System and method for providing black start of inverter-based resources for grid formation

Abstract

A method for black-starting a power plant with multiple inverter-based resources includes satisfying one or more black-start preconditions. Upon satisfying one or more black-start preconditions, the method includes implementing a self-excitation process on a first inverter-based resource among the multiple inverter-based resources. The self-excitation process includes utilizing at least one of a DC link capacitor or a first converter of a power conversion assembly of the first inverter-based resource. The self-excitation process also includes energizing the generator of the first inverter-based resource among the multiple inverter-based resources by ramping up the DC bus setpoint of the DC link of the first inverter-based resource to gradually increase the terminal voltage of the generator and the voltage of the DC link in a controlled manner. Furthermore, the method includes using the self-excited first inverter-based resource to black-start the remaining inverter-based resources among the multiple inverter-based resources.

Description

Technical Field

[0001] This disclosure generally relates to inverter-based resources, and more particularly to systems and methods for black-starting inverter-based resources for grid formation. Background Technology

[0002] Wind power 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 the known airfoil principle. For example, rotor blades typically have an airfoil cross-sectional profile, causing air to flow over the blades during operation, creating 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 turbines 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 the penetration of wind power 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 power, the penetration of wind power into some grids has increased to the point where wind turbine generators have a significant impact on grid voltage and frequency. When wind turbines are located in weak grids, wind turbine power fluctuations can lead to increased variations in the amplitude and frequency of grid voltage. These fluctuations can adversely affect the performance and stability of the PLL and wind turbine current control, and adversely affect the performance of loads connected to the grid.

[0004] Furthermore, many existing renewable energy converters, such as doubly-fed wind turbines, operate in a "grid-following" mode. Grid-following 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 elements of the main circuit and converter control structure for a grid-following doubly-fed induction generator (DFIG) wind turbine. As shown, the active power reference to the converter is generated by an energy regulator (e.g., the turbine control section of the wind turbine). This is transmitted 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 commands for the voltage to be applied to the system by the converter, such that the actual current closely tracks the commands.

[0005] Alternatively, grid-forming converters provide voltage source characteristics in which the angle and magnitude 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, and the converter helps to establish voltage and frequency for the grid. This characteristic is comparable to that of a conventional generator based on a turbine that drives a synchronous machine. Therefore, a grid-forming source must include the following basic functions: (1) support grid voltage and frequency (both active and reactive) for any current flow within the rated values ​​of the equipment; (2) prevent operation beyond the voltage or current capacity of the equipment by allowing changes in grid voltage or frequency rather than disconnecting the equipment (disconnection is only allowed if the voltage or frequency is outside the limits established by the grid entity); (3) maintain stability for any grid configuration or load characteristics, including serving isolated loads or connecting to other grid-forming sources, and switching between such configurations; (4) share the total load of the grid among other grid-forming sources connected to the grid; (5) traverse grid disturbances (both major and minor); and (6) meet requirements (1)-(5) without requiring rapid communication with other control systems present in the grid or externally generated logical 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-proven for battery systems (see, for example, U.S. Patent No. 5,798,633, entitled "Battery Energy Storage Power Conditioning System"). Applications to 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 Grid Connected Power Generating System," and U.S. Patent No. 9,270,194, entitled "Controller for controlling a power converter." However, such implementations have already been adopted in all-converter wind turbines.

[0007] The black-start capability of traditional generators is a crucial element for grid restoration after power outages. As inverter-based resources replace many synchronous generators in the grid, there is an emerging grid demand for inverter-based resources to provide black-start capabilities similar to those of traditional generators. The inverter-based resources formed by the grid can thus provide black-start functionality.

[0008] In view of the foregoing, this disclosure relates to systems and methods for providing inverter-based resources for grid formation in a black start. 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 having multiple inverter-based resources. The method includes satisfying one or more black-start preconditions. Upon satisfying one or more black-start preconditions, the method includes implementing a self-excitation process on a first inverter-based resource among the multiple inverter-based resources. The self-excitation process includes utilizing at least one of a DC link capacitor or a first converter of a power conversion assembly of the first inverter-based resource. The self-excitation process also includes energizing the generator of the first inverter-based resource among the multiple inverter-based resources by ramping up the DC bus setpoint of the DC link of the first inverter-based resource to gradually increase the terminal voltage of the generator and the voltage of the DC link in a controlled manner. Furthermore, the method includes using the self-excited first inverter-based resource to black-start the remaining inverter-based resources among the multiple inverter-based resources.

