Study Of Power System Electromagnetic Transient And Electromechanical Transient Real-time Hybrid Simulation

Electromagnetic transient process and electromechanical transient process are two kinds of physical processes with different mathematical models and different time constants. In general, the above procedures are simulated separately. Compared to the electromechanical transient simulation, real-time electromagnetic transient simulation for a large-scale power system is much more difficult considering the shorter evaluation interval and more computation required. With the development of regional power grids'interconnection and HVDC transmission systems as well as the extensive applications of power electronic devices like FACTS and SVC, power grid's scale is extending and its composition is getting more complicated. Thus the interlace of different physical procedures ---electromagnetic transient procedure & electromechanical transient procedure has become the important characteristics of a modern power system. And power system analyses and simulation techniques are facing new challenges. How to integrate the electromechanical transient simulation for a large-scale power system with an electromagnetic transient simulation for a specified part of the system, and further more to synchronize the digital simulation with the real physical process, is a leading subject in recent years. A breakthrough to this subject is of great importance both in theory and reality, for analyzing and studying power system dynamic characteristics as well as enhancing power system stability and reliability. This dissertation's work aims at establishing models and algorithms of hybrid real-time simulation of electromagnetic transients and electromechanical transients, moreover to validate those models and algorithms by applications in complicated large power system analyses. The main contents of the thesis includes: 1) Setting up a parallel computation model for electromagnetic transients, to realize a real-time simulation in comparably small systems by network partition and paralleling computation techniques; 2) Modeling an interactive interface between electromagnetic transient simulation course and electromechanical transient simulation course, to realize a hybrid real-time simulation of electromagnetic transients and electromechanical transients in large-scale power systems; 3) Software development and applications of above models and algorithms in practical power system analyses. An existing network partition and parallel computation methodology ---long transmission line decoupling algorithm is reviewed in detail. Concerning the limitations of this method ---the precondition of long transmission lines existing in an original network to make network partition on, a new network partition and parallel computation method named as node-splitting algorithm is proposed by the author. Applying multi-area Thevenin equivalent theory, the partition is made on the boundary nodes of sub-networks. And associated reduced order equation of network is derived and solved, to realize the network partition and parallel computation, based on the fact that the voltage of the same node should remain the same when being calculated in different sub-networks. The proposed algorithm is characterized by arbitrary partitioning of the original network with no restriction on the boundary nodes. With different precondition in applications, node-splitting algorithm and long transmission line decoupling algorithm are complementary in network partition and parallel computation of electromagnetic transients and achieving computation efficiency and flexibility of parallel simulation., thus to establish foundations of electromagnetic real-time simulation of power grids. In hybrid simulation of electromagnetic transients and electromechanical transients, the calculated power network topology is divided into electromagnetic transient simulation network and electromechanical transient simulation network. The integration is achieved by independent computations of each network and exchanging the required data through the interface at certain time intervals. The modeling and development of interface models have been proposed in this dissertation. When doing electromagnetic transient simulation, the associated mechanical transient simulation network is represented as external Thevenin equivalent circuit. And Norton equivalent circuit is for electromagnetic transient simulation when doing mechanical transient simulation. The interface models for the two networks respectively are actually calculation models of parameters and variables of the external circuits. The data exchange ways are decided through the sequence of parameter modifications. The different sequences are set for calculating parameters and variables of interface circuits at a steady state or a transient state of the system, which are essentially the combination of a parallel connection sequence at steady operation condition and a serial connection sequence during dynamics of network topology change. When the electromechanical transient network including rotating components like generators, the positive resistances and negative resistances of the network are unequal. The symmetric interfaces can not be achieved for electromagnetic transient simulation with asymmetric admittance matrix of the electromechanical network. Corresponding solutions based on the node-splitting method is presented. In hybrid simulation, the transformation between instant data of electromagnetic transients...