System and method for protecting multiple distributed power generation resources

Abstract

A method for providing a multi-layer protection against faults for a power plant is provided. The method includes monitoring, via a system level controller, one or more parameters at a first plurality of distributed power generation resources. The method also includes implementing, via the system level controller, a failsafe mode when the one or more parameters of the first plurality of distributed power generation resources exceed a first threshold. Specifically, the fail-safe mode includes implementing a time delay, and after the time delay, commanding, via the system level controller, a trip of a first feeder circuit breaker on the first feeder line. The method further includes exiting the failsafe mode when the one or more parameters of the first plurality of distributed power generation resources are equal to or fall below a first threshold.

Description

Technical Field

[0001] The present disclosure generally relates to distributed generation resources, such as wind turbine power systems, solar inverters, or energy storage devices, and more particularly, to systems and methods for protecting multiple distributed generation resources, for example, by tripping at least one feeder breaker. Background Art

[0002] Protection of distributed generation resources (DGRs), such as wind turbines, solar inverters, energy storage devices, and other DGRs, is typically implemented only by protection devices local to such generation. For example, synchronous contactors may be provided within the architecture of a DGR to match the frequency, phase, and voltage of the DGR with other DGRs located within the power grid. Additionally, circuit breakers may be provided together with the DGR or upstream of the DGR along the power plant to provide protection for individual DGRs, series of DGRs, or the power plant against conditions such as overload or short circuit. For example, a feeder breaker may be provided as an upstream circuit breaker for one or more groups of DGRs.

[0003] However, since current is limited by its impedance, the reach of feeder breakers and other upstream circuit breakers typically does not extend beyond the low voltage (LV) side of the transformer of the DGR. As an example, overload or short circuit protection of the circuits within a DGR may be achieved by coordinating the tripping of medium voltage (MV) switchgear and synchronous contactors local to the individual DGRs. More specifically, overload protection involving a DGR is typically achieved by opening the synchronous contactor, where the MV switchgear provides backup protection. In an example, in a wind turbine having a doubly-fed induction generator (DFIG), for a short circuit fault on the stator side of the wind turbine transformer, the MV switchgear is the sole means of protection and typically does not have an autonomous backup.

[0004] As a result, there may be a power path within an individual DGR unit that relies on only a single device (e.g., a circuit breaker) for all of its protection. If that device fails to operate, the backup protection of the DGR unit is insufficient or generally non-existent.

[0005] In view of the foregoing, the present disclosure is directed to a system and method for avoiding undesirable short circuits and overloads by using a system-level controller. For example, the system-level controller may be configured to autonomously detect a fault within a DGR when needed, or alternatively, detect a fault within a DGR based on an instruction from a faulty DGR. Once a fault is detected, the system-level controller is configured to request or command a feeder breaker or another circuit breaker upstream of the DGR to trip to clear the fault in an individual DGR, a series of DGRs, or the entire network of DGRs. Summary of the Invention

[0006] Aspects and advantages of the present disclosure will be set forth in part in the following description, or may be obvious from the description, or may be learned by practice of the present disclosure.

[0007] In one aspect, the present disclosure is directed to a method for providing multi-layer protection against faults for a power plant having a first plurality of distributed generation resources electrically connected to a first feeder line, the first feeder line being electrically connected to a power grid via a first feeder breaker. The method includes monitoring, via a system-level controller, one or more parameters at the first plurality of distributed generation resources. The method further includes implementing a fault protection mode via the system-level controller when the one or more parameters of the first plurality of distributed generation resources exceed a first threshold. Specifically, the fault protection mode includes implementing a time delay, and after the time delay, commanding, via the system-level controller, a trip of the first feeder breaker on the first feeder line. The method also includes exiting the fault protection mode when the one or more parameters of the first plurality of distributed generation resources are equal to or fall below the first threshold.

[0008] In an embodiment, the one or more parameters of the first plurality of distributed generation resources include at least one of voltage, current, active power, reactive power, rotor speed, electrical frequency, wind speed, light intensity, ultraviolet radiation intensity, or one or more fault codes of one or more of the first plurality of distributed generation resources.

[0009] In another embodiment, the method further includes implementing a fault protection mode via the system-level controller when the one or more parameters of the first plurality of distributed generation resources exceed a second threshold, the second threshold being greater than the first threshold.

[0010] In yet another embodiment, a first feeder line and a second feeder line are electrically connected to the power grid via at least one main breaker, the main breaker being upstream of the first feeder breaker and the second feeder breaker, and the fault protection mode further includes tripping the main breaker in addition to the first feeder breaker and the second feeder breaker.

[0011] In yet another embodiment, the fault protection mode further includes: when the first threshold is exceeded, allowing at least one fault clearing device within the first plurality of distributed generation resources to trip on its own within the time delay; and when the second threshold is exceeded, determining, via the system-level controller, the time delay based on one or more predetermined settings.

[0012] In additional embodiments, the fault protection mode further includes: detecting, after the time delay, that the first threshold or the second threshold is exceeded; and implementing an additional time delay before commanding, via the system-level controller, a trip of the first feeder breaker on the first feeder line.

