Methods and systems for determining an association between nodes and phases via a smart grid

Determining the number of loads associated with each phase in a three-phase electric power system. The loads can be associated with the consumption of electric power at a node, such as a metering device located at a facility. In one implementation, a central device that is connected to such nodes via a smart grid and a radio frequency mesh network can be leveraged to determine a phase in real time. For example, the central device can include a processor that executes one or more computer program modules which can cause a load tap changer having access to a distribution feeder in the smart grid to vary a voltage level supplied across each phase of the power system. Additionally, the central device can communicate with nodes in the mesh network to cause the nodes to perform voltage measurements and collect information related to such measurements.

TECHNICAL FIELD

This invention relates generally to electric power systems and more specifically to a software module that communicates with a load tap changer, or similar voltage regulating device, and selected nodes in a mesh network to collect and analyze information for correcting load imbalances in three-phase power systems.

BACKGROUND

Three-phase power systems are widely used to provide electric power to consumers. Efficient operation of such systems requires that loads are properly balanced across each phase. Unfortunately, load imbalances can be a common occurrence. Various systems such as power line carrier or power line communication systems offer an integrated solution to resolving such imbalances in part by leveraging the distribution feeder network to collect and analyze phase-related information, real-time, in a centralized location. Power line carrier systems, however, represent only one medium for correcting imbalances. Other systems that leverage existing network connectivity between centralized locations and devices capable of obtaining phase-related information that can be used to correct load imbalances are also desirable.

SUMMARY

Various aspects of the present invention relate to determining an association between nodes in a mesh network and electric power phases. In one aspect, a load tap changer can be instructed to apply an initial voltage level to the first electric power phase, the second electric power phase, and the third electric power phase. The initial voltage level is applied for an initial period. The load tap changer can also be instructed to apply a first voltage to the first electric power phase and to apply a second voltage to the second electric power phase and the third electric power phase for a first period. A plurality of nodes in a mesh network can be instructed to perform a plurality of voltage measurements during the first period. Information related to the plurality of voltage measurements taken during the first period can be received from nodes in the mesh network. The information can be processed to determine which nodes are associated with the first electric power phase. Similar steps can be performed to determine which nodes are associated with a second and third electric power phase.

In another aspect, an initial voltage for an initial period can be received. A first voltage for a first period, a second voltage for second period, and a third voltage for a third period can also be received. A plurality of measurements can be taken during the first period, the second period, and the third period. The voltage measurements during two of the first, second, and third periods are similar and the received voltage during the remaining period is dissimilar. Receiving the voltages and taking the voltage measurements occur at nodes within a mesh network.

These illustrative examples are mentioned not to limit or define the disclosure, but to provide examples to aid understanding thereof. Additional examples and further description are provided in the Detailed Description.

DETAILED DESCRIPTION

Aspects of the present invention relate to determining the number of loads associated with each phase in a three-phase electric power system. The loads can be associated with the consumption of electric power at a node, such as a metering device located at a facility. In one aspect, a central device that is connected to such nodes via a smart grid and a radio frequency mesh network can be leveraged to determine a phase in real time. For example, the central device can include a processor that executes one or more computer program modules which can cause a load tap changer having access to a distribution feeder in the smart grid to vary a voltage level supplied across each phase of the power system. Additionally, the central device can communicate with nodes in the mesh network to cause the nodes to perform voltage measurements and to collect information related to such measurements.

According to one implementation, the central device controls a recursive process in which voltage levels are varied depending on phase and voltages are measured. For example, the central device can cause the load tap changer to set the voltage across each phase to an initial level for an initial period. After the initial period has expired, the central device can cause the load tap changer to increase the voltage level applied to a first phase of the power system, e.g., Phase A, by a certain amount, while causing the load tap changer to decrease the voltage level applied to Phase B and Phase C, by a certain amount. The voltage levels can remain in effect for a particular period, during which time the nodes measure a first set of voltage measurements. A second and third set of voltage measurements can be measured by repeating the above steps. For instance, the second set of voltage measurements can be measured in conjunction with an increase in voltage level applied to a second phase, e.g., Phase B, and a decrease in voltage level applied to Phase A and Phase C. The third set of voltage measurements can be measured in conjunction with an increase in voltage level applied to a third phase, e.g., Phase C, and a decrease in voltage level applied to Phase A and Phase B.

