System and method for providing black start service from inverter-based resources

Abstract

A method of black-starting a power plant includes sending a black-start command to one or more first inverter-based resources having energy storage on an isolated first feed line at the power plant. Thus, the method includes implementing a black start mode using the first inverter-based resource (s) having energy storage, which includes establishing an auxiliary voltage and an auxiliary frequency to one or more auxiliary loads thereof using a first converter having the first inverter-based resource (s) having energy storage, and establishing a first voltage and a first frequency to the isolated first feeder using a second converter having energy storage first inverter-based resource (s). The method further includes exciting one or more first inverter-based resources without black start capability via an isolated first feed line, switching from a black start mode to a normal mode, and connecting the power plant to the power grid.

Description

Technical Field

[0001] This disclosure relates generally to wind turbines, and more specifically to systems and methods for providing blackstart services from inverter-based resources. Background Technology

[0002] Wind energy is considered one of the cleanest and most environmentally friendly energy sources available today, and wind turbines have gained increasing attention in this area. Modern wind turbines typically consist of a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture the kinetic energy of the wind using known airfoil principles. For example, rotor blades typically have an airfoil cross-sectional profile, causing airflow over the blades during operation to create a pressure difference between the two sides. Therefore, lift acts on the blades from the pressure side towards the suction side. This lift generates torque on the main rotor shaft, which is typically meshed with a generator used to produce electricity.

[0003] Wind turbines can be classified into two types: constant-speed and variable-speed turbines. Traditionally, variable-speed wind turbines are controlled as current sources connected to the power grid. In other words, variable-speed wind turbines rely on the grid frequency detected by a phase-locked loop (PLL) as a reference and inject a specified amount of current into the grid. Traditional current source control of wind turbines is based on the assumption that the grid voltage waveform is a fundamental voltage waveform with a fixed frequency and amplitude, and that wind penetration into the grid is low enough not to interfere with the grid voltage amplitude and frequency. Therefore, the wind turbine simply injects a specified current into the grid based on the fundamental voltage waveform. However, with the rapid growth of wind energy, wind energy penetration into some grids has increased to the point where wind turbine generators have a significant impact on grid voltage and frequency. When a wind turbine is located in a weak grid, wind turbine power fluctuations can lead to increased variations in the amplitude and frequency of grid voltage.

[0004] Furthermore, many existing renewable energy converters, such as doubly-fed wind turbines, operate in "grid-tracking" mode. Grid-tracking devices utilize fast current regulation loops to control the active and reactive power exchanged with the grid. More specifically, Figure 1The diagram illustrates the basic components of the main circuit and converter control structure of a grid-tracking doubly-fed induction generator (DFIG) wind turbine. As shown, the active power reference to the converter is generated by an energy source regulator (e.g., the turbine control section of the wind turbine). This is expressed as a torque reference, representing the smaller of the maximum available power from the energy source at that moment, or a reduction command from a higher-level grid controller. The converter control then determines the current reference for the active component of the current to achieve the desired torque. Therefore, the DFIG wind turbine includes functions that manage voltage and reactive power in a manner that generates commands for the reactive component of the current. A wide-bandwidth current regulator then generates a command for the voltage applied to the system by the converter, ensuring that the actual current closely tracks the command.

[0005] Alternatively, grid-forming converters provide voltage source characteristics, where the angle and amplitude of the voltage are controlled to achieve the regulation functions required by the grid. With this structure, current will flow according to the grid's demand, while the converter helps establish voltage and frequency for the grid. This characteristic is comparable to that of conventional generators based on turbine-driven synchronous machines. Therefore, grid-forming sources must include the following basic functions: (1) support grid voltage and frequency for any current within the device's rating, whether active or reactive; (2) prevent operation beyond the device's voltage or current capabilities by allowing changes in grid voltage or frequency rather than disconnecting the device (disconnection is only allowed when the voltage or frequency exceeds the limits established by the grid entity); (3) maintain stability for any grid configuration or load characteristics, including serving isolated loads or connected to other grid-forming sources, and switching between these configurations; (4) share the total load of the grid among other grid-forming sources connected to the grid; (5) traverse grid disturbances, whether major or minor; and (6) meet requirements (1)-(5) without requiring rapid communication with other control systems present in the grid or externally generated logic signals related to changes in grid configuration.

[0006] In the early 1990s, basic control structures for achieving the aforementioned grid formation goals were developed and field-verified for battery systems (see, for example, U.S. Patent No. 5,798,633, entitled "Battery Energy Storage Power Conditioning System"). Applications of all-converter wind turbines and solar generators are disclosed in U.S. Patent Publication No. 2010 / 0142237, entitled "System and Method for Control of a GridConnected Power Generating System," and U.S. Patent No. 9,270,194, entitled "Controller for controlling a power converter." However, this implementation has already been adopted in all-converter wind turbines.

[0007] The black-start capability of traditional generators is a crucial element for grid restoration after a power outage. Existing wind farms require operating grid voltage or other external AC power sources to operate auxiliary loads and start. Other types of generators, such as traditional thermal or gas turbine generators, have historically been used to black-start the grid during power outages. With inverter-based resources replacing many synchronous generators in the grid, there is a demand for grid resources that provide a black-start capability similar to that of traditional generators. Grid formation using inverter-based resources may enable black-start capabilities.

[0008] In view of the foregoing, this disclosure relates to systems and methods for providing black-start services from inverter-based resources (such as wind turbines). Summary of the Invention

[0009] Aspects and advantages of the invention will be set forth in part in the description which follows, or may be apparent from the description, or may be learned by practice of the invention.

