Wind turbine yaw system with a variable frequency drive and an electronic switch
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-04-26
- Publication Date
- 2026-03-04
Smart Images
Figure EP2024061535_31102024_PF_FP_ABST
Abstract
Description
[0001] WIND TURBINE YAW SYSTEM WITH A VARIABLE FREQUENCY DRIVE AND AN ELECTRONIC SWITCH
[0002] TECHNICAL FIELD
[0003] The invention relates to a yaw system for a wind turbine and, in particular, to a yaw system having a variable frequency drive for driving electrical motors to drive rotation of a nacelle of the wind turbine relative to a tower of the wind turbine, and an electronic switch for receiving a plurality of sensor signals indicative of the operation of the electrical motors and for selecting one of the sensor signals to provide to the variable frequency drive.
[0004] BACKGROUND
[0005] Wind turbines as known in the art have a tower supporting a nacelle and a rotor with a plurality of rotor blades. It is known to provide a wind turbine with a yaw system that can control the nacelle to rotate relative to the tower. Generally, yaw control is implemented to keep a rotor plane defined by the rotor and rotor blades perpendicular to an incoming wind direction, in order to maximise energy capture.
[0006] In known arrangements, a plurality of electrical motors are provided to drive rotation of the nacelle relative to the tower. In addition, a plurality of variable frequency drives (VFDs) are provided to drive rotation of the electrical motors. For instance, one VFD per electrical motor may be provided, i.e. each motor has a dedicated VFD. In such an arrangement, each VFD may receive a sensor signal indicative of a rotational speed or other operational parameter of the electrical motor that the respective VFD controls. The VFD uses this sensor signal to adjust the output frequency to control the electrical motor in accordance with a desired rotational speed or torque, as part of a feedback control loop.
[0007] In order to provide more compact yaw system arrangements, it may be desired to provide fewer VFDs than the number of electrical motors in the yaw system, such that each VFD drives a plurality of the electrical motors. The most compact solution in this regard is to provide a yaw system with a single VFD driving each of the electric motors of the yaw system.
[0008] An issue can arise in relation to operation of arrangements in which each VFD drives a plurality of the electrical motors. This is because each VFD may be capable of receiving only a single sensor signal. Hence, when multiple electrical motors are to be controlled by a VFD, said VFD cannot receive sensor signals, e.g. a rotational speed signal, from all of the electrical motors to be controlled.
[0009] It is against this background to which the present invention is set.
[0010] SUMMARY OF THE INVENTION
[0011] According to an aspect of the invention there is provided a yaw system for a wind turbine including a tower and a nacelle atop the tower. The yaw system comprises a yaw ring configured to allow rotation of the nacelle relative to the tower, and a plurality of electrical motors configured to drive rotation of the nacelle relative to the tower. The yaw system comprises a variable frequency drive configured to drive the plurality of electrical motors. The yaw system comprises a plurality of sensors, wherein each of the sensors is associated with a respective one of the electrical motors, and wherein each of the sensors is configured to measure an operational parameter of the respective electrical motor. The yaw system comprises an electronic switch configured to receive a sensor signal from each of the plurality of sensors, the sensor signal being indicative of the measured operational parameter of the respective electrical motor. The electronic switch is controllable to select one of the plurality of sensor signals to be received by the variable frequency drive. The variable frequency drive is configured to drive the plurality of electrical motors based on the selected one of the plurality of sensor signals.
[0012] The electronic switch may be a solid state switch.
[0013] Each of the plurality of sensors may be an encoder. Alternatively, each of the plurality of sensors may be a resolver.
[0014] The measured operational parameter of each of the plurality of electrical motors may be a rotation speed or position of a shaft of the respective electrical motor.
[0015] According to an aspect of the invention there is provided a control system comprising a yaw system as defined above. The control system may comprise a controller configured to control the variable frequency drive to drive the plurality of electrical motors and to control the electronic switch to select the one of the plurality of sensor signals to be received by the variable frequency drive. The controller may be configured to control the variable frequency drive to adjust a frequency of an input electrical power source to the variable frequency drive based on the selected one of the plurality of sensor signals in order to control the plurality of electrical motors to be driven at a desired shaft rotation speed as part of a closed feedback loop.
[0016] The controller may be configured to detect that the sensor from which the selected one of the plurality of sensor signals is received has a fault. The controller may be configured to, upon the detection, send a control signal to control the electronic switch to select a different one of the plurality of sensor signals to be received by the variable frequency drive. The variable frequency drive may be configured to drive the plurality of electrical motors based on the selected different one of the plurality of sensor signals.
[0017] The controller may be configured to determine that the sensor has a fault if the selected one of the plurality of sensor signals ceases to be received by the electronic switch.
[0018] The selected one of the sensor signals may be received from a first sensor of the plurality of sensors. The controller may be configured to perform a maintenance check of the first sensor based on the selected one of the sensor signals. The controller may be configured to: (i) control the electronic switch to select a different one of the sensor signals received from a different sensor of the plurality of sensors to be received by the variable frequency drive; and, (ii) perform a maintenance check of the further sensor based on the selected different one of the sensor signals. The controller may be configured to repeat steps (i) and (ii) for different sensors of the plurality of sensors until a maintenance check of each of the plurality of sensors has been performed.
