The Research And Design Of High-frequency Link Matrix Rectifier

High-Frequency Link Matrix Rectifier(HFLMR)is a new topology structure evolved from three-phase matrix converter.It`s generally composed of five parts: input filter,bidirectional switching matrix,high frequency transformer,rectifier and output filter.The topology has the advantages of high energy density,small size,standard sine of input current,unit power factor and so on,because there is no large capacity energy storage element and high frequency transformer in series.It has a certain application value in the occasions with high demand for weight,volume,efficiency and isolation between input and output.The design and optimization of modulation strategy and control strategy is an important part of this topology research,so the design and implementation of the converter will be deeply studied from these two perspectives in this paper.Firstly,the basic principle of the topology is analyzed,and it is proved that the topology has the ability of standard sine of input current and stable output voltage.In this paper,the most common bipolar current space vector modulation strategy is chosen as the focus.Choice of vector and synthetic process are described in detail and by comparing the clear vector synthesis of temporal sequence,the number of period,and sector division will affect the performance of the converter,main performance in the output current ripple,input current harmonic content and stability of working and so on,further illustrate the importance of modulation strategy and the optimization direction of this.Then,an improved current space vector modulation strategy is proposed to solve the problems of strong common-mode interference,large DC ripple and high voltage stress of switch tube existing in traditional modulation strategy.In this modulation strategy,a new duty cycle calculation formula is established by redesigning the vector sector,and the adjacent effective vectors are selected as the basic vectors to synthesize the reference current vector.The proposed improved modulation strategy not only reduces the common-mode voltage to 50%and the diode voltage stress to 86%,but also effectively restrains the current ripple.Then,model predictive control(MPC)is introduced to solve the problems such as weak anti-interference ability,low input power factor and long adjustment time.Firstly,we build the dq mathematical model of the topology and build prediction ring of input current by discretization.We design a model predictive control system based on space vector synthesis to control the power factor and output voltage.And ultimately achieve stable output voltage waveform,fast dynamic response,regulating time and overshoot volume reduced to 45% and63% respectively and keep working with unit power factor.When the input three-phase electric non-equilibrium,output waveform is stable.Finally,the simulation model and prototype are built to verify the feasibility and correctness of the above strategies.