Research And Application Of General Power Electronic Real-time Simulation Methods

As the development of power electronic techniques,a variety of power electronic devices have become an indispensable part of the modern power systems.They are playing important roles in renewable energy generation,DC transmission/distribution system,microgrid,etc.As an important tool of studying and testing power electronics and power systems,the real time simulation study can remarkably improve design efficiency of protection/control schemes,reduce experimental cost of hardware prototypes,and lower risk of test experiments.However,compared with the real-time simulation of traditional power systems,there are still many problems to be solved in the power electronic real-time simulation.These problems severely limit its applications in researches and projects.The first one is the accuracy problem of the power electronic switch model,which will generate the abnormal power loss under high switch frequencies.The second one is the simulation scale problem of the FPGA(field programmable gate array)-based real-time simulation,which is not only limited by the hardware resources,but also limited by the simulation time-step.This dessertation focuses on these two bottleneck problems and proposes corresponding solutions.A general power electronic real-time simulation platform is developed and real-time simulations of typical topologies,solid-state transformer and microgrids are performed.The detailed research contents are as follows.1)Power electronic switch modeling.Power electronic switches are usually represented by the L/C-equivalent model in the real-time simulation.This model will generate the abnormal power loss under a switch frequency higher than 5k Hz,which severely affects the accuracy of the power electronic real-time simulation.To solve this problem,the response-matching method is proposed for the modeling of power electronic switches.The abnormal power loss problem of the L/C-equivalent model is well solved,and the merit of no need to reform the admittance matrix is reserved.This modeling method has been applied to the real-time simulation of two-level converter,T-type three-level converter,Buck/Boost circuit,etc.2)Real-time simulation under high switching frequencies.A compact nodal analysis method suitable for the FPGA is proposed to achieve smaller time-steps and real-time simulations with higher switching frequencies.This method condenses the simulation loop of the traditional nodal analysis method,thus reduces the execuation time per time-step.This method has been applied to the real-time simulation of a solid-state transformer with a switching frequency of 50 k Hz.3)Microgrid real-time simulation with power electronic switch modeling.The simulation scale of the FPGA-based power electronic real-time simulation is not only limited by the hardware resources,but also limited by the time-step.To solve this problem,the hybrid simulation method based on the latency insertion method and the nodal analysis method is proposed.The real-time simulations of the multiple power electronic devices are parallelized by the latency insertion method.As a result,the simulation scale of the FPGA-based power electronic real-time simulation is no longer limited by the time-step.This hybrid simulation method is applied to the real-time simulation of an AC microgrid with 5 distributed generators.4)Microgrid real-time simulation based on the dynamic phasor model.Dynamic phasor modeling and simulation methods can be adopted in microgrid real-time simulations when the simulation scale is of high priority.A dynamic phasor model based on the multiple frequency shift transformations is proposed to improve the accuracy of dynamic phasor based simulation,and has been applied to the real-time simulation of a hybrid AC/DC microgrid with 12 distributed generators.