Flexibility Evaluation And Analysis Method Of Smart Grid Planning And Operation Control

Smart grid is a modern electric energy supply system to deal with a series of problems,such as resource shortage, environment pollution, etc., in human society. Compared withconventional power grids, smart grid sets much higher requirements on power gird planning,operation and management. The whole process of electric energy generation, transmission andcomsuption is required to be more efficient, economical and secure. Meanwhile, smart gridalso provides better controllability and user experiences.In power system analysis and calculation, system operation constraints are usuallyexpressed in rigid forms. On one hand, such a rigid expression method appears to be tooinflexible to meet with the inquirements on flexibility of smart grid planning, operation andmanagement. On the other hand, with the large number of application of new technologies,control methods of power systems are greatly enriched. Smart grids are required to controlsystem operation parameters flexibly according to the actual grid operating states. Thisdissertation introduces flexibility analysis method in industry process system design to powersystem analysis and optimization, and systematacially proposes flexibility evaluation andanalysis method of smart grid planning and operation control.Main research works and innovative points of this dissertation are as follows:1. The disadvantages of rigid constraints in conventional power system analysis are firstanalyzed. Then, the concept of power system flexibility expression and analysis method isproposed and compared with fuzzy set theory, probability theory, and grey theory. After that,flexibility in smart grid analysis is defined and classified. A one-dimension linear index is proposed to evaluate smart grid flexibility. According to the different constraint types inpower system operation, it is then extended from one-dimension to multi-dimension.2. Based on the flexible expression of equality and inequality constraints in optimalpower flow models, the flexible expression method of grid operation objective function isproposed. And the objective function is transferred to a flexible equality constraint. Then,taking grid operation economy, security and reliability into account, a multi-dimensionflexible comprehensive optimization model for smart grid economic dispatch is establishedand solved.3. Flexibility analysis method is applied in smart grid planning. System investmentcosts, operation costs and reliability benefits are evaluated flexibly in the whole planningcycle. Meanwhile, through the flexible expression of transmission line load rate constraints,some system power flow transmission ability is reserved, so that a certain degree of systemoperation security margin and adaptability to uncertain factors can be reserved.4. Based on the monitoring data from real-time dynamic thermal line rating (RT-DTLR)system, the real-time thermal stability limits of lines can be determined. Through the flexibleexpression of transmission line power flow constraints, line power flow can be controlledflexibly. Then, RT-DTLR technology is combined with conventional power system loadshedding strategies. Taking both system risks and benefits into account, a smart grid flexibleload shedding strategy involving RT-DTLR technology is established, and it is solved usingsatisfaction evaluation method.5. The realization method of improving power system operation level by use of loadflexibility is first elaborated. Then, acting as an important kind of flexible load in smart grid,the effect of electric vehicle charging and discharging activities to power system operation isanalyzed. Based on the analysis of guidance and management measures of electric vehicles,the load characteristic of electric vehicle battery swapping station (EVBSS) can be obtained.After that, a model for optimal charging/discharging strategy of EVBSS is established and solved, so that the daily load curve of EVBSS can be obtained and the load of EVBSS can bemanaged orderly. Finally, base on the daily load curve obtained, the effect of EVBSS load onpower grid operation is analyzed.6. Power system operation homogeneity analysis and evaluation method is proposed,and the relationship among system economy, security and homogeneity is analyzed. For theconsiderations of system operation states and security margins, degrees of power system statehomogeneity and inherent homogeneity are defined respectively. For the difficulties in directsolution of inherent homogeneity index, the flexibility analysis method proposed in thisdissertation is used. An optimal model based on flexible device load rate constraintparametersδ Uandδ Lis established and solved, so that the inherent homogeneity indexcan be obtained.Garver6-bus, IEEE14-bus and IEEE30-bus test systems are used to analyze and verifythe validity of the flexibility evaluation and analysis method of smart grid planning andoperation control proposed in this dissertation.