Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> Press-pack IGBT has been developed in recent years as a superior high power IGBT device to conventional IGBT module in reliability and performance. This type of IGBT is replacing GTO or thyristor in such applications as traction, power transmission and industrial motor drive because of its excellent advantages such as high performance, high reliability, compactness due to the both-sided cooling, rupture free feature, and so forth. This paper reviews the performance and structure of 2.5 kV and 4.5 kV press-pack IGBT's and their major applications. <s> BIB001 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> A novel press pack IGBT (PPI) with a rating of up to 4500 V and 2000 A is presented. During the development of this new component, special emphasis was placed on the ease of use by system manufacturers. The mechanical design is optimized in order to facilitate the clamping of the PPI in long stacks. Even if the clamping in the stack has severe pressure nonuniformities, the PPI remains fully functional due to its unique design with individual press-pins for each chip. Furthermore, the choice of materials is optimized to achieve high reliability in the field. The trade-off between power-cycling capability and operation under shorted conditions was a major thrust of the development. The IGBT as well as the diode chip are based on SPT (soft punch through) technology. Together with an advanced planar cell design of the IGBT and the sophisticated lifetime engineering of the diode, this chip set offers an unprecedented safe operating area (SOA). This greatly facilitates system design by making clamps or snubbers obsolete. <s> BIB002 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> The three-level neutral-point-clamped voltage-source converter (NPC VSC) is widely used in high-power medium-voltage applications. The unequal loss distribution among the semiconductors is one major disadvantage of this popular topology. This paper studies the loss distribution problem of the NPC VSC and proposes the active NPC VSC to overcome this drawback. The switch states and commutations of the converter are analyzed. A loss-balancing scheme is introduced, enabling a substantially increased output power and an improved performance at zero speed, compared to the conventional NPC VSC. <s> BIB003 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> Press pack insulated gate bipolar transistor (IGBT) modules connected in series for high-voltage direct current (HVDC) converter applications are designed such that when a failure occurs, it occurs in a safe manner by the formation of a stable short circuit, while redundant modules take up the voltage blocking function of the failed module. One such design using individual pressure contacts is described and the events occurring from the initiation of the short circuit to its final failure due to open circuit are reported from an electronics packaging materials design point of view. Experiments to hasten the failure under accelerated test conditions on modules were performed and interrupted at various stages of operation under a short circuit condition. The formation and subsequent aging of the metallurgical alloy under short circuit conditions was investigated by analyzing cross sections of the alloy forming the short circuit. Liquid metal corrosion along with the formation of intermetallics with poor conductivities lead to the final failure by open circuit <s> BIB004 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> This paper proposes fault tolerant operation strategies for three-level neutral point clamped pulsewidth modulation inverters in high power, safety-critical applications. Likely faults are identified and fault tolerant schemes based on the inherent redundancy of voltage vectors are presented. Simulation verification is performed to show fault handling capabilities. Prototyping and principle investigation are performed on a 150-KW inverter and testing results are presented. <s> BIB005 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> In this paper, a simple method for fault tolerance is proposed for improvement of reliability when the NPC inverter fault occurs in the switching device. The fault of switching device is detected by checking the change of a leg-voltage in NPC inverter. This method has some advantage of fast detection ability and a simple realization for fault detection, compared with conventional methods. Also, reconfiguration is performed by two phases control method which used to supply the balancing three phases voltage to the load continuously. This proposed method help the system minimize the harmful affection to the load caused by a delay of fault detection. The proposed method has been verified by simulation and experiment. <s> BIB006 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> Three-level Diode Clamped Multilevel Inverter, generally known as Neutral-Point-Clamped (NPC) Inverter, has an inherent problem causing Neutral Point (NP) potential variation. Until now, in many literatures NP potential problem has been investigated and lots of solutions have also been proposed. However, in the cases of fault and fault tolerant control state, distinctive feature of NP potential variation was rarely published from the standpoint of reliability. In this paper, NP potential is analytically investigated both normal and fault conditions under carrier based PWM. Subsequently, relation between fault detection time and size of capacitor is analyzed. This information is explored by simulation results, which contribute to enhance the reliability of inverter system. <s> BIB007 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> Compared with traditional three-level neutral-point-clamped converter, the recently proposed three-level active neutral-point-clamped (ANPC) converter can overcome the unequal loss distribution among semiconductor devices, and therefore result in increased output power or switching frequency. In industrial applications, fault tolerance of power electronics converters is very important considering system availability, safety and reliability. This paper presents the fault tolerant ability of three-level ANPC converter. Control schemes are proposed to keep the neutral-point voltage balanced and get stable and continuous output under single device fault for both open-circuit fault and short-circuit fault cases. Simulation