WO2021240835A1

WO2021240835A1 - A method and apparatus for transmission branch switching for overload mitigation

Info

Publication number: WO2021240835A1
Application number: PCT/JP2020/037355
Authority: WO
Inventors: Nagaraj Neradhala
Original assignee: Hitachi, Ltd.
Priority date: 2020-05-28
Filing date: 2020-09-30
Publication date: 2021-12-02
Also published as: JP2023517005A; EP4158748A1; JP7461492B2

Abstract

In one embodiment, the present invention relates to a method and device for selecting a transmission branch from a plurality of transmission branches in a power system. At least one overload in the power system is detected. At least one radial branch and critical branch are eliminated from the plurality of transmission branches to obtain a first set of transmission branches. At least one pair of analog and digital parameters for each of the plurality of transmission branches are calculated, compared with one or more thresholds and the plurality of transmission lines are filtered to obtain a second set of transmission branches. An outage is simulated in the power system and stability of power system is checked based on one or more dynamic constraints to identify and eliminate a weakest branch from second set of transmission branch. Rank of the second set of transmission branches is rearranged and a transmission branch is selected for switching.

Description

A METHOD AND APPARATUS FOR TRANSMISSION BRANCH SWITCHING FOR OVERLOAD MITIGATION

The present subject matter relates to the field of power systems. More particularly, the present subject matter relates to a switching of transmission branches for overload mitigation in the power systems.

Electric grid is made up of plurality of transmission and distribution lines and power generating sources (e.g. generators). In the electric grid, there may occur a scenario where one or more transmission branches or power generation sources fail. This causes overload in the system. Overload may occur in real time inside the electric grid networks. Overloads cause problems with generation and distribution of power inside the electric grid and therefore the overloads need to be mitigated.

Existing systems of relieving overload in the electric grid networks requires adjusting schedule of the power generating sources. Adjusting schedule involves re-dispatching power of power generation sources, for example, generators. However, there is operating cost involved in such re-dispatching power of power generation sources. Thus, there is a need in the art to for finding a novel manner of mitigating overloads in the electric grid networks.

Also, the current systems of relieving overloads do not consider scenarios where an overload can occur at a future point of time. For example, after switching of a transmission branch is performed, a scenario may arise where the power system may fail again. Thus, a power system is required which checks the possibility of occurrence of overload in future and is accordingly prepared for such overload.

Summary

In one embodiment, the present invention relates to a method and system for selecting a transmission branch from a plurality of transmission branches in a power system. At least one overload in the power system is detected. At least one radial branch and critical branch are eliminated from the plurality of transmission branches to obtain a first set of transmission branches. At least one pair of analog and digital parameters for each of the plurality of transmission branches are calculated, compared with one or more thresholds and the plurality of transmission lines are filtered to obtain a second set of transmission branches. An outage is simulated in the power system and stability of power system is checked based on one or more dynamic constraints to identify and eliminate a weakest branch from second set of transmission branch. Rank of the second set of transmission branches is re-arranged, and a transmission branch is selected for switching.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and regarding the accompanying figures, in which:
Figure 1 illustrates an exemplary environment in accordance with some embodiments of the present disclosure; Figure 2 shows an electric grid in accordance with some embodiments of the present disclosure; Figure 3A illustrates a flowchart showing a method in accordance with some embodiments of present disclosure; Figure 3B illustrates a flowchart showing a method in accordance with some embodiments of present disclosure; Figure 4 illustrates calculating Thevenin equivalent circuit in accordance with some embodiments of present disclosure; Figure 5 illustrates plotting a graph in accordance with some embodiments of present disclosure; Figure 6 illustrates a block diagram of computing device in accordance with some embodiment of the present disclosure.

It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative systems embodying the principles of the present subject matter. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and executed by a computer or processor.

DESCRIPTION OF THE EMBODIMENTS

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.

The terms “includes”, “including”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that includes a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “includes… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.

In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.

