Robust, Cybersecurity-Enabled, Cooperative Detection of Unintended Islands for Microgrids

Abstract

Due to the unintentional islanding (UI) of a distributed energy resource (DER) circuit, the external area power system (EPS) of the DER circuit may remain energized. Therefore, UI detection methods have been developed to detect unintentional islanding and trigger a UI response. However, individual UI detection methods have various drawbacks. Accordingly, a consensus-based UI detection process is disclosed that optionally implements different UI detection methods to build a consensus from multiple UI detection sources. The redundancy in this consensus-based UI detection process provides robust, sensitive, selective, and cyber-secure UI detection for the entire DER circuit. For example, the consensus-based UI detection process can exclude or reduce non-detection areas, avoid false positives, and prevent cyberattacks.

Description

Technical Field

[0001] Government's licensing right This invention was made with government support under Contract No. DE-OE0000896 awarded by the Department of Energy. The United States government has certain rights in this invention.

[0002] Background Field of the Invention Embodiments described herein generally relate to cooperative island detection, and more particularly, to robust, sensitive, selective, and cyber-secure cooperative detection of unintentional islands (UI) for distributed energy resource (DER) circuits such as microgrids.

Background Art

[0003] Description of Related Art Grid codes generally require that interconnections with distributed energy resources be able to accurately and quickly detect unintentional islands and de-energize. The new grid code extends this requirement to a single point of common coupling (PCC) between the microgrid and the main grid. For microgrids operating under Institute of Electrical and Electronics Engineers (IEEE) Standard (IEEE1547-2018) or similar grid codes regarding the interconnection and interoperability of distributed energy resources with the associated power system interface, the UI response requirements are the same as for stand-alone distributed energy resources. IEEE1547-2018 defines an unintentional island as an island scenario where a DER circuit energizes a part of the regional power system (EPS) through the point of common coupling. However, as used herein, the term "unintentional island" can be understood to refer to any scenario where one or more distributed energy resources are unintentionally separated from the rest of the power system and continue to supply power so as to energize the components of the power system.

[0004] Typical operation of a microgrid as an intentional island involves disconnection from the area EPS along a predefined electrical boundary (e.g., the point of common coupling). If an island is formed outside these electrical boundaries such that both the microgrid and electrical system components are included within the area EPS that is not part of the microgrid, the microgrid needs to detect the unintentional island and de-energize the non-microgrid components. For example, if a transformer located upstream of the microgrid and the point of common coupling between the microgrid is separated from the main grid due to a fault, the microgrid must quickly de-energize the transformer.

[0005] Mango et al., ‘‘Overview of Anti-Islanding Algorithms for PV Systems. Part I: Passive Methods’’, 12th Int’l Power Electronics and Motion Control Conference, 2006, pp. 1878-1883 provides an overview of some existing anti-islanding algorithms. This disclosure relates to overcoming one or more of the problems found in state-of-the-art algorithms. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0006] SUMMARY Accordingly, a system, method, and non-transitory computer-readable medium for robust, sensitive, selective, and cyber-secure cooperative UI detection for DER circuits including microgrids are disclosed. The objective of embodiments is to build consensus from multiple UI detection sources using one or more redundancy steps before triggering a UI response such as a transition to an intentional island where the area EPS is de-energized. A further objective of some embodiments is to eliminate or reduce non-detection regions within the UI detection method. A further objective of some embodiments is to prevent false positives asserted by UI detection sources from triggering a UI response. A further objective of some embodiments is to prevent a compromised UI detection source from supporting a cyber-attack aimed at islanding a DER circuit such as a microgrid.

[0007] In one embodiment, a method for detecting unintentional islanding (UI) of a distributed energy resource (DER) circuit, using at least one hardware processor to monitor transmissions from a plurality of UI detection sources to identify an indication of unintentional islanding from the plurality of UI detection sources, and determining a detection of unintentional islanding of the DER circuit when an indication of unintentional islanding is identified from fewer than a consensus number of the plurality of UI detection sources during a time window, where the consensus number is greater than 1, and determining that unintentional islanding has been detected when an indication of unintentional islanding is identified from a consensus number of the plurality of UI detection sources during the time window. A method is disclosed that includes performing the above.

[0008] Each transmission from one or more of the plurality of UI detection sources may include a plurality of measurement values, and the method includes determining, for each measurement value of each of the one or more UI detection sources, whether the measurement value meets its respective measurement threshold, determining that an indication of unintentional islanding is identified in the transmission when a threshold number of the plurality of measurement values meet their respective measurement thresholds, where the threshold number is greater than 1, and determining that an indication of unintentional islanding is not identified in the transmission when the threshold number of the plurality of measurement values do not meet their respective measurement thresholds. The plurality of measurement values may include a positive rate of change of frequency and a negative rate of change of frequency. The plurality of measurement values may include a rate of change of the positive sequence component of current and a rate of change of the negative sequence component of current. The plurality of measurement values may include a positive rate of change of frequency, a negative rate of change of frequency, a rate of change of the positive sequence component of current, and a rate of change of the negative sequence component of current.

[0009] This method uses at least one hardware processor to determine whether the first UI detection source among a plurality of UI detection sources is local to or remote from the DER circuit when an indication of unintentional islanding is identified in a transmission from the first UI detection source, and when it is determined that the first UI detection source is local to the DER circuit, to determine whether to perform a detection of unintentional islanding of the DER circuit based on the position of the first UI detection source within the DER circuit, and when it is determined that the first UI detection source is remote from the DER circuit, to perform a detection of unintentional islanding of the DER circuit. Determining whether to perform a detection of unintentional islanding of the DER circuit based on the position of the first UI detection source within the DER circuit includes determining whether the first UI detection source is downstream of a segmentation device within the DER circuit, and when it is determined that the first UI detection source is not downstream of the segmentation device, performing a detection of unintentional islanding of the DER circuit, and when it is determined that the first UI detection source is downstream of the segmentation device, determining whether the segmentation device is in an open state, and when it is determined that the segmentation device is not in an open state, performing a detection of unintentional islanding of the DER circuit, and when it is determined that the segmentation device is in an open state, not performing a detection of unintentional islanding of the DER circuit.

[0010] This method further includes using at least one hardware processor to start a timer representing a time window, perform a detection of unintentional islanding of the DER circuit from the start of the timer, and block a transition to an intentional island of the DER circuit until an unintentional islanding of the DER circuit is detected or until the timer expires.

[0011] The method may further include using at least one hardware processor to initiate a transition of the DER circuit to an intentional island in response to detecting an unintentional islanding of the DER circuit. Initiating a transition of the DER circuit to an intentional island may include preparing the DER circuit for the intentional island. The method may further include using at least one hardware processor to open a common coupling point with the DER circuit after preparing the DER circuit for the intentional island.

[0012] At least one of the plurality of UI detection sources may generate an indication of unintentional islanding using a different UI detection method than another one of the plurality of UI detection sources.

[0013] Each transmission from one or more of the plurality of UI detection sources may include a binary value indicating the presence or absence of unintentional islanding.

[0014] Any of the above methods may be embodied individually or in any combination in an executable software module of a processor-based system, such as a server, and / or in executable instructions stored on a non-transitory computer-readable medium.

[0015] Brief Description of the Drawings Details of the present invention may be partially gathered by considering the accompanying drawings with respect to both its structure and operation, in which like reference numerals refer to like parts.

Brief Description of the Drawings

[0016]

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[0017] Detailed Description In one embodiment, a system, method, and non-transitory computer-readable medium for robust, sensitive, selective, and cyber-secure collaborative UI detection for a DER circuit including a microgrid are disclosed. After reading this description, those skilled in the art will become apparent as to how to implement the present invention in various alternative embodiments and alternative applications. However, while various embodiments of the present invention are described herein, it is understood that these embodiments are presented for purposes of example and illustration only and are not limiting. Accordingly, this detailed description of the various embodiments should not be construed as limiting the scope or breadth of the present invention as set forth in the appended claims.

[0018] Conventional methods of UI detection can be grouped into the following three general categories: passive, active, and remote. Passive UI detection monitors for specific anomalies that indicate islanding conditions in the measurement of voltage and current waveforms. Examples of such measurements include voltage under / over-voltage, rate of change of frequency (ROCOF), and voltage vector shift (VVS). Generally, these passive UI detection methods function because parameters such as voltage, frequency, and phase are disturbed immediately after the loss of connection to a highly rigid high-inertia grid. Passive UI detection methods are simple to implement but have two major drawbacks.

[0019] The first drawback of the passive UI detection method is the existence of a non-detection zone (NDZ). The non-detection zone is the range of the net active power load and the reactive power load that cannot detect the island state. For example, the active power load and the reactive power load in the islanded DER circuit are almost balanced by the DER power supply, and little power is exchanged with the area EPS. As a result, when an island is formed, there is no significant change in the frequency or phase of the voltage waveform in the islanded DER circuit.

