Research On Single-Phase Cascade Voltage-Source High-Frequency Link Matrix Rectifier

With the advantages of large passenger capacity,safety and convenience,environmental protection and comfort,electric high-speed train has become an important means of transportation for the vigorous development of all countries around the world.At the same time,with the strong support of the country,it has been listed as one of the top ten key breakthrough development areas of Made in China 2025.At present,the traction power supply system of traditional train mainly adopts the structure of power frequency step-down transformer + AC-DC-AC converter,which has the disadvantages of large volume,heavy weight,low efficiency under light load,single function,easy electromagnetic resonance and so on.Using power electronic traction transformer to replace the traditional power frequency transformer,not only overcomes the shortcomings of the power frequency transformer scheme,retains its characteristics of voltage transformation and electrical isolation,but also effectively improve the carrying capacity of the train,which is one of the key ways to solve the problem of lightweight of electric locomotive,and has become a research hotspot at home and abroad.At present,the mainstream circuit topology in the relevant research of PETT adopts the cascade H-bridge AC/DC + intermediate frequency isolation DC/DC +parallel DC/AC three-level architecture.Although the control is flexible,there are many power conversion stage and the system efficiency is seriously limited.Compared with the cascaded H-bridge structure,the power electronic traction transformer topology based on the cascaded high-frequency link matrix rectifier combines the AC/DC input stage with the DC/DC isolation stage.And one level power conversion is reduced without the addition of power switching devices,which effectively improves the system efficiency and power density.In this paper,the single-phase cascaded HFLMR is taken as the object to carry out research on its reliable modulation strategy and high-performance control strategy,which has important theoretical research significance and engineering application value for promoting the efficient and lightweight development of high-speed rail.The main research contents of this article are as follows:Firstly,the basic working principle of single-phase cascaded HFLMR is analyzed,and the small signal model of single-phase HFLMR module is established by using the state space average method.The influence of each passive parameter on the system performance is analyzed through the zero pole distribution diagram,which provides the theoretical basis for the control system and parameter design.Secondly,based on the de-re-coupling SPWM strategy,the mechanism of voltage spikes generated by HFLMR during matrix converter current commutation is analyzed.And a space vector modulation strategy for suppressing the voltage spikes is proposed.Through a reasonable switch state,the transformer leakage inductance is precharged to ensure the safe and stable commutation of matrix converter.In order to improve the anti-interference ability and dynamic response performance of the single-phase cascaded HFLMR system,and overcome the shortcomings of the conventional PID regulator-based control algorithm that cannot take into account the rapidity and optimization of overshoot,this paper introduces the sliding mode variable structure control strategy and designs the voltage and current double closed-loop sliding mode variable structure controller based on exponential approach law.Finally,the simulation model of single-phase HFLMR and two-module cascaded single-phase HFMLR are established respectively based on MATLAB simulation software.Then the proposed modulation strategy and sliding mode variable structure control strategy based on exponential approach law are simulated and analyzed,respectively.And the simulation results prove its correctness and reliability.