Research On Modelling And Simulation Of Power System Based On Dynamic Phasor

With the gradual interconnection of large-scale regional power systems and application of electronic devices, the operation and control of power systems are becoming more and more complicated. There is an urgent need for a quick digital simulation technique with accurate models for power system dynamic stability assessment (DSA). This research was motivated by the progressing demand of power system. And the key research on the modelling and hybrid simulation of power system using dynamic phasors wae implemented in this dissertation. The main results of the dissertation are summarized as follows.The dynamic phasor models of basic devices such as conductor, capacitor, three-phase distribution parameter lines and generator are developed in this dissertation. The simulation of practical power systems is implemented with these models. The numerical oscillation of dynamic phasor simulation based on trapezoidal integrator is analyzed. In this dissertation, dynamic phasor method based on the critical damping adjustment (CDA) is developed to eliminate the numerical oscillation caused by the changes of the network configuration.Based on the former research, the dynamic phasor model of three-phase distribution parameter lines is improved in this dissertation. A novel large step size model which takes line loss into consideration is introduced to accelerate simulation speed further. By comparing with EMTP model, it is obvious that the new model can overcome the maximum step size constraint of regular transmission lines and be used to simulate the fast electromagnetic transient phenomena at a higher speed.As for the electronic device, the dissertation developed a new model of Thyristor-controlled reactor (TCR) using dynamic phasor modelling mthod. By truncating the less important higher order terms and keeping the significant ones, the dynamic phasor models of TCR can realistically simulate its nonlinear characteristic with fast speed and high accuracy. The operation of anti-parallel-connected thyristor pair is simulated by switching function which simplified the model deduction. Then based on the TCR dynamic phasor model, static VAR compensator (SVC) and thyristor-controlled series capacitor (TCSC) dynamic phasor models are implemented to valuate the TCR model.A hybrid simulation algorithm based on SVC dynamic phasor model proposed in this dissertation is implemented to effectively accelerate the simulation speed of power system including nonlinear devices. Based on network decomposition method, the external subsystem is represented with conventional quasi-steady state model. And SVC is simulated using DP model and interfaced into conventional transient stability program (TSP) as electromagnetic subsystem. Subsequently, the TSP-DP hybrid simulation of whole system is accomplished.The preliminary research on the hybrid simulation of dynamic phasor and electromagnetic transient program (DP-EMTP) was performed and implemented with the proposed DP models. The key problems during the hybrid simulation are discussed, which including the network equivalent, weighted curve-fitting and phase offset caused by frequency mismatch during the interactions. Case studies on the test systems were performed to assess the performance of the DP models and verify the effectiveness and efficiency of DP-EMTP hybrid simulation. By the comparison and analysis of simulation results, it is obvious that the DP-EMTP hybrid method can be practically used for fast trasnient simulation of power systems.