Coordinated unplanned islanding detection for robustness and network security of microgrids

Abstract

An unplanned islanding phenomenon (UI) of a distributed energy source (DER) circuit may keep a regional power system (EPS) external to the DER circuit energized. Accordingly, UI detection methods have been developed to detect unplanned islanding phenomena and trigger UI responses. However, each UI detection method has various defects. Thus, a consensus-based UI detection process is disclosed that establishes a consensus from a plurality of UI detection sources, optionally implementing different UI detection methods. The redundancy in the consensus-based UI detection process provides robust, sensitive, selective and network secure UI detection for the entire DER circuit. For example, a consensus-based UI detection process may eliminate or reduce non-detection zones, avoid misinformation, hinder network attacks, and / or the like.

Description

[0001] Government licensing rights

[0002] This invention was made with U.S. Government support under Contract No. DE-OE0000896 awarded by the U.S. Department of Energy. The U.S. Government has certain rights in this invention. Technical Field

[0003] Embodiments described herein relate generally to coordinated islanding detection, and more particularly to coordinated unplanned islanding (UI) detection that is robust, sensitive, selective, and cyber-secure for distributed energy resource (DER) circuits, such as microgrids. Background Art

[0004] Grid codes typically require that interconnections with distributed energy resources must accurately and quickly detect unplanned islands and stop energizing them. 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 in accordance with the Institute of Electrical and Electronics Engineers (IEEE) Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Power Systems (IEEE 1547-2018) or similar grid codes, the UI response requirements are the same as for independent distributed energy resources. IEEE 1547-2018 defines unplanned islands as island scenarios in which DER circuits energize a portion of the regional power system (EPS) through a common coupling point. However, as used herein, the term "unplanned island" may be understood to refer to any scenario in which one or more distributed energy resources become unplannedly isolated from the rest of the power system and continue to power so that they may energize components of the power system.

[0005] Typical operation of a microgrid as a planned island involves disconnection from the regional EPS along predefined electrical boundaries (e.g., points of common coupling). If an island is formed outside of these electrical boundaries so as to include both the microgrid and electrical system components in the regional EPS that are not part of the microgrid, the microgrid is required to detect the unplanned island and stop energizing the non-microgrid components. For example, if a fault causes the microgrid and a transformer located upstream of the point of common coupling with the microgrid to become isolated from the main grid, the microgrid must quickly stop energizing the transformer.

[0006] Mango et al., "Overview of Anti-Islanding Algorithms for PV Systems. Part I: Passive Methods" (12th International Conference on Power Electronics and Motion Control, 2006, pp. 1878-1883) provides an overview of some existing anti-islanding algorithms. The present disclosure is directed to overcoming one or more of the problems found in current state-of-the-art algorithms. Summary of the invention

[0007] Thus, systems, methods, and non-transitory computer-readable media for robust, sensitive, selective, and cyber-secure coordinated UI detection for DER circuits, including microgrids, are disclosed. It is an object of an embodiment to establish consensus from multiple UI detection sources using one or more redundancy levels before triggering a UI response, such as transitioning to a planned islanding in which a regional EPS is de-energized. It is a further object of some embodiments to eliminate or reduce non-detection zones within the UI detection method. It is a further object of some embodiments to prevent false positives asserted by a UI detection source from triggering a UI response. It is a further object of some embodiments to prevent a compromised UI detection source from supporting a cyber attack aimed at islanding DER circuits, such as a microgrid.

[0008] In an embodiment, a method for detecting unplanned islanding (UI) of a distributed energy resource (DER) circuit is disclosed, the method comprising using at least one hardware processor to: monitor transmissions from a plurality of UI detection sources to identify indications of unplanned islanding from the plurality of UI detection sources; and perform detection of unplanned islanding of the DER circuit by: determining that unplanned islanding is not detected when indications of unplanned islanding are identified from a plurality of UI detection sources less than a consensus number during a time window, wherein the consensus number is greater than one; and determining that unplanned islanding is detected when indications of unplanned islanding are identified from a plurality of UI detection sources greater than a consensus number during the time window.

[0009] Transmissions from one or more of a plurality of UI detection sources may each include a plurality of measurements, and the method may include identifying an indication of unplanned islanding in transmissions from each of the one or more UI detection sources by: for each of the plurality of measurements, determining whether the measurement satisfies a corresponding measurement threshold; determining an indication that unplanned islanding is identified in the transmission when a threshold number of the plurality of measurements satisfies the corresponding measurement threshold, wherein the threshold number is greater than one; and determining an indication that unplanned islanding is not identified in the transmission when a threshold number of the plurality of measurements does not satisfy the corresponding measurement threshold. The plurality of measurements may include a positive rate of change of frequency and a negative rate of change of frequency. The plurality of measurements may include a rate of change of a positive sequence component of current and a rate of change of a negative sequence component of current. The plurality of measurements may include a positive rate of change of frequency, a negative rate of change of frequency, a rate of change of a positive sequence component of current, and a rate of change of a negative sequence component of current.

[0010] The method may include: when an indication of unplanned islanding is identified in a transmission from a first UI detection source among the plurality of UI detection sources, using the at least one hardware processor to: determine whether the first UI detection source is local to the DER circuit or remote from the DER circuit; when it is determined that the first UI detection source is local to the DER circuit, determine whether to perform detection of unplanned islanding on the DER circuit based on the location 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, perform detection of unplanned islanding on the DER circuit. Determining whether to perform unplanned islanding detection of the DER circuit based on the position of the first UI detection source in the DER circuit may include: determining whether the first UI detection source is downstream of a segmenting device in the DER circuit; when it is determined that the first UI detection source is not downstream of the segmenting device, performing unplanned islanding detection of the DER circuit; and when it is determined that the first UI detection source is downstream of the segmenting device: determining whether the segmenting device is in a disconnected state, and when it is determined that the segmenting device is not in a disconnected state, performing unplanned islanding detection of the DER circuit; and when it is determined that the segmenting device is in a disconnected state, not performing unplanned islanding detection of the DER circuit.

[0011] The method may further include: when an indication of unplanned islanding is identified in a transmission from a first UI detection source among the plurality of UI detection sources, using the at least one hardware processor to: start a timer representing a time window and perform detection of unplanned islanding of the DER circuit from the time the timer is started; and prevent transition of the DER circuit to planned islanding unless and until unplanned islanding of the DER circuit is detected before expiration of the timer.

[0012] The method may further include: in response to detecting unplanned islanding of the DER circuit, initiating transition of the DER circuit to planned islanding using the at least one hardware processor. Initiating transition of the DER circuit to planned islanding may include preparing the DER circuit for planned islanding. The method may further include: after preparing the DER circuit for planned islanding, disconnecting a point of common coupling with the DER circuit using the at least one hardware processor.

[0013] At least one of the plurality of UI detection sources may generate the indication of unintentional islanding using a different UI detection method than another of the plurality of UI detection sources.

[0014] The transmissions from one or more of the plurality of UI detection sources may each include a binary value indicating the presence or absence of unintended islanding.

[0015] Any of the above methods may be embodied, alone or in any combination, in an executable software module of a processor-based system (such as a server) and / or in executable instructions stored in a non-transitory computer-readable medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The details of the invention, both as to its structure and operation, may be gleaned in part by examination of the accompanying drawings, in which like reference numerals refer to like parts, and in which:

[0017] Figure 1 illustrates an example DER circuit according to an embodiment, for which one or more of the disclosed processes may be implemented;

[0018] Figure 2 An example processing system is illustrated according to an embodiment by which one or more of the processes described herein may be performed;

[0019] Figure 3 illustrates an example process for consensus-based UI detection according to an embodiment;

[0020] Figure 4 illustrates an example state diagram for consensus-based UI detection according to an embodiment; and

[0021] Figure 5 An example timing of a process for consensus-based UI detection according to an embodiment is illustrated. DETAILED DESCRIPTION

[0022] In an embodiment, a system, method, and non-transitory computer-readable medium for robust, sensitive, selective, and cyber-secure coordinated UI detection for DER circuits, including microgrids, is disclosed. After reading this description, it will become apparent to those skilled in the art how to implement the invention in various alternative embodiments and alternative applications. However, although various embodiments of the invention will be described herein, it should be understood that these embodiments are presented by way of example and illustration only and not by way of limitation. Thus, this detailed description of the various embodiments should not be construed as limiting the scope or breadth of the invention as set forth in the appended claims.

