Synthetical Control Strategy Research In Dual-PWM Rectifier-inverter System

AC frequency conversion speed regulation device is the core of modern industrial automation production,and the performance of it will directly influence the quality and yield of product.Combining with modern auto control system,developing a high-performance vector control system for dual-PWM frequency control mainly reflects in three aspects.It needs to reduce the pollution system for grid,ensure the unit power factor rectifier side operation and reduce the net side current harmonic in the grid side;AC motor in the load side requires high speed control precision,fast dynamic and static response and low torque pulse vibration;The device itself should improve the efficiency of system,suppress DC bus voltage fluctuation to promote energy conversion on both sides.The object of this paper is three-phase two-level four-quadrant dual-PWM.The design of virtual flux control in rectifier side,non-speed sensor control in inverter side and new cooperative control scheme in both sides are introduced after analyzing the traditional double current closed loop control,direct power control,direct torque control and other normal algorithms.The schemes mentioned above are meticulously discussed in three aspects—method analysis,simulation and experiment,based on the analysis of dual-PWM frequency control model.The main work of this paper is:1)Virtual flux direct power control based adaptive sliding mode observation is provided in PWM rectifier.At the beginning,considering that the ideal flux is completely orthogonal with virtual flux,a new control law for virtual flux compensation is designed,which can improve the dynamic performance of rectifier side via improving virtual flux observer to track the flux change caused by voltage fluctuation in grid side with high accuracy.Compared this method with traditional saturation suppression method,first order low pass filter and integral observation method,the validity of improved observation is proved.Aiming at the voltage estimation procedure,sliding mode observation is firstly introduced into the flux observer in PWM rectifier,which can chose proper switch function to estimate grid side voltage and obtain virtual flux and vector phase angle by combining adaptive controller in the above design.2)In the research and application of speed sensorless control algorithm an adaptive siding mode speed sensorless control algorithm based on auto disturbance rejection controller(ADRC)is proposed.The speed sensorless method based on rotor flux orientation is studied,a new hyperbolic tangent switch function is introduced based on traditional sliding mode observer to design the adaptive law for rotor position and rotor speed estimation,and the stability of them is analyzed;considering that the rotor speed will be affected by stator resistance,Lyapunov function is applied to identify stator resistance online.To ensure the identification accuracy under dynamic response and reduce the deviation in steady state,the expanded state observer is adopted to realize the linearization for system dynamic compensation,and an ADRC with speed loop and current loop is established as well.The dynamic response performance and the speed estimation accuracy of traditional sliding mode control and the improved one is compared in the simulation part and verified in the experiment part by using electric vehicle as objective3)As for the research in dual-PWM coordinated control,in order to solve the problem of bus voltage fluctuation during power changing,a power balance model for dual-PWM rectifier-inverter system is established based on DTC in both rectifier and inverter side,and then a full response power compensation algorithm is provided for dynamic and steady compensation,which is compared to the traditional PI loop by simulation and experiment;model prediction control in both rectifier side and inverter side is studied combing with dual-side independent control,including first step prediction and second step prediction;based on the power balance in system level,the current outer loop control under dual-side model prediction control is effectively improved and a dual-PWM coordinated control based on system level power balance and model prediction control is provided.The experiment for stability analysis under parameter perturbation is implemented,and the result of it is compared with traditional PI control algorithm,traditional model prediction control algorithm and inverter side power feedback model prediction control algorithm.4)Dual-PWM frequency control experiment platform based on double DSP processor is established,which is used to the control circuit design and software design,and complete related experimental verification of the algorithm.