[0013] In yet another embodiment, the method further includes monitoring the one or more parameters of the first plurality of distributed generation resources at an upstream location of the power plant in response to a communication failure between the system-level controller and the first plurality of distributed generation resources.

[0014] In another further embodiment, the fault protection mode further includes allowing a local controller or relay in each of the first plurality of distributed generation resources to command a first fault clearing device within each of the first plurality of distributed generation resources to trip before commanding the first feeder circuit breaker to trip.

[0015] In another embodiment, the fault protection mode further includes: detecting that the first fault clearing device fails to trip, or detecting that one or more parameters of the first plurality of distributed generation resources exceed a first threshold after commanding the first fault clearing device to trip; and allowing a local controller or relay in each of the first plurality of distributed generation resources to command a second fault clearing device within each of the first plurality of distributed generation resources to trip.

[0016] In yet another embodiment, the first plurality of distributed generation resources includes at least one of one or more wind turbines, one or more solar inverters, one or more energy storage devices, or one or more hybrid inverter-based resources.

[0017] In another aspect, the present disclosure is directed to a system for providing multi-layer protection against faults for a power plant. The system includes a first plurality of distributed generation resources electrically connected to a first feeder line and a system-level controller, and the first feeder line is electrically connected to the power grid via a first feeder circuit breaker. In particular, the system-level controller is configured to monitor one or more parameters at the first plurality of distributed generation resources. The system-level controller is further configured to implement a fault protection mode when the one or more parameters of the first plurality of distributed generation resources exceed a first threshold. Specifically, the fault protection mode includes: implementing a time delay; after the time delay, commanding the first feeder circuit breaker on the first feeder line to trip via the system-level controller; and exiting the fault protection mode when the one or more parameters of the first plurality of distributed generation resources are equal to or drop below the first threshold.

[0018] These and other features, aspects, and advantages of the present disclosure will become better understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0019] This application may further include the following solutions: Solution 1. A method for providing multi - layer protection against faults for a power plant, the power plant having a first plurality of distributed generation resources electrically connected to a first feeder line, the first feeder line being electrically connected to a power grid via a first feeder breaker, the method comprising: Monitoring, via a system - level controller, one or more parameters at the first plurality of distributed generation resources; When the one or more parameters at the first plurality of distributed generation resources exceed a first threshold, implementing, via the system - level controller, a fault protection mode, the fault protection mode comprising: Implementing a time delay; and After the time delay, commanding, via the system - level controller, the tripping of the first feeder breaker on the first feeder line; and When the one or more parameters at the first plurality of distributed generation resources are equal to or drop below the first threshold, exiting the fault protection mode.

[0020] Solution 2. The method according to Solution 1, wherein the one or more parameters at the first plurality of distributed generation resources include at least one of voltage, current, active power, reactive power, rotor speed, electrical frequency, wind speed, light intensity, ultraviolet radiation intensity, or one or more fault codes of one or more of the first plurality of distributed generation resources.

[0021] Solution 3. The method according to Solution 1, further comprising implementing the fault protection mode via the system - level controller when the one or more parameters at the first plurality of distributed generation resources exceed a second threshold, the second threshold being greater than the first threshold.

[0022] Solution 4. The method according to Solution 3, wherein the first feeder line and a second feeder line are electrically connected to the power grid via at least one main breaker, the main breaker being upstream of the first feeder breaker and the second feeder breaker, and the fault protection mode further comprises tripping the main breaker in addition to the first feeder breaker and the second feeder breaker.

[0023] Solution 5. The method according to Solution 3, wherein the fault protection mode further comprises: When the first threshold is exceeded, allowing at least one fault clearing device within the first plurality of distributed generation resources to trip on its own within the time delay; and When the second threshold is exceeded, determining, via the system - level controller, the time delay based on one or more predetermined settings.

[0024] Solution 6. The method according to Solution 5, wherein the fault protection mode further includes: Detecting that the first threshold or the second threshold is exceeded after the time delay; and Implementing an additional time delay before tripping the first feeder breaker on the first feeder line via the system-level controller.

[0025] Solution 7. The method according to Solution 1, further including: Monitoring one or more parameters of the first plurality of distributed generation resources at an upstream location of the power plant in response to a communication failure between the system-level controller and the first plurality of distributed generation resources.

[0026] Solution 8. The method according to Solution 1, wherein the fault protection mode further includes: Allowing a local controller or relay in each of the first plurality of distributed generation resources to command a first fault clearing device within each of the first plurality of distributed generation resources to trip before commanding the first feeder breaker to trip.

[0027] Solution 9. The method according to Solution 8, wherein the fault protection mode further includes: Detecting that the first fault clearing device fails to trip, or detecting that one or more parameters of the first plurality of distributed generation resources exceed the first threshold after commanding the first fault clearing device to trip; and Allowing a local controller or relay in each of the first plurality of distributed generation resources to command a second fault clearing device within each of the first plurality of distributed generation resources to trip.

[0028] Solution 10. The method according to Solution 1, wherein the first plurality of distributed generation resources includes at least one of one or more wind turbines, one or more solar inverters, one or more energy storage devices, or one or more hybrid inverter-based resources.

