Selective crowbar response of power converters for mitigating equipment failure

Abstract

A method for operating a multi-stage bridge power converter in an electrical power system includes connecting multiple phases of the power converter to a common terminal on the DC side of the power converter to effectively make the multiple phases equal at a common potential. The method may further include fault monitoring of multiple devices of the power converter via a controller. Upon detecting a fault in one or more of the multiple devices, the method includes activating one or more protective devices of the power converter via the controller to prevent further faults in the remaining devices by diverting energy from the remaining devices.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to electrical power systems, and more particularly to selective crowbar response of power converters of electrical power systems for mitigating equipment failures. BACKGROUND

[0002] Wind turbines have received increasing attention as a source of renewable energy. Wind turbines use wind to generate electrical power. The wind turns a plurality of blades connected to a rotor. The rotation of the blades caused by the wind rotates a shaft of the rotor, which is connected to a generator that generates electrical power. Certain wind turbines include a doubly-fed induction generator (DFIG) to convert wind energy into electrical power suitable for output to a power grid. The DFIG is typically connected to a converter that regulates the flow of electrical power between the DFIG and the power grid. More particularly, the converter allows the wind turbine to output electrical power at a grid frequency, regardless of the rotational speed of the wind turbine blades.

[0003] A typical DFIG system includes a wind-driven DFIG having a rotor and a stator. The stator of the DFIG is coupled to a power grid through a stator bus. A power converter is used to couple the rotor of the DFIG to the power grid. The power converter can be a two-stage power converter that includes both a rotor-side converter and a line-side converter. The rotor-side converter can receive alternating current (AC) power from the rotor via a rotor bus and can convert the AC power to DC power. The line-side converter can then convert the DC power to AC power having a suitable output frequency, such as a grid frequency. The AC power is provided to the power grid via a line bus. An auxiliary power feeder can be coupled to the line bus to provide power to components used in the wind turbine system, such as fans, pumps, motors, and other components of the wind turbine system.

[0004] A typical DFIG system includes a dual-winding transformer having a high voltage primary winding (e.g., greater than 12 KV AC) and a low voltage secondary winding (e.g., 575 V AC, 690 V AC, etc.) to couple the DFIG system to the power grid. The high voltage primary winding can be coupled to a high voltage power grid. A stator bus providing AC power from the stator of the DFIG and a line bus providing AC power from the power converter can be coupled to the low voltage secondary winding. In this system, the output power of the stator and the output power of the power converter are operated at the same voltage and are combined into a single transformer secondary winding at a low voltage.

[0005] Recently, DFIG systems have included a three-winding transformer to couple the DFIG system to the power grid. The three-winding transformer can have a high voltage (e.g., greater than 12 KV AC) primary winding coupled to the power grid, a medium voltage (e.g., 6 KV AC) secondary winding coupled to the stator bus, and a low voltage (e.g., 575 V AC, 690 V AC, etc.) auxiliary winding coupled to the line bus. The three-winding transformer arrangement can be preferred in systems with increased output power (e.g., 3 MW systems) as it reduces the current in the stator bus and other components on the stator side of the DFIG.

[0006] During operation of a wind turbine system, including a DFIG system, various fault events can occur, including grid under- or over-voltage conditions and faults within the power system and / or associated wind turbine. This can result in excess energy in the power converter, which can result in damage to the converter.

[0007] Various methods have been utilized to reduce the risk of over-voltage conditions in power converters. For example, when a grid fault occurs, a crowbar has been utilized as an initial measure to prevent excess energy from reaching the power converter. A braking chopper has also been utilized as an initial measure to absorb such excess energy. Furthermore, during a device failure on a multi-stage bridge power converter, continued operation without addressing the initial failure can induce failure propagation, which can damage all devices in the power converter. Thus, if the initial failure is not quickly controlled, damage can occur in the remaining stages, effectively destroying the entire converter.

[0008] Accordingly, an improved method for operating a multi-stage bridge power converter of an electrical power system that addresses the above problems is desirable in the art. In particular, an improved method that utilizes selective crowbar response of the power converter of the electrical power system to mitigate device failures would be advantageous. SUMMARY

[0009] Aspects and advantages of the application will be set forth in part in the following description, or can be obvious from the description, or can be learned through practice of the application.

[0010] In one aspect, the present disclosure relates to a method for operating a multi-level bridge power converter of an electric power system. The power converter includes a rotor-side converter coupled to a line-side converter via a DC link. The method includes connecting a plurality of phases of the power converter to a common terminal at a DC side of the power converter so as to effectively equalize the plurality of phases at a common electrical potential. The method can also include fault monitoring, via a controller, of a plurality of devices of the power converter. Upon detecting a fault in one or more of the plurality of devices, the method includes activating, via the controller, one or more protection devices of a crowbar of the power converter to prevent an additional fault in a remaining one or more of the plurality of devices by diverting energy away from the remaining one or more of the plurality of devices.

[0011] In one embodiment, the method can also include detecting, via the controller, a location of the fault in one or more of the plurality of devices. In such an embodiment, activating the crowbar of the power converter to prevent the additional fault of the plurality of devices can include selecting a crowbar response from a plurality of crowbar responses based on the location of the fault in one or more of the plurality of devices and activating the selected crowbar response.

[0012] In particular embodiments, the fault can be a bridge fault on a bridge circuit of the power converter.