Various terms used in the present invention are described below:

Power system: Power system may be defined as a network containing at least one transmission line and power generating sources.
Transmission branch: Transmission branch may be defined as electrical cable connecting two nodes.
Nodes: A node is a point of interconnections or junctions between one or more power system components. The node may be defined as endpoint of the transmission branch. The node may be connected to one or more power generation sources and/or loads. The power generation sources may include for example, generators. The examples of node may include load, compensation devices or general power system equipment.
Overload: Overload may be defined as a situation where capacity of equipments present in the power system is violated.
Outage: Outage in the power system may be defined as a scenario where one or more network element (for example, a transmission line or one or more power generation sources) fails. Thus, overload is a consequence of outage.
weakest node: The weakest node is a node which has tendency to violate at least one of the transient stability constraints, like angle stability, voltage stability and frequency stability.
Angle Stability: The node which have less short circuit MVA
Voltage stability: The generators with minimum reactive power margin and loads with maximum change in nodal reactive power loss within the zone
Frequency stability: The node which has less inertia or high rate of change of frequency for small/large disturbance.
Static limits: During steady state operations, each node/equipment will have operational constraints which are expressed in minimum and maximum limits as per planning criteria or some time by system operator. These are the limits of the network which can withstand violations for seconds to few minutes. The calculations for such limits take shorter time frame, say few milli seconds. For example, 400kV node with +/- 5% variation in voltage is allowed, etc.
Dynamic constraints: These are the constraints to be checked in transient conditions. These are the limits of the network which need to be checked and defined in milli seconds timeframes. The calculations for such limits take longer time frame, say seconds/minutes. For example, the angle stability at node will be stable if fault clearance is less than 120 milli seconds, otherwise the system will be unstable.
weakest node: The weakest node is a node which has tendency to violate at least one of the transient stability constraints, like angle stability, voltage stability and frequency stability.
Angle Stability: The node which have less short circuit MVA
Voltage stability: The generators with minimum reactive power margin and loads with maximum change in nodal reactive power loss within the zone
Frequency stability: The node which has less inertia or high rate of change of frequency for small/large disturbance.
Static limits: During steady state operations, each node/equipment will have operational constraints which are expressed in minimum and maximum limits as per planning criteria or some time by system operator. These are the limits of the network which can withstand violations for seconds to few minutes. The calculations for such limits take shorter time frame, say few milli seconds. For example, 400kV node with +/- 5% variation in voltage is allowed, etc.
Dynamic constraints: These are the constraints to be checked in transient conditions. These are the limits of the network which need to be checked and defined in milli seconds timeframes. The calculations for such limits take longer time frame, say seconds/minutes. For example, the angle stability at node will be stable if fault clearance is less than 120 milli seconds, otherwise the system will be unstable.

The present invention will now be described with the help of drawings.

Referring to figure 1, a power system 100 in accordance with an embodiment is disclosed. Figure 1 discloses the system 100 comprising an electric grid 103, a communication network 102 and a computing device 105. The electric grid 103 may be in communication with the computing device 105 via the communication network 102.

The electric grid 103 may contain a plurality of transmission lines and one or more power generation sources. A transmission line connected between two nodes is termed as a transmission branch. The nodes may be connected to one or more power generation sources and/or loads. The electric grid 103 is exemplified in figure 2. As shown in figure 2, transmission branches are connected between the nodes, 204, 206, 210, 212, 214, , 220, 222, 226, 230.

Some of the transmission branches out of the plurality of transmission branches in the power system 100 may be categorised as critical branches and radial branches. Critical branches are the one which are necessary for the operation of the power system 100 and without which the power system 100 may not work properly. In one embodiment, the critical branches are pre-defined by a system operator. Radial transmission branches may be defined as transmission branches which may be directly connected to the nodes. For example, as shown in figure 2, transmission branches connected between

nodes

226 and 230, 204 and 206, 212 and 214 are radial lines since they are directly connected to the generators (G).

