EP2783445A1 - A method for computer-assisted control of an electric power grid - Google Patents

A method for computer-assisted control of an electric power grid

Info

Publication number
EP2783445A1
EP2783445A1 EP12770276.9A EP12770276A EP2783445A1 EP 2783445 A1 EP2783445 A1 EP 2783445A1 EP 12770276 A EP12770276 A EP 12770276A EP 2783445 A1 EP2783445 A1 EP 2783445A1
Authority
EP
European Patent Office
Prior art keywords
case
node
power grid
cases
parameters
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP12770276.9A
Other languages
German (de)
French (fr)
Inventor
Yuriy Sergeevich CHISTYAKOV
Mikhail Aleksandrovich KALINKIN
Vasily Faritovich SHARIPOV
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP2783445A1 publication Critical patent/EP2783445A1/en
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H02J13/00002—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by monitoring
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
    • H02J13/00022—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using wireless data transmission
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1878—Arrangements for adjusting, eliminating or compensating reactive power in networks using tap changing or phase shifting transformers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
    • Y02B70/3225—Demand response systems, e.g. load shedding, peak shaving
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/70—Smart grids as climate change mitigation technology in the energy generation sector
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/22—Flexible AC transmission systems [FACTS] or power factor or reactive power compensating or correcting units
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/30—State monitoring, e.g. fault, temperature monitoring, insulator monitoring, corona discharge
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
    • Y04S20/20—End-user application control systems
    • Y04S20/221—General power management systems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
    • Y04S20/20—End-user application control systems
    • Y04S20/222—Demand response systems, e.g. load shedding, peak shaving
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
    • Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
    • Y04S40/126—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment using wireless data transmission

