Microgrid error handling framework and method

Abstract

The invention relates to a micro-grid error processing framework and method. A method of handling one or more errors in a microgrid includes measuring an attribute of a device within the microgrid for a measurement period and comparing the measured attribute of the device to a predetermined threshold attribute value. The presence of an error associated with the device is detected based on a comparison of the measured attribute to a predetermined threshold attribute value. The created error signal includes a sequence of digits having at least three digits identifying the sequence of digits of measured attributes and devices within the microgrid.

Description

Technical Field

[0001] The present disclosure relates to a framework, method and system for error handling in a microgrid. Background Art

[0002] The proliferation of renewable energy sources, battery and power storage devices, and grid-connected electrical devices has led to a corresponding proliferation of microgrids, which consist of generators, storage, and load banks connected to utility lines. However, operating a microgrid in accordance with electrical standards and / or regulations can be difficult because the complexity of microgrids and the number and type of devices they contain vary widely. To ensure proper operation of a microgrid, the microgrid must be monitored and controlled by an appropriate control scheme. The control scheme may include procedures for detecting and handling errors based on measurement data received from the entire microgrid or from individual devices within the microgrid. Detecting and handling such errors is important because if the microgrid exhibits anomalies in operation, intervention may be required to ensure safety and prevent damage to the microgrid or its components.

[0003] However, conventional error handling frameworks have difficulty managing errors in microgrids that include many devices or many types of devices. Each type of device in the microgrid may provide a different set of measurements, making error detection different for each device type in the microgrid. In addition, it is difficult to separate or distinguish between transient / non-critical errors and permanent and / or critical errors. Furthermore, a limitation of known error handling frameworks is that errors may be handled sequentially or non-sequentially over time.

[0004] Traditional microgrids can be monitored based on measurements taken from within the microgrid to assess the health of the microgrid and determine when anomalies exist in the microgrid. Traditional solutions also include targeted error handling methods and / or structures that are designed to handle a single type of error but do not provide functionality or flexibility beyond the specific errors for which they were designed. In addition, traditional error handling solutions may not be able to handle multiple errors, especially simultaneously, and / or manage the measurements of the errors independently.

[0005] Therefore, improved error handling methods and frameworks are needed to manage faulty components in microgrids. Summary of the invention

[0006] A method for processing one or more errors in a microgrid includes measuring a property of a device within the microgrid for a measurement period and comparing the measured device property to a predetermined threshold property value. Based on the comparison of the measured property to the predetermined threshold property value, the presence of an error associated with the device is detected. The created error signal includes a digital sequence having at least three digits, the digital sequence identifying the measured property and the device within the microgrid. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The subject matter of the present disclosure will be described in more detail below based on exemplary drawings. All features described and / or illustrated herein may be used alone or in combination in various combinations. The features and advantages of various implementations will become apparent by reading the following detailed description with reference to the accompanying drawings, which illustrate the following:

[0008] Figure 1 illustrates an error handling framework according to an embodiment of the present disclosure;

[0009] Figure 2 illustrates computer implemented code for performing error determination comparisons according to embodiments of the present disclosure;

[0010] Figure 3 A lookup table template and a lookup table according to an embodiment of the present disclosure are illustrated;

[0011] Figure 4 A flowchart illustrating an error handling method according to an embodiment of the present disclosure; and

[0012] Figure 5 The results of simulation operations using the error handling framework according to an embodiment of the present disclosure are illustrated. DETAILED DESCRIPTION

[0013] In one aspect of the present disclosure, a modular and flexible framework for handling different types of errors in a microgrid is described. Using this framework, different microgrid attributes or conditions can be defined for each component of the microgrid. Therefore, if one of the attributes or conditions is violated, a specific course of action can be taken to handle such errors. In addition, using this architecture, transient errors can be distinguished from permanent errors. After generating the required error mitigation signals, various aspects of the present disclosure allow the system dynamics to settle down, and if the detected error of the device is determined to be permanent, the device is also marked for further inspection. Simultaneous errors can also be detected. In addition, various aspects of the present disclosure generate an error signal that carries all the information required by the microgrid controller. For example, if the state of charge (SOC) of the battery is not within an acceptable range, an error signal may be provided indicating that the faulty item is a battery energy storage system (BESS) and that the problem is a battery SOC measurement error.