Referring to figure 2, there may occur a scenario where transmission branch connected between 210 and 212 fails, for example, due to power supply failure. Due to this, overload may occur between transmission branch connected between 210 and 226. To mitigate the overload, switching of transmission branch is required. The present disclosure proposes a novel way of switching of power supply from one transmission branch to another. The switching requires selecting a transmission branch for switching with lowest computations.

Referring to figure 1, the computing device 105 may be any general purpose computing device comprising a processor 110 and a memory 112 coupled to the processor 110 and configured to store instructions to be executed by the processor 110. The computing device 105 will be described later in detail.

Referring to figure 3, a method for selecting a transmission branch from a plurality of transmission branches in the power system is described.

At step 302, the method comprises detecting at least one overload in the power system. The processor 110 may detect one or more overloads occurring in the power system 100. The one or more overloads may occur due to failure of one or more transmission branch in the electric grid 103. In one embodiment, the one or more overloads may occur due to change in loads in the power system. In yet another embodiment, the one or more overloads may occur due to intermittent renewable energy generations. For example, as explained above with respect to figure 2, the outage may occur in transmission branch connected between 210 and 212 which may cause overload between the

branches

210 and 226. In one embodiment, the computing device 105 may include an overload detection module (not shown). The overload detection module may detect one or more overloads occurring in the power system 100.

At step 304, the method comprises eliminating at least one radial branch and at least one critical branch from the plurality of transmission branches to obtain a first set of transmission branches. As defined earlier, the critical branches are pre-defined by the system operators. Further, the radial lines may be the one directly connected to the one or more power generation sources and/or one or more loads in the power system. The processor 110 is configured to eliminate the number of radial branches and the critical branches from the total number of transmission branches present in the electric grid. The remaining set of branches obtained after eliminating the critical branches and the radial branches is termed as a first set of transmission branches. The at least one critical branch and the at least one radial branch may not be considered for switching when switching the transmission branch in case of power supply failure. Thus, for example, in the electric grid, there may be 100 (in number) transmission branches out of which 10 (in number) may be critical branches and another 10 (in number) may be radial branches. Hence, the first set of transmission branches may include 80 transmission branches i.e. eliminating 20 (10 radial and 10 critical) branches from total of 100 transmission branches. The remaining 80 transmission branches may be processed further to select a transmission branch to switch power supply when the overload occurs in the power system 100.

At step 306, the method comprises calculating at least one pair of analog and digital parameters for each of the second set of transmission branches. The processor is configured to obtain the analog and digital parameters for each of the first set of transmission branches obtained in the above step . For example, the analog and digital parameters may be obtained for all the 80 transmission branches (as per the above example).

To obtain the analog and digital parameters of the transmission branches, Thevenin equivalent circuit is obtained for each of the transmission branches. Figure 4 describes a Thevenin equivalent circuit obtained for any one transmission branch connected between 2 nodes. Calculating Thevenin equivalent is known in the art and the description for calculating the Thevenin equivalent is omitted here in the description. With the Thevenin equivalent circuit, the one or more analog and digital parameters are obtained. The one or more analog and digital parameters comprises one or more of voltage, impedance, angle, voltage deviation, impedance deviation, angle deviation , switchgear status (ON/OFF). The switchgear status may include line breaker status (ON/OFF), isolators status (ON/OFF).

From the Thevenin equivalent circuit of figure 4:

Where,
V_s is vector, voltage and phase at the sending end (at one side of transmission branch);
V_r is vector, voltage and phase at the receiving end (at other side of transmission branch);

Z is the complex impedance of the line / transfer of the branch from Zbus matrix;
I is the current phasor.

The complex AC power transmitted to the receiving end of the transmission branch can be calculated as follows:

The branch model can be more realistic with resistive components in impedance. The power transfer across the line is therefore:

P = real power across the line
Q = Reactive power across the line
δ= Power angle
θ= impedance angle

With the above power transfer equations, angle and voltage thresholds may be calculated based on “Available Transfer Capacity” (ATC) with known variables of transfer impedance and voltage.
ATC may be defined as:
ATC = rating of the branch - power flow in the branch = P_rating - P_flow
Where, ATC is the maximum allowable power in the branch.