Definitions

  • the invention refers to a method for computer-assisted control of an electric power grid.
  • the method of the invention provides a computer-assisted control of a distributed electric power grid comprising a plurality of nodes, where each node includes electric equipment for power control.
  • Any well-known node or electric equipment may be controlled by the method of the invention.
  • the electric equipment in at least some of the nodes may refer to a transformer including an onload tap changer and/or to circuit breakers and/or to reactive power compensation equipment and/or to power generation equipment and/or to power consumption equipment.
  • the term "plurality of nodes" may refer to all nodes in the power grid or only to a part of the nodes which are controlled by the inventive method.
  • a central control unit which can communicate with each node determines an overall state of the electric power grid, said overall state referring to the generation and consumption of energy in the power grid.
  • This overall state may be determined by an appropriate classification scheme based on well-known measurements in the power grid. The determination of such an overall state lies within the technical knowledge of a skilled person and, thus, will not be described in detail herein.
  • the central control unit informs each node about a number of basis cases valid for the respective node and for the overall state of the electric power grid.
  • Each basis case comprises a case description including one or more values for a number of parameters of the electric equipment of the respective node and a case solution comprising at least one action which is to be performed by the electric equipment of the respective node if the number of parameters has the value or values according to the case description.
  • the respective node derives at least one action from the current value or values of the number of parameters by case- based reasoning using a case base comprising at least the number of basis cases, where said at least one derived action is performed by the respective node.
  • Case-based reasoning per se is known from the prior art and solves a new problem by remembering the previous similar situation which is derived based on a case base.
  • the case base holds the number of problems in the form of the above defined basis cases, each basis case including a case description and a corresponding case solution. Once a new problem in the form of new values of parameters arises, the solution to this problem is obtained be retrieving similar cases from the case base and studying the similarity between them. Examples of retrieving similar cases by a similarity measure are given in the detailed description.
  • the method according to the invention provides an efficient approach to a local control of the nodes in a power grid on the basis of the overall state of the power grid.
  • the information about basis cases correlated with the overall state of the grid is given to the local nodes by a central control unit. Based on those cases, local case- based reasoning is performed by the nodes.
  • the central control unit may transmit the basis cases to the nodes.
  • the control unit may only give the information to the node which set shall be used according to the overall state of the power grid.
  • the method according to the invention has the advantage that it can be easily implemented in already existing power grids and provides a reliable control of even large power grids by low computational efforts due to the use of local case bases.
  • the distributed case-based reasoning according to the invention has a self-learning ability. To do so, said at least one derived action and the current value or values of the number of parameters are added as derived cases to the case base used for case-based reasoning.
  • the basis cases are adapted when the overall state of the power grid changes.
  • the control unit informs each node about a number of different basis cases valid for the respective node and the changed overall state of the electric power grid.
  • the number of basis cases in the base case used by the respective node for the case-based reasoning is substituted by the number of different basis cases.
  • the case base already includes derived cases, those cases will be discarded from the case base because they are derived for another overall state of the power grid.
  • the number of basis cases is determined by a rule-based expert system in the central control unit. I.e., based on predetermined rules, a set of basis cases can be derived for the overall state of the electric power grid.
  • the rules are defined by experts in order to fulfil particular requirements of the power grid, e.g. the maintenance of power quality in the power grid.
  • the implementation of a rule-based expert system lies within the technical knowledge of a skilled person and, thus, will not be described in detail herein.
  • the case description of the cases valid for at least some of the nodes comprises one or more of the following parameters:
  • said at least one action of the case solution of cases valid for at least some of the nodes is taken out of a number of predetermined switching operations, e.g. a switching operation for an on-load tap changer or a switching operation for a circuit breaker.
  • the number of parameters of the case description for cases valid for the transformer comprises one or more of the following parameters:
  • a switching position of the on-load tap changer said switching position being related to a turns ratio of the transformer
  • said at least one action of the case solution for cases valid for a node with the transformer including the on-load tap changer is preferably taken out of a number of actions comprising the following actions:
  • the invention also refers to an electric power grid comprising a central control unit and a plurality of nodes, each node including electric equipment for power control.
  • the central control unit can communicate with each node and includes means for determining an overall state of the electric power grid, said overall state referring to the generation and consumption of energy in the power grid.
  • the central control unit further includes means for informing each node about a number of basis cases valid for the respective node and the overall state of the electric power grid, each basis case comprising a case description including a value or values for a number of parameters of the electric equipment of the respective node and a case solution comprising at least one action which is to be performed by the electric equipment of the respective node if the number of parameters has the value or values according to the case description.
  • each node includes a case-based reasoning system where, in case of changes of the value or values for the number of parameters of a respective node and/or at predetermined time points during the operation of the power grid, the case- based reasoning system of the respective node derives at least one action from the current value or values of the number of parameters by case-based reasoning using a case base comprising at least the number of basis cases, where said at least one derived action is performed by the respective node.
  • the above described power grid of the invention is preferably adapted to perform one or several preferred embodiments of the method according to the invention.
  • the invention also refers to a central control unit for the above described electric power grid of the invention.
  • This central control unit can communicate with each node and includes means for determining an overall state of the electric power grid, said overall state referring to the generation and consumption of energy in the power grid.
  • the central control unit includes means for informing each node about a number of basis cases valid for the respective node and for the overall state of the electric power grid, each basis case comprising a case description including a value or values for a number of parameters of the electric equipment of the respective node and a case solution comprising at least one action which is to be performed by the electric equipment of the respective node if the number of parameters has the value or values according to the case description.
  • the invention refers to a node for an electric power grid according to the invention.
  • This node includes a case-based reasoning system where, in case of changes of a value or values for a number of parameters of the node and/or at predetermined time points during the operation of the power grid, the case-based reasoning system derives at least one action from the current value or values of the number of parameters by case-based reasoning using a case base comprising at least a number of basis cases which are specified by a central control unit communicating with the node, where said at least one derived action is performed by the node.
  • Fig. 1 shows a schematic illustration of a part of a power grid in which an embodiment of the control method according to the invention is implemented
  • Fig. 2 is a detailed view of the case-based reasoning system included in the nodes of the power grid shown in Fig. 1 ;
  • Fig. 3 shows an example of the structure of cases used for case-based reasoning according to an embodiment of the invention.
  • Fig. 1 which includes nodes Nl , N2, Nn.
  • Each of those nodes includes electric equipment for fulfilling specific tasks in the power grid.
