| Motor speed control system is widely used in mine hoists, electric vehicles and other trade, its reliability is directly related to the safe operation of the whole system.But inverter and the drive circuit prone to failure in the system, the reliability problem has not been effectively resolved. The dual three-level inverter has a high output voltage level, various output number and robustness advantages, in this thesis, the dual three-level inverter topology as research object, and the fault tolerant control,neutral point potential balance, dead time compensation, common mode voltage suppression, vector control and other aspects of the system are intensive studied in this thesis.This thesis analyze the topology commutation of dual three-level inverter, Five kinds of output states are summed up according to the different combination of switching devices; solution of space voltage vector expression, drew the space voltage vector diagram; the dead time effect and dead time compensation are discussed, and two kinds of compensation methods of time compensation and voltage compensation are given.; analysis of open winding motor mathematical model and vector control principle, gives the basic vector control block diagram.Aiming at arbitrary switching device open circuit, this thesis proposes a line voltage coordinate system fault tolerant algorithm, the algorithm use of available zero common mode voltage vector without generating zero sequence voltage and the common voltage, analysis of used vector influence of neutral point, by adjusting the balance factor achieve the neutral point balancing. Due to the fault switching device turn-on order do not have the normal operation of symmetry, this thesis change the the switch on rules when fault to meet the requirements of fault tolerant operation. For arbitrary bridge arm failure, a dual three-level inverter common bus fault tolerant topology is adopted in this thesis, in between the motor winding and the DC side of the midpoint connection 6 bidirectional thyristor, when the inverter arbitrary a bridge arm short-circuit or open circuit fault, resection of the bridge arm, the use of 60°coordinate system fault tolerant algorithm in order to the fault-tolerant operation of the system. When the above faults happen, the maximum output voltage of the dual-three level inverter is reduced to half of the normal operation. Through the simulation to verify the line voltage coordinate system fault tolerant algorithm and60° coordinate system fault tolerance algorithm. Simulation results prove thecorrectness of the fault-tolerant algorithm and dead time compensation means, two algorithms are to achieve all right control effect.Aiming at the independent bus topology of the dual three-level inverter, the fault tolerant topology of any side of the inverter is improved, and the system is switched from the normal operation to the fault tolerant operation. Will bidirectional thyristor introducing independent bus topology, arbitrary double arm fault system can still operational derating, and abscission one side inverter method is compared, the method can realize double inverter fault tolerant operation, expanding the range of fault tolerant. Dual three-level inverter independent bus fault tolerant topology can also be applied to a single bridge fault, fault tolerant rated speed to achieve the original rated speed of 3/4, it can be applied to the high speed requirements of the occasion.Experiment of the proposed fault-tolerant control strategy based on dual three level inverter experimental platform. Proved that the fault-tolerant control strategy,the neutral point potential balance, vector control, dead time compensation method,zero common mode voltage suppression method is effective, and has better fault tolerance effect. |
