A Research On Fault Tolerant Control For Back-to-back Converter-Fed Induction Motor

With the scale expansion and automaitc level improvement of the power electronic system,the reliability of the system is increasingly improtant.In fact,the power converter is the most fragile component in the power electronic system and its failure can cause great econimic loss and even serious accident.It is necessary to anticipate the fault tolerance ability against unpredicted faults to increase the reliability of the system.Due to some of its advantages such as bidirectional energy-flow,low current harmonics and etc,back-to-back converter is widely applied in industrial production,motor drives and grid-connected power generation.This paper does a comprehensive research on the non-redundant fualt tolerant control for the back-to-back converter fed induction motor system and the details shows as follow.To avoid the complex decoupling control of the post fault system,the “double zero sequence injection” method is widely used for the share-leg fault tolerant scheme.However this method will limit the performance of the system due to its poor DC-bus utilization.For the SPWM based “double zero sequence injection” fault tolerant control algorithm,the al-gorithm theory is analyized and the 3rd harmonic is injected to the modualtion signals to improve its DC-bus utilization.The 3rd harmonic is generated online.For the SVPWM based fault tolerant control algorithm,the conventional algorithm is analyzed and a novel al-gorithm based on the optimized utilization of the active voltage vectors duty time is proposed.The DC-bus voltage utilization is improved and current harmonic is reduced especially when the load is heavy or speed is high.To realize a generalized fault tolerant control which accounts for both healty and different fault conditions,the health leg binary variables that indicate the fault condition of the back-to-back converter is introduced into the SVPWM modualtor.Thus,the fault diagnose,topology reconfiguration and control algorithm reconfiguration will be implemented at a uniform pace automatically and an easy and feasible fault management and tolerance is achieved.The required resource of the micro controller can be reduced.Matlab/Simulink results is presented to support the theory analysis.The experimental result validate the feasibility of the proposed algorithm further.