[0023] Conventional UI detection methods can be grouped into three general categories: passive; active; and remote. Passive UI detection monitors specific anomalies in measurements of voltage and current waveforms that indicate islanding conditions. Examples of such measurements include undervoltage / overvoltage, rate of change of frequency (ROCOF), and voltage vector shift (WS). Generally speaking, these passive UI detection methods work because parameters such as voltage, frequency, and phase experience disturbances immediately after losing connection to a rigid, high-inertia grid. While passive UI detection methods are simple to implement, they have two major disadvantages.

[0024] The first disadvantage of passive UI detection methods is the presence of a non-detection zone (NDZ). The non-detection zone is a range of net active and reactive power loads within which an islanding condition cannot be detected. For example, the active and reactive power loads in an islanded DER circuit may be nearly balanced by the DER sources, such that little power is exchanged within the regional EPS. As a result, there will be no significant changes in the frequency and phase of the voltage waveform in the islanded DER circuit when an island is formed.

[0025] The second disadvantage of passive UI detection methods is improper tripping. An improper trip refers to a scenario where islanding is erroneously indicated because the measurement exceeds the threshold for detecting unplanned islanding due to a non-islanding event. For example, a sudden large change in load within a microgrid may cause a large change in voltage, thereby erroneously triggering a UI detection. Improper tripping can have a cascading effect that can have a devastating impact on a regional EPS, as was the case with the 2016 Blue Cut fire in Southern California. IEEE 1547-2018 addresses improper tripping by setting ride-through requirements for several common passive UI indicators, such as ROCOF and VVS. In situations where ride-through would be required, improper tripping is not allowed.

[0026] In active UI detection methods, the DER will control the voltage and / or current at its terminals, which conflicts with the regional EPS. Under normal conditions, this conflict has no effect on the regional EPS because the DER is very small relative to the larger grid. However, when the DER is islanded, this conflict forces 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.

[0027] In active frequency drift, the DER distorts its output current so that one cycle of the current waveform is shorter than the grid voltage cycle. When the DER becomes islanded, the short current cycle will force the islanding frequency to rise quickly and exceed the measurement threshold. Therefore, when the islanding frequency exceeds the measurement threshold, it can indicate unplanned islanding.

[0028] Sandia Frequency Drift improves on active frequency drift by adding a feedback loop where the chopping factor is a function of frequency. When islanding causes small frequency deviations, Sandia Frequency Drift eliminates the non-detection zone of active frequency drift by quickly driving the islanding frequency to the measurement threshold. Thus, again, when the islanding frequency exceeds the measurement threshold, unplanned islanding can be indicated.

[0029] In impedance measurement, the DER applies a disturbance to its output current signal. If a corresponding disturbance is measured in the voltage signal, the DER is islanded. Therefore, unintended islanding can be indicated when a corresponding disturbance is measured in the voltage signal.

[0030] During operation, if the reactive power generated by the distributed energy resource (s) exceeds the local reactive power demand, the excess reactive power will be exported to the grid through the point of common coupling. In the case of islanding, this excess reactive power will no longer be measured at the point of common coupling. Therefore, in reactive power control, unplanned islanding can be indicated when the difference between the expected reactive power and the actual reactive power at the point of common coupling exceeds a measurement threshold.

[0031] While active UI detection methods typically have small or no non-detection zones, they present potential problems in terms of power quality. This is especially true in EPS with high DER penetration. In this case, many DERs (each injecting distortion independently) can cause problems and also make UI detection methods less effective. In addition, active UI detection methods can only be implemented by the DERs themselves, as other components (e.g., relays, microgrid controllers, etc.) cannot directly control the voltage or frequency waveforms.

[0032] Remote UI detection methods are based on communication between the distributed energy resources or microgrid and the upstream management system of the regional EPS, such as a supervisory control and data acquisition (SCADA) system. Examples of remote UI detection methods include power line carrier signals and inter-hopping. While remote UI detection methods can be effective, they are potentially slow and require expensive communication overhead, especially relative to UI detection methods that are native to the DER devices and therefore cost nothing to the operator of the regional EPS.

[0033] Figure 1An example DER circuit 130 is illustrated for which one or more of the disclosed processes may be implemented, according to an embodiment. The grid 110 may be electrically connected to the DER circuit 130 via a point of common coupling 140. A transformer 120 may be present between the grid 110 and the point of common coupling 140 to transform voltage levels between the grid 110 and the DER circuit 130. The point of common coupling 140 may include a circuit breaker 142 configured to switch between a closed state, in which the DER circuit 130 is electrically connected to the grid 110, and an open state, in which the DER circuit 130 is electrically disconnected or "islanded" from the grid 110 and the regional EPS (e.g., including the transformer 120).

[0034] 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 electricity. Examples of loads 160 may include electric vehicles, appliances, machinery, and other things that consume electricity. DER circuit 130 may include different types of distributed energy resources 150 or be composed of the same type of distributed energy resources 150. Similarly, DER circuit 130 may include different types of loads 160 or be composed of the same type of loads 160.

[0035] Multiple UI detection sources 170 (e.g., 170A, 170B, 170C, 170D, and 170E) may be distributed locally within DER circuit 130 (e.g., 170B-170E) and / or remotely outside DER circuit 130 (e.g., 170A). Each UI detection source 170 may include a device designed to continuously or continuously measure one or more parameters at a location within the circuit. For example, UI detection source 170A measures parameter(s) at a point between transformer 120 and point of common coupling 140, and UI detection source 170B measures parameter(s) at a point on the other side of point of common coupling 140 between point of common coupling 140 and the remainder of DER circuit 130. Other UI detection sources 170 (e.g., 170C, 170D, and 170E) may be distributed throughout the remainder of DER circuit 130. Each UI detection source 170 may measure the same one or more parameters as each other UI detection source 170 at its respective location, or may measure a different set or parameters than one or more other UI detection sources 170. Similarly, each UI detection source 170 may utilize the same UI detection method, or may utilize a different UI detection method than one or more other UI detection sources 170. The UI detection source 170 may be any device capable of measuring and outputting a value of a parameter, including a microgrid controller, a relay, a distributed energy resource 150, and / or the like, as well as a device dedicated to detecting unplanned islanding.

[0036] 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, the UI detection source 170 and the controller 190 may each 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 performed using a digital communication protocol (such as 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., regularly at predefined intervals), continuously, or in response to a triggering event. The triggering event may include a request from the controller 190, a local detection of an unplanned islanding phenomenon at the UI detection source 170 based on (multiple) measured parameters, and / or the like. Alternatively, the UI detection source 170 may transmit only when an unplanned islanding phenomenon is detected locally at the UI detection source 170, or may continuously or continuously transmit a binary indication of whether an unplanned islanding phenomenon is detected locally at the UI detection source 170. In other words, the UI detection source 170 may simply transmit a message or signal indicating that an unplanned islanding phenomenon has been detected without including a specific (multiple) measured parameter. As another alternative, the UI detection source 170 may report the difference between the measured parameter and the corresponding measurement threshold value, rather than the value of the measured parameter itself. The difference value indicates the severity of the measured parameter. It should be understood that different UI detection sources 170 may utilize different types of these communication types, and the controller 190 may be configured to receive and process each type of communication.

[0037] The DER circuit 130 may include one or more sectionalizing devices 180. Each sectionalizing device 180 may be configured to switch between a closed state, in which two or more sections of the DER circuit 130 are electrically connected to each other, and an open state, in which two or more sections of the DER circuit 130 are electrically disconnected or sectionalized from each other. When the sectionalizing device 180 is in the open state, a local island may be formed within the DER circuit 130. Examples of sectionalizing devices 180 include reclosers, circuit breakers, and the like.

[0038] Each segmenting device 180 may communicate with the controller 190. For example, each segmenting device 180 may transmit messages or signals to the controller 190 directly or indirectly via wired or wireless communications. For example, the segmenting device(s) 180 and the controller 190 may each be connected to a network, and the segmenting device(s) 180 may transmit to the controller 190 via the network. The segmenting device 180 may transmit an indication of a state (such as whether the segmenting device is in a closed state or an open state) to the controller 190, so that the controller 190 can make a decision based on the state of the segmenting device 180.

