(1990). ENERGY FUNCTION ANALYSIS FOR POWER SYSTEM STABILITY. Electric Machines & Power Systems: Vol. 18, No. 2, pp. 209-210.

Energy function analysis for power system stability

The invention includes an electric machine having a rotor, stator and at least one winding in the stator adapted to conduct a current, and a secondary winding, electrically isolated from the first winding and inductively coupled to the first winding, which may be used to control at least one of the output voltage and current of the first winding.

Architecture for electric machine

Impact of Low Rotational Inertia on Power System Stability and Operation

A method, system and computer program product enhance the commercial value of electrical power produced from a wind turbine production facility. Features include the use of a premier power conversion device that provides an alternative source of power for supplementing an output power of the wind turbine generation facility when lull periods for wind speed appear. The invention includes a communications infrastructure and coordination mechanism for establishing a relationship with another power production facility such that when excess electrical power is produced by the wind turbine facility, the excess may be provided to the power grid while the other energy production facility cuts back on its output production by a corresponding amount. A tracking mechanism keeps track of the amount of potential energy that was not expended at the other facility and places this amount in a virtual energy storage account, for the benefit of the wind turbine facility. When, the wind turbine power production facility experiences a shortfall in its power production output it may make a request to the other source of electric power, and request that an increase its power output on behalf of the wind turbine facility. This substitution of one power production facility for another is referred to herein as a virtual energy storage mechanism. Furthermore, another feature of the present invention is the use of a renewal power exchange mechanism that creates a market for trading renewable units of power, which have been converted into “premier power” and/or “guaranteed” by secondary sources of power source to provide a reliable source of power to the power grid as required by contract.

System, method and computer program product for enhancing commercial value of electrical power produced from a renewable energy power production facility

The paper proposes a new test function to be used in an existent performance index for detection of proximity to a static voltage collapse point. This test function is based on a reduction of the load flow Jacobian with respect to the critical bus of a system. The test function is compared with known singular values and eigenvalues indices, and with other previously proposed test functions. A thorough analysis of the similarities, advantages, and disadvantages of all these indices and test functions is presented. The techniques are tested and compared on the IEEE 300 bus test system, showing the effect of system characteristics and limits in these indices and functions.

Comparison of performance indices for detection of proximity to voltage collapse

Analytic investigations of interarea oscillation damping of an idealized two-machine system using active-power modulation of three- and four-terminal high-voltage dc (HVDC) transmissions are presented. It is shown that, generally, the pairing of two terminals gives the highest damping. Based on the analytical results, recommendations for how the pairing should be made are developed. Simulations, both on a two-machine system and on a more realistic 23-machine system, verify the analytical results.

Interarea Oscillation Damping Using Active-Power Modulation of Multiterminal HVDC Transmissions

A method, voltage source converter and computer program product for limiting the current in a DC power transmission system are disclosed. The voltage source converter has an AC side and a DC side and a fault current path between these sides. It furthermore includes a control unit and at least one switching unit of a first type provided in the fault current path and that includes a primary switching element together with an anti-parallel secondary controllable rectifying element. Based on a fault being detected in the DC power system when the primary switching elements of the converter are blocked, the control unit changes the control of the controllable rectifying element from acting as a non-controllable rectifying to acting as a controllable rectifying element.

Fault current limitation in dc power transmission systems

A rotating electric machine for direct connection to high-voltage networks, in which the magnetic circuit adapted for high voltage comprises a rotor, stator and main and auxiliary windings in operative relation. At least one of the windings is a conductor surrounded by a magnetically permeable, field confining insulation system.

Method and device for controlling the magnetic flux in a rotating high voltage electric alternating current machine

In this paper, a new dc switchyard structure for a multiterminal dc (MTDC) grid is proposed. Fast fault current breaking capability, which is essential for a dc grid, can be achieved with available HVDC breaker solutions (e.g., ABB's hybrid HVDC breaker). However, the hybrid HVDC breaker concept also opens up possibilities for unconventional (relative to ac) switchyard solutions which may be more cost effective. The main aim of this paper is to expound how the proposed dc switchyard can be built with hybrid HVDC breakers in a configuration where the number of components is much less compared to a conventional switchyard structure. After that, the switchyard operation, fault current handling flexibility, and actions against component failure are described conceptually. Finally, the performance of the proposed switchyard is validated and compared with that of a conventional double breaker double busbar switchyard structure for selected cases through time-domain simulations

An Alternative Method to Build DC Switchyard With Hybrid DC Breaker for DC Grid

Converter control is an important aspect of voltage-source-converter high-voltage dc (VSC-HVDC) based multi-terminal dc grids. Variants of power drooped against dc voltage control have previously been proposed for this purpose. However, there is at this time no clear methodology available on how to select the size of the droop constants for distributing a power mismatch, following, e.g., a converter trip, on several converters. This paper proposes a methodology for establishing droop constants for a variant of power drooped against dc voltage called pilot voltage droop control. The methodology is derived from the basic control laws in a straight forward fashion and the accuracy is exemplified by time domain simulations in Digsilent's Powerfactory platform.

Bertil Berggren

Papers

Interarea Oscillation Damping Using Active-Power Modulation of Multiterminal HVDC Transmissions

Fault current limitation in dc power transmission systems

Method and device for controlling the magnetic flux in a rotating high voltage electric alternating current machine

An Alternative Method to Build DC Switchyard With Hybrid DC Breaker for DC Grid

DC Grid Control Through the Pilot Voltage Droop Concept—Methodology for Establishing Droop Constants