[0014] Embodiments of the present disclosure provide a flexible framework for incorporating any thresholds based on user preferences in error handling. The framework also has the flexibility to incorporate fixed thresholds or probabilistic thresholds into error handling. Compared to traditional error handling systems and methods, embodiments of the present disclosure also provide methods for separating temporary errors from permanent errors, taking into account the dynamics of the system, and providing different remedial actions that can be taken for severe error conditions and non-severe error conditions. Automatic assessment of error persistence is also incorporated into error handling, and provisions are also provided for marking devices that require further inspection. Embodiments of the present disclosure are also capable of identifying multiple errors simultaneously and allow error types and fault items to be reported to the microgrid controller for remedial actions. Embodiments of the present invention provide algorithms that are modular and can be implemented for any microgrid structure.

[0015] In addition, embodiments of the present disclosure provide improved computational efficiency in error processing because a single signal with merged error data for multiple simultaneously detected errors can be processed rather than processing multiple signals from multiple input channels. Computational speed associated with error processing is also increased because embodiments of the present disclosure are able to determine remedies for more urgent and permanent errors in a single signal rather than requiring a process to fully process non-urgent signals without error indications before having to continue processing subsequent error signals.

[0016] Figure 1 The error handling framework according to an embodiment of the present disclosure is illustrated. The framework 100 includes an error detection and identification layer 102, an error aggregation and processing layer 104, and a microgrid controller layer 106. The error detection and identification layer 102 includes measurements taken from within the microgrid, each measurement corresponding to a measured value of an attribute of a microgrid device. The error aggregation and processing layer 104 includes error aggregation performed at the microgrid controller level, responsible for integrating all error signals and generating remedial actions. The microgrid controller layer 106 includes one or more physical microgrid controllers with embedded selector functions. The microgrid controller provides an appropriate operating mode based on its input, which will be described in more detail later. The microgrid controller is configured to determine the operating mode based on the output received from the error aggregation and processing layer 104 as an input to the state machine. The state machine can also receive other system operating conditions as input. The state machine is then used to determine the operating mode based on the input, and the microgrid controller implements control of the microgrid components according to the determined operating mode.

[0017] The error detection and identification layer 102 includes several definable attributes, each of which can be considered as an independent module that requires certain measurements. Each attribute can interact with other modules or layers through the code conventions described in the present disclosure, and the error aggregation and processing layer 104 can handle each module with minimal dependency on other modules. For the above reasons, the error detection and identification layer 102 provides modularity that can accommodate various systems with different attribute monitoring requirements while always supporting the processing of multiple errors at the same time.

[0018] For example, standard measurements for conventional generators and renewable energy sources may include current, voltage, active power, and reactive power. Batteries may provide respective active and reactive power status, as well as respective SOC. Standard measurements for loads may be active and reactive demand consumption, as well as load power factor. To detect disconnection errors, all operating flags from one or more disconnects may be used, which may include one or more commonly coupled disconnect points. One or more line breakers may be designed for overcurrent, overvoltage, and / or overfrequency protection.

[0019] The operational flags may be stored as real-time signals or in an array to provide a historical behavior of the signal. The measured value, whether it is embodied as a real-time measurement or historical data, may then be compared to a predetermined threshold. A predefined threshold may be fixed for real-time data. For example, the maximum output of a photovoltaic (PV) unit may be determined from its data table and used as a predetermined threshold. This threshold is compared to the provided measured value. If the measured value exceeds the predetermined threshold, an error signal (Ec) is generated.

[0020] For historical data, the historical average of a particular measured attribute can be determined and compared to the current measured value of that attribute. Specifically, the measured value can be compared to the historical average plus three standard deviations of the historical values. Thus, the error signal accuracy can be 99% or better. Figure 2 2 is shown in the form of code or script 200 that can be implemented in software. However, if the measured values ​​are compared to the historical average plus two standard deviations, an error signal accuracy of 95% or higher can be achieved. The above comparison is useful for detecting errors in loads and renewable energy sources because these data change over time. If sufficient historical information is stored in the error handling framework, the average and standard deviation values ​​for different time periods can be easily calculated. The measured values ​​can then be compared to dynamic thresholds to determine whether they are correlated with past data, and if a corresponding error is determined to have occurred based on this comparison, an error signal can be generated.

[0021] In order to distinguish between serious errors and non-serious errors, a code convention for reporting errors is required. Therefore, a three-digit error code is provided, wherein the first and second digits indicate the defective item and its identification number, and wherein the third digit indicates the cause of the error. A lookup table may be provided, whereby each digit may be selected from the lookup table. Lookup tables may be defined in the user interface for items and attributes defined in the error detection and identification layer 102. For ease of illustration, an error code may be "521". If the value 5 is associated with a BESS of a microgrid in the lookup table, then the error code 521 will point to the BESS identified by the value 2. The third digit, 1, will then identify the attribute of the identified device of the microgrid. For example, Figure 2 The error code Ec of "211" is illustrated, where the third digit corresponds to the attribute identified by the value 1. Figure 3 The above error code format and the meaning of the numbers within the error code are explained in more detail. The remaining steps of the error handling process can then be performed according to the remaining layers of the error handling framework and as described below.

