Study And Application Of High-Power Digital-Analog Hybrid Simulation Interface System

With the fast development of the electric power system,more electric transmission and distribution forms are applied.Such as cross-regional interconnection of large power grids,ultra-high voltage AC/DC hybrid transmission,new energy resources,microgrid technology,applications of various power electronic equipment,new control and protection devices,etc.The characteristics and interaction mechanism of each link in the modern power system have changed deeply,which leads to a single digital simulation or physical simulation can no longer meet its simulation needs.Digital-analog hybrid simulation technology combines real-time digital simulation and physical dynamic simulation to realize their complementary advantages.It is expected to provide an important simulation method for modern power system.The interface system of digital-analog hybrid simulation is the bridge connecting the digital and physical simulation subsystems and is also the key to implement the digital-analog hybrid simulation.This thesis focuses on the high-power broadband interface system of digitalanalog hybrid simulation and conducts research on the stability and accuracy analysis,broadband power interface method and its implementation,and the application of high-power digital-analog hybrid simulation platform in power systems.(1)Aiming at the shortcomings of the existing stability and accuracy analysis of digitalanalog hybrid simulation,a detailed model of the interface system considering the non-ideal factors of the actual interface is established.The Nyquist curve method is used to analyze the stability and evaluate the stability margin of the detailed nonlinear interface system.The Routh criterion method is used to derive the simplified linear interface system's analytical stability conditions,includeing the main non-ideal factors of actual interface system.An improved ideal transformer model interface algorithm considering the simulation ratio and time delay is proposed,and the improvement of stability margin and the applicability to broadband systems are verified by digital-analog hybrid simulation experiments.An accuracy evaluation method based on Hausdorff distance is proposed,and it makes the evaluation result more intuitive and the transient process evaluation more reasonable by quantifying the maximum dissimilarity between the digital-analog hybrid simulation and reference waveforms.(2)To meet the high-power and wide-band requirements of digital-analog hybrid simulation,a high-power broadband power interface method based on the high-power IGBT converter and high-frequency MOSFET converter in series is proposed.It includes the fasttracking control strategies of the main frequency and high-frequency power interfaces based on the PIQR controller,the fast component detection method capable of accurately separating the main frequency and high-frequency components of reference signals,and the broadband phase compensation method capable of improving the phase accuracy of each frequency component in a wide-band.The broadband output voltage accuracy,good dynamic tracking performance,and stability and accuracy in the digital-analog hybrid simulation system simulation of the proposed power interface have been verified by simulations,which lays a certain basis for the realization of the power interface and its digital-analog hybrid simulation interface system.(3)Aiming at the implementation of high-power broadband interface system of digitalanalog hybrid simulation,the high-power IGBT modules and the MOSFET-based programmable power supply are used to realize the main frequency power interface and highfrequency power interface,respectively,and a high-power broadband interface system is further constructed.The linear phase compensation algorithms are implemented in both the main frequency and high-frequency power interfaces to improve the phase tracking accuracy in a wider frequency band.The stability,accuracy,and dynamic response performance of the main frequency power interface,the high frequency power interface,and the constructed high-power broadband interface system have been verified through comparative experiments.The two application scenarios of railway traction power supply system and ground-current active suppression device testing are selected,and the digital-analog hybrid simulation application experiments have been carried out.The results show that the interface system has a wider frequency band than the existing fundamental wave-based simulation system and can be applied to simulation and testing occasions containing a variety of controllable voltage sources and harmonic source conditions.(4)Aiming at the application of high-power digital-analog hybrid simulation platform in power systems,a 400 V/500 k VA digital-analog hybrid simulation platform is constructed.Based on the platform,the case application of power system fault recurrence is carried out,and the stability and accuracy of the platform are further verified by comparing the digital-analog hybrid simulation results with the field fault recording and using the proposed accuracy index to evaluate the accuracy.The system-level testing case of static var generator(SVG)is selected,and the SVG input voltage range,unbalanced load compensation,and short-circuit fault compensation tests are carried out to verify the corresponding functions and performance of the SVG under test.The low-voltage ride through(LVRT)standard testing case of photovoltaic inverters is selected,and the LVRT tests with different phases and different voltage drop amplitudes are conducted.The results show that the inverter under test meets the corresponding LVRT standards.These application studies show that the platform can be used for complex power system simulation analysis,equipment system-level testing,and voltage standard testing,etc.,which provides a foundation for the further promotion and application of digital-analog hybrid simulation technology.