[0039] The controller 190 (which may be included in the SCADA system of the DER circuit 130) monitors the transmissions from the UI detection source 170 to identify any indication of unplanned islanding from the UI detection source 170 and triggers a response based on a consensus scheme, as described elsewhere herein. In other words, the controller 190 may implement the process of UI detection and response described herein. The response may include controlling the PCC circuit breaker 142 to switch to an open state, thereby disconnecting the DER circuit 130 from all external components (including the transformer 120). This control may be referred to as planned islanding. Therefore, the controller 190 may detect unplanned islanding based on a consensus within the transmissions from the UI detection source 170, and responsively transition the DER circuit to a planned island. The controller 190 may communicate directly with the PCC circuit breaker 142, or may communicate with the PCC circuit breaker 142 via a network connecting both the controller 190 and the circuit breaker 142.

[0040] Although DER circuit 130 is depicted as having a certain arrangement and number of components (including PCC circuit breaker 142, distributed energy resources 150, load 160, UI detection source 170, segmentation device 180, and controller 190), this is merely a non-limiting example for illustration purposes. It should be understood that DER circuit 130 may include any different arrangement and / or any different number of components. In addition, DER circuit 130 may be connected to one or more other DER circuits, such as at point A. It should be understood that DER circuit 130 may be a microgrid or may be included in a microgrid.

[0041] Figure 2is a block diagram illustrating an example wired or wireless system 200 that may be used in conjunction with the various embodiments described herein. For example, the system 200 may be used as or in conjunction with one or more of the functions, processes, or methods described herein (e.g., to store and / or execute software), and may represent a component of the controller 190, the UI detection source 170, and / or other processing devices described herein. The system 200 may be a server or any conventional personal computer, or any other processor-enabled device capable of wired or wireless data communications. Other computer systems and / or architectures may also be used, as will be apparent to those skilled in the art.

[0042] The system 200 preferably includes one or more processors 210. The processor(s) 210 may include a central processing unit (CPU). Additional processors may be provided, such as a graphics processing unit (GPU), an auxiliary processor to manage input / output, an auxiliary processor to perform floating point math operations, a dedicated microprocessor with an architecture suitable for fast execution of signal processing algorithms (e.g., a digital signal processor), a slave processor subordinate to the main processing system (e.g., a back-end processor), an additional microprocessor or controller for a dual processor system or a multi-processor system, and / or a coprocessor. Such auxiliary processors may be discrete processors or may be integrated with the processor 210. Examples of processors that may be used with the system 200 include, but are not limited to, any processor available from Intel Corporation of Santa Clara, California (e.g., Pentium TM 、Core i7 TM , Xeon TM any processor available from Advanced Micro Devices, Incorporated (AMD) of Santa Clara, California, any processor available from Apple Inc. of Cupertino (e.g., A-series, M-series, etc.), any processor available from Samsung Electronics Co., Ltd. of Seoul, South Korea (e.g., Exynos TM ), any processor available from NXP Semiconductors NV of Eindhoven, the Netherlands, and / or the like.

[0043] The processor 210 is preferably connected to a communication bus 205. The communication bus 205 may include a data channel for facilitating the transfer of information between the storage devices and other peripheral components of the system 200. In addition, the communication bus 205 may provide a set of signals for communicating with the processor 210, including a data bus, an address bus, and / or a control bus (not shown). The communication bus 205 may include any standard or non-standard bus architecture, such as, for example, a bus architecture that conforms to the following: Industry Standard Architecture (ISA), Extended Industry Standard Architecture (EISA), Micro Channel Architecture (MCA), Peripheral Component Interconnect (PCI) local bus, standards published by the Institute of Electrical and Electronics Engineers (IEEE) (including IEEE 488 General Purpose Interface Bus (GPIB), IEEE 696 / S-100, and / or the like).

[0044] The system 200 preferably includes a main memory 215 and may also include a secondary memory 220. The main memory 215 provides storage of instructions and data for programs executed on the processor 210 (such as any software discussed herein). It should be understood that the programs stored in the memory and executed by the processor 210 can be written and / or compiled according to any suitable language (including but not limited to C / C++, Java, JavaScript, Perl, Visual Basic, .NET, etc.). The main memory 215 is typically a semiconductor-based memory, such as a dynamic random access memory (DRAM) and / or a static random access memory (SRAM). Other semiconductor-based memory types include, for example, synchronous dynamic random access memory (SDRAM), Rambus dynamic random access memory (RDRAM), ferroelectric random access memory (FRAM), etc., including read-only memory (ROM).

[0045] The secondary memory 220 is a non-transitory computer-readable medium having computer executable code (e.g., any software disclosed herein) and / or other data stored thereon. The computer software or data stored on the secondary memory 220 is read into the main memory 215 for execution by the processor 210. The secondary memory 220 may include, for example, semiconductor-based memories such as programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable read-only memory (EEPROM), and flash memory (block-oriented memory similar to EEPROM).

[0046] Optionally, the secondary storage 220 may include internal media 225 and / or removable media 230. Reading from and / or writing to the removable media 230 is performed in any known manner. The removable storage medium 230 may be, for example, a tape drive, a compact disk (CD) drive, a digital versatile disk (DVD) drive, other optical drives, a flash memory drive, and / or the like.

[0047] In alternative embodiments, secondary memory 220 may include other similar devices for allowing computer programs or other data or instructions to be loaded into system 200. Such devices may include, for example, a communication interface 240 that allows software and data to be transferred from an external storage medium 245 to system 200. Examples of external storage medium 245 include an external hard drive, an external optical drive, an external magneto-optical drive, and / or the like.

[0048] As mentioned above, the system 200 may include a communication interface 240. The communication interface 240 allows software and data to be transferred between the system 200 and an external device (e.g., a printer), a network, or other information source. For example, computer software or executable code may be transferred from a network server (e.g., platform 110) to the 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 cardbus network adapter, a wireless network adapter, a universal serial bus (USB) network adapter, a modem, a wireless data card, a communications port, an infrared interface, an IEEE 1394 FireWire, and any other device capable of interfacing the system 200 with a network or another computing device. The communication interface 240 preferably implements industry-published protocol standards, such as Ethernet IEEE 802 standards, Fibre Channel, Digital Subscriber Line (DSL), Asynchronous Digital Subscriber Line (ADSL), Frame Relay, Asynchronous Transfer Mode (ATM), Integrated Services Digital 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 custom or non-standard interface protocols.

[0049] The software and data transferred via the communication interface 240 are typically in the form of electrical communication signals 255. These signals 255 may be provided to the communication interface 240 via the communication channel 250. In an embodiment, the communication channel 250 may be a wired or wireless network (e.g., any kind of other communication link). The communication channel 250 carries the signals 255 and may be implemented using a variety of wired or wireless communication means, including wire or cable, fiber optics, a conventional telephone line, a cellular telephone link, a wireless data communication link, a radio frequency ("RF") link, or an infrared link, to name a few examples.

[0050] Computer executable code (e.g., computer programs, such as the disclosed software) is stored in the main memory 215 and / or the secondary memory 220. The computer executable code may also be received via the communication interface 240 and stored in the main memory 215 and / or the secondary memory 220. Such computer programs, when executed, enable the system 200 to perform various functions of the disclosed embodiments as described elsewhere herein.

[0051] 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 the 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 devices (including network information servers or other network devices) communicatively coupled to communication interface 240. These non-transitory computer-readable media are means for providing software and / or other data to system 200.

[0052] In embodiments implemented using software, the software may be stored on a computer-readable medium and loaded into the system 200 by way of the removable medium 230, the I / O interface 235, or the communication interface 240. In such embodiments, the software is loaded into the system 200 in the form of electrical communication signals 255. The software, when executed by the processor 210, preferably causes the processor 210 to perform one or more of the processes and functions described elsewhere herein.

[0053] In an 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. Example input devices include, but are not limited to, sensors, keyboards, touch screens or other touch-sensitive devices, cameras, biometric sensing devices, computer mice, trackballs, pen-based pointing devices, and / or 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 / or the like. In some cases, input and output devices may be combined, such as in the case of a touch panel display (e.g., in a smartphone, tablet, or other mobile device).

[0054] System 200 may also include optional wireless communication components that facilitate wireless communication over a voice network and / or a data network. The wireless communication components include antenna system 270, radio system 265, and baseband system 260. In system 200, radio frequency (RF) signals are transmitted and received over the air by antenna system 270 under the management of radio system 265.

