Application Of Time-Varying Dynamic Phasor Theory In Analysis Of Electric Power System

As" Generalized Averaging Theory" is widely applied into power electronics analysis recently, it is paid more and more attention. "Time-Varying" Dynamic Phaser Method, which is based on this theory, has been successfully used to analyze dynamics of electric power system brought by FACTS (Flex AC Transmission System). It is well known that there exist much more advantages using this method to analyze dynamics of electric power system than the traditional method does. This paper firstly summarized research achievements that overseas researcher made in this area in past years. According to the classic "Signals and Systems Theory", we compared traditional signals with the Dynamic Phaser signals in details. In order to apply Dynamic Phasor into power system, we put forth some limit condition on it to ensure load flow to be balanced and the theorem KVL, KCL to be true. And more, by introducing errors caused by "Quasi-Stationary" phasor models, it proved that there exist many limitations on "quasi-stationary" phasor models, and Dynamic Phasor models are more advanced and precise.In our paper, we developed Dynamic Phasor models for major elements, which are suitable to simulate on computer. These models can simulate big-disturb dynamics of the large-scale electric power systems. These models are easy to be developed into application programs. All simulation results of these models are compared with ones of EMTP, MATLAB or PSASP. These models offer a number of advantages, when they are used to simulate power system. Firstly, they can be used to not only compute fast electromagnetic transients, but electromechanical transients; The simulation can fast cover course of electromagnetic transients and electromechanical transients in short time. Secondly, the simulation speed is faster than standard time-domain models (such as EMTP models). Thirdly, these models can be used to simulate SSR phenomena.In order to calculate the unbalance faults in electric power system, we developed the Dynamic Phasor models for elements based on three-phase A, B, C frame system. As to network elements, we obtained models with relative high precision, by comparing their simulation results with EMTP's. As to generator's model, we use the Park model, the negative sequence equivalent circuit and zero sequence equivalent circuit to compute the positive sequence, negative sequence and zero sequence values, respectively. Furthermore, we considered phasor dynamics of values of negative sequence and zero sequence. When a balanced fault occurs, this model is accurate model. While an unbalanced fault happens, it is a "Quasi-Accurate" model compared with "EMTP-like" model. These models built on the A, B and C three-phase frame system offer a advantage: they can easily simulate complex faults, and it is unnecessary to transform the three-phase network into positive sequence, negative sequence and zero sequence sub-networks as traditionalelectromechanical transient program does.In order to analyze SSO phenomena caused by HVDC control parameters, we developed Dynamic Phaser model for HVDC system. The methods include eigen-analysis, complex torque scanning. For the sample network studied by us, we get how eigenvalues vary with parameters of control system. Using complex torque scanning method, we analyze the interaction between electrical damping and mechanical damping.Dynamic Phasors can be used to fast calculate electromagnetic transients, and its simulation cover course of electromagnetic transients and electromechanical transients in short time. So, Dynamics Phasors models are can serve as middle models between full-time simulation (Electromagnetic transients) and phasor simulation (Electromechanical transients). Where the simulating speed is required to be fast (for example, Real-Time electric power system simulation), we often use Dynamic Phasor models to take place of traditional "EMTP-Like" models to simulate electromagnetic transients. If, in a relative large network, a local sub-network's electromagnetic transients are required to co...