Sharif Digital Repository

Multilevel converters are mainly used in high power applications (usually more than a few hundred kW). It is therefore important that they can continue working under faulty condition. In this paper, a new method is proposed to improve performance of CHB inverter under faulty condition. The proposed method will be compared with existing methods in term of voltage availability. The converter is simulated in Simulink and the results are provided. These results confirm the effectiveness of the proposed scheme, and are in accordance with the theoretical results  

This paper is focused on improving the post-fault performance of cascaded H-bridge multilevel inverters by decreasing the common-mode voltage. First, an algorithm is proposed to determine the optimal post-fault state among all possible states, which have the same maximum available voltage. Furthermore, a modified technique is proposed to calculate the references of inverter phase voltages under faulty conditions. This technique leads to a decrease in the common-mode voltage when the required output voltage is less than its maximum value. These solutions are mutually employed in the post-fault control system. Simulation and experimental results confirm the effectiveness of the proposed... 

Due to several advantages, three-phase Dual Active Bridge (DAB) converter is widely used in numerous applications nowadays. On the other hand, this converter is very vulnerable to Transistor Open-Circuit Fault (TOCF). Therefore, a fault-tolerant (FT) scheme has been proposed in this paper to solve the problem. First, normal and faulty conditions are investigated, and according to the results, a fault-diagnosis (FD) approach is introduced. Using the outcomes of FD unit, a new post-fault strategy is proposed for the converter. The FD method is based on the DC component of transformer phase currents, and the basis of FT technique is shedding the faulty phase. Some benefits of the proposed... 

In This paper, a new post-fault control method for symmetric cascaded H-bridge multilevel inverters (CHB-MLIs) is proposed with the aim of the development of CHB-MLIs performance under faulty conditions due to decrease in common mode voltage (CMV). In other words, this technique addresses the exclusive process to select the optimal post-fault state among all available states possess the same amplitude of the output line to line voltages. As a result, this process leads to provide computed phase voltages references to apply to PWM block. Hence, this technique leads to decrease the common mode voltage and eliminate it under some desired output line-line voltages. Finally, the feasibility of... 

The study reported in this paper deals with the problem of developing a controller with tolerance to current sensor faults. To achieve this goal, two control strategies are considered. In the first method, field oriented control and a developed observer are used in case of no fault. The second approach is concerned with fault tolerant strategy based on an observer for faulty conditions. Current sensors failures are detected and the current will be estimated successfully in order to allow continuous operation of the vector control. Based on the motor model, currents can be estimated using a nonlinear observer. A decoupling current vector control strategy is developed to ensure high...