Optimal Planning Of Wind-Thermal Generation And Transmission Systems

Development of energy consumption and progressive environmental deterioration have driven many countries in the world to expand the exploration of sustainable energies. Wind energy, as a widely distributed sustainable energy, has captured comprehensive attention. Recently, with the adjustment of national energy policy, the maturity of wind turbine technology, and the decrease of installed capital, the development of wind power has entered an extensive stage in our country. However, owing to the stochastic, intermittent, and uncontrollable nature, the integration of wind power will create great challenges for the safety operation of power systems.Due to the geographical compensation condition of energy resources(i.e., the windy areas are always be/near to the areas with abundant coal reserves) and the long-distance diverse distribution between energy resources and load centers in our country, one feasible plan of utilizing the large-scale wind power while guaranteeing the demand security of load centers is to build bundled wind-thermal generation and transmission systems(BWTGTSs).To handle the issues regarding the planning of BWTGTSs, researches on the coordinated wind-thermal generation scheduling simulation, the transmission power(TP) modeling, the optimal planning of bundled generation and transmission systems, and the solving optimization algorithms, etc., have been investigated in this thesis.Firstly, the compensating situation of power outputs of bundled wind-thermal generation systems(BWTGSs) is analyzed. Based on this analysis, an optimal BWTGS planning model, which takes the unit generation cost as the objective function, the compensating ability and the installed thermal generation capacity, etc., as the constraints, is established. A simulated-annealing-based algorithm is developed to solve the model. Results from the case studies show that because of the inherent operation constraints of thermal generating units(TGUs), the matched installed capacity of thermal generation should be greater than the wind generation capacity.Secondly, a long-term coordinated wind-thermal generation scheduling model considering the sequential system operation constraints is built to simulate the daily operation behavior of BWTGSs and obtain a more accurate operation cost. According to the operation requirement and compensating aim, different transmission modes that BWTGTSs may adopt are proposed. By analyzing the rules of cost changing with the installed capacity of TGUs and incorporating the long-term coordinated wind-thermal generation scheduling model, a unit-commitment-based optimal planning model of BWTGSs is formed. Taking the characteristics of the algorithms and the problems to be solved into account, the solving algorithms with accelerating techniques, such as the prejudgment of non-feasible states, the saving-branch-cost technique, etc., for the two models are given. Numerical results show that for a certain wind farm, different matched schemes of TGUs result in different operation costs, capital costs and maintenance costs of BWTGS. Large capacity TGUs, due to their better input-output characteristics, should be the major type of BWTGS.Thirdly, a two-stage optimal planning model for HVAC-based BWTGTSs is presented. At the inner optimal stage, the impact of TP of bundled system on the unit generation cost of planning schemes is analyzed. And based on this analysis, a search algorithm called window search method is proposed to search the optimal basic TP as well as the matched TGU scheme. At the outer optimal stage, the genetic algorithm is employed to further optimize the schemes of wind farm and transmission system. Case studies are conducted on two test systems and results indicate that the wind generation scheme, the matched thermal generation scheme, the basic TP selection and the TP mode will influence the unit generation cost of HVAC-based BWTGTS. When adopting the large-capacity TGUs, the high voltage transmission system, and the flexible sectionalized demand-oriented TP, the unit generation cost of HVAC-based BWTGTS achieves the minimum.Finally, by analyzing the duration power output characteristics of HVDC-based bundled system, the planning constrains for the bundled system is determined, and the methods for calculating the operation cost and the generations of sending and receiving systems are presented; and then an optimal planning model of HVDC-based BWTGTS is established accordingly. Numerical studies on different planning forms, such as the bundled generation planning, the single thermal generation planning, etc., are conducted. Results from the studies indicate that by comparing single thermal generation planning, the bundled generation planning is a more suitable planning manner because of the no-fuel-cost wind power and the less influence on the receiving system. Meanwhile, the results also show that the capacity of single TGU can affect the unit generation cost of BWTGTS.