Studies On Several Problems Of Electrical Power System Digital Simulation

Power system digital simulation is believed as an indispensable tool for power system planning, design, operation, analysis, control etc. The simulation results are normally regarded as authoritative opinions, by which the planning schemes, dispatch plans, control strategies, and equipments performances are evaluated.With the development of power electronics, microprocessors, and microelectronics, new equipments are beginning to emerge. With the restructuring of the electric power industry, new regulating strategies come to front. All these have led to a sharp increase in the need for power system digital simulation software packages to count for these new models. With the development towards an open market and interconnection, the operating condition of transmission systems will be more uncertain, and the physical flows on the system will be harder to control. All these factors drive modern power transmission systems to operate closer and closer to their physical limits and increase the complexity of assessing and controlling the security. Under this circumstance, results of digital simulation are more sensitive to system models and parameters. It is an urgency matter to study the effects of models on simulation results. In this dissertation, studies on user-defined modeling(UDM) and effects of speed variations in generator model on power system transient stability are carried out.UDM has been adopted by several famous power system digital simulation software packages with different implementation methods, such as NETOMAC, TSAT, ETAP, PSASP, etc. In this dissertation, UDM's basic principle, mathematic model and solving method have been deeply studied, and iteration solving scheme of UDM in power flow calculation and transient calculation is also investigated. Take aforementioned software packages as an example, the differences, the advantages and disadvantages of different ones are studied.User system modeling method and interface between main system and user system are two key parts of UDM. At present, user systems are usually sorted to different classes according to their physical attributes, which leads to complex interface. In this dissertation, an equivalent modeling method based on main system status is presented, it treats the effects of UDM on main system network, including structure and parameters, as parallel voltage source and impendence, series voltage source and impendence, or variation of transformer ratio, then change the equivalent voltages, impendences and transformer's ratio variation to injections of corresponding nodes. It allows to calculate UDM without changing main system's Jacobian matrix, which can reduce the complexity of interface largely. A power system digital simulation program with UDM function is developed in MATLAB circumstance, including power flow calculation, transient digital integration and transient stability quantitative analysis.FASTEST is a unique and rigorously quantitative method for transient stability analysis. MATLAB, which is an excellent tool for numerical calculation, modeling and...