You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems 
Chapter Title:  2) MODIFIED POWER CONVERTER 
1. Abstract of Cited Paper (BIB001):  The mutually coupled dual three-phase switched reluctance motor (DTPSRM) is a new type of special 12/8 SRMs, which possesses high-reliability and fault-tolerant feature. In the past researches, the model, analysis, and fault-tolerant operation were mainly focused on the classical single three- and four-phase SRMs. This paper is mainly to analyze and investigate the fault-tolerant performances of a 12/8-pole mutually coupled DTPSRM drive under various open-circuit operations. First, the static magnetic characteristics of DTPSRM with single- and two-phase excitations are calculated by finite-element analysis. Then, the mathematic model of the DTPSRM drive under open-circuit condition is developed with a combination of state and fault functions. The simulation model of the DTPSRM drive system with a fault-tolerant control strategy is established for dynamic analysis. The faulty characteristics and fault-tolerant performances of the DTPSRM with diverse open circuits are predicted. Finally, a 12/8 DTPSRM is prototyped and an experimental setup is built for verification. The experimental normal results and diverse open-circuit operations and self-starting capability under lack of phases are presented, validating the accuracy of the analysis and simulation as well as fault-tolerant characteristics of the DTPSRM drive system. 
2. Abstract of Cited Paper (BIB002):  This publication describes an novel fault tolerant converter for switch reluctance machines. It is proposed to take the advantages of multilevel output converter in the normal operation mode and exploit the switching states that are destructive for the conventional NPC topology and use them for fault tolerance. Moreover, simple and yet effective modulation technique has been found, modified and improved for the specific needs of the converter including the DC bus voltage balancing. The modulation technique has been tested in simulation and the results are presented. 
3. Abstract of Cited Paper (BIB003):  The following paper presents new fault tolerant converter topology for switched reluctance machines, that features multilevel output along with its advantages. The principle of operation in normal as well as in the fault conditions are described. Previously proposed modulation strategy including DC bus voltage balancing scheme is applied and tested in measurements. Low cost, discrete implementation of the NPC asymmetric bridge converter including the measurement results are presented. The measurements prove basic functionality of the new converter topology and at the same time the viability of such a implementation. Furthermore, semiconductor power losses comparison with conventional asymmetric bridge converter is carried out through simulation. The results of power losses analysis show that an converter with multilevel output and inherent fault tolerance does not have to dramatically decrease the overall efficiency. Moreover, power losses distribution show that there is a lot of space for further optimization of the converter. The optimization can be done throughout modifications of the modulation scheme as well as proper component selection. 
4. Abstract of Cited Paper (BIB004):  This paper proposes a novel dual-channel switched reluctance motor (DCSRM) driven by two 3-phase standard inverters. The key of the proposed DCSRM is its two operational models. For the first operational model (Model I), it works like a 3-phase traditional SRM supplied by an H-bridge inverter, which is driven by square-wave currents. For the second operational model (Model II), it can be considered as two mutually coupled SRMs that are supplied by sine-wave currents. These operational models are used to overcome different faults, and the corresponding remedial current strategies are proposed to realize fault-tolerant operation. Then, Model I is adopted for power switch fault. Meanwhile, Model II is employed for open-circuit fault. Moreover, the performances of proposed DCSRM are calculated by a finite element, method and the fault-tolerant performances under different fault conditions are verified by cosimulation. Results show that the proposed DCSRM can be used for safety-critical applications by combining the advantages of traditional SRM and mutually coupled SRM. 
5. Abstract of Cited Paper (BIB005):  In this paper, a novel modular full-bridge converter is proposed for three-phase switched reluctance motors (SRMs), which provides an advanced fault-tolerance solution for both the open- and short-circuit faults in switching devices. The proposed converter is composed of two standard six-pack switch modules, providing great benefits for industrial massive production due to the modular topology. Under normal conditions, bidirectional current excitation is developed in the proposed converter, where all the switching devices are actively involved, which makes full use of the switches and averages the heat dissipation for the heat sink design. When a switch fault occurs, the fault signature can be extracted by detecting the characteristics of phase currents and operation modes, and effective fault-tolerance strategies are further applied to achieve the fault-tolerance operation accordingly. Under switch open-circuit faults, the faulty phase is adjusted to unidirectional current excitation without degrading the motor performance. Under switch short-circuit faults, the motor can still work steadily with a single six-switch inverter module by easily reconstructing the proposed converter, without losing any phase windings. The simulation and experiments on a three-phase 12/8 SRM are carried out to validate the feasibility of the proposed converter and control techniques.

Literature Review:
Redundant switches increase the construction and maintenance cost of SRM drives. Moreover, the original switches are heavily used, while the redundant switches are lightly used. Consequently, the life-spans of switches become different. Considering this point, the modified power converter is developed to achieve fault-tolerant control in BIB006 - BIB003 with the ability to balance the service life of all power switches. As exhibited in Fig. 18 , four solid-state relays (SSRs) K 1 ∼ K 4 are connected to two standard six-pack switch modules for open-and short-circuit fault-tolerant control BIB006 . In the open-circuit fault, four SSRs are kept closed and switch control signals are adjusted to form a closed loop for currents. In short-circuit fault, one of the SSRs will be turned off and five tolerance operation states are analyzed in details. In BIB005 , the SRM has two channels (channel 1 and channel 2), and each channel owns three phase windings namely A 1 , B 1 , C 1 , and A 2 , B 2 , C 2 sharing a common neutral point. On one hand, the power switches open-circuit fault is repaired by regulating drive signals of power transistors. On the other hand, the phase winding open-circuit fault is fixed by injecting three-phase symmetrical sine-wave currents into the healthy channel and two sine-wave currents with opposite phase into the faulty channel. The torque ripple is reduced by this fault-tolerant method. In BIB002 , BIB001 , dual-channel SRM (DCSRM) is proposed whose phase windings are connected to AHB converters independently, providing excellent phase isolation and fault tolerance ability. The SRM is able to continue operating even if three-phase windings in one channel are broken-down. Neutral point clamped AHB converter is investigated in BIB004 , BIB003 , making it possible for the SRM to continue operating after switch open-circuit fault.