Similarly, the simplest form of power flow equations can also be represented, if we neglect resistance and capacitance of the branches and represent the line as lossless.

The above power flow equations can be used to calculated ATC value.

The method then proceeds to step 308. At step 308, the method comprises comparing the calculated at least one pair of analog and digital parameters with one or more thresholds.

At step 310, the method comprises filtering the first set of transmissions branches based on the comparison to obtain a second set of transmission branches.

The

step

308 and 310 may be performed by plotting a graph by the computing device 105. The graph may be plotted between one or more analog and/or digital parameters. For example, the graph may be plotted between analog and analog parameters, or between digital and digital parameters, or between analog and digital parameters.

Figure 5 discloses plotting of a graph between parameters angle and voltage. The angle and voltage parameters are obtained from a Thevenin equivalent circuit. The plotted angle and voltage parameters are compared with one more thresholds. The threshold is defined by system operator of the power system 100 or by calculating based on static limits and an available transfer capacity (ATC) using one or more power flow equations as defined above. As shown in figure 5, the bold line defines stable operating area boundary i.e. thresholds. The angle and voltage parameters values falling outside the operating area boundary are eliminated. This means that the transmission branches having analog and digital parameter values falling outside the operating area boundary are eliminated from further screening. The remaining transmission branches thus obtained are termed as second set of transmission branches. The figure 5 also shows a dotted line. This dotted line may be termed as a margin of safety and may be defined by a system operator.

By way of an example, a graph for all the 80 transmission branches (i.e. transmission branches obtained after excluding the radial and critical transmission branches) present in the electric grid is plotted. Analog and digital parameters for each of the 80 transmission branches are compared with the one or more thresholds and transmission branches whose analog and digital parameters fall outside the threshold are eliminated. Thus, in this example, there may be 50 branches which may be eliminated according to the described method. Thus, the second set of transmission lines may be equal to 30 (total lines 80 minus 50 branches for which the analog and digital parameters fall outside the threshold).

At step 314, the method comprises ranking each of the second set of transmission branches based on one or more objective functions. The processor is configured to rank each of the second set of transmission branches based on one or more objective functions. Thus, considering above example, 30 transmission branches obtained as the second set of transmission lines are ranked by the processor. The one or more objective functions comprises of, for example, but not limited to, minimum losses, minimum generation cost, minimum angle deviation, minimum voltage deviation. In one embodiment, the one or more objective functions are solved using one or more optimization methods. In one embodiment, the objective functions are defined by the system operator of the power system. For example, the system operator may define “minimum losses” as one of the objective function by which the transmission branches may be ranked. The system operator may define that the power system should have minimum losses by selecting “minimum losses” as one of the objective function. Once the objective parameter is selected, the processor ranks the transmission branches by mitigating or eliminating the overloads in the branches. The ranking will be done such that there is minimum losses in the power system. For example, using the transmission branch ranked as “one” is supposed to have minimum losses followed by other ranked transmission branches.

At step 316, the method comprises simulating an outage in the power system to rearrange the ranking of each of the second set of transmission branches. The outage may be simulated to check possibility of future failures in the power system. The future failure may occur, for example, when a transmission branch is selected for switching from the second set of transmission branches and an outage occurs in future resulting in overload in the power system 100. Thus, to make the power system ready for future, the power system is checked for one more outage in the system 100. One more outage is a forced outage which is done by simulation techniques known in the art. This ensures that the power system 100 is ready for future outage, if it happens in the power system.