[0029] Solution 11. A system for providing multi-layer protection against faults to a power plant, the system including: A first plurality of distributed generation resources, the first plurality of distributed generation resources being electrically connected to a first feeder line, the first feeder line being electrically connected to a power grid via a first feeder breaker; and A system-level controller, the system-level controller being configured to: Monitor one or more parameters at the first plurality of distributed generation resources, When one or more parameters of the first plurality of distributed generation resources exceed a first threshold, a fault protection mode is implemented via the system-level controller, and the fault protection mode includes: Implementing a time delay; and After the time delay, commanding, via the system-level controller, a trip of the first feeder breaker on the first feeder line; and Exiting the fault protection mode when one or more parameters of the first plurality of distributed generation resources are equal to or fall below the first threshold.

[0030] Solution 12. The system according to Solution 11, wherein the one or more parameters of the first plurality of distributed generation resources include at least one of voltage, current, active power, reactive power, rotor speed, electrical frequency, wind speed, light intensity, ultraviolet radiation intensity, or one or more fault codes of one or more of the first plurality of distributed generation resources.

[0031] Solution 13. The system according to Solution 11, wherein the system-level controller is further configured to: Implement the fault protection mode when one or more parameters of the first plurality of distributed generation resources exceed a second threshold, the second threshold being greater than the first threshold.

[0032] Solution 14. The system according to Solution 13, wherein the first feeder line and the second feeder line are electrically connected to the power grid via at least one main breaker, the main breaker being upstream of the first feeder breaker and the second feeder breaker, and the fault protection mode further includes tripping the main breaker in addition to the first feeder breaker and the second feeder breaker.

[0033] Solution 15. The system according to Solution 13, wherein the fault protection mode further includes: When the first threshold is exceeded, allowing at least one fault clearing device in one or more of the first plurality of distributed generation resources or the second plurality of distributed generation resources to trip on its own within the time delay; and When the second threshold is exceeded, determining the time delay via the system-level controller based on one or more predetermined settings.

[0034] Solution 16. The system according to Solution 15, wherein the fault protection mode further includes: Detecting that the first threshold or the second threshold is exceeded after the time delay; and Implement an additional time delay before tripping the first feeder breaker on the first feeder line via the system-level controller command.

[0035] Scheme 17. The system according to Scheme 11, wherein the system-level controller is further configured to monitor one or more parameters at the power plant level at an upstream location of the power plant in response to a communication failure between the system-level controller and the first plurality of distributed generation resources.

[0036] Scheme 18. The system according to Scheme 11, wherein the fault protection mode further includes: Allowing the local controller or relay of each of the first plurality of distributed generation resources to command the first fault clearing device in each of the first plurality of distributed generation resources to trip before commanding the tripping of the first feeder breaker.

[0037] Scheme 19. The system according to Scheme 18, wherein the fault protection mode further includes: After commanding the first fault clearing device to trip, detecting that one or more parameters of the first plurality of distributed generation resources exceed the first threshold; and Allowing the local controller or relay of each of the first plurality of distributed generation resources to command the second fault clearing device in each of the first plurality of distributed generation resources to trip.

[0038] Scheme 20. The system according to Scheme 11, wherein the first plurality of distributed generation resources includes at least one of one or more wind turbines, one or more solar inverters, one or more energy storage devices, or one or more hybrid inverter-based resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The complete and enabling disclosure of the present disclosure for those of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, including its best mode, wherein:

[0040] Figure 1 A perspective view illustrating an embodiment of a wind turbine according to the present disclosure;

[0041] Figure 2 A schematic diagram illustrating an example embodiment of a distributed generation resource according to the present disclosure;

[0042] Figure 3 A schematic diagram illustrating an example embodiment of a power plant electrically connected to a power grid according to the present disclosure;

[0043] Figure 4Flowchart of an embodiment of a method for providing multi - layer protection against faults to a power plant using a system - level controller with a fault - protection mode according to the present disclosure;

[0044] Figure 5 Flowchart of an embodiment of a fault - protection mode according to the present disclosure, particularly illustrating a fault - protection mode that provides multiple threshold conditions;

[0045] Figure 6 Flowchart of an embodiment of a fault - protection mode according to the present disclosure, particularly illustrating a fault - protection mode that utilizes both a system - level controller and a local DGR controller; and

[0046] Figure 7 Flowchart of an embodiment of a fault - protection mode according to the present disclosure, particularly illustrating a fault - protection mode that utilizes parameters external to a separate DGR. Detailed Description

[0047] Reference will now be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the present disclosure, and not as a limitation thereof. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit thereof. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield yet a further additional embodiment. Accordingly, it is intended that the present disclosure cover such modifications and variations as fall within the scope of the appended claims and their equivalents.