  • the nodes may include transformers for changing the voltage in the grid, circuit breakers which break power transmissions, e.g. in an emergency, a reactive power compensation equipment or any other equipment which is usually implemented in state of the art power grids.
  • the invention will be explained based on nodes forming transformers with a so-called on-load tap changer.
  • On-load tap changers which are also abbreviated as OLTC enable to change of the turns ratio of a transformer during the operation of the transformer.
  • OLTCs are well-known in the art and, thus, will not be described in detail.
  • the power grid as shown in Fig. 1 is controlled by a central control unit CU which can communicate with each of the nodes Nl , N2, Nn as indicated by respective arrows between the control unit and the corresponding nodes.
  • the central control unit CU is based on a rule-based expert system which is used to estimate the overall state of the power grid.
  • This overall state refers to corresponding parameters describing the energy production and energy consumption in the power grid and may depend on several factors. E.g., in case that renewable energies are used in the power grid, the overall state depends on weather conditions. Furthermore, the overall state usually depends on the daytime. E.g., during night time energy consumption for households is less than during the day.
  • the rule-based expert system categorizes the power grid according to the energy consumption and energy distribution into a certain state class. Based on the corresponding class, a number of so-called basis cases for each of the nodes are defined according to predetermined rules.
  • the basis cases include actions to be performed by the corresponding nodes in response to certain values assumed by corresponding parameters of the nodes as will be described in more detail later on.
  • the rules in the rule-based expert system are such that a desired operation of the power grid with respect to certain criteria is achieved. In a particularly preferred embodiment, the rules are such that the actions performed based on the values of the parameters in the respective nodes lead to a maintenance of the power quality in the network, e.g. by preventive load shedding and/or reserve generation switching.
  • the number of basis cases valid for each of the nodes Nl to Nn is transmitted to the corresponding nodes based on the detected overall regime of the power grid.
  • Those basis cases are stored in case-based reasoning systems implemented in each node.
  • node Nl includes the case- based reasoning system CBR1
  • node N2 includes the case-based reasoning system CBR2
  • node Nn includes the case-based reasoning system CBRn.
  • a distributed case-based reasoning system is formed in the power grid by decentralized case-based reasoning systems CBR1 to CBRn.
  • the case base used in the corresponding reasoning systems depends on the overall state of the power network which is estimated by the central control unit CU.
  • the basis cases will also be changed with the consequence that the central control unit will provide changed basis cases to each case-based reasoning system.
  • the changed basis cases substitute the basis cases currently in use.
  • the basis cases are defined by the control unit using expert knowledge coded in a rule-based expert system.
  • each of the nodes Nl to Nn monitors the corresponding parameters in its case base and performs well-known case-based reasoning using the current values of the parameters.
  • Fig. 2 illustrates the case-based reasoning CBR system used by each node.
  • the system includes a number of basis cases BC depending on the overall state of the power grid.
  • new cases are derived during the process of case-based reasoning. This is indicated by the arrow P in Fig. 2 which leads to corresponding derived cases DC.
  • the derived cases DC are added to the case base and, thus, increase the number of cases in case base used for case-based reasoning.
  • the number of basis cases will also change so that the derived cases are no longer applicable for the new set of basis cases.
  • the old derived cases are discarded from the case base.
  • Fig. 3 indicates the structure of a case CA in such a node.
  • This case can refer to a basis case BC as well as to a derived case DC.
  • the case CA includes a case description CD as well as a case solution CS.
  • the case description comprises a number of parameters.
  • those parameters usually comprise an output voltage VO, a current CR, the position PO of the on-load tap changer (i.e. the turns ratio of the transformer) and the time TI from the last OLTC switching.
  • Other parameters may also be included in the case description CD depending on the circumstances.
  • the case CA includes a case solution CS which is represented by at least on action A which refers to the action "switch” or “not switch” as well as to the new position of the on-load tap changer in case that a switching operation is to be performed by the on-load tap changer.
  • action A as specified in the case solution CS is taken by the transformer in case that the parameters in the case description CD assume the values specified in the case description.
  • Case-based reasoning will be performed by each node in case of a new situation, i.e. a change in its current parameter values monitored by the node.
  • the new parameter values which form a vector will be compared to the vectors of the parameter values in the case descriptions of the cases in the case base. This is done in order to find those cases in the case base which are nearest (i.e. most similar) to the vector of the current parameter values.
  • Well-known prior art methods can be applied for identifying the nearest cases. Particularly, the nearest neighbour approach can be used where only the nearest case is considered.
  • the solution of this case is directly reused as the solution for the current values of the parameters.
  • the action according to this case solution is then performed by the respective node.
  • the current values of the parameters of this solution form a new derived case DC stored as a new case in the case base.
  • Another approach for identifying nearest cases is majority voting. In this approach, a small (normally three or five) number of nearest cases is considered and a vote is organized among them. E.g., if three nearest cases are considered and two of them have solution "a" and the third case has solution "b", then solution "a" wins and, therefore, the action according to this solution is performed by the node. Furthermore, the current values of the parameters and this solution forms a new derived case added to the case base.
  • Another approach for identifying a nearest case is weighted majority voting which is similar to majority voting but takes into account distances to nearest neighbour cases.
  • a similarity function is to be used which is preferably based on the Euclidian distance between the parameter vectors of the current values of the parameters and the vector of the case descriptions in the case base.
  • the distance between Casel and Case2 according to the Euclidian distance can be defined as follows:
  • dist(Case ⁇ ,Case2) J(V - V 2 ) 2 + ( , - i 2 + ( ⁇ - ⁇ 2 f + ( ⁇ ] - ⁇ 2 ) 2 + (pos ] - pos 2 ) 2 (1)
  • , V 2 are output voltages for Casel and Case2 correspondingly;
  • ii, i 2 are output currents for Casel and Case2 correspondingly;
  • ⁇ , ⁇ 2 are phase shifts for Casel and Case2 correspondingly;
  • posi, pos 2 are current positions of tap changers for Casel and Case2 correspondingly.
  • x n0 rmaii d is the normalized value of the parameter
  • x is the initial value of parameter
  • ⁇ is the mean value of x among all cases in the case base
  • ⁇ is the standard deviation of x among all cases in the case base.
  • the invention provides a mechanism for distributed case-based reasoning where the cases in the case base represent different regimes of the power grid and are defined by offline calculation with the help of a rule- based expert system.
  • the cases are changed by the supervising rule-based expert system when some changes in the power grid occur.
  • new cases are derived which are added to the case base of the existing basis cases. If the basis cases are changed by the central rule-based expert system, the derived cases become unvalid and are removed from the case-based reasoning system.
  • the invention as described above has several advantages. Particularly, in comparison to local expert systems installed in each node of the power grid, the reliability of the power grid is increased. This is because global information about the overall state of the grid is available. This global information is very important for a save and reliable operation of the corresponding electric equipment in the nodes and particularly for an OLTC mechanism of a transformer. In comparison to an approach where one global expert system monitors all nodes in the grid, low computational efforts are needed for the method of the invention due to the relative small sizes of local case bases. Furthermore, due to the derivation of new cases, the system includes a self-learning ability. Moreover, the maintenance of the distributed case-based reasoning system is very simple in comparison to a single central case-based reasoning system with a large case base. Furthermore, the distributed case-based system can be easily integrated in an existing infrastructure of a power grid. List of references