[0019] The yaw system may comprise an electrical circuit breaker controllable to selectively provide an electrical connection between an input electrical power source and the plurality of electrical motors. The electrical circuit breaker may be arranged in parallel with the variable frequency drive. The controller may be configured to detect that the variable frequency drive cannot be controlled to drive the plurality of electrical motors. The controller may be configured to, upon the detection, send a control signal to control the electrical circuit breaker to provide the electrical connection between the input electrical power source and the plurality of electrical motors. According to another aspect of the invention there is provided a wind turbine comprising a yaw system as defined above. According to another aspect of the invention there is provided a wind turbine comprising a control system as defined above.
[0020] According to another aspect of the invention there is provided a method of controlling a yaw system for a wind turbine including a tower and a nacelle atop the tower. The yaw system comprises a plurality of electrical motors for driving rotation of the nacelle relative to the tower, and a variable frequency drive that is for driving the electrical motors. The method comprises, for each of the plurality of electrical motors, measuring an operational parameter of the respective electrical motor using a respective sensor. The method comprises receiving, at an electronic switch of the yaw system, a sensor signal from each of the plurality of sensors indicative of the measured operational parameter of the respective electrical motor. The method comprises selecting, at the electronic switch, one of the plurality of sensor signals received from the sensors, and communicating the selected sensor signal to the variable frequency drive. The method comprises controlling the variable frequency drive to drive the plurality of electrical motors based on the selected sensor signal received via the electronic switch.
[0021] The method may comprise detecting that the sensor from which the selected sensor signal is received has a fault. The method may comprise, upon the detection, selecting, at the electronic switch, a different one of the plurality of sensor signals received from the sensors, and communicating the selected different sensor signal to the variable frequency drive. The method may comprise controlling the variable frequency drive to drive the plurality of electrical motors based on the selected different sensor signal received via the electronic switch.
[0022] The selected one of the sensor signals may be received from a first sensor of the plurality of sensors. The method may comprise performing a maintenance check of the first sensor based on the selected one of the sensor signals. The method may comprise: (i) controlling the electronic switch to select a different one of the sensor signals received from a different sensor of the plurality of sensors to be received by the variable frequency drive; and (ii) performing a maintenance check of the further sensor based on the selected different one of the sensor signals. The method may comprise repeating steps (i) and (ii) for different sensors of the plurality of sensors until a maintenance check of each of the plurality of sensors has been performed. According to another aspect of the invention there is provided a non-transitory, computer- readable storage medium storing instructions thereon that, when executed by one or more processors, cause the one or more processors to perform the method as defined above.
[0023] BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Examples of the invention will now be described with reference to the accompanying drawings, in which:
[0025] Figure 1 is a schematic diagram of a wind turbine in accordance with an example of the invention;
[0026] Figure 2 is a schematic top view of the wind turbine of Figure 1 , indicating how a nacelle of the wind turbine may be rotated about a yaw angle based on an incoming wind direction;
[0027] Figure 3 is a schematic diagram of a yaw system of the wind turbine of Figure 1 , the yaw system being for causing rotation of the nacelle about the yaw angle indicated in Figure 2;
[0028] Figure 4 schematically illustrates elements of the yaw system of Figure 3 in accordance with an example, the yaw system including a plurality of electrical motors and a dedicated variable frequency drive for each respective electrical motor;
[0029] Figure 5 schematically illustrates elements of the yaw system of Figure 3 in accordance with a different example, the yaw system including a plurality of electrical motors and a single variable frequency drive for driving each of the electrical motors;
[0030] Figure 6 schematically illustrates elements of the yaw system of Figure 3 in accordance with a different example, the yaw system including a plurality of electrical motors and a plurality of variable frequency drives each for driving a plurality of the electrical motors;
[0031] Figure 7 schematically illustrates the plurality of electrical motors and single variable frequency drive of Figure 5, a plurality of sensors each associated with a respective one of the electrical motors, and an electronic switch between the sensors and the variable frequency drive; and, Figure 8 schematically illustrates the plurality of electrical motors and single variable frequency drive of Figure 5, and an electrical circuit breaker arranged in parallel with the variable frequency drive.
[0032] DETAILED DESCRIPTION
[0033] Figure 1 illustrates, in a schematic view, an example of a wind turbine 10. The wind turbine 10 includes a tower 102, a nacelle 103 disposed at the apex of, or atop, the tower 102, and a rotor 104 operatively coupled to a generator housed inside the nacelle 103. In addition to the generator, the nacelle 103 houses other components required for converting wind energy into electrical energy and various components needed to operate, control, and optimise the performance of the wind turbine 10. The rotor 104 of the wind turbine 10 includes a central hub 105 and three rotor blades 106 that project outwardly from the central hub 105.
[0034] The rotor 104 and rotor blades 106 rotate about a rotor axis and define a rotor plane. In particular, wind impinging on the rotor blades 106 drives rotation of the rotor 104 and rotor blades 106, thereby capturing wind energy that can be converted to electrical energy, e.g. for supply to the grid.
