Research Of Hybrid Simulation Interface Model For Wide-Band Equivalents Electromechanical-Electromagnetic Transient

With the large-scale renewable energy access and the wide use of power electronic converters in power systems,the frequency band and dynamic characteristics of power systems have been greatly changed.The random fluctuation of renewable energy,the wide-frequency oscillation and complex interaction of power electronic converter in weak power grid bring unknown and complex transient characteristics and system stability problems to power system.Such a complex large-scale system can not be accurately simulated by the full electromagnetic transient simulation,and the electromechanical transient simulation can not reflect the wide-band characteristics of the whole system.The hybrid real-time simulation makes up for their limitations and solves the constraints between simulation scale,speed and accuracy.It can simulate the stability and transient characteristics of large-scale power system simultaneously in the simulation process.It is an effective research method to analyze the current large-scale renewable energy access to the power system.Because the electromechanical transient simulation can only reflect the power frequency bandwidth of the system,the interface model of the electromechanical side system is mainly based on the fundamental frequency equivalent,and can not reflect the wide-band characteristics of the system,so it is no longer suitable for large-scale renewable energy access power systems.Therefore,it is of great significance and theoretical value to research the interface model which can reflect the broadband characteristics of hybrid simulation system.Firstly,based on the research of electromechanical transient simulation and electromagnetic transient simulation calculation method and mathematical model,the principle and key technology of electromechanical-electromagnetic transient hybrid real-time simulation interface are studied.The main contents are as follows: the method of calculating the equivalent circuit of hybrid simulation interface and its realization process;Hybrid simulation interface data conversion method,hybrid simulation interface data exchange algorithm and time synchronization method.The theoretical analysis and support are provided for the electromechanical-electromagnetic transient hybrid real-time simulation.Secondly,aiming at the problem that the traditional electromechanical-electromagnetic transient hybrid real-time simulation interface model can not reflect the wide-band characteristics of the system,the error mechanism of different hybrid simulation interface models is analyzed,and an interface model based on high-frequency equivalent impedance is proposed.The interface model is based on the Thevenin equivalent circuit in the form of controlled source,and the high frequency equivalent impedance is introduced to reflect the broadband characteristics of the electromechanical side system,which can not only accurately reflect the broadband interaction characteristics of the two sides of the system,but also have no fundamental frequency error.Therefore,it has high simulation accuracy.The high frequency equivalent impedance model is obtained by vector fitting method,and the accuracy of the analysis is verified.Finally,taking the grid-connected photovoltaic system into a single-machine infinite bus system as an example,the transient and dynamic characteristics of the system are simulated and analyzed,and the accuracy of the proposed hybrid simulation interface method is verified by comparing the results of hybrid simulation and all-electromagnetic simulation.Through the simulation analysis of grid-connected inverter system connected to IEEE14 node system,compared with different hybrid simulation interface models,it is verified that the improved frequency equivalent impedance interface model can reflect the wide-band characteristics of the system and has higher simulation accuracy.