Abb Research Ltd.

Petr Korba

Mats Larsson

Bertil Berggren

Alexandre Oudalov

Rajat Majumder

Peter Karl Steimer

Tord Bengtsson

Stefan G Thorburn

Christian Rehtanz

Srinivas Ponnaluri

Marek Zima

Andrew D Paice

Rudolf Wieser

Jose Taborda

Johan Lindberg

Swakshar Ray

Rafael Segundo

Albert Leirbukt

Alexander Oudalov

The invention provides improved control of a power transmission system having a first group of measurement units in a first geographical area providing a first set of phasors and a second group of measurement units in a second geographical area providing a second set of phasors, where the phasors in the sets are generated at the same instant in time. In this system the power control device includes a phasor aligning unit that time aligns the first and second sets of phasors and a control unit that compares each set of phasors with a corresponding phasor number threshold, determines that a first control condition is fulfilled if each phasor number threshold has been exceeded and enables the provision of a common signal if the first control condition is fulfilled. The common signal is based on the obtained phasors in the first and second sets.

Control of a power transmission system

A method and controller are provided for the compensation of time delays in remote feedback signals in power system control. The method includes converting the time delay into a phase shift and calculating four compensation angles from the phase shift. The optimal compensation angle is determined and applied to the remote feedback signals. A technique of equipping a controller with a global clock is also disclosed.

Time delay compensation in power system control

The present disclosure relates to power system sensitivities as computed from power flow parameters and control parameters of a Power Flow Control Device (PFC). To this end, control parameter variations are applied to or generated by a PFC, and comprise variations in a control input u, a control effort e (injected series voltage, inserted series reactance), or a control effect q (power flow, active power transfer, phase-shift, current). A power flow response measuring unit measures a variation of a power flow response such as current, active or apparent power, in a way sufficiently synchronized with the control parameter variation to allow establishing an unambiguous causal relationship or correspondence in the form of a power system sensitivity. The latter may be on-line adapted to continuously reflect an updated aspect of the power system behavior, and thus enable an improved, fast and reliable power flow control in power systems comprising a meshed power network with two parallel flow paths or corridors connecting two areas or sub-systems.

Determination and use of power system sensitivities

Exemplary embodiments of the present disclosure provide a method and controller for damping multimode electromagnetic oscillations in electric power systems which interconnect a plurality of generators and consumers. The controller for damping such oscillations includes a phasor measurement unit (PMU) and a power oscillation damper (POD) controller. Each oscillating mode signal is damped and then superposed to derive a control signal. A feedback controller is used to feedback the control signal to a power flow control device in the power system.

Damping electromagnetic oscillations in power systems

The present disclosure is concerned with the combined voltage or power flow control and damping of electromechanical oscillations in an electric power system by Flexible AC Transmission System (FACTS) devices or High Voltage DC (HVDC) transmission devices. To this end, information about a state or operating point of the power system is generated from suitable second system signals (y) and a control parameter (cp) of a FACTS controller is derived therefrom. The control parameter and a first system signal (y) are used in the calculation of a control command (u) defining the settings of the FACTS device. Following a change in the state of the power system such as a change in the topology of a transmission network, poorly damped or even unstable oscillations are avoided by appropriate re-tuning of the control parameter of the damping or stabilizing equipment.

Damping electromechanical oscillations in power systems

The disclosure relates to a converter control unit or power system stabilizing unit for counteracting oscillations in electric power systems that is equipped and employed to provide and processes information for system-wide monitoring, protection, control and metering. It comprises means for synchronized (e.g. via GPS or another absolute/global time reference) sampling of voltages and/or currents, means for down-sampling in order to decrease the number of samples, and means for calculating phasors, i.e. time stamped amplitude and phase angle of the voltages and/or currents.

Converter control unit

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 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.

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Turgi, Switzerland

Petr Korba