DE2922972C2 - Wind turbine control system - Google Patents

Description

The invention relates to a wind turbine control system as specified in the preamble of claim 1 Art.

The basic problem with power generated with wind turbines is that the power generated in a Supplied in the form in which it is used for public power supply networks or for isolated power supply stations is usable. The amount of available power is determined by wind speed and gusts of wind influenced. When alternating current electrical power is powered by a wind turbine Synchronous generator is generated, must have both the frequency and the phase of the AC power and the AC power itself can be regulated before the AC power is delivered to users or fed into existing power supply networks can be.

It has been shown that the regulation that is used to generate of electrical power required by a synchronous generator driven by a wind turbine is, can be done by changing the angle of attack of the rotor blades in a way that the Blade pitch control for an aircraft propeller is analogous. The US-PS 23 63 850 describes a through a wind turbine driven alternator with one controlled by a speed controller Device for changing the blade angle between full vane or flag position and full power position. In addition, there are devices for regulating the electrical output frequency, the phase , and the power and to switch off the electrical generator at wind speeds that are used to generate are too high or too low for the desired output. The US-PS 25 47 636 describes a automatic speed control for a wind turbine to regulate the charging speed of a storage battery, where the speed control consists of mechanical devices that respond to the wind speed respond and change the blade pitch. The US-PS 25 83 369 describes a similar scheme for mechanical adjustment of the blade pitch angle.

around a relatively constant speed of the electrical generator and thus a relatively constant alternating current output frequency maintain.

The US-PS 27 95 285 describes a scheme for changing the rate of change of the load, the speed or the voltage of a motor driven by a wind turbine by changing it the angle of incidence of the rotor blades of the wind turbine in the manner of a closed control loop. The US PS 28 32 895 describes a further device for adjusting the blade pitch angle of a wind turbine, wherein the device is responsive to a predetermined load on a battery or to sudden gusts of wind.

These known control systems have the disadvantage.

that they do not respond quickly enough or with sufficient accuracy to cope with the stresses in to limit the blades and other mechanical parts to permissible values. Also, the known control systems are overly influenced by windbusters and turbulence and cannot be satisfactory Power control maintained over a wide range of wind speeds to a Allow connection to a standard power supply network. Generated at high wind speeds even weak turbulence can cause considerable fluctuations in power and the generator is disconnected from the grid.

It is the object of the invention. in the case of a wind turbine control system of the generic type, the response sensitivity and speed.

According to the invention, this object is achieved by what is stated in the characterizing part of claim 1 Features solved.

The wind turbine control system according to the invention maintains an operating variable, e.g. B. the electrical alternating current frequency, the phase, the speed, the torque and the power, within the desired tolerances, by automatically influencing the blade pitch angle of the rotor blades in such a way that the effects wind gusts and turbulence are minimized.

It also reduces the stress on the rotor blades and other mechanical parts.;. According to the invention, the blade angle z. B. regulate as a function of the generator speed or the generator power depending on the connection of the generator to a power transmission network. The wind turbine control system according to the invention is adaptive, since it takes into account the respective size or wind speed and changes in the wind speed. The wind turbine lock system works electronically, is therefore fast acting and can be implemented inexpensively with digital computers or microprocessors. Advantageous refinements of the invention form the subject of the subclaims.
In the embodiment of the invention according to claims 2 and 5, the wind turbine control system contains a blade pitch control which generates P, I and D control signals, the control gains being continuously changed as a function of the wind speed.

In the embodiment of the invention according to claim 6, the wind turbine control system contains an integrator, which follows the blade pitch even when the control is inactive.

In the embodiment of the invention according to claims 7 and 8, default devices the blade pitch angle is specified so that the blade stress and shaft torque changes can be minimized during startup and shutdown transitions. The control gains are thereby continuously changed as a function of the wind speed to improve stability and transient response to optimize.

In the embodiment of the invention according to claims 12 and 13, the blade pitch controller is very sensitive to wind gusts and responds quickly via an anticipatory control signal, which during faster changes in the wind conditions are added to the control signals to reduce mechanical loads to minimize.

In the embodiment of the invention according to claim 14, the wind turbine control system maintains the output power of the synchronous generator at a predetermined value and at a predetermined frequency and regulates the feeding of the alternating current power into a power supply network automatically.

Several embodiments of the invention are described below with reference to the drawings described in more detail. It shows

1 shows an example of a wind turbine,

Fig. 2 is a circuit diagram showing the mutual relationship between the rotor blades, the electrical Power generation system and the wind turbine control system shows

Fig. 3 is a circuit diagram of the control system of Fig. 2,

4 shows a diagram of the acceleration specification for the blade angle of attack,

5 shows a diagram of the default delay for the blade pitch angle.

6 shows a block diagram of the rotor speed setting device.

7 shows a block diagram of the wind anticipation specification device,

8 shows a block diagram of the shaft torque setting device,

9 shows a block diagram of gain specifications for the specification device from FIGS. 6 and 8,

FIG. 10 is a block diagram showing a change in the gain setting shown in FIG. 9 using an assumed wind speed and

11 shows a block diagram of further setting devices for the blade pitch angle.

Fig. 1 shows an example of a wind turbine construction, which consists of two diametrically opposed, the same rotor blades 10, which are typically 30.5 m to 91 m in diameter, and is mounted on an open lattice tower 12, which ensures a sufficient ground clearance of the leaves and brings them into an area with relatively high wind speeds. The rotor blades 10 are generally made of aluminum, steel or fiberglass. The electric power generation unit and others mechanical parts are contained in a cell 14 and mounted on a platen, not shown. The rotor blades 10 are arranged at the end of the cell 14 downstream of the tower 12 so that they do not Can touch the tower if they hit under shock load. Yaw control (not shown) can be provided be in order to rotate the cell 14 and the rotor blades 10 in the event of slow changes in a weather front Holding downwind, start allowing the rotor blades to move freely about the yaw axis and to follow sudden shifts in wind direction. The cell 14 contains the hub for the rotor blades 10, a transmission, a hydraulic adjustment device for the rotor blades, a synchronous generator for generating of electricity and the necessary gear drives and control equipment.

