Study On Fault-Tolerant Control Of Three Phase AC Variable Frequency Drive System

Three-phase AC variable frequency drive system is widely used in industrial, commercial, aviation and other fields for its excellent sports performance and good energy-saving effects. Because the physical model of the system has nonlinear, multi-variable, strong coupling of its own characteristics, precise control of the system is difficult and vulnerable to failure. The system failures are diagnosed fast and accurately.The corresponding fault-tolerant control strategy is of great significance to improve system reliability. In this paper, multi-level inverter drive system for the study on the inverter topology between different parts of the merits of the situation, three-phase inverter-driven control strategy, focuses on the applied multi-level cascade inverter pulse width modulation control technology. When phase-shifting point of view in different ways is used, the system output performance will have different impacts, and mathematical explanation is given to start.In accordance with the three-phase AC variable frequency drive system of the division, parts of the rectifier, DC filter capacitors, the inverter and induction motor , the fault condition may occur are described and, the various parts can be used for fault diagnosis theory in detail. The study based on 9-level inverter cascade system, when the internal switch of the power module failure, all three measures were taken and the system output performance compared. By using of neutral-shift theory, the line output voltage can be re-balanced because of fault isolation device caused .With the level of failure and the power module of failure isolation, being isolated of the failure power switch will be better performance.Theory analysis and simulation on the basis of the cascaded 7-level inverter drive system for the experimental platform, the hardware design and software design is described in detail. And by fault simulation, the correctness of the theoretical study of the feasibility and system design by taking the appropriate technology for fault-tolerant control are verified.