[0011] In another aspect, this disclosure relates to a wind farm. The wind farm includes a plurality of wind turbines, the plurality of wind turbines including at least a first wind turbine. The first wind turbine has a generator electrically coupled to a power conversion assembly. The power conversion assembly has a line-side converter and a rotor-side converter coupled together via a DC link, the DC link including a DC link capacitor. The wind farm also includes a controller having at least one processor configured to perform a plurality of operations. The plurality of operations includes: satisfying one or more black-start preconditions; and, upon satisfying one or more black-start preconditions, performing a self-excitation process on the first wind turbine. The self-excitation process includes: utilizing at least one of the DC link capacitors of the power conversion assembly or the first converter; and self-exciting the generator by ramping up the DC bus setpoint of a first inverter-based DC link to gradually increase the terminal voltage of the generator and the voltage of the DC link in a controlled manner. The method also includes using the self-excited first wind turbine to black-start the remaining wind turbines among the plurality of wind turbines.

[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 invention (including its preferred mode) is fully disclosed and can be practiced by one of ordinary skill in the art in the description with reference to the accompanying drawings, in which: Figure 1 The diagram shows a single-line diagram of a conventionally constructed doubly-fed wind turbine generator, which has a converter control structure for grid-following applications. Figure 2 The figure is a perspective view of one embodiment of a wind turbine according to the present disclosure; Figure 3 The figure shows a simplified interior view of a cabin according to an embodiment of the present disclosure; Figure 4 The illustration is suitable for use Figure 1 A schematic diagram of one embodiment of the wind turbine electric power system used in the wind turbine shown; Figure 5 The figure is a schematic diagram of an embodiment of a wind farm with multiple wind turbines according to the present disclosure; Figure 6 The figure shows a block diagram of one embodiment of the controller according to the present disclosure; Figure 7The figure shows a single-line diagram of a doubly-fed wind turbine generator with converter control for grid forming applications according to the present disclosure. Figure 8 The illustration is a schematic diagram of an embodiment of inverter-based resources for a power plant (e.g., a wind farm) with black-start capability according to the present disclosure; Figure 9 The illustration is a schematic diagram of an embodiment of a power plant (e.g., a wind farm) with black-start capability according to the present disclosure; and Figure 10 The illustration is a flowchart of an embodiment of a black-start method for a power plant having multiple inverter-based resources and power generation devices according to the present disclosure. Detailed Implementation

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

[0015] Black-start wind turbines based on doubly-fed induction generators require an external power supply, in the form of an additional battery storage device or a diesel generator, to generate a three-phase AC voltage at the turbine terminals. Using this voltage, the wind turbine can black-start without a power grid. However, providing black-start capability to DFIG-based wind turbines without requiring an external power supply would also be advantageous.

[0016] Therefore, this disclosure generally relates to systems and methods for black-starting power plants with multiple inverter-based resources (e.g., wind turbines). Specifically, in embodiments, this disclosure relates to a method whereby, assuming that auxiliary systems, pitch systems, and yaw systems are powered by existing backup power at the start of the restart process, the generator of a first wind turbine starts without any external power source and from zero terminal voltage. In a particular embodiment, the generator may be a doubly-fed induction generator (DFIG). Thus, in embodiments, the method uses the self-excitation process of the induction machine to gradually build up the terminal voltage in a controlled manner. In embodiments, and as a prerequisite, the wind turbine's drivetrain should rotate at a speed greater than the cut-in speed, and there should be some terminal voltage generated due to residual magnetic force, or the wind turbine's DC link capacitor should have some pre-charge. Furthermore, in embodiments, the method may be used in conjunction with grid formation control to build up the terminal voltage and frequency at rated voltage and frequency. Using the voltage generated by the first wind turbine, additional wind turbines in the wind farm can then be black-started.

[0017] Now refer to the attached diagram, Figure 2 The figure shows a perspective view of an embodiment of the wind turbine 10 according to the present disclosure. The wind turbine 10 described herein can be as follows: Figure 2 The image shows an onshore or offshore wind turbine. For example... Figure 2 As shown, a 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 the rotation of the rotor 18, thereby enabling kinetic energy to be converted from wind 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 This allows for the generation of electrical energy.