[0020] The second drawback of the passive UI detection method is nuisance tripping. Nuisance tripping refers to a scenario where the measured value exceeds the threshold used to detect unintentional islanding as a result of a non-islanding event, causing the island to be falsely indicated. For example, a sudden large change in the load within a microgrid can cause a large change in voltage, thereby accidentally triggering UI detection. Nuisance tripping can have a cascading effect, which can affect the area EPS, as was the case in the 2016 Blue Cut fire event in Southern California. IEEE1547-2018 addresses nuisance tripping by setting ride-through requirements for some common passive UI indicators (e.g., ROCOF and VVS). Under conditions where ride-through is required, nuisance tripping is not permitted.

[0021] In the active UI detection method, the distributed energy resource controls the voltage and / or current of its terminal that competes with the area EPS. Under normal conditions, since the distributed energy resource is very small relative to the bulk grid, this competition does not affect the area EPS. However, when the distributed energy resource is islanded, this competition causes the voltage waveform to deviate from its normal operation and quickly exceed a certain threshold. Examples of active UI detection include active frequency drift, Sandia frequency drift, impedance measurement, and reactive power control.

[0022] In active frequency drift, the distributed energy resource distorts its output current, as a result of which one cycle of the current waveform becomes shorter than the grid voltage period. When the distributed energy resource becomes islanded, the short current cycles rapidly increase the island frequency to exceed the measurement threshold. Therefore, when the island frequency exceeds the measurement threshold, there may be an indication of unintentional islanding.

[0023] Sandia frequency drift improves active frequency drift by adding a feedback loop in which the chopping coefficient is a function of frequency. Sandia frequency drift eliminates the non-detection region of active frequency drift by rapidly driving the island frequency to the measurement threshold when islanding causes a small frequency deviation. Therefore, again, when the island frequency exceeds the measurement threshold, there may be an indication of unintentional islanding. In impedance measurement, the distributed energy resource perturbs its output current signal. When the corresponding perturbation is measured within the voltage signal, the distributed energy resource is islanded. Therefore, when the corresponding perturbation is measured in the voltage signal, there may be an indication of unintentional islanding.

[0024] During operation, when the distributed energy resource generates reactive power that exceeds the local reactive power demand, the excess is exported to the grid via the point of common coupling. In the case of islanding, this excess reactive power can no longer be measured at the point of common coupling. Therefore, in reactive power control, when the difference between the predicted reactive power and the actual reactive power at the point of common coupling exceeds the measurement threshold, there may be an indication of unintentional islanding.

[0025] Active UI detection methods generally have small or no undetected regions, but there are potential problems with power quality. This is especially true for EPSs with high DER penetration. In this case, many distributed energy resources that each independently inject distortion may cause problems, but the effectiveness of the UI detection method is also reduced. Furthermore, active UI detection methods can only be implemented by the distributed energy resources themselves because other components (e.g., relays, microgrid controllers, etc.) cannot directly control the voltage or frequency waveform.

[0026] Remote UI detection methods are based on communication between distributed energy resources or microgrids and upstream management systems such as supervisory control and data acquisition (SCADA) systems for area EPS monitoring and control. Examples of remote UI detection methods include power line carrier signals and transfer trips. Remote UI detection methods can be effective, but are potentially slow and require costly communication overhead compared to UI detection methods that are specific to DER devices and thus do not cost the area EPS operator.

[0027] FIG. 1 illustrates an exemplary DER circuit 130 in which one or more of the disclosed processes may be implemented, according to one embodiment. Grid 110 may be electrically connected to DER circuit 130 via a common coupling point 140. A transformer 120 may be present between grid 110 and common coupling point 140 to convert the voltage level between grid 110 and DER circuit 130. Common coupling point 140 may include a circuit breaker 142 configured to switch between a closed state in which DER circuit 130 is electrically connected to grid 110 and an open state in which DER circuit 130 is electrically disconnected from (or "islanded" from) grid 110 and area EPS (e.g., including transformer 120).

[0028] The DER circuit 130 may include one or more distributed energy resources 150 (e.g., 150A, 150B, and 150C) and one or more loads 160 (e.g., 160A, 160B, 160C, 160D, and 160E). Examples of distributed energy resources 150 include, but are not limited to, photovoltaic cells, synchronous generators, gas turbines, wind turbines, biomass generators, fuel cells, battery energy storage systems (BESS), electric vehicles, and other things that can generate and / or supply power. Examples of loads 160 may include electric vehicles, electrical appliances, machinery, and other things that consume power. The DER circuit 130 may include different types of distributed energy resources 150 or may consist of the same type of distributed energy resources 150. Similarly, the DER circuit 130 may include different types of loads 160 or may consist of the same type of loads 160.

[0029] A plurality of UI detection sources 170 (e.g., 170A, 170B, 170C, 170D, and 170E) may be locally distributed within the DER circuit 130 (e.g., 170B - 170E), and / or remotely distributed external to the DER circuit 130 (e.g., 170A). Each UI detection source 170 may comprise a device designed to continuously or successively measure one or more parameters at a location within an electrical circuit. For example, UI detection source 170A measures a parameter at a point between the transformer 120 and the common connection point 140, and UI detection source 170B measures a parameter at a point on the other side of the common connection point 140, between the common connection point 140 and the remainder of the DER circuit 130. Other UI detection sources 170 (e.g., 170C, 170D, and 170E) may be distributed throughout the remainder of the DER circuit 130. Each UI detection source 170 may measure the same one or more parameters as each of the other UI detection sources 170 at their respective locations, or may measure a set of one or more parameters different from one or more of the other UI detection sources 170. Similarly, each UI detection source 170 may utilize the same UI detection method, or may utilize a UI detection method different from one or more of the other UI detection sources 170. The UI detection sources 170 may be any device capable of measuring and outputting the value of a parameter, including a microgrid controller, a relay, a distributed energy resource 150, etc., and a device dedicated to the detection of an unintentional island.

[0030] Each UI detection source 170 may communicate with the controller 190. For example, each UI detection source 170 may transmit a message or signal to the controller 190 directly or indirectly via wired or wireless communication. For example, each of the UI detection source 170 and the controller 190 may be connected to a network, and the UI detection source 170 may transmit to the controller 190 via the network. The communication between the UI detection source 170 and the controller 190 may be implemented using a digital communication protocol such as the Distributed Network Protocol 3 (DNP3) or the International Electrotechnical Commission (IEC) 61850 standard, or may be based on simple digital or analog input / output. The UI detection source 170 may transmit the value of each measured parameter continuously (e.g., periodically at a predetermined interval), continuously, or in response to a trigger event. The trigger event may include a request from the controller 190, detection of local unintentional islanding in the UI detection source 170 based on the measured parameter, etc. Alternatively, the UI detection source 170 may transmit only when local unintentional islanding is detected in the UI detection source 170, or may continuously or continuously transmit a binary indication of whether local unintentional islanding has been detected in the UI detection source 170. In other words, the UI detection source 170 may simply transmit a message or signal indicating that local unintentional islanding has been detected without including a specific measured parameter. As another alternative, the UI detection source 170 may report the difference between the measured parameter and each measurement threshold instead of the value of the measured parameter itself. This difference value represents the severity of the measured parameter. It should be understood that different UI detection sources 170 may utilize different ones of these communication types, and the controller 190 may be configured to receive and process each type of communication.

[0031] The DER circuit 130 may include one or more segmentation devices 180. Each segmentation device 180 may be configured to switch between a closed state in which two or more segments of the DER circuit 130 are electrically connected to each other and an open state in which two or more segments of the DER circuit 130 are electrically disconnected or segmented from each other. When the segmentation device 180 is in the open state, a local island may be formed within the DER circuit 130. Examples of the segmentation device 180 include a recloser, a circuit breaker, and the like.

[0032] Each segmentation device 180 may communicate with the controller 190. For example, each segmentation device 180 may directly or indirectly send a message or signal to the controller 190 via wired or wireless communication. For example, each of the segmentation device 180 and the controller 190 may be connected to a network, and the segmentation device 180 may send to the controller 190 via the network. The segmentation device 180 may send an indication of a state, such as whether the segmentation device is in the closed state or the open state, to the controller 190 so that the controller 190 can form a determination based on the state of the segmentation device 180.

[0033] As described elsewhere in this specification, the controller 190 that may be included in the SCADA system of the DER circuit 130 monitors transmissions from the UI detection source 170 to identify an unintentional islanding instruction from the UI detection source 170 and triggers a response based on a consensus scheme. In other words, the controller 190 may implement the UI detection and response processes described herein. The response may include controlling the PCC circuit breaker 142 to switch to the open state, thereby disconnecting the DER circuit 130 from all external components including the transformer 120. This control may be referred to as intentional islanding. Thus, the controller 190 may detect an unintentional island based on the consensus within the transmission from the UI detection source 170 and transition the DER circuit to an intentional island in response. The controller 190 may communicate directly with the PCC circuit breaker 142 or may communicate with the PCC circuit breaker 142 via a network to which both the controller 190 and the circuit breaker 142 are connected.