[0010] In one aspect, this disclosure relates to a method for black-starting a power plant. The method includes, as the power plant disconnects from the power grid, sending a black-start command via a controller to one or more first inverter-based resources on an isolated first feeder at the power plant, the one or more first inverter-based resources having energy storage. Upon receiving the black-start command, the method includes implementing a black-start mode using the one or more first inverter-based resources with energy storage. Implementing the black-start mode includes establishing an auxiliary voltage and auxiliary frequency to one or more auxiliary loads using a first converter of the one or more first inverter-based resources with energy storage, and establishing a first voltage and a first frequency to the isolated first feeder using a second converter of the one or more first inverter-based resources with energy storage. The method also includes energizing one or more first inverter-based resources without black-start capability via the isolated first feeder. Furthermore, the method includes switching from the black-start mode to a normal mode. Additionally, the method includes connecting the power plant to the power grid to support black-start or recovery of a portion of the power grid.

[0011] In another aspect, this disclosure relates to a wind farm. The wind farm includes a plurality of wind turbines capable of being connected to a power grid via a transmission network and a controller having at least one processor. The processor(s) are configured to perform a plurality of operations, including: sending a black-start command to one or more first wind turbines on an isolated first feeder at the wind farm as the wind farm disconnects from the power grid, the one or more first wind turbines having energy storage; upon receiving the black-start command, implementing a black-start mode using the one or more first wind turbines having energy storage to establish voltage and frequency on the isolated first feeder, wherein implementing the black-start mode includes establishing auxiliary voltage and auxiliary frequency to one or more auxiliary loads using a first converter of one or more first inverter-based resources having energy storage, and establishing a first voltage and first frequency to the isolated first feeder using a second converter of one or more first inverter-based resources having energy storage; energizing one or more first inverter-based resources without black-start capability via the isolated first feeder; switching from the black-start mode to a normal mode; and connecting the power farm to the power grid to support a portion of the power grid's black-start or recovery.

[0012] These and other features, aspects, and advantages of the invention will become more readily 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. Attached Figure Description

[0013] The present invention is a complete and implementable disclosure for those skilled in the art, including its best mode, as set forth in the specification with reference to the accompanying drawings, in which: Figure 1 A single-line diagram of a doubly fed wind turbine generator with converter control for grid tracking applications, constructed according to conventional methods, is shown. Figure 2 A perspective view of one embodiment of a wind turbine according to the present disclosure is shown; Figure 3 A simplified interior view of a cabin according to an embodiment of the present disclosure is shown; Figure 4 It shows suitable for supply Figure 1 A schematic diagram of one embodiment of the wind turbine power system used by the wind turbine shown in the illustration; Figure 5 A schematic diagram of one embodiment of a wind farm having multiple wind turbines according to the present disclosure is shown; Figure 6 A block diagram of one embodiment of a controller according to the present disclosure is shown; Figure 7 A single-line diagram of a doubly-fed wind turbine generator with converter control for grid-forming applications is shown according to this disclosure; Figure 8 A flowchart illustrating an embodiment of a method for black-starting a power plant connected to a power grid according to this disclosure is shown; Figure 9 A schematic diagram of an embodiment of a system for black-starting a power plant connected to a power grid according to the present disclosure is shown; Figure 10 A schematic diagram of an embodiment of a grid with energy storage forming a wind turbine according to the present disclosure is shown; and Figure 11 A schematic diagram of an embodiment of a control structure for a wind turbine with energy storage grid according to the present disclosure is shown. Detailed Implementation

[0014] Reference will now be made in detail to embodiments of the invention, one or more of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not as a limitation thereof. Indeed, it will be apparent to those skilled in the art that various modifications and alterations can be made to the invention without departing from the scope or spirit thereof. For example, features shown or described as part of one embodiment may be used with another embodiment to produce yet another embodiment. Therefore, the invention is intended to cover these modifications and alterations that fall within the scope of the appended claims and their equivalents.

[0015] Increased levels of renewable energy integration are associated with rising grid security costs. Therefore, emerging grid specifications require the provision of functionality traditionally provided by synchronous generators, based on inverter resources. One example of this functionality is enabling generation resources to provide black-start capability. In light of the foregoing, this disclosure relates to systems and methods for providing black-start capability for power plants connected to the power grid. For example, in embodiments, the method of this disclosure involves black-start wind turbines that do not rely on external AC power. Specifically, in embodiments, a first black-start wind turbine (or wind turbine assembly) with this capability is further used to start other wind turbines within the power plant, subsequently energizing portions of the external power grid to facilitate the black-start of the power grid.

[0016] Now refer to the attached diagram, Figure 2 A perspective view of one embodiment of a wind turbine 10 according to this disclosure is shown. As shown, the wind turbine 10 typically 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 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 from the wind to be converted into usable mechanical energy, and subsequently into electrical energy. For example, the hub 20 may be rotatably coupled to a generator 24 located within the nacelle 16. Figure 3 On top of that, so that electrical energy can be generated.

[0017] The wind turbine 10 may also include a wind turbine controller 26 centralized within the nacelle 16. However, in other embodiments, the controller 26 may be located within any other component of the wind turbine 10, or at a location external to the wind turbine 10. Furthermore, the controller 26 may be communicatively coupled to any number of components of the wind turbine 10 to control the operation of these components and / or to perform corrective or control actions. Thus, the controller 26 may include a computer or other suitable processing unit. Therefore, in several embodiments, the controller 26 may include suitable computer-readable instructions that, when implemented, configure the controller 26 to perform various functions, such as receiving, transmitting, and / or executing wind turbine control signals. Thus, the controller 26 may typically be configured to control various operating modes (e.g., start-up or shutdown sequences) to de-rating or up-rating the wind turbine and / or individual components of the wind turbine 10.

[0018] Now refer to Figure 2 , showed Figure 1The diagram shows a simplified internal view of one embodiment of the nacelle 16 of the wind turbine 10. As shown, a generator 24 may be housed within the nacelle 16 and supported on top of a base 46. Typically, the generator 24 may be coupled to a rotor 18 to generate electrical energy from the rotational energy produced by the rotor 18. For example, as shown in the illustrated embodiment, the rotor 18 may include a rotor shaft 34 coupled to a hub 20 for rotation therewith. The rotor shaft 34 is in turn rotatably coupled to a generator shaft 36 of the generator 24 via a gearbox 38. As generally understood, in response to rotation of the rotor blades 22 and the hub 20, the rotor shaft 34 may provide a low-speed, high-torque input to the gearbox 38. The gearbox 38 may then be configured to convert the low-speed, high-torque input into a high-speed, low-torque output to drive the generator shaft 36, and thus the generator 24.