[0013] In another embodiment, the protection device(s) can include a fuse, a switching element, or a combination thereof. In certain embodiments, the protection device(s) can include one or more switching elements of at least one of the rotor-side converter or the line-side converter. Alternatively, the protection device(s) can include one or more switching elements disposed upstream or downstream of at least one of the rotor-side converter or the line-side converter.

[0014] In further embodiments, the plurality of devices can include one or more semiconductor switches.

[0015] In further embodiments, the electric power system can include a wind turbine power system, a solar power system, an energy storage power system, or a combination thereof.

[0016] In another aspect, the present disclosure relates to an electric power system. The electric power system includes a doubly-fed induction generator having a rotor and a stator. The stator provides AC power to a stator bus. The system also includes a multi-level bridge power converter coupled to the rotor of the doubly-fed induction generator. The power converter provides an output to a line bus and includes a rotor-side converter, a line-side converter, a DC link, and a plurality of phases connected to a common terminal at a DC side of the power converter so as to effectively equalize the plurality of phases at a common potential. Further, the system includes a controller communicatively coupled to the power converter. The controller is configured to perform a plurality of operations including, but not limited to: fault monitoring of a plurality of devices of the power converter; and upon detection of a fault in one or more of the plurality of devices, activating one or more protection devices of a crowbar of the power converter via the controller to prevent additional faults in a remainder of the plurality of devices by diverting energy away from the remainder of the plurality of devices. It should be appreciated that the electric power system can also include any additional features described herein.

[0017] In yet another aspect, the present disclosure relates to a method for operating a multi-level bridge power converter of an electric power system. The power converter includes a rotor-side converter coupled to a line-side converter via a DC link. The method includes connecting a plurality of phases of the power converter to a common terminal at a DC side of the power converter. Further, the method includes monitoring one or more parameters of a plurality of devices of the power converter via a controller. Upon detection of the one or more parameters indicating a fault in one or more of the plurality of devices, the method includes activating one or more protection devices of a crowbar of the power converter via the controller to prevent additional faults in a remainder of the plurality of devices by diverting energy away from the remainder of the plurality of devices.

[0018] In such embodiments, the parameter(s) can include at least one of a current, a voltage, a desaturation event, or a combination thereof. It should be appreciated that the method can also include any additional steps and / or features described herein.

[0019] Technical Solution 1. A method for operating a multi-level bridge power converter of an electric power system, the power converter including a rotor-side converter coupled to a line-side converter via a DC link, the method comprising:

[0020] connecting a plurality of phases of the power converter to a common terminal at a DC side of the power converter so as to effectively equalize the plurality of phases at a common potential;

[0021] fault monitoring of a plurality of devices of the power converter via a controller; and

[0022] Upon detecting a fault in one or more of the plurality of devices, activating, via the controller, one or more protection devices of the crowbar of the power converter to prevent additional faults in the remaining ones of the plurality of devices by diverting energy away from the remaining ones of the plurality of devices.

[0023] Technical solution 2. The method of technical solution 1, further comprising detecting, via the controller, a location of the fault in one or more of the plurality of devices.

[0024] Technical solution 3. The method of technical solution 2, wherein activating the crowbar of the power converter to prevent additional faults of the plurality of devices further comprises:

[0025] selecting a crowbar response from a plurality of crowbar responses based on the location of the fault in one or more of the plurality of devices; and

[0026] activating the selected crowbar response.

[0027] Technical solution 4. The method of technical solution 1, wherein the fault comprises a bridge fault on a bridge circuit of the power converter.

[0028] Technical solution 5. The method of technical solution 1, wherein the one or more protection devices comprise at least one of a fuse, a switching element, or a combination thereof.

[0029] Technical solution 6. The method of technical solution 1, wherein the one or more protection devices comprise one or more switching elements of at least one of the rotor-side converter or the line-side converter.

[0030] Technical solution 7. The method of technical solution 1, wherein the one or more protection devices comprise one or more switching elements disposed upstream or downstream of at least one of the rotor-side converter or the line-side converter.

[0031] Technical solution 8. The method of technical solution 1, wherein the plurality of devices comprise one or more semiconductor switches.

[0032] Technical solution 9. The method of technical solution 1, wherein the electrical power system comprises a wind turbine power system, a solar power system, an energy storage power system, or a combination thereof.

[0033] Technical solution 10. An electrical power system, comprising:

[0034] A doubly-fed induction generator having a rotor and a stator, the stator providing AC power to a stator bus;

[0035] A multi-level bridge power converter coupled to the rotor of the doubly-fed induction generator, the power converter providing an output to a line bus, the power converter including a rotor-side converter, a line-side converter, a DC link, and a plurality of phases connected to a common terminal at a DC side of the power converter so as to effectively equalize the plurality of phases at a common potential; and

[0036] A controller communicatively coupled to the power converter, the controller configured to perform a plurality of operations, the plurality of operations including:

[0037] Fault monitoring a plurality of devices of the power converter; and

[0038] Upon detection of a fault in one or more of the plurality of devices, activating one or more protective devices of the power converter via the controller to prevent additional faults in remaining ones of the plurality of devices by diverting energy away from the remaining ones of the plurality of devices.

[0039] Technical solution 11. The electrical power system of technical solution 10, further comprising detecting, via the controller, a location of the fault in the one or more of the plurality of devices.

