Heating circuit for heating system of wind turbine and method of operation thereof

Abstract

The invention relates to a heating circuit for a heating system of a wind turbine and a method for operating the same, in particular to a method for operating a heating system of a wind turbine connected to a power grid. The method includes receiving a voltage signal from a power grid via a heating circuit of a heating system. The method also includes processing the voltage signal using a heating circuit of the heating system. Processing the voltage signal using a heating circuit of the heating system includes superimposing a pulse width modulation (PWM) signal onto the voltage signal. Further, the method includes providing continuous temperature control to at least one heating element of the heating system via the PWM signal from the heating circuit. Further, the method includes maintaining a temperature of the at least one heating element within a temperature range using the PWM signal during operation of the wind turbine to minimize temperature cycling of the at least one heating element.

Description

Technical Field

[0001] The present disclosure generally relates to wind turbines, and more particularly, to a heating circuit of a heating system for a wind turbine for mitigating ice on the wind turbine and a method of operating the same. Background Art

[0002] Generally, a wind turbine includes a turbine having a rotor, the rotor including a rotatable hub assembly having a plurality of blades. The blades convert wind energy into mechanical rotational torque, which drives one or more generators via the rotor. The generators are sometimes (but not always) rotationally coupled to the rotor via a gearbox. The gearbox increases the inherently low rotational speed of the rotor so that the generators can effectively convert rotational mechanical energy into electrical energy, which is fed into the utility grid via at least one electrical connection. There are also gearless direct drive wind turbines. The rotor, generators, gearbox, and other components are typically mounted within a housing or nacelle, which is positioned on top of a base, which can be a truss or tubular tower.

[0003] Some wind turbine configurations include a doubly-fed induction generator (DFIG). Such configurations may also include a power converter for converting the frequency of the generated electrical power into a frequency substantially similar to the utility grid frequency. Additionally, such a converter in combination with the DFIG also transfers electrical power between the utility grid and the generator, and transfers the generator excitation power from one of the connections to the utility grid connection to the wound generator rotor. Alternatively, some wind turbine configurations include, but are not limited to, alternative types of induction generators, permanent magnet (PM) synchronous generators, and electrically excited synchronous generators, as well as switched reluctance generators. These alternative configurations may also include a power converter for converting the frequency and transferring electrical power between the utility grid and the generator as described above.

[0004] With new developments in the wind industry, wind turbines are exploring new areas and striving to enter remote and extreme weather locations to harvest energy. Thus, in some cases, the rotors are more complex, and in addition to pitch control, additional systems may be required, such as an ice mitigation system that requires more power. Additionally, such systems operate at different potential and current levels, and sometimes cannot maintain a common potential due to certain limitations of the power devices or applications. Summary of the Invention

[0005] Aspects and advantages of the present invention will be set forth in part in the following description, or may be apparent from the description, or may be learned by practice of the present invention.

[0006] In one aspect, the present disclosure relates to a method of operating a heating system of a wind turbine connected to an electrical grid. The method includes receiving a voltage signal from the electrical grid via a heating circuit of the heating system; processing the voltage signal using the heating circuit of the heating system. Processing the voltage signal using the heating circuit of the heating system includes superimposing a pulse width modulation (PWM) signal onto the voltage signal. The method further includes providing continuous temperature control to at least one heating element of the heating system via the PWM signal from the heating circuit. Additionally, the method includes maintaining the temperature of the at least one heating element within a temperature range during operation of the wind turbine using the PWM signal to minimize temperature cycling of the at least one heating element.

[0007] In another aspect, the present disclosure relates to a heating system. The heating system includes at least one heating element and a heating circuit electrically coupled to the at least one heating element. The heating circuit is configured to perform a plurality of operations including, but not limited to, receiving a voltage signal from the electrical grid; processing the voltage signal, where processing the voltage signal includes superimposing a pulse width modulation (PWM) signal onto the voltage signal; providing continuous temperature control to the at least one heating element via the PWM signal; and maintaining the temperature of the at least one heating element within a temperature range using the PWM signal to minimize temperature cycling of the at least one heating element.

[0008] In yet another aspect, the present disclosure relates to a wind turbine connected to an electrical grid. The wind turbine includes a tower, a nacelle mounted on top of the tower, and a rotatable hub mounted to the nacelle. The rotatable hub has at least one rotor blade mounted thereto. The wind turbine further includes a heating system for mitigating ice on the wind turbine. The heating system includes at least one heating element and a heating circuit electrically coupled to the at least one heating element. The heating circuit is configured to perform a plurality of operations including, but not limited to, receiving a voltage signal from the electrical grid; processing the voltage signal, where processing the voltage signal includes superimposing a pulse width modulation (PWM) signal onto the voltage signal; providing continuous temperature control to the at least one heating element via the PWM signal; and maintaining the temperature of the at least one heating element within a temperature range using the PWM signal to minimize temperature cycling of the at least one heating element.

