Laith M. Halabi, "Reliability Enhancement and Operation Analysis of Hybrid ANPC Inverters Under Multi Fault Tolerance Control," 아주대학교 공학박사 학위 논문, 2022. > Paper

Renewable energy (RE) has adopted a decent position in renewable energy filed. Many renewable energy stations have been established around 

the world, among these stations, one of the most important parts of any power system is the electric inverter/rectifier. Whereas power converters 

are prepared to operate continuously throughout the lifetime of the power generation system. Meanwhile, the operational performance is opposed 

to failure due different open/short circuit faults at the switching devices level which would highly affect the reliability and stability of the system. 

The faults could occur as single open-circuit, single short-circuit faults, multi open-circuit faults, multi short-circuit faults or mix of open/short 

circuit faults at the switching devices level.

Among all kinds of switches faults, the failure of an open-circuit have the chance to be more repetitive. On contrast, short-circuit failures are 

regarded as less common but more harmful to the system components and operation. Nevertheless, multiple kinds of faults at same time sharply 

reduce the reliability of the system and led to series of effects that reduce the stability of other components of the whole power system. In these 

regards, to maintain the reliability and stability of the system, an accurate and precise fault tolerant that can operate the system normally under the 

different kinds of component failures. The space vector modulation (SVM) technique is one of the best control schemes used in power generation 

and conversion due to its high capability of working over higher modulation index with better performance compared to other methods. However, 

the normal SVM without improvements is unable to operates during the failure of any part of the system components due to any kind of switches 

fault (open or/and short). In these regards, this work develops an improved SVM control scheme that can operate the system normally and safely 

under different failure conditions. This works performed a new and improved method that can tolerate the extreme fault cases in three-level hybrid 

active neutral point converters (HANPCs). This includes the new generation of voltage references, new voltage offset, and switching sequences 

for all faulty cases that would occur in HANPC converters.

The proposed fault tolerant control strategy is illustrated in deep details in order to highlight the influence of the improved SVM modulation 

technique under the faulty switching devices conditions. This includes the obtaining of the normal operation under the faulty conditions, improving 

the total harmonic distortion (THD) and operating the system normally under the different single/multi failures at any of the switching devices. 

Among the proposed control strategy, there is no need to make any changes on the basic topology of the system or inserting any external devices 

to the inverter circuit. Additionally, a descriptive analysis of the operational performance of the system under the healthy and faulty conditions is 

carried out in deep details. The simulation and experimental results are obtained to confirm the effectiveness of the proposed fault tolerant strategy 

in effectively maintaining normal and safe working behavior over different kinds of the devices failure single and multiple faults without alternating 

the topology configuration. In addition, the results confirm the effectiveness in reducing the voltage stress on all switching devices to withstand 

low voltage level under the faulty conditions. The outcomes of this work can be regarded as a general framework for future works that need higher 

stability in different industrial applications, besides it can be used among the well know topology such as three-level neutral point clamped (NPC) 

and T-type topologies and further for new topologies with different output voltage levels.