Figure 2 shows the rotor blades 10 attached to a hub 16 and the electrical power generation system and the wind turbine control system contained in cell 14 of FIG. The electric Power generation system shown as a synchronous generator 26 and the mechanical part of the wind turbine control system for the rotor blades 10 are generally known and will therefore not be discussed in detail described.

A shaft 18 is connected at one end to the hub 16 and at the other end to a gear 20, which translates the rotary motion of the wind turbine in a ratio that of the Polnaaryahl in the Synchronous generator 26 and is dependent on the desired output frequency of the synchronous generator. In In a typical installation, a wind turbine speed of 40 RPM will be used by the gearbox 20 in FIG implemented a rotational speed of 1800 rpm in order to generate a 60 Hz alternating current with a standard synchronous generator to create.

The output shaft 22 of the transmission 20 is connected to the synchronous generator 26 at its other 5th end. A conventional slip clutch can be inserted between the output shaft 22 and the synchronous generator. The synchronous generator 26 typically has a constant magnetic field t .-, nd an armature which supplies alternating current in synchronism with the armature rotation and at a frequency which is the product of the number of pole pairs in the synchronous generator and the rotational speed in revolutions per minute. The electrical output power of the generator 26 is output via a line 28, a switch 40 and a line 34 to a load (not shown). The generator 26 may have a single phase or a three phase output. The load can be a storage battery or other energy storage, in which case conversion to direct current may be required, or the line can be delivered directly to a remote facility, in which case the frequency and phase of the output power can be critical. Typically, however, the AC power from generator 26 is fed into a public utility network and transmitted to a remote location by power transmission lines. In this case the phase relation between the utility grid and the generator output power is quite critical as the phase relationship is a measure of the power being transferred from one to the other and a phase mismatch between the output of the synchronous generator 26 and the power transmission grid not only reduces the efficiency of the system, it actually does can lead to the fact that power is taken from the power transmission network instead of supplied. Changes in performance can lead to overheating and damage to the synchronous generator 26. Therefore, an automatic frequency and phase synchronization circuit 30 is connected to the synchronous generator 26, the structure of which is known. The synchronization circuit 30 ensures that the frequency / and the phase α of the synchronous generator 26 are adapted to those of the load or the network before the synchronous generator pulls

is switched. Signals which indicate the frequency / and the phase α at the synchronous generator output are fed to the synchronization circuit 30 via a signal line 32. A signal line 36 also supplies the synchronization circuit 30 with the frequency / and the phase α of the load or of the network, which appear on a line 34 when the switch 40 is open. The automatic synchronizing circuit 30 compares the frequency and the phase of the synchronous generator 26 with those of the load and, if synchronism is present, a discrete signal is emitted by the synchronizing circuit 30 over a line 38 which closes the switch 40 and activates the synchronous generator. The discrete signal on line 38 is also fed to the blade pitch controller 46 described below.

When the synchronous generator 26 operates at the desired frequency, but not with the load in Phase is, a signal is sent from the synchronizing circuit 30 via a signal line 42 to the bias angle controller 46 output, which is the number of rotors and thus the frequency and phase at the output of the synchronous generator adjusted in order to carry out the synchronization described below in connection with FIG.

Since the output frequency of the synchronous generator 26 is controlled by the rotational speed of the wind turbine requires maintaining a predetermined electrical output frequency, e.g. 60 Hz, a precise regulation of the wind turbine speed of rotation. The most practical Way of regulating the wind turbine speed and thus the generator speed and -output frequency consists in changing the angle of attack of the rotor blades in order to attach the wind turbine to it to prevent accelerating with increasing wind speed or with decreasing wind speed to slow down. To prevent speed fluctuations with unpredictable gusts of wind occur, the regulation must be very sensitive.

Referring to Figure 2, a pitch actuator 44 is provided which includes known hydraulic actuators and connections similar to those used on aircraft propellers, but on a larger scale. A control valve in the hydraulic part of the pitch actuator 44 responds to an electrical signal from the blade pitch controller 46, which is transmitted via a line 48. As a control valve, the angle of attack actuator 44 contains a two-stage hydraulic unit with a high adjusting speed, which moves the rotor blades 10 via connections and levers (not shown). The signal on line 48 is proportional to the blade pitch error ß _E , which is the difference between the target or reference blade pitch angle ß _R , which is provided by the blade pitch controller 46 (Fig. 3) according to a plan, and the actual blade pitch angle ß _A. The actual blade angle of attack β _A is measured by a transducer 50, which is arranged in the angle of attack actuator 44, and an electrical signal representing the actual blade angle of attack is output via a signal line 52 to the blade angle of attack controller 46.

The blade angle of attack controller 46 is used to influence the angle of attack of the blades 10 so that mechanical stresses during start-up and shutdown and during gusts of wind are minimized. It is also used as part of a closed loop to control the wind turbine rotor speed and thus the electrical output frequency in one control mode or the generator output or shaft torque in another control mode, depending on the type of load. For example, when the wind turbine and generator 26 are used as an isolated generator station, the wind turbine rotor speed control is generally sufficient. However, when the generator 26 is switched to a mains, shaft torque or generator power control is required. In either case, the control system must respond to wind turbulence in order to maintain a reasonably constant generator output. The blade pitch controller 46 specifies the target blade pitch angle β _R , taking into account selected operating states and reference signals, and provides for a quick adjustment of the blade pitch angle from a full flag stcüung. i 90 in είπε power steering of 0 °. Since the rotor blades 10 are not flat, but rather have a certain twist, the angle of attack in degrees is related to the pitch of the blade in V »of the outer distance along the blade from the hub 16.

The speed of rotation is used to provide the blade pitch register 46 with the necessary data of the wind turbine rotor is sensed by a transducer 54 connected to the hub 16, which is for example a gearwheel to which a magnetic

table sensor is assigned, which supplies an electrical signal proportional to the rotor speed N _{R via a line 56.} A similar transducer 58 is connected to the shaft of the synchronous generator 26 to provide an electrical signal over a line 60 which is proportional to the speed N _{c of} the synchronous generator. A transducer 62, for example a strain gauge or several strain gauges with different orientations, is connected to a shaft in the transmission 20 or to the shaft 18 or 22 in order to sense the shaft torque Q and to supply the blade pitch controller 46 with a signal proportional thereto via a line 64. The output power (or the output current) P _{c of} the synchronous generator 26 can be measured and fed to the blade pitch controller 46 via a signal line 66 which is connected to the output line 28 of the synchronous generator. Further signal transmitters, amplifiers and / or attenuators may be required, but have not been shown for the sake of simplicity.