[0048] Generally, the present disclosure is directed to systems and methods for providing multi - layer protection against faults to a power plant using a feeder breaker and a system - level controller placed on a feeder line. Specifically, in an embodiment, the system - level controller is configured to: monitor one or more parameters at a distributed generation resource (DGR) (such as a wind turbine) within a power plant, and implement a fault - protection mode when the (one or more) parameters exceed a threshold in order to protect the power plant from faults. Thus, in certain embodiments, the systems and methods of the present disclosure are capable of providing improved protection to a power plant or an individual DGR within a power plant. For example, in addition to the existing protection within the DGR, the systems and methods of the present disclosure are capable of providing additional protection to the DGR. Additionally, in certain embodiments, the systems and methods of the present disclosure are capable of providing such protection without significant cost or expense by building on the infrastructure of a typical power plant such as a wind farm.

[0049] Now referring to the drawings, Figure 1Perspective view of an embodiment of a wind turbine 10 implementing control techniques according to the present disclosure. As described, the wind turbine 10 is an example of a DGR that can be protected using systems and methods described in more detail below. As shown, the wind turbine 10 generally includes a tower 12 extending from a support surface 14, a nacelle 16 mounted on the tower 12, and a rotor 18 coupled to the nacelle 16. The rotor 18 includes a rotatable hub 20 and at least one rotor blade 22, the rotor blade 22 being coupled to the hub 20 and extending outwardly 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 about the hub 20 to facilitate rotation of the rotor 18 such that kinetic energy can be converted from wind energy into useful mechanical energy and subsequently into electrical energy. For example, the hub 20 may be rotatably coupled to a generator positioned within the nacelle 16 to permit generation of electrical energy.

[0050] 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. Additionally, 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 implement corrective actions. Accordingly, 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. Accordingly, the controller 26 may generally be configured to control various operating modes (e.g., startup or shutdown sequences), derate the wind turbine, and / or control various components of the wind turbine 10, as will be discussed in more detail below.

[0051] Now referring to Figure 2 , a schematic diagram of an example embodiment of a DGR 100 according to the present disclosure is illustrated. As shown, the DGR 100 may be an inverter-based resource, such as a wind turbine power system, such as the wind turbine 10. In additional embodiments, the DGR 100 may also be other types of DGRs, such as solar inverters, energy storage devices, or hybrid inverter-based resources. Accordingly, it should be understood that although Figure 2 features specific to a particular type of DGR may be provided, the present disclosure should not be construed as limited to a particular type of DGR. Now turning to the embodiment provided within Figure 2 , the DGR 100 may include a generator 102, a converter 104, a transformer 106, a feeder line switch 108, a first fault clearing device 110, and a second fault clearing device 114.

[0052] In an embodiment, the generator 102 can be a doubly-fed induction generator (DFIG). The generator 102 can also be any other type of power generation resource. Additionally, as shown, the generator 102 is connected to the converter 104 to change the frequency or phase of the electrical output of the generator 102. Further, as shown, the generator 102 is also electrically connected to the transformer 106 such that the voltage of the electrical output of the generator 102 can be stepped up or down. Additionally, as shown, the transformer 106 is electrically connected to a power grid (not shown) via the feeder line switch 108 such that the electrical output of the generator 102 can be transmitted outside the DGR 100.

[0053] Still referring to Figure 2 , the first fault clearing device 110 is disposed between the generator 102 and the transformer 106. In an embodiment, the first fault clearing device 110 can be a synchronous contactor or switch. Thus, in an embodiment, the first fault clearing device 110 is capable of providing fault protection within the DGR 100.

[0054] Additionally, as shown, the second fault clearing device 114 is disposed between the transformer 106 and the feeder line switch 108. In an embodiment, as shown, the second fault clearing device 114 can be a circuit breaker local to the DGR 100. As such, in an embodiment, the second fault clearing device 114 is capable of providing additional fault protection within the DGR 100. Thus, by using the first fault clearing device 110 and the second fault clearing device 114, greater protection local to the DGR 100 can be provided.

[0055] Referring to Figure 3 , a schematic diagram of an example embodiment of a power plant 200 electrically connected to a power grid 218 in accordance with the present disclosure is illustrated. As shown, the power plant 200 can include a first plurality of DGRs 202 connected to the power grid 218 via a first feeder line 204, and a first feeder breaker 206 on the first feeder line 204 for selectively electrically coupling the first feeder line 204 to the power grid 218. As detailed above, an individual DGR 100 can be a variety of devices or equipment, such as any of those described herein with respect to the DGR 100 illustrated in Figure 2 . Thus, an individual DGR 202 can be electrically connected to the first feeder line 204 via the feeder line switch 108 ( Figure 2 ).

[0056] Power plant 200 may also include additional feeder lines that connect additional DGRs to the power grid 218. For example, as shown, power plant 200 includes a second plurality of DGRs 208, a second feeder line 210, and a second feeder breaker 212. It should be understood that power plant 200 may include any suitable number of feeder lines having any suitable number of DGRs connected to the power grid. Additionally, it should be understood that, like the first plurality of DGRs 202, individual DGRs 100 within the second plurality of DGRs 208 may include various types of DGRs. Specifically, like the first plurality of DGRs 202, individual DGRs 100 within the second plurality of DGRs 208 may include wind turbine power systems, solar inverters, energy storage devices, or hybrid inverter-based resources.