[0040] Technical solution 12. The electrical power system of technical solution 11, wherein activating the crowbar of the power converter to prevent additional faults of the plurality of devices further comprises:

[0041] selecting a crowbar response from a plurality of crowbar responses based on the location of the fault in the one or more of the plurality of devices; and

[0042] activating the selected crowbar response.

[0043] Technical solution 13. The electrical power system of technical solution 10, wherein the fault comprises a bridge fault on a bridge circuit of the power converter.

[0044] Technical solution 14. The electrical power system of technical solution 10, wherein the one or more protective devices comprise a fuse or a switching element.

[0045] Technical solution 15. The electrical power system of technical solution 10, wherein the one or more protective devices comprise a switching element of at least one of the rotor-side converter or the line-side converter.

[0046] Technical Solution 16. The electric power system of Technical Solution 10, characterized in that the one or more protection devices include a switching element disposed upstream of the rotor-side converter within the power converter.

[0047] Technical Solution 17. The electric power system of Technical Solution 10, characterized in that the electric power system includes a wind turbine power system, a solar power system, an energy storage power system, or a combination thereof.

[0048] Technical Solution 18. A method for operating a multi-level bridge power converter of an electric power system, the power converter including a rotor-side converter coupled to a line-side converter via a DC link, the method comprising:

[0049] connecting a plurality of phases of the power converter to a common terminal at a DC side of the power converter;

[0050] monitoring, via a controller, one or more parameters of a plurality of devices of the power converter; and

[0051] upon detecting that the one or more parameters indicate a fault occurrence in one or more of the plurality of devices, activating, via the controller, one or more protection devices of a crowbar of the power converter to prevent additional fault occurrences in remaining ones of the plurality of devices by diverting energy away from the remaining ones of the plurality of devices.

[0052] Technical Solution 19. The method of Technical Solution 18, characterized in that the one or more parameters include at least one of a current, a voltage, a desaturation event, or a combination thereof.

[0053] Technical Solution 20. The method of Technical Solution 18, characterized in that further comprising detecting, via the controller, a location of the fault in the one or more of the plurality of devices, wherein activating the crowbar of the power converter to prevent additional faults of the plurality of devices further comprises selecting a crowbar response from a plurality of crowbar responses based on the location of the fault in the one or more of the plurality of devices and activating the selected crowbar response.

[0054] These and other features, aspects, and advantages of the present application will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and serve to explain the principles of the application. BRIEF DESCRIPTION OF DRAWINGS

[0055] The complete and enabling disclosure of the present application, including the best mode thereof, to one of ordinary skill in the art, is set forth in the specification, which is to be read in conjunction with the appended drawings, wherein:

[0056] Figure 1 A perspective view of one embodiment of a wind turbine according to the present disclosure is shown;

[0057] Figure 2 An internal perspective view of one embodiment of a nacelle of a wind turbine according to the present disclosure is shown;

[0058] Figure 3 A schematic diagram of one embodiment of suitable components that can be included within a controller of a wind turbine and / or an electrical power system according to the present disclosure is shown;

[0059] Figure 4 A schematic diagram of one embodiment of an electrical power system according to the present disclosure is shown;

[0060] Figure 5 A schematic diagram of one embodiment of an electrical power system according to the present disclosure is shown;

[0061] Figure 6 A flow diagram of one embodiment of a method according to the present disclosure is shown; and

[0062] Figure 7 A flow diagram of another embodiment of a method according to the present disclosure is shown. DETAILED DESCRIPTION

[0063] Reference will now be made in detail to embodiments of the application, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the application, not limitation of the application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the scope or spirit of the application. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present application cover modifications and variations of this application provided they come within the scope of the appended claims and their equivalents.

[0064] Reference will now be made to the drawings, in which Figure 1A perspective view of one embodiment of a wind turbine 10 according to the present disclosure is shown. As shown, the wind turbine 10 includes a tower 12 extending from a support surface 14, a nacelle 16 mounted on the tower 12, and a rotor 18 coupled to the nacelle 16. The rotor 18 includes a rotatable hub 20 and at least one rotor blade 22, the rotor blade 112 being coupled to and extending outward from the hub 20. For example, in the illustrated embodiment, the rotor 18 includes three rotor blades 22. However, in alternative embodiments, the rotor 18 may include more or fewer than three rotor blades 22. Each rotor blade 22 may be spaced apart around the hub 20 to facilitate rotation of the rotor 18, thereby enabling kinetic energy to be converted from wind energy into usable mechanical energy, and subsequently into electrical energy. For example, the hub 20 may be rotatably coupled to a generator 24 positioned within the nacelle 16. Figure 2 This allows for the generation of electrical energy.