[0019] The wind turbine 10 may also include one or more pitch drive mechanisms 32 communicatively connected to the wind turbine controller 26, wherein each pitch drive mechanism 32 is configured to rotate the pitch bearing 40, and thus rotate the individual rotor blade(s) 22 about their respective pitch axis 28. Furthermore, as shown, the wind turbine 10 may include one or more yaw drive mechanisms 42 configured to change the angle of the nacelle 16 relative to the wind (e.g., by engaging a yaw bearing 44 of the wind turbine 10, which is arranged between the nacelle 16 and the tower 12 of the wind turbine 10).

[0020] In addition, the wind turbine 10 may include one or more sensors 66, 68 for monitoring various wind conditions of the wind turbine 10. For example, the direction 52 of the incoming wind, wind speed, or any other suitable wind condition near the wind turbine 10 may be measured, for example, by using a suitable meteorological sensor 66. Suitable meteorological sensors may include, for example, light detection and ranging devices, acoustic detection and ranging devices, anemometers, wind vanes, barometers, radio detection and ranging devices, or any other sensing devices that can provide wind direction information now known or later developed in the art. As described herein, additional sensors 68 may be used to measure additional operating parameters of the wind turbine 10, such as voltage, current, vibration, etc.

[0021] Now refer to Figure 4 A schematic diagram of one embodiment of a wind turbine power system 100 is shown according to some aspects of this disclosure. Although reference will be made herein to Figure 4 The system 100 shown herein provides a general description of this disclosure; however, those skilled in the art who use the disclosure provided herein will understand that some aspects of this disclosure may also be applied to other power generation systems, and as stated above, the invention is not limited to wind turbine systems.

[0022] exist Figure 4In the embodiments and as described above, the rotor 18 of the wind turbine 10 ( Figure 2 The generator 102 can be optionally coupled to gearbox 38, which in turn is coupled to generator 102, which may be a doubly-fed induction generator (DFIG). As shown, generator 102 can be connected to stator bus 104. Furthermore, as shown, power converter 106 can be connected to generator 102 via rotor bus 108 and to stator bus 104 via line-side bus 110. Thus, stator bus 104 can provide multiphase output power (e.g., three-phase power) from the stator of generator 102, and rotor bus 108 can provide multiphase output power (e.g., three-phase power) from the rotor of generator 102. Power converter 106 may also include rotor-side converter (RSC) 112 and line-side converter (LSC) 114. Generator 102 is coupled to rotor-side converter 112 via rotor bus 108. Furthermore, RSC 112 is coupled to LSC 114 via DC link 116, with DC link capacitor 118 bridging DC link 116. LSC 114 is also coupled to line-side bus 110.

[0023] RSC 112 and LSC 114 may use one or more switching devices, such as insulated-gate bipolar transistor (IGBT) switching devices, configured for normal operating mode in a three-phase pulse width modulation (PWM) arrangement. Furthermore, power converter 106 may be coupled to converter controller 120 to control the operation of rotor-side converter 112 and / or line-side converter 114 as described herein. It should be noted that converter controller 120 may be configured to interface between power converter 106 and turbine controller 26 and may include any number of control devices.

[0024] In a typical configuration, various line contactors and circuit breakers may also be included, including, for example, grid circuit breaker 122, for isolating various components required for the normal operation of generator 102 during connection to and disconnection from a load (such as power grid 124). For example, system circuit breaker 126 may couple system bus 128 to transformer 130, which may be coupled to power grid 124 via grid circuit breaker 122. In alternative embodiments, fuses may replace some or all of the circuit breakers.

[0025] In operation, the AC power generated at generator 102 by rotating rotor 18 is supplied to power grid 124 via a dual path defined by stator bus 104 and rotor bus 108. On rotor bus side 108, sinusoidal multiphase (e.g., three-phase) alternating current (AC) power is supplied to power converter 106. Rotor-side converter 112 converts the AC power supplied from rotor bus 108 into direct current (DC) power and supplies the DC power to DC link 116. As is generally understood, the switching elements (e.g., IGBTs) used in the bridge circuit of rotor-side converter 112 can be modulated to convert the AC power supplied from rotor bus 108 into DC power suitable for DC link 116.

[0026] Furthermore, the line-side converter 114 converts the DC power on the DC link 116 into AC output power suitable for the power grid 124. Specifically, the switching elements (e.g., IGBTs) used in the bridge circuit of the line-side converter 114 can be modulated to convert the DC power on the DC link 116 into AC power on the line-side bus 110. The AC power from the power converter 106 can be combined with the power from the stator of the generator 102 to provide multiphase power (e.g., three-phase power) at a frequency substantially maintained at the frequency of the power grid 124 (e.g., 50 Hz or 60 Hz).

[0027] In addition, various circuit breakers and switches, such as grid circuit breaker 122, system circuit breaker 126, stator synchronizing switch 132, converter circuit breaker 134, and line contactor 136, may be included in the wind turbine power system 100 to connect or disconnect corresponding busbars, for example, in the event of excessive current that could damage components of the wind turbine power system 100, or for other operational considerations. Additional protection components may also be included in the wind turbine power system 100.

[0028] Furthermore, the power converter 106 can receive control signals from, for example, a local control system 176 via the converter controller 120. These control signals can be based on the sensed state or operating characteristics of the wind turbine power system 100. Typically, the control signals provide control over the operation of the power converter 106. For example, feedback in the form of sensed speed from the generator 102 can be used to control the conversion of output power from the rotor bus 108 to maintain a proper and balanced multiphase (e.g., three-phase) power supply. Other feedback from other sensors can also be used by controller(s) 120, 26 to control the power converter 106, 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.