[0057] Like the first plurality of DGRs 202, the second plurality of DGRs 208 may similarly be electrically connected to the power grid 218, for example, via the second feeder line 210 and various feeder line switches. Additionally, like the first plurality of DGRs 202, the second feeder line 210 may be selectively electrically connected to the power grid 218 via the second feeder breaker 212 to provide protection to power plant 200. Additionally, it should be understood that feeder breakers 206, 212 may be placed upstream of the feeder line switches 108, as Figure 3 shown. If desired, feeder breakers 206, 212 may also be placed between the feeder line switches 108. To this end, any number of feeder breakers according to the present disclosure may be utilized.

[0058] Still referring Figure 3 , the first feeder breaker 206 and the second feeder breaker 212 may be electrically connected to the power grid 218 via one or more power lines 214 upstream of the first feeder line 204 and the second feeder line 210. For example, as shown, the first feeder line 204 and the second feeder line 210 are electrically connected to a first power line 214. The first power line 214 is electrically connected to a second power line 215 via a first main breaker 220. The second power line 215 is connected to a third power line 217 via a transformer 216, which may be located at a substation 219 having a substation controller 225.

[0059] The third power line 217 is electrically connected to the power grid 218 via a second main breaker 222. Thus, like the first feeder breaker 206 and the second feeder breaker 212, the first main breaker 220 and the second main breaker 222 may provide protection to power plant 200. It should also be understood that any number of power lines, such as more than three or less than three power lines, may also be included in power plant 200.

[0060] In addition, in an embodiment, as shown, the power plant 200 may further include a system-level controller 224. More specifically, in an embodiment, the system-level controller 224 may be a supervisory control and data acquisition (SCADA) controller, a programmable logic controller (PLC), or other controller-based system. Like the system-level controller 224, the substation controller 225 may also be a SCADA controller, a PLC, or other controller-based system.

[0061] Thus, in an embodiment, the system-level controller 224 is capable of monitoring various parameters within the individual DGRs 100 via a communication channel 226 between the system-level controller 224 and the respective local controllers 228 communicatively coupled to the individual DGRs 100. As described, it should be understood that the local controllers 228 may also include local relays, or any other type of device that provides commands to the DGRs 100 or acts as a conduit for commands.

[0062] In an embodiment, the system-level controller 224 may monitor various parameters at the first plurality of DGRs 202, the second plurality of DGRs 208, etc. The system-level controller 224 may also be able to monitor various parameters from upstream locations of the power plant 200 via hardwired and / or communication-based channels 226. This may occur continuously, in addition to or in response to a communication failure between the system-level controller 224 and the first plurality of DGRs 202 or the second plurality of DGRs 208.

[0063] In an embodiment, the monitored parameter(s) may include various operating conditions or grid conditions, such as active power, reactive power, voltage, current, electrical frequency, generator rotor speed, and various fault codes generated by the DGRs 100. Additionally, the system-level controller 224 may be able to monitor parameters specific to certain types of DGRs. For example, when the DGR 100 is a wind turbine power system, the system-level controller 224 may monitor one or more wind parameters, such as wind speed, wind direction, etc. Alternatively, when the DGR 100 is a solar inverter, the system-level controller 224 may monitor light intensity, ultraviolet (UV) radiation intensity, etc.

[0064] In addition, in an embodiment, the system-level controller 224 may also be used to implement various forms of protection for the power plant 200. For example, the system-level controller 224 is capable of commanding the tripping of the first feeder breaker 206, the second feeder breaker 212, the first main breaker 220, and / or the second main breaker 222. Additionally, the system-level controller 224 is capable of commanding the first fault clearing device 110 and / or the second fault clearing device 114 within the individual DGRs 100 ( Figure 2)Trip. The system-level controller 224 is also capable of identifying whether any of the power lines connected to any one of the first fault clearing device 110, the second fault clearing device 114, the first feeder breaker 206, the second feeder breaker 212, the first main breaker 220, and / or the second main breaker 222 contributed to the fault, and then commanding a trip in response. To this end, the system-level controller 224 may be provided with various fault protection modes and other operating methods, as will be discussed in more detail below.

[0065] Reference Figure 2 and Figure 3 Each of the embodiments discussed may benefit from improved multi-layer protection against faults. For example, Figure 2 the DGR 100 or Figure 3 the power plant 200 may be better protected by utilizing a system-level controller (such as the system-level controller 224 described herein). For example, Figure 4 FIG. illustrates a flow chart of a method 400 for providing multi-layer protection against faults for a power plant using a system-level controller with fault protection modes in accordance with the present disclosure. For purposes of illustration and discussion, Figure 4 the steps are depicted as being performed in a particular order. Using the disclosure provided herein, one of ordinary skill in the art will understand that the various steps of method 400 or any of the methods disclosed herein may be adjusted, modified, rearranged, performed simultaneously, or otherwise modified without departing from the scope of the present disclosure.

[0066] As shown at (402), method 400 includes monitoring, via the system-level controller, one or more parameters at a first plurality of DGRs (such as the first plurality of DGRs 202). A second plurality of DGRs, such as the second plurality of DGRs 208, may also be monitored. For example, in an embodiment, as mentioned, the system-level controller 224 may monitor various operating conditions, grid conditions, or wind conditions, such as active power, reactive power, voltage, current, electrical frequency, generator rotor speed, fault codes, wind parameters, environmental conditions, etc.

