Patent Application
20250070697
The present disclosure relates in general to power generation, and more particularly to systems and methods for decoupling current command components in rotating frames with calculated reference nodes.
Power generating assets may take a variety of forms and may include assets which rely on renewable and/or nonrenewable sources of energy. Those power generating assets which rely on renewable sources of energy may generally be considered one of the cleanest, most environmentally friendly energy sources presently available. For example, wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The nacelle includes a rotor assembly coupled to the gearbox and to the generator. The rotor assembly and the gearbox are mounted on a bedplate support frame located within the nacelle. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy and the electrical energy may be transmitted to a converter and/or a transformer housed within the tower and subsequently deployed to a utility grid. Modern wind power generation systems typically take the form of a wind farm having multiple wind turbine generators that are operable to supply power to a transmission system providing power to an electrical grid.
Wind turbines can be distinguished in two types: fixed speed and variable speed turbines. Conventionally, variable speed wind turbines are controlled as current sources connected to an electrical grid. In other words, the variable speed wind turbines rely on a grid frequency detected by a phase locked loop (PLL) as a reference and inject a specified amount of current into the grid. The conventional current source control of the wind turbines is based on the assumptions that the grid voltage waveforms are fundamental voltage waveforms with fixed frequency and magnitude and that the penetration of wind power into the grid is low enough so as to not cause disturbances to the grid voltage magnitude and frequency. Thus, the wind turbines simply inject the specified current into the grid based on the fundamental voltage waveforms. However, with the rapid growth of the wind power, wind power penetration into some grids has increased to the point where wind turbine generators have a significant impact on the grid voltage and frequency. When wind turbines are located in a weak grid, wind turbine power fluctuations may lead to an increase in magnitude and frequency variations in the grid voltage. These fluctuations may adversely affect the performance and stability of the PLL and wind turbine current control.
Furthermore, existing controls for doubly-fed induction generator (DFIG) wind turbine systems with three-winding grid-interfacing transformers estimate primary-side transformer voltage to lock its phase reference (PLL). Once this phase is locked, angular information of feedback signals is used to transform typical three-phase power system (which uses an a-b-c reference frame) into a two-phase system (which uses a d-q reference frame). A proper selection of this phase refence also allows decoupling of the active and reactive current control loops. Therefore, this control structure assumes decoupled control of active and reactive components of current. However, the PLL reference node being separate from the voltage and current feedback nodes introduces coupling between active and reactive components of current.
Thus, the present disclosure is directed to a system and method for decoupling current command components in rotating frames with calculated reference nodes to address the aforementioned issues. More specifically, the present disclosure describes how compensation terms on the current command components can be introduced to significantly reduce a coupling effect that active and reactive current regulation loops have on each other.
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In one aspect, the present disclosure is directed to a method for controlling a power generating asset having a generator. The generator has a stator operably coupled to a transformer and a rotor operably coupled to the transformer via a power converter. The method includes using, via a controller, an angle of a phase-locked loop (PLL) reference signal of a PLL at a PLL reference node of the power generating asset to transform a three-phase set of signals to a two-dimensional orthogonal coordinate system of a synchronously-rotating frame. The two-dimensional orthogonal coordinate system include x and y components of at least one of voltage and current. The method also includes determining, via the controller, one or more dynamic decoupling factors as a function of one or more of the x and y components of voltage and current. Further, the method includes applying, via the controller, the one or more dynamic decoupling factors to current command calculation logic to mitigate a coupling effect of one or more current command components. The method may further include any of the additional steps and/or features described herein.
In another aspect, the present disclosure is directed to a system for operating power generating asset. The system includes a generator connected to a power grid and a controller communicatively coupled to the generator. The controller includes at least one processor configured to perform a plurality of operations, including but not limited to using an angle of a phase-locked loop (PLL) reference signal of a PLL at a PLL reference node of the power generating asset to transform a three-phase set of signals to a two-dimensional orthogonal coordinate system of a synchronously-rotating frame, the two-dimensional orthogonal coordinate system including x and y components of at least one of voltage and current, determining one or more dynamic decoupling factors as a function of one or more of the x and y components of at least one of voltage and current, and applying the one or more dynamic decoupling factors to current command calculation logic to mitigate a coupling effect of one or more current command components. The plurality of operations may include any of the operations and/or features described herein.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.