[0018] 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 such components and / or perform corrective or control actions. Therefore, the controller 26 may include a computer or other suitable processing unit. Thus, 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. Therefore, the controller 26 may generally be configured to control various operating modes (e.g., start-up or shutdown sequences), reducing or increasing the ratings of the wind turbine and / or individual components of the wind turbine 10.

[0019] Now for reference Figure 2 Illustration Figure 1 The 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 power 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.

[0020] The wind turbine 10 may also have one or more pitch drive mechanisms 32 communicatively coupled to the wind turbine controller 26, wherein each(s) pitch drive mechanism 32 is configured to rotate the pitch bearing 40, and thus rotate individual(s) rotor blades 22 about their respective pitch axes 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).

[0021] 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 wind direction, wind speed, or any other suitable wind conditions near the wind turbine 10 may be measured by using a suitable weather sensor 66. Suitable weather sensors may include, for example, light detection and ranging devices, sound 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 in the art or developed hereafter. Other sensors 68 may be used to measure additional operating parameters of the wind turbine 10, such as voltage, current, vibration, etc., as described herein.

[0022] Now for reference Figure 4 The diagram illustrates a schematic representation of one embodiment of a wind turbine power system 100 according to aspects of this disclosure. Although reference will be made herein... 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 aspects of this disclosure may also be applied to other power generation systems, and as mentioned above, the invention is not limited to wind turbine systems.

[0023] exist Figure 4 In the embodiments and as mentioned, wind turbine 10 ( Figure 2 The rotor 18 of the generator 102 can be optionally coupled to a gearbox 38, which in turn is coupled to a generator 102, which may be a doubly-fed induction generator (DFIG). As shown, the generator 102 can be connected to a stator bus 104. Furthermore, as shown, a power conversion assembly 106 can be connected to the generator 102 via a rotor bus 108 and to the stator bus 104 via a line-side bus 110. Therefore, the stator bus 104 can provide multiphase output power (e.g., three-phase power) from the stator of the generator 102, and the rotor bus 108 can provide multiphase output power (e.g., three-phase power) from the rotor of the generator 102. The power conversion assembly 106 may also include a rotor-side converter (RSC) 112 and a line-side converter (LSC) 114. The generator 102 is coupled to the rotor-side converter 112 via the rotor bus 108. Furthermore, RSC 112 is coupled to LSC 114 via DC link 116, across which is DC link capacitor 118. LSC 114 is then coupled to line-side bus 110.

[0024] RSC 112 and LSC 114 can be configured for normal operating modes in a three-phase pulse-width modulation (PWM) arrangement using one or more switching devices such as insulated-gate bipolar transistor (IGBT) switching elements. Furthermore, the power conversion assembly 106 can be coupled to the converter controller 120 to control the operation of the rotor-side converter 112 and / or the line-side converter 114 as described herein. It should be noted that the converter controller 120 can be configured as an interface between the power conversion assembly 106 and the turbine controller 26, and can include any number of control devices.

[0025] In a typical configuration, various line contactors and circuit breakers (including, for example, grid circuit breaker 122) may also be included to isolate various components necessary for the normal operation of generator 102 during connection to and disconnection from loads 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.

[0026] 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 conversion assembly 106. Rotor-side power converter 112 converts the AC power supplied from rotor bus 108 to direct current (DC) power and supplies DC power to DC link 116. As generally understood, the switching elements (e.g., IGBTs) used in the bridge circuit of rotor-side power converter 112 can be modulated to convert the AC power supplied from rotor bus 108 to DC power suitable for DC link 116.

[0027] Additionally, 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 power 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 conversion assembly 106 can be combined with the power from the stator of the generator 102 to provide multiphase power (e.g., three-phase power) with a frequency that substantially remains at the frequency of the power grid 124 (e.g., 50 Hz or 60 Hz).

[0028] Furthermore, the wind turbine power system 100 may include 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) to connect or disconnect corresponding buses, for example, when excessive current flows and 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.