At step 318, the method comprises checking stability of the power system based on one or more dynamic constraints. Once the outage is simulated in the power system, the processor 110 is configured to check the stability of the power system in the simulated environment. The system operator of the computing device 105 may simulate the power system 100 in the simulated environment and the stability of the power system after outage is checked for a predetermined period of time. Checking the stability of the system comprises checking stability of the one or more transmission branches and the node in the electric grid 103. The stability may include how stable the power system is after outage has occurred. This includes checking if there occurs another outage/overload in the power system after lapse of the pre-determined period of time. In one embodiment, the computing device 105 may include stability analysis module (not shown) to check the stability of the power system 100.

The stability of the power system includes at least one of transient stability of the power system, voltage stability, frequency stability and angle stability. In one embodiment, the stability may include checking if there is violation in any of the dynamic constraints of the power system. The dynamic constraints may include angle, voltage and frequency. However, the dynamic constraint may not be limited to the one defined here. Thus, in the simulated environment, the processor 110 is configured to check if there is any change in any of the dynamic constraints i.e. angle, voltage or frequency of each of the transmission branch. If there is no violation in dynamic constraints, the processor 110 is configured to determine that the power system is stable. Alternatively, if there is violation in dynamic constraints, the processor 110 is configured to identify the transmission branch (from the first set of transmission branch) which is violating the dynamic constraints as the weakest branch/node in the power system.

At step 320, the method comprises identifying one or more weakest transmission branch out of the second set of transmission branches in the power system based on the result of the stability of the power system. The weakest transmission branch may include the transmission branch of the second set of transmission branches for which there is maximum change in the dynamic constraints. For example, the transmission branch ranked as number one may undergo maximum change in value of angle or voltage when simulated for the predetermined amount of time. Thus, the transmission branch ranked as number one may be identified as the weakest node.

At step 322, the method comprises eliminating the one or more identified weakest transmission branch from the second set of transmission branches. The processor is configured to eliminate the identified one or more weakest transmission branch from the second set of transmission branches. Thus, the second set of transmission branch may be updated by eliminating weakest transmission branch.

At step 324, the method comprises rearranging the rank of the second set of transmission branches after eliminating the one or more identified weakest transmission branch. Once the second set of transmission branch is updated, the processor is configured to rearrange the rank of the second set of transmission branches. For example, as explained above, the transmission branch with rank “one” may be identified as the weakest transmission branch. Thus, the transmission branch with rank “one” may be eliminated (since it’s the weakest branch) and the transmission branch with rank “two” may now become transmission branch with rank “one. Thus, the processor updates the second set of transmission branch to obtain rearranged rank of the remaining transmission branches of the second set of transmission branches.

At step 326, the method comprises selecting a transmission branch from the second set of transmission branches based on the rearranged rank. The processor may select a transmission branch based on the rearranged rank of the transmission branches present in the second set of transmission branches. For example, the transmission branch with rank “one” may be selected for switching. The selected transmission branch may be used for the branch switching to mitigate overload occurring in the power system 100.

In one embodiment, the steps 316 to 326 may be eliminated. Thus, after the second set of transmission branches are ranked, a transmission branch is selected based on the ranking to mitigate or eliminate the overload occurring in the power system 100.

The order in which the method 300 is described may not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

Computing Device
Figure 6 illustrates a block diagram of an exemplary computing device 105 for implementing embodiments consistent with the present disclosure. The computing device 105 may include the central processing unit (“CPU” or “processor”) 110. The processor 110 may include specialized processing units such as, integrated system (bus) controllers, memory management control units, floating point units, graphics processing units, digital signal processing units, etc. The processor 110 may be disposed in communication with one or more input/output (I/O)

devices

609 and 610 via I/O interface 601. The computing device 105 may also include stability analysis module and overload detection module.

The I/O interface 601 may employ communication protocols/methods such as, without limitation, audio, analog, digital, monoaural, RCA, stereo, IEEE-1394, serial bus, universal serial bus (USB), infrared, PS/2, BNC, coaxial, component, composite, digital visual interface (DVI), high-definition multimedia interface (HDMI), RF antennas, S-Video, VGA, IEEE 802.n /b/g/n/x, Bluetooth, cellular (e.g., code-division multiple access (CDMA), high-speed packet access (HSPA+), global system for mobile communications (GSM), long-term evolution (LTE), WiMax, or the like), etc.