[0035] The wind turbine 10 includes a yaw system (not shown in Figure 1) for rotation of the nacelle 103 (including the rotor 104 and rotor blades 106) relative to the tower 102 about a defined yaw axis of the wind turbine 10. This is illustrated schematically in Figure 2, which is a top view of the wind turbine 10. In particular, Figure 2 schematically illustrates that the nacelle 103 may be rotated about a yaw angle 201 - along with the rotor 104 and rotor blades 106 - relative to the tower 102 (not shown in Figure 2).
[0036] Typically, a yaw system is operated to drive rotation, or maintain the position, of the nacelle 103 such that the rotor axis 202 is aligned with the incoming wind direction 203 or, equivalently, that the rotor plane 204 is perpendicular to the incoming wind direction 203. In general, such operation allows for the energy captured by the wind turbine 10 from the wind passing the wind turbine 10 to be maximised. This may be referred to as upwind control. As the wind direction 203 changes, based on an input from a wind direction sensor, the yaw system causes rotation of the nacelle 103 about the yaw axis as appropriate. Figure 3 illustrates a side view of an example of components of a yaw system 30 of the wind turbine 10. The yaw system 30 includes a yaw ring 301. In the described example, the yaw ring 301 is fixed to the top of the tower 102; however, in different examples the yaw ring may instead be fixed to the nacelle 103, adjacent to the tower top.
[0037] The yaw system 30 includes a plurality of electrical motors or yaw motors 302, one of which is illustrated in Figure 3. In the described example, the electrical motors 302 are fixed to the nacelle 103 (adjacent to the tower top); however, in different examples the electrical motors may instead be fixed to the tower top. Each electrical motor 302 includes an electrical brake and is connected to a respective yaw gear 303. When the electrical motors 302 are driven, the respective yaw gears 303 are driven and engage the yaw ring 301 to cause rotation of the nacelle 103 relative to the tower 102. In this regard, bearings 304 are provided between the tower top and nacelle 103 to allow I permit relative rotation therebetween.
[0038] Electrical motors may be driven in different ways. In examples of the present invention, the yaw system 30 is provided with one or more variable frequency drives (VFDs) for driving the electrical motors. A VFD is a type of alternating current (AC) motor drive that controls speed and torque of an electrical motor by varying the frequency of an input electrical power source. A VFD may have an AC and DC (direct current) supply. The use of VFDs allows for flexibility in the control of electrical motors. For instance, the use of VFDs allows torque / power / speed to be ramped up / down gradually, thereby increasing the ability of the wind turbine to handle certain loading cases. The use of VFDs can be particularly beneficial in larger wind turbines.
[0039] Figure 4 schematically illustrates a top view of components of an example yaw system 30. The plurality of electrical motors 302 are disposed around, and adjacent to, a perimeter of the yaw ring 301. In the illustrated example, the yaw system 30 includes 18 electrical motors 302; however, it will be understood that any suitable number of electrical motors may be provided, e.g. depending on the size of the wind turbine, for instance. The number of motors may typically be between 6 and 20 motors. The electrical motors may be synchronous motors or asynchronous, for instance.
[0040] In the example illustrated in Figure 4, the yaw system 30 includes a plurality of VFDs 41. In particular, in the illustrated example each of the plurality of electrical motors 302 is controlled / driven by a dedicated VFD 41. That is, in the illustrated example an equal number of VFDs 41 and electrical motors 302 are provided, i.e. 18 in this example. Each of the VFDs 41 is communicatively connected to a respective one of the electrical motors 302, i.e. each VFD 41 is electrically connected to the respective electrical motor 302, via a connection 42. Note that only some of the connections 42 are shown in Figure 4. An arrangement in which a dedicated VFD is provided to control each electrical motor may be regarded as being relatively simple to implement.
[0041] Each VFD 41 is communicatively connected (electrically connected) to an input electrical power source (not shown in Figure 4). When the VFDs 41 are provided with electrical power from the input electrical power source, the VFDs 41 are configured to control, e.g. drive, the respective electrical motors 302 to rotate at a desired rotation speed or with a desired torque. In this way, the electrical motors 302 are controlled to rotate the nacelle 103 relative to the tower 102 about a yaw angle, or maintain a yaw position of the nacelle 103 relative to the tower 102, via engagement with the yaw ring 301 .
[0042] Although not shown in Figure 4, the yaw system 30 further includes a plurality of sensors each associated with a respective one of the electrical motors 302. The yaw system 30 further includes an electronic switch, positioned between the VFDs 41 and the sensors in an electrical circuit, and for receiving sensor signals from each of the sensors. This will be discussed in greater detail below.