[0029] Furthermore, the power conversion assembly 106 can receive control signals from, for example, a local control system 176 via the converter controller 120. These control signals may be based, in particular, on sensed states or operating characteristics of the wind turbine power system 100. Typically, the control signals provide control over the operation of the power conversion assembly 106. For example, feedback in the form of sensed speed of the generator 102 can be used to control the conversion of output power from the rotor bus 108 to maintain a correct and balanced multiphase (e.g., three-phase) power supply. Other feedback from other sensors may also be used by controller(s) 120, 26 to control the power conversion assembly 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.

[0030] The power conversion assembly 106 also compensates for or adjusts the frequency of the three-phase power from the rotor for variations in wind speed, such as at hub 20 and rotor blades 22. Thus, the mechanical and electric rotor frequencies are decoupled and facilitate frequency matching between the electric stator and rotor substantially independently of the mechanical rotor speed.

[0031] In some states, the bidirectional characteristics of the power conversion assembly 106, and specifically the bidirectional characteristics of LSC 114 and RSC 112, facilitate the feedback of at least some of the generated electrical power to the generator rotor. More specifically, the power can be transferred from the stator bus 104 to the line-side bus 110, and subsequently through the line contactor 136 and into the power conversion assembly 106, specifically into the 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 the DC link 116. The capacitor 118 helps mitigate DC link voltage amplitude variations by facilitating the reduction of DC ripple sometimes associated with three-phase AC rectification.

[0032] 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, reactive power control of the generator is facilitated by controlling the rotor current and voltage.

[0033] 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 wind turbine 10 described above) 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. 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, such as 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 another embodiment, the field-level controller 156 is configured to send and receive control signals to and from various wind turbines 52, such as, for example, allocating actual and / or reactive power demands across the wind turbines 52 of the wind field 50.

[0034] Now for reference Figure 6 The illustration is a block diagram of one embodiment of 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, which may include suitable computer-readable instructions that, 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).

[0035] As used herein, the term "processor" refers not only to integrated circuits known in the art as included in a computer, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits (ASICs), and other programmable circuits. Additionally, memory device 60 typically includes 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.

[0036] One or more such memory devices 160 are typically 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. Additionally, the controller may include a communication interface 62 for facilitating 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 transmitting and receiving control signals. Furthermore, the controller may include a sensor interface 64 (e.g., one or more analog-to-digital converters) for allowing signals transmitted from sensors 66, 68 to be converted into signals that can be understood and processed by one or more processors 58.

[0037] Now for reference Figure 7 A schematic diagram of an embodiment of the grid-forming power system 200 of this disclosure is shown, particularly a single-line diagram of a doubly-fed wind turbine generator 102 having an advanced control structure for grid-forming characteristics. Specifically, as shown, the grid-forming power system 200 may include the features described herein. Figure 4 Many of the same features are present, and components with the same reference numerals represent similar components. Furthermore, as shown, the power grid forming system 200 may include a control structure for controlling a line-side converter, the control structure for controlling the line-side converter being similar to... Figure 1 The control structure shown is illustrated. 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 then 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.

[0038] 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.

[0039] Now for reference Figures 8-10 This disclosure relates to a method 400 for a power plant 300 (e.g., a wind farm 50) and a black-start power plant 300 according to this disclosure. Specifically, Figure 8 The illustration is a schematic diagram of a first inverter-based resource 302 (e.g., a wind turbine) according to the present disclosure, which is part of a power plant 300. Figure 9 The illustration is based on this disclosure. Figure 8 A schematic diagram of an embodiment of inverter-based resource 302, which provides constant voltage and frequency to power plant 300 to start power plant 300 in the absence of grid power. Figure 10 The illustration is a flowchart of an embodiment of the method 400 for a black-start power plant 300 according to the present disclosure.

[0040] Specific reference Figure 8 In this embodiment, the first inverter-based resource 302 is configured similar to Figure 7 The illustrated power grid forming system 200 (i.e., a grid forming wind turbine) includes a wind turbine 10 capable of connecting to a power grid 304, as shown in the illustrated embodiment and previously explained. Furthermore, as shown, a first inverter-based resource 302 includes a power conversion assembly 306 with a first converter 308 and a second converter 310. Specifically, as shown, the first converter 308 is a line-side converter 114, and the second converter 310 is a rotor-side converter 112, coupled together via a DC link 116. Furthermore, as shown, the DC link 116 includes a DC link capacitor 118. Additionally, as shown, the wind turbine 10 includes a generator 102.

