Vienna Rectifier Analog Synchronous Machine Modeling And Simulation Of Technology

With the popularization of electric vehicles,charging piles are in urgent need of development.In particular,the need for the development of high-power charging piles that can realize fast charging is particularly urgent.Vienna rectifier has a series of advantages such as high power factor,low switching stress,high power density,stable output voltage,low current harmonic content,and a series of advantages.At the same time,it also has good economy and has attracted wide attention.It is gradually applied to the front-stage rectification part of electric vehicle charging piles,but high-power charging and frequent load switching will cause an impact on the grid.Therefore,this article applies virtual synchronous motor control to the Vienna rectifier to achieve high-power unidirectional charging piles to the grid.Friendliness.This article introduces the topological structure and conduction principle of the Vienna rectifier,and on this basis abstracts the mathematical model of the Vienna rectifier based on the three-phase static coordinate system and obtains the mathematical model of the two-phase synchronous rotating coordinate system through Parker transformation.In the modulation strategy,this article adopts the SVPWM modulation strategy,because the level state of the Vienna rectifier is jointly determined by the switching state and the three-phase current polarity.Therefore,the SVPWM modulation of the Vienna rectifier not only involves the judgment of the voltage interval,but also needs to combine the current polarity,and then calculate the vector voltage action time and action sequence to obtain the pulse waveform.The power factor under the control method of double closed loop etc.is stable at 1,or when the power factor is fixed,the positional relationship between the vector voltage and current is fixed,which is convenient to find the corresponding switch state according to the reference vector.However,when the active and reactive power of the VSM changes and the power factor is unstable,the corresponding current polarity between each cell can even be 6 kinds.Therefore,it is necessary to judge the current polarity every time and calculate the corresponding switching sequence to realize the VSM-based Vector modulation.This article has made changes to the modulation method based on variable power factor,which is suitable for VSM control.Then the most common double closed-loop control is applied to the Vienna rectifier,which aims to stabilize the DC side voltage and track the AC current measurement,as well as to achieve high power factor operation.Simulation and comparison with the two-level rectifier show the advantages of the Vienna rectifier more intuitively.However,if the Vienna rectifier is used in the interface part of the electric vehicle charging pile where the load is frequently switched on,it not only needs to ensure the stability of the output voltage and the low harmonic distortion of the current,but also needs to be able to respond to the fluctuation of the grid voltage frequency and improve the interface.The inertia damping can improve the stability of the power grid to a certain extent,and make the power grid friendly to a greater extent while ensuring fast charging.Therefore,this paper also proposes the application of virtual synchronous machine control to the Vienna rectifier to improve the adaptability of the grid to the large-scale access of electric vehicles.The virtual synchronous motor technology simulates the operating characteristics of traditional motors,making power electronic devices more suitable for contemporary power grid structures.However,due to the topology limitation of the Vienna rectifier,only one-way energy can be realized,which is suitable for high-power one-way charging scenarios,and cannot realize V2G(Vehicle-to-grid)application scenarios.The virtual synchronous motor technology to be used in this paper is the product of the virtual synchronous generator technology transferred from the grid side to the load side.New energy grid connection and energy storage applications of virtual synchronous generators require inverters to achieve four-quadrant power control.However,the virtual synchronous motor technology is still applicable when the scene is shifted to high-power unidirectional charging on the load side.By adjusting the amount of active and reactive power absorbed by the rectifier,one frequency regulation and one voltage regulation can be achieved under the condition of unidirectional energy flow.In order to verify the feasibility of the proposed scheme,this paper builds the Vienna rectifier controlled by VSM as the front stage in Simulink,and builds a complete highpower unidirectional charging pile model with the double closed-loop controlled fullbridge resonant LLC circuit as the topological structure of the charging pile..It realizes that the front-stage AC-DC conversion provides a primary adjustment function,provides inertia damping to reduce the impact of frequent switching on and off the power grid,and the rear-stage DC-DC conversion stabilizes the DC bus voltage and provides a guarantee for high-power fast charging.The front and rear levels perform their duties and complement each other to achieve grid-friendly high-power charging.