Transmission System Expansion Planning Considering Wind Farms

With integration of large-scale wind farms, transmission system needs to be upgraded to meet the growth of load and wind power. Although wind power is clean and renewable, wind farms can bring about significant unfavorable impacts on power systems due to their stochastic, intermittent and uncontrollable characteristics. With the expansion of wind power generation and thus the increasing quota of wind energy in power systems, these adverse influences could introduce an extra factor of uncertainties for power system planning and operation. A power network with a large proportion of wind power penetration will suffer more uncertain factors and power flow fluctuations. To address these challenges and improve the utilization of wind power, this thesis explores the impact of wind power on transmission system planning and operation, and then presents multi-objective transmission system expansion planning (TSEP) models with wind farms. The detailed work is as following:1) A transmission system planning method with risk-control strategies for power systems with wind generators is presented. First, some uncertainties associated with wind power generators are expressed with probability measures, and the probabilistic load flow is calculated by the combined use of cumulants and Gram-Charlier series. Then, risk-control strategies are introduced into the transmission system planning to enhance the ability of the system against security/reliability risks. A security risk index is then defined and a multi-objective transmission system planning model is next developed with the transmission investment and the security risk index as the objective functions, and in this way the security/reliability and economics associated with transmission system planning schemes could be well compromised.2) A transmission system planning method with available transmission capacity (ATC) for power systems with wind generators is presented. Firstly, a probabilistic ATC model of the power system is formed considering the correlation between the random input variables and outage rate of the equipments. Then, a hybrid method, combining the Monte Carlo simulation based on Latin hypercube sampling with the sensitivity analysis method, is developed to solve the ATC model. Lastly, a multi-objective transmission system expansion planning model with the objective functions composed of transmission investment and the expected value of ATC is developed. The presented work represents a superior model for transmission system expansion planning in terms of reliability and economy, which is advantageous to the integration of large-scale wind farms.3) A transmission system planning method considering combined operation of wind farms and energy storage systems (ESS) is presented. ESS is applied to smooth the fluctuations of wind power outputs, and hence improve the security and economics of the power system concerned. A strategy for the combined operation of a wind farm and an ESS is next presented to optimize the capacity of ESS installed. Then, a transmission system expansion planning model is developed with the sum of the transmission investment costs, the operating costs of the systems as the objective function to be minimized. It aims to decrease the cost of ESSs, smooth the fluctuation of wind power and improve the utilization of wind power.4) A transmission system planning method based on demand-side response for power systems with wind generators is presented. Demand-side response is explored to cope with the uncertainty due to wind farms. The interruptible load and electricity price incentive are used to smooth the load curve. Then, a bi-level transmission system planning model based on demand-side response is developed with minimized objective functions, i.e. the sum of the transmission investment costs, the cost of demand-side response, and the punishment cost of curtailed wind energy. Lastly, the effectiveness of demand-side response for transmission system planning considering wind farms is verified.Finally, several conclusions are obtained based on the research outcomes, and directions for future research indicated.