Abstract: A modular multilevel voltage source converter and a method and computer program product for handling circulating currents in such a modular multilevel voltage source converter are described. A control unit of the voltage source converter determines a circulating current control signal contribution (ER1?ER2+2VCM) for a phase leg based on the sum of cell voltages in the upper phase arm of the phase leg, the sum of cell voltages in the lower phase arm of the phase leg and at least one modulation reference and combines the circulating control signal contribution with a modulation reference used for one of the phase arms in order to obtain a modified voltage reference for controlling the phase arm to handle a circulating current while a waveshape is formed.

Abstract: A modular multilevel voltage source converter and a method and computer program product for handling circulating currents in such a modular multilevel voltage source converter are described. A control unit of the voltage source converter determines a circulating current control signal contribution (ER1?ER2+2VCM) for a phase leg based on the sum of cell voltages in the upper phase arm of the phase leg, the sum of cell voltages in the lower phase arm of the phase leg and at least one modulation reference and combines the circulating control signal contribution with a modulation reference used for one of the phase arms in order to obtain a modified voltage reference for controlling the phase arm to handle a circulating current while a waveshape is formed.

Abstract: A system for distributing electrical current to a plurality of loads includes a first sensor coupled to an input of a protection zone for measuring a first current entering the protection zone, wherein the protection zone includes at least a portion of an electrical distribution feeder. The system also includes a second sensor coupled to an output of the protection zone for measuring a second current exiting the protection zone, and a processor coupled to the first sensor and to the second sensor. The processor is programmed to receive measurements representative of the first current and the second current, and calculate a reactive current differential of the protection zone based on the first current and the second current. The processor is also programmed to compare the reactive current differential with a fault threshold, and generate an error notification if the reactive current differential is greater than the fault threshold.

Abstract: A method of damping power system oscillations include obtaining a time synchronized damping control signal from a remote location and determining a communication time delay in receiving the time synchronized damping control signal from the remote location. The time synchronized damping control signal is then modified based on a phase compensation factor and an amplitude compensation factor determined from the time delay. Finally, a damping signal is generated based on the modified time synchronized damping control signal.

Abstract: A method of damping power system oscillations includes obtaining an AC measurement signal from a power system location and determining oscillation frequency values in the AC measurement signal. A plurality of single signal components are extracted from the AC measurement signal by subtracting a plurality of processed measurement signals from the AC measurement signal and a damping signal is generated based on the plurality of single signal components. Each of the plurality of processed measurement signals are generated by time delaying the AC measurement signal with a time delay associated with each of the oscillation frequency values other than the oscillation frequency value of the single signal component to be extracted.

Abstract: An electric distribution system includes at least one feeder and a protection and control system. The feeder includes at least one segment including a first end and an opposing second end. The protection and control system includes a protective device and an electric current measuring device coupled to the segment proximate each end. The system further includes at least one processor coupled in communication with the electric current measuring devices. The at least one processor is programmed to determine a difference between a synchronized first electric current measured proximate the first end and a synchronized second electric current measured proximate the opposing second end and determine a switching condition of the protective devices as a function of the difference between the synchronized first and second electric currents.

Abstract: 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.

Abstract: A method, device and computer program product for providing improved control of power or voltage oscillation damping in a power transmission system. The device includes a magnitude obtaining element configured to obtain an instantaneous magnitude of a signal representing a deviating oscillation in at least one element of the power transmission system, a slope investigating element configured to determine the rate of change of the signal, and a first processing block including an integrating element configured to integrate the instantaneous magnitudes with an integrating factor that is based on the determined rate of change. The first processing block is further configured to form a phase compensation angle based on the integrated instantaneous magnitude for use in a damping control signal generating unit in order to provide power or voltage oscillation damping of the system.

Abstract: A method of damping power system oscillations include obtaining a time synchronized damping control signal from a remote location and determining a communication time delay in receiving the time synchronized damping control signal from the remote location. The time synchronized damping control signal is then modified based on a phase compensation factor and an amplitude compensation factor determined from the time delay. Finally, a damping signal is generated based on the modified time synchronized damping control signal.

Abstract: A system for distributing electrical current to a plurality of loads includes a first sensor coupled to an input of a protection zone for measuring a first current entering the protection zone, wherein the protection zone includes at least a portion of an electrical distribution feeder. The system also includes a second sensor coupled to an output of the protection zone for measuring a second current exiting the protection zone, and a processor coupled to the first sensor and to the second sensor. The processor is programmed to receive measurements representative of the first current and the second current, and calculate a reactive current differential of the protection zone based on the first current and the second current. The processor is also programmed to compare the reactive current differential with a fault threshold, and generate an error notification if the reactive current differential is greater than the fault threshold.

Abstract: An electric distribution system includes at least one feeder and a protection and control system. The feeder includes at least one segment including a first end and an opposing second end. The protection and control system includes a protective device and an electric current measuring device coupled to the segment proximate each end. The system further includes at least one processor coupled in communication with the electric current measuring devices. The at least one processor is programmed to determine a difference between a synchronized first electric current measured proximate the first end and a synchronized second electric current measured proximate the opposing second end and determine a switching condition of the protective devices as a function of the difference between the synchronized first and second electric currents.

Abstract: A method of damping power system oscillations includes obtaining an AC measurement signal from a power system location and determining oscillation frequency values in the AC measurement signal. A plurality of single signal components are extracted from the AC measurement signal by subtracting a plurality of processed measurement signals from the AC measurement signal and a damping signal is generated based on the plurality of single signal components. Each of the plurality of processed measurement signals are generated by time delaying the AC measurement signal with a time delay associated with each of the oscillation frequency values other than the oscillation frequency value of the single signal component to be extracted.

Abstract: A method, device and computer program product for providing improved control of power or voltage oscillation damping in a power transmission system. The device includes a magnitude obtaining element configured to obtain an instantaneous magnitude of a signal representing a deviating oscillation in at least one element of the power transmission system, a slope investigating element configured to determine the rate of change of the signal, and a first processing block including an integrating element configured to integrate the instantaneous magnitudes with an integrating factor that is based on the determined rate of change. The first processing block is further configured to form a phase compensation angle based on the integrated instantaneous magnitude for use in a damping control signal generating unit in order to provide power or voltage oscillation damping of the system.