Abb Research Ltd.

Abb Technology Ag

Abb Schweiz Ag

Abb Power Grids Switzerland Ag

Joachim Bertsch

Christian Rehtanz

Marek Fulczyk

Marek Zima

Marian Sobierajski

Mats Larsson

Martin Naedele

Valentin Bürgler

Andreas Suranyi

Odd Lekva

Mehmet Kaba

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 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, 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

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

A method is disclosed for the identification of weak and/or strong nodes of an electric power transmission system. Electric parameters characterizing nodes and branches of an electric power transmission system are subject to computational treatment to obtain equations of power flow in all nodes of the system at assumed 100 percent system load value. Using earth as the reference point, nodal impedance values are computed for all nodes, and used to construct a P-Q curve which presents the functional relation between the system's reactive and active load. The nodal coefficient of voltage stability is determined as the relative distance between the base load point of that node and the critical point on the P-Q curve situated most closely to the base point. The coefficient is compared with a threshold value considered to be a safe margin to maintain voltage stability for a given node.

Method of the identification of weak and/or strong nodes of an electric power system

The subject of the invention is a method of identification of weak and/or strong branches of an electric power transmission system. In the inventive method electrical parameters characterizing the nodes and branches of an electric power transmission system are subjected to computational treatment in order to obtain equations of power flow in all nodes of the system at assumed 100 percent system load value. Then an electric model of a branch is assumed and a curve P-Q is constructed which shows the functional relation between active and reactive load in the system. For the assumed branch model a branch voltage stability coefficient is determined. Then the analysed system is overloaded by increasing the total system load up to 120% base load and the branch voltage stability coefficient is determined again. The numerical values of the appropriately determined coefficients are compared with threshold values considered to be a safe margin for the maintenance of voltage stability for the given branch.

Method of the identification of weak and/or strong branches of an electric power transmission system

Method and device for assessing the stability of an electric power transmission 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.

Growing community of inventors

Kilchberg, Switzerland

Joachim Bertsch