[0022] Figure 3 The diagram shows a lookup table template 300 and a lookup table 310. The lookup table template 300 contains entries for each of the three digits that make up the error code. Specifically, the lookup table template 300 includes a project type identification value for the first digit 302, a project number identification value for the second digit 304, and an attribute identification value for the third digit 306. The lookup table 310 represents an illustrative example of the form that the lookup table implemented according to the embodiment of the present disclosure can have. For the first digit 312, various project types in the microgrid and their corresponding values ​​are listed. In the illustrated embodiment, the microgrid project may include a circuit breaker, a load, a renewable energy source (RES), a conventional generator (CG), a battery energy storage system (BESS), and a reserved port for an unidentified project or project that can be selectively connected to the microgrid. The second digit 314 includes various values ​​for identifying a specific device in a device type or category from the first digit 312. The third digit 316 includes various attributes, each of which is associated with a value that can be used as the third digit.

[0023] The error aggregation and handling layer 104 creates two types of signals: aggregate error signals (ES) and permanent error signals (PEs). Es are generated whenever the threshold of the first layer (e.g., the error detection and identification layer 102) is violated. For example, if the lookup table indicates that an attribute value of 1 indicates a threshold violation, an Es will be generated in which at least one Ec signal is 1. PEs, on the other hand, need to be evaluated in more detail. Three parameters are introduced for this purpose. The first parameter is called the error cycle count (ECC). Using this parameter, the persistence of the error can be monitored and it can be determined whether the error is temporary or permanent. For example, when the ECC is set to 3, the error handling module ignores errors that last less than 3 cycles. If Es exceeds the specified conditions of the first layer for more than three cycles, PEs will become 1 (indicating the presence of a permanent error).

[0024] Depending on the type of erroneous measurement, a time frame may be required to implement remedial actions. For example, if the battery active power is greater than its maximum value for a period of time that exceeds the time specified by the ECC, it may be necessary to temporarily set the battery's active power P and reactive power Q to zero. This is achieved by setting the reference values ​​of P and Q to zero. However, after experiencing some transient state, it may take some time for the battery to stabilize to the new reference value. To achieve this goal, the PEs must be maintained for a specified period of time. This period of time is called the Error Signal Hold (ESH) and should be different for each component depending on the dynamic behavior of the component. The ESH of a specific component is directly dependent on the settling time of the component. The ESH of a component can be determined by applying a step change to the input of the component and then calculating the time it takes for the component to output within the stability band from the application of the step change. In order to effectively handle the error, the ESH value of the component should be greater than the settling time of the component. After the ESH is completed, the PEs are reset to zero and the error detection process is repeated.

[0025] If multiple erroneous measurements are observed within a short period of time, this could be a sign of a serious problem that requires human intervention. Therefore, another parameter is defined, called the Maximum Permanent Error Count (MPEC). To incorporate MPEC into the error handling framework, the time frame in which it is performed must be determined. This time frame is called the Maximum Error Measurement Interval (MEMI) and is completely adjustable by the microgrid operator. The error handling framework then counts the number of PEs, compares them to the MPEC during the MEMI, and if the number of PEs exceeds the MPEC, flags the device for further inspection. At this stage, service personnel must inspect the item and perform necessary maintenance before it can be brought back online.

[0026] Figure 4A flowchart 400 for an error handling module is illustrated and provides a visual illustration of the error handling process described above. First, an error is detected 402 based on whether the Ec or PEs signal is set to a corresponding value indicating that an error has been detected. In the illustrated embodiment, Ec is set to 1 (Ec=1) or PEs is set to 1 (PEs=1). This triggers a query 404 to determine whether the ECC is less than a predetermined limit. If the ECC is less than the predetermined limit, step 406 is performed, the permanent error signal is set to zero, the ECC is increased by the measurement sampling time, and the next time step is performed, thereby repeating the process shown in the flowchart 400 from the beginning. If the ECC is not less than the predetermined limit, a query 408 is performed to determine whether the ESH is less than the predetermined limit. If not, step 410 is performed, wherein the MPEC value is increased, Ec is set to zero, PEs is set to zero, both the ECC and ESH are reset, and the next time step is performed, thereby repeating the process shown in the flowchart 400 from the beginning. If the ESH is less than the predetermined limit, the permanent error signal is set to 1 to indicate that a permanent error exists in step 412.

