Research On Some Problems Of Power System Stability And Control In The Context Of Smart Grid

Due to the shortage of fossil resources and the deterioration of environment,people are gradually realizing the importance of renewable energy in guaranteeing thesustainable development of society and economy. As the most important secondaryenergy, with the clean and efficient characteristic, electrical energy would serve as themain conversion form of renewable energy. Power system, as the carrier of electricity,has unshirkable responsibility to ensure the renewable energy access, whilemaintaining stable operation. The emerging issues, such as increasingly systemoperational requirements, the larger amount of renewable energy access, and the moreactive demand-side, have driven the electrical power industry towards the goal ofsmart grid. In the context of smart grid, this thesis is focused on the field of powersystem static voltage stability and control, controlled system splitting, as well asdemand response. The major works are listed in the following:First, a new calculation method of load adjustment with considering the staticvoltage stability of power system is proposed, which is solved based on the staticvoltage stability region in active load injection space (SVSR_IS). In order to promisethe accurate results, it is necessary to construct a more precise expression of SVSR_IS.Therefore, a two-stage method based on clustering analysis is proposed. It firstreduces the computational burden, and then could obtain a more accurate hyper-planeapproximation with considering the curvature change of the stability region boundary.Due to the hyper-plane form and the embedded global information of SVSR_IS, theproposed method could give better load adjustment result in short time.Second, construction of high-dimensional stability region is difficult. However,the local feature of some certain control problems in power system makes it possibleto put forward a stability region that only involving local varaibles. At this point ofview, a hyper-plane form approximation of the relationship between load margin andlocal injection space parameters (HFAL_I) is proposed. Similar to the calculation ofSVSR_IS, HFAL_Icould also be solved using a two-stage method while only somedetail steps need modified. Based on HFAL_I, system load margin and the adjustmentof local injection variable could be easily derived. Third, a multi-level partitioning theory based method for power system controlledsplitting is proposed. Three main steps, called coarsening, initial partitioning andrefinement, are executed in sequence to achieve optimal splitting boundary. Someoperational characteristics of power system are ultilized to accelerate searching speed.In coarsening process, a novel power flow tracing method based on the group ofsynchronized generators is proposed to improve the efficiency, and then a0-1programming problem with considering topology connectivity constraints is solved inrefinement process to guarantee the high quality of partitioning and the connectivityof each island.Last, with the development of smart grid, demand response could be turned intoone kind of dispatchable resource through the state-of-the-art technology, and then itcould play a role in the power system operation and control. A framework of demandresponse providing ancillary services is given based on the large-scale centralizedcontrol of thermostatically controllable load (TCL). Two scenario of TCL attendingwind power system control, for example, wind farm output smoothing and staticvoltage stability control, are simulated. Simulation results showed that demandresponse could reduce system operational cost and improve system reliability at thesame time. In case of contingency, demand response could also serve as large reservesin short time to help maintaining system stable.