[0055] In an embodiment, antenna system 270 may include one or more antennas and one or more multiplexers (not shown) that perform switching functions to provide transmit and receive signal paths for antenna system 270. In the receive path, a received RF signal may be coupled from the multiplexer to a low noise amplifier (not shown) that amplifies the received RF signal and sends the amplified signal to radio system 265.

[0056] In an alternative embodiment, the radio system 265 may include one or more radios configured to communicate over various frequencies. In an embodiment, the radio system 265 may combine a demodulator (not shown) and a modulator (not shown) in one integrated circuit (IC). The demodulator and modulator may also be separate components. In the incoming path, the demodulator strips off the RF carrier signal, leaving behind a baseband receive audio signal that is sent from the radio system 265 to the baseband system 260.

[0057] The baseband system 260 may be communicatively coupled to the processor(s) 210. The processor(s) 210 may access data storage areas 215 and 220. The processor(s) 210 are preferably configured to execute instructions (i.e., computer programs, such as the disclosed software) which may be stored in the main memory 215 or the secondary memory 220. Computer programs may also be received from the baseband processor 260 and stored in the main memory 210 or the secondary memory 220, or executed upon receipt. Such computer programs, when executed, may enable the system 200 to perform various functions of the disclosed embodiments.

[0058] Figure 3An example process 300 for consensus-based UI detection according to an embodiment is illustrated. The process 300 may be implemented by the controller 190 within the supervisory control layer of the DER circuit 130. The process 300 may be implemented as software executed by one or more processors (e.g., 210) of the controller 190. Alternatively, the process 300 may be implemented as a hardware component (e.g., an integrated circuit (IC), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, etc.). In order to clearly illustrate the interchangeability of hardware and software, the sub-processes of the process 300 are described herein in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. A skilled person may implement the described functionality in different ways for each specific application. In addition, the grouping of functions within the process 300 is for ease of description. In alternative embodiments, these functions may be grouped differently. In addition, although process 300 is illustrated as having a certain arrangement and order of subprocesses, process 300 can be implemented with fewer, more, or different subprocesses and with subprocesses arranged and / or ordered differently. In addition, it should be understood that any subprocess that does not depend on the completion of another subprocess can be performed before, after, or in parallel with other independent subprocesses, even if the subprocesses are described or illustrated in a particular order.

[0059] In subprocess 305, the controller 190 monitors transmissions from the UI detection source 170 to identify indications of unplanned islanding within the transmissions. In embodiments where the UI detection source 170 transmits only when unplanned islanding is detected, an indication of unplanned islanding may be identified each time a transmission is received from the UI detection source 170. In embodiments where the UI detection source 170 continuously or continuously transmits a binary value indicating the presence or absence of unplanned islanding, an indication of unplanned islanding may be identified each time the binary value indicates the presence of unplanned islanding. In embodiments where the UI detection source 170 continuously or continuously transmits values ​​of parameter(s), an indication of unplanned islanding may be identified each time a transmission including parameter(s) that meets one or more criteria is received from the UI detection source 170. For example, in the case where the UI detection source 170 transmits a single parameter, unplanned islanding may be identified from the transmission when the parameter value meets a threshold (e.g., exceeds the threshold or falls below the threshold, depending on the parameter). In the case where the UI detection source 170 transmits multiple parameters, unplanned islanding can be identified from the transmission when a threshold number or a threshold percentage of parameter values ​​each meet the corresponding threshold. It should be understood that there are many other ways in which indications of unplanned islanding can be represented and identified in transmissions, and the disclosed embodiments are not dependent on any particular way. When the first indication is identified (i.e., "yes" in subprocess 305), process 300 continues to subprocess 310. Otherwise, if the first indication has not yet been identified (i.e., "no" in subprocess 305), process 300 continues to wait for the first indication in subprocess 305.

[0060] In subprocess 310, controller 190 determines whether a first indication of unplanned islanding identified in subprocess 305 is received from a remote UI detection source 170. Remote UI detection source 170 may be any UI detection source 170 external to DER circuit 130 (such as UI detection source 170A between grid 110 and point of common coupling 140), or a UI detection source within grid 110 or otherwise associated with the grid (e.g., transmitted by a utility distribution control system). In contrast, local UI detection source 170 may be any UI detection source 170 internal to DER circuit 130, such as UI detection sources 170B-170E. Whereas the indication of unplanned islanding from a remote UI detection source 170 indicates external islanding, the indication of unplanned islanding from a local UI detection source 170 may be the result of another event, such as tripping of a sectionalizing device 180 within DER circuit 130, which does not require the entire DER circuit 130 to transition to planned islanding. If segmentation device 180 switches to the disconnected state, for example, to form an internal island (e.g., as a protective action in response to a non-UI event), this may cause UI detection sources 170D and 170E downstream of segmentation device 180 (i.e., on the other side of segmentation device 180, such as point of common coupling 140) to erroneously indicate unplanned islanding of DER circuit 130. When a first indication of unplanned islanding is received from local UI detection source 170 (i.e., "No" in sub-process 310), process 300 proceeds to sub-process 315. Otherwise, when a first indication of unplanned islanding is received from remote UI detection source 170 (i.e., "Yes" in sub-process 310), process 300 proceeds to sub-process 330.

[0061] In subprocess 315, the controller 190 determines whether the first indication of unplanned islanding identified in subprocess 305 is received from a local UI detection source 170 downstream of the segmenting device 180. The controller 190 may include or access a memory (e.g., 215 or 220) storing 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 downstream of the segmenting device 180. In the illustrated example, UI detection sources 170D and 170E are downstream of the segmenting device 180, while UI detection sources 170A, 170B, and 170C are upstream of the segmenting 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 unplanned islanding was received is downstream of the segmenting device 180. If the first indication is received from a local UI detection source 170 downstream of the segmentation device 180 (i.e., "yes" in subprocess 315), the process 300 continues to subprocess 320. Otherwise, if the first indication is received from a local UI detection source 170 not downstream of the segmentation device 180 (i.e., "no" in subprocess 315), the process 300 continues to subprocess 330.

[0062] In subprocess 320, the controller 190 determines whether the segmenting device 180 upstream of the UI detection source 170 from which the first indication of unplanned islanding was received is in an open state. If the segmenting device 180 is in an open state (i.e., "yes" in subprocess 320), the process 300 proceeds to subprocess 325. In this case, the DER circuit 130 is engaged in normal protection operation without external islanding. In other words, when the first indication of unplanned islanding is that an internal event becomes apparent, the controller 190 stops the consensus algorithm. On the other hand, if the segmenting device 180 is in a closed state (i.e., "no" in subprocess 320), the process 300 proceeds to subprocess 330.

[0063] In sub-process 325, the controller 190 resets the consensus-based UI detection function without initiating any UI response. In other words, the first indication of unplanned islanding identified in the transmission from the UI detection source 170 downstream of the disconnected segmenting device 180 is ignored or forgotten. The controller 190 returns to sub-process 305 to monitor the transmission from the UI detection source 170 for a new first indication of unplanned islanding.

[0064] In subprocess 330, if desired, the controller 190 may prevent tripping based on the first indication of unplanned islanding. For example, if there is another mechanism within the DER circuit 130 (e.g., within the SCADA system of the DER circuit 130, within each UI detection source 170, etc.) that is configured to trigger control (such as tripping the PCC circuit breaker 142 based on a single indication of unplanned islanding or based on detection of unplanned islanding at a single UI detection source 170), the controller 190 may inhibit or override the mechanism or control. For example, upon receiving the first indication of unplanned islanding, the controller 190 may issue a prevent command to all UI detection sources 170 to inhibit any control function so that no individual UI detection source 170 triggers control. Therefore, no UI-based tripping will occur in the DER circuit 130 until the controller 190 detects unplanned islanding based on consensus. In other words, the DER circuit 130 will continue to operate normally until the process 300 detects unplanned islanding based on consensus. Notably, if the first indication of unintended islanding is a false alarm or a malicious cyber attack, subprocess 330 will prevent the false alarm or cyber attack from triggering any controls within DER circuit 130. In embodiments where controller 190 is the only mechanism for triggering such controls, subprocess 330 may be omitted.