[0065] As shown, the wind turbine 10 may also include a turbine control system or turbine controller 26 centralized within the nacelle 16. However, it should be understood that the turbine controller 26 may be located on the wind turbine 10 or at any location within the wind turbine 10, at any location on the support surface 14, or substantially at any other location. The turbine controller 26 may be generally configured to control various operating modes (e.g., start-up or shutdown sequence) and / or components of the wind turbine 10. For example, the controller 26 may be configured to control the blade pitch or pitch angle (i.e., the angle that determines the perspective of the rotor blade 22 relative to the wind direction 28) of each of the rotor blades 22 to control the load on the rotor blade 22 by adjusting the angular position of at least one rotor blade 22 relative to the wind. For example, the turbine controller 26 may transmit appropriate control signals / commands to various pitch drives or pitch adjustment mechanisms 32 of the wind turbine 10. Figure 2 The turbine controller 26 can control the pitch angle of the rotor blades 22 individually or simultaneously. Specifically, the rotor blades 22 can be rotatably mounted to the hub 20 via one or more pitch bearings (not shown), allowing the pitch angle to be adjusted by rotating the rotor blades 22 about their pitch axis 34 using the pitch adjustment mechanism 32. Furthermore, as the wind direction 28 changes, the turbine controller 26 can be configured to control the yaw direction of the nacelle 16 about the yaw axis 36 to position the rotor blades 22 relative to the wind direction 28, thereby controlling the load acting on the wind turbine 10. For example, the turbine controller 26 can be configured to transmit control signals / commands to the yaw drive mechanism 38 of the wind turbine 10. Figure 2 This allows the cabin 16 to rotate around the yaw axis 30.

[0066] Furthermore, the turbine controller 26 can be configured to control the torque of the generator 24. For example, the turbine controller 26 can be configured to transmit control signals / commands to the generator 24 to modulate the magnetic flux generated within the generator 24, thereby regulating the torque demand on the generator 24. This temporary derating of the generator 24 reduces the rotational speed of the rotor blades 22, thereby reducing the aerodynamic load acting on the blades 22 and the reaction load acting on various other components of the wind turbine 10.

[0067] It should be understood that the turbine controller 26 may generally include a computer or any other suitable processing unit. Therefore, in several embodiments, the turbine controller 26 may include one or more processors and associated memory devices(s) configured to perform various computer-implemented functions, such as... Figure 3 As shown and discussed herein, the term "processor" as used herein refers not only to an integrated circuit considered to be included in a computer in the art, but also to a controller, microcontroller, microcomputer, programmable logic controller (PLC), application-specific integrated circuit, and other programmable circuits. Additionally, the memory devices of the turbine controller 26 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 disks (MOD), digital versatile discs (DVDs), and / or other suitable memory elements. Such memory devices may generally be configured to store suitable computer-readable instructions that, when implemented by the processor, configure the controller 26 to perform various computer-implemented functions, including but not limited to: performing proportional-integral-derivative ("PID") control algorithms, including various calculations in one or more PID control loops; and various other suitable computer-implemented functions. In addition, the turbine controller 26 may include various input / output channels for receiving inputs from sensors and / or other measuring devices and for sending control signals to various components of the wind turbine 10.

[0068] It should also be understood that controller 26 may be a single controller or may include various components, such as a pitch controller and / or a yaw controller, which communicate with the central controller for the purpose of specifically controlling pitch and yaw as discussed. Additionally, the term "controller" may also include combinations of computers, processing units, and / or related components that communicate with each other.

[0069] Now for reference Figure 2A simplified internal view of one embodiment of the nacelle 16 of a wind turbine 10 is shown. As shown, a generator 24 may be disposed within the nacelle 16. Generally, the generator 24 may be coupled to the rotor 18 of the wind turbine 10 to generate electrical power from the rotational energy produced by the rotor 18. For example, the rotor 18 may include a main rotor shaft 40 coupled to a hub 20 to rotate therewith. The generator 24 may then be coupled to the rotor shaft 40 such that rotation of the rotor shaft 40 drives the generator 24. For example, in the illustrated embodiment, the generator 24 includes a generator shaft 42 rotatably coupled to the rotor shaft 40 via a gearbox 44. However, in other embodiments, it should be understood that the generator shaft 42 may be directly rotatably coupled to the rotor shaft 40. Alternatively, the generator 24 may be directly rotatably coupled to the rotor shaft 40 (generally referred to as a "direct-drive wind turbine").

[0070] It should be understood that the rotor shaft 40 may be generally supported within the nacelle by a support frame or base plate 46 positioned on top of the wind turbine tower 12. For example, the rotor shaft 40 may be supported by the base plate 46 via a pair of shaft supports 48, 50 mounted on the base plate 46.

[0071] Additionally, as indicated herein, the turbine controller 26 may also be located within the nacelle 16 of the wind turbine 10. For example, as shown in the illustrated embodiment, the turbine controller 26 is housed within a control cabinet 52 mounted to a portion of the nacelle 16. However, in other embodiments, the turbine controller 26 may be located on and / or within the wind turbine 10 at any other suitable location or remotely from the wind turbine 10. Furthermore, as described herein, the turbine controller 26 may also be communicatively coupled to various components of the wind turbine 10 for generally controlling the wind turbine and / or such components. For example, the turbine controller 26 may be communicatively coupled to the yaw drive mechanism 38(s) of the wind turbine 10 for controlling and / or changing the direction 28 of the nacelle 16 relative to the wind. Figure 1 The turbine controller 26 can also be communicatively coupled to each pitch adjustment mechanism 32 (one of which is shown) of the wind turbine 10 for controlling and / or changing the pitch angle of the rotor blades 22 relative to the wind direction 28. For example, the turbine controller 26 can be configured to transmit control signals / commands to each pitch adjustment mechanism 32 such that one or more actuators (not shown) of the pitch adjustment mechanism 32 can be used to rotate the blades 22 relative to the hub 20. In particular, such a method can be performed using the controller 26, and the controller 26 can further control the torque regulation of the generator 24, the yaw regulation of the wind turbine 10, and / or the pitch regulation of the rotor blades 22 based on such a method discussed herein.