[0041] In addition, such as Figure 8As shown, the first inverter-based resource 302 has grid-forming capability as illustrated by the grid-forming (GFM) control module 312, which is communicatively and electrically coupled to the rotor-side converter 112. Furthermore, as shown, the first inverter-based resource 302 may include a DC voltage establishment module 314 for providing line-side control to the line-side converter 114. More specifically, in an embodiment, as shown, the DC voltage establishment module 314 may include a DC voltage regulator, a flux regulator, a line current regulator, and a modulator. Additionally, the first inverter-based resource 302 may include various switches, such as a synchronization switch 316, a load switch 318 for coupling a load 320 to the stator bus 104, and a grid circuit breaker 324 for selectively coupling the wind turbine 10 to the grid 304.

[0042] Specific reference Figure 10 This article refers to Figures 2-9 Method 400 is described using wind turbine 10 and wind farm 50. However, it should be understood that the disclosed method 400 can be implemented using any inverter-based resources, except for wind turbines with any other suitable configuration. Furthermore, although... Figure 10 The 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. Using the disclosure provided herein, those skilled in the art will appreciate that the 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.

[0043] As shown at (402), method 400 includes satisfying one or more black-start preconditions. For example, in one embodiment, the black-start preconditions may include using an existing backup power system of the wind turbine to power one or more auxiliary systems of the wind turbine. In such an embodiment, the auxiliary systems may include, for example, the control system of the wind turbine 10 (e.g., turbine controller 26), the pitch system (e.g., pitch drive mechanism 32), and / or the yaw system (e.g., yaw drive mechanism 44).

[0044] In another embodiment, one or more black-start preconditions may include at least one of the following: grid circuit breaker 324 open, rotor circuit short-circuited, generator 102 rotating at a speed greater than or equal to the cut-in speed, and / or a voltage value in the stator terminals of generator 102 greater than 0.1 pu due to residual magnetic force, or a precharge of at least 0.1 pu in the DC link 116 of the first inverter-based resource 302. More specifically, in an embodiment, one or more black-start preconditions may include at least one of the following: grid circuit breaker 324 open, rotor circuit short-circuited, generator 102 rotating at a speed greater than or equal to the cut-in speed, and a voltage value in the stator terminals of generator 102 greater than 0.1 pu due to residual magnetic force, or a precharge of at least 0.1 pu in the DC link 116 of the first inverter-based resource 302.

[0045] When one or more black boot prerequisites are met, such as Figure 10 As shown at (404), method 400 includes implementing a self-excitation process for a first inverter-based resource 302 among a plurality of inverter-based resources. For example, in an embodiment, method 400 may include closing a synchronization switch 322 between the grid 304 and the generator 102 after satisfying one or more black-start preconditions to excite the stator of the generator 102. In an embodiment, as Figure 8 and Figure 9 As shown, the first inverter-based resource 302 is under grid formation control.

[0046] Return to reference Figure 10 As shown at (406), the self-excitation process includes energizing the first inverter-based resource from the DC link capacitor 118 of DC link 116 or the first converter 308 of the power conversion assembly 306 of the first inverter-based resource 302 using at least one of these. For example, as shown at (408), method 400 may include energizing the generator 102 of the first inverter-based resource 302 from among a plurality of inverter-based resources by ramping up the DC bus setpoint of the DC link 116 of the first inverter-based resource 302 in a controlled manner to gradually increase the terminal voltage of the generator 102 and the bus voltage of the DC link 116. More specifically, in embodiments, as shown Figure 8As shown, the DC voltage establishment module 314 is configured to establish the DC bus voltage by ramping up the DC bus setpoint and flux setpoint to the rated voltage / flux when the rotor circuit (e.g., rotor circuit breaker) is short-circuited. At this point in the self-excitation process, the stator terminal voltage and frequency are not at the rated voltage / frequency. Furthermore, in an embodiment, method 400 may include opening the rotor circuit (e.g., containing the GFM control module 312) after gradually increasing the terminal voltage of the DC link 116 of the first inverter-based resource 302, thereby enabling grid formation control.

