Study On Active Damping Control Of The Two-stage Matrix Converter

The matrix converter eliminates the dc side energy storage link of the traditional ac-dc-ac converter,and has advantages of good input-output performance,high power density,wide output frequency range and four-quadrant operation with motor load.The two-stage matrix converter is developed from the topology of matrix converter,and the separation between rectifying modulation and inverting modulation is realized by using the dc bus.Compared with the direct matrix converter,it has advantages of simple modulation strategy,no need for complex converter mode,and its inverting topology can be optimized according to the load.In this dissertation,based on the topology structure of two-stage matrix converter,the active damping algorithm based on different modulation and control is studied.This dissertation first introduces the topological structure of the two-stage matrix converter,then builds a mathematical model of the two-stage matrix converter,studies its switching function matrix,and analyzes the relationship between its input and output variables and the switching function matrix.The rectifier modulation,inverter modulation and two stage coordinated control are studied in this dissertation.The experimental prototype of the two-stage matrix converter is built.Under the double space vector modulation strategy,the grid current harmonic content of the two-stage matrix converter is large.In this dissertation,the input side filter is modeled mathematically,and the filtering effect of the input side filter is analyzed under the damping resistance and the traditional active damping.The existing active damping algorithm has no obvious effect on fifth and seventh harmonics suppression.In this dissertation,the fifth and seventh harmonic signals in the network side current are detected by using the quasi-resonance controller to amplify the harmonics of a specific number of times,and the signals are fed back to the active damping algorithm,so as to optimize the active damping algorithm and suppress the fifth and seventh harmonics in the network side current.Simulation and experiment verify the effectiveness of the algorithm.The current waveform distortion of the two-stage matrix converter is serious under the model predictive control.In this dissertation,the predictive control model is constructed,its switching state is selected by rolling optimization of value function,and its current harmonic characteristics are optimized by active damping algorithm.Aiming at the problem that the active damping algorithm can't improve the current characteristics of the network side greatly,this dissertation analyzes the mechanism of the model predictive control,and points out that the single vector action of the rectifying stage in each sampling period is the reason for the current characteristics of the network side to become worse.Under the current modulation model predictive control method,active damping can not be used in the two-stage matrix converter to suppress the network side current harmonics.In this dissertation,the modulation model predictive control algorithm is improved,and the input side current space vector is fine-tuned by zero vector and modulation system.Based on this,the active damping algorithm is applied to the modulation model prediction,and the network side current is optimized.Simulation and experiments verify the effectiveness of the improved model predictive control and active damping algorithm.There are 46 pictures,7 tables and 71 references in this dissertation.