[0034] The DER circuit 130 is shown with a specific arrangement and number of components including the PCC circuit breaker 142, the distributed energy resource 150, the load 160, the UI detection source 170, the segmentation device 180, and the controller 190, but this is merely a non-limiting example for illustrative purposes. It should be understood that the DER circuit 130 may comprise any different arrangement and / or any different number of components. Further, the DER circuit 130 may be connected to one or more other DER circuits, for example, at point A. It should be understood that the DER circuit 130 may be a microgrid or may be included in a microgrid.

[0035] FIG. 2 is a block diagram showing an exemplary wired or wireless system 200 that can be used in connection with the various embodiments described herein. For example, system 200 may be used as one or more of the functions, processes, or methods described herein (e.g., for storing and / or executing software), or in combination therewith, and may represent components of controller 190, UI detection source 170, and / or other processing devices described herein. System 200 can be a server or any conventional personal computer, or any other processor-enabled device capable of wired or wireless data communication. As will be apparent to those skilled in the art, other computer systems and / or architectures may also be used.

[0036] System 200 preferably includes one or more processors 210. The processor 210 may include a central processing unit (CPU). Additional processors may be provided, such as a graphics processing unit (GPU), an auxiliary processor for managing input / output, an auxiliary processor for performing floating point arithmetic, a dedicated microprocessor (e.g., a digital signal processor) having an architecture suitable for fast execution of signal processing algorithms, a slave processor (e.g., a backend processor) subordinate to the main processing system, an additional microprocessor or controller for a dual or multiprocessor system, and / or a coprocessor. Such auxiliary processors may be individual processors or may be integrated with the processor 210. Examples of processors that may be used with system 200 include, but are not limited to, any processor available from Intel Corporation, Santa Clara, California (e.g., Pentium™, Core i7™, Xeon™, etc.), any processor available from Advanced Micro Devices, Incorporated (AMD), Santa Clara, California, any processor available from Apple Inc., Cupertino (e.g., A series, M series, etc.), any processor available from Samsung Electronics Co., Ltd., Seoul, Korea (e.g., Exynos™), any processor available from NXP Semiconductors N.V., Eindhoven, Netherlands, etc.

[0037] Processor 210 is preferably connected to communication bus 205. Communication bus 205 may include a data channel for facilitating information transfer between storage and other peripheral components of system 200. Further, communication bus 205 may provide a set of signals used for communication with processor 210, including a data bus, an address bus, and / or a control bus (not shown). Communication bus 205 may comply with any standard or non-standard bus architecture, such as, for example, an industry standard architecture (ISA), an extended industry standard architecture (EISA), a Micro Channel Architecture (MCA), a peripheral component interconnect (PCI) local bus, an Institute of Electrical and Electronics Engineers (IEEE) published standard such as IEEE 696 / S-100, which includes a general-purpose interface bus (GPIB) of the IEEE, or other bus architectures.

[0038] System 200 preferably includes main memory 215 and may also include secondary memory 220. Main memory 215 provides storage for instructions and data for programs that execute on processor 210, such as any of the software described herein. It should be understood that the programs stored in memory and executed by processor 210 may be written and / or compiled according to any suitable language, including but not limited to C / C++, Java, JavaScript, Perl, Visual Basic,.NET, etc. Main memory 215 is typically semiconductor-based memory such as dynamic random access memory (DRAM) and / or static random access memory (SRAM). Other semiconductor-based memory types include synchronous dynamic random access memory (SDRAM), Rambus dynamic random access memory (RDRAM), ferroelectric random access memory (FRAM (registered trademark)), etc., including read only memory (ROM).

[0039] The secondary memory 220 is a non-transitory computer-readable medium storing computer-executable code (e.g., any of the software disclosed herein) and / or other data. The computer software or data stored in the secondary memory 220 is loaded into the main memory 215 for execution by the processor 210. The secondary memory 220 may include semiconductor-based memories such as, for example, programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable read-only memory (EEPROM), and flash memory (a block-oriented memory similar to EEPROM).

[0040] The secondary memory 220 may optionally include an internal medium 225 and / or a removable medium 230. The removable medium 230 is read and / or written in any well-known manner. The removable storage medium 230 may be, for example, a magnetic tape drive, a compact disc (CD) drive, a digital versatile disc (DVD) drive, other optical drives, a flash memory drive, and the like.

[0041] In an alternative embodiment, the secondary memory 220 may include other similar means for enabling a computer program or other data or instructions to be loaded into the system 200. Such means may include, for example, a communication interface 240 that enables software and data to be transferred from an external storage medium 245 to the system 200. Examples of the external storage medium 245 include an external hard disk drive, an external optical drive, an external magneto-optical drive, and the like.

[0042] As described above, system 200 may include a communication interface 240. The communication interface 240 enables the transfer of software and data between system 200 and an external device (e.g., a printer), a network, or other information sources. For example, computer software or executable code may be transferred from a network server (e.g., platform 110) to system 200 via the communication interface 240. Examples of the communication interface 240 include a built-in network adapter, a network interface card (NIC), a Personal Computer Memory Card International Association (PCMCIA) network card, a card bus network adapter, a wireless network adapter, a Universal Serial Bus (USB) network adapter, a modem, a wireless data card, a communication port, an infrared interface, an IEEE 1394 FireWire, and any other device capable of interfacing system 200 with a network or another computing device.The communication interface 240 preferably implements protocol standards published in the industry, such as Ethernet (registered trademark) IEEE802 standards, Fibre Channel, Digital Subscriber Line (DSL), Asynchronous Digital Subscriber Line (ADSL), Frame Relay, Asynchronous Transfer Mode (ATM), Integrated Digital Services Network (ISDN), Personal Communications Service (PCS), Transmission Control Protocol / Internet Protocol (TCP / IP), Serial Line Internet Protocol / Point to Point Protocol (SLIP / PPP), etc., but may also implement customized or non-standard interface protocols.

[0043] The software and data transferred via the communication interface 240 are generally in the form of telecommunication signals 255. These signals 255 may be provided to the communication interface 240 via a communication channel 250. In one embodiment, the communication channel 250 may be a wired or wireless network, or any of a variety of other communication links. The communication channel 250 carries the signals 255 and can be implemented using various wired or wireless communication means, including, by way of example only, wired or cable, optical fiber, conventional telephone lines, cellular phone links, wireless data communication links, radio frequency ("RF") links, or infrared links.

[0044] Computer-executable code (e.g., a computer program such as the disclosed software) is stored in main memory 215 and / or secondary memory 220. The computer-executable code can also be received via communication interface 240 and stored in main memory 215 and / or secondary memory 220. When such a computer program is executed, it enables system 200 to perform the various functions of the disclosed embodiments described elsewhere herein.

[0045] In this description, the term "computer-readable medium" is used to refer to any non-transitory computer-readable storage medium used to provide computer-executable code and / or other data to or within system 200. Examples of such media include main memory 215, secondary memory 220 (including internal memory 225 and / or removable media 230), external storage media 245, and any peripheral device (including a network information server or other network device) communicatively coupled to communication interface 240. These non-transitory computer-readable media are means for providing software and / or other data to system 200.

[0046] In embodiments implemented using software, the software may be stored on a computer-readable medium and loaded into system 200 via removable media 230, I / O interface 235, or communication interface 240. In such embodiments, the software is loaded into system 200 in the form of an electrical communication signal 255. When the software is executed by processor 210, it preferably causes processor 210 to perform one or more of the processes and functions described elsewhere herein.

[0047] In one embodiment, the I / O interface 235 provides an interface between one or more components of the system 200 and one or more input and / or output devices. Examples of input devices include, but are not limited to, sensors, keyboards, touchscreens or other touch-sensitive devices, cameras, biometric devices, computer mice, trackballs, pen-based pointing devices, and the like. Examples of output devices include, but are not limited to, other processing devices, cathode ray tubes (CRTs), plasma displays, light-emitting diode (LED) displays, liquid crystal displays (LCDs), printers, vacuum fluorescent displays (VFDs), surface-conduction electron-emitter displays (SEDs), field emission displays (FEDs), and the like. In some cases, input and output devices may be combined, such as in the case of a touch panel display (e.g., a smartphone, tablet, or other mobile device).

[0048] The system 200 may also include an optional wireless communication component that facilitates wireless communication via a voice network and / or a data network. The wireless communication component includes an antenna system 270, a wireless system 265, and a baseband system 260. In the system 200, radio frequency (RF) signals are wirelessly transmitted and received by the antenna system 270 under the management of the wireless system 265.