[0009] These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. Technical solution 1. A method of operating a heating system of a wind turbine connected to an electrical grid, the method comprising: Receiving a voltage signal from the electrical grid via a heating circuit of the heating system; Process the voltage signal using the heating circuit of the heating system, wherein processing the voltage signal using the heating circuit of the heating system includes superimposing a pulse width modulation (PWM) signal onto the voltage signal; Provide continuous temperature control to at least one heating element of the heating system via the PWM signal from the heating circuit; and During operation of the wind turbine, maintain the temperature of the at least one heating element within a temperature range using the PWM signal to minimize temperature cycling of the at least one heating element. Technical solution 2. The method according to technical solution 1, wherein processing the voltage signal using the heating circuit of the heating system further includes: Implement a zero crossing detection (ZCD) algorithm on the voltage signal to provide a smooth start for the temperature control. Technical solution 3. The method according to technical solution 2, wherein superimposing the PWM signal onto the voltage signal occurs after implementing the ZCD algorithm on the voltage signal. Technical solution 4. The method according to technical solution 3, wherein processing the voltage signal using the heating circuit of the heating system further includes: Implement an integral cycle control (ICC) on the PWM signal to reduce harmonics fed into the power grid. Technical solution 5. The method according to technical solution 4, wherein superimposing the PWM signal onto the voltage signal occurs before implementing the ICC on the PWM signal. Technical solution 6. The method according to technical solution 1, wherein providing the continuous temperature control to the at least one heating element of the heating system via the PWM signal from the heating circuit further includes: Gate and turn off at least one semiconductor device of the heating circuit to apply the PWM signal to the at least one heating element in order to provide power to the at least one heating element. Technical solution 7. The method according to technical solution 6, wherein the at least one semiconductor device of the heating circuit includes at least one of a thyristor, a diode, a metal oxide semiconductor field effect transistor (MOFSET), or an insulated gate bipolar transistor (IGBT). Technical solution 8. The method according to technical solution 1, the method further includes arranging the at least one heating element of the heating system on one or more rotor blades of the wind turbine. Technical solution 9. A heating system, comprising: At least one heating element; and A heating circuit electrically connected to the at least one heating element, the heating circuit configured to perform a plurality of operations, the plurality of operations including: Receiving a voltage signal from the power grid; Processing the voltage signal, wherein processing the voltage signal includes superimposing a pulse width modulation (PWM) signal onto the voltage signal; Providing continuous temperature control to the at least one heating element via the PWM signal; and Maintaining the temperature of the at least one heating element within a temperature range using the PWM signal to minimize temperature cycling of the at least one heating element. Aspect 10. The heating system according to aspect 9, wherein the heating circuit includes a zero crossing detection (ZCD) module, and wherein processing the voltage signal further includes: Implementing a ZCD algorithm on the voltage signal via the ZCD algorithm module to provide a smooth start for the temperature control. Aspect 11. The heating system according to aspect 10, wherein superimposing the PWM signal onto the voltage signal occurs after implementing the ZCD algorithm on the voltage signal via the ZCD algorithm module. Aspect 12. The heating system according to aspect 11, wherein the heating circuit includes an integral cycle control (ICC) module, and wherein processing the voltage signal further includes: Implementing ICC on the PWM signal via the ICC module to reduce harmonics fed into the power grid. Aspect 13. The heating system according to aspect 12, wherein superimposing the PWM signal onto the voltage signal occurs before implementing the ICC on the PWM signal via the ICC module. Aspect 14. The heating system according to aspect 9, wherein the heating circuit further includes at least one semiconductor device, and wherein providing continuous temperature control to the at least one heating element via the PWM signal further includes: Gating and turning off the at least one semiconductor device to apply the PWM signal to the at least one heating element to provide power to the at least one heating element. Aspect 15. The heating system according to aspect 14, wherein the at least one semiconductor device of the heating circuit includes at least one of a thyristor, a diode, a metal oxide semiconductor field effect transistor (MOFSET), or an insulated gate bipolar transistor (IGBT). Aspect 16. The heating system according to Aspect 9, wherein at least one heating element of the heating system is arranged on one or more rotor blades of a wind turbine. Aspect 17. A wind turbine connected to a power grid, the wind turbine comprising: A tower; A nacelle mounted on top of the tower; A rotatable hub mounted in the nacelle, the rotatable hub having at least one rotor blade mounted thereto; A heating system for mitigating ice on the wind turbine, comprising: At least one heating element arranged together with the at least one rotor blade; and A heating circuit electrically coupled to the at least one heating element, the heating circuit configured to perform a plurality of operations, the plurality of operations including: Receiving a voltage signal from the power grid; Processing the voltage signal, wherein processing the voltage signal includes superimposing a pulse width modulation (PWM) signal onto the voltage signal; Providing continuous temperature control to the at least one heating element via the PWM signal; and During operation of the wind turbine, maintaining the temperature of the at least one heating element within a temperature range using the PWM signal to minimize temperature cycling of the at least one heating element. Aspect 18. The wind turbine according to Aspect 17, wherein the heating circuit includes a zero crossing detection (ZCD) module and an integral cycle control (ICC) module, and wherein processing the voltage signal further includes: Implementing a ZCD algorithm on the voltage signal via the ZCD algorithm module to provide a smooth start for the temperature control; and Implementing ICC on the PWM signal via the ICC module to reduce harmonics fed into the power grid. Aspect 19. The wind turbine according to Aspect 18, wherein superimposing the PWM signal onto the voltage signal occurs after implementing the ZCD algorithm on the voltage signal via the ZCD algorithm module and before implementing ICC on the PWM signal via the ICC module. Aspect 20. The wind turbine according to Aspect 17, wherein the heating circuit further includes at least one semiconductor device, and wherein providing continuous temperature control to the at least one heating element via the PWM signal further includes: Strobe and turn off the at least one semiconductor device to apply the PWM signal to the at least one heating element so as to supply power to the at least one heating element, wherein the at least one semiconductor device of the heating circuit includes at least one of a thyristor, a diode, a metal-oxide semiconductor field effect transistor (MOFSET), or an insulated gate bipolar transistor (IGBT). BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A complete and enabling disclosure of the invention, including the best mode thereof, for one of ordinary skill in the art, is set forth in the specification, which makes reference to the accompanying drawings, in which:

