to motor shaft drives the coupler2 (7) which inturn rotates the turbine. The spacer(4) also rotates with the turbine and while reaching the sustainable speed the centrifugal force on the spacer(4) will push it away from the couplers (6, 7) thereby creating a void space between the arms of the couplers (6, 7) (Fig 4), referred as running mode of turbine. The position of the spacer (4) as per the running mode or position of the airfoil blades (2) is sensed by a suitable sensor mechanism through a closed loop digital control system. The position of the spring (5) remains in the compressed state due to transmission of torque from airfoil blades (2) which is due to sustainable speed of the turbine. The centrifugal mass (8) also remains in the same position as explained in the earlier case.

When the turbine rotates beyond the cut-off speed, power generation is stopped using the system as shown in Fig 2, resulting in no load condition of the entire system. Under no load condition, the transmission of the torque from the airfoil blades (2) will not be transferred to couplers (6, 7), thereby the spring (5) is elongated and the airfoil blades (2) are brought to feathered condition, referred as the stop mode of the turbine. In some cases, the transmission of torque exists while the rotational speed exceeds the rated speed where the centrifugal force of the turbine exceeds the centrifugal mass (8). So, the centrifugal mass (8) is driven away thereby causing angular displacement of couplerl (6) and the airfoil blades (2) are brought to the feathered condition by the linear movement of push rod (3).

The following description of diagrams are with reference to the fig 5, fig 5 a, b, c and Fig.6 which is an additional embodiment to the present invention described so far.

Fig.5 illustrates the various modes of operation of the turbine and airfoil blade position and spring condition in each mode. The operational mode of the turbine and their corresponding airfoil blade (2) position are shown in the figure. The airfoil blades (2) will be in feathered condition while the spring (5) is in ground state at the startup and stop mode of the turbine. The airfoil blades (2) will be in ln-wind condition while the spring (5) is in compressed state at the running mode of the turbine.

Fig.5 (a) illustrates a wind turbine (VAWT) in start mode condition of the wind turbine. The spring (5) loaded with predetermined tension is in ground state while airfoil blade (2) is in feathered condition. The spring (5) remains in the ground state throughout the starting mode of the turbine.

Fig.5 (b) illustrates a wind turbine (VAWT) in Running-lnwind condition of the wind turbine. When the motor (9) become generator or a dynamic brake the spring(5) gets compressed thereby the push rod(3) gets activated by the rotation of spider(11) and brings the air foil blade(2) to in-wind position. Fig.5(c) illustrates a wind turbine (VAWT) in stop mode condition of the wind turbine. The airfoil blade (2) is in in-wind position as long as the load in the generator (9) continues and once the generator (9) losses the load the spring (5) comes back to ground state and thereby bringing the airfoil blade to feathered position.

Fig.6 is a block diagram (of additional embodiment) showing the steps involved in start and stop of the wind turbine

C. Push rod (3) gets activated by the rotation of spider (11).

D. The air foil blades (2) are brought to in-wind position by the linear movement of pushrod (3).

G. The airfoil blades (2) are brought to the feathered position by the rotation of spider (11) which activates the linear movement of pushrod (3).

It will be obvious to a person skilled in the art that with the advance of technology, the basic idea of the invention can be implemented in a plurality of ways. The invention and its embodiments are thus not restricted to the above examples but may vary within the scope of the claims.

Further the above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.

Claims

CLAIMS:

1. The wind power generation system or a wind turbine, with electromechanical means of start and stop control comprising

B. The arm (1) connecting the airfoil blade to the hub for structural support of the airfoil blades.

D. The Spacer (4) for engage and disengage with the coupling arrangement to control the operational mode of the turbine.

E. The spring (5) connected between the couplers (6, 7) with predetermined tension for holding and turning the couplers according to the rotational speed.

F. The couplers (6, 7) for transmitting the torque from the motor to the airfoil blades.

H. Motor(9) for transmitting the torque at start up condition to the arms & blades and during power generation mode it functions as generator(which is an additional embodiment)

I. Motor shaft (10) for coupling the motor with the drive line.

J. Spider (11) for transmitting the torque from the motor (9) to the airfoil blades (2) through arms (1)·

2. The system as claimed in claim 1 wherein the plurality of airfoil blades (2) are connected operably to the system by means of arm (1) and the arms (1) are attached to the hub for transmitting the torque to the airfoil blades (2).

