Application Of Dynamic Phasor Theory In Simulation Of Modern Power Systems

With the power system interconnection and application of various power electronic devices, such as FACTS devices and HVDC, modern power systems are becoming more and more huge and complicated. Traditional technology for modeling and simulation is no longer appropriate. How to describe the power electronic devices with simple but accurate models? When simulating a large-scale power system including quick transients, how to solve the conflict between precision and speed using single electromagnetic transient simulation and electromechanical transient simulation? All these are the key problems in researching on digital simulation of modern power systems.The emphasis of this dissertation is put on the study of modeling and simulation method for modern power systems including power electronic devices.The dynamic phasor theory, which is based on time-varying Fourier coefficient series, is applied to modeling and simulation of power electronic devices. Combined with switching functions, dynamic phasor method can be used to build the general and continuous model for power electronic devices. In this dissertation, the dynamic models for a 3-level STATCOM, a UPFC, and a HVDC system with dynamic phasor method are presented. Computer simulation results verified the accuracy and efficiency of the dynamic phasor models. Dynamic phasor model can be viewed as an intermediate between quasi-steady static model and detailed electromagnetic transient model, which can describe the original system accurately and improve the simulation speed. It can fill the gap between the simplified and detailed models.Hybrid simulation based on dynamic phasor simulation and electromechanical transient simulation is implemented. The power system can be divided into two parts. One is described with dynamic phasor model and the other is described with electromechanical transient model. With the alternate iterative method, the dynamic phasor model can be interfaced with the transient stability program easily. During the iterative, the different simulation time steps can be chosen in the dynamic phasor simulation and the electromechanical transient simulation. This hybrid simulation approach can take account of both precision and speed, which fits for large-scale modern power systems.This dissertation also relates to a lab experimental system, which is tried to model a small-scale power transmission system including a 3-level STATCOM. An improved SVPWM control strategy is presented and implemented to balance the voltages on the two DC capacitors of the NPC 3-level converter.