According to some examples, after the first, second, and third set of voltage measurements are received at the central device, information related to the voltage measurements can be analyzed to determine an association between nodes and phases, such as an indication of the number of loads associated with a particular phase or the phase associated with each node. The information can be used to make other determinations in other aspects of the invention. Nodes can be configured to measure voltages, optionally store the measured voltages, and send the information related to the measured voltages to the central device. The information can be sent at various times, e.g., batch or real-time as each measurement is taken, according to various implementations. The information can be routed to the central device via one or more nodes in the mesh network.

As used herein, the term “device” refers to any computing or other electronic equipment that executes instructions and includes any type of processor-based equipment that operates an operating system or otherwise executes instructions. A device will typically include a processor that executes program instructions and may include external or internal components such as a mouse, a CD-ROM, DVD, a keyboard, a display, or other input or output equipment. Examples of devices are personal computers, digital assistants, personal digital assistants, cellular phones, mobile phones, smart phones, pagers, digital tablets, laptop computers, Internet appliances, other processor-based devices, and television viewing devices.

The central device10is used as a special purpose computing device to provide specific functionality offered by its applications. In embodiments herein, it acts as a “central” location or hub for receiving information from various nodes in the mesh network15, as well as a central command center for initializing and controlling the features described herein.

As used herein, a “node” refers to a device that can measure voltages at a facility, such as a house, apartment unit or other place of dwelling, or other type of end point that may rely upon electric power. The node can include hardware and software that configures it to communicate with like nodes and/or other devices via mediums to which it has connectivity, such as a smart grid or a mesh network. In one implementation, the node is a meter that measures the consumption of electric power at a facility. Thus, a node can represent the “load” at any given time at a certain location along a distribution feeder in a power system.

As used herein, a “load tap changer” refers to a device that can regulate voltage originating from a power source, such as a substation. The voltage levels can be regulated on a per phase basis.

Claims that follow recite a “computer-readable medium.” A computer-readable medium may comprise, but is not limited to, an electronic, optical, magnetic, or other storage device capable of providing a processor with computer-readable instructions. Other examples comprise, but are not limited to, a floppy disk, CD-ROM, DVD, magnetic disk, memory chip, ROM, RAM, an ASIC, a configured processor, optical storage, magnetic tape or other magnetic storage, flash memory, or any other medium from which a computer processor can read instructions. The instructions may comprise processor-specific instructions generated by a compiler and/or an interpreter from code written in any suitable computer-programming language, including, for example, C, C++, C#, Visual Basic, Java, Python, Perl, JavaScript, and ActionScript.

FIG. 1depicts an exemplary environment for implementing systems described herein. The environment shown inFIG. 1comprises a wired or wireless network5to which a central device10and a load tap changer40are connected. The network5can comprise the Internet. Alternatively, other networks, intranets, or combinations of networks may be used such that devices connected to the network5may communicate with each other. Other environments do not involve a network and may, for example, rely upon a single device or on devices that are directly connected to one another, e.g., the central device10may be directly connected to the load tap changer40. Other alternative networks, computer devices, and electronic device configurations are also possible.

The environment inFIG. 1may also contain a network15. In one implementation, the network15is a wireless mesh network comprising multiple nodes that can communicate with one another to route information to the central device10. Similarly, the nodes in the mesh network15may also route messages from the central device10to other nodes in the mesh network15.FIG. 2depicts individual nodes206a-nin the mesh network15. Additionally, the nodes in the mesh network15can be associated with one of multiple phases107(Phase A),108(Phase B), and109(Phase C) of an electric power distribution system comprising distribution feeder45, as illustrated inFIG. 1. Thus, a node according to aspects herein can function within a mesh network15and a distribution feeder45of an electric power distribution system.

The central device10shown inFIG. 1can include a processor11for executing computer instructions embodied in the load identification application30and an input/output device17connected to the processor11via a bus16. Users can use a display18and one or more user interface devices19, such as a mouse and keyboard, to interact with the central device10. A memory12can include the load identification application30, which can include various computer program modules, such as a load tap changer interface31, a node selector32, an information collector33, and a phase analysis and determination module34.