[0065] Subprocess 330 may be particularly applicable when the distributed energy source 150 includes an embedded UI detection function. For example, anti-islanding is a standard function in modern distributed energy sources 150, but is typically internal and has no communication interface exposed to external systems. Therefore, it may not be possible for the controller 190 to access UI detection measurements and signals within the distributed energy source 150. In other words, the controller 190 may not be able to utilize the UI detection function of the distributed energy source 150 in the consensus algorithm. In this case, the UI detection function of the distributed energy source 150 should be completely blocked to solve at least two problems. First, the internal anti-islanding function of the distributed energy source 150 is fast and autonomous, while the consensus algorithm relies on some delay between the first instance of UI detection and the cessation of power-on to establish consensus. Subprocess 330 may prevent the distributed energy source 150 from stopping power-on until and unless consensus is reached. Second, because the distributed energy sources 150 are able to control their voltage and current waveforms, they are more likely to use active UI detection methods. However, without connection to the rigid high inertia grid 110 to absorb or attenuate waveform distortion introduced by active UI detection methods, power quality may be degraded in the islanded DER circuit 130. By blocking these active UI detection methods, the subprocess 330 can prevent such degradation of power quality.

[0066] In subprocess 335, the controller 190 starts a timer to determine when a predetermined time window expires from the receipt of the first indication of an unplanned islanding phenomenon. Additionally, in subprocess 340, a counter is initialized (e.g., to a value of 1, which indicates that the first indication of an unplanned islanding phenomenon has been received). Any additional indications of unplanned islanding phenomena will not be counted toward establishing consensus until the timer expires. When the timer expires and consensus has not been achieved (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 expired (i.e., "no" in subprocess 345), process 300 continues to wait for consensus in subprocess 350.

[0067] In subprocess 350, the controller 190 monitors transmissions from the UI detection source 170 to identify new indications of unplanned islanding within those transmissions. It should be understood that the monitoring of transmissions in subprocess 350 may be the same or similar to the monitoring of transmissions in subprocess 305, except that the receipt of a new indication in subprocess 305 initiates consensus building, while the receipt of a new indication in subprocess 350 increases consensus building. When a new indication is identified (i.e., "yes" in subprocess 350), the controller 190 increments a counter in subprocess 355 and proceeds to subprocess 360. Otherwise, if a new indication has not been identified (i.e., "no" in subprocess 350), the process 300 continues to wait for the timer to either expire or reach consensus. In an embodiment, the increment of the counter may be replaced by a more complex calculation, such as combining the severity level representations in the indications (e.g., the difference between the measured value and the corresponding measurement threshold) into an aggregate or composite representation of the overall state of the severity level.

[0068] In subprocess 360, the controller 190 determines whether consensus has been reached. This determination in subprocess 360 may utilize any of a variety of potential schemes to establish consensus (i.e., more than one indication of unplanned islanding) before unplanned islanding is detected. Several such consensus-based schemes will now be described. However, it should be understood that the described schemes are non-limiting and any different consensus-based schemes may be utilized in subprocess 360. The advantages of the disclosed embodiments are achieved by requiring that multiple indications of unplanned islanding be identified before any control (e.g., tripping the PCC circuit breaker 142) that disrupts normal operation of the DER circuit 130 is performed to thereby suppress or mitigate the effects of false alarms or cyber attacks on the DER circuit 130. Therefore, in each of these schemes, when indications are received from less than the consensus number of UI detection sources 170 and / or when less than the consensus number of indications are received from the UI detection sources 170, unplanned islanding is not detected. Conversely, unplanned islanding is detected when an indication is received from a consensus number of UI detection sources 170 and / or an indication of a consensus number is received from UI detection sources 170. The consensus number (which may be determined based on a predefined count, percentage, etc.) may be set based on the specific design goals of the implementation (e.g., a desired confidence level). However, it should be understood that the consensus number should be set so that more than one UI detection source 170 and / or more than one indication is required.

[0069] In the first scenario, consensus can be reached (i.e., "yes" in subprocess 360) when indications of unplanned islanding are received from a threshold number or a threshold percentage of different UI detection sources 170. In the illustrated example, there are five UI detection sources 170A, 170B, 170C, 170D, and 170E. In this case, a counter can be incremented each time a new indication is identified from a previously unseen UI detection source 170. If the threshold number is three (or the threshold percentage is 60%), consensus will be reached when the counter reaches three. This is an example of a single-layer consensus-based scenario.

[0070] In the second scheme, consensus can be reached (i.e., "yes" in subprocess 360) when a threshold number or threshold percentage of indications of unplanned islanding is received. This scheme may be applicable when a single UI detection source 170 transmits measurements of one or more parameters, which can each individually indicate unplanned islanding. For example, the measured values ​​of parameters that meet the corresponding predefined measurement thresholds can be identified as indications of unplanned islanding. In the illustrated example, there are five UI detection sources 170A, 170B, 170C, 170D, and 170E. For a total of twenty possible indications of unplanned islanding, it is assumed that each UI detection source 170 transmits measurements of four parameters, which can each individually indicate unplanned islanding (e.g., if the corresponding threshold is met). In this case, each time a measurement from any UI detection source 170 meets the corresponding measurement threshold, a counter can be incremented. If the threshold number is fifteen (or the threshold percentage is 75%), a consensus will be reached when the counter reaches fifteen. This is another example of a single-layer consensus based scheme.

[0071] In a third scenario, when an indication of unplanned islanding is identified from a threshold number or a threshold percentage of transmissions from different UI detection sources 170, a consensus may be reached (i.e., "yes" in subprocess 360), wherein no indication of unplanned islanding is identified in transmissions from UI detection sources 170 unless a threshold number or a threshold percentage of measurements indicate unplanned islanding. This scenario may be applicable when a single UI detection source 170 transmits measurements of multiple parameters, each of which may individually indicate unplanned islanding. For example, parameter measured values ​​that meet corresponding predefined measurement thresholds may be identified as an indication of unplanned 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 measurements of four parameters, each of which may individually indicate unplanned islanding (e.g., if the corresponding thresholds are met). In this case, a counter may be incremented each time a threshold number of measurements from previously unseen UI detection sources 170 meet their respective measurement thresholds. If the threshold number of different UI detection sources 170 is three (or a threshold percentage of 60%) and the threshold number of measurements is three (or a threshold percentage of 75%), consensus will be reached when the counter reaches three, indicating that each of the three UI detection sources has reported at least three measurements that meet their respective measurement thresholds. This is an example of a two-tier consensus-based approach.

[0072] It is noteworthy that the UI detection source 170 that monitors the measured values ​​of multiple parameters can be configured to locally determine whether a threshold number or a threshold percentage of the measured values ​​meet their corresponding thresholds. In this case, each UI detection source 170 may transmit an indication of unplanned islanding only when the UI detection source 170 locally determines that a threshold number or a threshold percentage of the measured values ​​meet their corresponding thresholds. In this case, when a threshold number or a threshold percentage of UI detection sources 170 transmit an indication of unplanned islanding, the controller 190 may determine that a consensus has been reached. Although technically this is an example of a two-layer consensus-based scheme, from the perspective of the controller 190, it is a single-layer consensus-based scheme that can be implemented by the controller 190 in the same manner as the first described scheme.

[0073] In a fourth scenario, a consensus can be reached (i.e., "yes" in subprocess 360) when a threshold number or threshold percentage of different UI detection sources 170 indicate unplanned islands and a threshold number or threshold percentage of measurements across all UI detection sources 170 indicate unplanned islands. This scenario may be applicable when a single UI detection source 170 transmits measurements of multiple parameters, which can each individually indicate unplanned islanding. For example, parameter measurements that meet corresponding predefined measurement thresholds can be identified as an indication of unplanned 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 measurements of four parameters, which can each individually indicate unplanned islanding (e.g., if the corresponding thresholds are met). In this case, there may be a first counter that tracks the number of different UI detection sources 170 that have transmitted measurements indicating unplanned islanding, and a second counter that tracks the total number of measurements indicating unplanned islanding transmitted by any UI detection source 170. If the threshold number of different UI detection sources 170 is three (or the threshold percentage is 60%) and the threshold number of measurements is fifteen (or the threshold percentage is 75%), then consensus will be reached when the first counter reaches three and the second counter reaches fifteen. This is another example of a two-tier consensus based approach.