[0072] Now for reference Figure 3This diagram illustrates a block diagram of one embodiment of suitable components that may be included within a turbine controller 26 according to various aspects of this subject matter. As shown, the controller 26 may include one or more processors 60 and associated memory devices 62 configured to perform various computer-implemented functions (e.g., performing the methods, steps, calculations, etc. disclosed herein). Additionally, the controller 26 may include a communication module 64 to facilitate communication between the controller 26 and various components of the wind turbine 10. For example, the communication module 64 may serve as an interface to allow the turbine controller 26 to transmit control signals to each pitch adjustment mechanism 32 for controlling the pitch angle of the rotor blades 22. Furthermore, the communication module 64 may include a sensor interface 66 (e.g., one or more analog-to-digital converters) to allow input signals transmitted from, for example, various sensors to be converted into signals that can be understood and processed by the processor 60.

[0073] Now for reference Figure 4 and Figure 5 According to this disclosure, an embodiment of an electric power system 100 is shown. Specifically, as shown, system 100 is a doubly-fed induction generator (DFIG) wind turbine system. Furthermore, as shown, system 100 includes a wind turbine 10 as discussed above and an optional gearbox 44, which is connected to a generator 24. According to aspects of this disclosure, generator 24 is a doubly-fed induction generator (DFIG) 24. However, it should be understood that this disclosure is not limited to DFIG system 100 and DFIG 24, and rather, any suitable system and generator, including, for example, a full-power conversion system and a generator, is within the scope and spirit of this disclosure.

[0074] DFIG 24 is typically connected to stator bus 122 and power converter 130 via rotor bus 124. Stator bus 122 provides output multiphase power (e.g., three-phase power) from the stator of DFIG 24, and rotor bus 124 provides output multiphase power (e.g., three-phase power) from the rotor of DFIG 24. Referring to power converter 130, DFIG 24 is connected to rotor-side converter 132 via rotor bus 124. Rotor-side converter 132 is connected to line-side converter 134, and line-side converter 134 is in turn connected to line-side bus 138.

[0075] Power converter 130 may include one or more rotor-side switching elements 192 and one or more line-side switching elements 194, wherein the rotor-side switching elements 192 may be components of rotor-side converter 132 and the line-side switching elements 194 may be components of line-side converter 134. Switching elements 192 for each phase of rotor-side converter 132 may be included in the bridge of rotor-side converter 132, and switching elements 194 for each phase of line-side converter 134 may be included in the bridge of line-side converter 134. In an exemplary embodiment, switching elements 192, 194 may be IGBTs. For example, in an exemplary configuration, rotor-side converter 132 and line-side converter 134 are configured for normal operating mode in a three-phase pulse-width modulation (PWM) arrangement using insulated-gate bipolar transistors (IGBTs) as switching devices. Other suitable switching devices, such as insulated-gate rectifier thyristors, MOSFETs, bipolar transistors, silicon controlled rectifiers, or other suitable switching devices, may be used. Rotor-side converter 132 and line-side converter 134 can be connected via DC link 135, with DC link capacitor 136 spanning the DC link 135.

[0076] In some embodiments, a plurality of rotor-side converters 132 and / or line-side converters 134 may be used, and the plurality of rotor-side converters 132 and / or line-side converters 134 are electrically connected together in parallel.

[0077] Power converter 130 can be communicatively coupled to controller 26 to control the operation of rotor-side converter 132 and line-side converter 134. For example, controller 26 can send control commands to rotor-side converter 132 and line-side converter 134 to control the modulation of switching elements (such as IGBTs) used in power converter 130, thereby providing the desired active and reactive power output.

[0078] As shown in the figure, system 100 may further include a transformer 160 connecting the wind turbine system 100 to a power grid 168. In an embodiment, as shown, transformer 160 may be a three-winding transformer, comprising a high-voltage (e.g., greater than 12 kVAC) primary winding 162 connected to the power grid 168, a medium-voltage (e.g., 6 kVAC) secondary winding 164 connected to the stator bus 122, and / or a low-voltage (e.g., 575 VAC, 690 VAC, etc.) auxiliary winding 166 connected to the line bus 138. It should be understood that transformer 160 may be a three-winding transformer as shown in the figure, or alternatively a two-winding transformer having only a primary winding 162 and a secondary winding 164; a four-winding transformer having a primary winding 162, a secondary winding 164, an auxiliary winding 166, and additional auxiliary windings; or may have any other suitable number of windings.

[0079] Auxiliary power feeder 170 is connected to the output of power converter 130. Auxiliary power feeder 170 acts as a power source for various components of wind turbine system 100. For example, auxiliary power feeder 170 can provide power to fans, pumps, motors, and other suitable components of wind turbine system 100.

[0080] In operation, the power generated at DFIG 24 by rotating rotor 106 is supplied to power grid 168 via a dual path. The dual path is defined by stator bus 122 and rotor bus 124. On the rotor bus 124 side, sinusoidal multiphase (e.g., three-phase) alternating current (AC) power is supplied to power converter 130. Rotor-side power converter 132 converts the AC power supplied from rotor bus 124 into direct current (DC) power and supplies the DC power to DC link 135. Switching devices (e.g., IGBTs) used in the parallel bridging circuit of rotor-side power converter 132 can be modulated to convert the AC power supplied from rotor bus 124 into DC power suitable for DC link 135.

