Research On Transmission Expansion Planning Based On Risk Assessment Theory

Transmission expansion planning problems based on risk assessment theories and techniques use comprehensive analysis of economic and risk to search optimum solution of transmission expansion planning with the consideration of new constrains.This dissertation has discussed the risk assessment theory and its application on transmission expansion planning. According to the risk calculation of voltage security, outage and investment and fuzzification of uncertainty factors, the new planning methods accurately reflected the characteristics of random and probabilistic in transmission systems that can not be found by deterministic methods. The main contributions of this dissertation are as follows:(1) Improved single-stage and multiple-stage transmission network planning models integrating with risk assessment techniques are proposed. Transmission investment cost and operation cost are involved in the proposed deterministic transmission planning models and an improved genetic algorithm is applied for solving. The risk assessment techniques are used to evaluate each solution that is obtained by the deterministic approach. According to the sum of deterministic cost and risk cost of each plan, the optimal plan is obtained.(2) A novel transmission planning approach that considers voltage security is proposed. Voltage security is the basic criterion for transmission system, so the voltage stable index (VSI) is proposed and applied on the risk assessment of transmission planning. An optimal load curtailment model that includes the security margin and cost is proposed that can be solved by a successive fuzzy linear programming method. The optimal transmission plan is decided by the sum of deterministic cost and risk cost.(3) A novel transmission planning model that considers uncertainties and integrates risk assessment techniques is proposed. Fuzzy transmission investment cost and fuzzy operation cost are involved in the transmission planning model and an improved genetic algorithm is applied for solving. The risk assessment techniques considering uncertainties are used to evaluate each solution that is obtained by the provirus method. According to the sum of fuzzy transmission investment cost, fuzzy operation cost and fuzzy risk cost, the proposed approach decides the optimal plan.(4) A novel transmission planning approach that considers outage risk of load bus is proposed. The model of outage cost is proposed to evaluate the outage risk level of load bus. The objective of transmission planning is the sum of investment cost and operation cost, integrating with security operation constrains and chance constraint of outage risk of load bus. The Monte Carlo simulation method and improved genetic algorithm are combined to solve this model and decided the optimal planning scheme according to a certain trust level.(5) A novel transmission planning approach that considers conditional values at risk (CVaR) is proposed. The CVaR index is adopted to evaluate the transmission investment risk. In the analysis of CVaR, the uncertainty of nodal power is taken as a random disturb and caused by which, the random distribution of transmission investment profit is obtained by solving the probabilistic power flow. After the CVaR index is adopted in objective functions and limitation of rate of return on transmission investment is taken as one of constraints, the transmission planning model is built up and solved by genetic method to achieve the optimal transmission planning.Analysis and comparison on the test cases illustrate the differences between the proposed methods and the differences between risk methods and deterministic methods and prove the feasibility, validity and practicability of the proposed planning models and solving algorithms in this dissertation.