[0029] The power converter 106 also compensates for or adjusts the frequency of the three-phase power from the rotor to accommodate variations in wind speed, such as at hub 20 and rotor blades 22. Therefore, the mechanical and electric rotor frequencies are decoupled, and the electric stator frequency is substantially independent of the mechanical rotor speed.

[0030] In some states, the bidirectional nature of power converter 106, and particularly the bidirectional nature of LSC 114 and RSC 112, helps to feed at least some of the generated electrical power back to the generator rotor. More specifically, electrical power can be transferred from stator bus 104 to line-side bus 110, and then via line contactor 136 to power converter 106, specifically to LSC 114, which acts as a rectifier and rectifies the sinusoidal three-phase AC power into DC power. The DC power is then transferred to DC link 116. Capacitor 118 helps mitigate DC link voltage amplitude variations by helping to reduce DC ripple sometimes associated with three-phase AC rectification.

[0031] The DC power is then transmitted to RSC 112, which converts the DC power into three-phase sinusoidal AC power by adjusting the voltage, current, and frequency. This conversion is monitored and controlled via converter controller 120. The converted AC power is transmitted from RSC 112 to the generator rotor via rotor bus 108. In this way, controlling the rotor current and voltage facilitates active and reactive power control or other controls of the generator.

[0032] Now for reference Figure 5 The wind turbine power system 100 described herein may be part of a wind farm 50. As shown, the wind farm 50 may include a plurality of wind turbines 52 (including the aforementioned wind turbine 10) and a total farm-level controller 56. For example, as shown in the illustrated embodiment, the wind farm 50 includes twelve wind turbines, including wind turbine 10. However, in other embodiments, the wind farm 50 may include any other number of wind turbines, such as fewer than twelve or more than twelve wind turbines. In one embodiment, the turbine controllers of the plurality of wind turbines 52 are communicatively coupled to the farm-level controller 56, for example, via a wired connection, such as by connecting turbine controller 26 via a suitable communication link 54 (e.g., a suitable cable). Alternatively, the turbine controllers may be communicatively coupled to the farm-level controller 56 via a wireless connection, such as by using any suitable wireless communication protocol known in the art. In a further embodiment, the field-level controller 56 is configured to send and receive control signals to and from various wind turbines 52, such as assigning active and / or reactive power demands or voltage reference commands across the wind turbines 52 of the wind farm 50.

[0033] Now refer to Figure 6This diagram illustrates a block diagram of one embodiment of suitable components that may be included within a controller (such as any of the converter controller 120, turbine controller 26, and / or field-level controller 56 described herein) according to exemplary aspects of this disclosure. As shown, the controller may include one or more processors 58, a computer or other suitable processing unit, and (one or more) associated memory devices 60 that may include suitable computer-readable instructions 60, which, when implemented, configure the controller to perform various functions, such as receiving, transmitting, and / or performing wind turbine control signals (e.g., performing the methods, steps, calculations, etc. disclosed herein).

[0034] As used herein, the term "processor" refers not only to an integrated circuit known in the art as included in a computer, but also to a controller, microcontroller, microcomputer, programmable logic controller (PLC), application-specific integrated circuit (ASIC), and other programmable circuits. Furthermore, memory device(s) 60 typically includes memory elements(s), 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, optical disc read-only memory (CD-ROM), magneto-optical disc (MOD), digital versatile disc (DVD), and / or other suitable memory elements.

[0035] One or more of these memory devices 60 may typically be configured to store suitable computer-readable instructions that, when implemented by one or more processors 58, configure the controller to perform the various functions described herein. Furthermore, the controller may include a communication interface 62 to facilitate communication between the controller and various components of the wind turbine 10. The interface may include one or more circuits, terminals, pins, contacts, conductors, or other components for sending and receiving control signals. Additionally, the controller may include a sensor interface 64 (e.g., one or more analog-to-digital converters) to allow signals transmitted from sensors 66, 68 to be converted into signals that can be understood and processed by one or more processors 58.

[0036] Now for reference Figure 7 A schematic diagram of an embodiment of a grid-forming power system 200 according to the present disclosure is shown, with a particular single-line diagram of a generator 102 having an advanced control structure for grid-forming characteristics. Specifically, as shown, the grid-forming power system 200 may include many of the features described herein. Figure 4 The components share the same features, with components having the same reference numerals representing similar components. Furthermore, as shown, the power grid forming system 200 may include a control structure for controlling line-side converters, which is similar to... Figure 1The control structure is shown. More specifically, as shown, the line-side converter control structure may include a DC regulator 212 and a line current regulator 214. The DC regulator 212 is configured to generate a line-side current command for the line current regulator 214. The line current regulator 214, in turn, generates a line-side voltage command for the modulator 218. The modulator 218 also receives an output (e.g., a phase-locked loop angle) from a phase-locked loop 216 to generate one or more gate pulses for the line-side converter 114. The phase-locked loop 216 typically uses a voltage feedback signal to generate its output.

[0037] Furthermore, as shown in the figure, the grid-forming power system 200 may also include a unique control structure for controlling the rotor-side converter 112 using grid-forming characteristics. Specifically, as Figure 7 As shown, the grid-forming power system 200 may include a stator voltage regulator 206 for providing such grid-forming characteristics. Furthermore, as shown, the grid-forming power system 200 may include a grid voltage / VAR regulator 202, an inertial power regulator 204, a rotor current regulator 208, and a modulator 210.

[0038] More specifically, as will be explained, the grid-forming power system 200 includes an inner-loop current regulator structure and a fast stator voltage regulator to translate voltage commands from grid-forming control into rotor current regulator commands. Therefore, the systems and methods of this disclosure provide control over the rotor voltage of generator 102 to meet higher-level commands regarding the amplitude and angle of the stator voltage. This control must be relatively fast and insensitive to the current flowing in the stator of generator 102.

