Research On Stabilization Control Technology Of Cascaded System Based On DC Bus Voltage Conditioner

In recent years,power electronic cascade system has gained widely attention in academic research and industrial applications.Because of the high bandwidth control characteristics,the constant power negative impedance characteristics of the load side power electronic converters may lead to the oscillation of the DC bus voltage of the cascade system,which seriously affects the stable operation of the system.This article from the stability of electronic cascaded systems perspective,based on the explicit compensation mechanism to improve the dynamic performance and stability of DC bus voltage in cascaded system,a unified compensation index is designed to control effectively the DC bus voltage oscillation control strategy to improve the stability of power electronic cascade system.This paper firstly introduces the stability criteria commonly used in cascaded systems and the development status and main research directions of DC bus voltage stability control technology,and determines the main research contents of this paper.After that,the mathematic model of phase shift full bridge circuit is deduced by the small-signal mathematical model of Buck converter,the required transfer function is obtained,and the closed loop control system of phase shift full bridge circuit is designed.Based on the impedance analysis method proposed by Middlebrook,the more intuitive ESAC criterion is used as the method to analyze the stability of the cascade system,and the root cause of the DC bus voltage oscillation of the power electronic cascade system is discussed.Secondly,the paper studies the stability control strategy of DC bus voltage in power electronic cascade system.A method of parallel DC bus voltage conditioner(DBVC)on DC bus is designed and the DBVC is controlled to AC component of load current source,virtual resistor and virtual capacitor respectively.At the same time,they were also control into a virtual resistor and capacitor by using its active control;As the use of active control will affect the performance of the converter,so the parallel DBVC and active control together to improve the DC bus voltage stability;By studying the topology of cascade system,the integrated DC bus voltage conditioner(IDBVC)is proposed,not only can reduce switch quantity,but slso can effectively improve the power density and reduce the loss.A sensitivity function is established to analyze and compare the inhibitory effects of various control strategies on DC bus voltage oscillation,and the frequency domain analysis of the above control strategy is carried out,combined with the relevant stability criterion to verify its rationality.In this paper,Matlab/Simulink simulation software is used to build a cascade system simulation model.By observing the time domain waveform and its changing trend,and combining the previous theoretical analysis,the designed control strategy is simulated in time domain.The results show that the theoretical analysis is in good agreement with the simulation results,and the control strategy is proved to be accurate and effective.At last,the control strategy of DC bus designed in this paper is verified by experiment,the control system with STM32F407 as the core is designed,and the simulation waveform is verified based on the experimental platform.It is proved that the simulation waveform in the time domain is consistent with the experimental waveform,and the control strategy is effectiveness.