Research On Performance Optimization Of Three-phase Matrix Isolation Rectifier

The three-phase matrix isolation rectifier(3MIR)is derived from the AC-AC matrix converter.It has the advantages of adjustable power factor,four-quadrant operation,bidirectional energy flow,no large capacity energy storage element,etc.After introducing the high-frequency transformer,the weight and volume of the device are reduced,the output voltage regulation range is increased,and the electrical isolation between the power supply and the load is also realized.Therefore,3MIR has a broad application prospect in the fields of multi-electric aircraft systems,data center front-end power supply systems,electric vehicle charging systems,etc.At present,the research on 3MIR is in the initial stage,and there are some problems such as complex modulation strategy and difficult control technology.To improve the overall performance of the 3MIR system,this paper studies its modulation and control strategy,and the main contents are as follows:Firstly,the topology structure and working principle of 3MIR are introduced,and the expressions of 3MIR AC input current and DC output voltage are derived.The 3MIR topological structure is idealized,and the mathematical models and equivalent circuit diagrams of 3MIR in different coordinate systems are established by Kirchhoff’s law,which laid a theoretical foundation for the subsequent control design.Secondly,the bipolar current space vector modulation(B-C-SVM)strategy of 3MIR is studied.By analyzing the principle and algorithm of the traditional six-sector B-C-SVM modulation strategy,it is found that a large number of narrow pulses are generated during the action of the traditional six-sector B-C-SVM modulation strategy,which can lead to commutation failure and current distortion on the network side.In order to ensure the success of commutation and obtain good current quality on the network side,this paper proposes a narrow-pulse optimized B-C-SVM modulation strategy on the basis of the four-step commutation mode.In this strategy,the traditional six sectors are refined,the switching sequence of the switch tube is optimized and multiple zero vectors are allocated reasonably while keeping fewer switching operation times,therefore,narrow pulse generation is reduced,and the switching tube on-time is ensured to be sufficient to complete the commutation.Then,the control strategy of 3MIR was studied.In order to improve the complex parameter setting and slow system dynamic response of the double closed-loop PI control strategy,to make up for the switching frequency is not fixed and the system calculation of the traditional model predictive control(MPC)strategy.Combining the above two control strategies,this paper proposes a model predictive current control strategy based on the optimal modulation ratio.The PI controller is used in the outer loop to maintain constant output voltage,and model predictive control is used in the inner loop.The inner loop takes the minimum network side current error as the control objective to establish an evaluation function,through which the corresponding optimal modulation ratio is derived,and combines the B-C-SVM modulation strategy to generate the switching state.In this way,the optimization of the traditional MPC strategy can be replaced.While the switching frequency is fixed and the amount of system computation is reduced,the PI parameter setting is simplified and the dynamic response speed of the system is accelerated.Finally,the modulation and control strategies proposed in this paper are verified by Matlab/Simulink simulation software and 3MIR experimental test platform.Simulation and experimental results verify the correctness and effectiveness of the proposed narrow-pulse optimized B-C-SVM modulation strategy and the model predictive current control strategy based on the optimal modulation ratio.