Abb Research Ltd.

Abb Schweiz Ag

Abb Technology Ag

Abb Power Grids Switzerland Ag

Christian Rehtanz

Joachim Bertsch

Marek Zima

Mats Larsson

Dirk Westermann

Petr Korba

Martin Naedele

Valentin Bürgler

Andreas Suranyi

Peter Bosshart

Christian Pinzon

The present disclosure is concerned with the reduction of an operational security margin of a power system without jeopardizing the safety of the power system or incurring heavy investments. According to the disclosure, a check for basic accuracy or correctness of a conventional State Estimation (SE) procedure allows to increase a level of confidence in the results of the procedure. To this end, an accuracy of the estimated states is verified by comparing the latter with the results (y, y') of independent phasor measurements performed at selected locations of the power system. Unless a discrepancy is reported by this comparison, the results of the SE can be assumed to be sufficiently accurate, and any conservative or additional security margin intended to compensate for SE uncertainty can be relaxed. Hence, established trustworthiness in the estimated states allows increasing the transmitted power where the estimated states do indicate such a possibility, i.e. in particular in fringe areas and/or transmission corridors between countries, and especially under stressed network conditions.

Verifying an accuracy of a state estimation

The invention is directed toward an electrical power control system () in an electrical power system, having: a power control unit () for setting electric state variables and/or parameters in a current conductor, to be controlled, of the electrical power system, having: means () for detecting electric characteristic values () of the current conductor; a function processor for applying a control function (F()) from a mathematical set of control functions to the electric characteristic values, and for determining controlled variables (y) for achieving the parameters; and coordination means for determining a control function (F(u)) from the set of control functions with the aid of operating states of the electrical power system. This system renders it possible to achieve a predictive tuned control of the electrical power control system which can also stabilize unusual operating states of the electrical power system.

Electrical power control system, and method for setting electric state variables and/or parameters in a current conductor

A method for determining an equivalent impedance of a transmission section of an electrical network, includes representing the transmission section as having at least two interfaces with other sections of the network. For each interface, a voltage phasor and a current phasor flowing through the interface are determined from simultaneously made measurements at the interfaces. From the phasors, the equivalent impedance is calculated. The required simultaneousness of the phasor measurements is achieved by means of Phasor Measurement Units (PMUs) that are synchronized via the Global Positioning System (GPS).

Determining parameters of an equivalent circuit representing a transmission section of an electrical network

The detection of electromechanical oscillations in power systems and the estimation of their frequency and damping parameters are based on a linear time-varying model. The parameters of the linear model are on-line adapted by means of Kalman filtering techniques to optimally approximate the measured signal representing the behavior of the power system based on a quadratic criterion. The estimated model parameters are then the basis for the calculation of parameters of the oscillations. Adaptive algorithms are based on a recursive calculation of the estimated parameter vector for each time-step based on the new value of the measured signal and the old values of the estimated parameters.

Detecting electromechanical oscillations in power systems

In a method, computer program and system for determining an operational limit of a power transmission line, time-stamped current phasor information and voltage phasor information for a first end and a second end of the line are determined, an ohmic resistance of the line is computed from the phasor information, and an average line temperature is computed from the ohmic resistance. This allows to determine the average line temperature without dedicated temperature sensors. The average line temperature represents the actual average temperature and is largely independent of assumptions regarding line parameters.

Determining an operational limit of a power transmission line

A method, device and computer program product for the prediction of the stability of an electric power network, where the method is executed after a fault or contingency has occurred, and comprises the steps of (a) during a time interval in which the network is in a transient condition, determining for at least one load connected to the electric power network, at least one parameter describing an estimated steady state behavior of the load, (b) executing a load flow calculation for the electric power network using the least one parameter describing the estimated steady state behavior the at least one load, (c) determining, if the load flow calculation indicates stability has a solution, that a future stability of the electrical power network exists, or, if the load flow calculation indicates instability does not have a solution, that a future stability of the electrical power network does not exist.

Stability prediction for an electric power network

In a method, computer program and system for estimating a state of an electric power transmission network, time-stamped phasor measurements are made by phasor measurement units () located at a first set of locations () throughout the network, and a plurality of voltage and/or current phasors at a second set of locations is estimated, where the locations of the first () and second sets of locations are distant from one another, and a status of network elements (L,L) that are remotely located from the phasor measurement units is inferred from the phasor measurements and the estimated phasors. In a preferred variant of the invention, the network elements are transmission lines (L. . . L), switchgear, under load tap changing transformers, compensation devices () or FACTS devices, and the status information describes whether a network element (L,L) is electrically connected to or disconnected from the network.

Electric power transmission network state estimation

For the control of an electric power transmission network, where local protection functions are implemented by a plurality of local protection devices () located at a plurality of locations throughout the network, the following steps are executed In a preferred variant of the invention, values of predetermined parameters that are used in the protection function, in particular protection threshold values, are adapted to measured values.

Protection of an electric power transmission network

The method according to the invention is based on a configuration model of a part of an electrical power distribution network, describing a totality of possible configurations of appliances. The configuration model is used to systematically produce () all the possible configurations which satisfy a predetermined set of functional requirements, in which case each possible configuration may have at least one associated characteristic value, and a solution configuration is defined which optimizes this characteristic value. It is thus possible to produce an optimum configuration automatically, without any need for expert knowledge about the appliances used in the configuration. In one preferred embodiment of the invention, a simulation model for simulation of a technical response of the solution configuration is produced automatically (). It is thus possible to test one or more solution configurations by simulations (), without any need for expert knowledge about the characteristics and simulation models of the appliances used in the solution configuration.

Configuration of a part of an electrical power distribution network

In a method and system for assessing the stability of an electric power transmission network, where at least one pair of measurements including a first and a second measurement point (P P ), each measurement point comprising a voltage and a current phasor, is processed and where a Th&eacute;venin impedance (Zt) and a present stability margin (dS(k)) value are computed, a validity indicator (v) is computed which depends on whether there is a difference between the first and second measurement points and whether there is a difference between corresponding estimated first and second load impedances (Za). From all validity indicators (v) associated with all of the at least one pair of measurements a quality indicator (q) is computed that is associated with the Th&eacute;venin impedance value (Zt) and with the present stability margin (dS(k)). The invention allows to continuously compute and output a present stability margin (dS(k)) value and to provide a measure (q) of its quality.

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Baden-Dättwil, Switzerland

Christian Rehtanz