[0043] The wind turbine 10 includes a (high level) wind turbine controller that is for controlling different control systems of the wind turbine 10, e.g. pitch control system, generator speed control system, etc. In the described example, the wind turbine controller is configured to control the yaw system 30. In particular, the wind turbine controller may request or demand that the yaw system performs yawing to achieve a specific yaw angle of the nacelle 103, e.g. to maximise power production. The yaw system 30 may include a yaw controller 305 (illustrated schematically in Figure 2) for implementing the request from the wind turbine controller. In particular, the yaw controller 305 may determine one or more operational parameters in the form of set points for speed, torque, power, etc. The yaw system 30 may further include one or more VFD controllers (not shown) each associated with one or more respective VFDs 41. The VFD controller(s) may use the set points of the yaw controller 305 to power the VFDs 41 , e.g. by controlling voltage or current, to control components of the yaw system 30 to rotate in a clockwise direction, to rotate in an anticlockwise direction, to stop rotating, to apply mechanical braking, or to apply torque, so as to control movement of the nacelle 103 about the yaw axis as required for upwind control. The yaw controller 305 may be in the form of any suitable computing device, for instance one or more functional units or modules implemented on one or more computer processors. Such functional units may be provided by suitable software running on any suitable computing substrate using conventional or custom processors and memory. The one or more functional units may use a common computing substrate (for example, they may run on the same server) or separate substrates, or one or both may themselves be distributed between multiple computing devices. A computer memory may store instructions for performing the methods performed by the controller, e.g. controlling the yaw system in a desired manner, and the processor(s) may execute the stored instructions to perform the methods.
[0044] Figure 5 schematically illustrates a top view of components of the yaw system 30 in accordance with another example. The yaw system 30 includes the plurality of electrical motors 302 (specifically, 18 motors) disposed around the perimeter of, and adjacent to, the yaw ring 301. Unlike in the Figure 4 example, however, in the Figure 5 example the yaw system 30 includes only a single VFD 51 . The single VFD 51 is electrically connected to each of the plurality of electrical motors 302, via connections 52. Note that not all of the connections 52 are shown in Figure 5. The VFD 51 is communicatively connected (electrically connected) to an input electrical power source (not shown in Figure 5). When the VFD 51 is provided with electrical power from the input electrical power source, the VFD 51 is configured to control, e.g. drive, the respective electrical motors 302 to rotate at a desired rotation speed or with a desired torque. An arrangement in which a single VFD is provided to control each of the electrical motors may be regarded as being a relative cost effective and compact solution. While the single VFD 51 may be larger than one of the dedicated VFDs 41 , there is still a significant space saving by virtue of only having a single VFD unit.
[0045] Although not shown in Figure 5, the yaw system 30 further includes a plurality of sensors each associated with a respective one of the electrical motors 302. The yaw system 30 further includes an electronic switch, positioned between the VFD 51 and the sensors in an electrical circuit, and for receiving sensor signals from each of the sensors. This will be discussed in greater detail below.
[0046] Figure 6 schematically illustrates a top view of components of the yaw system 30 in accordance with another example. The yaw system 30 includes the plurality of electrical motors 302 (specifically, 18 motors) disposed around the perimeter of, and adjacent to, the yaw ring 301. In the Figure 6 example the yaw system 30 includes a plurality of VFDs 61. However, unlike the Figure 4 example, in the Figure 6 example each of the VFDs 61 is electrically connected to a plurality of electrical motors 302, via connections 62. Note that not all of the connections 62 are shown in Figure 6. There are fewer VFDs 61 than electrical motors 302. In the illustrated example, there are 4 VFDs 61 (and 18 electrical motors 302). Each VFD 61 is communicatively connected (electrically connected) to an input electrical power source (not shown in Figure 6).
[0047] As mentioned above, each VFD is used to control rotation of the electrical motors. In particular, a VFD may receive a sensor signal indicative of a rotational speed or other operational parameter of an electrical motor that the VFD controls. The VFD may then use this sensor signal to adjust the output frequency to control the electrical motor in accordance with a desired rotational speed or torque, as part of a feedback control loop.
[0048] An issue may arise in relation to operation of arrangements in which each VFD drives a plurality of the electrical motors, e.g. the arrangement illustrated in Figure 5. This is because each VFD may be capable of receiving only a single sensor signal. Hence, when multiple electrical motors are to be controlled by a VFD, said VFD cannot receive sensor signals, e.g. a rotational speed signal, from all of the electrical motors to be controlled.
[0049] The invention is therefore beneficial in that it provides an arrangement that allows for a VFD to control rotational speed or torque of an electrical motor in accordance with a desired rotation speed or torque in a wind turbine yaw system in which the VFD controls rotation speed or torque of a plurality of electrical motors. The arrangement of the invention is also beneficial in that it provides increased redundancy relative to previous arrangements and allows for monitoring operation of components of the arrangement as part of a maintenance routine. The means by which these benefits are achieved are described below.
[0050] Figure 7 schematically illustrates components of the yaw system 30 in an example in which each VFD of the yaw system drives a plurality of electrical motors, where the yaw system includes one or more VFDs. The example illustrated in Figure 7 specifically relates to the yaw system 30 illustrated in Figure 5 in which the yaw system 30 includes the single VFD 51 electrically connected to, and for driving, each of the plurality of electrical motors 302 (only 4 of the motors 302 are shown in Figure 7). Figure 7 illustrates that the yaw system 30 further includes a plurality of sensors 71. Each of the sensors 71 is associated with a respective one of the electrical motors 302. Each sensor 71 is configured to measure an operational parameter associated with operation of the respective electrical motor 302. Each of the sensors 71 may be an encoder or a resolver. The operational parameter to be measured using the sensors 71 may be a rotation speed of the respective motor 302, a position of the shaft of the respective motor 302, and / or a rotation direction of the shaft of the respective motor 302.