[0011] Figure 1 A partial perspective view of an embodiment of a wind turbine in accordance with the present disclosure is shown;

[0012] Figure 2 A schematic view of an embodiment of an electrical and control system of a wind turbine in accordance with the present disclosure is shown;

[0013] Figure 3 A block diagram of a controller for a wind turbine in accordance with the present disclosure is shown;

[0014] Figure 4 A perspective view of an embodiment of a wind turbine is shown, which particularly shows ice mitigation and detection of a wind turbine in accordance with the present disclosure;

[0015] Figure 5 A flowchart of an embodiment of a method of operating a heating system for a wind turbine in accordance with the present disclosure is shown;

[0016] Figure 6 A schematic view of an embodiment of a heating circuit for a wind turbine in accordance with the present disclosure is shown; and

[0017] Figure 7 An example voltage signal superimposed with a PWM signal in accordance with the present disclosure is shown. DETAILED DESCRIPTION

[0018] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention and not as a limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For example, features shown or described as part of one embodiment can be used with another embodiment to yield yet another embodiment. Accordingly, it is intended that the present invention cover such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0019] The wind turbine and aircraft industries are entering new areas and are located in more remote and extreme climates to capture energy. Airfoils, rotors, and rotor blades are also becoming more complex. In particular, in addition to pitch control, various systems, such as various systems for ice mitigation or de-icing systems, are more common and require more power. In addition, such systems operate at different potential and current levels, which sometimes cannot be maintained at a common potential due to limitations of the power device or application.

[0020] Accordingly, the present disclosure generally relates to a heating system having at least one heating element and a heating circuit electrically coupled to the heating element(s). In addition, the heating circuit is configured to receive a voltage signal from the power grid and process the voltage signal by implementing a zero-crossing detection (ZCD) algorithm on the voltage signal, superimposing a pulse-width modulation (PWM) signal onto the voltage signal, and implementing an integral cycle control (ICC) on the PWM signal (e.g., completing one or more cycles as an integer) to reduce harmonics fed into the power grid. In addition, the heating circuit is configured to provide continuous temperature control to the heating element(s) via the PWM signal and maintain the temperature of the heating element(s) within a temperature range during operation of the wind turbine using the PWM signal to minimize temperature cycling of the heating element(s).

[0021] In this regard, the systems and methods of the present disclosure are configured to simplify the operation of the heating element(s) and improve the reliability of the heating system by regulating logic and components, which ensures sinusoidal current and acceptable power quality. Accordingly, the systems and methods of the present disclosure are configured to reduce the harmonic impact on the power grid. In addition, due to the use of ICC, electromagnetic compatibility (EMC) is improved, and electromagnetic radiation is reduced and / or eliminated.

[0022] Now referring to the drawings, Figure 1 A partial perspective view of an embodiment of a wind turbine 100 according to the present disclosure is shown. In the illustrated embodiment, the wind turbine 100 is a horizontal-axis wind turbine. Alternatively, the wind turbine 100 may be a vertical-axis wind turbine. In addition, as shown, the wind turbine 100 includes a nacelle 102 that houses a generator ( Figure 1 not shown in the figure). The nacelle 102 is mounted on a tower 104 (a portion of the tower 104 is shown in Figure 1 the figure). The tower 104 may have any suitable height to facilitate operation of the wind turbine 100 as described herein. The wind turbine 100 also includes a rotor 106. The rotor 106 may include three rotor blades 108 attached to a rotating hub 110. Alternatively, the wind turbine 100 may include any number of rotor blades 108 to facilitate operation of the wind turbine 100 as described herein. The wind turbine 100 may include a gearbox ( Figure 1 not shown in the figure) operatively coupled to the rotor 106 and the generator (Figure 1 (not shown). The rotor blades 108 are spaced around the hub 110 to facilitate rotation of the rotor 106, such that kinetic energy can be converted from the wind into useful mechanical energy and subsequently into electrical energy.

[0023] The wind turbine 100 may also include a turbine controller 202 for controlling its various components. In the illustrated embodiment, the turbine controller 202 is shown centered within the nacelle 102; however, the turbine controller 202 may also be a distributed system throughout the wind turbine 100, on the support system ( Figure 1 (not shown), within the wind farm, and / or at a remote control center.

[0024] Now referring to Figure 2 , a schematic illustration of an embodiment of an electrical (power) and control system 200 that may be used with the wind turbine 100 is shown. During operation, the wind impinges on the rotor blades 108, and the rotor blades 108 convert the wind energy into mechanical rotational torque, which rotatably drives the low-speed shaft 112 via the hub 110. In an embodiment, the low-speed shaft 112 is configured to drive a gearbox 114, which then increases the low rotational speed of the low-speed shaft 112 to drive the high-speed shaft 116 at an increased rotational speed. The high-speed shaft 116 is generally rotatably coupled to the generator 118 to rotatably drive a generator rotor 122 having field windings (not shown).