[0039] Now for reference Figure 8 and Figure 9 This disclosure relates to a method 250 and a system 300 for black-starting a power plant (e.g., a wind farm 50) connected to a power grid according to this disclosure. Specifically, Figure 8 A flowchart illustrating an embodiment of a method 250 for black-starting a power plant (e.g., wind farm 50) connected to a power grid according to this disclosure is shown, while Figure 9 A schematic diagram of an embodiment of a system 300 for black-starting a power plant (e.g., wind farm 50) connected to a power grid according to this disclosure is shown. Generally, reference is made herein to... Figure 2-7 Method 250 and system 300 are described using wind turbine 10 and wind farm 50. However, it should be understood that the disclosed method 250 and system 300 can be implemented using any inverter-based resources, in addition to wind turbines with any other suitable configuration. Furthermore, although... Figure 8The steps are described in a specific order for illustrative and discussion purposes, but the methods discussed herein are not limited to any particular order or arrangement. Those skilled in the art will appreciate, using the disclosure provided herein, that the steps of the methods disclosed herein can be omitted, rearranged, combined, and / or adapted in various ways without departing from the scope of this disclosure.

[0040] like Figure 8 As shown at (252) in the diagram, method 250 includes disconnecting the power plant (e.g., wind farm 50) from the power grid after a power outage. For example, in an embodiment, as... Figure 9 As shown, the wind farm 50 can be disconnected from the power grid by opening multiple switching devices 302 to multiple feeders 304 and main switching device 306 to transformer 308.

[0041] Furthermore, and return to the reference. Figure 8 Method 250 includes setting the inertial power regulator reference to zero, setting the frequency to a baseline frequency reference, and setting the voltage to a baseline voltage reference. In such an embodiment, the baseline voltage reference is less than or equal to the nominal voltage, and the baseline frequency reference is less than or equal to the nominal frequency.

[0042] As the power plant (e.g., wind farm 50) is disconnected from the power grid, as shown at (254), method 250 includes sending a black-start command via a controller to one or more first inverter-based resources (e.g., wind turbines) on an isolated first feeder at the power plant. In such an embodiment, the first inverter-based resources(s) have energy storage and grid-forming capabilities. For example, as shown... Figure 9 As shown, the wind farm 50 includes an isolated first feeder 310, which has one or more energy storage units 324. Figure 10 The grid-forming wind turbine 312 is shown in the figure, with only one shown for clarity. In embodiments, for example, the number of grid-forming wind turbines 312 with energy storage may depend on the auxiliary loads on the individual feeders and / or the first feeder 310.

[0043] Return to reference Figure 8 Upon receiving a black-start command, as shown at (256), method 250 includes implementing a black-start mode using one or more first inverter-based resources (e.g., grid-forming wind turbines 312) with energy storage. For example, upon receiving a black-start command, one or more grid-forming wind turbines 312 begin energizing the device in black-start mode.

[0044] More specifically, in embodiments, implementing a black-start mode may include establishing an auxiliary voltage and auxiliary frequency to one or more auxiliary loads using a first converter with one or more first inverter-based resources having energy storage, and establishing a first voltage and first frequency to an isolated first feeder using a second converter with one or more first inverter-based resources having energy storage, the first voltage following a baseline voltage reference and the first frequency following a baseline frequency reference. Furthermore, in embodiments, implementing a black-start mode may include ramping up the voltage of the energy storage(s) of the first inverter-based resource(s) to a first voltage reference having a first frequency reference at a predetermined rate. In such embodiments, the predetermined rate and the reduced voltage / frequency are configured to reduce transient and steady-state loading during black-start mode.

[0045] Furthermore, in the embodiments, such as Figure 10 As shown, ramping the voltage of one or more first inverter-based resources (e.g., one or more grid-forming wind turbines 312) with energy storage 324 to a first voltage reference with a first frequency reference at a predetermined rate may include using energy from the energy storage 324 of the grid-forming wind turbines 312 and / or at least one of the first converters 326 (e.g., RSC) to facilitate the black start of the wind farm 50. Furthermore, as Figure 10 As shown, ramping the voltage of one or more grid-forming wind turbines 312 to a first voltage reference having a first frequency reference at a predetermined rate may include supplying auxiliary power 330 through at least one of the energy storage 324 of the one or more grid-forming wind turbines 312 and / or one or more second converters 328 (e.g., LSCs). In such an embodiment, the auxiliary power 330 is configured to supply at least one of the following: auxiliary loads, cable charging, or losses of the one or more grid-forming wind turbines 312.

[0046] Therefore, in the embodiments, such as Figure 10 As shown, a black-start mode typically includes charging the DC bus 334 via energy storage 324 and enabling control card 332. Furthermore, as shown, a black-start mode typically includes closing and opening multiple switches (e.g., S1, S2, S3, S4, S5, and S6) according to the desired black-start mode. Additionally, a black-start mode typically includes operating LSC 328 or RSC 326 according to the desired black-start mode to provide auxiliary power 330 to the auxiliary load. Another converter (i.e., the converter not supplying the auxiliary load) is operating in black-start mode, where the black-start mode may also typically include using grid forming control and ramp voltage to energize transformer 336, collector cable, and / or one or more other units on the first feeder 310.