[0051] Figure 7 illustrates that the yaw system 30 further includes an electronic switch 72. The switch 72 is positioned between the VFD 51 and the sensors 71 in an electrical circuit. The switch 72 is configured to receive a sensor signal 73 from each of the plurality of sensors 71. Each sensor signal 73 is indicative of the measured operational parameter, e.g. shaft rotation speed, of the respective electrical motor 302.
[0052] The specific VFD 51 being used is capable of receiving only a single sensor signal. The electronic switch 72 is beneficially controllable to select one of the plurality of sensor signals 73 received from the sensors 71 to be received by the VFD 51. The electronic switch 72 is configured to direct I send the selected sensor signal 73 to the VFD 51 as the selected signal 74. The VFD 51 is configured to control I drive the plurality of electrical motors 302 based on the selected one 74 of the plurality of sensor signals 73.
[0053] The yaw controller 305 may be used to control the VFD 51 to drive I control the electrical motors 302. In particular, the yaw controller 305 or VFD controller may be configured to control the VFD 51 to adjust a frequency of an input electrical power source 65 to the VFD 51 based on the selected sensor signal 74 in order to control each of the electrical motors 302 to be driven at a desired shaft rotation speed as part of a closed feedback loop. The yaw controller 305 may also be used to control the electronic switch 72 to select which received sensor signal 73 is to be provided to the VFD 51 . The controller 205 and the yaw system 30 may collectively be referred to as a control system of the wind turbine 10. In alternative examples, the VFD and / or electronic switch may act as a controller to control operation of themselves and / or one another. For instance, the electronic switch may be configured to monitor received sensor signals and determine I select which sensor signal to provide to the VFD.
[0054] In the described example, the electronic switch is a solid state switch. Such a switch is an electronic switching device with no moving parts that switches on or off when an external voltage is applied across its control terminals. Such a switch is beneficial because it is fast and reliable at coupling and decoupling signals. It will be understood that different types of electronic switch may be used in different examples. The type of switch that is deployed may depend on the type of sensor being used to measure the electronic motor operational parameters.
[0055] During normal operation of the yaw system 30, a single signal indicative of operation of only one of the electrical motors 302 is sufficient for the VFD 51 to perform closed-loop feedback control to control each of the electrical motors 302. In one example, one of the plurality of sensors 71 may be regarded as a default sensor, with the electronic switch 72 selecting the sensor signal 73 associated with the default sensor 71 to be provided to the VFD 51 during normal operation. In another example, the electronic switch 72 may be controlled to switch between the different received sensor signals 73, e.g. in a cyclical or periodic manner, such that the VFD receives the sensor signal from different ones of the electrical motors at different times.
[0056] The yaw system 30 including the electronic switch 72 is beneficial in that it introduces a degree of redundancy into the system. In particular, if the electrical motor 302 or sensor 71 associated with the sensor signal 73 selected by the electronic switch 72 to be provided to the VFD 51 fails or has a fault, then the electronic switch 72 can select a different one of the sensor signals 73 - associated with an electrical motor 302 and sensor 71 that are operating correctly - to be provided to the VFD 51 , to ensure continued operation of the yaw system. For instance, the yaw controller 305 may be configured to detect that one of the sensors 71 is faulty, or that an electrical motor 302 is not operating as expected, in which case the yaw controller 305 may be configured to control the electronic switch 72 to select one of the sensor signals 73 that is not associated with a faulty I failed sensor 71 or motor 302. In one example, the yaw controller 305 may be configured to determine that one of the sensors 71 has a fault if the respective signal 73 from the sensor 71 ceases to be received by the electronic switch 72, i.e. communication loss. In this way, failure of one or more electrical motors 302 or sensors 71 does not impact on operation of the VFD 51 . This increased redundancy in the yaw system may be with reference to a previous arrangement in which one VFD controls a plurality of electrical motors, but in which a sensor signal associated with one of the electrical motors is fed directly to the VFD, i.e. without an electronic switch. It is noted that if it is detected that none of the sensor signals 73 to be received by the electronic switch 72 are available, then the VFD 51 can be controlled to operate according to an open feedback loop (rather than a closed feedback loop), i.e. determining a frequency output with which to control the electrical motors 302 where the determination is not based on any of the sensor signals 73.
[0057] It is noted that a benefit of an arrangement in which each electrical motor has a dedicated VFD - such as the example illustrated in Figure 4 - is that operation of each electrical motor, as well as brakes and gears of the yaw system, can be monitored using the sensor signal indicative of an operational parameter of the respective electrical motor received by the respective dedicated VFD to be used for feedback control. For instance, the sensor signal can be analysed to ensure that the actual shaft rotation speed of the electrical motor is in line with the shaft rotation speed that the VFD is controlling the electrical motor to operate at.
