Research On Modulation Strategy And Control Based On Virtual Impedance For High Frequency Link Matrix Rectifier

The high-frequency link matrix rectifier has the voltage source and current source,which is generally composed of an LC or L filter,a matrix converter composed of bidirectional switches,a high-frequency transformer,an uncontrolled rectifier,an output filter L or C,and a load.It is a new kind of converter,which has the advantages of energy bidirectional flow,unit power factor,no large-capacity energy storage components,light weight and small size.Therefore,the research of high-frequency link matrix converters has received great attention from all walks of life.The high-frequency link matrix rectifier modulation strategy and control method have become the key to the research.In the modal switching,due to the presence of transformer leakage inductance,different modulation methods will cause different levels of over voltage stress at both ends of the switch.The modulation strategy is compared to achieve the safe commutation of the matrix converter.In the design of the filter,not only the input side unit power factor but also the harmonic interference should be reduced.Therefore,a closed loop control based on virtual impedance is proposed in this paper to eliminate resonance and reduce the THD of the input side current.In this paper,single-phase high-frequency link matrix rectifiers are firstly studied.The voltage and current modulation strategies of unipolar frequency-doubling uncoupled couplings and the switching control methods are introduced.The driving logic diagrams are given,but there is leakage inductance in transformers.The modulation method makes the voltage spike at both ends of the switch tube,and then an integrated unipolar frequency doubling de-re-coupling modulation and phase-shifting de-re-coupling modulation method are proposed,and the respective modulation schematics and driving logic diagrams are given.And the modal analysis is carried out.A safe commutation of the switch tube is achieved,eliminating voltage spikes.Secondly,a new 12-sector division of the input current of the three-phase high-frequency matrix rectifier is performed.The vector action time is calculated and the vector combination sequence is optimized.The switching loss is reduced,the switching time is short,and less switching times and secure commutation of matrix converters are implemented.Then,in this paper,phase-locked analysis based on second-order generalized integrator is performed for single-phase high-frequency link matrix rectifiers,and a double closed-loop control method based on virtual impedance is designed.Then a mathematical model is built for the three-phase current high-frequency link matrix rectifier.A double closed loop based on the virtual impedance of the DC side current outer loop and the network side AC current inner loop was designed.Finally,based on theoretical analysis,this paper designs the hardware circuit and software system,and builds a single-phase platform and a three-phase high-frequency link matrix rectifier platform based on DSP and CPLD combination control.Finally,the experimental results verify the correctness of the proposed modulation strategy.