| The development of the power industry changes with each passing day,which makes the application of power electronic equipment more and more extensive,and the resulting harmonic pollution problem of the power system is more serious.The main reason for this problem is the distortion of the current waveform.Vienna rectifier is widely used in uninterruptible power supply,electric vehicle charging pile,new energy power generation and other fields due to its advantages of low harmonic content,high power factor state,relatively small number of power switching devices,low switching voltage stress and high power density.The traditional PI control is difficult to meet the application requirements of Vienna rectifier in some situations with high performance requirements.Therefore,it is very important to improve the control strategy of Vienna rectifier.To sum up,this paper proposes a double closed-loop control strategy of sliding mode-model predictive control for Vienna rectifier.The specific contents are as follows:(1)Compare and analyze the performance of the common topology of the three-phase three-level rectifier and the common control strategy of the Vienna rectifier;The working principle of Vienna rectifier is analyzed,and based on the principle of coordinate transformation,the mathematical models of Vienna rectifier under the abc coordinate system,αβ coordinate system and dq coordinate system are established by the state space method.(2)The double closed-loop control strategy of sliding mode-model prediction is proposed for Vienna rectifier.The sliding mode variable structure control based on variable exponential reaching law is adopted for the voltage outer loop.The error between the given value and the feedback value of DC output voltage is selected as the sliding mode surface.The finite set model predictive control with midpoint potential control was adopted for the current inner loop,and a group of optimal voltage space vectors were obtained by establishing the prediction model,determining the value function and carrying out rolling optimization.The midpoint potential control item was added to the prediction expression of the current inner loop model,and the midpoint potential balance was realized by adjusting the weight coefficient.(3)Complete parameter calculation of components according to the technical requirements of this paper;The sliding mode-model predictive control simulation model of Vienna rectifier is built with MATLAB software.The simulation analysis verifies that the sliding mode-model predictive control of Vienna rectifier can effectively reduce the input current harmonic content,and has advantages in current raptness,system robustness and midpoint potential balance.(4)The hardware circuit and software algorithm of the system are designed,and the experimental prototype of 1.2k W Vienna rectifier with TMS320F28335 as the core is built.Through the analysis of the experimental results,the effectiveness and feasibility of the sliding mod-model predictive control strategy designed in this paper are verified.In conclusion,the topology and working principle of Vienna rectifier are analyzed in this paper.Secondly,the variable exponential reaching law was designed for the outer voltage loop controller,the current prediction model was established for the inner current loop controller,the value function was determined and the rolling optimization was carried out,and the midpoint potential control item was added to realize the midpoint potential balance.Finally,a simulation model and experimental prototype are built for the sliding mode-model predictive control system of Vienna rectifier,and the effectiveness of the sliding mode-model predictive control system of Vienna rectifier is verified through simulation and experimental analysis. |
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