3. The system as claimed in claim 1 wherein the couplers (6, 7) are connected to hub for transmitting the torque to the airfoil blades (2).

4. The system as claimed in claim 1 wherein the spacer (4) engages or disengages with the couplers (6, 7) and controls the operational mode of the turbine.

5. The system as claimed in claim 1 wherein the spring (5) installed between the arms of the couplers (6, 7) compress or elongate thereby controlling the operational mode of the turbine.

6. The system as claimed in claim 1 wherein the pushrod (3) connected at trial edge of the blades brings the airfoil blades to ln-wind or feathered condition depending upon the operational mode of the turbine.

7. The system as claimed in claim 1 wherein the couplers (6, 7) transmits torque from the motor shaft to the airfoil blades(2) at start mode and transmits torque from the airfoil blades(2) to the generator while generating power.

8. The system as claimed in claim 1 wherein the start mode, the couple (6) is rotated in reverse direction and the spring (5) is compressed thereby bringing the airfoil blades (2) to ln-wind position.

9. The system as claimed in claim 1 wherein the spacer(4) is latched between the arms of the couplers (6, 7) by the creation of void space accounting from the compression of Spring(5).

10. The system as claimed in claim 1 wherein the running mode, the spacer (4) is driven outwards from the couplers (6, 7) while the turbine reaches sustainable speed.

11. The system as claimed in claim 10 wherein the spacer (4) is attached to a spring to latch or retain the spacer (4) between the arms of the coupler at start mode condition of turbine.

12. The system as claimed in claim 11 wherein the spring (5) remains in compressed state and the airfoil blades (2) are in ln-wind position.

13. The system as claimed in claim 1 wherein the stop mode, the torque is not transmitted from airfoil blades (2) to the couplers (6, 7) when the generator runs in no load condition.

14. The system as claimed in claim 13 wherein the couplerl (6) is displaced angularly by the elongation of the spring (5) which triggers linear movement of push rod (3).

15. The system as claimed in claim 13 wherein the couplerl (6) is displaced angularly by the sliding movement of centrifugal mass (8) when the rotational speed exceeds and the transmission of torque exists.

16. The system as claimed in claim 14 wherein the airfoil blades(2) are brought to feathered position by the linear movement of push rod(3).

17. The system as claimed in 1 where in the method of starting and stopping the wind turbine by electromechanical means of coupling arrangement comprises of:

A. Rotating the motor in reverse direction, such that the airfoil blade(s)(2) are brought to in wind condition from feathered condition.

F. Void space is created between the arms of the couplers (6, 7).

18. The system as claimed in 1 where in the method of starting and stopping the wind turbine by electromechanical means of coupling arrangement comprises of:

A. Rotating the motor in reverse direction, such that the airfoil blade(s)(2) are brought to in wind condition from feathered condition. B. Springs (5) installed between the arms of the couplers (6, 7) are compressed and centrifugal mass (8) is pulled toward the hub.

F. Void space is created between the arms of the couplers (6, 7).

H. When the rotational speed exceeds the operating speed but transmission of torque exists, the centrifugal mass (8) slides away thereby turning the couplerl and the airfoil blades are brought to feathered condition by linear movement of push rod (3).

19. The system as claimed in 1 where in the spring (5) loaded with predetermined tension is in ground state while airfoil blade (2) is in feathered condition and it remains in the ground state at the startup condition.

20. The system as claimed in claim 1 where the spring(5) gets compressed while the motor(9) become generator or a dynamic brake thereby the push rod(3) gets activated by the rotation of spider(11) and brings the air foil blade(2) to in-wind position.

21. The system as claimed in claim 1 wherein the airfoil blade (2) is in in-wind position as long as the load in the generator (9) continues and the spring(5) will come back to ground state once the generator(9) losses the load thereby bringing the airfoil blade (2) to feathered position.

22. The method of starting and stopping the wind turbine (in additional embodiment) by triggering effect of motor comprises of: A. The spring (5) loaded with predetermined tension is in ground state while airfoil blade (2) is in feathered condition and it remains in the ground state at the startup condition.

C. Push rod (3) gets activated by the rotation of spider (11).

23. The system as claimed in 1 where in the wind turbine with start and stop control using electromechanical means and triggering effect of motor (additional embodiment) substantially as herein described with respect to the accompanying drawings.