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: Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview 
Chapter Title:  B. Phase Redundancy 
1. Abstract of Cited Paper (BIB001):  This paper presents a new three-level topology based on the neutral-point-clamped converter. The new topology includes a fourth leg that provides fault tolerance to the converter. Furthermore, during normal operation mode, this leg is able to provide a stiff neutral voltage. Consequently, the low- frequency voltage oscillations that appear in the neutral point of the standard three-level topology for some operation conditions no longer exist. As a result, the modulation strategy of the three main legs of the converter does not have to take care of voltage balance, and it can be design to improve the efficiency of the converter. On the other hand, the addition of a fourth leg to the converter produces additional losses. However, in order to eliminate switching losses of this leg, all the power devices commutate under zero-current or zero-voltage transitions. Some simulation results are presented to show viability of this approach under both, normal operation mode and fault event. 
2. Abstract of Cited Paper (BIB002):  This paper presents some modified topologies of the neutral-point-clamped converter. In all of them, the main change consists of adding a fourth leg, which is based on the flying-capacitor converter structure. The aim of this additional leg is to provide the converter with fault tolerance. Furthermore, during normal operation mode, this leg is able to provide a stiff neutral voltage. Consequently, the low-frequency voltage oscillations that appear at the neutral point of the standard three-level topology in some operating conditions no longer exist. As a result, the modulation strategy of the three main legs of the converter does not have to take care of voltage balance, and it can be designed to either achieve optimal output voltage spectra or improve the efficiency of the converter. Simulation and experimental results are presented to show the viability of this approach both under normal operation mode and in the event of faults. 
3. Abstract of Cited Paper (BIB003):  The design, implementation, experimental validation and performances of a fully digital fast power switch failure detection and compensation for fault-tolerant voltage source inverters (VSIs) are discussed. The approach introduced minimises the time interval between the fault occurrence and its diagnosis. The possibility to detect a faulty switch or driver of the VSI in less than 10 µs by using simultaneously a ‘time criterion’ and a ‘voltage criterion’ is demonstrated. In order to attain this short detection time a field programmable gate array (FPGA) is used. The studied fault detection method is implemented using a FPGA and experimentally validated for a three-phase VSI used in shunt active filter case. The proposed method tested first by ‘FPGA in the loop’ prototyping has been also validated through a fully experimental active power filter which confirms the satisfactory performances of the proposed approach. Moreover, the other feature introduced in this approach is that the control scheme and the fault-tolerant scheme are both programmed in only one FPGA. 
4. Abstract of Cited Paper (BIB004):  This paper proposes a fault-tolerant matrix converter with reconfigurable structure and modified switch control schemes, along with a fault diagnosis technique for open-circuited switch failures. The proposed fault recognition method can detect and locate a failed bidirectional switch with voltage error signals dedicated to each switch, based on a direct comparison of the input and the output voltages. Following the fault detection, the designed converter architecture isolates the faulty parts and bypasses the remaining load phase, resulting in a 3 × 2 matrix configuration with six bidirectional switches. Based on the reconfigured hardware topology, novel fault-tolerant modulation strategies are developed to produce three-phase balanced sinusoidal output voltages/currents with only six bidirectional switches, but at a reduced output voltage magnitude as compared with the normal matrix converter. Thus, the developed switching function matrices for the reconfigurable converter structure, containing an appropriate positive- and negative-sequence set of matrices with input voltage vector, can preserve continuous operation even after switch failures and improve reliability of the drives. 
5. Abstract of Cited Paper (BIB005):  This paper describes a new design for a fault tolerant H-bridge dc-dc converter. Fault tolerance is achieved using a multilevel converter topology in combination with a pulsewidth modulation control strategy allowing a large set of converter switching states to produce bidirectional power flows at any required output voltage. For a given converter open-circuit or short-circuit fault, all potential switch combinations are compared in terms of converter losses and output voltage harmonics to identify the most suitable switching combinations to achieve the prefault output voltage level. The fault tolerant ability of the proposed converter to recover the required output voltage is verified by both computer simulations and experimentally using a 1 kW laboratory set. 
6. Abstract of Cited Paper (BIB006):  This paper describes a novel fault-tolerant matrix converter motor drive system which requires an appropriate control strategy and the application of an effective fault detection technique. Two types of fault-tolerant matrix converter, a direct matrix converter and an indirect matrix converter, are proposed for a permanent magnet synchronous motor drive against open-circuit faults in safety-critical applications. A fault-tolerant control strategy is developed in order to maintain the continuous operation of the drive system with satisfactory performance. A high-speed fault detection strategy for detecting and identifying the faulty open-circuited switches located in the fault-tolerant four-phase direct matrix converter is also proposed. Simulation and experimental results are shown to demonstrate the effectiveness of the proposed fault-tolerant matrix converters and the developed fault detection strategy applied to the motor drive system under faulty operating conditions. 