[0081] Line-side converter 134 converts DC power on DC link 135 into AC power at a frequency suitable for power grid 168. Specifically, the switching devices (e.g., IGBTs) used in the bridging circuit of line-side power converter 134 can be modulated to convert DC power on DC link 135 into AC power on line-side bus 138. Power from power converter 130 can be supplied to power grid 168 via auxiliary winding 166 of transformer 160.

[0082] The power converter 130 may receive control signals from, for example, the controller 26. These control signals may be based, among other things, on sensed conditions or operating characteristics of the wind turbine system 100. For example, the control signal may be based on a sensed voltage associated with the transformer 160 determined by the voltage sensor 144. As another example, the control signal may be based on a sensed voltage associated with the auxiliary power feeder 170 determined by the voltage sensor 146.

[0083] Typically, control signals are provided for controlling the operation of power converter 130. For example, feedback in the form of sensed speed of DFIG 24 can be used to control the conversion of output power from rotor bus 156 to maintain an appropriate and balanced multiphase (e.g., three-phase) power source. Other feedback from other sensors can also be used by controller 174 to control power converter 130, including, for example, stator and rotor bus voltage and current feedback. Using various forms of feedback information, switching control signals (e.g., gate timing commands for IGBTs), stator synchronization control signals, and circuit breaker signals can be generated.

[0084] On the stator bus 122 side, sinusoidal multiphase (e.g., three-phase) alternating current (AC) power is supplied from the stator of generator 120 to stator bus 122, and from stator bus 122 to transformer 160, and particularly to its secondary winding 164. System 100 may include various circuit breakers, fuses, contactors, and other devices, such as grid circuit breaker 158, stator bus circuit breaker 156, switch 154, and line bus circuit breaker 152, to connect or disconnect the corresponding bus, for example, in case of excessive current that could damage components of wind turbine system 100 or for other operational considerations. Additional protective components may also be included in wind turbine system 100.

[0085] Additionally, in some embodiments, a crowbar may be provided in the power converter 130. In some embodiments, the crowbar may include one or more protective devices, including, for example, a fuse, a switching element, or a combination thereof. For example, as Figure 4 As shown, the protection devices may include rotor-side switching element 192 and / or line-side switching element 194. In alternative embodiments, such as Figure 5 As shown, the protection device may include an additional switching element 196, which is included in the power converter 130 and located upstream and / or downstream of the rotor-side converter 132 and / or the line-side converter 134. Therefore, in this embodiment, when the crowbar is activated, the switching element (i.e., element 192 or element 196) can be turned on. When the crowbar is deactivated, the switching element (i.e., element 192 or element 196) can be turned off.

[0086] Now for reference Figure 4 to Figure 6 This disclosure also relates to a method for operating an electrical power system 100. In some embodiments, a controller 26 is configured to perform such operations. More specifically, Figure 6 A flowchart of one embodiment of a method 200 for operating an electric power system according to the present disclosure is shown. Generally, method 200 will be referred to herein. Figure 1 to Figure 5 The wind turbine 10, electric power system 100, and controller 26 shown are described herein. However, it should be understood that the disclosed method 200 can be implemented with wind turbines and power systems (such as, for example, solar power systems, energy storage power systems, or combinations thereof) having any other suitable configuration.

[0087] Furthermore, although for the purposes of explanation and discussion, Figure 6 The steps are described in a specific order, but the methods discussed herein are not limited to any particular order or arrangement. Using the disclosure provided herein, those skilled in the art will understand that the various steps of the methods disclosed herein can be omitted, rearranged, combined, and / or modified in various ways without departing from the scope of this disclosure.

[0088] As shown in (202), method 200 includes connecting a plurality of phases of power converter 130 to a common terminal on the DC side of the power converter to effectively make the plurality of phases equal at a common potential. As shown in (204), method 200 includes fault monitoring of a plurality of devices of power converter 130 via controller 26. For example, in a particular embodiment, the fault may be a bridging fault on the bridging circuitry of power converter 130. Accordingly, a fault may occur in one or more of the switching elements (i.e., semiconductor switches) of power converter 130.

[0089] As shown in (206), method 200 determines whether a fault is detected. If a fault is detected in one or more of the plurality of devices, as shown in (208), method 200 may further include detecting the location of the fault in one or more of the plurality of devices via controller 26. Therefore, as shown in (210), method 200 also includes activating one or more protective devices of the power converter 130 via controller 26 to prevent further faults in the remaining devices by diverting energy from the remaining devices. If not, method 200 continues monitoring as shown in (204).

[0090] More specifically, in an embodiment, the controller 26 can activate the crowbar of the power converter 130 by selecting a crowbar response from a plurality of crowbar responses based on the location of the fault in one or more devices and activating the selected crowbar response. Thus, using the crowbar will generate an immediate transient that will rapidly activate protective devices (e.g., fuses or protective switching devices) before causing further damage to the bridging circuitry.

[0091] Now for reference Figure 7 This illustrates a flowchart of another embodiment of a method 300 for operating an electric power system according to the present disclosure. Generally, method 300 will be referred to herein. Figure 1 to Figure 5 The wind turbine 10, electric power system 100, and controller 26 shown are described herein. However, it should be understood that the disclosed method 300 can be implemented with wind turbines and power systems (such as, for example, solar power systems, energy storage power systems, or combinations thereof) having any other suitable configuration.