[0049] In one embodiment, the antenna system 270 may include one or more antennas and one or more multiplexers (not shown) that implement a switching function to provide a transmission signal path and a reception signal path to the antenna system 270. In the reception path, the received RF signal can be coupled from the multiplexer to a low-noise amplifier (not shown) that amplifies the received RF signal and transmits the amplified signal to the wireless system 265.

[0050] In an alternative embodiment, the wireless system 265 may include one or more radios configured to communicate via various frequencies. In one embodiment, the wireless system 265 may combine a demodulator (not shown) and a modulator (not shown) in a single integrated circuit (IC). The demodulator and the modulator may be separate components. In the incoming path, the demodulator removes the RF carrier signal leaving the baseband received audio signal transmitted from the wireless system 265 to the baseband system 260.

[0051] The baseband system 260 may be communicatively coupled to the processor 210. The processor 210 may have access to data storage areas 215 and 220. The processor 210 is preferably configured to execute instructions (i.e., computer programs such as the disclosed software) that can be stored in the main memory 215 or the secondary memory 220. The computer program can also be received from the baseband processor 260 and stored in the main memory 210 or the secondary memory 220, or executed upon reception. Such a computer program, when executed, can enable the system 200 to perform the various functions of the disclosed embodiments.

[0052] FIG. 3 illustrates an exemplary process 300 for consensus-based UI detection, according to one embodiment. Process 300 may be implemented by controller 190 within the monitoring control layer of DER circuit 130. Process 300 may be implemented as software executed by one or more processors (e.g., 210) of controller 190. Alternatively, process 300 may be implemented as hardware components (e.g., integrated circuit (IC), application-specific integrated circuit (ASIC), digital signal processor (DSP), field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, etc.). For the sake of clearly exemplifying the compatibility between hardware and software, various sub-processes of process 300 are described herein with respect to their functions. Whether such functions are implemented as hardware or software depends on the specific application and design constraints imposed on the overall system. Those skilled in the art can implement the functions described in various ways for each specific application. Further, the grouping of functions within process 300 is for ease of explanation. In alternative embodiments, these functions can be grouped differently. Further, although process 300 is illustrated with a particular arrangement and order of sub-processes, process 300 may be implemented with fewer, more, or different sub-processes, as well as with different arrangements and / or orders of sub-processes. Further, even if sub-processes are described or illustrated in a particular order, it should be understood that any sub-process that does not depend on the completion of another sub-process may be executed before, after, or in parallel with other independent sub-processes.

[0053] In sub-process 305, the controller 190 monitors transmissions from the UI detection source 170 to identify an indication of unintentional islanding within the transmission. In embodiments where the UI detection source 170 transmits only when an unintentional islanding is detected, an indication of unintentional islanding may be identified whenever a transmission is received from the UI detection source 170. In embodiments where the UI detection source 170 continuously or serially transmits a binary value indicating the presence or absence of unintentional islanding, an indication of unintentional islanding may be identified whenever the binary value indicates the presence of unintentional islanding. In embodiments where the UI detection source 170 continuously or serially transmits the values of one or more parameters, an indication of unintentional islanding may be identified whenever a transmission containing a parameter that meets one or more criteria is received from the UI detection source 170. For example, if the UI detection source 170 transmits a single parameter, an unintentional islanding may be identified from the transmission when the parameter value meets a threshold (e.g., exceeds or is below a threshold depending on the parameter). If the UI detection source 170 transmits multiple parameters, an unintentional islanding may be identified from the transmission when each of the parameter values of a threshold number or percentage of thresholds is met. It should be understood that there are many other means by which an indication of unintentional islanding may be represented and identified in a transmission, and the disclosed embodiments do not depend on any particular means. When a first indication is identified (i.e., "Yes" in sub-process 305), process 300 proceeds to sub-process 310. Otherwise, if the first indication has not yet been identified (i.e., "No" in sub-process 305), process 300 continues to wait for the first indication in sub-process 305.

[0054] In sub-process 310, the controller 190 determines whether a first indication of unintentional islanding identified in sub-process 305 has been received from the remote UI detection source 170. The remote UI detection source 170 can be any UI detection source outside the DER circuit 130, such as the UI detection source 170A between the grid 110 and the common coupling point 140, or a UI detection source within the grid 110 or associated with the grid 110 (e.g., transmitted by the utility distribution control system). In contrast, the local UI detection source 170 can be any UI detection source inside the DER circuit 130, such as the UI detection sources 170B - 170E. An indication of unintentional islanding from the remote UI detection source 170 indicates an external island, while an indication of unintentional islanding from the local UI detection source 170 may be the result of another event, such as a trip of the segmentation device 180 within the DER circuit 130, which does not require the entire DER circuit 130 to transition to an intentional island. If the segmentation device 180 switches to the open state to form an internal island (e.g., as a protection action in response to a non-UI event), this may cause the UI detection sources 170D and 170E downstream of the segmentation device 180 (i.e., on the other side of the segmentation device 180 as the common coupling point 140) to erroneously indicate an unintentional islanding of the DER circuit 130. When a first indication of unintentional islanding is received from the local UI detection source 170 (i.e., "No" in sub-process 310), the process 300 proceeds to sub-process 315. Otherwise, when a first indication of unintentional islanding is received from the remote UI detection source 170 (i.e., "Yes" in sub-process 310), the process 300 proceeds to sub-process 330.

[0055] In sub-process 315, the controller 190 determines whether a first indication of unintentional islanding identified in sub-process 305 was received from a local UI detection source 170 that is downstream of the segmentation device 180. The controller 190 may comprise, or have access to, a memory (e.g., 215 or 220) that stores a representation of the topology of the DER circuit 130. As an example, the representation of the topology may include identifiers of all UI detection sources 170 that are downstream of the segmentation device 180. In the illustrated example, UI detection sources 170D and 170E are downstream of the segmentation device 180, while UI detection sources 170A, 170B, and 170C are upstream of the segmentation device 180. Regardless of the particular representation, the controller 190 may access the representation of the topology to determine whether the UI detection source 170 from which the first indication of unintentional islanding was received is downstream of the segmentation device 180. When the first indication is received from a local UI detection source 170 that is downstream of the segmentation device 180 (i.e., “Yes” in sub-process 315), process 300 proceeds to sub-process 320. Otherwise, when the first indication is received from a local UI detection source 170 that is not downstream of the segmentation device 180 (i.e., “No” in sub-process 315), process 300 proceeds to sub-process 330.

[0056] In subprocess 320, the controller 190 determines whether the segmentation device 180, which is upstream of the UI detection source 170 from which the first indication of unintentional islanding was received, is in an open state. If the segmentation device 180 is in an open state (i.e., "Yes" in subprocess 320), process 300 proceeds to subprocess 325. In this case, the DER circuit 130 is involved in normal protection operations without external islanding. In other words, the controller 190 stops the consensus algorithm when it becomes clear that the first indication of unintentional islanding is an internal event. On the other hand, if the segmentation device 180 is in a closed state (i.e., "No" in subprocess 320), process 300 proceeds to subprocess 330.

[0057] In subprocess 325, the controller 190 resets the consensus-based UI detection function without starting a UI response. In other words, the first indication of unintentional islanding identified in the transmission from the UI detection source 170 downstream of the open segmentation device 180 is ignored or forgotten. The controller 190 returns to subprocess 305 and monitors the transmission from the UI detection source 170 for new first indications of unintentional islanding.

[0058] In sub - process 330, the controller 190 may block the trip, if necessary, based on the first indication of unintentional islanding. For example, if another mechanism configured to trigger control such as the trip of the PCC circuit breaker 142 is within the DER circuit 130 (e.g., within the SCADA system of the DER circuit 130, within an individual UI detection source 170, etc.) based on a single indication of unintentional islanding or based on the detection of unintentional islanding at a single UI detection source 170, the controller 190 may suppress or override this mechanism or control. For example, the controller 190 may issue block commands to all UI detection sources 170 to suppress any control functions so that no individual UI detection source 170 triggers control when the first indication of unintentional islanding is received. Thus, UI - based trips do not occur in the DER circuit 130 until the controller 190 detects unintentional islanding based on consensus. In other words, the DER circuit 130 continues to operate normally until the process 300 detects unintentional islanding based on consensus. In particular, if the first indication of unintentional islanding is a false positive or a malicious cyber - attack, sub - process 330 prevents the false positive or cyber - attack from triggering control within the DER circuit 130. In embodiments where the controller 190 is the only mechanism for triggering such control, sub - process 330 may be omitted.