In addition, the blade pitch controller 46 provides several sources for fixed or variable reference signals connected, which are simple voltage packs in analog format or a digital word in

Digital format can act. A rotor speed reference signal N _R REF is generated in a block 69 and fed to the controller 46 via a line 70. A torque reference signal β i? £ F is generated in a block 67 and sent to the controller 46 via a line 68

fed. A reference signal denoted by AN _R REF , which is used for overspeed control, is generated in a block 71 and fed to the controller 46 via a signal line 72. A signal labeled FLAG POSITION which is used to bring the wind turbine rotor blades into the flag position.

is generated in a block 73 and fed to the controller 46 via a signal line 74 and a switch 76.

The wind speed is determined by a wedge

speed sensor 78 is sensed which is attached to the cell 14 of Fig. 1 or some other location where it is not affected by the rotation of the wind turbine. The wind speed sensor 78 measures the actual wind speed and outputs a signal indicating this via a signal line 80 to an averaging circuit 82 , which is an electronic integrator or a digital or microelectronic unit which carries out statistical processing and the average Wind speed determined over a selected period of time. The output signal V _{WA of} the averaging circuit 82 , which represents the mean wind speed, is output to the controller 46 via a signal line 84.

For the purposes of the present description of an exemplary embodiment, it is assumed that the synchronous generator 26 begins to generate usable power at a wind speed of 12.9 km / h and delivers its nominal output power of, for example, 100 kW at a wind speed of 29 km / h. It is further assumed that the nominal rotor speed is 40 rpm, at which the generator 26 generates an output alternating current with a frequency of 60 Hz.

The details of an embodiment of the blade pitch regulator 46 of FIG. 2 are shown in the form of a block diagram in FIG. 3. The controller 46 consists of an acceleration setting device 86, a rotor speed setting device 88, a wind anticipation setting device 90, a torque setting device 92 and a deceleration setting device 94. The operation of the wind turbine can be divided into four operating modes, namely start-up, rotor speed control, torque control (or power control) when the wind turbine is running is connected to a public power supply network, and flagging or disconnection. The controller 46 provides open loop control of the rotor blade angle of attack during start-up and shutdown and a closed-loop control of the rotor blade angle of attack (ie with feedback) for the speed and torque (or power) control. In addition, the gains in the rotor speed setting device 88 and the torque setting device 92 are changed by a gain setting device 95 via a signal line 97, taking into account the wind speed.

Each of the five setting devices 86, 88, 90, 92 and 94 provides an output signal which represents a nominal blade pitch angle for the particular operating conditions of the wind turbine and is referred to as a blade pitch angle reference signal. The output signal of the acceleration specification device 86, that is to say an acceleration blade pitch angle reference signal β _s, appears on a signal line 96 and is fed to a maximum value selection circuit 98 as an input signal. The output signal of the rotor speed setting device 88, ie a rotor speed regulating blade pitch angle reference signal β _N appears on a signal line 100 and is fed to a summing point 102. The output signal of the wind anticipation setting device 90, ie a wind anticipation blade pitch angle reference signal β _ANT appears on a signal line 104 and is also fed to the summing point 102 , where it is added to the rotor speed control blade pitch angle reference signal β _N

will. The output signal of the summing point 102 on a signal line 106 is therefore the sum of the rotor speed control blade pitch angle reference signal β _N and the wind anticipation blade pitch angle reference signal β _A ^ _T. The signal on line 106 is also provided to the maximum value selection circuit 98 as an input signal.

The output signal of the torque setting device 92, ie a torque control blade pitch angle reference signal β _Q appears on a line 108 and is fed to a summing point 110 , where it is also added to the wind anticipation blade pitch angle reference signal β _ANT on the line 104 . The output signal of the summing point 110 is output via a line 112 as a third input signal to the maximum value selection circuit 98.

The maximum value selection circuit 98 selects the signal on lines 96, 106 or 112 which requires the greatest blade pitch angle, ie the blade pitch angle! the flag control or 90 ° closest to it and lets this signal through. During the start of the wind turbine, the selected signal will normally be the acceleration blade pitch reference signal β _s on line 96 and, as the rotor speed increases and approaches rated speed, the selected signal will normally be either the signal on line 106 or the signal on line 112 be, depending on whether the synchronous generator 26 is connected or not.

The output signal of the maximum value selection circuit 98 on a line 114 is fed to a summing point 116 as an input signal. The FLAG POSITION reference signal on line 74 is also provided as an input to summing point 116. If, however, the switch 76 in the line 74 is open, no signal appears on the line 74 and the output signal of the summing point on a line 118 is identical to that on the line 114, ie with the output signal of the maximum value selection circuit 98.

The output signal of the delay setting device 94, ie a delay sheet signal ß _D appears on a signal line 120 and is fed as the other input signal together with the signal on the line 118 to a minimum value selection circuit 122. The minimum value selection circuit selects the signal on lines 118 or 120 and lets through the signal which requires the smallest blade angle of attack, ie the blade position which is closest to the full power position or 0 °. During normal operation, the signal selected by the minimum value selector circuit 122 is that on line 118. However, if the wind turbine is to be shut down quickly, the vane switch 76 is closed and the VANISH LUNG reference signal appears on line 74. This signal is requested a very large blade angle. At this time, the signal on line 120, ie the acceleration blade angle reference signal β _D , defines a smaller blade angle of attack and is the signal which is selected by the smallest value selection circuit 122. The selection of the signal β _n makes it possible to limit the speed with which the blades 10 are brought into flag control in order to minimize the stresses on the blades during deceleration and to limit the negative torque generated by the rotor.

The output signal of the minimum value selection circuit

122 on a line 124 is referred to as the resulting blade pitch angle reference signal β _R and fed to a summing point 126 and compared with the actual blade pitch angle signal β _A on line 52 in order to generate the blade pitch angle error signal β _E on line 48. The latter signal is fed to the angle of attack actuator 44 of FIG.