[0047] In a particular embodiment, as an example and as shown at (410), providing a constant voltage and frequency to the remaining inverter-based resources via the first inverter-based resource 302 may include activating the second converter 310 of the power conversion assembly 306 once the bus voltage of the DC link 116 reaches the rated voltage, to use grid forming control and disable flux regulation performed by the first converter 308 to establish the rated terminal voltage at the rated frequency. Furthermore, as shown at (412), method 400 includes using the self-excited first inverter-based resource 302 to black-start the remaining inverter-based resources among a plurality of inverter-based resources. More specifically, in embodiments, as... Figure 9 As shown, the remaining inverter-based resources 330 of the power plant 300 (e.g., which may be a GFM or grid-following GFL wind turbine) can be black-started by providing a constant voltage and frequency to the remaining inverter-based resources via the first inverter-based resource 302. Therefore, in embodiments, the black-start process of this disclosure can be completed without an additional external power source (e.g., an additional anchor generator).

[0048] Further aspects of the invention are provided by the subject matter of the following provisions: A method for black-starting a power plant having multiple inverter-based resources, the method comprising: satisfying one or more black-start preconditions; upon satisfying the one or more black-start preconditions, performing a self-excitation process on a first inverter-based resource among the multiple inverter-based resources, the self-excitation process comprising: utilizing at least one of a DC link capacitor or a first converter of a power conversion assembly of the first inverter-based resource; and self-exciting the generator of the first inverter-based resource among the multiple inverter-based resources by ramping up the DC bus setpoint of the DC link of the first inverter-based resource to gradually increase the terminal voltage of the generator and the bus voltage of the DC link in a controlled manner; and using the self-excited first inverter-based resource to black-start the remaining inverter-based resources among the multiple inverter-based resources.

[0049] According to the method described in any of the foregoing clauses, the first inverter-based resource of the plurality of inverter-based resources is under grid formation control.

[0050] According to any of the foregoing provisions, the method of using the terminal voltage to black-start the remaining inverter-based resources among the plurality of inverter-based resources further includes: providing a constant voltage and frequency to the remaining inverter-based resources among the plurality of inverter-based resources via the first inverter-based resource.

[0051] According to any of the preceding clauses, providing the constant voltage and frequency to the remaining inverter-based resources among the plurality of inverter-based resources via the first inverter-based resource further includes: once the bus voltage of the DC link reaches the rated voltage, activating the second converter of the power conversion assembly to establish the rated terminal voltage at the rated frequency using the grid forming control and disabling flux regulation performed through the first converter.

[0052] According to any of the foregoing provisions, the first inverter-based resource is a wind turbine, and the first converter is a line-side converter of the power conversion assembly, and the second converter is a rotor-side converter of the power conversion assembly.

[0053] The method according to any of the foregoing provisions, wherein the one or more black start prerequisites include using the existing backup power system of the wind turbine to power one or more auxiliary systems of the wind turbine.

[0054] The method according to any of the foregoing provisions, wherein the one or more auxiliary systems include at least one of a control system, a pitch system, and a yaw system.

[0055] According to any of the preceding clauses of the method, the one or more black-start preconditions include at least one of: a grid circuit breaker being open, a rotor circuit being short-circuited, the generator rotating at a speed greater than or equal to the cut-in speed, or at least one of: a voltage value in the stator terminals of the generator being greater than 0.1 pu due to residual magnetic force, or the DC link of the first inverter-based resource having a precharge of at least 0.1 pu.

[0056] According to any of the foregoing provisions, the one or more black-start preconditions include each of the following: the grid circuit breaker being open, the rotor circuit being short-circuited, the generator rotating at a speed greater than or equal to the cut-in speed, and the voltage value at the stator terminals of the generator being greater than 0.1 pu or the precharge in the DC link of the first inverter-based resource being at least 0.1 pu due to residual magnetic force.

[0057] The method according to any of the foregoing provisions further includes opening the short circuit of the rotor circuit after gradually increasing the terminal voltage of the generator and the bus voltage of the DC link of the first inverter-based resource to enable the grid formation control.

[0058] According to any of the foregoing provisions, the self-excitation process further includes closing the synchronization switch of the first inverter-based resource after satisfying the one or more black-start preconditions to excite the stator of the generator.

[0059] The method according to any of the foregoing clauses, wherein the black start is performed without an additional external power source.

[0060] The method according to any of the foregoing clauses, wherein the generator is a doubly-fed induction generator.