[0059] Sub - process 330 may be particularly applicable when the distributed energy resource 150 includes an embedded UI detection function. For example, anti - islanding is a standard function in modern distributed energy resources 150, but typically it is internal and has no exposed communication interface to an external system. Thus, it may be impossible for the controller 190 to access the UI detection measurements and signals within the distributed energy resource 150. In other words, the controller 190 may not be able to utilize the UI detection function of the distributed energy resource 150 in the consensus algorithm. In this case, to solve at least two problems, the UI detection function of the distributed energy resource 150 should be completely blocked. First, the anti - islanding function inside the distributed energy resource 150 is fast and autonomous, but the consensus algorithm depends on some delay between the first instance of UI detection and power - off to build a consensus. The sub - process 330 may prevent the distributed energy resource 150 from powering off until a consensus is reached and as long as a consensus is not reached. Second, since distributed energy resources 150 can control their voltage and current waveforms, they are more likely to use an active UI detection method. However, without a connection to a stiff, high - inertia grid 110 to absorb or attenuate the waveform distortion introduced by the active UI detection method, the power quality in the islanded DER circuit 130 may degrade. By blocking these active UI detection methods, the sub - process 330 may prevent this degradation of power quality.

[0060] In subprocess 335, the controller 190 starts a timer to determine when a pre-determined time window expires since the time when the first indication of unintentional islanding was received. Further, in subprocess 340, a counter is initialized (e.g., set to a value of 1 representing the reception of the first indication of unintentional islanding). Until the timer expires, any additional indication of unintentional islanding is counted to build a consensus. If the timer expires without a consensus being obtained (i.e., "Yes" in subprocess 345), process 300 proceeds to subprocess 325 to reset the consensus-based UI detection function. Otherwise, if the timer has not yet expired (i.e., "No" in subprocess 345), process 300 continues to wait for a consensus in subprocess 350.

[0061] In subprocess 350, the controller 190 monitors transmissions from the UI detection source 170 to identify new indications of unintentional islanding in the transmissions. It should be understood that the transmission monitoring in subprocess 350 can be the same or similar to the transmission monitoring in subprocess 305, except that the reception of a new indication in subprocess 350 adds to the consensus building, whereas the reception of a new indication in subprocess 305 starts the consensus building. When a new indication is identified (i.e., "Yes" in subprocess 350), the controller 190 increments the counter in subprocess 355 and proceeds to subprocess 360. Otherwise, if no new indication has been identified yet (i.e., "No" in subprocess 350), process 300 continues to wait for either the timer to expire or a consensus to be reached. In one embodiment, the increment of the counter may be replaced by a more complex calculation that combines, for example, the severity representation in the indication (e.g., the difference between a measured value and its respective measurement threshold) to form an aggregated or composite representation of the overall severity state.

[0062] In sub - process 360, the controller 190 determines whether a consensus has been reached. This determination in sub - process 360 may utilize any one of a variety of potential ways to build a consensus (i.e., more than one indication of unintentional islanding) before detecting an unintentional island. Next, some of such consensus - based ways will be described. However, the described ways are non - limiting, and it should be understood that any different consensus - based way may be utilized in sub - process 360. The advantage of the disclosed embodiments is that it is necessary to identify multiple indications of unintentional islanding before performing any control (e.g., tripping of the PCC circuit breaker 142) that would interfere with the normal operation of the DER circuit 130, thereby achieved by suppressing or reducing the impact of false positives or cyber - attacks on the DER circuit 130. Thus, in each way, unintentional islanding is not detected while an indication is received from a number of UI detection sources 170 that is less than the consensus number and / or while a number of indications received from the UI detection sources 170 is less than the consensus number. Conversely, unintentional islanding is detected when an indication is received from the UI detection sources 170 of the consensus number and / or when a number of indications of the consensus number is received from the UI detection sources 170. This consensus number may be determined from a predetermined count, percentage, etc., and can be set according to the specific design goals of the implementation (e.g., the desired confidence level). However, it should be understood that the consensus number should be set to require more than one UI detection source 170 and / or more than one indication.

[0063] In the first approach, a consensus may be reached when an indication of unintentional islanding is received from different UI detection sources 170 with a threshold number or a threshold percentage (i.e., “Yes” in sub - process 360). In the illustrated example, there are five UI detection sources 170A, 170B, 170C, 170D, 170E. In this case, the counter may be incremented each time a new indication is identified from a UI detection source 170 that was not previously visible. If the threshold number is 3 (or the threshold percentage is 60%), a consensus is reached when the counter reaches 3. This is an example of a one - stage consensus - based approach.

[0064] In the second approach, a consensus may be reached when an indication of unintentional islanding with a threshold number or a threshold percentage is received. This approach may be applicable when a single UI detection source 170 transmits measurement values of one or more parameters, each of which may individually indicate unintentional islanding. For example, measurement values of a parameter that each meet a respective predetermined measurement threshold may be identified as an indication of unintentional islanding. In the illustrated example, there are five UI detection sources 170A, 170B, 170C, 170D, 170E. Assume that each UI detection source 170 transmits measurement values of four parameters that may each individually indicate unintentional islanding (e.g., when each meets its respective threshold), for a total of 20 potentially unintentional islanding indications. In this case, the counter may be incremented each time a measurement value from any UI detection source 170 meets its respective measurement threshold. If the threshold number is 15 (or the threshold percentage is 75%), a consensus is reached when the counter reaches 15. This is another example of a one - stage consensus - based approach.

[0065] In the third approach, consensus may be reached when an indication of unintentional islanding is identified from transmissions of different UI detection sources 170 of a threshold number or threshold percentage (i.e., “Yes” in sub-process 360), and the indication of unintentional islanding is not identified in transmissions from the UI detection source 170 unless the measured value of the threshold number or threshold percentage indicates an unintentional island. This approach may be applicable when a single UI detection source 170 transmits measured values of a plurality of parameters, each of which may individually indicate unintentional islanding. For example, measured values of parameters that each meet a respective measurement threshold may be identified as an indication of unintentional islanding. In the illustrated example, there are five UI detection sources 170A, 170B, 170C, 170D, and 170E. Assume that each UI detection source 170 transmits measured values of four parameters, each of which may individually indicate unintentional islanding (e.g., when each meets its respective threshold). In this case, the counter may be incremented each time a measured value of the threshold number from a previously unseen UI detection source 170 meets its respective measurement threshold. If the threshold number for different UI detection sources 170 is three (or the threshold percentage is 60%) and the threshold number for measurement is three (or the threshold percentage is 75%), reaching a count of three indicates reaching consensus and that at least three measured values reported by each of the three UI detection sources meet their respective measurement thresholds. This is an example of a two-step consensus-based approach.

[0066] In particular, the UI detection source 170 that monitors the measured values of a plurality of parameters may be configured to locally determine whether the measured values of the threshold number or the threshold percentage meet their respective thresholds. In this case, each UI detection source 170 may send an indication of unintentional islanding only if the UI detection source 170 locally determines that the measured values of the threshold number or the threshold percentage meet their respective thresholds. In this case, the controller 190 may determine that a consensus has been reached when the UI detection source 170 of the threshold number or the threshold percentage sends an indication of unintentional islanding. Technically, this is an example of a two-stage consensus-based approach, but from the perspective of the controller 190, this is a one-stage consensus-based approach that can be implemented by the controller 190 in the same way as the approach described initially.

[0067] In a fourth approach, a consensus may be reached when different UI detection sources 170 with different threshold numbers or threshold percentages indicate an unintentional island and the measured values of the threshold numbers or threshold percentages across all UI detection sources 170 indicate an unintentional island (i.e., “Yes” in sub - process 360). This approach may be applicable when a single UI detection source 170 transmits measured values of multiple parameters, each of which may individually indicate unintentional islanding. For example, measured values of parameters that meet respective predetermined measurement thresholds may be identified as an indication of unintentional islanding. In the illustrated example, there are five UI detection sources 170A, 170B, 170C, 170D, 170E. Assume that each UI detection source 170 transmits measured values of four parameters, each of which may individually indicate unintentional islanding (e.g., when each meets its respective threshold). In this case, there may be a first counter that tracks the number of different UI detection sources 170 that transmit measured values indicating unintentional islanding, and a second counter that tracks the total number of measured values indicating unintentional islanding transmitted by any UI detection source 170. If the threshold number for different UI detection sources 170 is 3 (or the threshold percentage is 60%) and the threshold number for measurement is 15 (or the threshold percentage is 75%), a consensus is reached when the first counter reaches 3 and the second counter reaches 15. This is another example of a two - stage consensus - based approach.