[0025] More specifically, in an embodiment, the generator 118 may be a wound-rotor three-phase doubly-fed induction (asynchronous) generator (DFIG) that includes a generator stator 120 magnetically coupled to the generator rotor 122. In this regard, a rotating magnetic field may be induced by the generator rotor 122, and a voltage may be induced within the generator stator 120 magnetically coupled to the generator rotor 122. In such embodiments, the generator 118 is configured to convert the rotational mechanical energy into a sinusoidal three-phase alternating current (AC) electrical energy signal in the generator stator 120. The associated electrical power may be transmitted to the main step-up transformer 234 via the stator bus 208, the stator synchronous switch 206, the system bus 216, the step-up transformer circuit breaker 214, and the generator-side bus 236. The step-up transformer 234 increases the voltage amplitude of the electrical power such that the converted electrical power can be further transmitted to the power grid via the grid circuit breaker 238, the breaker-side bus 240, and the grid bus 242.

[0026] Additionally, the turbine controller 202 is configured to control any of the components of the wind turbine 100 and / or implement any of the method steps described herein. For example, as particularly in Figure 3As shown, the turbine controller 202 may include one or more processors 204 and associated memory devices 207 configured to perform a variety of computer-implemented functions (e.g., execute methods, steps, calculations, etc., and store related data as disclosed herein). Additionally, the turbine controller 202 may also include a communication module 209 to facilitate communication between the turbine controller 202 and various components of the wind turbine 100 (e.g., Figure 2 any of the components of). The communication module 209 may include a sensor interface 211 (e.g., one or more analog-to-digital converters) to allow signals transmitted from one or more sensors to be converted into signals that can be understood and processed by the processor 204. It should be appreciated that the sensors (e.g., sensors 252, 254, 256, 258) may be communicatively coupled to the communication module 209 using any suitable means. For example, as Figure 3 shown, the sensors 252, 254, 256, 258 may be coupled to the sensor interface 211 via a wired connection. However, in other embodiments, the sensors 252, 254, 256, 258 may be coupled to the sensor interface 211 via a wireless connection (such as by using any suitable wireless communication protocol known in the art). In this regard, the processor 204 may be configured to receive one or more signals from the sensors 252, 254, 256, 258.

[0027] Additionally, at least one additional sensor (not shown) may be provided for sensor data related to meteorological data, such as the sensors provided by a meteorological mast. The at least one additional sensor may specifically include a sensor for determining the wind speed at the rotor 106 of the wind turbine 100.

[0028] As used herein, the term "processor" refers not only to integrated circuits known in the art as being included in a computer, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits, and other programmable circuits. The processor 204 is also configured to compute advanced control algorithms and communicate with a variety of Ethernet or serial-based protocols (Modbus, OPC, CAN, etc.). Additionally, the memory devices 207 may generally include memory elements, including but not limited to computer-readable media (e.g., random access memory (RAM)), computer-readable non-volatile media (e.g., flash memory), floppy disks, compact disc read-only memory (CD-ROM), magneto-optical discs (MOD), digital versatile discs (DVD), and / or other suitable memory elements. Such memory devices 207 may generally be configured to store suitable computer-readable instructions that, when executed by the processors 204, configure the turbine controller 202 to perform the various functions described herein.

[0029] Still referring to Figure 2 , the generator stator 120 can be electrically coupled to the stator synchronous switch 206 via the stator bus 208. In an embodiment, for facilitating the DFIG configuration, the generator rotor 122 is electrically coupled to the bidirectional power conversion assembly 210 via the rotor bus 212. Alternatively, the generator rotor 122 is electrically coupled to the rotor bus 212 via any other device facilitating the operation of the electrical and control system 200 as described herein. As yet another alternative, the electrical and control system 200 is configured as a full power conversion system (not shown), which includes a full power conversion assembly ( Figure 2 not shown in), which is similar in design and operation to the power conversion assembly 210 and is electrically coupled to the generator stator 120. The full power conversion assembly facilitates directing electrical power between the generator stator 120 and an electrical power transmission and distribution network (not shown).

[0030] In an embodiment, the stator bus 208 transmits three-phase power from the generator stator 120 to the stator synchronous switch 206. The rotor bus 212 transmits three-phase power from the generator rotor 122 to the power conversion assembly 210. In an embodiment, the stator synchronous switch 206 is electrically coupled to the step-up transformer circuit breaker 214 via the system bus 216. In an embodiment, one or more fuses (not shown) are used in place of the step-up transformer circuit breaker 214. In another embodiment, neither fuses nor the step-up transformer circuit breaker 214 are used.

[0031] The power conversion assembly 210 includes a rotor filter 218, which is electrically coupled to the generator rotor 122 via the rotor bus 212. The rotor filter bus 219 electrically couples the rotor filter 218 to the rotor-side power converter 220, and the rotor-side power converter 220 is electrically coupled to the line-side power converter 222. The rotor-side power converter 220 and the line-side power converter 222 are power converter bridges including power semiconductors (not shown). In an embodiment, the rotor-side power converter 220 and the line-side power converter 222 are configured in a three-phase pulse width modulation (PWM) configuration, which includes insulated gate bipolar transistor (IGBT) switching devices ( Figure 2 not shown in) operating as known in the art. Alternatively, the rotor-side power converter 220 and the line-side power converter 222 have any configuration using any switching device facilitating the operation of the electrical and control system 200 as described herein. The power conversion assembly 210 is coupled to the turbine controller 202 in electronic data communication to control the operation of the rotor-side power converter 220 and the line-side power converter 222.