[0092] Furthermore, although for the purposes of explanation and discussion, Figure 7 The steps are described in a specific order, but the methods discussed herein are not limited to any particular order or arrangement. Using the disclosure provided herein, those skilled in the art will understand that the various steps of the methods disclosed herein can be omitted, rearranged, combined, and / or modified in various ways without departing from the scope of this disclosure.

[0093] As shown in (302), method 300 includes connecting a plurality of phases of power converter 130 to a common terminal on the DC side of power converter 130. As shown in (304), method 300 includes monitoring one or more parameters of a plurality of devices of power converter 130 via controller 26. For example, in such an embodiment, the parameters may include at least one of current, voltage, desaturation event, or combinations thereof. As shown in (306), method 300 includes determining whether the parameters indicate a fault has occurred in one or more of the plurality of devices. If so, as shown in (308), method 300 includes activating one or more protection devices of the power converter 130 via controller 26 to prevent further faults in the remaining devices of the plurality of devices by diverting energy away from the remaining devices.

[0094] Various aspects and embodiments of the present invention are defined by the following numbered clauses:

[0095] Clause 1. A method for operating a multi-stage bridge power converter in an electrical power system, the power converter including a rotor-side converter connected to a line-side converter via a DC link, the method comprising:

[0096] Connect multiple phases of the power converter to a common terminal on the DC side of the power converter so as to effectively make the multiple phases equal under a common potential;

[0097] Fault monitoring of multiple devices in the power converter is performed via the controller; and

[0098] When a fault is detected in one or more of the multiple devices, one or more protective devices of the power converter are activated via the controller to prevent further faults in the remaining devices by diverting energy away from the other devices.

[0099] Clause 2. The method according to Clause 1 further includes detecting the location of a fault in one or more of the plurality of devices via a controller.

[0100] Clause 3. The method according to any one of the preceding clauses, wherein activating the power converter's crowbar to prevent further malfunctions of multiple devices further includes:

[0101] Select a crowbar response from multiple crowbar responses based on the location of a fault in one or more of multiple devices; and

[0102] Activate the selected crowbar response.

[0103] Clause 4. The method according to any one of the preceding clauses, wherein the fault includes a bridging fault on the bridging circuit of the power converter.

[0104] Clause 5. The method according to any one of the preceding clauses, wherein one or more protection devices include at least one of a fuse, a switching element, or a combination thereof.

[0105] Clause 6. The method according to any one of the preceding clauses, wherein one or more protection devices include one or more switching elements of at least one of a rotor-side converter or a line-side converter.

[0106] Clause 7. The method according to any one of the preceding clauses, wherein one or more protection devices include one or more switching elements disposed upstream or downstream of at least one of the rotor-side converters or line-side converters.

[0107] Clause 8. The method according to any one of the preceding clauses, wherein the plurality of devices includes one or more semiconductor switches.

[0108] Clause 9. The method according to any one of the preceding clauses, wherein the electric power system includes a wind turbine power system, a solar power system, an energy storage power system, or a combination thereof.

[0109] Clause 10. An electric power system comprising:

[0110] A doubly-fed induction generator has a rotor and a stator, with the stator supplying AC power to the stator bus.

[0111] A multi-stage bridge power converter, connected to the rotor of a doubly-fed induction generator, provides output to the line bus. The power converter includes a rotor-side converter, a line-side converter, a DC link, and multiple phases connected to a common terminal on the DC side of the power converter to effectively equalize the phases under a common potential.

[0112] A controller, communicatively coupled to the power converter, is configured to perform a plurality of operations, including:

[0113] Fault monitoring of multiple devices in a power converter; and

[0114] When a fault is detected in one or more of the multiple devices, one or more protective devices of the power converter are activated via the controller to prevent further faults in the remaining devices by diverting energy away from the other devices.

[0115] Clause 11. The electrical power system according to Clause 10 further includes detecting the location of a fault in one or more of the plurality of devices via a controller.

[0116] Clause 12. The electrical power system according to Clause 11, wherein activating the power converter's crowbar to prevent further malfunctions of multiple devices further includes:

[0117] Select a crowbar response from multiple crowbar responses based on the location of a fault in one or more of multiple devices; and

[0118] Activate the selected crowbar response.

[0119] Clause 13. The electrical power system as described in Clauses 10 to 12, wherein the fault includes a bridging fault on the bridging circuit of the power converter.

[0120] Clause 14. The electrical power system described in Clauses 10 to 13, wherein one or more protective devices include fuses or switching elements.

[0121] Clause 15. The electrical power system according to Clauses 10 to 14, wherein one or more protection devices include a switching element of at least one of a rotor-side converter or a line-side converter.

[0122] Clause 16. The electric power system according to Clauses 10 to 15, wherein one or more protection devices include a switching element disposed upstream of the rotor-side converter within the power converter.

[0123] Clause 17. The electric power system described in Clauses 10 to 16, wherein the electric power system includes a wind turbine power system, a solar power system, an energy storage power system, or a combination thereof.

[0124] Clause 18. A method for operating a multi-stage bridge power converter in an electrical power system, the power converter including a rotor-side converter connected via a DC link to a line-side converter, the method comprising:

[0125] Connect multiple phases of the power converter to a common terminal on the DC side of the power converter;

[0126] The controller monitors one or more parameters of multiple devices in the power converter; and

[0127] When one or more parameters indicate a fault in one or more of the multiple devices, one or more protective devices of the power converter are activated via the controller to prevent further faults in the remaining devices by diverting energy away from the other devices.

