Research On Techniques Of Electromagnetic Transient Simulation On Power System

With the development of power system and advancement of computer technology, numerical simulation, widely used in the system, has been one of the effective tools for the analysis of security and stability. The higher level digital simulation is required to solve the complication of the operation and control because of the network access of power electronic device and new energy, such as High Voltage Direct Current(HVDC), Flexible AC Transmission Systems(FACTS), grid-connected wind farms and solar system.Electromagnetic transient simulation(EMTP) can simulate and analyze the new devices above owing to the accurate calculation to dynamic response the components. In the study, the performance and precision of the trapezoidal integration with damping to numerical oscillation is researched based on the EMTP platform developed by C++. Companion circuit model of synchronous generator for transient simulation is proposed and verified through the comparison to PSCAD.Considering the detailed dynamic response of voltages and currents of component in the network, EMTP simulation is not suitable to the security analysis of large-scaled grid limited by the memory and speed of computer. While transient simulation program(TSP), based on single-phase quasi-steady state models, is ineffective on the transient response and non-linear characteristic inside of power electronic devices and clean energy. EMTP and TSP are combined to hybrid simulation, where the internal elements is researched with EMTP in detail and the external system is calculated by TSP simulation to raise the accuracy and efficiency.EMTP/TSP hybrid simulation interface technology is emphasized in the paper. In the EMTP program, the external network is expressed with 3-phase Thevenin equivalent circuit model, which is simplified through WARD equivalent methods with uniform generator models. The constant power impedance model is adopted for the TSP simulation, which is computed with the EMTP simulation voltage and current results of internal network with improved least squares method and symmetrical component method. The exchange information of equivalent models between the two sub-programs is controlled by serial method through the interface bus. The accuracy of the techniques are verified through comparison of the results obtained from commercial software PSCAD and BPA on the modified IEEE-9 bus system.