Abstract
This paper proposes a fault diagnosis and tolerant control methods for an open-switch fault caused in a three-phase three-level neutral-point-clamped (NPC) pulse-width modulation (PWM) active rectifier. The open-switch fault in the three-level NPC active rectifier causes a distortion in the input phase current and a ripple in the DC-link capacitor voltage. Therefore, proper fault diagnosis and tolerant control methods are required to prevent additional failures and performance degradation in the rectifier system. This paper conducted a detailed analysis of the effect of the single open-switch fault on the NPC PWM active rectifier and proposed a fault diagnosis method utilizing the DC link voltage and the phase angle of the input grid voltage. Furthermore, this paper proposes a fault-tolerant control method to reduce the effect of the open-switch fault by compensating a distorted reference voltage. The effectiveness of the proposed fault diagnosis and tolerant control methods are verified through experimental results.
Highlights
Multilevel converter topologies provide advantages in terms of increasing the allowable DC-link voltage and the better harmonics of the input current in comparison with the conventional two-level converters
Most of the research is related to pulse-width modulation (PWM) techniques for improved performance [1,2,3] and balancing algorithms of the neutral-point voltages [4,5,6,7,8]
Since the three-level neutral-point clamped (NPC) topology has been widely applied to various industries, the system reliability has emerged as an important issue [9]
Summary
Multilevel converter topologies provide advantages in terms of increasing the allowable DC-link voltage and the better harmonics of the input current in comparison with the conventional two-level converters. In three-phase two-level PWM converters, the fault-tolerant control method is proposed through the modification of the PWM switching patterns [13] This method can improve the efficiency and power factor as well as the distortion and imbalance of the grid current under the fault condition. The current distortion is restored, the injected reactive current drops the power factor To overcome this disadvantage, [28] proposes a fault-tolerant control method adding a compensation value to the reference voltages for the outer switches of three-level rectifiers. A fault diagnosis algorithm and tolerant control method for single open-switch faults of three-level NPC active rectifier systems is proposed.
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