Abstract

The invention refers to a method for computer-assisted control of an electric power grid comprising a plurality of nodes (N1, N2,, Nn), each node (N1, N2,, Nn) including electric equipment for power control. In this method, decentralized case-based reasoning is implemented in each node where the number of cases (BC) used for the case-based reasoning is specified by a central control unit (CU) communicating with each node. The central control unit estimates the overall state of the power grid and determines the number of cases to be used in each node in dependence from this overall state. During the operation of the power grid, case-based reasoning is performed in each node by comparing current parameters of the electric equipment in the node with the cases in a case base comprising the number of cases specified by the central control unit. In a preferred embodiment, the invention is used for nodes including transformers with an on-load tap changer where the switching of the tap changer is determined by case-based reasoning. The invention provides an easy and reliable control of decentralized power grids and an easy implementation of the method in existing grid structures. Fig.1

Description

A METHOD FOR COMPUTER-ASSISTED CONTROL
OF AN ELECTRIC POWER GRID
The invention refers to a method for computer-assisted control of an electric power grid.
Due to the increasing decentralization of power generation, the control of power grids is becoming more complex. Local control of electric equipment in corresponding nodes in the power grid is in many cases not sufficient and may lead to power outages. E.g., switching operations of transformers with an on-load tap changer can be problematic. This is because the mechanism of an on-load tap changer is designed to keep the voltage of consumers close to the optimum by increasing and decreasing the transformation coefficient of the transformer even if the load changes significantly. This can lead to a voltage collapse.
In document [1], a mechanism of case-based reasoning for a distributed voltage control in a power grid is described. To do so, a central case-based reasoning expert system is used for active voltage control using available control mechanisms in the distributed power grid, like on-load tap changers, breakers, local generators and so on. This control system will be hard to maintain for a big distributed power grid.
Hence, it is an object of the invention to provide an easy and reliable control mechanism for a distributed power grid.
This object is solved by the independent claims. Preferred embodiments are defined in the dependent claims.
The method of the invention provides a computer-assisted control of a distributed electric power grid comprising a plurality of nodes, where each node includes electric equipment for power control. Any well-known node or electric equipment may be controlled by the method of the invention. Particularly, the electric equipment in at least some of the nodes may refer to a transformer including an onload tap changer and/or to circuit breakers and/or to reactive power compensation equipment and/or to power generation equipment and/or to power consumption equipment. The term "plurality of nodes" may refer to all nodes in the power grid or only to a part of the nodes which are controlled by the inventive method.
According to the invention, a central control unit which can communicate with each node determines an overall state of the electric power grid, said overall state referring to the generation and consumption of energy in the power grid. This overall state may be determined by an appropriate classification scheme based on well-known measurements in the power grid. The determination of such an overall state lies within the technical knowledge of a skilled person and, thus, will not be described in detail herein.
The central control unit informs each node about a number of basis cases valid for the respective node and for the overall state of the electric power grid. Each basis case comprises a case description including one or more values for a number of parameters of the electric equipment of the respective node and a case solution comprising at least one action which is to be performed by the electric equipment of the respective node if the number of parameters has the value or values according to the case description.
In case of changes of the value or values for the number of parameters of a respective node and/or at predetermined time points, the respective node derives at least one action from the current value or values of the number of parameters by case- based reasoning using a case base comprising at least the number of basis cases, where said at least one derived action is performed by the respective node. Case-based reasoning per se is known from the prior art and solves a new problem by remembering the previous similar situation which is derived based on a case base. The case base holds the number of problems in the form of the above defined basis cases, each basis case including a case description and a corresponding case solution. Once a new problem in the form of new values of parameters arises, the solution to this problem is obtained be retrieving similar cases from the case base and studying the similarity between them. Examples of retrieving similar cases by a similarity measure are given in the detailed description.
The method according to the invention provides an efficient approach to a local control of the nodes in a power grid on the basis of the overall state of the power grid. To do so, the information about basis cases correlated with the overall state of the grid is given to the local nodes by a central control unit. Based on those cases, local case- based reasoning is performed by the nodes. In order to inform the nodes about the number of basis cases to be used, the central control unit may transmit the basis cases to the nodes. However, it is also possible that several sets of different basis cases are already stored in the nodes and the control unit only gives the information to the node which set shall be used according to the overall state of the power grid.
The method according to the invention has the advantage that it can be easily implemented in already existing power grids and provides a reliable control of even large power grids by low computational efforts due to the use of local case bases.
In a preferred embodiment, the distributed case-based reasoning according to the invention has a self-learning ability. To do so, said at least one derived action and the current value or values of the number of parameters are added as derived cases to the case base used for case-based reasoning.
In another embodiment of the invention, the basis cases are adapted when the overall state of the power grid changes. To do so, in case that the central control unit determines a change in the overall state of the power grid, the control unit informs each node about a number of different basis cases valid for the respective node and the changed overall state of the electric power grid. As a consequence, the number of basis cases in the base case used by the respective node for the case-based reasoning is substituted by the number of different basis cases. In case that the case base already includes derived cases, those cases will be discarded from the case base because they are derived for another overall state of the power grid.
In another preferred embodiment of the invention, the number of basis cases is determined by a rule-based expert system in the central control unit. I.e., based on predetermined rules, a set of basis cases can be derived for the overall state of the electric power grid. The rules are defined by experts in order to fulfil particular requirements of the power grid, e.g. the maintenance of power quality in the power grid. The implementation of a rule-based expert system lies within the technical knowledge of a skilled person and, thus, will not be described in detail herein.
In a particularly preferred embodiment, the case description of the cases valid for at least some of the nodes comprises one or more of the following parameters:
one or more voltages occurring in or produced by the electric equipment of the node;
- one or more electric currents occurring in or produced by the electric equipment of the node;
one or more phases and/or phase shifts of electric voltage and/or current occurring in or produced by the electric equipment of the node;