results show the effectiveness of the fault tolerant ability of the three-level ANPC inverter under the presented control strategies, which are promising to carry on further experimental validation. <s> BIB008 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> This paper presents a study of the fault tolerance capacity of a neutral-point-clamped converter. Different faults in power semiconductors are considered, and the available postfault states of the converter are shown. In regard of the operation limits, two possible solutions are presented. In these solutions, adding a reduced number of additional components, the behavior of the converter when a switch fails improves considerably. Furthermore, an analysis of the neutral-point voltage balancing conditions after a fault and reconfiguration of the system is also evaluated. Experimental results that prove the correct operation of the proposed topologies are shown. <s> BIB009 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> This paper focuses on fault-tolerant control for a battery-energy-storage system based on a multilevel cascade pulsewidth-modulation (PWM) converter with star configuration. During the occurrence of a single-converter-cell or single-battery-unit fault, the fault-tolerant control enables continuous operation and maintains state-of-charge balancing of the remaining healthy battery units. This enhances both system reliability and availability. A 200-V, 10-kW, 3.6-kW·h laboratory system combining a three-phase cascade PWM converter with nine nickel-metal-hydride battery units is designed, constructed, and tested to verify the validity and effectiveness of the proposed fault-tolerant control. <s> BIB010 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> Reliability is a critical criterion for multi-MW wind turbines, which are being employed with increasing numbers in wind power plants, since they operate under harsh conditions and have high maintenance cost due to their remote locations. In this study, the wind turbine grid-side converter reliability is investigated regarding IGBT lifetime based on junction temperature cycling for the grid-side press-pack IGBT 3L-NPC-VSC, which is a state-of-the art high reliability solution. In order to acquire IGBT junction temperatures for given wind power profiles and to use them in IGBT lifetime prediction, the converter electro-thermal model including electrical, power loss, and dynamical thermal models is developed with the main focus on the thermal modeling regarding converter topology, switch technology, and physical structure. Moreover, these models are simplified for their practical implementation in computation platforms. Finally, the converter lifetimes for wind power profiles are predicted using the IGBT lifetime model available. Hence, the developed electro-thermal model's suitability for the lifetime predictions is shown. <s> BIB011 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> Epoxy molded package and silicone gel module are compared in short-circuit failure mode with respect to critical energy, I2T melting and explosion energy capabilities. The molded technology yields a very low and stable R sc "residual ohmic value" of the dies in low energy short failure which are analyzed through a complete 3D reverse. A continuous thermal cycling test over a short term (duration sc property. These original and not enough known properties are afterwards used for new and original fail-safe X-phase inverter or interleaved chopper. All these proposed topologies use only one paralleled safety leg that is spontaneously connected in series with the faulty devices without any additional complexity or extra cost. Finally, a first lab. set-up provides additional properties during the disconnection of the faulty leg and the automatic connection of the safety leg. <s> BIB012 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> A. Device Redundancy <s> This letter presents a fault detection method for modular multilevel converters which is capable of locating a faulty semiconductor switching device in the circuit. The proposed fault detection method is based on a sliding mode observer (SMO) and a switching model of a half-bridge, the approach taken is to conjecture the location of fault, modify the SMO accordingly and then compare the observed and measured states to verify, or otherwise, the assumption. This technique requires no additional measurement elements and can easily be implemented in a DSP or microcontroller. The operation and robustness of the fault detection technique are confirmed by simulation results for the fault condition of a semiconductor switching device appearing as an open circuit. <s> BIB013
Contrary to modules, press-pack IGBTs intrinsically short after a catastrophic failure, due to the absence of bond wires and direct connection between die and metal contacts BIB002 . This feature can be profitably used for series redundancy, where several devices work as a single-switch. Nowadays it is widely used in traction, high power drives and power transmission systems BIB001 BIB011 . However, for the sake of completeness, it should be pointed out that failed press-pack IGBTs could be open-circuit after some time, due to the interaction of molten aluminum (Al), molybdenum (Mo) and Si leading to various intermetallics, following with poor conductivity as open-circuit BIB004 . Another way is using bypass switches, as shown in Fig. 5 [49]. The bypass switches are located between the neutral point and phase output. Failure occurred in switching devices (e.g. S ap ) can be cleared by blowing fuses (e.g. F a ) through turning on the bypassing switch (e.g. TR a ). The circuit operates as a four-switch three-phase inverter, with lower quality of the output. This topology can also handle open-phase failure in motor drive application, which needs to turn on TR n and change the phase currents to maintain motor's torque constant. This method has been applied in neutral point clamped (NPC) converters BIB005 . Similar solutions are also presented in BIB012 BIB007 BIB006 BIB008 BIB003 BIB009 . The other method with both series redundancy and bypass switches is cascaded H-bridge multilevel (CHBM) converter BIB010  or modular multilevel converter (MMC) BIB013 . When a fault occurs to a switch, the faulty H-bridge (or half H-bridge) cell is bypassed. The output voltage magnitude can be maintained with an increase of harmonic distortion.