The terms “coupled,” “fixed,” “attached to,” and the like refer to both direct coupling, fixing, or attaching, as well as indirect coupling, fixing, or attaching through one or more intermediate components or features, unless otherwise specified herein.
Approximating language, as used herein throughout the specification and claims, is applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. For example, the approximating language may refer to being within a 10 percent margin.
Here and throughout the specification and claims, range limitations are combined and interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.
Generally, the present disclosure is directed to systems and methods for controlling a power generating asset, such as a wind turbine, connected to an electrical grid. In particular, the systems and methods disclosed herein may be employed to introduce reactive current command compensation after any algorithm that efficiently distributes net current flow between secondary transformer windings. Moreover, the systems and methods disclosed herein may be employed to define new dynamic decoupling factors based on ratio of voltage feedback magnitude to individual components. In addition, the systems and methods disclosed herein may be employed to cancel a coupling effect by adding a product of uncompensated commands and dynamic decoupling factors to existing current command calculation logic. It should be further appreciated that such a decoupling of the drivetrain shaft power from the active power injected into the electrical grid may be desirable in both grid-following and grid-forming applications.
Accordingly, the present disclosure is configured to provide numerous benefits not present in the prior art. For example, new compensation terms are intended to improve performance aspects of existing DFIG converter controls, in the areas of steady state discrepancy elimination between line and stator current control, positive sequence reactive current injection during unbalanced faults, voltage stability for unbalanced grid faults, and/or ride-through capability for remote faults. Thus, the present disclosure is configured to eliminate wasted converter current capability by preventing unnecessary circulating reactive current between the line-side converter and the generator stator, reduce the number of wind turbine trips when subjected to remote grid faults, improve voltage stability compliance under grid disturbance, and/or improve reactive current K-factor compliance, where K-factor is a voltage-variation to current-variation proportionality number during grid events, commonly required by grid codes.
Referring now to the drawings,
When configured as a wind turbine 114, the power generating asset 100 may generally include a tower 102 extending from a support surface 104, a nacelle 106, mounted on the tower 102, and a rotor 108 coupled to the nacelle 106. The rotor 108 includes a rotatable hub 110 and at least one rotor blade 112 coupled to and extending outwardly from the hub 110. For example, in the illustrated embodiment, the rotor 108 includes three rotor blades 112. However, in an alternative embodiment, the rotor 108 may include more or less than three rotor blades 112. Each rotor blade 112 may be spaced about the hub 110 to facilitate rotating the rotor 108 to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub 110 may be rotatably coupled to an electric generator 118 (
The wind turbine 114 may also include a controller 120 centralized within the nacelle 106. However, in other embodiments, the controller 120 may be located within any other component of the wind turbine 114 or at a location outside the wind turbine. Further, the controller 120 may be communicatively coupled to any number of the components of the wind turbine 114 in order to control the components. As such, the controller 120 may include a computer or other suitable processing unit. Thus, in several embodiments, the controller 120 may include suitable computer-readable instructions that, when implemented, configure the controller 120 to perform various different functions, such as receiving, transmitting and/or executing wind turbine control signals.
As depicted in
It should also be appreciated that, as used herein, the term “monitor” and variations thereof indicates that the various sensors of the power generating asset 100 may be configured to provide a direct measurement of the parameters being monitored or an indirect measurement of such parameters. Thus, the sensors described herein may, for example, be used to generate signals relating to the parameter being monitored, which can then be utilized by the controller 120 to determine a condition or response of the power generating asset 100.