[0058] In an arrangement in which one VFD controls a plurality of electrical motors, and the VFD performs feedback control based on a measured operational parameter signal of only one of the electrical motors - such as the arrangements illustrated in Figures 5 and 6 - then one issue is that it is more difficult to perform maintenance checks on all of the electrical motors, brakes, gears, etc., of the yaw system. A further benefit of the yaw system 30 including the electronic switch 72 described herein is that checks to ensure that all of the electrical motors and sensors are operating correctly can be performed. Similarly to above, this benefit may for instance be evident relative to a previous arrangement in which one VFD controls a plurality of electrical motors, but in which a sensor signal associated with one of the electrical motors is fed directly to the VFD, i.e. without an electronic switch.
[0059] When it is desired to perform a maintenance check, e.g. periodically, the wind turbine controller may be configured to control the electronic switch 72 to cycle through each of the plurality of received sensor signals 73 to be the selected signal 74 to send to the VFD 51 . For a first one of the received sensor signals 73 as the selected signal 74, the controller 205 may be configured to perform a maintenance check of the sensor 71 associated with the first one of the sensor signals 73. This could involve analysing the sensor signal 73 to detect any potential issues. For instance, if the signal 73 is not being received by the electronic switch 72, i.e. the sensor signal is unavailable, then this could indicate that the associated sensor 71 is faulty or that there has been a loss of communication between the sensor 71 and the switch 72. If the sensor signal 73 indicates that the measured operational parameter is outside of an expected operating range, then this could indicate a fault with the respective electrical motor 302 or a fault with the associated sensor 71. The controller 205 may be configured to repeat the process for each of the sensor signals 73 input into the electronic switch 72. If an issue is detected with one of the sensor signals 73 during the maintenance check then various suitable actions may be taken. For instance, the controller 205 may raise an alarm to an operator, indicating that maintenance or investigation is needed. That controller 205 may control the electronic switch 72 to not select the sensor signal 73 associated with the fault until the fault has been investigated and fixed. The maintenance check may alternatively be implemented or initiated by the yaw controller 305 or one or more dedicated (inner) VFD controllers, or by a combination of the wind turbine controller, the yaw controller 305 and one or more VFD controllers.
[0060] It will be appreciated that the provision of a yaw system with an electronic switch that receives a plurality of sensor signals indicative of respective operation of a plurality of electrical motors, and selects one of the received sensor signals to be provided to a VFD, may be implemented in a yaw system in which one or more VFDs each control a plurality of electrical motors. This includes the arrangement illustrated in Figure 5 - in which a single VFD controls each of the electrical motors of the yaw system - as well as arrangements such as the arrangement of Figure 6 in which a plurality of VFDs each control a plurality of electrical motors, e.g. a yaw system comprising 2 VFDs and 18 electrical motors, where each of the VFDs controls 9 of the electrical motors.
[0061] With reference to Figure 8, the yaw system 30 may optionally further include an electrical circuit breaker 83 in examples of the invention. The example illustrated in Figure 8 specifically relates to the yaw system 30 illustrated in Figure 5 in which the yaw system 30 includes the single VFD 51 electrically connected to, and for driving, each of the plurality of electrical motors 302, and including the electronic switch 72.
[0062] The circuit breaker 83 is actuatable to open or close an electrical connection between the input power source 65 and the electrical motors 302. The circuit breaker 83 is arranged in parallel with the VFD 51. That is, the VFD 51 and circuit breaker 83 are on different branches 54a, 54b of the electrical connection between the input electrical power source 65 and the electrical motors 302.
[0063] In the described example, the circuit breaker 83 is a direct online contactor (DOL). A DOL allows for the bypass branch 54b to be connected such that full line voltage is applied via the bypass branch 54b immediately, i.e. allows for starting at full load. Other types of contactor may be used. The circuit breaker may for instance be a moulded case circuit breaker in some examples. The DOL 83 allows the motors 302 to be started at full load, with full line voltage applied to motor terminals. A DOL starter may be used if the high inrush current of the starter motor does not cause excessive voltage drop in the supply circuit.
[0064] When the VFD 51 is electrically connected to the input electrical power source 65 and the electrical motors 302, such that the VFD 51 controls operation of the electrical motors 302, the circuit breaker 83 is open or disconnected. That is, in such a case electrical current does not flow via the circuit branch 54b from the input electrical power source 65 to the electrical motors 302.
[0065] When the VFD 51 cannot control operation of the electrical motors 302, the circuit breaker 83 can be actuated to close or connect such that electrical current does flow via the circuit branch 54b from the input electrical power source 65 to the electrical motors 302. The VFD 51 can then be shunted out of the electrical circuit. In this way, in the event that the VFD 51 cannot be used to control the electrical motors 302, the electrical motors 302 nonetheless remain operational by virtue of the branch 54b and the circuit breaker 83. In particular, while the provision of electrical power via the branch 54b may not allow for such a degree of control over the operation of the electrical motors 302 compared to when the VFD 51 is operational, the circuit breaker 83 is a relatively simple and cost efficient way to ensure that the electrical motors 302 remain operational at least until the issue affecting operation of the VFD 51 can be resolved. In addition to the system being provided with a controllable circuit breaker to allow electrical current to flow via the bypass branch 54b, the system is also provided with controllable electrical contacts to shunt in / out the VFD 51 from the electrical circuit as desired, as mentioned above.