[0032] In an embodiment, a line - side power - converter bus 223 electrically couples a line - side power converter 222 to a line filter 224. Additionally, a line bus 225 electrically couples the line filter 224 to a line contactor 226. Further, the line contactor 226 is electrically coupled to a transfer breaker 228 via a transfer - breaker bus 230. Additionally, the transfer breaker 228 is electrically coupled to a step - up transformer breaker 214 via a system bus 216 and a connection bus 232. Alternatively, the line filter 224 is directly electrically coupled to the system bus 216 via the connection bus 232 and includes any suitable protection scheme (not shown) configured to account for the removal of the line contactor 226 and the transfer breaker 228 from the electrical and control system 200. The step - up transformer breaker 214 is electrically coupled to a step - up transformer 234 via a generator - side bus 236. Additionally, the step - up transformer 234 is electrically coupled to a grid breaker 238 via a breaker - side bus 240. The grid breaker 238 is connected to an electric - power transmission and distribution grid via a grid bus 242. In an alternative embodiment, the step - up transformer 234 is electrically coupled to one or more fuses (not shown) via the breaker - side bus 240 instead of the grid breaker 238. In another embodiment, neither fuses nor the grid breaker 238 are used, and instead, the step - up transformer 234 is coupled to the electric - power transmission and distribution grid via the breaker - side bus 240 and the grid bus 242.

[0033] Still referring to Figure 2 , in an embodiment, a rotor - side power converter 220 is electrically communicatively coupled to the line - side power converter 222 via a single direct - current (DC) link 244. Alternatively, the rotor - side power converter 220 and the line - side power converter 222 are electrically coupled via separate and distinct DC links ( Figure 2 not shown). Additionally, as shown, the DC link 244 includes a positive rail 246, a negative rail 248, and at least one capacitor 250 coupled between the positive rail 246 and the negative rail 248. Alternatively, the capacitor 250 includes one or more capacitors configured in series and / or parallel between the positive rail 246 and the negative rail 248.

[0034] In an embodiment, the turbine controller 202 is configured to receive a plurality of voltage and current measurement signals from a first set of voltage and current sensors 252. Additionally, the turbine controller 202 is configured to monitor and control at least some of the operating variables associated with the wind turbine 100. In an embodiment, each of the three voltage and current sensors 252 is electrically coupled to each of the three phases of the grid bus 242. Thus, the current frequency of the grid can be determined by the turbine controller 202. Alternatively or additionally, the turbine controller 202 can be functionally coupled to a frequency sensor capable of connecting to the grid. Further, it is possible that via a main facility controller, such as a wind farm controller functionally coupled to the respective sensors, the turbine controller 202 receives the current frequency of the grid, or at least a signal representative of the current frequency of the grid.

[0035] As Figure 2 shown, the electrical and control system 200 also includes a converter controller 262, which is configured to receive a plurality of voltage and current measurement signals. For example, in one embodiment, the converter controller 262 receives voltage and current measurement signals from a second set of voltage and current sensors 254, which are electronically data-communicatively coupled to the exemplary three-phase stator bus 208. The converter controller 262 receives a third set of voltage and current measurement signals from a third set of voltage and current sensors 256, which are electronically data-communicatively coupled to the rotor bus 212. Additionally, in an embodiment, the converter controller 262 also receives a fourth set of voltage and current measurement signals from a fourth set of voltage and current sensors 258, which are electronically data-communicatively coupled to the converter breaker bus 230. The second set of voltage and current sensors 254 is substantially similar to the first set of voltage and current sensors 252, while the fourth set of voltage and current sensors 264 is substantially similar to the third set of voltage and current sensors 256. Additionally, in an embodiment, the converter controller 262 is substantially similar to the turbine controller 202 and is electronically data-communicatively coupled to the turbine controller 202. Further, in an embodiment, the converter controller 262 is physically integrated within the power conversion assembly 210. Alternatively, the converter controller 262 has any configuration facilitating the operation of the electrical and control system 200 as described herein.

[0036] During operation, wind impinges on rotor blades 108, and the rotor blades 108 convert wind energy into mechanical rotational torque, which rotatably drives a low-speed shaft 112 via a hub 110. The low-speed shaft 112 drives a gearbox 114, which then increases the low rotational speed of the low-speed shaft 112 to drive a high-speed shaft 116 at an increased rotational speed. The high-speed shaft 116 rotatably drives a generator rotor 122. A rotating magnetic field is induced by the generator rotor 122, and a voltage is induced within a generator stator 120 that is magnetically coupled to the generator rotor 122. The generator converts the rotational mechanical energy into a sinusoidal three-phase alternating current (AC) electrical power signal in the generator stator 120. In an embodiment, the associated electrical power is transmitted to a step-up transformer 234 via a stator bus 208, a stator synchronous switch 206, a system bus 216, a step-up transformer circuit breaker 214, and a generator-side bus 236. The step-up transformer 234 increases the voltage amplitude of the electrical power, and the converted electrical power is further transmitted to the power grid via a breaker-side bus 240, a grid circuit breaker 238, and a grid bus 242.

[0037] In an embodiment, a second electrical power transmission path is provided. Three-phase sinusoidal AC electrical power is generated within the generator rotor 122 and transmitted via a rotor bus 212 to a power conversion assembly 210. Within the power conversion assembly 210, the electrical power is transmitted to a rotor filter 218 and modified for the rate of change of a PWM signal associated with a rotor-side power converter 220. The rotor-side power converter 220 acts as a rectifier and rectifies the sinusoidal three-phase AC power into DC power. The DC power is transmitted into a DC link 244. A capacitor 250 facilitates mitigation of DC link voltage amplitude variations by facilitating mitigation of DC ripple associated with AC rectification.