Referring now to
In an embodiment, the rotor side converter 212 and the line-side converter 214 may be configured for normal operating mode in a three-phase, pulse width modulation (PWM) arrangement using insulated gate bipolar transistors (IGBTs) as switching devices. Other suitable switching devices may be used, such as insulated gate commuted thyristors, MOSFETs, bipolar transistors, silicone-controlled rectifiers, and/or other suitable switching devices. The rotor side converter 212 and the line-side converter 214 may be coupled via a DC link 218 across a DC link capacitor 220.
In an embodiment, the power converter 208 may be coupled to a converter controller 209 and/or the controller 120, which is configured to control the operation of the power converter 208. For example, the converter controller 209 may send control commands to the rotor side converter 212 and the line-side converter 214 to control the modulation of switching elements used in the power converter 208 to establish a desired generator torque setpoint and/or power output.
As further depicted in
In an embodiment, the electrical system 200 may include various protective features (e.g., circuit breakers, fuses, contactors, and other devices) to control and/or protect the various components of the electrical system 200. For example, the electrical system 200 may, in an embodiment, include a grid circuit breaker 230, a stator bus circuit breaker 232, and/or a line bus circuit breaker 234. The circuit breaker(s) 230, 232, 234 of the electrical system 200 may connect or disconnect corresponding components of the electrical system 200 when a condition of the electrical system 200 approaches a threshold (e.g., a current threshold and/or an operational threshold) of the electrical system 200.
Referring now to
As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) 242 may generally comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s) 242 may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) 240, configure the controller 120 to perform various functions as described herein, as well as various other suitable computer-implemented functions.
Referring now to
Furthermore, as shown in
More specifically, as shown in
As shown at (502), the method 500 includes using, via a controller, an angle of a phase-locked loop (PLL) reference signal of a PLL at a PLL reference node of the power generating asset to transform a three-phase set of signals to a two-dimensional orthogonal coordinate system of a synchronously-rotating frame. The two-dimensional orthogonal coordinate system include x and y components of at least one of voltage and current. As shown at (504), the method 500 may include determining, via the controller, one or more dynamic decoupling factors as a function of one or more of the x and y components of at least one of voltage and current.
As shown at (506), the method 500 may include applying, via the controller, the one or more dynamic decoupling factors to current command calculation logic to mitigate a coupling effect of one or more current command components. For example, in an embodiment, the coupling effect of the one or more current command components occurs between active and reactive current command components.
For example, in an embodiment, applying the dynamic decoupling factor(s) to the current command calculation logic to mitigate the coupling effect of one or more current command components may include observing an approach of a first dynamic decoupling x-factor and a second dynamic decoupling y-factor to zero as the x component of voltage aligns with an x-axis of the two-dimensional synchronously-rotating frame. In such embodiments, if the first dynamic decoupling x-factor and the second dynamic decoupling y-factor both approach zero as the x component of voltage aligns with the x-axis of the two-dimensional synchronously-rotating frame, then the first dynamic decoupling x-factor and the second dynamic decoupling y-factor have no effect on the current command calculation logic.
However, if the first dynamic decoupling x-factor and the second dynamic decoupling y-factor do not both approach zero as the x component of voltage aligns with the x-axis of the two-dimensional synchronously-rotating frame, then one can conclude that one or more feedback and reference node disparities exist in the power generating asset and the first and second dynamic decoupling x-and y-factors provide dynamic measures of how much one or more of the current command components needs to be adjusted in order to obtain a desired net current at the PLL reference node. Thus, the first and second dynamic decoupling x-and y-factors are applied to the current command calculation logic to mitigate the coupling effect of the current command component(s).
The method 500 of
Still referring to
For example, in an embodiment, as shown in
In such embodiments, the voltage magnitude of the PLL reference signal may be determined as a function of the x and y components of voltage. More specifically, in an embodiment, the voltage magnitude may be calculated using a square root of a summation of the x and y components of voltage squared, as provided in Equation (4) below:
Referring now to
Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments. Similarly, the various method steps and features described, as well as other known equivalents for each such methods and feature, can be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
The present application claims priority to PCT Application Serial Number PCT/US2021/063774, filed Dec. 16, 2021, which is incorporated by reference herein in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2021/063774 | 12/16/2021 | WO |
