| With the development of microgrids,smart grids and energy internet,large-scale power electronic are incorporated into power system gradually in recent years,which results in that the traditional AC grid develops into an AC/DC hybrid nonlinear system.And traditional electromechanical transient simulation cannot fully reflect the actual dynamic response of the hybrid power system.To address this major issue,electromagnetic transient simulation program(EMTP)based on detailed modeling and small simulation step has become the important power system analysis tools.However,due to the limitation of the simulation step size,simulation speed and scale of traditional EMTP are greatly restrained.Therefore,it is necessary and important to research the fast electromagnetic transient(EMT)simulation method suitable for AC/DC hybrid power system.According to Nyquist sampling theory,a negative correlation exists between the simulation step size of EMT simulation and the frequency of electrical quantity.To increase the simulation efficiency,time-scale-frame transformation(TSFT)is introduced and a novel imaginary part construction method of analytic signal is proposed in this paper.The main feature of TSFT is to construct the analytical signal of single-phase electric quantity and adopt the single-phase dq rotation transformation to reduce fundamental frequency of original signal,which avoid the unbalance drawback for three-phase Park transformation.In terms of the advantages of TSFT,this paper mainly focuses on the application of TSFT method in the modeling and simulation of induction machine and modular multilevel converter(MMC).Induction machines are an indispensable part of the power system loads and have extensive applications in industry and agriculture.Based on the introduction of the EMT models of induction machine that widely employed in various simulation software nowadays,an improved induction machine model,which can enhance numerical stability and simulation efficiency,is put forward in this paper.Then,combined this improved model with TSFT method,the mathematical model of induction machine TSFT model is derived and the corresponding model is programmed in this paper.In addition,the accuracy and effectiveness of induction machine TSFT model are verified through simulation comparison with the classical asynchronous machine model built in Matlab/Simulink.For the limitation of the MMC electromagnetic transient simulation speed and simulation scale,an MMC fast model based on TSFT method is proposed in this paper.To verify the validity and efficiency of the proposed model,the simulation results of MMC time-scale-frame transformation model written on Matlab are compared with that of traditional MMC electromagnetic transient model built in PSCAD/EMTDC under the same conditions.The simulation tests show that the simulation time-consuming of the TSFT model is less than the traditional electromagnetic transient model of MMC without sacrificing necessary accuracy.The simulation analysis of the abovementioned induction machine and MMC shows that the time-scale-frame transformation provides a feasible fast simulation method for electromagnetic transient simulation of AC/DC hybrid power system. |
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