Study On The Electromechanical And Electromagnetic Transient Hybrid Simulation For Power Systems Based On Socket Techniques

Hybrid simulation technology for power system combines the advantages of both electromechanical and electromagnetic transient simulation. It can also balance the issues of scale, precision and speed of power system numerical simulation, which provides a new approach to study on the stability and dynamic characteristics of large-scale power systems.However, there are still disadvantages belong to existing hybrid simulation algorithms of electromechanical transient and electromagnetic transient of power system. Most of them require fully new electromagnetic transient models of the HVDC or FACTS devices as well as their controllers. Furthermore, a large number of program is essential to achieve data interaction, which always require heavy coding tasks. Eventually, time sequence coordination for the two simulation algorithms is lack of the flexibility and versatility. This thesis tries to put forward a hybrid simulation method based on socket techniques to conquer the obstacles of traditional hybrid simulation methods of power system.Firstly, PSCAD program is used to create flexible alternating current transmission system(FACTS) elements and their controller circuit thanks of the element graphics library in the software, which can conveniently serving accurate simulation of the local network in electromagnetic transient level. At the same time, PSAT toolbox under MATLAB environment is used to simulate large-scale power systems in electromechanical transient level.Secondly, traditional hybrid simulation interface algorithms is improved, mainly concerned with the following three aspects:(1) Three-phase-Thevenin equivalent circuits are used to represent the external electromechanical network model in the electromagnetic transient simulation, while the impact of the internal electromagnetic model on external network is modeled by three sequence power load in the electromechanical transient simulation.(2) A combinative data exchange protocol is presented in this thesis, which introduces parallel data exchange protocol in steady-state operation to enhance speed and serial data exchange protocol in the network topology change to ensure accuracy. Meanwhile, an automatic conversion algorithm of time sequence interaction is designed.(3) Socket technique serves as the communication ―bridge‖ to exchange data between PSCAD and PSAT. Due to socket techniques based on IP/TCP protocol, these two softwares can interact with each other at data level rather than the algorithm level and successfully guarantee the accuracy and reliability of data and control command during communication. This method, with simple interface design and high scalability, can flexibly and efficiently carry out electromechanical transient- electromagnetic transient hybrid simulation.The result of the theoretical analysis is validated by concrete examples of 3-machine-9-node power system with SVC(Static Var Compensator),while the results by the Transient Simulation of PSAT and Electromagnetic Transient simulation of PSCAD are compared at the end of this thesis.