[0068] In a fifth approach, consensus may be reached when an indication of unintentional islanding is identified from transmissions of UI detection sources 170 with different threshold numbers or threshold percentages (i.e., “Yes” in sub-process 360), where the measured value of the threshold number or threshold percentage indicates an unintentional island and the measured values of the threshold number or threshold percentage across all UI detection sources 170 do not indicate an unintentional island. The indication of unintentional islanding is not identified in transmissions from UI detection sources 170 unless the measured value of the threshold number or threshold percentage indicates an unintentional island and the measured values of the threshold number or threshold percentage across all UI detection sources 170 do not indicate an unintentional island. This approach may be applicable when a single UI detection source 170 transmits measured values of multiple parameters, each of which may individually indicate unintentional islanding. For example, the measured value of a parameter that meets each respective measurement threshold may be identified as an indication of unintentional islanding. In the illustrated example, there are five UI detection sources 170A, 170B, 170C, 170D, and 170E. Assume that each UI detection source 170 transmits measured values of four parameters, each of which may individually indicate unintentional islanding (e.g., when each respective threshold is met). In this case, a first counter may be incremented each time a measured value of the threshold number from a previously unseen UI detection source 170 meets their respective measurement thresholds, and a second counter may be incremented each time a measured value from any UI detection source 170 meets its respective threshold. When the threshold number of different UI detection sources 170 is 3 (or the threshold percentage is 60%), the threshold number of measured values from UI detection sources 170 is 3 (or the threshold percentage is 75%), and the threshold number of measured values across all UI detection sources 170 is 16 (or the threshold percentage is 80%), consensus is reached when the first counter reaches 3 (indicating that each of at least three UI detection sources has reported at least three measured values that meet their respective measurement thresholds) and the second counter reaches 16. This is an example of a three-stage consensus-based approach.

[0069] In any embodiment where the UI detection source 170 can utilize different UI detection methods, a hybrid approach may be used. For example, some UI detection sources 170 may send locally determined indications of unintentional islanding or measurements of a single parameter, while other UI detection sources 170 may send measurements of multiple parameters. In this case, the controller 190 may increment a counter each time it identifies an indication of unintentional islanding in a transmission, but the controller 190 may identify each indication in a different way depending on the UI detection source 170 from which the transmission was received. For example, when a locally determined indication of unintentional islanding is received, the controller 190 may increment the counter. When a transmission consisting of a measurement of a single parameter is received, the controller 190 may increment the counter only if the measurement meets its respective measurement threshold. When a transmission containing measurements of multiple parameters is received, the controller 190 may increment the counter only if a number or percentage of those threshold measurements meet their respective measurement thresholds. Regardless of how indications from different UI detection sources 170 are identified, the controller 190 may determine that consensus has been reached when the counter reaches a consensus threshold (i.e., "Yes" in sub-process 360).

[0070] In a sixth approach, consensus may be reached if the overall severity of the indication reaches a consensus threshold (i.e., “Yes” in sub - process 360). This approach may be applicable when the UI detection source 170 transmits the difference between each measured value and its respective measurement threshold, which represents the severity of the measured parameter. Alternatively, the UI detection source 170 may transmit the measured values, and the controller 190 may calculate the difference between the measured values and their respective measurement thresholds. In either case, the differences may be combined in some way and the result may be compared to the consensus threshold. In particular, in this approach, the counter is not a simple incremental counter. Rather, sub - process 355 may include a more complex calculation that combines the aggregated difference or other representation of aggregated severity with the difference of the new indication of unintentional islanding identified in sub - process 350. As a result, the consensus is not based on whether the UI detection source 170 agrees that an unintentional island has occurred. Rather, the consensus is based on whether the DER circuit 130 as a whole has reached an aggregated state of severity indicating unintentional islanding.

[0071] When the UI detection source 170 uses different UI detection methods, the sixth method can be further improved. For example, consider two UI detection sources 170 that use two different UI detection methods with two different non-detection regions. When an unintentional island occurs, the net power change may be within the non-detection region of the first UI detection source among the UI detection sources 170 but outside the non-detection region of the second UI detection source among the UI detection sources 170. In this case, the first UI detection source 170 does not provide an indication of unintentional islanding, and the second UI detection source 170 provides an indication of unintentional islanding. If the consensus algorithm only knows that the second UI detection source 170 indicates an unintentional island while the first UI detection source 170 does not indicate an unintentional island, the UI response is not triggered. However, if the consensus algorithm knows that the second UI detection source 170 shows measured parameters that far exceed its respective measurement threshold, and the first UI detection source 170 shows measured parameters that are not exactly at its respective measurement threshold but are very close, the aggregated severity state may be sufficient to trigger the UI response.

[0072] In any of the methods that utilize the measured values of one or more parameters, the parameters may include any parameter that can indicate an unintentional island. Examples of such parameters include, but are not limited to, voltage under / over voltage, frequency under / over frequency, rate of change of frequency, voltage vector shift, rate of change of frequency with respect to power (df / dP), total harmonic distortion (THD), rate of change of symmetrical components, etc. It should be understood that a single UI detection source 170 may measure one or any combination of a plurality of these parameters, potentially all of them, as well as other parameters not specifically described herein.

[0073] In the case of voltage deficiency / overvoltage or frequency deficiency / overfrequency, without a highly rigid high-inertia grid 110, the voltage and / or frequency of an unintentional island may increase or decrease. This is particularly likely when there is an imbalance between the power generation by the distributed energy resource 150 and the load 160 inside the island. Therefore, when the voltage or frequency exceeds a first measurement threshold or falls below a second measurement threshold, an unintentional island may be indicated.

[0074] Regarding the rate of change of frequency, in the absence of a high-inertia grid 110, the frequency within an unintentional island may change rapidly due to the imbalance between the power generated by the distributed energy resource 150 and the load 160 within the island. Therefore, when the rate of change of frequency (i.e., the derivative of frequency) exceeds a measurement threshold, an unintentional island may be indicated. The positive and negative rates of change of frequency may be calculated as two separate parameters or as a single parameter.

[0075] Regarding the voltage vector shift, a sudden loss of the voltage reference from the grid 110 may cause a step change in the phase of the voltage within the DER circuit 130. Therefore, the voltage signal period may be tracked, and when the difference between the measured signal period and the reference exceeds a measurement threshold, an unintentional island may be indicated.

[0076] Regarding the rate of change of frequency with respect to power, under normal grid connection conditions, the change in the power output by the distributed energy resource 150 does not result in a significant change in the frequency within the DER circuit 130. However, without a connection to the high-inertia grid 110, a step change in the output power may cause a large change in the frequency. Therefore, the value of the rate of change of frequency with respect to the rate of change of power (i.e., df / dP) may be tracked, and when this value exceeds a measurement threshold, an unintentional island may be indicated.

[0077] Regarding total harmonic distortion, when the DER circuit 130 loses its connection to the grid 110, the high-frequency components of the current output by the distributed energy resource 150 may experience an increase in impedance, and as a result, the total harmonic distortion of the voltage increases. Therefore, if the total harmonic distortion exceeds a measurement threshold, an unintentional islanding may be indicated.

[0078] Regarding the rate of change of symmetrical components (e.g., positive and negative sequences), an unintentional islanding may disrupt the symmetry of the three-phase current waveform. Therefore, if the rate of change of the magnitude of the positive or negative sequence component exceeds a measurement threshold, an unintentional islanding may be indicated.

[0079] Regardless of the specific method and / or measurement values used, if a consensus has been reached (i.e., "Yes" in sub-process 360), process 300 proceeds to sub-process 365. Otherwise, if no consensus has been reached (i.e., "No" in sub-process 360), process 300 continues to wait until either the timer expires or a consensus is reached.

[0080] In sub-process 365, the controller 190 may start preparing for islanding. The preparation for islanding may include any steps necessary to transition the DER circuit 130 to an intentional island (i.e., before opening the PCC circuit breaker 142). Such steps may include, but are not limited to, managing the load 160 for islanding preparation, changing the control mode of the DER circuit 130 or one or more distributed energy resources 150 within the DER circuit 130 from grid-following to grid-forming, providing voltage and frequency references, and configuring various components of the DER circuit 130, such as performing load shedding if necessary.

[0081] In sub - process 370, the controller 190 may initiate the transition of the PCC circuit breaker 142 from the closed state to the open state. For example, the controller 190 may communicate directly or indirectly (e.g., via a network) with the PCC circuit breaker 142 and send a control command or signal to open the PCC circuit breaker 142. After the PCC circuit breaker 142 transitions to the open state representing an intentional island, the DER circuit 130 may operate in islanding mode. The process 300 may end until the PCC circuit breaker 142 transitions back to the closed state, at which point the process 300 may resume. In other words, the process 300 may operate at any time when the PCC circuit breaker 142 is in the closed state and may stop operating at any time when the PCC circuit breaker 142 is in the open state.

[0082] In particular, when the PCC circuit breaker 142 is opened, the area EPS including the transformer 120 is no longer energized by the DER circuit 130 in accordance with the applicable grid code. The DER circuit 130 may continue to operate in islanding mode.