Each of these modules can be implemented as individual modules that provide specific functionality of the load identification application30. For example, the load tap changer interface31can cause the load tap changer40to vary the voltage level applied to each phase carried by the distribution feeder45. The node selector32can implement various algorithms that can be used to select certain nodes for performing voltage measurements. An information collector33can receive and parse information related to the voltage measurements that are received from one or more nodes in the mesh network15which route the information from the nodes that performed the voltage measurements to the central device10. The phase analysis and determination module34can process the information to determine an association between nodes and phases.

In some implementations, at least some of the above program modules can be located on devices other than the central device10. For example, the phase analysis and determination module34can be executed by a processor on a device that is connected to the device10via the network5or via the network15. In other implementations, the program modules can communicate with one or more other program modules, on the device10or on another device, to provide specific functionality for determining an association between nodes and phases. In these implementations, determining a phase association may represent only one function or feature within a broader software application that provides numerous other additional functions or features. In other implementations, the functionality provided by the various program modules can be implemented in a single module.

FIG. 2illustrates a distribution feeder45that carries power from power source202to nodes206a-nwhich can be located at a facility. The load tap changer40can regulate the voltage level received from the power source202to control the voltage level present at the nodes206a-n.

FIG. 2also illustrates a relationship between the mesh network15and the phases107,108, and109carried by distribution feeder45. Such a relationship exists by way of nodes206a-nwhich are common to the mesh network15and to power distribution feeder45.FIG. 2illustrates four nodes (206a-d) connected to107(Phase A), two nodes (206e-f) connected to108(Phase B), and eight nodes (206g-n) connected to109(Phase C). Although only fourteen nodes are shown, fewer or more nodes may exist. The dotted cloud15represents the mesh network and illustrates that the nodes206a-nalso have a relationship with one another in the mesh network15.

In some systems, a node can include the phase analysis and determination module34. According to these systems, the node can access the stored voltage measurements from a local memory, or another external memory accessible by the node, and determine the phase with which the node is associated. The node can send the results to the central device10instead of the central device10performing the phase analysis and determination to obtain the results.

FIG. 3is a flowchart of an exemplary phase determination method. Phase determination begins at step304where certain of the nodes206a-non the distribution feeder45are selected to participate in the phase determination by performing voltage measurements and sending information related to the voltage measurements to the central device10. In some implementations, various algorithms can be implemented to select certain nodes. For example, nodes can be selected based on their location. Locations that are experiencing rapid growth may be more prone to load imbalances than more stable locations and therefore nodes associated with those locations may be desirable candidates. As another example, nodes that are associated with a facility that is experiencing trouble or inefficient operation may also be desirable candidates. Nodes in proximity to troubled nodes may also be selected according to some algorithms. In other implementations, all nodes located on one or multiple distribution feeders can be selected. Various other algorithms and/or logic can utilize metrics or data associated with various other conditions to determine which nodes will be selected.

At step306, the voltage applied to107(Phase A),108(Phase B), and109(Phase C) can be set to an initial voltage level and held at that level until the system achieves a steady state. In one example, steady state is achieved by applying the initial voltage for an initial period sufficient to allow voltage to propagate throughout the nodes, e.g., thirty minutes. The load tap changer interface31can use a predetermined value for the initial period or can determine the value based on certain data, e.g., historical periods stored in a memory or database accessible by the load tap changer interface31. In some examples, the load tap changer interface31can receive input or an instruction specifying the period.

In other examples, the load tap changer interface31can determine whether the voltage has propagated throughout the nodes. For example, the load tap changer interface31can cause the candidate nodes to measure voltage on demand and send the measured voltages real time to the central device10. The measured voltages can be compared to the steady state voltage level such that measured voltages that are equal to or within an acceptable range of the steady state voltage level can be considered to have received the initial voltage. In some implementations, the central device10may conclude that the initial voltage has been propagated throughout the nodes after a predefined percentage of the nodes have measured a voltage equal to or within an acceptable range of the steady state voltage. Relying on a percentage can effectively exclude from the determination any nodes that may be experiencing trouble.