[0074] In the fifth scheme, when an indication of unplanned islanding is identified in transmissions from a threshold number or threshold percentage of different UI detection sources 170 (wherein no indication of unplanned islanding is identified in transmissions from a UI detection source 170 unless a threshold number or threshold percentage of measurements indicate unplanned islanding) and a threshold number or threshold percentage of measurements across all UI detection sources 170 indicate unplanned islanding, a consensus can be reached (i.e., "yes" in subprocess 360). This scheme may be applicable when a single UI detection source 170 transmits measurements of multiple parameters, which may each individually indicate unplanned islanding. For example, parameter measured values ​​that meet corresponding predefined measurement thresholds may be identified as an indication of unplanned 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 measurements of four parameters that may each individually indicate unintended islanding (e.g., if corresponding thresholds are met). In this case, a first counter may be incremented each time a threshold number of measurements from previously unseen UI detection sources 170 meet their corresponding measurement thresholds, and a second counter may be incremented each time a measurement from any UI detection source 170 meets its corresponding threshold. If the threshold number of different UI detection sources 170 is three (or a threshold percentage of 60%), the threshold number of measurements from UI detection sources 170 is three (or a threshold percentage of 75%), and the threshold number of measurements across all UI detection sources 170 is sixteen (or a threshold percentage of 80%), consensus will be reached when the first counter reaches three (indicating that each of the three UI detection sources has reported at least three measurements that meet their corresponding measurement thresholds) and the second counter reaches sixteen. This is an example of a three-tier consensus-based scheme.

[0075] In any embodiment in which the UI detection source 170 may utilize different UI detection methods, a hybrid solution may be used. For example, some UI detection sources 170 may transmit locally determined indications of unplanned islanding or measured values ​​of a single parameter, while other UI detection sources 170 may transmit measured values ​​of multiple parameters. In this case, the controller 190 may increment the counter each time it identifies an indication of unplanned islanding in the transmission, but the controller 190 may identify each indication in a different manner depending on the UI detection source 170 from which the transmission is received. For example, if an indication of locally determined unplanned islanding is received, the controller 190 may increment the counter. If a transmission consisting of a measured value of a single parameter is received, the controller 190 may increment the counter only if the measured value meets the corresponding measurement threshold. If a transmission including measured values ​​of multiple parameters is received, the controller 190 may increment the counter only if those measured values ​​of a threshold number or a threshold percentage meet the corresponding measurement threshold. Regardless of how the indications from the different UI detection sources 170 are identified, the controller 190 may determine that consensus has been reached when the counter reaches the consensus threshold (ie, “yes” in subprocess 360 ).

[0076] In a sixth scenario, consensus may be reached (i.e., "yes" in subprocess 360) when the indicated overall severity level reaches the consensus threshold. This scenario may apply when the UI detection source 170 transmits the difference between each measurement value and its corresponding measurement threshold value (indicative of the severity level of the measured parameter). Alternatively, the UI detection source 170 may transmit the measurement values, and the controller 190 may calculate the difference between these measurement values ​​and their corresponding measurement threshold values. In either case, these differences may be combined in some way, and the result may be compared to the consensus threshold value. It is worth noting that in this scenario, the counter is not a simple incrementing counter. Instead, subprocess 355 may include a more complex calculation that combines the aggregate difference or other representation of the aggregate severity level with the difference of the new indication of unplanned islanding identified in subprocess 350. As a result, the consensus is not based on whether the UI detection source 170 agrees that unplanned islanding has occurred. Instead, the consensus is based on whether the DER circuit 130 as a whole has reached an aggregate state indicating a severity level of unplanned islanding.

[0077] The sixth solution can be further improved if the UI detection sources 170 utilize different UI detection methods. For example, consider two UI detection sources 170 that utilize two different UI detection methods with two different non-detection zones. At the moment of unplanned islanding, the net power change may be within the non-detection zone of the first UI detection source in the UI detection sources 170, but outside the non-detection zone of the second UI detection source in the UI detection sources 170. In this case, the first UI detection source 170 will not provide an indication of unplanned islanding, while the second UI detection source 170 will provide an indication of unplanned islanding. If the consensus algorithm only knows that the second UI detection source 170 indicates an unplanned islanding and the first UI detection source 170 does not indicate an unplanned islanding, then no UI response will be triggered. However, if the consensus algorithm knows that the second UI detection source 170 indicates that the measured parameter is far beyond its corresponding measurement threshold and the first UI detection source 170 indicates that the measured parameter is very close to but not completely at its corresponding measurement threshold, the aggregate state of the severity level may be sufficient to trigger a UI response.

[0078] In any scheme utilizing measurements of one or more parameters, these parameters may include any parameters that may indicate unplanned islanding. Examples of such parameters include, but are not limited to, undervoltage / overvoltage, underfrequency / overfrequency, rate of change of frequency, voltage vector shift, rate of change of frequency to rate of change of power (df / dP), total harmonic distortion (THD), rate of change of symmetrical components, and / or the like. It should be understood that a single UI detection source 170 may measure any combination of one or more (potentially including all) of these parameters and other parameters not specifically described herein.

[0079] With respect to under / overvoltage or under / overfrequency, the voltage and / or frequency of unplanned islanding may rise or fall in the absence of a rigid high inertia grid 110. This may especially occur if there is an imbalance between the generation of the distributed energy resources 150 and the loads 160 within the island. Thus, if the voltage or frequency exceeds a first measurement threshold or falls below a second measurement threshold, unplanned islanding may be indicated.

[0080] Regarding the rate of change of frequency, in the absence of a high inertia grid 110, the frequency in an unplanned island may change rapidly due to an imbalance between the power generated by the distributed energy resources 150 and the loads 160 within the island. Therefore, if the rate of change of frequency (i.e., the derivative of the frequency) exceeds a measurement threshold, an unplanned island may be indicated. Positive and negative rates of change of frequency may be calculated as two separate parameters or as a single parameter.

[0081] With respect to voltage vector shift, a sudden loss of voltage reference from grid 110 may cause a step change in voltage phase within DER circuit 130. Thus, the voltage signal period may be tracked, and if the difference between the measured signal period and the reference exceeds a measurement threshold, unplanned islanding may be indicated.

[0082] With respect to the rate of change of frequency with power, under normal grid connection conditions, changes in power output by the distributed energy resources 150 will not result in significant changes in frequency within the DER circuit 130. However, without a connection to the high inertia grid 110, a step change in output power can result in a large change in frequency. Therefore, the value of the ratio of the rate of change of frequency to the rate of change of power (i.e., df / dP) may be tracked, and if the value exceeds a measurement threshold, unplanned islanding may be indicated.

[0083] With respect to total harmonic distortion, when DER circuit 130 loses connection to grid 110, high frequency components of the current output by distributed energy resources 150 may experience an impedance increase, which results in an increase in total harmonic distortion of the voltage. Thus, if the total harmonic distortion exceeds a measurement threshold, unplanned islanding may be indicated.

[0084] Unplanned islanding may cause a disturbance in the symmetry of the three-phase current waveform with respect to the rate of change of symmetrical components (e.g., positive and negative sequence). Therefore, if the rate of change of the amplitude of the positive or negative sequence components exceeds a measurement threshold, unplanned islanding may be indicated.

[0085] Regardless of the particular scheme and / or measurements used, when consensus has been reached (i.e., "yes" in subprocess 360), process 300 proceeds to subprocess 365. Otherwise, if consensus has not been reached (i.e., "no" in subprocess 360), process 300 continues to wait for either the timer to expire or consensus to be reached.

[0086] In subprocess 365, controller 190 may begin preparing for islanding. Preparing for islanding may include any steps necessary to transition DER circuit 130 to planned islanding (i.e., prior to opening PCC circuit breaker 142). Such steps may include configuring various components of DER circuit 130, including, but not limited to, managing loads 160 to prepare them for islanding, changing the control mode of DER circuit 130 or one or more distributed energy resources 150 within DER circuit 130 from grid following to grid forming, providing voltage and frequency references, performing load shedding as needed, and / or the like. In subprocess 370, controller 190 may initiate transition of PCC circuit breaker 142 from a closed state to an open state. For example, controller 190 may communicate with PCC circuit breaker 142 directly or indirectly (e.g., via a network) to transmit a control command or signal that causes PCC circuit breaker 142 to open. After the PCC circuit breaker 142 has transitioned to the open state (indicating planned islanding), the DER circuit 130 may operate in an islanded mode. The process 300 may end until the PCC circuit breaker 142 transitions back to the closed state, at which time the process 300 may restart. In other words, the process 300 may operate whenever the PCC circuit breaker 142 is in the closed state, and the process may cease to operate whenever the PCC circuit breaker 142 is in the open state.

