Abb Research Ltd.

Abb Schweiz Ag

Abb Technology Ag

Abb Power Grids Switzerland Ag

Marek Zima

Mats Larsson

Christian Rehtanz

Joachim Bertsch

Petr Korba

Andreas Suranyi

Albert Leirbukt

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 present disclosure relates to monitoring of electromechanical oscillations in electric power systems, and their identification by an adaptive algorithm based on a repeatedly measured and evaluated signal. In order for an estimation of parameters of a model of the power system to reasonably converge, proper initialization of the recursive calculation is required, including the definition of tuning parameters constraining the model and the calculation. Initialization for a second signal to be exploited can then be simplified by copying the set of tuning parameters tuned previously for a different signal. A conditioning gain multiplying the second signal establishes compatibility between the different signals, and a signal pre-filter in turn discards contributions beyond a frequency band comprising typical electromagnetic oscillations.

Initializing an estimation of dynamic model parameters

The present invention is concerned with a method for real-time emergency control of power transmission networks, based on a modification of the model predictive control (MPC) approach. Following the detection of a contingency at time tonly one nominal trajectory xis approximated, together with its corresponding trajectory sensitivities for evaluating the effect of various key parameters or potential control actions. An optimum input control is finally identified via the solution of a cost function including e.g. a punishment for excessive load shedding. The process is started only if the nominal trajectory does not remain within acceptable trajectory limits.

Real-time emergency control in power systems

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

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

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.

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Baden, Switzerland

Marek Zima