[0038] The DC power then is transmitted from the DC link 244 to a line-side power converter 222, and the line-side power converter 222 serves as an inverter configured to convert the DC electrical power from the DC link 244 into three-phase sinusoidal AC electrical power having a predetermined voltage, current, and frequency. This conversion is monitored and controlled via a converter controller 262. The converted AC power is transmitted from the line-side power converter 222 to the system bus 216 via a line-side power converter bus 223, a line bus 225, a line contactor 226, a transfer breaker bus 230, a transfer breaker 228, and a connection bus 232. A line filter 224 compensates for or adjusts harmonic currents in the electrical power transmitted from the line-side power converter 222. The stator synchronous switch 206 may be closed to facilitate connection of the three-phase power from the generator stator 120 with the three-phase power from the power conversion assembly 210.

[0039] The transfer circuit breaker 228, the step-up transformer circuit breaker 214, and the grid circuit breaker 238 are configured to disconnect the corresponding busbars, for example, when excessive current may damage components of the electrical and control system 200. Additional protection components are also provided, including line contactors 226, which are controllable to disconnect the corresponding busbars by opening a switch ( Figure 2 (not shown) to form a disconnection.

[0040] In this regard, power conversion assembly 210 compensates or adjusts the frequency of three-phase power from generator rotor 122 for variations in, for example, wind speed at hub 110 and rotor blades 108. Thus, in this manner, the mechanical and electrical rotor frequencies are decoupled from the stator frequency.

[0041] Now refer to Figure 4 , showing Figure 1 A simplified schematic diagram of an embodiment of a wind turbine 100 is shown, which particularly illustrates an ice detection and heating system 300 (also referred to herein as a "heating system") according to the present disclosure. Because the configuration of this embodiment is similar to Figure 1 , so only the differences will be described. As shown, heating system 300 may generally include a detection device 302 connected to a sensor device 304 disposed with one or more of rotor blades 108 (such as the root of rotor blade 108). Furthermore, as shown, sensor device 304 is adapted to measure loads and / or vibrations of rotor blades 108. Although sensor device 304 is shown as only a single sensor for all three rotor blades 108, it may also be advantageous to use a separate sensor for each rotor blade 108. Thus, imbalances in rotor blades 108 may be readily detected by sensor device 304. In this regard, heating system 300 uses sensor data to detect icing conditions on wind turbine 100. In response, heating system 300 is configured to activate one or more heating elements 306 disposed with one or more rotor blades 108 of wind turbine 100 (or any other wind turbine component) to mitigate icing thereon. More specifically, as will be explained in greater detail, heating system 300 includes a heating circuit 350 electrically coupled to heating element(s) 306 .

[0042] Now refer to Figure 5 , a flow chart illustrating an embodiment of a method 400 of operating a heating system (such as heating system 300) of a wind turbine connected to a power grid according to the present disclosure. Figure 1-4 The method 400 is described with reference to the wind turbine 100 and the electrical and control system 200 described herein. However, one skilled in the art will recognize that the disclosed method 400 may generally be used to operate any other wind turbine having any suitable configuration.Figure 5 Steps are depicted in a particular order for purposes of illustration and discussion, but the methods discussed herein are not limited to any particular order or arrangement. Using the disclosures provided herein, those skilled in the art will recognize that the various steps of the methods disclosed herein may be omitted, rearranged, combined, and / or modified in various ways without departing from the scope of the present disclosure.

[0043] As shown at (402), method 400 includes receiving a voltage signal from the power grid via a heating circuit of a heating system. As shown at (404), method 400 includes processing the voltage signal using the heating circuit of the heating system, wherein processing the voltage signal using the heating circuit of the heating system includes superimposing a pulse width modulation (PWM) signal onto the voltage signal. As shown at (406), method 400 includes providing continuous temperature control to at least one heating element of the heating system via the PWM signal from the heating circuit. As shown at (408), method 400 includes maintaining the temperature of the at least one heating element within a temperature range using the PWM signal during operation of the wind turbine to minimize temperature cycling of the at least one heating element.

[0044] Reference may be made to Figure 6 for a better understanding of Figure 5 the method. In particular, as shown, a schematic diagram of an embodiment of a heating circuit 350 according to the present disclosure is shown. As shown, the heating circuit 350 receives a voltage signal 352 from the power grid. Additionally, as shown, the heating circuit 350 is then configured to process the voltage signal 352. More specifically, as shown, the heating circuit 350 is configured to process the voltage signal 352 by implementing a zero crossing detection (ZCD) algorithm on the voltage signal 352 via a ZCD module 354 to provide a smooth start for temperature control.

[0045] As used herein, the ZCD module 354 is configured to change the comparator output state when the AC input crosses a zero reference voltage. In an embodiment, this may be achieved by setting the comparator inverting input to the zero reference voltage and applying the attenuated input to the non-inverting input. One or more voltage dividers attenuate the input AC signal, and diodes are used to ensure that the non-inverting input never falls below the negative input common mode limit of the comparator.