[0087] Notably, once PCC circuit breaker 142 has opened, regional EPS (including transformer 120) is no longer energized by DER circuit 130 to comply with applicable grid codes. DER circuit 130 may continue to operate in islanded mode.

[0088] Figure 4 An example state diagram 400 for consensus-based UI detection according to an embodiment is illustrated. The state diagram 400 may be implemented by a controller 190 within a supervisory control layer of a DER circuit 130. Although the state diagram 400 is illustrated as having a certain arrangement of states, the state diagram 400 may be implemented with fewer, more, or different states and differently arranged states.

[0089] In state 410, the DER circuit 130 operates normally (e.g., corresponding to subprocess 305) while connected to the regional EPS. If an indication of unplanned islanding is received from the local UI detection source 170 during normal operation 410 (e.g., corresponding to "no" in subprocess 310), the controller 190 transitions to topology analysis 420 (e.g., corresponding to subprocesses 315 and 320) to locate the source of the indication. If an indication of unplanned islanding is received from the remote UI detection source 170 during normal operation 410 (e.g., corresponding to "yes" in subprocess 310), the controller 190 transitions to consensus algorithm 430 (e.g., corresponding to subprocesses 330-360). At this point, the controller 190 does not yet know whether a true island has formed or whether the UI detection logic has tripped for another reason, such as an inappropriate trip based on a false alarm or a cyber attack.

[0090] Based on the topology analysis 420, if the UI detection indicates internal islanding, the controller 190 transitions to a protection operation 440, which may involve reconfiguration of the DER circuit 130. Once the protection operation 440 is completed, the controller 190 transitions from the protection operation 440 to the normal operation 410. On the other hand, if the UI detection indicates external islanding, the controller 190 transitions from the topology analysis 420 to the consensus algorithm 430.

[0091] According to consensus algorithm 430, if consensus is not reached within the predefined time window (e.g., corresponding to "yes" in subprocess 345), controller 190 transitions back to normal operation 410. Otherwise, if consensus is reached within the predefined time window (e.g., corresponding to "yes" in subprocess 360), controller 190 transitions from consensus algorithm 430 to islanding preparation 450 (e.g., corresponding to subprocess 365). Once islanding preparation 450 is completed, controller 190 transitions from islanding preparation 450 to islanded operation 460 (e.g., corresponding to subprocess 370), in which DER circuit 130 is disconnected from regional EPS. Once islanded operation 460 has been completed (e.g., electrical connection with grid 110 is restored), controller 190 transitions from islanded operation 460 to normal operation 410.

[0092] The applicable grid code for DER circuit 130 may constrain the time period during which DER circuit 130 must detect and respond to unplanned islanding. For example, the IEEE 1547 standard requires DER circuit 130 to detect unplanned islanding and de-energize it within two seconds after they form. Therefore, controller 190 should be able to perform process 300 within this time constraint defined by the grid code.

[0093] Figure 5An example timing of a process 300 for consensus-based UI detection according to an embodiment is illustrated, where the time constraint specified by the applicable grid code is two seconds. As illustrated, after identifying the first indication of a planned islanding phenomenon (e.g., in subprocess 305), the controller 190 begins running a consensus algorithm (e.g., including subprocesses 330-360). Once consensus has been reached (e.g., "yes" in subprocess 360), the controller 190 begins the transition of the DER circuit to a planned island (e.g., subprocesses 365 and 370).

[0094] The consensus algorithm and transition should be able to complete within a specified time period (e.g., two seconds). Therefore, the length of the timer used in the consensus algorithm (e.g., initiated in subprocess 335) should be set to be sufficient to capture sufficient indications of unplanned islanding to meet the consensus threshold, but short enough to enable transition to planned islanding within the applicable time constraints, while taking into account delays in communication, processing, and / or the like. For example, the length of the timer can be calculated as the time constraint minus the maximum time duration required for the UI detection source 170 to communicate an indication of unplanned islanding to the controller 190, minus the maximum time duration required to transition to planned islanding, potentially minus a buffer duration. For example, if the time constraint is two seconds, communication between the UI detection source 170 and the controller 190 requires a maximum of 50 milliseconds, and the transition to planned islanding requires a maximum of 1 second, the length of the timer can be set to 950 milliseconds.

[0095] The disclosed consensus-based or coordinated UI detection has numerous advantages over conventional UI detection based on individual UI detection sources (e.g., monitored only at a common coupling point). For example, a redundant and consensus-based approach using multiple UI detection sources 170 distributed across multiple locations within and / or outside the DER circuit 130 to trigger a UI response when the number of positive indications has reached a threshold value improves the sensitivity (i.e., the ability to correctly detect unplanned islanding regardless of the size of the disturbance), selectivity (i.e., the ability to ignore disturbances that are not caused by unplanned islanding), and resilience to cyber attacks (i.e., the ability to ignore malicious false positives) of the DER circuit 130. Additionally, in embodiments, different types of UI detection sources 170 may be utilized in order to introduce diversity or robustness into the consensus-based UI detection process.

[0096] The sensitivity of any single UI detection method is limited by the location of the UI detection method and the UI detection source 170 within the DER circuit 130. The process 300 can improve the overall sensitivity of UI detection for the DER circuit 130 because the utilization of multiple UI detection sources 170 and / or multiple parameters ensures that the most sensitive UI detection method for each given situation will be operated during UI detection. For example, the utilization of multiple UI detection sources 170 and / or multiple parameters (which may have overlapping detection zones) effectively reduces or eliminates non-detection zones that exist in conventional passive UI detection methods. Therefore, the process 300 is able to detect unintended islands that cannot be detected by conventional passive UI detection methods.

[0097] Events other than unplanned islanding can cause disturbances that may produce an indication of unplanned islanding under certain UI detection methods. For example, a voltage-based method may trip due to a large change in load, while a frequency-based method will ignore the same disturbance. Process 300 can increase the selectivity of UI detection because the utilization of multiple UI detection sources 170 and / or multiple parameters prevents such improper tripping. In particular, because consensus is required, a single false alarm cannot trigger a UI response. The type and arrangement of UI detection sources 170 can be selected to prevent all such false alarms from triggering a UI response. Therefore, process 300 is able to prevent improper tripping, as required by applicable grid codes.

[0098] The process 300 may also increase the resilience of UI detection to cyber attacks. For example, the utilization of multiple UI detection sources 170 increases redundancy to prevent a compromised UI detection source 170 from triggering a UI response. In particular, the requirement for consensus prevents a single or small group of 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, then in order to trigger a UI response (e.g., take the DER circuit 130 offline), the process 300 prevents cyber attacks by requiring confirmation of unplanned islanding by one or more different UI detection sources 170 before triggering a UI response. In order for a cyber attack to be successful, a malicious actor would need to compromise a threshold number of UI detection sources 170. Notably, the cyber resilience of the DER circuit 130 may be proportionally increased 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.

[0099] Notably, the process 300 is also computationally inexpensive (i.e., does not require a large amount of computing resources). Thus, the process 300 can be incorporated into an existing controller 190 of a DER circuit 130. Additionally, the process 300 is capable of executing within the time constraints imposed by applicable grid codes. During experiments involving several different scenarios, the process 300 was able to detect true unplanned islanding within 0.3-0.4 seconds, which is well within the two-second time constraint imposed by IEEE 1547-2018, while successfully ignoring false alarms.

[0100] As discussed elsewhere herein, the UI detection source 170 may measure one or more parameters. In an embodiment, one or more (including potentially all) UI detection sources 170 measure multiple parameters, such as a positive rate of change of frequency, a negative rate of change of frequency, a rate of change of a positive sequence component, and / or a rate of change of a negative sequence component. Each measured parameter represents a distinct UI detection function by which unplanned islands may be detected. In particular, each measured parameter may be compared to a corresponding measurement threshold, and if the measured parameter satisfies the corresponding measurement threshold (e.g., exceeds the threshold in the case of the four example parameters mentioned above), it may be used to indicate the potential for unplanned islands.