one or more power generation or power consumption parameters of the electric equipment of the node.
In another embodiment of the invention, said at least one action of the case solution of cases valid for at least some of the nodes is taken out of a number of predetermined switching operations, e.g. a switching operation for an on-load tap changer or a switching operation for a circuit breaker.
In another embodiment of the invention in which the electric equipment of at least some of the nodes refers to a transformer including an on-load tap changer, the number of parameters of the case description for cases valid for the transformer comprises one or more of the following parameters:
an output voltage of the transformer;
an output current of the transformer;
a switching position of the on-load tap changer, said switching position being related to a turns ratio of the transformer;
the time from the last change of the switching position of the on-load tap changer.
Furthermore, said at least one action of the case solution for cases valid for a node with the transformer including the on-load tap changer is preferably taken out of a number of actions comprising the following actions:
changing the switching position of the on-load tap changer in a new predetermined position, where for each possible new predetermined position a corresponding action is defined;
not changing the switching position of the on-load tap changer.
Besides the above method, the invention also refers to an electric power grid comprising a central control unit and a plurality of nodes, each node including electric equipment for power control. In this power grid, the central control unit can communicate with each node and includes means for determining an overall state of the electric power grid, said overall state referring to the generation and consumption of energy in the power grid. The central control unit further includes means for informing each node about a number of basis cases valid for the respective node and the overall state of the electric power grid, each basis case comprising a case description including a value or values for a number of parameters of the electric equipment of the respective node and a case solution comprising at least one action which is to be performed by the electric equipment of the respective node if the number of parameters has the value or values according to the case description.
Furthermore, each node includes a case-based reasoning system where, in case of changes of the value or values for the number of parameters of a respective node and/or at predetermined time points during the operation of the power grid, the case- based reasoning system of the respective node derives at least one action from the current value or values of the number of parameters by case-based reasoning using a case base comprising at least the number of basis cases, where said at least one derived action is performed by the respective node.
The above described power grid of the invention is preferably adapted to perform one or several preferred embodiments of the method according to the invention.
The invention also refers to a central control unit for the above described electric power grid of the invention. This central control unit can communicate with each node and includes means for determining an overall state of the electric power grid, said overall state referring to the generation and consumption of energy in the power grid. Furthermore, the central control unit includes means for informing each node about a number of basis cases valid for the respective node and for the overall state of the electric power grid, each basis case comprising a case description including a value or values for a number of parameters of the electric equipment of the respective node and a case solution comprising at least one action which is to be performed by the electric equipment of the respective node if the number of parameters has the value or values according to the case description.
Moreover, the invention refers to a node for an electric power grid according to the invention. This node includes a case-based reasoning system where, in case of changes of a value or values for a number of parameters of the node and/or at predetermined time points during the operation of the power grid, the case-based reasoning system derives at least one action from the current value or values of the number of parameters by case-based reasoning using a case base comprising at least a number of basis cases which are specified by a central control unit communicating with the node, where said at least one derived action is performed by the node.
Embodiments of the invention will now be described with respect to the accompanying drawings wherein:
Fig. 1 shows a schematic illustration of a part of a power grid in which an embodiment of the control method according to the invention is implemented;
Fig. 2 is a detailed view of the case-based reasoning system included in the nodes of the power grid shown in Fig. 1 ; and
Fig. 3 shows an example of the structure of cases used for case-based reasoning according to an embodiment of the invention.
In the following, an embodiment of the invention will be described based on a power grid as shown in Fig. 1 which includes nodes Nl , N2, Nn. Each of those nodes includes electric equipment for fulfilling specific tasks in the power grid. E.g., the nodes may include transformers for changing the voltage in the grid, circuit breakers which break power transmissions, e.g. in an emergency, a reactive power compensation equipment or any other equipment which is usually implemented in state of the art power grids. Hereinafter, the invention will be explained based on nodes forming transformers with a so-called on-load tap changer. On-load tap changers which are also abbreviated as OLTC enable to change of the turns ratio of a transformer during the operation of the transformer. OLTCs are well-known in the art and, thus, will not be described in detail.
The power grid as shown in Fig. 1 is controlled by a central control unit CU which can communicate with each of the nodes Nl , N2, Nn as indicated by respective arrows between the control unit and the corresponding nodes. In the embodiment as described herein, the central control unit CU is based on a rule-based expert system which is used to estimate the overall state of the power grid. This overall state refers to corresponding parameters describing the energy production and energy consumption in the power grid and may depend on several factors. E.g., in case that renewable energies are used in the power grid, the overall state depends on weather conditions. Furthermore, the overall state usually depends on the daytime. E.g., during night time energy consumption for households is less than during the day.
The rule-based expert system categorizes the power grid according to the energy consumption and energy distribution into a certain state class. Based on the corresponding class, a number of so-called basis cases for each of the nodes are defined according to predetermined rules. The basis cases include actions to be performed by the corresponding nodes in response to certain values assumed by corresponding parameters of the nodes as will be described in more detail later on. The rules in the rule-based expert system are such that a desired operation of the power grid with respect to certain criteria is achieved. In a particularly preferred embodiment, the rules are such that the actions performed based on the values of the parameters in the respective nodes lead to a maintenance of the power quality in the network, e.g. by preventive load shedding and/or reserve generation switching. The estimation of the overall state or regime of a power grid by a central control unit as well as the definition of predetermined rules for defining a corresponding number of basis cases for respective nodes lies within the technical knowledge of a skilled person and, thus, will not be described in detail herein.