The resulting blade pitch angle reference signal β _R on the line 124 is also used to track the integrator in the rotor speed setting device 88 and in the torque setting device 92 and fed to both setting devices via a signal line 128.

The default devices 86, 88, 90, 92 and 94 are described with reference to FIGS. 4 through 8, respectively described in detail.

To start the wind turbine, the flag position switch 76 is opened, whereby the flag position reference signal on the line 74 is switched off. The signal ß *. that generated on line 96 by acceleration presetting device 86 is the signal selected at this time and it causes the angle of attack of rotor blades 10 to move out of a feathered position of + 90 °, in which no lift and therefore no torque is generated and is moved to the full power position of 0 ^c . As the speed of the rotor increases, the torque delivered by the rotor increases under certain conditions of the blade angle and rotor speed. There are some rotor speed and blade angle conditions in which negative torque or deceleration occurs. As a result, the speed of the blade pitch change during start-up is not arbitrary, but must be specified in accordance with the particular characteristics of the wind turbine. If the blade angle is changed too quickly out of the plume position, the flow on the rotor blade can stall. As a result, a controlled change in the blade pitch angle is required. Changing the pitch angle at a fixed speed from the vane position until the wind turbine rotor reaches its rated speed is an alternative that has proven useful as long as the pitch speed is changed quickly to prevent the rotor blade from dwell at speeds, stimulate the system resonances. The start-up time of the wind turbine decreases with increasing wind speed. A rotor with greater inertia will take more time to accelerate. The acceleration of the blade increases rapidly with the speed of rotation.

Admittedly, sufficient power can be achieved during the acceleration of the wind turbine by changing the rotor blade angle of attack from the feathered position to full power at a fixed speed, considerably better power, which results in faster acceleration and less stress at all wind speeds, can, however, be achieved by specifying the blade pitch as a function of the mean wind speed V _WA and the rotor speed N _R. 4 shows, in the form of a diagram, a bivariate acceleration specification, the optimal acceleration blade angle of attack being plotted against the wind speed for various rotor speeds. The minimum starting angle of attack is specified as a function of the mean wind speed V _WA and the rotor speed N _R. The specification according to FIG. 4 is implemented in the acceleration presetting device 86 of FIG. 3, in which the two input signals V _WA and N _{R appear} on the signal lines 84 and 56 and the output signal on the line 96 is the acceleration blade pitch angle reference signal β _s , which accordingly Fig. 4 is specified. Successful implementation? ata the simplest digital via a read-only memory, but analog circuits can also be used. According to

ίο Fig. 4 is a blade pitch angle for the start or 0 rpm of + 70 ° or more, depending on the wind speed. When the rotor speed increases and the synchronous generator 26 is supplied with a torque, the blade pitch angle is gradually reduced to 0, until the wind turbine rotor reaches its Nerm speed. The curves shown in Fig. 4 include Minimum blade pitch limits that prevent the wind turbine rotor from doing so. Acceleration torques produce which is greater than about 200% (or any other desired limit) of normal Nominal torque are, so that the blade loads and the arrangement of rotor shaft 18 and Transmission 20 transmitted torque can be minimized. During the start-up of the wind turbine the rotor blade pitch angle exclusively through the Acceleration specification device 86 set.

In the figures, although it is not shown, the rotor speed input signal .V _R acceleration setting means 86 of FIG. 3 may be replaced with only minor system changes by the generator speed signal N _c, as there is a direct relationship between rotor speed and generator speed via the gear 20 gives. The overall shape of the curves of Figure 4 will not change.

When the wind turbine speed increases in accordance with the acceleration presetting device 86, the rotor speed approaches the value preset in the rotor speed presetting device 88 by the signal N _R REF on the line 70. During start-up, the Istrotordrehzahl N _R on the line 56 will always be less than the Soiirotordrehzahl N _R REF , and the output signal ß _{N of} the rotor speed setting device 88 on the line 100 will require a small blade angle, that is, if an underspeed is sensed, the Rotor speed; 'ü-presetting device 88 specify a small blade pitch angle in order to try to increase the speed and bring the rotor and the synchronous generator 26 to the target speed. The maximum value selection circuit 98 will not let the signal on the line 106 through at this time, since a larger blade pitch angle is required by the signal β _s on the line 96. When the rotor speed N _R increases and approaches the value selected by the signal N _R REF , the signal ß _N requires a larger blade pitch angle, while the signal ß _s requires a smaller blade pitch angle, and a point is reached at which the control of the Blade angle of attack is taken over by the rotor speed setting device 88.

According to FIG. 3, the rotor speed setting device 88 receives as input signals the steering rotor speed N _R REF on the line 70, the actual rotor speed N _R on the line 56 and the peak speed reference signal AN _R REF on the line 72.Signals are also sent to the rotor speed setting device 88 by the automatic synchronization circuit 30 (Fig. 2) via lines 38 and 42 supplied. The feedback of the blade angle reference signal ß _R takes place via the line

device 128, and reinforcements for the default device 88 are delivered over line 97.

In principle, the rotor speed setting device 88 compares the actual rotor speed N _R with the solr rotor speed N _R REF and generates a rotor speed error signal, on the basis of which the blade pitch angle ß _{s is} specified by the P, I and D controllers, so that a stable, quickly responding system results Deviations in the rotor speed and thus in the alternating current output frequency, which are caused by gusts of wind or by loss of electrical load, are minimized. The rate of change of the rotor speed is also monitored for an additional lead compensation. The peak or overspeed signal AN _R REF is only used when the synchronous generator 26 is connected. The detailed implementation of the rotor speed setting device 88 is shown in FIG.

6, the Istrotor speed signal N _R on line 56 is compared with the target rotor speed signal N _R REF on line 70 at a summing point 130 and a speed error signal proportional to the difference between the two signals is generated on a signal line 132. The signal on the line 42 can be added to the signal N _R REF on the line 70 by means of a summing point 131 in order to establish phase synchronism between the generator 26 and the load, which is described in more detail below. The signal N _R on the line 56 is also fed to a differential or D-circuit 134, and the output signal of the D-circuit 134. e: in advantage signal, is applied to a gain multiplier circuit 138 via a line 136. The gain of the multiplier circuit 138 is variable as a function of the wind speed and is shown as Signa] Κ _Λ on a signal line 97a. The variable gain is described in more detail in connection with FIG. The output of multiplier 138 is applied to summing junction 130 over signal line 142 in the same direction as signal N _R so that the signal appearing on line 132 is actually the rotor speed error plus a constant times the rotor speed change rate.

