Fuzzy logic based on-line load flow solution under normal/contingency conditions of electrical power systems

摘要

In this paper, a fuzzy load flow (FLF) algorithm based on fuzzy control theory is proposed. Fuzzy logic is used to deal with uncertainties such as bus injected active and reactive powers, bus voltage magnitudes and angles in a simple manner thereby reducing the system complexity and the time required for calculations. In the proposed method, the real and reactive power mismatches per voltage magnitude at each bus of the power system are chosen as the crisp input values, which are fuzzified into a fuzzifier. The process logic uses a rule base to explode the fuzzy output signals which are defuzzified and the crisp values are chosen as the corrections of voltage angle and magnitude at each bus of the system. A sparsity technique is implemented for the sparse matrices as input data in order to reduce the overall computation time and storage requirements. The performance of the proposed fuzzy load flow method has been tested on the IEEE 14- bus typical system and 362-bus Iraqi National Grid (ING) as a practical system. Results are compared with fast decoupled load flow (FDLF) solution under normal operation conditions. The proposed method is faster (in overall computation time) than the fest decoupled load flow method by about 60 for the same power mismatch accuracy. Two characteristic features of the proposed fuzzy load flow are the on-line applicability for small as well as large-scale power systems in addition to successful solution of normal and contingent power systems especially the case of ill-conditioning by adding series capacitors to certain transmission lines in the system. Also, the fuzzy system has many advantageous features such as optimized system complexity, control of power flow, control of nonlinear system, and its durability to include uncertainty in input data.