[0066] The circuit breaker 83 can therefore selectively provide an electrical connection between the input electrical power source 65 and the plurality of electrical motors 302. In particular, the circuit breaker 83 can provide the electrical connection when the VFD 51 cannot be controlled to do so, e.g. as a result of a fault associated with the VFD 51 or a connection loss associated with the VFD 51.
[0067] Depending on the particular reason why the VFD 51 cannot be used to control the electrical motors 302, the VFD 51 may be disconnected from the input electrical power source 65 and / or the electrical motors 302, e.g. via controllable electrical contacts, prior to the circuit breaker 83 being closed to complete the electrical circuit. The wind turbine controller may be configured to request a specific yaw angle, e.g. to maximise wind turbine power production. The yaw controller 305 (or yaw motor controller) of the wind turbine 10 may then implement this request from the wind turbine controller. A VFD controller may further be provided to control the VFD 51. The yaw controller 305 and VFD controller may be part of the yaw system 30. In particular, the yaw controller 305 control operation of the VFD 51 , e.g. to adjust an output frequency in accordance with the desired rotation speed of the electrical motors 302. This may be directly, or via the VFD controller. In some examples, the controller 205 is configured to control actuation of the circuit breaker 83 between open and closed positions. For instance, the yaw controller 305 may be configured to detect that the VFD 51 cannot be controlled to drive the plurality of electrical motors 302. The detection may be performed in any suitable manner. For instance, the yaw controller 305 may be configured to receive a signal, e.g. a controller area network (CAN) signal, from the VFD 51 with a status update, where one such update may be that the VFD 51 has failed or is unavailable for another reason. Alternatively, the yaw controller 305 may be configured to monitor the electrical motors 302 or movement of the nacelle 103 when the yaw controller 305 sends a control signal to the VFD 51 to operate in a certain manner, e.g. to rotate the nacelle 103 in a particular direction. If there is no response by the electrical motors 302 or nacelle 103 detected by the yaw controller, then the yaw controller 305 may determine that a connection has been lost or the VFD 51 is faulty. Upon the detection that the VFD 51 cannot be controlled to drive the plurality of electrical motors 302, the controller 205 may be configured to send a control signal to control the electrical circuit breaker 83 to provide the electrical connection between the input electrical power source 65 and the plurality of electrical motors 302.
[0068] In different examples, the circuit breaker 83 may be configured to automatically close to provide the electrical connection between the input electrical power source 65 and the plurality of electrical motors 302 when the VFD 51 cannot provide such a connection. For instance, a signal, e.g. from a sensor, may be received by the circuit breaker 83 indicating that the VFD 51 is faulty or the electrical connection in the branch 54a has been lost, upon which the circuit breaker 83 is configured to automatically close to complete the circuit through the branch 54b.
[0069] It will be appreciated that the provision of a yaw system with a circuit breaker arranged in parallel with a VFD can be implemented in each of: the yaw system of Figure 4 in which each electrical motor has a dedicated VFD; the yaw system of Figure 5 in which a single VFD controls all of the electrical motors of the yaw system; and, the yaw system of Figure 6 in which a plurality of VFDs each control a plurality of electrical motors. A circuit breaker may be provided in parallel for all, or only some, of the VFDs in the yaw system. In examples in which the electronic switch 62 is provided, the circuit breaker 83 can also be provided as part of the same arrangement.
[0070] In all of these cases, the provision of the circuit breaker advantageously increases the redundancy of the yaw drive system when one or more VFDs are not operational. However, it will also be appreciated that the provision of the circuit breaker is particularly advantageous in yaw systems where fewer VFDs are provided, as the failure of one VFD in such systems has a greater impact on the operation of the yaw system. That is, the greater the number of electrical motors that a particular VFD is responsible for controlling, the greater the number of the electrical motors that may not be able to be driven in the event of VFD failure. It will furthermore be appreciated that the provision of the circuit breaker is most advantageous in the example illustrated in Figure 5 in which a single VFD controls all of the electrical motors of the yaw system. This is because if this single VFD 51 cannot be used to control the electrical motors 302, then the yaw system 30 would otherwise be inoperable without the backup circuit breaker. This can help avoid wind turbine down time, and minimise any loss in power generation.
[0071] The use of electrical circuit breakers or contactors in the described manner is a relatively cost effective and robust way to add redundancy to the wind turbine yaw system. Also, existing wind turbines can be retrofitted to include any necessary / missing components to provide an arrangement with one or more VFDs arranged in parallel with one or more circuit breakers. The retrofitting can involve including one or more VFDs into an existing arrangement, and / or including one or more circuit breakers into an existing system. The retrofitting could also involve the removal of certain components, e.g. one or more VFDs. Increasing the redundancy and reliability of a wind turbine in this way can extend the life of major, difficult-to-replace components of the wind turbine, such as the yaw ring and main shaft.
[0072] Many modifications may be made to the described examples without departing from the scope of the appended claims.
