Power System Oscillations
Chapter 10: Damping by Electronic Power System Devices
Abstract
So far, we have considered the damping of power system oscillations by power system stabilizers that act through the excitation systems of the generators. The generators act to amplify the power of these controllers so that they can add damping to the electromechanical oscillations. There are other system elements which can act as power amplifiers, for example, high-voltage direct current links, static VAr compensators and FACTS devices. Generally, these devices are placed in a power system for some reason other than to add damping to power system oscillations. However, once installed, their control design may be able to increase the damping of certain electromechanical modes as well as satisfying the primary requirements of the device. Because electronic devices are not directly involved with electromechanical oscillations, damping using these controls is not as straightforward as damping using power system stabilizers on the generators. It is particularly difficult to attain robustness to large changes in operating conditions. We will show that this is due to the large changes in the positions of the poles and zeros of the transfer functions of the devices when the operating conditions change.
