| The short distance between subway stations and the braking energy generated by the frequent braking of subway trains can be recycled and recovered as the core issue of future subway development research.A large amount of braking power will raise the voltage of the DC traction network and affect the safety of the subway transmission system.At present,it is the most effective way to return the electric energy on the traction network to the AC grid through the feedback converter.The feedback converter operates under high current conditions,usually using multiple power modules in parallel to reduce the current stress of the power device,but the parallel converter will generate a circulating current.The current method for suppressing the parallel converter circulation is numerous.Generally,the DC side voltage stability is considered.When the traction DC power supply has braking power flowing in,the DC voltage oscillation may occur.The current method is not suitable.In view of this,the method for suppressing the circulating current of the multi-module parallel converter The research is carried out,and a loop suppression method based on auto-disturbance control to dynamically change the zero vector action time is proposed.This method can reduce the in terference caused by the traction DC network voltage oscillation to the loop suppression,and is suitable for the feedback parallel converter.Used in complex subway drive systems.Firstly,this paper calculates the capacity of the parallel converter for the regenerative braking energy feedback of the metro with the parameters of Guangzhou Metro Line 5,and determines the parameters of a certain pro duct as the research object;then constructs a mathematical model of the circulation,the model shows the circulation value and the module.The difference between the duty cycles is related.At the same time,in order to reduce the harmonics of the grid-connected current,the modules are staggered and paralleled.Theoretical analysis and simulation verify that the staggered parallel can reduce the harmonics of the grid-connected current but increase the circulation.Then,based on the mathematical model of the circulation,it is analyzed that the outflow and zero vector action time correlation in SVPWM is used.A loop suppression method based on dynamic zero vector PI control is used to dynamically adjust the zero vector action time of SVPWM to realize the c losed loop of the loop.Control and design the control strategy of the external loop control traction network voltage,the inner loop control feedback power and the feedback control parallel current converter with circulation control.The simulation shows that the zero current vector PI control loop suppression method is stable when the traction network voltage is stable.The circulation suppression effect is good,and the sub-modules can be evenly distributed.Finally,the theoretical analysis shows that the regenerative braking ene rgy feedback will bring oscillation to the traction network and bring interference to the circulation control.Therefore,for the inherent defect of poor anti-interference of PI control,this paper proposes an anti-disturbance control based on The circulation control strategy of zero vector action time redistribution,the extended state observer and disturbance compensation energy in the anti-interference controller can compensate the disturbance,increase the anti-interference ability of the system,and adjust the parameters of the dynamic zero vector auto disturbance rejection controller.The tuning method and the stable line are analyzed.Finally,the simulation platform and the low-power simulation experiment platform are verified.The results show tha t under the traction network oscillation,the loop suppression effect of the zero-vector auto-disturbance control is better than the zero-zero vector PI control.Traditional system application under complex conditions... |
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