Research On Fixed-point Real-time Simulation Algorithms Of High Frequency Power Electronic Circuits Based On FPGA

With the rapid development of power switch in semiconductor industry,the switching frequency of power electronic circuits has been improved rapidly,which puts forward higher requirements for real-time simulation.A more rapid real-time simulation method is needed due to the limited speed of traditional real-time simulation platforms.Starting from the characteristics of field programmable gate array(FPGA)parallel computing,this paper makes an intensive study of establishment of a fast real-time simulation platform for power electronics from three aspects witch are simulation model,numerical algorithm and hardware numerical calculation.Firstly,the discrete iteration process of device model and circuit model is analyzed with the parallel computing time.Based on the analysis of the process of model combination,the method of switching function and combinational logic is used to improve the multi-circuit modal modeling method.Taking Boost circuit and three-phase inverter circuit as examples,the MATLAB program is compiled.And the simulation accuracy of high frequency model is simulated and analyzed by comparing with the reference standard of the small time-step simulation results of the models.Combined with three-phase inverters,the distributed modeling method of decomposition circuit with state variables is described.And the real-time simulation modeling method is determined by analyzing the computing time.Secondly,the discrete iterative algorithm is analyzed.An improved trapezoidal method is proposed,which improves operation speed with computing process by using historical data.On the basis of classification of switching events,the calculation flow of variable-step algorithm in real-time simulation is analyzed.The improved trapezoidal method is applied to the variable-step algorithm using a method of weight value to save the computing resources of the FPGA due to the improved structure of numerical computation.Taking three-phase inverters as an example,the validity of the numerical algorithm is preliminarily verified by comparing the results of off-line simulation with those of simulation software.After that,the computing method of fixed-point number is improved with the advantages of floating-point codes by analyzing the numerical characteristics of power electronic simulation.The order codes are determined according to the physical units and calculated in real time during the simulation process.The problem of small calculation range and low precision of fixed-point number is improved by fine-tuning the order codes in real time.This paper analyzes the specific calculation method of improved fixed-point number,and describes the use of fixed-point number combined with order code in simulation with the simulation calculation flow.Finally,the top-down programming flow of the FPGA is proposed by combining the power electronics modeling method and numerical algorithm.The design idea of real-time simulation platform is described with program structure.A real-time simulation platform based on fixed-point number is built in the development FPGA board.The validity of the method is further proved by comparing with the offline simulation results.The method of building simulation platform is proved by simulating on two kinds of FPGA board from Xilinx and Altera.