A switch 144 is provided in line 72, which is normally open and thereby prevents the overspeed signal AN _R REF from being applied to summing point 130. However, if the synchronous generator 26 is connected to a power supply network, the blade pitch control is switched to the torque specification device 92 (Fig. 3) and the switch 144 is closed by the discrete signal on the line 38, so that the signal AN _R REF is applied to the summing point 130 will. The signal AN _R REF has such a magnitude and direction that it is added to the signal N _R REF , thereby increasing the nominal generator speed to a value above the nominal speed of 1800 rpm, depending on the magnitude of the signal AN _R REF Da, however the signal AN _R REF is only used when the synchronous generator 26 is connected and when the blade pitch control has been switched to the torque specification device 92 of FIG. 3, the signal AN _R REF acts as an overspeed protection.

A signal appears on line 42 when the synchronous generator 26 of Fig. 2 is at the desired frequency but is not in phase with the load, this signal being of such magnitude and direction that the rotor reference speed N _R REF on line 70 is temporary is increased or decreased. The presence of the signal on line 42 which is added to the signal N _R REF at summing point 131 will adjust the rotor speed slightly until phase synchronism is achieved, at which time the signal on line 42 becomes zero.

Assume that switch 144 is open and that no signal appears on line 42. That

The signal on line 132, which represents the rotor speed error plus a constant times the rate of change of the rotor speed, is then fed to P, I and D controllers, which together generate the signal β _x on line 100. The P controller contains a gain multiplier circuit 146 which has a variable gain K _NP which is specified via a signal line 97b. The output of the multiplier circuit 146 is applied as an input to a summing junction 150. The I controller contains a multiplier circuit 152 which has a variable gain K _n , which is specified via a line 97c. The output of multiplier circuit 152 is applied over line 156 as an input to summing junction 158. The output signal of the summing point 158 is applied via a line 160 to an integrator 162, the output signal of which is applied via a line 164 to the summing point 150, where it is added to the proportional control signal.

Furthermore, an integrator readjustment is used in order to keep the integrator Iii2 close to the resulting reference blade angle of attack β _R when the control is inactive. The integrator output signal on line 164 is applied to a summing point 166 and compared with the feedback signal β _R on line 128. The initial signa! Suction point 166, which is e: in blade pitch error signal, is applied via line 168 to an amplification circuit 170 having a dead zone as shown in FIG. The amplification circuit 170 has the task of forcing the integral control signal to follow the blade pitch angle reference signal β _R only if the blade pitch angle predetermined by the integrator 162 deviates considerably from the resulting reference blade pitch angle β _{R in the rotor speed control.} The dead zone ensures that no tracking takes place if the predetermined blade angle of attack on line 164 is close to that indicated by the resulting reference blade angle of attack β _R. The output of gain circuit 170 is applied over line 172 to summing junction 158 and added to the integrator input signal on line 156, the signal on line 172 being zero if the blade pitch error is within the dead zone and not equal to zero and is added to or subtracted from the integrator input if the blade pitch error is outside the dead zone.

The D controller includes a multiplier circuit 174.

which has a variable gain K _m . which is specified via a signal line 97 <i. The output signal of the multiplier circuit 174 is output to a differentiation circuit 180 via a signal line. The output signal of the differentiating circuit is applied via a line 182 to a summing point 184, where it is combined with the integral and proportional control signals from the summing point 150, which appear on a line 186. The initial

The signal of the summing point 184 is the rotor speed control blade pitch angle reference signal β _N on the line 100.

In some cases the D-circuits 134 and 180 of FIG. 6 are not required and can be omitted or the respective gains K _n on line 97a and Κ _ΝΟ on line 97d can be reduced to zero. The need for pre-compensation depends on the type of operating variable being sensed.

The torque specification device 92 (FIG. 3) is used to minimize rotor shaft torque changes and rotor blade stresses due to gusts of wind and turbulence when the synchronous generator 26 is connected to an electrical network. The torque Q at the shaft connecting the wind turbine to the synchronous generator 26 is measured as the main control variable. The actual shaft torque signal Q appears on the signal line 64 and the desired operating torque signal Q REF appears on the signal line 68. The torque setting device 92 is similar to the rotor speed setting device 88 in that the actual torque Q is compared with the setpoint torque Q REF and that the resulting difference or error signal is used to influence the rotor blade angle via a PID controller, so that a stable, fast-responding control loop is available, which minimizes changes in torque. The correct selection of the control gains in connection with a fast acting angle of attack control device ensures a damping of the torsional resonance, which results from the inertia of the wind turbine and the spring constant of the shaft. The control gains are also selected so that torque deviations due to gusts of wind are minimized. Damping the torsional resonance of the wind turbine rotor helps. Reduce blade stresses, gear loads, and shaft torques, and allows a faster responsive torque control loop to be used. The output of the torque specification device 92 is the torque control blade pitch _{reference signal / J 0} which appears on line 108. The blade pitch angle reference _{signal β R} is fed back via line 128, and the gain is specified via line 97.

The torque setting device 92 generates the torque control sheet adjustment angle reference signal βQ on the line 108 only when the synchronous generator 26 is connected, ie only when the output frequency and the phase of the synchronous generator match those of the power supply network within the limits set by the synchronizing circuit 30 of FIG are in sync. Simultaneously with the connection of the synchronous generator 26, the rotor speed setting device 88 is converted into a speed peak or overspeed control device. When the generator 26 is switched on, namely the wind turbine with respect to the target rotor speed. N _R REF plus AN _R REF, always have underspeed and the rotor speed control blade pitch angle reference signal β _N on line 100 will require a lower blade pitch angle so that the rotor speed is increased. The torque setting device 92 limits the blade pitch angle in accordance with the system torque limits and will, in most circumstances, require a higher blade pitch angle closer to vane position. Since the maximum value selection circuit 98 of Fig. 3 passes the highest blade pitch signal, the torque control blade pitch reference signal β _{Q will be the} one that is passed, and the rotor speed setting device 88 is only effective in emergency situations when the rotor reaches upper speed, at which time the rotor speed control blade pitch reference signal β _N is the signal will be that requires the higher blade angle.