[0128] Clause 19. The method according to Clause 18, wherein one or more parameters include at least one of current, voltage, desaturation event, or a combination thereof.

[0129] Clause 20. The method according to Clauses 18 to 19 further includes detecting the location of a fault in one or more of the plurality of devices via a controller, wherein activating a crowbar of the power converter to prevent further faults in the plurality of devices further includes selecting a crowbar response from a plurality of crowbar responses based on the location of the fault in one or more of the plurality of devices and activating the selected crowbar response.

[0130] This written description uses examples to disclose the invention (including the best mode) and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any incorporated methods. The patentability of the invention is defined by the claims and may include other examples that would occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A method for operating a multi-level bridge power converter of an electric power system, the power converter comprising a rotor-side converter coupled to a line-side converter via a DC link, the method comprising: connecting a plurality of phases of the power converter to a common terminal at a DC side of the power converter so as to effectively equalize the plurality of phases at a common potential; fault monitoring, via a controller, a plurality of devices of the power converter; and upon detecting a fault in one or more of the plurality of devices of the power converter, activating, via the controller, one or more protection devices provided in the power converter to prevent additional faults in remaining devices of the plurality of devices of the power converter by diverting energy away from the remaining devices of the plurality of devices of the power converter; wherein the method further comprises detecting, via the controller, a location of the fault in one or more of the plurality of devices of the power converter; and wherein activating the crowbar of the power converter to prevent additional faults of the plurality of devices of the power converter further comprises: selecting a crowbar response from a plurality of crowbar responses based on the location of the fault in one or more of the plurality of devices of the power converter; and activating the selected crowbar response.

2. The method of claim 1, wherein, the fault comprises a bridge fault on a bridge circuit of the power converter.

3. The method of claim 1, wherein, the one or more protection devices comprise at least one of a fuse, a switching element, or a combination thereof.

4. The method of claim 1, wherein, the one or more protection devices comprise one or more switching elements of at least one of the rotor-side converter or the line-side converter.

5. The method of claim 1, wherein, the one or more protection devices comprise one or more switching elements disposed upstream or downstream of at least one of the rotor-side converter or the line-side converter.

6. The method of claim 1, wherein, the plurality of devices comprise one or more semiconductor switches.

7. The method of claim 1, wherein, the electric power system comprises a wind turbine power system, a solar power system, an energy storage power system, or a combination thereof.

8. An electric power system comprising: a doubly-fed induction generator having a rotor and a stator, the stator providing AC power to a stator bus; a multi-level bridge power converter coupled to the rotor of the doubly-fed induction generator, the power converter providing an output to a line bus, the power converter comprising a rotor-side converter, a line-side converter, a DC link, and a plurality of phases connected to a common terminal at a DC side of the power converter so as to effectively equalize the plurality of phases at a common potential; and a controller communicatively coupled to the power converter, the controller configured to perform a plurality of operations, the plurality of operations comprising: fault monitoring a plurality of devices of the power converter; and upon detecting a fault in one or more of the plurality of devices of the power converter, activating, via the controller, one or more protection devices provided in the crowbar of the power converter to prevent additional faults in the remaining devices of the plurality of devices of the power converter by diverting energy away from the remaining devices of the plurality of devices of the power converter; wherein the plurality of operations further comprise detecting, via the controller, a location of the fault in the one or more of the plurality of devices of the power converter; and wherein activating the crowbar of the power converter to prevent additional faults of the plurality of devices of the power converter further comprises: selecting a crowbar response from a plurality of crowbar responses based on the location of the fault in the one or more of the plurality of devices of the power converter; and activating the selected crowbar response.

9. The electric power system of claim 8, wherein, the fault comprises a bridge fault on a bridge circuit of the power converter.

10. The electric power system of claim 8, wherein, the one or more protection devices comprise a fuse or a switching element.

11. The electric power system of claim 8, wherein, the one or more protection devices comprise a switching element of at least one of the rotor-side converter or the line-side converter.

12. The electric power system of claim 8, wherein, the one or more protection devices comprise a switching element disposed upstream of the rotor-side converter within the power converter.

13. The electric power system of claim 8, wherein, the electrical power system comprises a wind turbine power system, a solar power system, an energy storage power system, or a combination thereof.

14. A method for operating a multi-level bridge power converter of an electrical power system, the power converter comprising a rotor-side converter coupled to a line-side converter via a DC link, the method comprising: connecting a plurality of phases of the power converter to a common terminal at a DC side of the power converter; monitoring, via a controller, one or more parameters of a plurality of devices of the power converter; and upon detecting that the one or more parameters indicate a fault occurred in one or more of the plurality of devices of the power converter, activating, via the controller, one or more protection devices provided in the crowbar of the power converter to prevent additional faults in the remaining devices of the plurality of devices of the power converter by diverting energy away from the remaining devices of the plurality of devices of the power converter; wherein the method further comprises detecting, via the controller, a location of the fault in the one or more of the plurality of devices of the power converter, wherein activating the crowbar of the power converter to prevent additional faults of the plurality of devices of the power converter further comprises selecting a crowbar response from a plurality of crowbar responses based on the location of the fault in the one or more of the plurality of devices of the power converter and activating the selected crowbar response.

15. The method of claim 14, wherein, the one or more parameters comprise at least one of a current, a voltage, a desaturation event, or a combination thereof.

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