[0047] Furthermore, and still refer to Figure 10 Various dashed boxes indicate when multiple switches (e.g., S1, S2, S3, S4, S5, and S6) are opened and closed. Specifically, as shown, switches S1 and S2 are closed during normal mode and are closed if a black-start power grid for wind turbine 312 is formed from one or more power grids with energy storage 324 using RSC 326. Furthermore, as shown, switch S3 is closed during normal mode, is closed if only energy storage 324 and LSC 328 are used for black-start power grid operation, and is closed when auxiliary loads and DC bus 334 are energized during normal startup. Additionally, as shown, switch S4 is closed during normal mode, is closed if only energy storage 324 and one of the converters are used for black-start power grid operation, is closed when auxiliary loads and DC bus 334 are energized during normal startup, and is closed if a black-start power grid for wind turbine 312 is formed from one or more power grids with energy storage 324. Furthermore, as shown in the figure, switch S5 is closed during normal mode, when the auxiliary load and DC bus 334 are energized during normal startup, and if an RSC 326 black-start power grid for wind turbine 312 is formed from one or more power grids with energy storage 324. Additionally, as shown in the figure, switch S6 is closed if only energy storage 324 and the LSC 328 black-start power grid are used.

[0048] Return to reference Figure 8 As shown at (258), method 250 includes energizing one or more first inverter-based resources that do not have black-start capability via an isolated first feeder. For example, as Figure 9 As shown, wind farm 50 includes one or more wind turbines 314 without black-start capability on an isolated first feeder 310. Therefore, after one or more grid-forming wind turbines 312 are energized, the grid-forming wind turbines 312 begin energizing the one or more wind turbines 314 without black-start capability on the isolated first feeder 310. In another embodiment, as indicated by dashed box 322, the one or more wind turbines 314 without black-start capability on the isolated first feeder 310 may be designed with medium-voltage (MV) switchgear and / or auxiliary load isolation to reduce load during black-start of the one or more wind turbines 314. In some embodiments, the one or more wind turbines 314 without black-start capability on the isolated first feeder 310 may be one or more grid-tracking wind turbines or one or more grid-forming wind turbines.

[0049] Return to reference Figure 8As shown at (260), method 250 includes a first feed line for excitation isolation. For example, in an embodiment, as... Figure 9 As shown, the first feed 310 for energizing isolation may include closing one or more switching devices (e.g., switching device 302) to energize the collector bus 316 of the first feed 310 for energizing isolation.

[0050] Return to reference Figure 8 As shown at (262), method 250 includes energizing one or more second feeders having one or more second inverter-based resources via an isolated first feeder. For example, as Figure 9 As shown, once the first feeder 310 is energized, the switching devices 302 of one or more second feeders 318 can be closed, and the first feeder 310 can be used to energize the second feeder 318, which has, for example, multiple second wind turbines 320 without black-start capability. Therefore, cables, gaskets, etc., mounted on the second feeder 318 can be energized via the first feeder 310.

[0051] Therefore, and return to the reference. Figure 8 As shown at (264), method 250 includes sequentially starting one or more second inverter-based resources, such as a plurality of second wind turbines 320. For example, in an embodiment, the plurality of second wind turbines 320 may not have black-start capability. Therefore, in an embodiment, sequentially starting the second inverter-based resources(s) may include sequentially starting the second inverter-based resources that do not have black-start capability.

[0052] Furthermore, in embodiments, this step can be repeated for any number of feeders as needed. As shown at (266), method 250 includes switching from a black-start mode to a normal mode. For example, in embodiments, switching from a black-start mode to a normal mode may include sending a signal to one or more grid-forming wind turbines 312 to operate in normal mode. Specifically, as Figure 10 As shown, transitioning from black-start mode to normal mode may include synchronizing the temporary auxiliary supply with the grid voltage and closing necessary switches (e.g., any one of S1, S2, S3, S4, S5, and S6) to operate the auxiliary load from external AC supply (not shown) and / or from power generated by the wind turbine 312 formed by the grid(s). Furthermore, in an embodiment, transitioning from black-start mode to normal mode may include disconnecting (if necessary) the temporary connection from RSC 326 or LSC 328 to the auxiliary load and switching the control of RSC 326 or LSC 328 previously supplying auxiliary power to normal control mode.

[0053] In addition, after switching to normal mode, such as Figure 8As shown at (268), method 250 may include adding a first voltage reference and a first frequency reference to a second voltage reference and a second frequency reference, respectively. Furthermore, in an embodiment, as shown at (270), method 250 includes energizing the power plant before connecting it to the power grid. Additionally, as shown at (272), method 250 includes connecting the power plant, such as wind farm 50, to the power grid to support black start or recovery of a portion of the power grid.

[0054] Now refer to Figure 11 A schematic diagram of an embodiment of a control structure 400 for a grid-forming wind turbine 312 with energy storage 324 is shown. Specifically, as shown, converter control 402 utilizes GFM control for normal operation and black-start operation. Furthermore, simple voltage / frequency control can be used to temporarily control one of the bridges during black-start mode to supply auxiliary loads. The desired operating mode 406 determines which control drives which bridge voltage. The desired operating mode can be determined based on available wind power at the turbine, the charge state of the energy storage, or a combination of both.

[0055] Furthermore, in this embodiment, black start can be achieved using only LSC 328 (where RSC 326 feeds the auxiliary load). Additionally, the mains voltage / VAR regulator 408 and the inertial power regulator 410 drive the LSC 328 with a voltage command 412 along with a PLL angle 414 (e.g., θ). PLL Therefore, in this embodiment, LSC 328 is operating as a grid forming converter to black-start the first feeder. Furthermore, as shown, auxiliary voltage control 416 uses a nominal frequency / angle signal 420 (e.g., θ). nom Drive voltage command 418. Additionally, as shown, battery control 422 regulates the DC voltage of DC link 424.

[0056] In another embodiment, black start can be achieved using only RSC 326 (where LSC 328 powers the auxiliary load). In such an embodiment, the grid voltage / VAR regulator 408 and the inertial power regulator 410 drive the voltage command 418 of RSC 326 along with the PLL angle 414 (e.g., θ) via the stator voltage regulator 426 and the rotor current regulator 428. PLL ) and rotor position feedback 430 (e.g., θ) rfbk Therefore, in this embodiment, RSC 328 facilitates the grid formation function required for black start. Furthermore, as shown, auxiliary voltage control 416 drives voltage command 412 along with a nominal frequency / angle signal 420 (e.g., θ). nomFurthermore, the battery control 422 regulates the DC voltage of the DC link 424. Additionally, in such an embodiment, turbine pitch control (not shown) regulates the rotor speed.