Claims
CLAIMS1. A yaw system for a wind turbine including a tower and a nacelle atop the tower, the yaw system comprising: a yaw ring configured to allow rotation of the nacelle relative to the tower; a plurality of electrical motors configured to drive rotation of the nacelle relative to the tower; a variable frequency drive configured to drive the plurality of electrical motors; a plurality of sensors, wherein each of the sensors is associated with a respective one of the electrical motors, wherein each of the sensors is configured to measure an operational parameter of the respective electrical motor; and, an electronic switch configured to receive a sensor signal from each of the plurality of sensors, the sensor signal being indicative of the measured operational parameter of the respective electrical motor, wherein the electronic switch is controllable to select one of the plurality of sensor signals to be received by the variable frequency drive, wherein the variable frequency drive is configured to drive the plurality of electrical motors based on the selected one of the plurality of sensor signals.
2. A yaw system according to Claim 1 , wherein the electronic switch is a solid state switch.
3. A yaw system according to Claim 1 or Claim 2, wherein: each of the plurality of sensors is an encoder; or, each of the plurality of sensors is a resolver.
4. A yaw system according to any previous claim, wherein the measured operational parameter of each of the plurality of electrical motors is a rotation speed or position of a shaft of the respective electrical motor.
5. A control system comprising the yaw system according to any previous claim, the control system comprising a controller configured to control the variable frequency drive to drive the plurality of electrical motors and to control the electronic switch to select the one of the plurality of sensor signals to be received by the variable frequency drive.
6. A control system according to Claim 5, wherein the controller is configured to control the variable frequency drive to adjust a frequency of an input electrical power source to the variable frequency drive based on the selected one of the plurality of sensor signals inorder to control the plurality of electrical motors to be driven at a desired shaft rotation speed as part of a closed feedback loop.
7. A control system according to Claim 5 or Claim 6, wherein the controller is configured to: detect that the sensor from which the selected one of the plurality of sensor signals is received has a fault; and, upon the detection, send a control signal to control the electronic switch to select a different one of the plurality of sensor signals to be received by the variable frequency drive, wherein the variable frequency drive is configured to drive the plurality of electrical motors based on the selected different one of the plurality of sensor signals.
8. A control system according to Claim 7, wherein the controller is configured to determine that the sensor has a fault if the selected one of the plurality of sensor signals ceases to be received by the electronic switch.
9. A control system according to any of Claims 5 to 8, wherein the selected one of the sensor signals is received from a first sensor of the plurality of sensors, wherein the controller is configured to perform a maintenance check of the first sensor based on the selected one of the sensor signals, wherein the controller is configured to:(i) control the electronic switch to select a different one of the sensor signals received from a different sensor of the plurality of sensors to be received by the variable frequency drive; and,(ii) perform a maintenance check of the further sensor based on the selected different one of the sensor signals, wherein the controller is configured to repeat steps (i) and (ii) for different sensors of the plurality of sensors until a maintenance check of each of the plurality of sensors has been performed.
10. A control system according to any of Claim 5 to 9, wherein the yaw system comprises an electrical circuit breaker controllable to selectively provide an electrical connection between an input electrical power source and the plurality of electrical motors, wherein the electrical circuit breaker is arranged in parallel with the variable frequency drive, wherein the controller is configured to: detect that the variable frequency drive cannot be controlled to drive the plurality of electrical motors; and,upon the detection, send a control signal to control the electrical circuit breaker to provide the electrical connection between the input electrical power source and the plurality of electrical motors.
11. A wind turbine comprising a yaw system according to any of Claims 1 to 4, or comprising a control system according to any of Claims 5 to 10.
12. A method of controlling a yaw system for a wind turbine including a tower and a nacelle atop the tower, the yaw system comprising: a plurality of electrical motors for driving rotation of the nacelle relative to the tower; and, a variable frequency drive that is for driving the electrical motors, the method comprising: for each of the plurality of electrical motors, measuring an operational parameter of the respective electrical motor using a respective sensor; receiving, at an electronic switch of the yaw system, a sensor signal from each of the plurality of sensors indicative of the measured operational parameter of the respective electrical motor; selecting, at the electronic switch, one of the plurality of sensor signals received from the sensors, and communicating the selected sensor signal to the variable frequency drive; and, controlling the variable frequency drive to drive the plurality of electrical motors based on the selected sensor signal received via the electronic switch.
13. A method according to Claim 12, the method comprising: detecting that the sensor from which the selected sensor signal is received has a fault; upon the detection, selecting, at the electronic switch, a different one of the plurality of sensor signals received from the sensors, and communicating the selected different sensor signal to the variable frequency drive; and, controlling the variable frequency drive to drive the plurality of electrical motors based on the selected different sensor signal received via the electronic switch.
14. A method according to Claim 12 or Claim 13, wherein the selected one of the sensor signals is received from a first sensor of the plurality of sensors, and the method comprisesperforming a maintenance check of the first sensor based on the selected one of the sensor signals, the method further comprising:(i) controlling the electronic switch to select a different one of the sensor signals received from a different sensor of the plurality of sensors to be received by the variable frequency drive;(ii) performing a maintenance check of the further sensor based on the selected different one of the sensor signals; and, repeating steps (i) and (ii) for different sensors of the plurality of sensors until a maintenance check of each of the plurality of sensors has been performed.
15. A non-transitory, computer-readable storage medium storing instructions thereon that, when executed by one or more processors, cause the one or more processors to perform the method of any of Claims 12 to 14.