[0083] FIG. 4 illustrates an exemplary state diagram 400 for consensus - based UI detection according to one embodiment. The state diagram 400 may be implemented by the controller 190 within the monitoring and control layer of the DER circuit 130. The state diagram 400 is illustrated with a particular arrangement of states, but the state diagram 400 may be implemented with fewer, more, or different states and different arrangements of states.

[0084] In state 410, while the DER circuit 130 is connected to the area EPS, it operates normally (e.g., corresponding to sub-process 305). If an unintentional islanding instruction is received from the local UI detection source 170 during normal operation 410 (e.g., corresponding to "No" in sub-process 310), the controller 190 transitions to topology analysis 420 to find the source of the instruction (e.g., corresponding to sub-processes 315 and 320). If an unintentional islanding instruction is received from the remote UI detection source 170 during normal operation 410 (e.g., corresponding to "Yes" in sub-process 310), the controller 190 transitions to the consensus algorithm 430 (e.g., corresponding to sub-processes 330 - 360). At this point, the controller 190 still doesn't know whether an actual island has been formed or whether the UI detection logic has been tripped for another reason, such as a false positive or a nuisance trip due to a cyber attack.

[0085] From the topology analysis 420, if the UI detection indicates an internal island, the controller 190 transitions to the protection operation 440, which may involve reconfiguring the DER circuit 130. When the protection operation 440 is complete, the controller 190 transitions from the protection operation 440 to the normal operation 410. On the other hand, if the UI detection indicates an external island, the controller 190 transitions from the topology analysis 420 to the consensus algorithm 430.

[0086] From the consensus algorithm 430, if consensus is not reached within a predetermined time window (for example, corresponding to "Yes" in sub-process 345), the controller 190 transitions to return to the normal operation 410. Otherwise, if consensus is reached within the predetermined time window (for example, corresponding to "Yes" in sub-process 360), the controller 190 transitions from the consensus algorithm 430 to the islanding preparation 450 (for example, corresponding to sub-process 365). When the islanding preparation 450 is completed, the controller 190 transitions from the islanding preparation 450 to the islanding operation 460 (for example, corresponding to sub-process 370), where the DER circuit 130 is disconnected from the area EPS. When the islanding operation 460 is completed (for example, the electrical connection to the grid 110 is restored), the controller 190 transitions from the islanding operation 460 to the normal operation 410.

[0087] The grid code applicable to the DER circuit 130 may limit the period during which the DER circuit 130 must detect and respond to an unintentional island. For example, the IEEE 1547 standard requires the DER circuit 130 to detect and stop powering within 2 seconds from the formation of an unintentional island. Therefore, the controller 190 should be able to execute the process 300 within this time constraint defined by the grid code.

[0088] Figure 5 illustrates an exemplary timing of the process 300 for consensus-based UI detection according to an embodiment where the time constraint specified by the applicable grid code is 2 seconds. As shown, after the first indication of intentional islanding is identified (for example, sub-process 305), the controller 190 starts the execution of the consensus algorithm (including, for example, sub-processes 330 - 360). When consensus is reached (for example, "Yes" in sub-process 360), the controller 190 starts the transition of the DER circuit to an intentional island (for example, sub-processes 365 and 370).

[0089] The consensus algorithm and transition should be able to be performed within a specified period (e.g., 2 seconds). Therefore, the length of the timer used in the consensus algorithm (e.g., started in subprocess 335) should be set to be long enough to capture sufficient indications that meet the consensus threshold for unintentional islanding, but short enough to allow for a transition to an intentional island within the applicable time constraints while taking into account latencies in communication, processing, etc. For example, the length of the timer may be calculated by subtracting from the time constraint the maximum duration required for the UI detection source 170 to communicate an indication of unintentional islanding to the controller 190, subtracting the maximum duration required for a transition to an intentional island, and potentially subtracting a buffer duration. For example, if the time constraint is 2 seconds, communication between the UI detection source 170 and the controller 190 requires a maximum of 50 milliseconds, and a transition to an intentional island requires a maximum of 1 second, the length of the timer may be set to 950 milliseconds.

[0090] The disclosed consensus-based or collaborative UI detection has many advantages over conventional UI detection based on individual UI detection sources (e.g., monitored only at a common junction point). For example, a redundant and consensus-based approach that uses multiple UI detection sources 170 distributed across multiple locations inside and / or outside the DER circuit 130 to trigger a UI response when the number of positive indications reaches a threshold improves the sensitivity of the DER circuit 130 (i.e., the ability to correctly detect unintentional islanding regardless of the magnitude of the disturbance), the selectivity (i.e., the ability to ignore disturbances not caused by unintentional islanding), and the resilience to cyberattacks (i.e., the ability to ignore malicious false positives). Further, in one embodiment, different types of UI detection sources 170 may be utilized to introduce diversity or robustness into the consensus-based UI detection process.

[0091] The sensitivity of any single UI detection method is limited by the UI detection method and the location of the UI detection source 170 within the DER circuit 130. By utilizing multiple UI detection sources 170 and / or multiple parameters, process 300 can improve the overall sensitivity of UI detection for the DER circuit 130, as it ensures that the most sensitive UI detection method operates during UI detection for a given situation. For example, the use of multiple UI detection sources 170 and / or multiple parameters that may have overlapping detection zones can effectively reduce or eliminate non-detection regions present in conventional passive UI detection methods. Thus, process 300 allows conventional passive UI detection methods to detect unintentional islands.

[0092] Events other than unintentional islanding can cause disturbances that may generate an indication of unintentional islanding under a particular UI detection method. For example, voltage-based methods may trip due to a large load change, while frequency-based methods may ignore the same disturbance. Process 300 can improve the selectivity of UI detection as the use of multiple UI detection sources 170 and / or multiple parameters prevents such nuisance trips. In particular, since a consensus is required, a single false positive cannot trigger a UI response. The type and placement of the UI detection sources 170 may be selected to prevent all such false positives from triggering a UI response. Thus, process 300 can prevent nuisance trips as required by the applicable grid code.

[0093] Process 300 can also improve the resilience of UI detection against cyberattacks. For example, the use of multiple UI detection sources 170 increases redundancy and prevents a compromised UI detection source 170 from triggering a UI response. In particular, the consensus requirement prevents a set of one or a few compromised UI detection sources 170 from using a false positive indication to trigger a UI response for the entire DER circuit 130. In other words, if a compromised UI detection source 170 generates a false positive, and attempts to trigger a UI response (e.g., to take the DER circuit 130 offline), process 300 prevents a cyberattack by requiring that unintentional islanding be confirmed by one or more different UI detection sources 170 before triggering a UI response. To succeed in a cyberattack, a malicious actor would need to compromise a threshold number of UI detection sources 170. In particular, the cyber resilience of the DER circuit 130 may be scaled up by increasing the number of UI detection sources 170 within the DER circuit 170 and / or the threshold number of UI detection sources 170 required for consensus.

[0094] In particular, process 300 is also computationally inexpensive (i.e., does not require significant computational resources). Thus, process 300 can be incorporated into the existing controller 190 of the DER circuit 130. Additionally, process 300 can be executed within the time constraints imposed by the applicable grid code. During experiments with several different scenarios, process 300 was able to detect a true unintentional island within 0.3 - 0.4 seconds, well within the 2-second time constraint imposed by IEEE 1547 - 2018, while successfully ignoring false positives.

[0095] As described elsewhere in this specification, the UI detection source 170 may measure one or more parameters. In one embodiment, one or more UI detection sources 170, potentially including all, measure a plurality of parameters such as the positive frequency change rate, the negative frequency change rate, the change rate of the positive sequence component, and / or the change rate of the negative sequence component. Each measured parameter represents a distinct UI detection function by which an unintentional island may be detected. In particular, each measured parameter may be compared to its respective measurement threshold, and if the measured parameter meets (e.g., exceeds the threshold in the case of the four exemplary parameters above) its respective measurement threshold, it may be used to indicate the possibility of an unintentional island.

[0096] The respective measurement thresholds for each UI detection function (i.e., the measured parameter) may be adjusted to strike an appropriate balance between sensitivity and selectivity. In particular, different measurement thresholds may be used for different UI detection sources 170, for example, based on their locations within the DER circuit 130. Further, in a manner that requires a threshold number or percentage of measurements to meet each respective measurement threshold, the threshold may also be set to strike an appropriate balance between sensitivity and selectivity. Further, the consensus threshold number or percentage of UI detection sources 170 that must receive an indication of unintentional islanding before an unintentional island is detected may also be set to strike an appropriate balance among sensitivity, selectivity, and cyber resilience. In other words, there are multiple steps that can be adjusted based on experiments (e.g., simulations) and design goals (e.g., applicable time constraints) to strike an appropriate balance among sensitivity, selectivity, and / or cyber resilience.