[0061] A wind farm includes: a plurality of wind turbines, the plurality of wind turbines including at least: a first wind turbine, the first wind turbine including a generator electrically coupled to a power conversion assembly, the power conversion assembly including a line-side converter and a rotor-side converter coupled together via a DC link, the DC link including a DC link capacitor; 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: satisfying one or more black-start preconditions; upon satisfying the one or more black-start preconditions, performing a self-excitation process on the first wind turbine, the self-excitation process including: utilizing at least one of the DC link capacitor of the power conversion assembly or the first converter; and self-exciting the generator by ramping up the DC bus setpoint of the DC link of the first inverter-based resource to gradually increase the terminal voltage of the generator and the bus voltage of the DC link of the first wind turbine in a controlled manner; and black-starting the remaining wind turbines among the plurality of wind turbines using the self-excited first wind turbine.

[0062] According to any of the foregoing provisions, the first wind turbine of the plurality of wind turbines is under grid formation control.

[0063] According to any of the foregoing provisions, in a wind farm, using the terminal voltage to black-start the remaining wind turbines among the plurality of wind turbines further includes: providing a constant voltage and frequency to the remaining wind turbines among the plurality of wind turbines via the first wind turbine.

[0064] According to any of the preceding provisions, the provision of the constant voltage and frequency to the remaining wind turbines among the plurality of wind turbines via the first wind turbine further includes: activating the second converter of the power conversion assembly once the bus voltage of the DC link reaches the rated voltage, to use the grid forming control and disable flux regulation performed through the first converter to establish the rated terminal voltage at the rated frequency.

[0065] According to any of the foregoing provisions, the one or more black start prerequisites include using the existing backup power system of the first wind turbine to power one or more auxiliary systems of the first wind turbine, wherein the one or more auxiliary systems include at least one of a control system, a pitch system, and a yaw system.

[0066] According to any of the preceding clauses, the one or more black-start preconditions include at least one of the following: a grid circuit breaker is open, a rotor circuit is short-circuited, the generator is rotating at a speed greater than or equal to the cut-in speed, or the voltage value at the stator terminals of the generator is greater than 0.1 pu due to residual magnetic force, or the DC link of the first wind turbine has a precharge of at least 0.1 pu.

[0067] According to any of the foregoing provisions, the plurality of operations further include: closing the synchronization switch of the first wind turbine after satisfying one or more black-start preconditions to excite the stator of the generator; and opening the short circuit of the rotor circuit after gradually increasing the terminal voltage of the generator and the bus voltage of the DC link of the first wind turbine.

[0068] This written description discloses the invention using examples 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 combination of methods. The scope of the invention is defined by the claims and may include other examples that would occur to a person 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 black-starting a power plant with multiple inverter-based resources, the method comprising: One or more black boot prerequisites must be met; When one or more black-start preconditions are met, a self-excitation process is implemented for the first inverter-based resource among the plurality of inverter-based resources. The self-excitation process includes: At least one of the DC link capacitor or the first converter in the power conversion assembly utilizing the resources of the first inverter; and By ramping up the DC bus setpoint of the DC link of the first inverter-based resource to energize the generator of the first inverter-based resource among the plurality of inverter-based resources, the terminal voltage of the generator and the bus voltage of the DC link are gradually increased in a controlled manner; and The remaining inverter-based resources among the plurality of inverter-based resources are black-started using the first self-excited inverter-based resource.

2. The method according to claim 1, wherein, The first inverter-based resource among the plurality of inverter-based resources is under grid formation control.

3. The method of claim 2, wherein, The remaining inverter-based resources among the plurality of inverter-based resources used to black-start the plurality of inverter-based resources also include: A constant voltage and frequency are provided to the remaining inverter-based resources among the plurality of inverter-based resources via the first inverter-based resource.

4. The method of claim 3, wherein, Providing the constant voltage and frequency to the remaining inverter-based resources among the plurality of inverter-based resources via the first inverter-based resource further includes: Once the bus voltage of the DC link reaches the rated voltage, the second converter of the power conversion assembly is activated to establish the rated terminal voltage at the rated frequency using the grid forming control and disabling flux regulation performed through the first converter.

5. The method according to claim 4, wherein, The first inverter-based resource is a wind turbine, and wherein the first converter is a line-side converter of the power conversion assembly, and the second converter is a rotor-side converter of the power conversion assembly.