[0101] The respective measurement threshold for each UI detection function (i.e., measured parameter) may be tuned to achieve an appropriate balance between sensitivity and selectivity. Notably, different measurement thresholds may be used for different UI detection sources 170, for example, based on their location within the DER circuit 130. Additionally, in scenarios where a threshold number or threshold percentage of measurements are required to satisfy a respective measurement threshold, the threshold may also be set to achieve an appropriate balance between sensitivity and selectivity. Additionally, a consensus threshold number or threshold percentage of UI detection sources 170 from which an indication of an unplanned islanding phenomenon must be received before an unplanned islanding is detected may also be set to achieve an appropriate balance between sensitivity, selectivity, and network resilience. In other words, there are multiple levels that may be tuned based on experiments (e.g., simulations) and design goals (e.g., applicable time constraints) to achieve an appropriate balance between sensitivity, selectivity, and / or network resilience.

[0102] The following table illustrates one specific example of measurement thresholds for different example parameters measured by each of the UI detection sources 170A- 170E in the DER circuit 130 (i.e., positive and negative rates of change of frequency, rates of change of positive sequence current, and rates of change of negative sequence current):

[0103]

[0104] In an embodiment, different consensus algorithms may be utilized depending on one or more characteristics of DER circuit 130 (e.g., load conditions, net steady-state power, etc.). For example, a first consensus algorithm may be utilized in process 300 when the net steady-state power crossing point of common coupling 140 is outside the overall non-detection zone, and a second consensus algorithm may be utilized in process 300 when the net steady-state power crossing point of common coupling 140 is within the overall non-detection zone. The overall non-detection zone may be identified in advance by systematically studying various non-detection zones in the passive UI detection method utilized by UI detection source 170. The first consensus algorithm and the second consensus algorithm may differ in various aspects, including, but not limited to, whether to prevent tripping in subprocess 330, various measurement thresholds (e.g., different measurement thresholds based on load conditions), consensus thresholds, consensus-based schemes, and / or the like. For example, in a first consensus algorithm (i.e., when power is utilized outside of the overall non-detection zone), the internal active UI detection methods of the distributed energy resources 150 may be blocked in subprocess 330, while in a second consensus algorithm (i.e., when power is utilized inside the overall non-detection zone), subprocess 330 may be omitted so that blocking does not occur. Thus, in situations where passive UI detection methods may fail to detect unplanned islanding, the distributed energy resources 150 may continue to employ their internal active UI detection methods.

[0105] The above description of the disclosed embodiments is provided to enable any person skilled 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 present invention. Therefore, it will be understood that the description and drawings presented herein represent currently preferred embodiments of the present invention, and therefore represent the subject matter broadly contemplated by the present invention. It should be further understood that the scope of the present invention fully encompasses other embodiments that may become apparent to those skilled in the art, and the scope of the present invention is accordingly not limited.

[0106] 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" described herein include any combination of A, B, and / or C, and may include multiple A, multiple B, or multiple C. 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 only A, only B, only C, A and B, A and C, B and C, or A, B, and C, and any such combination may include one or more members of its components A, B, and / or C. For example, the combination of A and B may include one A and multiple Bs, multiple A and one B, or multiple A and multiple Bs.

Claims

1. A method of detecting unplanned islanding (UI) of at least one distributed energy resource (DER) circuit, the method comprising using at least one hardware processor to: monitoring transmissions from a plurality of UI detection sources to identify indications of unintended islanding from the plurality of UI detection sources; and Detection of unplanned islanding of DER circuits is performed by: When indications of unintentional islanding are identified from less than a consensus number of the plurality of UI detection sources during the time window, it is determined that unintentional islanding is not detected, wherein The consensus number is greater than one, and Unintentional islanding is determined to be detected when an indication of unintentional islanding is identified from the consensus number of the plurality of UI detection sources during the time window.

2. The method according to claim 1, wherein: The transmissions from one or more of the plurality of UI detection sources each include a plurality of measurements, and wherein the method includes identifying an indication of unintended islanding in the transmissions from each of the one or more UI detection sources by: For each of the plurality of measurements, determining whether the measurement satisfies a corresponding measurement threshold; determining an indication that unintentional islanding has been identified in the transmission when a threshold number of the plurality of measurements satisfies the corresponding measurement threshold, wherein the threshold number is greater than one; and An indication that unintended islanding was not identified in the transmission is determined when the threshold number of the plurality of measurements does not satisfy the corresponding measurement threshold.

3. The method according to claim 2, wherein: The plurality of measurements include positive rates of change of frequency and negative rates of change of frequency.

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

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

6. The method according to claim 1, comprising: When an indication of unintended islanding is identified in a transmission from a first UI detection source of the plurality of UI detection sources, using the at least one hardware processor to: determining whether the first UI detection source is local to the DER circuit or remote from the DER circuit; when it is determined that the first UI detection source is local to the DER circuit, determining whether to perform detection of unplanned islanding of the DER circuit based on the location of the first UI detection source within the DER circuit; as well as When it is determined that the first UI detection source is far away from the DER circuit, detection of an unplanned islanding phenomenon of the DER circuit is performed.

7. The method according to claim 6, wherein: Determining whether to perform unplanned islanding detection of the DER circuit based on the location of the first UI detection source within the DER circuit includes: determining whether the first UI detection source is downstream of a segmenting device within the DER circuit; When it is determined that the first UI detection source is not downstream of the segmenting device, performing detection of unintended 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 segmenting device is in a disconnected state, When it is determined that the segmenting device is not in the disconnected state, performing detection of unplanned islanding of the DER circuit, and When it is determined that the sectionalizing device is in the disconnected state, detection of unintended islanding of the DER circuit is not performed.

8. The method according to claim 1, further comprising: When an indication of unintended islanding is identified in a transmission from a first UI detection source of the plurality of UI detection sources, using the at least one hardware processor to: Starting a timer representing the time window and performing detection of unplanned islanding of the DER circuit from the start of the timer; and Transition of the DER circuit to planned islanding is prevented unless and until unplanned islanding of the DER circuit is detected before expiration of the timer.

9. The method according to claim 1, further comprising: In response to detecting unplanned islanding of the DER circuit, transitioning the DER circuit to planned islanding is initiated using the at least one hardware processor.

10. The method according to claim 9, wherein: Initiating transition of the DER circuit to a planned island includes preparing the DER circuit for the planned island.

11. The method according to claim 10, further comprising: After preparing the DER circuit for the planned islanding, a point of common coupling with the DER circuit is disconnected using the at least one hardware processor.

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

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

14. A system comprising: Control system, including: At least one hardware processor, and software, configured, when executed by the at least one hardware processor: monitoring transmissions from a plurality of UI detection sources to identify indications of unintended islanding from the plurality of UI detection sources, and Detection of unplanned islanding of the DER circuit is performed by: determining that unintentional islanding is not detected when indications of unintentional islanding are identified from less than a consensus number of the plurality of UI detection sources during the time window, wherein the consensus number is greater than one, and Unintentional islanding is determined to be detected when an indication of unintentional islanding is identified from the consensus number of the plurality of UI detection sources during the time window. The system of 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 distributed at different locations relative to the DER circuit.

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

18. The system of claim 15, wherein: At least one UI detection source of the plurality of UI detection sources generates an indication of unintentional islanding using a different UI detection method than another UI detection source of the plurality of UI detection sources.

19. The system of claim 14, wherein: The transmissions from one or more of the plurality of UI detection sources each include a plurality of measurements, and wherein the software is further configured to identify an indication of unintended islanding in the transmissions from each of the one or more UI detection sources by: For each of the plurality of measurements, determining whether the measurement satisfies a corresponding measurement threshold; determining an indication that unintentional islanding has been identified in the transmission when a threshold number of the plurality of measurements satisfies the corresponding measurement threshold, wherein the threshold number is greater than one; and An indication that unintended islanding was not identified in the transmission is determined when the threshold number of the plurality of measurements does not satisfy the corresponding measurement threshold.

20. A non-transitory computer readable medium having stored thereon instructions, wherein: The instructions, when executed by a processor, cause the processor to: monitoring transmissions from a plurality of UI detection sources to identify indications of unintended islanding from the plurality of UI detection sources; and Detection of unplanned islanding of the DER circuit is performed by: determining that unintentional islanding is not detected when indications of unintentional islanding are identified from less than a consensus number of the plurality of UI detection sources during the time window, wherein the consensus number is greater than one, and Unintentional islanding is determined to be detected when an indication of unintentional islanding is identified from the consensus number of the plurality of UI detection sources during the time window.

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