[0067] As shown at (404), method 400 includes implementing a fault protection mode via the system-level controller when the (one or more) parameters of the first plurality of DGRs exceed a first threshold. The fault protection mode will be described using the DGR 100 and the power plant 200 described above. However, one of ordinary skill in the art will understand that the fault protection mode may be implemented with other types of power plants and DGRs.

[0068] Generally, a fault protection mode may include implementing a time delay based on the type of parameter-based conditions. After the time delay, the fault protection mode may include commanding a feeder circuit breaker to trip, such as the first feeder circuit breaker 206 or the second feeder circuit breaker 212. The fault protection mode may also include exiting the fault protection mode when the parameter is at an acceptable level. Reference is made herein Figures 5 to 7 to further describe additional implementations of the fault protection mode.

[0069] For example, with specific reference Figure 5 , a flowchart of an embodiment of a fault protection mode 500 that provides multiple threshold conditions is provided. As shown at (502), the fault protection mode 500 begins. As shown at (504), the system-level controller 224 collects one or more parameters from individual DGRs 100, such as DGRs within the first plurality of DGRs 202 or the second plurality of DGRs 208. As shown at (506), the system-level controller 224 is configured to implement a sanity check. If the sanity check fails, the fault protection mode 500 returns to (502). If the sanity check passes, as shown at (506), the system-level controller 224 is configured to determine whether a subset of the parameters for the DGR 100 (i.e., one or more parameters or any of the parameters) exceeds or is outside a threshold, such as a super threshold, as shown at (508). If the subset of parameters is outside the super threshold, as shown at (510), the system-level controller 224 may implement a time delay determined based on one or more predetermined settings set by the system-level controller 224.

[0070] For example, these settings for the super threshold may forego steps that would allow the fault clearing devices 110, 114 within the DGR 100 of the first plurality of DGRs 202 or the second plurality of DGRs 208 to trip within the time delay. This may be done to avoid any damage to components within the DGR 100 of the first plurality of DGRs 202 or the second plurality of DGRs 208 due to a failure to trip in a timely manner when the parameter is at a higher level indicated by the super threshold (especially when compared to the sub threshold, which will be discussed in more detail below).

[0071] As shown at (512), the super threshold response may also include an inspection of the DGR 100 to determine whether the super threshold is still exceeded after the time delay. This inspection may not necessarily consider the fault clearing devices 110, 114, but only determine whether the parameter associated with the super threshold is still exceeded.

[0072] If a subset of the parameters still exceeds the super threshold, then as shown at (514), the fault protection mode 500 will first identify the feeder circuit breakers 206, 212 associated with the DGR 100 that expresses the subset of parameters greater than the super threshold. Once identified, the system-level controller 224 will command the tripping of the feeder circuit breakers 206, 212 associated with the DGR 100 that expresses the elevated parameters, as shown at (516). Once the fault is cleared, the fault protection mode 500 will end, as shown at (518), and the normal operation of the power plant 200 will resume. It should be understood that the end of the fault protection mode 500 may also mean that the fault protection mode returns to (502).

[0073] Return to the scenario indicated by (508). If the super threshold is not exceeded, then as shown at (520), the system-level controller 224 will perform an inspection to determine whether the subset of parameters exceeds the sub threshold, where the sub threshold is within the super threshold. Specifically, the sub threshold may be a first threshold, and the super threshold may be a second threshold, where the first threshold is within the second threshold.

[0074] If the subset of parameters does not exceed the sub threshold, the fault protection mode 500 returns to (502). On the other hand, if the subset of parameters does exceed the sub threshold, then as shown at (522), the system-level controller 224 will estimate the time for the DGR 100 associated with the exceeded sub threshold to trip on its own, for example, by using the fault clearing devices 110, 114. Once the time has been estimated, then as shown at (524), the system-level controller 224 will implement a countdown of the time for the DGR 100 associated with the exceeded sub threshold to trip on its own. The countdown shown at (524) may also include an additional time delay to prevent spurious tripping of the feeder circuit breakers 206, 212, such that the energy transfer performed by the power plant 200 can be maintained without interruption.

[0075] After the countdown, the fault protection mode 500 may include an inspection by the system-level controller 224 to determine whether the sub threshold is still exceeded, as shown by (526). If the sub threshold is no longer exceeded, the fault protection mode 500 returns to (502). However, if the sub threshold is exceeded, the system-level controller may start the series of commands (514), (516), and (518) described above to command the feeder circuit breakers 206, 212 to trip to clear the fault and return the power plant 200 to normal operation.

[0076] Generally, the fault protection mode mainly utilizes the system-level controller, but may also operate in cooperation with local DGR-level controllers (such as the local controller 228). For example, now referring to Figure 6, a flowchart of an embodiment of a fault protection mode is provided. As shown at (602), the fault protection mode 600 begins. As shown at (604), the local controller 228 for each DGR 100 determines whether a fault exists within the DGR 100. For example, the local controller 228 or the system-level controller 224 may determine that a parameter from the DGR 100 exceeds a threshold to determine the existence of a fault. The local controller 228 may also receive one or more fault codes from any of the components within the DGR 100, and the one or more fault codes will indicate to the local controller 228 the existence of a fault. If the local controller 228 does not detect a fault, the fault protection mode 600 returns to (602).