In the power grid as shown in Fig. 1 , the number of basis cases valid for each of the nodes Nl to Nn is transmitted to the corresponding nodes based on the detected overall regime of the power grid. Those basis cases are stored in case-based reasoning systems implemented in each node. As shown in Fig. 1 , node Nl includes the case- based reasoning system CBR1 , node N2 includes the case-based reasoning system CBR2 and node Nn includes the case-based reasoning system CBRn. Hence, a distributed case-based reasoning system is formed in the power grid by decentralized case-based reasoning systems CBR1 to CBRn. The case base used in the corresponding reasoning systems depends on the overall state of the power network which is estimated by the central control unit CU. Hence, in case that the central control unit CU detects a change in the overall state of the power grid, the basis cases will also be changed with the consequence that the central control unit will provide changed basis cases to each case-based reasoning system. The changed basis cases substitute the basis cases currently in use. As mentioned before, the basis cases are defined by the control unit using expert knowledge coded in a rule-based expert system. During operation of the power grid in a fixed overall state determined by the control unit, each of the nodes Nl to Nn monitors the corresponding parameters in its case base and performs well-known case-based reasoning using the current values of the parameters. Fig. 2 illustrates the case-based reasoning CBR system used by each node. As mentioned above, the system includes a number of basis cases BC depending on the overall state of the power grid. In the embodiment as described herein, new cases are derived during the process of case-based reasoning. This is indicated by the arrow P in Fig. 2 which leads to corresponding derived cases DC. The derivation of those cases will be described in more detail later on. In the embodiment of Fig. 2, the derived cases DC are added to the case base and, thus, increase the number of cases in case base used for case-based reasoning. However, in case that the overall state of the power grid changes, the number of basis cases will also change so that the derived cases are no longer applicable for the new set of basis cases. Hence, in case that a new number of basis cases apply, the old derived cases are discarded from the case base.
In the following, the process of case-based reasoning with respect to cases for a node representing a transformer with an on-load tap changer is described in more detail. Fig. 3 indicates the structure of a case CA in such a node. This case can refer to a basis case BC as well as to a derived case DC. The case CA includes a case description CD as well as a case solution CS. The case description comprises a number of parameters. For a transformer including an on-load tap changer those parameters usually comprise an output voltage VO, a current CR, the position PO of the on-load tap changer (i.e. the turns ratio of the transformer) and the time TI from the last OLTC switching. Other parameters may also be included in the case description CD depending on the circumstances. Those parameters may comprise voltage or current phases, voltage or current phase jumps, the active power and so on. The case description CD including the number of parameters is characterized by corresponding values of the parameters which are not indicated in Fig. 3. Furthermore, the case CA includes a case solution CS which is represented by at least on action A which refers to the action "switch" or "not switch" as well as to the new position of the on-load tap changer in case that a switching operation is to be performed by the on-load tap changer. The action A as specified in the case solution CS is taken by the transformer in case that the parameters in the case description CD assume the values specified in the case description.
Case-based reasoning will be performed by each node in case of a new situation, i.e. a change in its current parameter values monitored by the node. To do so, the new parameter values which form a vector will be compared to the vectors of the parameter values in the case descriptions of the cases in the case base. This is done in order to find those cases in the case base which are nearest (i.e. most similar) to the vector of the current parameter values. Well-known prior art methods can be applied for identifying the nearest cases. Particularly, the nearest neighbour approach can be used where only the nearest case is considered. The solution of this case is directly reused as the solution for the current values of the parameters. The action according to this case solution is then performed by the respective node. Furthermore, the current values of the parameters of this solution form a new derived case DC stored as a new case in the case base. Another approach for identifying nearest cases is majority voting. In this approach, a small (normally three or five) number of nearest cases is considered and a vote is organized among them. E.g., if three nearest cases are considered and two of them have solution "a" and the third case has solution "b", then solution "a" wins and, therefore, the action according to this solution is performed by the node. Furthermore, the current values of the parameters and this solution forms a new derived case added to the case base. Another approach for identifying a nearest case is weighted majority voting which is similar to majority voting but takes into account distances to nearest neighbour cases.
For specifying the nearest cases, a similarity function is to be used which is preferably based on the Euclidian distance between the parameter vectors of the current values of the parameters and the vector of the case descriptions in the case base. E.g., the distance between Casel and Case2 according to the Euclidian distance can be defined as follows:
dist(Case\,Case2) = J(V - V2 )2 + ( , - i2 + (φ - φ2 f + (Αφ] - Δφ2 )2 + (pos] - pos2 )2 (1)
where
V|, V2 are output voltages for Casel and Case2 correspondingly;
ii, i2 are output currents for Casel and Case2 correspondingly;
(pi, φ2 are phases for Casel and Case2 correspondingly;
Δφι, Δφ2 are phase shifts for Casel and Case2 correspondingly;
posi, pos2 are current positions of tap changers for Casel and Case2 correspondingly. In a preferred embodiment, before the calculation of the distances according to formula (1 ), the values of the parameters are normalized to the standard deviation as follows: x normalized = ^ ( V2)
σ
where xn0rmaii: d is the normalized value of the parameter, x is the initial value of parameter, μ is the mean value of x among all cases in the case base and σ is the standard deviation of x among all cases in the case base.
As described in the foregoing, the invention provides a mechanism for distributed case-based reasoning where the cases in the case base represent different regimes of the power grid and are defined by offline calculation with the help of a rule- based expert system. The cases are changed by the supervising rule-based expert system when some changes in the power grid occur. During the operation of the local case-based reasoning systems in the nodes of the grid, new cases are derived which are added to the case base of the existing basis cases. If the basis cases are changed by the central rule-based expert system, the derived cases become unvalid and are removed from the case-based reasoning system.
The invention as described above has several advantages. Particularly, in comparison to local expert systems installed in each node of the power grid, the reliability of the power grid is increased. This is because global information about the overall state of the grid is available. This global information is very important for a save and reliable operation of the corresponding electric equipment in the nodes and particularly for an OLTC mechanism of a transformer. In comparison to an approach where one global expert system monitors all nodes in the grid, low computational efforts are needed for the method of the invention due to the relative small sizes of local case bases. Furthermore, due to the derivation of new cases, the system includes a self-learning ability. Moreover, the maintenance of the distributed case-based reasoning system is very simple in comparison to a single central case-based reasoning system with a large case base. Furthermore, the distributed case-based system can be easily integrated in an existing infrastructure of a power grid. List of references
[1] T. Xu, P. Taylor, M. Prodanovic, T. Green, E. Davidson, S. McArthur, Case based reasoning for distributed voltage control, 20th international conference on electricity distribution, Prague, 8-11 June 2009.