[0057] Other aspects of the invention are provided by the subject matter of the following provisions: A method for black-starting a power plant, the method comprising: as the power plant is disconnected from a power grid, sending a black-start command via a controller to one or more first inverter-based resources on an isolated first feeder at the power plant, the one or more first inverter-based resources having energy storage; upon receiving the black-start command, implementing a black-start mode using the one or more first inverter-based resources having the energy storage, wherein implementing the black-start mode includes establishing an auxiliary voltage and auxiliary frequency to one or more auxiliary loads using a first converter of the one or more first inverter-based resources having the energy storage, and establishing a first voltage and a first frequency to the isolated first feeder using a second converter of the one or more first inverter-based resources having the energy storage; energizing one or more first inverter-based resources without black-start capability via the isolated first feeder; switching from the black-start mode to a normal mode; and connecting the power plant to the power grid to support a portion of the power grid's black-start or recovery.

[0058] The method according to any of the foregoing provisions further includes: energizing one or more second feeders having one or more second inverter-based resources via the isolated first feeder; and sequentially activating the one or more second inverter-based resources.

[0059] According to any of the foregoing provisions, wherein the one or more second inverter-based resources do not have black-start capability, and wherein sequentially starting the one or more second inverter-based resources further includes sequentially starting the one or more second inverter-based resources that do not have black-start capability.

[0060] The method according to any of the foregoing provisions further includes: disconnecting the power plant from the power grid before sending the black start command.

[0061] According to any of the foregoing provisions, disconnecting the power plant from the power grid further includes: turning on multiple switching devices of the power plant to multiple feeders and the main switching device to the transformer.

[0062] The method according to any of the foregoing clauses further includes: setting the inertial power regulator reference to zero, setting the first frequency to a baseline frequency reference, and setting the first voltage to a baseline voltage reference before sending the black start command, wherein the baseline voltage reference is less than or equal to the nominal voltage, and the baseline frequency reference is less than or equal to the nominal frequency.

[0063] According to any of the foregoing provisions, implementing the black-start mode using the resources of the one or more first inverters having the energy storage further includes: ramping up a first voltage of the resources of the one or more first inverters having the energy storage to a first voltage reference having a first frequency reference at a predetermined rate, wherein the predetermined rate and the reduced voltage / frequency reduce transient and steady-state loading during the black-start mode.

[0064] The method according to any of the foregoing clauses further includes: adding the first voltage reference and the first frequency reference to the second voltage reference and the second frequency reference, respectively.

[0065] According to any of the foregoing provisions, the auxiliary power supply is at least one of the following: auxiliary load, cable charging, or loss of the one or more first inverter-based resources.

[0066] According to any of the foregoing provisions, the method of switching from the black-start mode to the normal mode further includes: sending a signal to the one or more first inverter-based resources at the power plant that have the energy storage to operate in the normal mode.

[0067] The method according to any of the foregoing provisions further includes: energizing the power plant before connecting the power plant to the power grid.

[0068] According to any of the foregoing provisions, wherein the one or more first inverter-based resources and the one or more second inverter-based resources comprise a plurality of wind turbines, wherein at least the one or more first inverter-based resources have grid-forming capability.

[0069] According to any of the foregoing provisions, implementing the black-start mode further includes: operating the first converter such that the auxiliary voltage and the auxiliary frequency are independent of the first voltage and the first frequency established by the second converter.

[0070] According to any of the foregoing provisions, the one or more first inverter-based resources having the energy storage are one of a doubly-fed induction generator or a full-power conversion system, and the first converter is at least one of a machine-side converter or a grid-side converter.

[0071] According to any of the foregoing provisions, the method of switching from the black-start mode to the normal mode further includes: connecting the one or more auxiliary loads to the isolated first feeder, thereby supplying the one or more auxiliary loads with power from the first feeder.

[0072] A wind farm includes: a plurality of wind turbines capable of being connected to a power grid via a transmission network; and a controller including at least one processor configured to perform a plurality of operations, the plurality of operations including: sending a black-start command to one or more first wind turbines having energy storage on an isolated first feeder at the wind farm as the wind farm disconnects from the power grid; upon receiving the black-start command, implementing a black-start mode using the one or more wind turbines having the energy storage to establish voltage and frequency on the isolated first feeder, wherein implementing the black-start mode includes establishing auxiliary voltage and auxiliary frequency to one or more auxiliary loads using a first converter of the one or more first inverter-based resources having the energy storage, and establishing a first voltage and first frequency to the isolated first feeder using a second converter of the one or more first inverter-based resources having the energy storage; energizing one or more first inverter-based resources without black-start capability via the isolated first feeder; switching from the black-start mode to a normal mode; and connecting the wind farm to the power grid to support partial black-start or recovery of the power grid. According to any of the foregoing provisions, the plurality of operations further include: energizing one or more second feeders having one or more second wind turbines without black start capability via the isolated first feeder; and sequentially starting the one or more second wind turbines without black start capability.

[0073] According to any of the foregoing provisions, the multiple operations further include: disconnecting the wind farm from the power grid before sending the black start command, wherein disconnecting the wind farm from the power grid further includes turning on multiple switching devices of the wind farm to multiple feeders and the main switching device to the transformer.

[0074] According to any of the foregoing provisions, the plurality of operations further include: setting the inertial power regulator reference to zero, setting the first frequency to a baseline frequency reference, and setting the first voltage to a baseline voltage reference before sending a black start command, wherein the baseline voltage reference is less than or equal to the nominal voltage, and the baseline frequency reference is less than or equal to the nominal frequency.