Using the I/O interface 601, the computing device 105 may communicate with one or more I/

O devices

609 and 610. For example, the input devices 609 may be an antenna, keyboard, mouse, joystick, (infrared) remote control, camera, card reader, fax machine, dongle, biometric reader, microphone, touch screen, touchpad, trackball, stylus, scanner, storage device, transceiver, video device/source, etc. The output devices 610 may be a printer, fax machine, video display (e.g., cathode ray tube (CRT), liquid crystal display (LCD), light-emitting diode (LED), plasma, Plasma display panel (PDP), Organic light-emitting diode display (OLED) or the like), audio speaker, etc.

In some embodiments, the processor 110 may be disposed in communication with the communication network 102 via a network interface 603. The network interface 603 may communicate with the communication network 611. The network interface 603 may employ connection protocols including, without limitation, direct connect, Ethernet (e.g., twisted pair 10/100/1000 Base T), transmission control protocol/internet protocol (TCP/IP), token ring, IEEE 802.11a/b/g/n/x, etc. The communication network 611 may include, without limitation, a direct interconnection, local area network (LAN), wide area network (WAN), wireless network (e.g., using Wireless Application Protocol), the Internet, etc. Using the network interface 603 and the communication network 611, the computing device 105 may communicate with an electric grid 612 for screening contingencies in the electric grid 102. The network interface 603 may employ connection protocols include, but not limited to, direct connect, Ethernet (e.g., twisted pair 10/100/1000 Base T), transmission control protocol/internet protocol (TCP/IP), token ring, IEEE 802.11a/b/g/n/x, etc.

The communication network 611 includes, but is not limited to, a direct interconnection, an e-commerce network, a peer to peer (P2P) network, local area network (LAN), wide area network (WAN), wireless network (e.g., using Wireless Application Protocol), the Internet, Wi-Fi and such. The first network and the second network may either be a dedicated network or a shared network, which represents an association of the different types of networks that use a variety of protocols, for example, Hypertext Transfer Protocol (HTTP), Transmission Control Protocol/Internet Protocol (TCP/IP), Wireless Application Protocol (WAP), etc., to communicate with each other. Further, the first network and the second network may include a variety of network devices, including routers, bridges, servers, computing devices, storage devices, etc.

In some embodiments, the processor 110 may be disposed in communication with a memory 112 (e.g., RAM, ROM, etc. not shown in Figure 6) via a storage interface 604. The storage interface 604 may connect to memory 112 including, without limitation, memory drives, removable disc drives, etc., employing connection protocols such as, serial advanced technology attachment (SATA), Integrated Drive Electronics (IDE), IEEE-1394, Universal Serial Bus (USB), fibre channel, Small Computer Systems Interface (SCSI), etc. The memory drives may further include a drum, magnetic disc drive, magneto-optical drive, optical drive, Redundant Array of Independent Discs (RAID), solid-state memory devices, solid-state drives, etc.

The memory 112 may store a collection of program or database components, including, without limitation, user interface 606, an operating system 607 etc. In some embodiments, computing device 105 may store user/application data 606, such as, the data, variables, records, etc., as described in this disclosure. Such databases may be implemented as fault-tolerant, relational, scalable, secure databases such as Oracle or Sybase.

The operating system 607 may facilitate resource management and operation of the computing device 105. Examples of operating systems include, without limitation, Apple Macintosh OS X, Unix, Unix-like system distributions (e.g., Berkeley Software Distribution (BSD), FreeBSD, NetBSD, OpenBSD, etc.), Linux distributions (e.g., Red Hat, Ubuntu, Kubuntu, etc.), IBM OS/2, Microsoft Windows (XP, Vista/7/8, etc.), Apple iOS, Google Android, Blackberry OS, or the like.

