| This thesis presents two methods to damp electromechanical oscillations in large power systems such as Trans-Canadian grid. A control method, used in conjunction with Wide Area Measurement System (WAMS), is proposed to damp very low frequency inter-area modes of very large systems. This Global PSS requires knowledge of the eigenvectors of the targeted modes, and only a limited number of power stations are involved in its feedback loop. It does not destabilize other modes, and its robustness is assured. Besides mathematical proof, a series of simulations are conducted to validate the claims of the proposed Global PSS. The second solution is based on fast controllability of Voltage Source Converters (VSCs) connecting Renewable technologies to the power system. In this method, their injected Active and Reactive powers are modulated to improve power system damping. Mathematical formulations are developed to study the effectiveness of damping in relation to injection point along the transmission line. Taking nonlinearity, due to limit on active/reactive output power, into account, trade-offs of feedback gain constants with respect to saturation limits are studied. Phase-plane diagrams give clear picture of this nonlinearity, and simulation results confirm how high damping can be secured. |