[0046] In addition, in an embodiment, the heating circuit 350 is then configured to process the voltage signal 352 by superimposing a pulse width modulation (PWM) signal onto the voltage signal 352, e.g., after performing a zero crossing detection (ZCD) algorithm on the voltage signal 352. Further, as shown, the heating circuit 350 is configured to perform integral cycle control (ICC) on the PWM signal via an integral cycle control (ICC) module 358 to reduce the harmonics fed into the power grid. As used herein, integral cycle control generally refers to a converter having the ability to perform direct switching losslessly. In an example, the process directly converts AC to AC without having to perform the intermediate processes of AC to DC and then DC to AC.

[0047] Accordingly, the output of the ICC module 358 is then fed to the semiconductor device 360. In this regard, in an embodiment, providing continuous temperature control to the heating element(s) 306 via the PWM signal from the heating circuit 350 may include gating and shutting off the semiconductor device(s) 360 to apply the PWM signal to the heating element(s) 306 to provide power thereto. In an embodiment, for example, the semiconductor device(s) 360 of the heating circuit 350 may be any one of or a combination of thyristors, diodes, metal oxide semiconductor field effect transistors (MOFSETs), and / or insulated gate bipolar transistors (IGBTs).

[0048] Now referring Figure 7 , an example voltage signal 400 superimposed with a PWM signal 402 is shown in accordance with the present disclosure. Thus, as shown, the PWM superposition of the present disclosure provides thermal performance smoothing and thermal stress elimination of the rotor blade 108. Further, the ICC module eliminates the harmonics fed back to the power grid, thereby saving power quality and unwanted overheating. Accordingly, the electrical stress of the entire system is reduced and there is no electromagnetic interference (EMI) problem. Further, the ZCD module provides a smooth start for the heating circuit 350, which also reduces the electrical stress and EMI generation during startup.

[0049] Additional aspects of the present invention are provided by the subject matter of the following clauses:

[0050] A method of operating a heating system of a wind turbine connected to a power grid, the method comprising: receiving a voltage signal from the power grid via a heating circuit of the heating system; processing the voltage signal using the heating circuit of the heating system, wherein processing the voltage signal using the heating circuit of the heating system includes superimposing a pulse width modulation (PWM) signal onto the voltage signal; providing continuous temperature control to at least one heating element of the heating system via the PWM signal from the heating circuit; and during operation of the wind turbine, maintaining the temperature of the at least one heating element within a temperature range using the PWM signal to minimize temperature cycling of the at least one heating element.

[0051] The method as described in any of the preceding clauses, wherein processing the voltage signal using the heating circuit of the heating system further comprises: implementing a zero-crossing detection (ZCD) algorithm on the voltage signal to provide a smooth start for temperature control.

[0052] The method as described in any of the preceding clauses, wherein superimposing the PWM signal onto the voltage signal occurs after implementing the ZCD algorithm on the voltage signal.

[0053] The method as described in any of the preceding clauses, wherein processing the voltage signal using the heating circuit of the heating system further comprises: implementing an integral cycle control (ICC) on the PWM signal to reduce the harmonics fed into the power grid.

[0054] The method as described in any of the preceding clauses, wherein superimposing the PWM signal onto the voltage signal occurs before implementing the ICC on the PWM signal.

[0055] The method as described in any of the preceding clauses, wherein providing continuous temperature control to at least one heating element of the heating system via the PWM signal from the heating circuit further comprises: gating and turning off at least one semiconductor device of the heating circuit to apply the PWM signal to at least one heating element so as to provide power to at least one heating element.

[0056] The method as in any of the preceding clauses, wherein at least one semiconductor device of the heating circuit comprises at least one of a thyristor, a diode, a metal-oxide-semiconductor field-effect transistor (MOFSET), or an insulated-gate bipolar transistor (IGBT).

[0057] The method as in any of the preceding clauses, the method further comprising arranging at least one heating element of the heating system on one or more rotor blades of a wind turbine.

[0058] A heating system, comprising: at least one heating element; and a heating circuit electrically coupled to the at least one heating element, the heating circuit configured to perform a plurality of operations, the plurality of operations including: receiving a voltage signal from a power grid; processing the voltage signal, wherein processing the voltage signal includes superimposing a pulse-width modulation (PWM) signal onto the voltage signal; providing continuous temperature control to the at least one heating element via the PWM signal; and maintaining the temperature of the at least one heating element within a temperature range using the PWM signal to minimize the temperature cycling of the at least one heating element.

[0059] The heating system as described in any of the preceding clauses, wherein the heating circuit includes a zero-crossing detection (ZCD) module, and wherein processing the voltage signal further comprises: implementing the ZCD algorithm on the voltage signal via the ZCD algorithm module to provide a smooth start for temperature control.

[0060] A heating system as described in any of the preceding clauses, wherein superimposing the PWM signal onto the voltage signal occurs after performing the ZCD algorithm on the voltage signal via the ZCD algorithm module.

[0061] A heating system as described in any of the preceding clauses, wherein the heating circuit includes an Integral Cycle Control (ICC) module, and wherein processing the voltage signal further includes: performing ICC on the PWM signal via the ICC module to reduce harmonics fed into the power grid.

[0062] A heating system as described in any of the preceding clauses, wherein superimposing the PWM signal onto the voltage signal occurs before performing ICC on the PWM signal via the ICC module.

[0063] A heating system as described in any of the preceding clauses, wherein the heating circuit further includes at least one semiconductor device, and wherein providing continuous temperature control to at least one heating element via the PWM signal further includes: gating and turning off at least one semiconductor device to apply the PWM signal to at least one heating element so as to provide power to at least one heating element.