[0027] Next, a query 414 is made to determine whether the MPEC is less than a predetermined limit. If the MPEC is not less than a predetermined limit, the device identified by the Ec signal is marked for further inspection in step 416. If the MPEC is less than the predetermined limit, step 418 is executed. In step 418, ECC and ESH are each increased by one measurement sample time. Remedial action is taken to more urgently address the error found. The remedial action taken may include setting the reference value to zero, tripping a circuit breaker or other tripping device, and / or sounding an audible and / or visual alarm. The process then continues to the next time step and repeats if the Ec signal still indicates that an error has been detected.

[0028] In case of a critical error, the equipment must be disabled. However, if the error is not critical, an alarm or indicator can be set to alert the microgrid operator. Depending on the nature of the error, appropriate actions can be taken. The microgrid controller should be able to operate in two modes. In the first mode, critical error conditions can be automatically corrected by disabling the equipment associated with the error. The dispatchability of the equipment is directly related to this operation. If the item can be dispatched, the reference value can be set to zero. In the case of non-dispatchable equipment, this can be performed by opening the equipment circuit breaker. The second mode of operation for non-critical situations is handled by using a notification-only strategy.

[0029] In an embodiment, the error handling framework of the present disclosure has the ability to handle multiple errors simultaneously. This is because the Es signal can be included as an array containing all real-time error information. For example, the Es signal can have the form of [0, 0, 314, 0, 521, ...], which will indicate errors in the devices identified by error codes 314 and 521, especially for the 4th attribute of the item identified by number 31 and the 1st attribute of the item identified by number 52. The microgrid controller can handle these two error instances in parallel and propose measures that can mitigate the impact of these two errors.

[0030] It is readily appreciated that the embodiments described in the present disclosure are exemplary and may be modified without departing from the spirit of the present disclosure. For example, although a specific convention for the Ec and PEs values ​​is described in the exemplary embodiment above according to flowchart 400, the specific value (0 or 1) of the signal is not important. One of ordinary skill in the art will readily recognize that whether to use a zero signal to indicate the presence or absence of an error (or the value of the state) is merely a matter of preference and does not depart from the spirit of the process shown in flowchart 400 or other embodiments described herein.

[0031] Figure 5 The results of the simulation operation using the error handling framework according to the embodiment of the present invention are shown. Specifically, Figure 5 A simulated conventional generator (CG) output graph 500 is illustrated, wherein the CG output in megawatts is plotted over time. A corresponding simulated permanent error graph 510 is also plotted, wherein signal values ​​for PEs are plotted over the same time period as the CG output graph 500. In the simulation shown, the CG output exceeded a threshold defined in the error handling framework. Therefore, after reaching the MPEC limit of 3, the CG device was marked for further inspection. In the illustrated embodiment, a high signal for PEs (PEs=1) is used to indicate a nominal value, while a low signal (PEs=0) is used to indicate a permanent error. As previously discussed, this difference in convention does not cause Figure 5 The embodiments of are not compatible with other embodiments described in this disclosure, but merely represent differences in signal conventions that can be implemented in any embodiment described herein.

[0032] like Figure 5As shown in the error diagram 510, when the CG output exceeds the maximum CG output threshold, PEs is set to zero (which indicates a permanent error in the illustrated embodiment). During the first time period of the error diagram 510, the PEs signal remains at zero during the hold time. During this hold time, since the CG is disabled, the CG output drops to zero. The presence of the erroneous measurement is obvious. The correct output value of the CG should be zero throughout the period that the CG is disabled, but during time period 1, a varying non-zero output is measured in the output diagram 500. After the wait time has passed, PEs is reset to 1 (PEs=1), enabling the CG function. When the CG output exceeds the maximum CG output value threshold again, the process for time period 1 described above is repeated for time periods 2 and 3. However, when the MPEC limit is reached, PEs is set to zero (PEs=0), exceeds the hold time, and the device is marked for further inspection.

[0033] The use of the terms "a" and "an" and "the" and "at least one" and similar indicators in the context of describing the present invention (especially in the context of the following claims) should be interpreted as including the singular and the plural, unless otherwise stated herein or clearly contradicted by the context. The use of the term "at least one" followed by a list of one or more items (e.g., "at least one of A and B") should be interpreted as referring to one item selected from the listed items (A or B) or any combination of two or more listed items (A and B), unless otherwise stated herein or clearly contradicted by the context. Unless otherwise stated, the terms "including", "having", "including" and "comprising" should be interpreted as open-ended terms (i.e., meaning "including but not limited to"). Unless otherwise stated herein, the numerical ranges listed herein are intended merely as a shorthand method of individually referring to each individual value falling within the range, and each individual value is incorporated into the specification as if it were individually listed herein. All methods described herein can be performed in any suitable order, unless otherwise stated herein or clearly contradicted by the context. The use of any and all examples or exemplary language (e.g., "such as") provided herein is intended only to better illustrate the invention and will not limit the scope of the invention unless otherwise required. No language in the specification should be construed as indicating any non-claimed element is essential to the practice of the invention.