[0097] The following table illustrates one particular example of the measurement thresholds of different exemplary parameters (i.e., the positive and negative frequency change rates, the change rate of the positive sequence current, and the change rate of the negative sequence current) measured by each of the UI detection sources 170A - 170E within the DER circuit 130.

[0098]

Table 1

[0099] In one embodiment, different consensus algorithms may be utilized according to one or more characteristics of the DER circuit 130 (e.g., load state, net steady-state power, etc.). For example, when the net steady-state power of the common connection point 140, which is an intersection point, is outside the entire non-detection region, the first consensus algorithm may be utilized in the process 300. Also, when the net steady-state power of the common connection point 140, which is an intersection point, is inside the entire non-detection region, the second consensus algorithm may be utilized in the process 300. The entire non-detection region may be pre-identified through system studies of various non-detection regions in the passive UI detection method utilized by the UI detection source 170. The first and second consensus algorithms may differ in various aspects including, but not limited to, whether the trip is blocked in the subprocess 330, various measurement thresholds (e.g., different measurement thresholds based on the load state), consensus thresholds, consensus-based schemes, etc. For example, in the first consensus algorithm (i.e., utilized when the power is outside the entire non-detection region), the internal active UI detection method of the distributed energy resource 150 may be blocked in the subprocess 330, but in the second consensus algorithm (i.e., utilized when the power is inside the entire non-detection region), the subprocess 330 may be omitted so that no blockage occurs. Therefore, the distributed energy resource 150 may continue to exercise their internal active UI detection methods in situations where the passive UI detection method may not be able to detect unintentional islanding.

[0100] The foregoing description of the disclosed embodiments is provided to enable a person of ordinary skill in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles described herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the description and drawings presented herein represent the presently preferred embodiments of the invention and are therefore representative of the broad subject matter contemplated by the invention. It should be understood that the scope of the invention is to fully encompass other embodiments that may become apparent to those skilled in the art and accordingly the scope of the invention is not limited thereby.

[0101] Combinations described herein such as "at least one of A, B, or C", "one or more of A, B, or C", "at least one of A, B, and C", "one or more of A, B, and C", and "A, B, C, or any combination thereof" include any combination of A, B, and / or C and may include multiple A's, multiple B's, or multiple C's. Specifically, combinations such as "at least one of A, B, or C", "one or more of A, B, or C", "at least one of A, B, and C", "one or more of A, B, and C", and "A, B, C, or any combination thereof" may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, and any such combination may include one or more members of its components A, B, and / or C. For example, a combination of A and B may include one A and multiple B's, multiple A's and one B, or multiple A's and multiple B's.

Claims

1. A method for detecting unintentional islanding (UI) of at least one distributed energy resource (DER) circuit, using at least one hardware processor to monitor transmissions from a plurality of UI detection sources to identify an indication of unintentional islanding from the plurality of UI detection sources, and detecting unintentional islanding of the DER circuit by determining that unintentional islanding is not detected when an indication of unintentional islanding is identified from less than a consensus number of the plurality of UI detection sources during a time window, the consensus number being greater than 1, and determining that unintentional islanding is detected when an indication of unintentional islanding is identified from the consensus number of the plurality of UI detection sources during the time window implemented thereby A method comprising

2. each of the transmissions from one or more of the plurality of UI detection sources includes a plurality of measurements, and the method determines, for each of the plurality of measurements in the transmission from each of the one or more UI detection sources, whether the measurement meets its respective measurement threshold, determining that an indication of unintentional islanding is identified in the transmission when a threshold number of the plurality of measurements meet their respective measurement thresholds, the threshold number being greater than 1, and determining that an indication of unintentional islanding is not identified in the transmission when the threshold number of the plurality of measurements do not meet their respective measurement thresholds The method according to claim 1, comprising identifying by

3. The method according to claim 2, wherein the plurality of measurements includes a positive rate of change of frequency and a negative rate of change of frequency.

4. The method according to claim 2, wherein the plurality of measurements includes a rate of change of the positive sequence component of current and a rate of change of the negative sequence component of current.

5. The method according to claim 2, wherein the plurality of measurements includes a positive rate of change of frequency, a negative rate of change of frequency, a rate of change of the positive sequence component of current, and a rate of change of the negative sequence component of current.

6. Using the at least one hardware processor, if the indication of unintentional islanding is identified in the transmission from a first UI detection source among the plurality of UI detection sources, determining whether the first UI detection source is local to or remote from the DER circuit; if it is determined that the first UI detection source is local to the DER circuit, determining whether to perform the detection of unintentional islanding of the DER circuit based on the location of the first UI detection source within the DER circuit; if it is determined that the first UI detection source is remote from the DER circuit, performing the detection of unintentional islanding of the DER circuit The method according to claim 1, comprising.

7. Determining whether to perform the detection of unintentional islanding of the DER circuit based on the location of the first UI detection source within the DER circuit is determining whether the first UI detection source is downstream of a segmentation device within the DER circuit; if it is determined that the first UI detection source is not downstream of the segmentation device, performing the detection of unintentional islanding of the DER circuit; if it is determined that the first UI detection source is downstream of the segmentation device, determining whether the segmentation device is in an open state; if it is determined that the segmentation device is not in the open state, performing the detection of unintentional islanding of the DER circuit, and if it is determined that the segmentation device is in the open state, not performing the detection of unintentional islanding of the DER circuit The method according to claim 6, comprising.

8. Using the at least one hardware processor, if the indication of unintentional islanding is identified in the transmission from a first UI detection source among the plurality of UI detection sources, starting a timer representing the time window, and performing the detection of unintentional islanding of the DER circuit from the start of the timer Unless and until an unintentional islanding of the DER circuit is detected before the timer expires, block an intentional transition of the DER circuit to an island. The method according to claim 1, further comprising.

9. The method according to claim 1, further comprising using the at least one hardware processor to initiate an intentional transition of the DER circuit in response to detection of an unintentional islanding of the DER circuit.

10. The method according to claim 9, wherein initiating an intentional transition of the DER circuit to an island includes preparing the DER circuit for the intentional island.

11. The method according to claim 10, further comprising using the at least one hardware processor to open a common connection point with the DER circuit after preparing the DER circuit for the intentional island.

12. The method according to claim 1, wherein at least one of the plurality of UI detection sources generates the indication of unintentional islanding using a different UI detection method than another one of the plurality of UI detection sources.

13. The method according to claim 1, wherein each of the transmissions from one or more of the plurality of UI detection sources includes a binary value indicating the presence or absence of unintentional islanding.

14. At least one hardware processor; When executed by the at least one hardware processor, Monitor transmissions from a plurality of UI detection sources to identify an indication of unintentional islanding from the plurality of UI detection sources, and Detect an unintentional islanding of the DER circuit, Determine that unintentional islanding has not been detected when an indication of unintentional islanding is identified from fewer than the consensus number of the plurality of UI detection sources during a time window, the consensus number being greater than 1, and Determine that unintentional islanding has been detected when an indication of unintentional islanding is identified from the consensus number of the plurality of UI detection sources during the time window Software configured to perform by A control system comprising A system comprising.

15. The system according to claim 14, further comprising the plurality of UI detection sources.

16. The system of claim 15, further comprising the DER circuit, wherein the plurality of UI detection sources are dispersed at different positions with respect to the DER circuit.

17. The system of claim 16, wherein the DER circuit is a microgrid including one or more distributed energy resources.

18. The system of claim 15, wherein at least one of the plurality of UI detection sources generates the indication of unintentional islanding using a different UI detection method from another one of the plurality of UI detection sources.

19. Each of the transmissions from one or more of the plurality of UI detection sources includes a plurality of measurement values, and the software determines the indication of unintentional islanding in the transmission from each of the one or more UI detection sources by for each of the plurality of measurement values, determining whether the measurement value meets its respective measurement threshold, when the plurality of measurement values of the threshold number meet their respective measurement thresholds, determining that an indication of unintentional islanding is identified in the transmission, wherein the threshold number is greater than 1, and when the plurality of measurement values of the threshold number do not meet their respective measurement thresholds, determining that an indication of unintentional islanding is not identified in the transmission and is further configured to identify by. The system of claim 14.

20. A non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to monitor transmissions from a plurality of UI detection sources to identify an indication of unintentional islanding from the plurality of UI detection sources, and detect unintentional islanding of the DER circuit by determining that unintentional islanding is not detected while an indication of unintentional islanding is identified from fewer than a consensus number of the plurality of UI detection sources during a time window, wherein the consensus number is greater than 1, and determining that unintentional islanding is detected when an indication of unintentional islanding is identified from the consensus number of the plurality of UI detection sources during the time window and perform A non-transitory computer-readable medium that causes it to perform.

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