[0064] A heating system as described in any of the preceding clauses, wherein at least one semiconductor device of the heating circuit includes at least one of a thyristor, a diode, a Metal Oxide Semiconductor Field Effect Transistor (MOFSET), or an Insulated Gate Bipolar Transistor (IGBT).

[0065] A heating system as described in any of the preceding clauses, wherein at least one heating element of the heating system is arranged on one or more rotor blades of a wind turbine.

[0066] A wind turbine connected to a power grid, the wind turbine including: a tower; a nacelle mounted on top of the tower; a rotatable hub mounted to the nacelle, the rotatable hub having at least one rotor blade mounted thereto; a heating system for mitigating ice on the wind turbine, the heating system including: at least one heating element arranged together with at least one rotor blade; and a heating circuit electrically coupled to at least one heating element, the heating circuit configured to perform a plurality of operations, the plurality of operations including: receiving a voltage signal from the power grid; processing the voltage signal, wherein processing the voltage signal includes superimposing a Pulse Width Modulation (PWM) signal onto the voltage signal; providing continuous temperature control to at least one heating element via the PWM signal; and during operation of the wind turbine, maintaining the temperature of at least one heating element within a temperature range using the PWM signal to minimize temperature cycling of at least one heating element.

[0067] A wind turbine as described in any of the preceding clauses, wherein the heating circuit includes a zero-crossing detection (ZCD) module and an integral cycle control (ICC) module, and wherein processing the voltage signal further includes: implementing a ZCD algorithm on the voltage signal via the ZCD algorithm module to provide a smooth start for temperature control; and implementing ICC on the PWM signal via the ICC module to reduce harmonics fed into the power grid.

[0068] A wind turbine as described in any of the preceding clauses, wherein superimposing the PWM signal on the voltage signal occurs after implementing the ZCD algorithm on the voltage signal via the ZCD algorithm module and before implementing ICC on the PWM signal via the ICC module.

[0069] A wind turbine as described in any of the preceding clauses, wherein the heating circuit further includes at least one semiconductor device, and wherein providing continuous temperature control to at least one heating element via the PWM signal further includes: gating and shutting off at least one semiconductor device to apply the PWM signal to at least one heating element so as to provide power to at least one heating element, wherein at least one semiconductor device of the heating circuit includes at least one of a thyristor, a diode, a metal-oxide semiconductor field-effect transistor (MOFSET), or an insulated gate bipolar transistor (IGBT).

[0070] This written description uses examples to disclose the invention (including the best mode), and also enables those skilled in the art to practice the invention (including making and using any device or system and performing any incorporated method). The scope of patentability of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. If these other examples include structural elements that do not differ from the literal language of the claims, or if these other examples include equivalent structural elements that do not differ significantly from the literal language of the claims, then these other examples are intended to be within the scope of the claims.

Claims

1. A method of operating a heating system of a wind turbine connected to an electrical grid, the method comprising: Receiving a voltage signal from the electrical grid via a heating circuit of the heating system; Processing the voltage signal using the heating circuit of the heating system, wherein processing the voltage signal using the heating circuit of the heating system includes superimposing a pulse width modulation (PWM) signal onto the voltage signal; Providing continuous temperature control to at least one heating element of the heating system via the PWM signal from the heating circuit; And During operation of the wind turbine, maintaining the temperature of the at least one heating element within a temperature range using the PWM signal to minimize temperature cycling of the at least one heating element.

2. The method according to claim 1, wherein Processing the voltage signal using the heating circuit of the heating system further includes: Performing a zero crossing detection (ZCD) algorithm on the voltage signal to provide a smooth start for the temperature control.

3. The method according to claim 2, wherein Superimposing the PWM signal onto the voltage signal occurs after performing the ZCD algorithm on the voltage signal.

4. The method according to claim 3, wherein, Processing the voltage signal using the heating circuit of the heating system further includes: Performing an integral cycle control (ICC) on the PWM signal to reduce harmonics fed into the electrical grid.

5. The method according to claim 4, wherein Superimposing the PWM signal onto the voltage signal occurs before performing the ICC on the PWM signal.

6. The method according to claim 1, wherein, Providing the continuous temperature control to the at least one heating element of the heating system via the PWM signal from the heating circuit further includes: Gating and turning off at least one semiconductor device of the heating circuit to apply the PWM signal to the at least one heating element to provide power to the at least one heating element.

7. The method according to claim 6, wherein, The at least one semiconductor device of the heating circuit includes at least one of a thyristor, a diode, a metal oxide semiconductor field effect transistor (MOFSET), or an insulated gate bipolar transistor (IGBT).

8. The method according to claim 1, the method further comprising arranging the at least one heating element of the heating system on one or more rotor blades of the wind turbine.

9. A heating system, comprising: At least one heating element; And A heating circuit electrically coupled to the at least one heating element, the heating circuit configured to perform a plurality of operations, the plurality of operations including: Receiving a voltage signal from the electrical grid; Processing the voltage signal, wherein processing the voltage signal includes superimposing a pulse width modulation (PWM) signal onto the voltage signal; Providing continuous temperature control to the at least one heating element via the PWM signal; and Maintaining the temperature of the at least one heating element within a temperature range using the PWM signal to minimize temperature cycling of the at least one heating element.

10. The heating system according to claim 9, wherein, The heating circuit includes a zero crossing detection (ZCD) module, wherein processing the voltage signal further includes: Performing a ZCD algorithm on the voltage signal via the ZCD algorithm module to provide a smooth start for the temperature control.

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