Claims

Patent Claims
1. A method for computer-assisted control of an electric power grid comprising a plurality of nodes (Nl, N2, Nn), each node (Nl , N2, Nn) including electric equipment for power control, wherein
- a central control unit (CU) which can communicate with each node (Nl ,
N2, Nn) determines an overall state of the electric power grid, said overall state referring to the generation and consumption of energy in the power grid;
the central control unit (CU) informs each node (Nl , N2, Nn) about a number of basis cases (BC) valid for the respective node (Nl , N2, Nn) and the overall state of the electric power grid, each basis case (BC) comprising a case description (CD) including one or more values for a number of parameters (VO, CR, PO, TI) of the electric equipment of the respective node (Nl , N2, Nn) and a case solution (CS) comprising at least one action (A) which is to be performed by the electric equipment of the respective node (Nl , N2, Nn) if the number of parameters (VO, CR, PO, TI) has the value or values according to the case description (CD);
in case of changes of the value or values for the number of parameters (VO, CR, PO, TI) of a respective node (Nl , N2, Nn) and/or at predetermined time points during the operation of the power grid, the respective node (Nl , N2, Nn) derives at least one action (A) from the current value or values of the number of parameters (VO, CR, PO, TI) by case-based reasoning using a case base comprising at least the number of basis cases (BC), where said at least one derived action (A) is performed by the respective node (N 1 , N2, ..., Nn).
2. The method according to claim 1 , wherein said at least one derived action (A) and the current value or values of the number of parameters (VO, CR, PO, TI) are added as derived cases (DC) to the case base used for case-based reasoning.
3. The method according to claim 1 or 2, wherein, in case that the central control unit (CU) determines a change in the overall state of the power grid, the central control unit (CU) informs each node (Nl , N2, Nn) about a number of different basis cases (BC) valid for the respective node (Nl , N2, Nn) and the changed overall state of the electric power grid, whereupon the number of basis cases (BC) in the case base being used by the respective node (Nl , N2, Nn) for the case-based reasoning is substituted by the number of different basis cases (BC).
4. The method according to claim 2 and 3, wherein the derived cases (DC) determined for another overall state than the changed overall state are discarded from the case base.
5. The method according to one of the preceding claims, wherein the number of basis cases (BC) is determined by a rule-based expert system in the central control unit
(CU).
6. The method according to one of the preceding claims, wherein the case description (CD) of cases valid for at least some of the nodes (Nl , N2, Nn) comprises one or more of the following parameters:
- one or more voltages occurring in or produced by the electric equipment of the node (Nl, N2, ..., Nn);
one or more electric currents occurring in or produced by the electric equipment of the node (Nl , N2, ..., Nn);
one or more phases and/or phase shifts of electric voltage and/or current occurring in or produced by the electric equipment of the node (Nl , N2, ..., Nn);
one or more power generation or power consumption parameters of the electric equipment of the node (N 1 , N2, ... , Nn).
7. The method according to one of the preceding claims, wherein said at least one action (A) of the case solution (CS) of cases valid for at least some of the nodes (N 1 , N2, ... , Nn) is taken out of a number of predetermined switching operations.
8. The method according to one of the preceding claims, wherein the electric equipment of at least some of the nodes (Nl , N2, Nn) refers to a transformer including an on-load tap changer.
9. The method according to claim 8, wherein the number of parameters (VO, CR, PO, TI) of the case description for cases valid for a node (Nl , N2, Nn) with the transformer including the on-load tap changer comprises one or more of the following parameters:
an output voltage (VO) of the transformer;
an output current (CR) of the transformer;
- a switching position (PO) of the on-load tap changer, said switching position (PO) being related to a turns ratio of the transformer;
the time (TI) from the last change of the switching position (PO) of the on-load tap changer.
10. The method according to claim 8 or 9, wherein said at least one action (A) of the case solution (CS) for cases valid for a node (Nl , N2, Nn) with the transformer including the on-load tap changer is taken out of a number of actions comprising the following actions (A):
changing the switching position (PO) of the on-load tap changer in a new predetermined position;
not changing the switching position (PO) of the on-load tap changer.
11. The method according to one of the preceding claims, wherein the electric equipment of at least some of the nodes (Nl , N2, Nn) refers to a circuit breaker and/or to a reactive power compensation equipment and/or power generation equipment and/or power consumption equipment.
12. An electric power grid comprising a central control unit (CU) and a plurality of nodes (Nl , N2, Nn), each node (Nl , N2, Nn) including electric equipment for power control, wherein
the central control unit (CU) can communicate which each node (Nl , N2, Nn) and includes means for determining an overall state of the electric power grid, said overall state referring to the generation and consumption of energy in the power grid;
- the central control unit (CU) includes means for informing each node
(Nl , N2, Nn) about a number of basis cases (BC) valid for the respective node (Nl , N2, Nn) and the overall state of the electric power grid, each basis case (BC) comprising a case description (CD) including value or values for a number of parameters (VO, CR, PO, TI) of the electric equipment of the respective node (Nl , N2, ..., Nn) and a case solution comprising at least one action (A) which is to be performed by the electric equipment of the respective node (Nl, N2, Nn) if the number of parameters (VO, CR, PO, TI) has the value or values according to the case description (CD);
each node (Nl , N2, Nn) includes a case-based reasoning system (CBR1 , CBR2, CBRn) where, in case of changes of the value or values for the number of parameters (VO, CR, PO, TI) of a respective node (Nl , N2, Nn) and/or at predetermined time points during the operation of the power grid, the case-based reasoning system (CBR1 , CBR2, CBRn) of the respective node (Nl , N2, Nn) derives at least one action (A) from the current value or values of the number of parameters (VO, CR, PO, TI) by case-based reasoning using a case base comprising at least the number of basis cases (BC), where said at least one derived action (A) is performed by the respective node (N 1 , N2, ... , Nn).
13. The power grid according to claim 12, wherein the power grid is adapted to perform a method according to one of the claims 2 to 11.
14. A central control unit for an electric power grid according to claim 12 or 13, wherein
- the central control unit (CU) can communicate which each node (Nl ,
N2, Nn) and includes means for determining an overall state of the electric power grid, said overall state referring to the generation and consumption of electric energy in the power grid;
the central control unit (CU) includes means for informing each node (N 1 , N2, ... , Nn) about a number of basis cases (BC) valid for the respective node ( 1 , N2, Nn) and the overall state of the electric power grid, each basis case (BC) comprising a case description (CD) including value or values for a number of parameters (VO, CR, PO, TI) of the electric equipment of the respective node (Nl , N2, ..., Nn) and a case solution comprising at least one action (A) which is to be performed by the electric equipment of the respective node if the number of parameters (VO, CR, PO, TI) has the value or values according to the case description (CD).
15. A node for an electric power grid according to claim 12 or 13, where said node (Nl , N2, Nn) includes a case-based reasoning system (CBR1 , CBR2, CBRn) where, in case of changes of a value or values for a number of parameters (VO, CR, PO, TI) of the node (Nl , N2, Nn) and/or at predetermined time points during the operation of the power grid, the case-based reasoning system (CBR1 , CBR2, CBRn) derives at least one action (A) from the current value or values of the number of parameters (VO, CR, PO, TI) by case-based reasoning using a case base comprising at least a number of basis cases which are specified by a central control unit (CU) communicating with the node (Nl , N2, Nn), where said at least one derived action (A) is performed by the node (Nl , N2, ..., Nn).
EP12770276.9A 2012-03-01 2012-03-01 A method for computer-assisted control of an electric power grid Ceased EP2783445A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/RU2012/000149 WO2013129958A1 (en) 2012-03-01 2012-03-01 A method for computer-assisted control of an electric power grid

