Advanced Modeling of Electromagnetic Transients in Power Systems

Simulation of fast and slow dynamic behavior of electrical power systems is needed for many industrial applications. The results influence the development of electrical and mechanical components and the design of control elements in power systems. Examples are Mechanical stresses on network elements Control systems of turbines and generators Settings of protective relays Transient stability of power systems Important phenomena to be simulated are i.e. synchronous stability, machine dynamics, subsynchronous resonance, influence of load variations, switching and lightning overvoltages, and saturation effects. The conventional and functional grouping of simulation tools into power flow-, short circuitand dynamic calculations was necessary in the past for computation reasons. Traditional simulation tools are especially designed for each application, seperated by the different time constant of interest. Power flow calculations are needed for stability investigations in electrical power systems. Simulation tools like PSS/E and Simpow, [10, 11] are able to compute the long term dynamics. In order to calculate fast transients caused by switching and lightning, etc. detailled models of the network components are needed (realized i.e. in EMTP, EMTDC, Netomac, etc. [7, 8, 9]) The numerical schemes implemented are based on [4] and discussed in detail in [5]. Drawbacks have been identified and compared to a pure state space representation. The effizient object-oriented hierarchical modelling language Modelica enables the graphical definition of complex networks. The used components are defined by their differential algebraic equations (DAE). Simulation tools [1] transform the overall differential algebraic system to a state space representation. The individual components are depending on the application (time constraints) and can be variied in compexity. The component interfaces are kept equal, which enables an easy exchange of simple to complex components. This concept enables the simulation of electrical, mechanical and control application and combines power flow-, short circuitand dynamic calculations within one simulation environment.