Fig. 8 shows the details of the torque setting device 92 of Fig. 3. The signal Q is the measured torque on the line 64 and the target torque signal Q REF on line 68 is compared in a summing junction 188 and it will generate a torque error signal on a signal line 190 . The proportional control takes place via a multiplier circuit 192, which has a variable gain K _QP , which is specified via a line 97e. The integral control is carried out by a multiplier circuit 196 which has a variable gain Kq , which is specified via a line 97 /. The output signal of the multiplication circuit 196 is applied via a line 198 to a summing point 200, the output signal of which is applied to an integrator 204 via a line 202. The integrator output is then applied via line 206 to summing point 208 where it is added to the output of multiplier 192 on line 210. As in the rotor speed setting device (FIG. 6), the integrator tracking takes place through the reference blade angle of attack β _R on the line 128, which is compared with the integrator output signal at a summing point 212. The difference signal is applied to summing point 200 via a line 214 and an amplification circuit 216 as well as a line 218. Boost circuit 216 has a dead zone shown in FIG.

so that the integrator 204 is only tracked when its output signal deviates considerably from the reference blade angle of attack β _R.

The differential control is carried out by a multiplier circuit 220 which has a variable gain Kq ₀ which is specified via a line 97g. The output of the multiplier circuit 220 is applied to a differentiating circuit 226 via a signal line 224, and the output of the differentiating circuit 226 is applied to a summing point 230 via a line 228, where it is combined with the PI output of the summing point 208 on a signal line 232.

The output of summing point 230 on line 108, which is the PID torque control blade pitch reference signal β _Q , passes through switch 234. Switch 234 is closed only to allow blade pitch reference signal / 3 _y to pass when the Synchronous generator 26 is connected and a discrete signal is generated on line 38 by synchronizing circuit 30 (FIG. 3). The signal on line 38 closes switch 40 (FIG. 2), connects synchronous generator 26 to the power supply network and simultaneously closes switches 144 (FIG. 6) and

234 (Fig. 8), whereby the rotor speed setting device 88 is converted into an overspeed control device becomes as described above. and thereby also the torque setting device 92 in FIG

the system is turned on. When the synchronous generator 26 is disconnected from the mains for any reason or if the frequency and / or the "base of the synchronous generator differs from that of the power supply network, the discrete Signal on line 38 is switched off, switches 40, 144 and 234 are opened and the wind turbine turns back to the rotor speed control.

When the generator 26 is connected to the mains and thus the blade pitch angle is under control the torque specification device 92 is, the generator speed and thus the output frequency kept reasonably constant by the power supply network. After switching on, the power supply network holds the speed of the synchronous generator 26 at the line frequency and in phase with the same. One Lower rotor shaft stiffness is the spring constant of the wind turbine with the synchronous generator 26 reducing the connecting shaft and helping to reduce the torsional torque to reduce.

In addition, the wind anticipation setting device 90 of FIG. 3, which is shown in detail in FIG. 7, provides further support in reducing shaft torque deviations when the generator 26 is switched on and in reducing speed deviations when the generator is disconnected from the mains. The wind anticipation setting device 90 generates a signal β _ANT on the line 104 for rapidly changing wind conditions over a nominal profile of the blade angle of attack, block 236, as a function of the wind speed V _WA , which appears as an input signal to the block 236 on the line 84, and through a differentiating transition anticipation circuit in 31ock 237. The wind anticipation schedule in block 2-6 is obtained by calculating the blade pitch required to produce constant output for different wind speeds, assuming that the generator speed is constant the desired reference value. Two wind anticipation plans can be used, one of which is set up for 100% power when the torque control is used with the generator 26 connected to the mains, and the second of which is set up for = 0% power when the generator is not connected. In any event, the β _ANT signal on line 104 is only non-zero during rapidly changing wind conditions. The signal is added to the rotor speed control blade angle reference signal β _N at the summing point 102 and also to the torque control blade pitch angle reference signal β _Q at the summing point 110. If the wind speed changes, the anticipatory signal β _ANT indicates a change in the blade angle, the temporary deviations in the rotor speed or minimized in torque, which would result from gusts of wind. However, strong gusts of wind will generally change the torque or speed sufficiently and cause the generator 26 to be disconnected from the mains until the correct frequency and phase are restored.

Instead, shaft torque changes can also be achieved through a conventional slip clutch between the wind turbine and the synchronous generator can be reduced.

The use of a PID control, which is combined in an integrator with quadratic lead compensation is, both in the rotor speed setting device 88 and in the torque setting device 92 considerably improves the stability and responsiveness of the control loops.

The delay presetting device 94 of FIG. 3 is shown in the form of a diagram in FIG. 5. In the event that the wind turbine needs to be shut down quickly, it is important to limit the rate at which the blade pitch is brought into the finned position in order to minimize the stresses placed on the blades when the wind turbine is slowed down. This limit is created here by providing a maximum blade pitch limit value which is specified as a function of the mean wind speed V _WA and the rotor speed N _R. The specification is shown for a typical wind turbine in FIG. 5, in which the delay control blade angle reference signal β _{B is} plotted against the wind speed V _WA for selected rotor speeds N _R. The plan of FIG. 5 is in Pi o_ "\ ΐΐηηΐί» ηΊί »ηΗί * τ + Here, EiH ⁰ Sn ⁰ SSi ¹⁷ HsIs are the mean wind speed V _WA on line 84 and the rotor speed N _R on line 56 of the delay setting device 94 which is an analog or digital generator for a bivariate function that generates an output signal β _D on line 120, which in turn is applied as an input signal to minimum value selection circuit 122. During normal operation of the wind turbine, the delay setting device generates 94 a blade pitch angle reference signal β _D , which requires a blade pitch angle which is greater than that specified by the rotor speed setting device 88 or by the torque setting device 92. The signal that is passed by the smallest value selection circuit 122 will therefore be that which appears on the input line 118 and requires the smallest blade angle of attack If the value is below that value? .bsink., which is required to generate the nominal power or nominal speed, the signal on the line 118 will require an even smaller blade angle of attack.