6. The method according to any one of the preceding claims, wherein, The one or more black start prerequisites include using the existing backup power system of the wind turbine to power one or more auxiliary systems of the wind turbine.

7. The method according to claim 6, wherein, The one or more auxiliary systems include at least one of a control system, a pitch system, and a yaw system.

8. The method according to any one of the preceding claims, wherein, The one or more black-start prerequisites include at least one of the following: a grid circuit breaker is open, a rotor circuit is short-circuited, the generator is rotating at a speed greater than or equal to the cut-in speed, or the voltage value at the stator terminals of the generator is greater than 0.1 pu due to residual magnetic force, or the DC link of the first inverter-based resource has a precharge of at least 0.1 pu.

9. The method according to claim 8, wherein, The one or more black-start prerequisites include each of the following: the grid circuit breaker being open, the rotor circuit being short-circuited, the generator rotating at a speed greater than or equal to the cut-in speed, and the voltage value at the stator terminals of the generator being greater than 0.1 pu due to residual magnetic force or the precharge in the DC link of the first inverter-based resource being at least 0.1 pu.

10. The method of claim 9, further comprising opening the short circuit in the rotor circuit after gradually increasing the terminal voltage of the generator and the bus voltage of the DC link of the first inverter-based resource to enable the grid formation control.

11. The method according to any one of the preceding claims, wherein, The self-excitation process further includes closing the synchronization switch of the first inverter-based resource after satisfying one or more black-start preconditions to excite the stator of the generator.

12. The method according to any one of the preceding claims, wherein, The black start is performed without any external power source.

13. The method according to any one of the preceding claims, wherein, The generator is a doubly-fed induction generator.

14. A wind farm, comprising: A plurality of wind turbines, the plurality of wind turbines including at least: a first wind turbine, the first wind turbine including a generator electrically coupled to a power conversion assembly, the power conversion assembly including a line-side converter and a rotor-side converter coupled together via a DC link, the DC link including a DC link capacitor; The controller includes at least one processor configured to perform a plurality of operations, the plurality of operations including: One or more black boot prerequisites must be met; When one or more of the black-start preconditions are met, a self-excitation process is implemented on the first wind turbine, the self-excitation process including: Utilizing at least one of the DC link capacitor of the power conversion assembly or the first converter; and The generator is energized by ramping up the DC bus setpoint of the first inverter-based DC link to gradually increase the terminal voltage of the generator and the bus voltage of the first wind turbine's DC link in a controlled manner; and The remaining wind turbines among the plurality of wind turbines are black-started using a self-excited first wind turbine.

15. The wind farm according to claim 14, wherein, The first wind turbine among the plurality of wind turbines is under grid formation control.

16. The wind farm according to claim 15, wherein, Using the terminal voltage to black-start the remaining wind turbine among the plurality of wind turbines also includes: A constant voltage and frequency are provided to the remaining wind turbines among the plurality of wind turbines via the first wind turbine.

17. The wind farm according to claim 16, wherein, Providing the constant voltage and frequency to the remaining wind turbines among the plurality of wind turbines via the first wind turbine further includes: Once the bus voltage of the DC link reaches the rated voltage, the second converter of the power conversion assembly is activated to establish the rated terminal voltage at the rated frequency using the grid forming control and disabling flux regulation performed through the first converter.

18. The wind farm according to any one of claims 14 to 17, wherein, The one or more black start prerequisites include using the existing backup power system of the first wind turbine to power one or more auxiliary systems of the first wind turbine, wherein the one or more auxiliary systems include at least one of a control system, a pitch system, and a yaw system.

19. The wind farm according to any one of claims 14 to 18, wherein, The one or more black-start prerequisites include at least one of the following: the grid circuit breaker is open, the rotor circuit is short-circuited, the generator is rotating at a speed greater than or equal to the cut-in speed, or the voltage value in the stator terminals of the generator is greater than 0.1 pu due to residual magnetic force, or the DC link of the first wind turbine has a precharge of at least 0.1 pu.

20. The wind farm according to any one of claims 14 to 19, wherein, The plurality of operations also include: After satisfying one or more black-start preconditions to excite the stator of the generator, the synchronization switch of the first wind turbine is closed; and After gradually increasing the terminal voltage of the generator and the bus voltage of the DC link of the first wind turbine, the short circuit of the rotor circuit is opened.

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