Abstract:
Attention is increasing on transient stability and secure mode of operation for power systems with asynchronous generation. This is due to asynchronous mode of generation like wind farms, increasing in capacity and displacing existing high inertia synchronous generation. Participation of wind farms, which are primarily inertia decoupled during transient disturbance, will become necessary to comprehensively analyse framework like energy function and coherency based reduction methods. This thesis investigates the impact of reduced system inertia due to asynchronous generation, on transient stability of power systems. This thesis proposes an energy function approach to assess power system transient stability impacts following increased penetration of asynchronous generation plants. The asynchronous wind farm generation is considered as an equivalent conventional synchronous generator with negligible inertia. Assessment has been carried out on single machine infinite system and three machine nine bus test system to compute critical energy and critical fault clearing time, from first principles, using potential energy boundary surface method. A new representation of plotting contours of critical clearing times on inertia space has been developed. This enables estimation of additional inertia required for a system due to inertia reduction from asynchronous generators. The results of the simulation and new graphical method confirms that transient stability margin of the system is impacted with increased penetration of asynchronous generation. This thesis also investigates coherency based analysis technique for network reduction to carry out transient stability analysis for a large power system network that has wind penetration. Identification of coherent groups targets to obtain simplified dynamic equivalent of system by aggregation of coherent generators and replacing it with an equivalent generator. The use of this equivalence can transform a large power system into a reduced model, localized into a small internal area containing the disturbance which impact stability. The New England, 39 bus 10 machine system has been used to demonstrate the methodology. Contingencies are applied with and without wind farm i.e., by replacing few synchronous generators with wind farm of similar capacity. This thesis also develops transient stability enhancement method for networks with asynchronous generation. When a machine inertia is reduced its first swing stability can be enhanced by line series compensation and also multi-swing stability using bang-bang control on series compensation. Compensation values and the lines that can participate in series compensation during contingencies are found.