The delay presetting device 94 will only have control over the blade pitch angle if the wind turbine is to be switched off. ie when the switch 76 in the flag position signal line 74 is closed. By closing switch 76, a flag position signal appears on line 74 and is applied to summing point 116, the flag position signal being of such magnitude. that a signal is generated on line 118 which requires a very large blade angle, regardless of the signal on line 114, the other input to summing point 116. At this time, the signal on line 120 will always be a smaller blade angle than the signal on line 118, and the minimum value selector circuit 122 will pass the retarder blade _pitch reference signal β D on line 120. The wind turbine is therefore decelerated and stopped according to the schedule of Fig. 5 which limits the negative torque generated by the rotor to a value approximately equal to twice the normal positive torque rating.

It is clear that, as in the case of the acceleration setting device 86, the generator speed N _(; instead of the rotor speed _{N H} in the case of the deceleration setting device 94 can be used.

The flag position switch 76 is shown as a manual switch that actually functions as an on / off switch works because by opening the switch the flag position signal is switched off and causes the Wind turbine accelerates. The flag position switch 76 can be closed automatically when in the Wind turbine a safety circuit is provided, for example with overspeed, overcurrent or Overtemperature sensors, and if this circuit is connected to switch 76 and its closure causes when an unsafe operating condition is sensed. Other mechanical devices, such as a Shaft brake can also be provided in a known manner.

Because of the non-linear aerodynamic performance of the wind turbine, it is desirable to change the control gains in the closed control loops as a function of operating conditions in order to optimize the stability and the transient response. The preferred implementation is shown in FIG. 9, in which the signal V _{WA of} the mean wind speed is fed to the line 84 (FIG. 1) of the gain setting device 95 (FIG. 3), the several analog or digital function generators 238, 240, 242 , 244, 246, 248 and 250, which in turn contain output signals on lines 97b, 97c, 97d, 91a, 97e, 97 / or. 97g, which represent the specified control gains K _NP , Km, K _ND , K _lW , K _Q p, Kq, or K _QD . The control gains are fed to the appropriate gain multiplier circuits in FIGS. 6 and 8 in order to determine the gain of the multiplier circuits as a function of the wind speed. The gain curves shown in the function generators of Fig. 9 are only given as examples, as the actual gains will depend on many factors and cannot be precisely determined without an analysis of the specific design and components of the wind turbine.

Instead of specifying the control gains as a function of the mean wind speed, as in FIG. 9, the control gains can be specified as a function of an assumed wind speed which is a function of the blade angle of attack and the shaft torque. A corresponding implementation is shown in FIG. 10, in which signals which represent the actual blade pitch angle β _A and the shaft torque Q on the lines 52 and 64 (FIG. 1), the gain setting device 95 and therein a; Analog or digital generator 252 are supplied for a bivariate function in which the shaft torque Q is varied as a function of an assumed wind speed V _ws for several rotor blade angles β _A. The output signal of the function generator 252, which represents the assumed wind speed V _ws , appears on the line 260 and is applied to the function generators 262, 264, which specify the control gains K _NP and _{Kq D} on the lines 97Z> and 97g. The other five gain function generators shown in Fig. 9 have been omitted from Fig. 10 for the sake of simplicity. The curves shown in the function generators of FIG. 10 also serve only for the purpose of illustration, but they are similar to those shown in FIG. 9.

It is also possible to use other combinations of the wind speed, the blade angle of attack and the shaft torque as well as other parameters for specifying the variable control gains. Most known control systems use constant gains in the control loops, but with the advent of inexpensive digital microcomputers it has become easy and cheap to provide variable gains in the control system. FIG. 11 shows a modification of the blade contact angle controller 46 from FIG. 13, in which the rotor speed setting device 88 has been replaced by a generator speed setting device 266 and the torque setting device 92 has been replaced by a generator power setting device 268. In the generator speed setting device 266, the actual generator speed N _G on the signal line 60 is compared with a setpoint generator speed N _G REF, which is generated in a block 269 and appears on a signal line 270, in order to generate an error signal, and PED controller with variable gains bind in the generator rotational speed setting means 266 in a similar manner as has been described mil reference to FIG. 6, contained a Generatordrehzr <ölattar "stellwinkelreferenzsignai β _V c g on a Signaiieinr to generate 272nd The overspeed control takes place in that a signal AN _C REF is added to the signal N _c REF.

which is generated in a block 273 and appears on a Leiturg 274 when the synchronous generator 26 is connected. The integrator tracking is also carried out as in FIG. 6 using the reference blade angle of attack _{signal β R} on the line 128. The input signals for the variable gains to block 266 are not shown.

The mode of operation of the generator power setting device, which is shown in block 268 in FIG. 11, resembles the torque setting device 92 of FIG. 8. The electrical output power P _{0 of} the synchronous generator 26 on line 66 in FIG ) is compared with a generator nominal power or generator power reference signal P _c REF , which in one! Block 279 is generated and appears on line 280 (or with a generator set current or generator current reference signal instead) to generate an error signal, and PID controllers, variable gains, and integrator tracking are provided similar to the control of FIG. 8, to generate a generator power (or current) blade pitch reference signal β _P on line 282. Adding the wind _{anticipation control blade pitch} reference signal β ΑΝτ to the reference signals

so ß _NG and ß _P and the use of a switch to switch the generator power setting device 268 into the system only when the generator 26 is switched on, can be described in the above. Way to be implemented.

In cases where more electrical power is required than is supplied by a single wind turbine several wind turbines can be arranged in parallel, but the relevant synchronous generators must generate the same electrical frequency and phase. Entry takes place but not by changing the magnitude of the voltages generated, as is the case with DC voltage generation, but by changing the input power of the wind turbines by specifying the rotor blade angle of attack.