7. Abstract of Cited Paper (BIB007):  This paper presents a diagnosis method for sparse matrix converter according to the fault of any single switch or two switches. The sparse matrix converter is functionally-equivalent to the standard matrix converter but has a reduced number of switches. The proposed diagnosis method is based on the measurement of input and output currents. The currents have respective characteristic according to the location of faulty switches. This method not only detects the switches of open-circuit fault but identifies the location of faulty switching devices without complicated calculation. The simulation results verify that, based on the proposed method, the fault of sparse matrix converter can be easily and fast detected. 
8. Abstract of Cited Paper (BIB008):  Fast fault detection and reconfiguration of power converters is necessary in electrical drives to prevent further damage and to make the continuity of service possible. On the other hand, component minimized converters may provide the benefits of higher reliability and less volume and cost. In this paper, a new fault-tolerant converter topology is studied. This converter has five legs before the fault occurrence, and after fault detection the converter continues to function with four legs. A very fast fault detection and reconfiguration scheme is presented and studied. Simulations and experimental tests are performed to evaluate the structure requirements, the digital reconfigurable controller, and fault detection scheme. For experimental tests, the control and the fault detection and reconfiguration schemes are implemented on a single field-programmable gate array (FPGA) chip. Experimental and simulation results show the effectiveness of the proposed fault-tolerant topology and its FPGA-based control. 
9. Abstract of Cited Paper (BIB009):  In this paper a five phase fault tolerant converter is proposed for permanent magnet (PM) drives. The proposed configuration is an extension of conventional three phase double switch redundant topologies. In contrast to three phase systems, the proposed configuration has more flexibility and reliability regarding simultaneous faults in more than one phase. Different faulty cases are explained. Optimal reconfiguration strategies are derived under several faulty conditions. Design criteria are defined and a comparative loss analysis is conducted on converter behavior under various conditions. Simulation results are included to validate the theory. 
10. Abstract of Cited Paper (BIB010):  In this paper, an FPGA-based fault-tolerant back-to-back converter without redundancy is studied. Before fault occurrence, the fault-tolerant converter operates like a conventional back-to-back six-leg converter, and after the fault, it becomes a five-leg converter. Design, implementation, and experimental verification of an FPGA-based reconfigurable control strategy for this converter are discussed. This reconfigurable control strategy allows the continuous operation of the converter with minimum affection from a fault in one of the semiconductor switches. A very fast detection scheme is used to detect and locate the fault. Implementation of the fault detection and of the fully digital control schemes on a single FPGA is realized, based on a suited methodology for rapid prototyping. FPGA in loop and also experimental tests are carried out, and the results are presented. These results confirm the capability of the proposed reconfigurable control and fault-tolerant structure. 
11. Abstract of Cited Paper (BIB011):  The photovoltaic (PV) technology has a small impact on the environment and is suitable for a wide range of applications. The main barrier for a more extensive implementation has been the reliability, mainly related to the power converters. According to this consideration, this paper presents an open-circuit fault diagnosis and fault-tolerant scheme for a three-level boost converter in a PV power system using batteries as storage devices. The fault diagnostic method takes advantage only of the control variables used for maximum power point tracking and output dc-link capacitor voltage balance. The fault-tolerant strategy requires only a few components added to the original three-level boost converter, so that, under an open-circuit power switch fault, it can be partly reconfigured into a two-level boost converter ensuring battery energy supply. Experimental results verify the proposed fault diagnostic method and reconfiguration for fault-tolerant operation. 
12. Abstract of Cited Paper (BIB012):  This paper proposes a new diagnosis method of an open-switch fault and fault-tolerant control strategy for T-type three-level inverter systems. The location of the faulty switch can be identified by the average of the normalized phase current and the change of the neutral-point voltage. The proposed fault-tolerant strategy is explained by dividing into two cases: the faulty condition of half-bridge switches and neutral-point switches. The performance of the T-type inverter system improves considerably by the proposed fault-tolerant algorithm when a switch fails. The proposed method does not require additional components and complex calculations. Simulation and experimental results verify the feasibility of the proposed fault diagnosis and fault-tolerant control strategy.

Literature Review:
This concept consists of introducing an additional phase leg to replace a faulty phase leg, as shown in Fig. 6 BIB004 . The faulttolerant control scheme is as follows: firstly, the gate driving signals of the two switches in the faulty leg (e.g. S 1 and S 2 ) are set to be zero level; secondly, the suited bidirectional switch is triggered (e.g. t 1 ); finally, the two switches in redundant phase (e.g. S BIB001 and S 8 ) are controlled by gate driving signals to resume the role of the two switches in faulty leg. This method has been applied in three-level converters BIB003 BIB002 . Five-leg BIB009 BIB010 and six-leg converter BIB011 also have similar fault redundancy. BIB005 BIB007 BIB008 , and T-type three-level converter BIB013 , which can handle open-circuit failure of switches. Moreover, researchers also proposed modifications to traditional converters to obtain fault-tolerant ability, such as an improved three-level boost converter for photovoltaic applications BIB012 , an H-bridge DC-DC converter with auxiliary leg and selector cells (HBALSC) BIB006 . A summary of fault-tolerant circuits' performance with respect to power switches failure is presented in Table II . It is worth mentioning that short-circuit failure is more difficult to handle than open circuit, and it usually needs very short detection times.