Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
Storage system is one of the critical components of the microgrid. Storage system has broad applicability in short-term and long-term operations of microgrid. Storage systems are fast response devices which add flexibility to the control of the microgrid, and furthermore provide economical benefits by storing energy at times of excess power and generating energy at times of low generation. Moreover, storage systems can mitigate the frequent and rapid power changes of renewable resources and therefore solve the volatility and intermittency problems associated with renewable resources.
The storage systems has existed for many decades, however, the impact of storage systems in future grids, incorporating microgrids, is receiving more attention than ever from system operators. In addition, the storage systems continue to evolve as new technologies are introduced. Considering these issues, modeling of the storage systems operation would an essential task to help operators in enhancing the microgrid operation from both economical and security points of view. The microgrid security means that a feasible power flow solution should be obtained in base case and contingency operation of microgrid. The base case is the normal operation of the microgrid when there is no outage in components. In contingency cases, however, some of the generating units and/or transmission lines would be out of service. The robust operation of the microgrid, as well power system in general, requires consideration of contingencies. If possible system contingencies are not determined and taken into account, dramatic and costly blackouts are likely to happen, which would provide inconvenience and unexpected costs for electricity customers. Therefore, contingencies are considered in microgrid operation so that the microgrid will operate at all times and unwanted events, such as instability, voltage collapse, and cascaded outages would not occur.
In this report, the economic and emergency operations of the storage system in the microgrid are investigated. In base case operation of the microgrid, the storage system provides economic benefits by storing energy at times of low electricity prices and using the stored energy at times of high electricity prices. Accordingly, it facilitates peak shaving and load shaping and results in reduction in electricity costs. In emergency cases, when there is a microgrid component outage and we have contingencies, the storage system would be used as a generation resource to compensate the lost generation due to generating unit outages, and furthermore satisfy system security. Preventive (precontingency) and corrective (post-contingency) actions of storage system are taken into consideration in the security-constrained unit commitment (SCUC) problem. The cost of system operation is minimized and at the same time the system security is satisfied. Appropriate storage system corrective and preventive control actions for managing contingencies represent a trade-off between economics and security in a microgrid. Both actions are introduced and compared, since the preventive dispatch is very conservative and could be expensive for considering all potentially dangerous contingencies, and in contrast, the corrective action only applies to allowable post-contingency control adjustments. A complete formulation of the SCUC problem in the microgrid incorporating a practical storage system model is presented. Mixed integer programming(MIP) will be used to formulate the problem.
2012. , 38 p.