[0034] Preferred embodiments of the present invention are described herein, including the best mode known to the present invention for implementing the present invention. After reading the above description, changes to these preferred embodiments may become apparent to those of ordinary skill in the art. The inventor expects that a skilled craftsman will appropriately adopt such changes, and the inventor intends to implement the present invention in a manner different from that specifically described herein. Therefore, the present invention includes all modifications and equivalents of the subject matter described in the appended claims of the present invention as permitted by applicable law. In addition, any combination of the above-mentioned elements in all possible variations thereof is included in the present invention, unless otherwise stated herein or clearly contradicted by the context.

Claims

1. A method for handling one or more errors in a microgrid, comprising: Measuring properties of devices in the microgrid for a measurement period; comparing the measured property of the device to a predetermined threshold property value; detecting the presence of an error associated with the device based on a comparison of the measured property to the predetermined threshold property value; and An error signal is created, the error signal comprising a digital sequence having at least three digits, the digital sequence identifying the property being measured and the device within the microgrid.

2. The method according to claim 1, comprising: determining an error cycle count, wherein the error cycle count is incremented for each measurement cycle in which the error is detected; comparing the error cycle count with a predetermined error cycle count value; and Based on the comparison of the error cycle count and the predetermined error cycle count value, it is determined whether the error is a persistent error.

3. The method according to claim 2, comprising: Determine the error signal holding time; comparing the error signal holding time with a predetermined error signal holding time threshold; as well as Based on the comparison between the error signal holding time and the predetermined error signal holding time threshold, it is determined whether the error is a permanent error or a transient error.

4. The method according to claim 3, comprising: If the error signal holding time exceeds the predetermined error signal holding time threshold, a maximum permanent error count is increased.

5. The method according to claim 4, comprising: comparing the maximum permanent error count to a maximum permanent error count threshold; as well as Based on a comparison of the maximum permanent error count to the maximum permanent error count threshold, a determination is made whether to flag the device for further inspection or to initiate remedial action.

6. The method of claim 5, wherein the remedial action comprises one or more of: tripping a circuit breaker, setting a reference value to zero, activating an audible alarm, and activating a visual alarm.

7. The method according to claim 1, wherein the digital sequence comprises at least three digits, wherein one of the at least three digits identifies a type of the device; wherein one of the at least three digits identifies an identification number of the device, and One of the at least three digits identifies the attribute.

8. The method of claim 7, further comprising providing a lookup table and identifying the device and the attribute based on a correlation of the device and the attribute to a value of the at least three digits in the lookup table.

9. The method of claim 1, wherein the error signal comprises an array having a plurality of digital sequences.

10. The method according to claim 1, comprising: forwarding the error signal to a state machine of a microgrid controller; determining an operating mode of the microgrid based on an output of the state machine; as well as The microgrid controller is utilized to operate the microgrid according to the operating mode.

11. The method of claim 1, wherein the predetermined threshold attribute value is a mean historical value of the attribute plus three times the standard deviation of the historical values ​​of the attribute.

12. The method of claim 11, wherein the predetermined threshold attribute value is dynamically calculated based on the historical value of the attribute over time and over a plurality of measurement periods.

13. The method of claim 1, wherein the steps of the method are iteratively repeated to provide a real-time error signal to a microgrid controller.

14. A non-transitory computer readable medium having processor-executable instructions stored thereon, wherein the processor-executable instructions, when executed by one or more processors, cause implementation of a method for handling one or more errors in a microgrid, the method comprising: Measuring properties of devices in the microgrid for a measurement period; comparing the measured property of the device to a predetermined threshold property value; detecting the presence of an error associated with the device based on a comparison of the measured property to the predetermined threshold property value; and An error signal is created, the error signal comprising a digital sequence having at least three digits, the digital sequence identifying the property being measured and the device within the microgrid.

15. A system comprising one or more processors, the processors being configured, alone or in combination, to provide for execution of a method comprising: measuring properties of devices within the microgrid for a measurement period; comparing the measured property of the device to a predetermined threshold property value; detecting the presence of an error associated with the device based on a comparison of the measured property to the predetermined threshold property value; and An error signal is created, the error signal comprising a digital sequence having at least three digits, the digital sequence identifying the property being measured and the device within the microgrid.

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