Certain other implementations can rely on known location data for each node. For example, the load tap changer interface31can cause nodes that are at the farthest points away from the load tap changer40to measure voltages. The initial voltage can be considered fully propagated throughout the nodes when such nodes indicate that they measured a voltage equal to or within an acceptable range of the initial voltage. Similar techniques can be used to verify that additional voltage levels applied to each of the phases, e.g., 2.0 volts above steady state voltage and 1.0 volts below steady state voltage, have been propagated throughout the nodes.

Voltages can be measured at step308.FIG. 4illustrates an exemplary process for measuring voltages. At step404, the voltage applied to Phase A is set to a first voltage, and the voltage applied to Phase B and Phase C is set to a second voltage. In one example, the voltage applied to Phase A is 2 volts higher than the initial voltage level, whereas the voltage applied to Phase B and Phase C is 1 volt lower than the initial voltage level. Phase B may receive a voltage that is different from that received by Phase C in some implementations.

The amount of voltage increase and decrease may be different in some implementations, so long as the voltage level is within acceptable tolerances, i.e., between 114 volts and 126 volts. Thus, a voltage differential of 3 volts (+2 volt increase and a −1 volt decrease) can be used. Other voltage differentials can also be used.

The selected nodes can begin measuring voltage at step410. In one system, the voltages can be measured for a first period. The first period can be the same as or different from the initial period used at step306. Similar to the initial period, certain data may be evaluated to determine the duration of the first period or, alternatively, the duration of the first period can be communicated to the node. Measurements can be taken over the first period at certain intervals of time. For example, nodes can measure voltages once a minute. In one implementation, the nodes are programmed to record voltage measurements at a predefined time interval. In other implementations, the nodes can receive a time interval from the central device10. Thus, according to these implementations, the central device10can effectively control the number of measurements taken by each node, i.e., requesting that a node measure voltage every minute for thirty minutes to arrive at a total of thirty measurements.

Information related to the voltage measurements can be optionally stored by the nodes at step412. Storing the information at the nodes can be particularly useful when information for multiple measurements is sent to the central device10in a single message or when the nodes include the phase analysis and determination module. The voltage measurements can be sent to the central device10at a determined or scheduled time or based on network activity. For example, information can be sent at a time during which the load on the mesh network15is relatively low, i.e., relatively few messages are being routed. In some implementations, voltage measurements may not be stored, particularly in those systems where voltage measurements are sent in real time, e.g., after each voltage measurement is performed, to the central device10.

The process determines whether the end of the first period has been reached at step414. If so, then the first set of voltage measurements have been effectively completed at reference416. Processing can resume at step406where Phase B is set to a first voltage (e.g., the same first voltage applied to Phase A in step404) and Phase A and Phase C are set to a second voltage (e.g., the same second voltage applied to Phase B and Phase C in step404). Steps410and412are repeated until a second period, which can be the same as or different from the first period and/or initial period, expires at step414. If the end of the second period has been reached, the second set of voltage measurements have been effectively completed at reference418. Steps410and412are repeated after processing resumes at step408, where a first voltage is applied to Phase C (e.g., the same first voltage applied to Phase A in step404and to Phase B in step406) and a second voltage is applied to Phase A and to Phase B (e.g., the same second voltage that was applied to Phase B and to Phase C in step404and to Phase A and Phase C in step406). The third set of voltage measurements are effectively completed at reference420after a third period has expired at decision step414. Voltage measurements can also be taken during the initial period according to some implementations to, for example, verify that the steady state voltage is achieved by the conclusion of the initial period.

In some implementations, the first period, the second period, and the third period are equivalent. They may also be different in other implementations. Dotted line402a, solid line402b, and bold line402cofFIG. 4join the respective steps performed for each of the voltage settings applied at steps404,406, and408, respectively.

FIG. 5aandFIG. 5bwork in conjunction with one another to illustrate an exemplary voltage collection process. Both figures illustrate several periods over which voltage measurements are collected: steady state505, first period510, second period515, and third period520. Each of the periods can occur at different times. For example, steady state505represents the initialization period from 0 minutes to 30 minutes; first period510ranges from 30 minutes to 60 minutes; second period515ranges from 60 minutes to 90 minutes; and third period520ranges from 90 minutes to 120 minutes.

