MULTI-OBJECTIVE GLOBAL OPTIMISATION FOR THE OPERATIONAL ECONOMICS AND SECURITY OF THE INTERCONNECTED AND LONGITUDINAL SYSTEM

Operation optimisation and security analysis are two important issues in modem power system energy management systems. In the first part of the thesis, an approach for the determination of the most appropriate dispatch solution which best meets the economic, environmental and security objectives in power system has been developed. The implementation of the proposed approach is based on the formation of a bi-criterion objective and a global optimisation technique. The simulated annealing optimisation method has been utilised in the present work. The proposed approach may be run either for evaluation of trade-off curves for post-optimisation treatment of voltage-sensitive security constraints, or for direct inclusion of MW transfer limits as part of the optimisation solution. A fixed power transfer can be incorporated du1ing the optimisation. Consequently, any point on the trade-off curve represents the global or near-global optimum trade-off point. The approach developed has the advantage that it can deal with multiple fuels, multiple pollutants and highly non-linear heat rate functions of thermal generators, the most appropriate fuel allocation can be proposed for various system load demand. These allocation results are very useful in the fuel choosing and planning, especially because how to arrange the fuel type properly in such interconnected level is still a very challenging and confusing problem. In Chapters 8 & 9 of the Part II of the thesis. a methodology has been proposed to identify small-perturbation instability in the critical inter-area modes for the longitudinal interconnected power system Unlike the traditional swing curve technique which is usually unreliable for coherency identification, the approach proposed is based on the examination of mode shapes, and can easily derive insight from mode shapes for nonstate variables P (real power). This methodology is very useful, not only for evaluating the best levels of transfer between subsystems, but also for monitoring different types of security assessments required in the context of generation dispatch. The results have confirmed the validity of two-machine equivalent for the stability assessment of such longitudinal configuration. Based on these, simple expressions are established to represent variations of security levels with the MW transfer between subsystems. These expressions are used to provide security constraints during global optimisation. The effectiveness of the above two approaches proposed in two parts of the thesis respectively has been demonstrated through a 3-area interconnected and longitudinal system. In the last Chapter 10 of this thesis, an eigenvalue-sensitivity check scheduling which runs after the optimisation is proposed to obtaining eigenvalue-sensitivity security optimisation results. The comprehensive derivation of three dimension matrix coefficients is described in detail. Thus the small-perturbation stability program is greatly improved by eigenvalue-sensitivity study. The process of eigenvalue-sensitivity check scheduling is demonstrated by a case study of the longitudinal and interconnected system.

Author dc:creator

• FAN BEI