Further, as used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a field-programmable gate arrays (FPGA), Programmable System-on-Chip (PSoC), a combinational logic circuit, and/or other suitable components that provide the described functionality. The modules when configured with the functionality defined in the present disclosure will result in a novel hardware.

Furthermore, one or more computer-readable storage media may be utilized in implementing embodiments consistent with the present disclosure. A computer-readable storage medium refers to any type of physical memory on which information or data readable by a processor may be stored. Thus, a computer-readable storage medium may store instructions for execution by one or more processors, including instructions for causing the processor(s) to perform steps or stages consistent with the embodiments described herein. The term “computer-readable medium” should be understood to include tangible items and exclude carrier waves and transient signals, i.e., be non-transitory. Examples include Random Access Memory (RAM), Read-Only Memory (ROM), volatile memory, non-volatile memory, hard drives, CD ROMs, DVDs, flash drives, disks, and any other known physical storage media.

Still further, the code implementing the described operations may be implemented in “transmission signals”, where transmission signals may propagate through space or through a transmission media, such as, an optical fibre, copper wire, etc. The transmission signals in which the code or logic is encoded may further comprise a wireless signal, satellite transmission, radio waves, infrared signals, Bluetooth, etc. The transmission signals in which the code or logic is encoded is capable of being transmitted by a transmitting station and received by a receiving station, where the code or logic encoded in the transmission signal may be decoded and stored in hardware or a non-transitory computer readable medium at the receiving and transmitting stations or devices.

When a single device or article is described herein, it will be readily apparent that more than one device/article (whether or not they cooperate) may be used in place of a single device/article. Similarly, where more than one device or article is described herein (whether or not they cooperate), it will be readily apparent that a single device/article may be used in place of the more than one device or article or a different number of devices/articles may be used instead of the shown number of devices or programs. The functionality and/or the features of a device may be alternatively embodied by one or more other devices which are not explicitly described as having such functionality/features. Thus, other embodiments of the invention need not include the device itself.

Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

100 Power system
102 Communication network
103 Electric grid
105 Computing device
202-232 Nodes
110 Processor
112 Memory
300 Method
302-326 Method steps
601 I/O Interface
603 Network Interface
604 Storage Interface
606 User Interface
607 Operating System
608 Web Server
609 Input Devices
610 Output Devices

