Research On Three-phase PWM Rectifier Foraircraft Application And Its Diagnosis And Fault-tolerant Control

Variety-frequency AC power system has broad application prospect in large civil aircrafts, due to its simple and reliable structure, high efficiency and large capacity. Compared with traditional passive rectifier, three-phase PWM rectifier has small harmonic pollution and can achieve unity power factor. However, the use of full-controlled devices results in low reliabilty, which restricts its aircraft application. Therefore, it's important to research three-phase PWM rectifier for aircraft application and its diagnosis and fault-tolerant control schemes.Firstly, the research status and development trend of three-phase PWM rectifier for aircraft application is introduced. Then, the mathematical model of PWM rectifier, double loop control scheme in dq coordinate and SVPWM is introduced, and parameter design of the control loop is given.The effect on working characteristics of rectifier under power switch faults is studied and fault modes are classified. Through analyzing the distortion of three-phase current, a diagnosis method of open-circuit faults based on the current phase angle is proposed. Specific implementation and parameter design methods are given. This diagnosis method can deal with both single and multi switch fault cases, with simple software algorithm, no additonal circuit and strong robustness.Through studying the feasibility of exisiting fault-tolerant schemes, four fault-tolerant topologies suitable for three-phase PWM rectifier is summarized. With analyzing effect on voltage vector under power switch faults, a fault-tolerant algorithm based on modifying PWM mode is studied, which can obviously reduce the distortion of three-phase current and DC voltage ripple without hardware. Finally, a comprehensive evaluation of feasible fault-tolerant schemes is given, from tolerant fault mode, cost, working performance and so on.On the basis of theoretical analysis, a 5k W PWM rectifier prototype with digital control is designed and built. The experimental results shows that the working performance of the system with variety-frequency AC power input meets the design requirement, and the proposed fault diagnosis and fault-tolerant control algrothim is effective.