[0077] However, if a fault does exist, then as shown by (606), the local-level controller 228 will determine whether it can clear the fault in the DGR 100. If the local-level controller 228 determines that it can clear the fault, then as shown at (608), the local-level controller 228 will command the first fault clearing device 110 (such as a synchronous contactor) to open and clear the fault. After the command, the local-level controller 228 will determine whether the first fault clearing device 110 has opened and successfully cleared the fault, as shown by (610). If necessary, the system-level controller 224 or the local controller 228 may check whether the first fault clearing device 110 has been successful in clearing the fault. If the fault is successfully cleared, the fault protection mode 600 will end, and the power plant 200 will return to normal operation, as shown by (612). The end indicated by (612) may also mean returning to the start as shown by (602).

[0078] However, if the first fault clearing device 110 determines that it cannot clear the fault, or the first fault clearing device 110 determines that it can clear the fault but fails to clear the fault, then the local-level controller 228 may command the second fault clearing device 114 (such as MV switchgear) to open, as shown at (614). After the command, the local-level controller 228 may determine whether the second fault clearing device 114 has been successful in clearing the fault, as shown by (616). Like the first fault clearing device 110, the system-level controller 224 or the local controller 228 may check whether the second fault clearing device 114 has been successful in clearing the fault. If the second fault clearing device 114 is successful, the fault protection mode will end, as shown by (612). However, if the second fault clearing device 114 is not successful, then as shown by (618), the local-level controller may notify the system-level controller 224 that the local-level controller 228's protection of the DGR 100 has failed.

[0079] Once notified, the system-level controller can identify the feeder breakers 206, 210 associated with the reported fault, as shown by (620). Once identified, the system-level controller 224 can then command the tripping of the feeder breakers 206, 212 to clear the fault in the DGR 100. After the fault is cleared, the fault protection mode ends, as shown by (612). Thus, by using the fault protection mode 600, the priorities of local-level resources such as the fault clearing device 110 and the second fault clearing device 114 can be prioritized, such that overutilization of the feeder breakers 206, 210 can be avoided, and power generation from the first plurality of DGRs 202 or the second plurality of DGRs 208 can be maintained.

[0080] The fault protection mode can also monitor parameters external to an individual DGR or a plurality of DGRs. For example, now referring to Figure 7 , a flowchart of an embodiment of a fault protection mode that utilizes parameters external to an individual DGR is provided.

[0081] As shown at (702), the fault protection mode 700 begins. As shown at (704), the system-level controller 224 can monitor a first set of parameters at a location upstream of the power plant 200. For example, the upstream location can be at the transformer 216, the first main breaker 220, or the second main breaker 222. Additionally, the first set of parameters can be any of the parameters previously described. However, in an exemplary embodiment, the first set of parameters can include voltage or current at the upstream location. The monitored voltage or current can then be converted to active power or reactive power for use by the system-level controller 224 in the fault protection mode 700. Monitoring at the upstream location can be particularly advantageous in the event of a communication failure between the system-level controller 224 and the first plurality of distributed generation resources 202 or the second plurality of distributed generation resources 208. In such scenarios, the system-level controller 224 can utilize the first main breaker 220 or the second main breaker 222 to clear the fault or reduce parameters that exceed a threshold within the first plurality of DGRs 202 or the second plurality of DGRs 208. Additionally, the system-level controller can utilize the substation controller 225 to trip the first feeder breaker 206 or the second feeder breaker 212, as will be discussed in more detail below.

[0082] As shown at (704), the system-level controller 224 can determine whether a sudden change (i.e., an exceeded threshold) has occurred in the first set of parameters that is inconsistent with a set point or an understood level at which a subset of the parameters should be. For example, in an exemplary embodiment, if the first set of parameters monitored at the upstream location includes voltage or current (which is converted to active power or reactive power), the system-level controller can compare the active power or reactive power at the upstream location with the set point at which the active power or reactive power should be.

[0083] The setpoint can be based on other factors obtained at other locations in the power plant 200. For example, the setpoint can be a second set of parameters monitored at other locations in the power plant 200. For example, if the first set of parameters at the monitored upstream location is current or voltage (which is converted to active power or reactive power), the second set of parameters used to provide the setpoint can be voltage, current, active power, reactive power, rotor speed, electrical frequency, wind speed, light intensity, ultraviolet radiation intensity at the first plurality of DGRs 202 or the second plurality of DGRs 208.

[0084] If no sudden change has occurred, the fault protection mode 700 returns to (702). However, if a sudden change has occurred, as shown at (706), the fault protection mode 700 can include providing a time delay similar to the time delays discussed with reference to the fault protection mode 500 or the fault protection mode 600. After the time delay, the system-level controller 224 can determine whether a difference between the first set of parameters and the setpoint or the second set of parameters still exists, as shown at (708). If the inconsistency between the first set of parameters and the setpoint no longer exists, the fault protection mode 700 returns to (702).