The operation of the control system is primarily with reference to block diagrams and function generators or special descriptions of the structure of the

same has been described. It is clear that the control system will be built entirely in analog format where the signals appearing on the various lines are voltage levels. It is however, it should also be understood that the preferred implementation of the control system is digital, with existing ones Microprocessors and / or digital computers can be used to carry out the necessary control functions. In the digital embodiment, the conversion of the sensed parameter signals can be made from the analog format to the digital format and the reverse conversion the steep drive control signals from digital format to analog format may be required.

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Claims (14)

Patent claims: 1. Wind turbine control system with a generator (26) driven by the wind turbine, the wind turbine having a rotor with several blades (10) with an adjustable pitch angle, with a pitch angle actuator (44) for adjusting the rotor blades, with a device (54, 58, 62 ) for measuring an operating variable (N & N _G , Q) of the generator and for generating a first signal representing this and with a device (78) for measuring the wind speed and for generating a second signal OV ₄ ) indicating this, characterized by at least one default device (88, 92), which is responsive to the first and the second signal and in dependence on the same a blade pitch angle reference signal (ß _N , ße> βώ generated by means (50) for sensing the actual pitch angle of the rotor blades (10) and for bearing one this representing third signal (β _A ) and by a comparison device (126) for comparing the blade pitch reference ignals (ßR) with the third signal (ß _A ) and for generating a blade pitch angle _{error signal (ß E} ), which is applied to the pitch angle actuator (44). 2. Control system according to claim 1, characterized in that the specification device contains: a device (67, 69, 71) for generating a reference signal (AN _R REF, N _R REF, Q REF) for the operational variable, a device (131, 188 ) for comparing the first signal with the reference signal for the operating variable and for generating an operating variable error signal which is proportional to the difference therebetween, and signal treatment means (102, 110, 236, 237) for modifying the operating variable error signal as a function of the second signal (V _WA ) in order to generate the blade pitch angle reference signal (β _N , β _Q ). 3. Control system according to claim 2, characterized in that the signal handling means includes: a first multiplier circuit (146) which generates a proportional control signal as a function of the second signal (V _WA ) from the operating variable error signal, a second multiplier circuit (152) and a Integrator (162) which generate an integral control signal as a function of the second signal (V _WA ) from the operating variable error signal, a third multiplier circuit (174) and a differentiating circuit (180) which converts the operating variable error signal into a differential control signal as a function of the generate second signal (V _WA ) , and means (150,184) for combining the proportional, integral and differential control signals. 4. Control system according to claim 3, characterized in that the gain of the first, the second and the third multiplier circuit (146, 152, 174) are each variable as a function of the second signal (V _WA ) (Fig. 9). 5. Control system according to claim 4, characterized by means (134) for generating a rate of change signal indicating the rate of change of the first signal by a fourth multiplying circuit (138) for modifying the rate of change signal in dependence on the second signal (V _WA ) and by means (130) for combining the modified rate of change signal with the operating variable error signal. 6. Control system according to one of claims 3 to 5, characterized by a device (166) for comparing the integral control signal with the blade pitch angle reference signal (ß _R ) to generate an IntegTElfehlersignal therefrom, by a tracking device (170) with a dead zone, which Receives the integral error signal and attenuates it if the integral error signal is outside a preselected range determined by the dead zone, and passes the integral error signal without attenuation if it is within the preselected range, and by a device (158) which the output signal of the tracking device (170 ) and adding the input signal of the integrator (162), thereby to keep the integral control signal within a certain relationship to the blade angle reference signal (β _R ) which is determined by the dead zone. 7 Control system according to claim 6, characterized by an acceleration setting device (86) which generates a minimum blade pitch angle frequency signal (ß _s relative to the blade pitch angle at which the blades (10) are set to full power for the acceleration phase of the roptor. 8. Control system according to claim 6 or 7, characterized by a delay setting device (94) which generates a maximum blade pitch reference signal (ß _D ) relative to the blade pitch at which the blades (10) are set to full power for the delay phase of the rotor. 9. Control system according to claim 7, characterized by a signal selection device (98, 122). which receives the blade pitch reference signals and selects one of the blade pitch reference signals, wherein the comparing means (126) the selected blade pitch roll. compares fcrenzsignal (ß _R ) with the third signal (ß _A ) in order to generate the blade pitch error signal (ß _E ). 10. Control system according to claim 9, characterized in that the signal selection device (98,122) contains a maximum value selection circuit (98) which receives the blade pitch angle reference signal (ß _N , ß _Q ) and the minimum blade pitch angle reference signal (ß _s ) and lets through that reference signal which has the greatest blade pitch angle specifies. 11. Control system according to claim 10, characterized in that the signal selection device (98, 122) contains a minimum value selection circuit (122) which receives the blade pitch angle reference signal and the maximum blade pitch angle reference signal (ß _D ) passed by the largest selection circuit (98) and passes that reference signal _{(ß R} ) , which determines the smallest blade angle. 12. Control system according to one of claims 1 to 11, characterized by a »wind anticipation preset device (90) which responds to changes in the wind speed and, as a function thereof, _{generates an anticipatory leaf pitch angle reference signal} {β ΑΝΊ) which is an adding device (102, 110) to the blade pitch angle reference signal ( ß _N , ß _Q ) added. 13. Control system according to claim 12, characterized in that the device (90) for Generate the anticipatory sheet pitch reference renzsignals 03 _AÄrr ) contains a device (236) which responds to the wind speed and specifies a target blade pitch angle anticipation signal, and a differentiating device (237) which receives the target blade pitch angle anticipation signal and therefrom generates the anticipatory blade pitch angle reference signal {βΑπτ) as a function of its rate of change. 14. Control system according to one of claims 1 to 14, wherein the generator is a synchronous generator connected to a power supply network, characterized by two setting devices (88,92) which are based on a first or second operating variable (Nr, Q) and on the responding to the wind speed indicating second signal and a first and second blade pitch angle reference signal (ß _N , ßo) , and by a further signal selection device (234) which receives both blade pitch angle reference signals and selects the first blade pitch angle reference signal when the synchronous generator (26) is not connected to the network is synchronized, and the second BlattansieUwinkelreferenz-sigtial when the synchronous generator (26) with the Ne · is synchronous. *, wherein the comparison means (126) compares the selected Blattanstellwinkelreferenzsignal with the third signal (Q _A), ß to the Blattanstellwinkelfehlersignal _(e ) to generate.