As previously discussed, the periods may be different, e.g., more or less than 30 minutes. Additionally, each period may begin at a particular time offset. The first period510, for example, can range from 40 minutes to 60 minutes, i.e., starting ten minutes after steady state505has ended. Such a time offset may be required in some implementations to allow the new voltage level to propagate throughout the nodes. The load tap changer interface31can apply a fixed or variable time offset between each phase, in one example. For the sake of simplicity, the time ranges inFIG. 5aandFIG. 5bdo not reflect a time offset (i.e., first period510begins at the end of steady state period505).

Each of the periods inFIG. 5aillustrates a phase of the distribution feeder that is varied by a certain voltage amount (e.g., +2.0 volts or −1.0 volts) with respect to the steady state voltage level. For example, Phase A is increased by 2 volts above the steady state voltage and Phase B and Phase C are decreased by 1 volt below the steady state voltage for the first period510; Phase B is increased by 2 volts above the steady state voltage and Phase A and Phase C are decreased by 1 volt below the steady state voltage for the second period; and Phase C is increased by 2 volts above the steady state voltage and Phase A and Phase B are decreased by 1 volt below the steady state voltage for the third period.

As illustrated inFIG. 5b, the first period510, second period515, and third period520each contain time intervals at which voltage measurements are performed by Node1, Node2, and Node3. For example, voltage measurements510d,510e, and510fcan correspond to voltage measurements taken by Node1at times510a,510b, and510c, respectively, during the first period510. Voltage measurements510g,510h, and510ican correspond to voltage measurements taken by Node2at times515a,515b, and515c. When, for example, Phase A is decreased by 1 volt below the steady state voltage for the second period515(as shown inFIG. 5a), Node1will perform new voltage measurements515d,515e, and515fthat correspond to time intervals515a,515b, and515c, respectively. Voltage measurement values may also change for Node2and Node3as indicated inFIG. 5bin response to the voltage level changing as illustrated inFIG. 5a.

Returning toFIG. 3, the process resumes at step310where information related to the voltage measurements is received. In one implementation, the information is received after all measurements have been received for the first period510, the second period515, and the third period520, as shown inFIGS. 5aand5b. In another implementation, the information can be received at the conclusion of each period. In yet another implementation, the information may be received real-time, e.g., after each measurement is taken by a node.

Examples of the information received include the measured voltage values, an identifier associated with the node that performed the voltage measurement, the time, either absolute or relative, at which the node measured the voltage. The identifier can be a street address, device serial number, or otherwise any identifier that can associate the node with a facility or physical location where the measurement was performed. Various other data can be included in the information, at least some of the data being uniquely associated with the voltage measurements.

The information related to the voltage measurements can be processed to determine an association between nodes and phases at step312.FIG. 6, in conjunction withFIGS. 5aand5b, illustrates exemplary steps for processing the information. At step604, the information can be parsed such that voltage measurements and related information pertaining to a particular node are grouped together. The information within each node group can be further identified by the time at which the voltage measurements were performed. The information can be stored at step606and a calculation can be performed at step608.

Hypothetical voltage measurements performed by three nodes (Node1, Node2, and Node3) inFIG. 5bwill now be considered for the purpose of illustrating an exemplary calculation at step608. While only three nodes are identified in the hypothetical, many more nodes may exist. During the first period510, Node1measured 2.1 volts above the steady state voltage (510d) at 40-minute mark510a,1.9 volts above the steady state voltage (510e) at 50-minute mark510b, and 2.0 volts above the steady state voltage (510f) at 60-minute mark510c. In one example, each of the measurements can be averaged to arrive at a representative measurement of 2.0 volts above steady state for the first period510. As illustrated inFIG. 5b, the voltage measurements performed during a particular period may be at least slightly different. Thus, in one example, measurements can be averaged to smooth out any inconsistencies in voltage measurements, which could be due to external factors (e.g., distance from substation and temperature) which may make it more difficult for the load tap changer40to maintain voltage levels. In addition to an average, other mathematical functions can be performed to represent the multiple measurements taken by Node1. In other examples, the voltage measurements can be expressed as a range. In the example above, Node1's voltage measurements can be expressed as a range of 1.9 volts to 2.1 volts, which can also be used to provide an association between Node1and a phase.

