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Reliability Enhancement and Operation Analysis of Hybrid ANPC Inverters Under Multi Fault Tolerance Control

초록/요약

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.

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목차

CHAPTER 1. INTRODUCTION 1
1.1 BACKGROUND 1
1.2 RESEARCH OBJECTIVES 11
1.2.1 OPERATION PERFORMANCE OF HANPC CONVERTERS 11
1.2.2 SINGLE/MULTI-FAULTS TOLERANT CONTROL FOR THREE LEVEL HANPC INVERTERS 12
1.3 THESIS OUTLINE 13
CHAPTER 2. HANPC INVERTERS MODELLING AND OPERATION UNDER HEALTHY CONDITIONS 14
2.1 PHYSICAL MODEL OF HANPC INVERTERS 14
2.2 HANPC INVERTERS PERFORMANCE UNDER HEALTHY OPERATING CONDITIONS 19
2.3 MODELING AND SIMULATION OF HANPC INVERTERS UNDER HEALTHY OPERATING CONDITIONS 25
CHAPTER 3. OPERATION OF HANPC INVERTERS UNDER FAILURE CONDITIONS 28
3.1 SINGLE OPEN-CIRCUIT FAULTS 28
3.2 SINGLE SHORT-CIRCUIT FAULTS 31
3.3 MULTI OPEN-CIRCUIT AND MULTI SHORT-CIRCUIT FAULTS 33
3.4 MULTI OPEN/SHORT-CIRCUIT FAULTS 36
3.5 FAULTS EFFECTS ON THE VOLTAGE VECTORS 39
CHAPTER 4. PROPOSED FAULT TOELEANT STARTAEGY 41
4.1 DERIVATION OF THE PROPOSED FAULT TOLERANT STRATEGY 41
4.1.1 DERIVATION OF NEW REFERENCES AND OFFSET 41
4.1.2 SELECTION OF NEW VOLTAGE VECTORS 50
4.2 NEW SWITCHING SEQUENCES 52
4.2.1 SINGLE OPEN-CIRCUIT AND SHORT CIRCUIT FAULTS 53
4.2.2 MULTI OPEN-/MULTI SHORT-CIRCUIT FAULTS 58
4.2.3 MULTI OPEN-/SHORT- CIRCUIT FAULTS 60
CHAPTER 5. RESULT AND DISCUSSION 62
5.1 SIMULAUION RESULTS OF APPLYING THE PROPOSED METHOD 62
5.1.1 SINGLE OPEN-CIRCUIT FAULTS 63
5.1.2 SINGLE SHORT-CIRCUIT FAULTS 70
5.1.3 MULTI OPEN-CIRCUIT AND MULTI SHORT-CIRCUIT FAULTS 77
5.1.4 MULTI OPEN/SHORT-CIRCUIT FAULTS 86
5.2 EXPERIMENTAL VERIFICATION 90
5.2.1 EXPERIMENTAL VERIFICATION FOR SINGLE OPEN-CIRCUIT FAULTS 92
5.2.2 EXPERIMENTAL VERIFICATION FOR SINGLE SHORT-CIRCUIT FAULTS 98
5.2.3 EXPERIMENTAL VERIFICATION FOR MULTI OPEN AND MULTI SHORT-CIRCUIT FAULTS 99
5.2.4 EXPERIMENTAL VERIFICATION FOR MULTI OPEN/SHORT-CIRCUIT FAULTS 103
CHAPTER 6. CONCLUSION 107
CHAPTER 7. REFERENCES 110

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