Publications (1)

Publication Number Publication Date
EP2783445A1 true EP2783445A1 (en) 2014-10-01

Family

ID=47010687

Family Applications (1)

Application Number Title Priority Date Filing Date
EP12770276.9A Ceased EP2783445A1 (en) 2012-03-01 2012-03-01 A method for computer-assisted control of an electric power grid

Country Status (2)

Country Link
EP (1) EP2783445A1 (en)
WO (1) WO2013129958A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102013202005A1 (en) * 2013-02-07 2014-08-07 Siemens Aktiengesellschaft Method and device for operating a power grid
DE102015005252A1 (en) * 2015-04-24 2016-10-27 Senvion Gmbh Control system for a wind turbine or a wind farm and control method

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2410386A (en) * 2004-01-22 2005-07-27 Areva T & D Uk Ltd Controlling reactive power output
EP1880459B2 (en) * 2005-05-13 2022-02-09 Siemens Gamesa Renewable Energy A/S Wind farm power control system

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
None *
See also references of WO2013129958A1 *

Also Published As

Publication number Publication date
WO2013129958A1 (en) 2013-09-06

Similar Documents

Publication Publication Date Title
Han et al. Distributed nonlinear control with event-triggered communication to achieve current-sharing and voltage regulation in DC microgrids
Islam et al. Coordinated decentralized emergency voltage and reactive power control to prevent long-term voltage instability in a power system
EP2506384B1 (en) System and method for operating a tap changer
US9887545B2 (en) Controlling an electrical energy distribution network
EP2688191A1 (en) Multi terminal HVDC control
Adewole et al. Adaptive under‐voltage load shedding scheme for large interconnected smart grids based on wide area synchrophasor measurements
WO2000077908A1 (en) An application and method for voltage instability predictor (vip)
Islam et al. A decentralized multiagent-based voltage control for catastrophic disturbances in a power system
US7277779B2 (en) Real-time emergency control in power systems
Hussain et al. A hybrid framework for adaptive protection of microgrids based on IEC 61850
CN107257133B (en) Reactive power optimization method and device and AVC system
JP6356517B2 (en) System monitoring and control device
US8817444B2 (en) Control arrangement
WO2013129958A1 (en) A method for computer-assisted control of an electric power grid
Genêt et al. Voltage-stability monitoring using wide-area measurement systems
Skok et al. System integrity protection schems for future power transmission system using synchrophasors
Shukla et al. A hierarchical decentralized coordinated voltage instability detection scheme for SVC
Skok et al. Monitoring and control of smart transmission grid based on synchronized measurements
Zoka et al. An optimal decentralized control for voltage control devices by means of a multi-agent system
Corsi Wide area voltage regulation & protection
Corsi Wide area voltage regulation in Italy and related wide area protection
Gajić et al. Using IEC 61850 analogue goose messages for OLTC control of parallel transformers
JP6848234B2 (en) Voltage monitoring and control device
Prabhu et al. Automatic tap changing in transformers for power quality enhancement in a smart grid distribution system
US11146102B2 (en) Method and control center arrangement for the control of an electrical energy transmission grid, and computer program product

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20140624

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

DAX Request for extension of the european patent (deleted)
17Q First examination report despatched

Effective date: 20160927

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: SIEMENS AKTIENGESELLSCHAFT

REG Reference to a national code

Ref country code: DE

Ref legal event code: R003

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED

18R Application refused

Effective date: 20190628