Claims

A method (300) for selecting a transmission branch from a plurality of transmission branches in a power system (100), the method (300) comprises:
detecting (302) at least one overload in the power system;
eliminating (304) at least one radial branch and at least one critical branch from the plurality of transmission branches to obtain a first set of transmission branches;
calculating (306) at least one pair of analog and digital parameters for each of the first set of transmission branches;
comparing (308) the calculated at least one pair of analog and digital parameters with one or more thresholds;
filtering (310) the plurality of transmissions branches based on the comparison to obtain a second set of transmission branches;
ranking (312) each of the second set of transmission branches based on one or more objective functions;
simulating (314) an outage in the power system to rearrange the ranking of each of the second set of transmission branches;
checking (316) stability of the power system based on one or more dynamic constraints;
identifying (320) one or more weakest transmission branch out of the second set of transmission branches in the power system based on the result of the stability of the power system;
eliminating (322) the one or more identified weakest transmission branch from the second set of transmission branches;
rearranging (324) the rank of the second set of transmission branches after eliminating the one or more identified weakest transmission branch; and
selecting (326) a transmission branch from the second set of transmission branches based on the rearranged rank.
The method as claimed in claim 1, further comprising:
after the step of ranking each of the second set of transmission branches, selecting a transmission branch based on the ranking of the second set of transmission branches.
The method as claimed in claim 1, wherein the step of calculating one or more analog and digital parameters for each of the plurality of transmission branches comprises calculating Thevenin equivalents for each of the plurality of transmission branch.
The method as claimed in claim 1, wherein the analog and digital parameters comprises one or more of voltage, impedance, angle, voltage deviation, impedance deviation, angle deviation, switchgear status.
The method as claimed in claim 1, wherein the threshold is defined by the system operator of the power system or by calculating based on static limits and an available transfer capacity (ATC) using one or more power flow equations.
The method as claimed in claim 1, wherein the one or more objective functions are solved using one or more optimization methods; and
wherein the one or more objective functions comprises:
minimum losses;
minimum generation cost;
minimum angle deviation;
minimum voltage deviation.
The method as claimed in claim 1, wherein the step of checking stability of the power system comprises checking behaviour of the power system over a period of time.
The method as claimed in claim 1, wherein the step of checking stability of the power system comprises checking stability of the plurality of transmission branches and at least one node in the power system, wherein each of transmission branch is connected between at least two nodes.
The method as claimed in claim 1, wherein the stability of the power system comprises at least one of transient stability of the power system, voltage stability, frequency stability and angle stability.
The method as claimed in claim 1, wherein the one or more dynamic constraints of the power system comprises angle, voltage and frequency.
The method as claimed in claim 1, wherein the at least one critical branch is defined by the system operator.
A computing device (105) for selecting a transmission branch from a plurality of transmission branches in a power system (100), the computing device (105) comprises:
a processor (110);
a memory (112) communicatively coupled to the processor (110), wherein the memory (112) stores processor-executable instructions, which, on execution, cause the processor to:
detect at least one overload in the power system;
eliminate at least one radial branch and at least one critical branch from the plurality of transmission branches to obtain a first set of transmission branches;
calculate at least one pair of analog and digital parameters for each of the first set of transmission branches;
compare the calculated at least one pair of analog and digital parameters with one or more thresholds;
filter the plurality of transmissions branches based on the comparison to obtain a second set of transmission branches;
rank each of the second set of transmission branches based on one or more objective functions;
simulate an outage in the power system to rearrange the ranking of each of the second set of transmission branches;
check stability of the power system based on one or more dynamic constraints;
identify one or more weakest transmission branch out of the second set of transmission branches in the power system based on the result of the stability of the power system;
eliminate the one or more identified weakest transmission branch from the second set of transmission branches;
rearrange the rank of the second set of transmission branches after eliminating the one or more identified weakest transmission branch; and
select a transmission branch from the second set of transmission branches based on the rearranged rank.
The computing device as claimed in claim 12, further comprising:
the processor is configured to:
select a transmission branch based on the ranking of the second set of transmission branches after the step of ranking each of the second set of transmission branches.
The computing device as claimed in claim 12, wherein the processor is configured to calculate one or more analog and digital parameters for each of the plurality of transmission branches comprises calculating Thevenin equivalents for each of the plurality of transmission branch.
The computing device as claimed in claim 12, wherein the analog and digital parameters comprises one or more of voltage, impedance, angle, voltage deviation, impedance deviation, angle deviation , switchgear status.
The computing device as claimed in claim 12, wherein the threshold is defined by the system operator of the power system or by calculating based on static limits and an available transfer capacity (ATC) using one or more power flow equations.
The computing device as claimed in claim 12, wherein the one or more objective functions are solved using one or more optimization methods; and
wherein the one or more objective functions comprises:
minimum losses;
minimum generation cost;
minimum angle deviation;
minimum voltage deviation.
The computing device as claimed in claim 12, wherein the processor is configured to check behaviour of the power system over a period of time.
The computing device as claimed in claim 12, wherein the processor is configured to check stability of the plurality of transmission branches and at least one node in the power system, wherein each of transmission branch is connected between at least two nodes.
The computing device as claimed in claim 12, wherein the stability of the power system comprises at least one of transient stability of the power system, voltage stability, frequency stability and angle stability.
The computing device as claimed in claim 12, wherein the one or more dynamic constraints of the power system comprises angle, voltage and frequency.
The computing device as claimed in claim 12, wherein the at least one critical branch is defined by the system operator.