[0085] However, if an inconsistency still exists between the first set of parameters and the setpoint, as shown at (710), the system-level controller 224 sends an alert to the substation controller 225 at the substation 219 after the time delay. After the alert is received by the substation controller 224, the substation controller identifies which of the feeder breakers 206, 212 is associated with the sudden change in the first set of parameters, as shown at (712). Once the feeder breakers 206, 212 associated with the sudden change in the first set of parameters are identified, as shown at (714), the substation controller 224 commands the tripping of the feeder breakers 206, 212 associated with the sudden change in the first set of parameters. After the first set of parameters returns to a value consistent with the setpoint or the fault has otherwise been cleared from the power plant 200, the fault protection mode 700 ends and the power plant 200 returns to normal operation, as shown at (716). It should be understood that the end indicated by (716) can also be a return to (702).

[0086] Thus, each of the fault protection modes 500, 600, 700 can use the resources provided within the power plant (i.e., the feeder breakers) to provide unique protection means for the DGR, the plurality of DGRs, and the power plant.

[0087] In addition to the first feeder breaker 206 and the second feeder breaker 212, the fault protection modes 500, 600, and 700 may also utilize the first main breaker 220 and the second main breaker 222. For example, the fault protection modes 500, 600, and 700 may effect the tripping of the first feeder breaker 206 and the second feeder breaker 212, and if the tripping of the first feeder breaker 206 and the second feeder breaker 212 is unsuccessful or fails to provide a desired result, the fault protection modes 500, 600, and 700 may effect the tripping of the first main breaker 220 or the second main breaker 222. Accordingly, the fault protection modes 500, 600, and 700 may be used to provide further protection for the power plant 200.

[0088] This written description uses examples to disclose the present disclosure, including the best mode, and also enables any person skilled in the art to practice the present disclosure, including making and using any device or system and performing any incorporated method. The patentable scope of the present disclosure 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 are not different in literal language from the claims, or if they include equivalent structural elements that are not substantially different in their literal language from the claims.

Claims

1. A method for providing multi - layer protection against faults for a power plant, the power plant having a first plurality of distributed generation resources electrically connected to a first feeder line, the first feeder line being electrically connected to a power grid via a first feeder breaker, the method comprising: Monitoring, via a system - level controller, one or more parameters at the first plurality of distributed generation resources; When one or more of the one or more parameters at the first plurality of distributed generation resources exceed a first threshold, implementing, via the system - level controller, a fault protection mode, the fault protection mode including: Implementing a time delay; and After the time delay, commanding, via the system - level controller, the tripping of the first feeder breaker on the first feeder line; and When one or more of the one or more parameters of the first plurality of distributed generation resources are equal to or drop below the first threshold, exiting the fault protection mode.

2. The method according to claim 1, wherein, The one or more parameters of the first plurality of distributed generation resources include at least one of voltage, current, active power, reactive power, rotor speed, electrical frequency, wind speed, light intensity, ultraviolet radiation intensity, or one or more fault codes of one or more of the first plurality of distributed generation resources.

3. The method according to claim 1, further comprising implementing the fault protection mode via the system - level controller when one or more of the one or more parameters of the first plurality of distributed generation resources exceed a second threshold, the second threshold being greater than the first threshold.

4. The method according to claim 3, wherein The first feeder line and a second feeder line are electrically connected to the power grid via at least one main breaker, the main breaker being upstream of the first feeder breaker and the second feeder breaker, and the fault protection mode further includes tripping the main breaker in addition to the first feeder breaker and the second feeder breaker.

5. The method according to claim 3, wherein The fault protection mode further includes: When the first threshold is exceeded, allowing at least one fault clearing device within the first plurality of distributed generation resources to trip on its own within the time delay; and When the second threshold is exceeded, determining, via the system - level controller, the time delay based on one or more predetermined settings.

6. The method according to claim 5, wherein, The fault protection mode further includes: Detecting that the first threshold or the second threshold is exceeded after the time delay; and Implementing an additional time delay before commanding, via the system - level controller, the tripping of the first feeder breaker on the first feeder line.

7. The method according to claim 1 further comprises: Monitoring, in response to a communication failure between the system - level controller and the first plurality of distributed generation resources, one or more parameters of the first plurality of distributed generation resources at an upstream location of the power plant.

8. The method according to claim 1, wherein The fault protection mode further includes: Allowing a local controller or relay in each of the first plurality of distributed generation resources to command a first fault clearing device in each of the first plurality of distributed generation resources to trip before commanding the tripping of the first feeder breaker.

9. The method according to claim 8, wherein, The fault protection mode further includes: Detect that the first fault clearing device fails to trip, or detect that one or more parameters of the first plurality of distributed generation resources exceed the first threshold after commanding the first fault clearing device to trip; and Allow a local controller or relay in each of the first plurality of distributed generation resources to command a second fault clearing device in each of the first plurality of distributed generation resources to trip.

10. The method according to claim 1, wherein, The first plurality of distributed generation resources includes at least one of one or more wind turbines, one or more solar inverters, one or more energy storage devices, or one or more hybrid inverter-based resources.

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