Research Of Multi-objective Transmission Network Planning Considering Electricity Market

Great changes have been observed in the power mechanisms due to the competition of electricity market, which hence has a great influence on the planning technologies. The changes on the evaluation standard for the planning schemes are in great need because of the alteration of the planner and request of market mechanisms. In electricity market, transmission network plays an important role, because whether its capacity is enough and reasonable will greatly affect the benefit of each participator in the market, and even influence the security of power system. Therefore transmission network planning becomes essential. To solve these problems, this dissertation analyzes the new characteristics and requests of transmission network planning for the developing electricity market; introduces new methods to evaluate the schemes; builds novel models for transmission network planning; and solves the models by a new algorithm. The innovations of this dissertation are as the following:1) A novel model of multi-objective transmission network planning with congestion management is presented, considering generation cost, transmission investment cost and load curtailment cost together. In this model, the congestion management methods based on the OPF are applied with generation adjustment and load curtailment used to alleviate network congestion. As a result, the resource is collocated optimally, and the social welfare is improved.2) A novel model of multi-objective transmission network planning based on the market economic benefit is presented, considering the social welfare and investment return rate together. In the planning model a novel OPF model is used to compute the spot price considering the transmission charge in the objective function. After the economic benefit indexes of investment return rate and maximal social welfare are evaluated by using market information, the optimal scheme is searched with the objective function of maximal social welfare and the economic restriction of investment return rate. 3) A novel model of multi-objective transmission network planning based on the connection number is presented. In this model the connection number is used to represent the synthetic uncertainties of the random, fuzzy, and grey ones in the transmission network planning; a new DC power flow method of the connection number is presented to obtain the line power flow; a connection number comparison model is developed for the overload analysis, from which the reliable section of the network is obtained. The blind number is introduced to describe the flexibility of each reliable section, which is combined with the economics by the cost-benefit analysis method to evaluate the candidate schemes.4) A novel model for multi-objective transmission network planning is developed by combining the Scenarios Method and the connection number, in which the Scenarios Method and the connection number are used to represent the macroscopical and microcosmic uncertainties respectively. A general flexibility of the network for multiple scenarios is obtained on the basis of the scenarios probability, and then the cost-benefit analysis method is used to evaluate the planning schemes. Combined with the connection number, the Scenarios Method is improved in the application of transmission network planning, and its optimal scheme has better economics, flexibility and investment benefit.5) A novel model of multi-objective transmission network planning with ATC based on the theory of Fuzzy Set Pair Analysis (FSPA) is developed. In the planning model economics, reliability and flexibility are emphasized as three important factors to evaluate the schemes, and Available Transfer Capability (ATC) is proposed to quantify the flexibility of the network for the first time. After the concept of FSPA is introduced, the different expressions of fuzzy connection degree are developed according to different properties of multi-objectives in the transmission network planning. When the FSPA is used to solve the problem of multi-objective transmission network planning, the certain and uncertain information are both included in the planning model. After getting the sequences of the candidate schemes by using the certain information to evaluate the schemes, the certain information is used to carry out the risk analysis of the evaluation results.6) According to the shortcomings in the application of Greedy Randomized Adaptive Search Procedure (GRASP) in the transmission network planning, some ways are proposed to improve calculation speed and global convergence performance. In the construction phase, the improved line integrated validity index is introduced as the greedy function, and a restricted candidate list (RCL) is constructed by rule of proportion, from which elements are randomly chosen to form a feasible solution. The redundant lines in the feasible solution are eliminated according to the actual effect of the lines, which provides an efficient and economical initial network for local search, and the local optimal solution is sought by using exchange method to bring neighbor set to extend search space. As to the"dimension tragedy"brought by the network scale augmentation, five neighbor-pruning techniques are presented, which improves the computing speed of this algorithm. The above measures improve calculation speed and global convergence performance of GRASP. Some expanded ways are present for GRASP to solve the problem of multistage transmission network planning.The models and algorithm mentioned above take full consideration of the characters of transmission network planning in electricity market. The simulation results of two different size transmission networks indicate they are feasible and efficient, and provide new ideas to solve the problem of transmission network planning in electricity market.