[0075] 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 combined methods. The patentable scope of the invention is defined by the claims, but may include other examples that would occur to a person skilled in the art. These other examples are intended to be within the scope of the claims if they comprise structural elements that are not different from the literal language of the claims, or if they comprise equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A method for a black-start power generation plant, the method comprising: As the power plant disconnects from the power grid, a black start command is sent via the controller to one or more first inverter-based resources on an isolated first feeder at the power plant, the one or more first inverter-based resources having energy storage. Upon receiving the black start command, a black start mode is implemented using the resources of the one or more first inverters having the energy storage, wherein implementing the black start mode includes establishing an auxiliary voltage and auxiliary frequency to one or more auxiliary loads using a first converter having the resources of the one or more first inverters having the energy storage, and establishing a first voltage and a first frequency to the isolated first feeder using a second converter having the resources of the one or more first inverters having the energy storage. One or more first inverter-based resources without black-start capability are activated via the isolated first feeder; Switch from the black boot mode to normal mode; as well as The power plant is connected to the power grid to support black start or recovery of a portion of the power grid.

2. The method according to claim 1, further comprising: One or more second feeders having one or more second inverter-based resources are energized via the isolated first feeder; as well as The one or more second inverter-based resources are started sequentially.

3. The method according to claim 2, wherein, The one or more second inverter-based resources do not have black start capability, and sequentially starting the one or more second inverter-based resources also includes sequentially starting the one or more second inverter-based resources that do not have black start capability.

4. The method according to claim 1, further comprising: Before sending the black start command, disconnect the power plant from the power grid.

5. The method according to claim 4, wherein, Disconnecting the power plant from the power grid also includes: Open the multiple switching devices of the power plant to the multiple feeders and the main switching device to the transformer.

6. The method according to claim 1, further comprising: Before sending the black start command, the inertial power regulator reference is set to zero, the first frequency is set to the baseline frequency reference, and the first voltage is set to the baseline voltage reference, wherein the baseline voltage reference is less than or equal to the nominal voltage, and the baseline frequency reference is less than or equal to the nominal frequency.

7. The method according to claim 1, wherein, Implementing the black-start mode using the resources of the one or more first inverters having the energy storage also includes: The first voltage of the one or more first inverter-based resources having the energy storage is ramped up at a predetermined rate to a first voltage reference having a first frequency reference, wherein the predetermined rate and the reduced voltage / frequency reduce transient and steady-state loading during the black-start mode.

8. The method according to claim 7, further comprising: The first voltage reference and the first frequency reference are respectively added to the second voltage reference and the second frequency reference.

9. The method according to claim 1, wherein, The auxiliary power supply is provided for at least one of the following: auxiliary load, cable charging, or loss of one or more first inverter-based resources.

10. The method according to claim 1, wherein, Switching from the black-start mode to the normal mode further includes sending a signal to the one or more first inverter-based resources at the power plant that have the energy storage, to operate in the normal mode.

11. The method according to claim 1, further comprising: The power plant is energized before it is connected to the power grid.

12. The method according to claim 1, wherein, The one or more first inverter-based resources and the one or more second inverter-based resources include a plurality of wind turbines, wherein at least the one or more first inverter-based resources have grid-forming capabilities.

13. The method according to claim 1, wherein, Implementing the black boot mode also includes: The first converter is operated such that the auxiliary voltage and the auxiliary frequency are independent of the first voltage and the first frequency established by the second converter.

14. The method according to claim 1, wherein, The one or more first inverter-based resources having the energy storage are either a doubly fed induction generator or a full-power conversion system, and the first converter is at least one of a machine-side converter or a grid-side converter.

15. The method according to claim 1, wherein, Switching from the black start mode to the normal mode also includes connecting the one or more auxiliary loads to the isolated first feeder, thereby supplying the one or more auxiliary loads with power from the first feeder.

16. A wind farm, the wind farm comprising: Multiple wind turbines can be connected to the power grid via a transmission network; and A controller including at least one processor, the at least one processor being configured to perform a plurality of operations, the plurality of operations including: As the wind farm disconnects from the power grid, a black start command is sent to one or more first wind turbines on an isolated first feeder at the wind farm, the one or more wind turbines having energy storage. Upon receiving the black start command, a black start mode is implemented using the one or more wind turbines having the energy storage to establish voltage and frequency on the isolated first feeder. Implementing the black start mode includes establishing auxiliary voltage and auxiliary frequency to one or more auxiliary loads using a first converter with the one or more first inverter-based resources having the energy storage, and establishing a first voltage and first frequency to the isolated first feeder using a second converter with the one or more first inverter-based resources having the energy storage. One or more first inverter-based resources without black-start capability are activated via the isolated first feeder; Switching from the black boot mode to normal mode; and The power plant is connected to the power grid to support black start or recovery of a portion of the power grid.

17. The wind farm according to claim 16, wherein, The plurality of operations also include: One or more second feeders of a second wind turbine without black-start capability are energized via the isolated first feeder; and The one or more second wind turbines without black start capability are started sequentially.

18. The wind farm according to claim 16, wherein, The plurality of operations also include: Before sending the black start command, the wind farm is disconnected from the power grid, wherein disconnecting the wind farm from the power grid also includes turning on multiple switching devices of the wind farm to multiple feeders and the main switching device to the transformer.

19. The wind farm according to claim 16, wherein, The plurality of operations also include: Before sending the black start command, the inertial power regulator reference is set to zero, the first frequency is set to the baseline frequency reference, and the first voltage is set to the baseline voltage reference, wherein the baseline voltage reference is less than or equal to the nominal voltage, and the baseline frequency reference is less than or equal to the nominal frequency.

20. The wind farm according to claim 16, wherein, Implementing the black-start mode using the resources of the one or more first inverters having the energy storage also includes: The first voltage of the one or more first inverter-based resources having the energy storage is ramped up at a predetermined rate to a first voltage reference having a first frequency reference, wherein the predetermined rate and the reduced voltage / frequency reduce transient and steady-state loading during the black-start mode.

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