POWER SYSTEM TRANSIENT STABILITY CONTROL WITH CONSIDERATION OF UNCERTAINTIES
Stability of power system ensures continuous and uninterrupted power delivery from generation to demands and measures the dynamic behaviour of different system characteristics subject to disturbances. Failure to maintain stability can lead to consequences ranging from disconnected buses and areas to cascading failures and system blackouts. Increased integration of renewable energy sources and involvement of demand-side into system operation in the recent years have introduced more intermittency into the power system. This intermittency increases the difficulty to maintain system stability and requires better control strategies to accommodate the high-level penetration of uncertainties in the power system operation. In addition to conventional control methods such as generator dispatch, numerous measures are considered to reduce the uncertainty introduced, such as wind curtailment, to act timely in case of instability, such as emergency load shedding, and also to utilize the flexible resources, such as energy storage systems. This research consists of methodologies that account for control measures both before and after the contingency to achieve the optimal balance between the economy and stability in system operation. The main research contributions are listed below: Firstly, a hybrid approach is proposed for the improvement of conventional optimal power flow (OPF) calculation, which utilizes the critical machine (CM) theory in the Extended Equal Area Criteria (EEAC). A detailed composite load model is later applied to capture a more accurate dynamic behaviour of the system. Secondly, a preventive-emergency coordinated control method is developed to maintain system transient stability in the presence of uncertain wind power generation. It coordinates between preventive control (generator dispatch and wind curtailment) and emergency control (emergency demand response) to achieve the optimal trade-off between system stability and economy. Thirdly, the effects of having actively controlled utility-scale Battery Energy Storage Systems (BESSs) systems are investigated, and a coordinated strategy that utilizes generator redispatch in preventive control and energy storage in both preventive and emergency control stage are developed. Finally, the flexibility of BESS is investigated. The model performance and parameter sensitivity of a new generic BESS model are firstly evaluated. An emergency control scheme is designed based on the results of evaluation, which includes both BESS and emergency load shedding scheme as post-contingency control measures. Proposed methodologies and strategies are evaluated on benchmark systems with industry-grade dynamic models and simulation software. Applicable cases from literature are also performed for comparative purpose. The simulation experimental results have verified the effectiveness of the proposed methodologies and strategies.
Renewable Energy Sources, Power Systems, Transient Stability Control, Uncertainties, Energy Storage Systems, Modelling
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