A representative voltage measurement or range can be compared to an acceptable range or tolerance level for each phase to determine an association between the voltage measurement and a particular phase. In one example, an acceptable range can be +/−2% of the voltage level that is applied to a phase. For example, if a voltage of 122 volts is applied to Phase A, voltage measurements within a range of 119.6 and 124.4 (i.e., +/−2% of 122 volts) can be associated with Phase A. Similar comparisons can be performed between voltage measurements and Phase B and Phase C.

A difference between each of Node1's voltage measurements and the steady state voltage can be calculated to provide an association between Node1and a phase, such as to which phase Node1belongs. For example, a difference equal to or within acceptable range of 2.0 volts can indicate that Node1is located on Phase A because the load tap changer40provided a voltage of 2.0 volts above the steady state voltage across107(Phase A) of distribution feeder45. Thus, Node1's measurement of 2.0 volts above steady state is reflective of its measuring the increased voltage of 2.0 volts applied to Phase A. Contrarily, a difference between Node2and Node3's voltage measurements and the steady state voltage during period510indicates that Node2and Node3are not located on Phase A.

During the first period510, Node2and Node3measured voltages equal to or in proximity of 1.0 volts below the steady state voltage, which indicates that Node2and Node3are both on either Phase B or Phase C. In particular, Node2and Node3measured 1.1 volts below the steady state voltage (510gand510j) at 40-minute mark510a,0.9 volts below the steady state voltage (510hand510k) at 50-minute mark510b, and 1.0 volts below the steady state voltage (510iand510l) at 60-minute mark510c.

A similar calculation of Node2's measurements for the second period515indicates that Node2is located on Phase B because its voltage measurements are equal to or within an acceptable range of the 2.0 volts above the steady state voltage to which Phase B was set for the second period515. For example, during the second period515, Node2measured 2.1 volts above the steady state voltage (515g) at 70-minute mark515a,1.9 volts above the steady state voltage (515h) at 80-minute mark515b, and 2.0 volts above the steady state voltage (515i) at 90-minute mark515c. Node1and Node3's measurements during second period515indicate that they are not on Phase B during this period. Particularly, during the second period515, Node1and Node3measured 1.1 volts below the steady state voltage (515dand515j) at 70-minute mark515a,0.9 volts below the steady state voltage (510eand510k) at 80-minute mark515b, and 1.0 volts below steady state voltage value (515fand515l) at 90-minute mark515c.

Similar analysis for the third period520provides an indication that Node3is located on Phase C. During the third period, Node3measured voltages equal to or within an acceptable range of 2.0 volts above the steady state voltage to which Phase C was set for the third period520. For example, during the third phase520, Node3measured 2.1 volts above steady state voltage value (520j) at 100-minute mark520a,1.9 volts above the steady state voltage (520k) at 110-minute mark520b, and 2.0 volts above the steady state voltage (520l) at 120-minute mark520c. Node1and Node2's measurements during third period520indicate that they are not on Phase C during this period. Particularly, during the third period520, Node1and Node2measured 1.1 volts below steady state voltage value (520dand520g) at 100-minute mark520a,0.9 volts below steady state voltage value (520eand520h) at 110-minute mark520b, and 1.0 volts below steady state voltage value520fand520iat 120-minute mark520c.

According to some examples, the measurements and calculations need not be performed for the third period because, of the nodes that were selected to perform voltage measurements, the nodes that do not have an association with Phase A or Phase B can be associated with Phase C. Put another way, after an association has been determined for any two of the three phases, no further measurement and calculation may be required to determine an association between the remaining nodes and the remaining third phase, according to some examples. Because each of them is the only remaining nodes or phase, they necessarily can be associated with each other. Some implementations may nevertheless perform measurements during the third phase to, for example, identify nodes that may not be properly associated with any of the phases. Such nodes can have measurements that are not within the acceptable range of any of the phases. Information related to these nodes may be analyzed to determine whether troubleshooting or dispatch, for example, may be required to correct any issues that may exist at the facility associated with the nodes.

Many other modifications, features and embodiments of the present invention will become evident to those of skill in the art. Accordingly, it should be understood that the foregoing relates only to certain aspects or implementations of the invention, which are presented by way of example rather than limitation. Numerous changes may be made to the examples described herein without departing from the spirit and scope of the invention as defined by the following claims.