Abstract
Remote and regional areas are usually supplied by isolated and self-sufficient electricity systems, which are called as microgrids (MGs). To reduce the overall cost of electricity production, MGs rely on non-dispatchable renewable sources. Emergencies such as overloading or excessive generation by renewable sources can result in a substantial voltage or frequency deviation in MGs. This paper presents a supervisory controller for such emergencies. The key idea is to remedy the emergencies by optimal internal or external support. A multi-level controller with soft, intermedial and hard actions is proposed. The soft actions include the adjustment of the droop parameters of the sources and the controlling of the charge/discharge of energy storages. The intermedial action is exchanging power with neighboring MGs, which is highly probable in large remote areas. As the last remedying resort, curtailing loads or renewable sources are assumed as hard actions. The proposed controller employs an optimization technique consisting of certain objectives such as reducing power loss in the tie-lines amongst MGs and the dependency of an MG to other MGs, as well as enhancing the contribution of renewable sources in electricity generation. Minimization of the fuel consumption and emissions of conventional generators, along with frequency and voltage deviation, is the other desired objectives. The performance of the proposal is evaluated by several numerical analyses in MATLAB®.
Highlights
Due to technical and geographical limitations, it is difficult to extend the existing transmission and distribution lines to remote and regional areas
Except the towns at Australia’s east coast that are supplied through the National Electricity Market (NEM) and those few at its southwest that are supplied through the south-west interconnected system (SWIS), most towns in Australia’s regional and remote areas, in which almost 31% of the population lives, are supplied by local generators running on diesel or gas [1], which is expensive
Consider study case 8, in which MG-1 is defined as a PMGOG while MG-4 is defined as a PMGOL
Summary
Due to technical and geographical limitations, it is difficult to extend the existing transmission and distribution lines to remote and regional areas. The key advantages of the proposed SEC are: 1) alleviating the emergency of an MG; 2) realizing an acceptable voltage and frequency deviation in remote area MGs after emergencies, at least cost, while satisfying the technical constraints; 3) minimizing the rate of load-shedding and curtailment of NDDs in MGs. the main contributions of the paper can be summarized as: 1) developing an optimization-based SEC to remedy emergencies at remote-area MGs; 2) formulating an OF that considers controlling dispatchable DERs, curtailment of non-essential loads and NDDs, as well as the life loss value of BESSs, along with technical constraints, such as spinning reserve, the dependency of an MG to external MGs, the contribution of renewable sources and power loss in tie-lines; 3) validating the effective operation of the proposed technique using numerical analyses. Five Appendices are provided at the end of the paper that respectively discuss the operational principles of DRS, employed power flow analysis when evaluating the system and Genetic algorithm when solving the optimization problem, some possible interconnection topologies amongst neighboring MGs, and the probabilistic modeling of NDDs for the studies of this research
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