IGBT Power Losses Research Articles

A Novel Thermal Management Method for Enhancing the Consistency of IGBT Heat Stress in Converter

The reliability of power electronic devices and converters is closely related to thermal stress. However, the research on IGBT heat balance in the converter is still insufficient. To address this problem, a novel thermal management method for enhancing the consistency of IGBT heat stress in a converter is proposed in this paper. A converter-level method based on the bus voltage ringing is utilized for the IGBT junction temperature monitoring. The IGBT power loss can be controlled by modulating the switching frequency, thus IGBT temperature can be adjusted to improve the IGBT thermal consistency of the converter. The validity of the proposed method is verified by experiments with unbalanced load and unbalanced thermal impedance for a three-phase inverter. Besides, the transient process and steady-state performance with asynchronous switching frequency are demonstrated. The method proposed can enhance the thermal consistency effectively and be promising for improving the reliability of the converter with little effect on the performance.

Redundancy Design of Modular DC Solid-State Transformer Based on Reliability and Efficiency Evaluation

The modular DC solid-state transformer (DC-SST) is promising but restricted by limited reliability, which can be solved by redundancy. However, current redundancy designs are only based on the reliability evaluation in stable operation condition and seldom efficiency. In this paper, a redundancy design method of DC-SST is proposed considering both reliability and efficiency. The long-term mission profile and aging of power semiconductor devices (PSDs) and capacitors are considered in the reliability evaluation. Based on the result that the capacitor reliability dominates the system reliability, a simplified system reliability model is proposed. Besides, IGBT power loss considering the long-term mission profile is obtained, which dominates the system power loss. Finally, a multi-objective optimization is solved to obtain the optimal redundant number. Feasibility of the proposed method is verified by a prototype.

Detection of IGBT degradation in NPC inverter based on infrared thermography

Multilevel inverters have been widely applied in high-voltage and high-power applications. Due to the increasing number of the switching devices in multilevel inverter, the probability of fault is increasing simultaneously. The development of reliable systems for fault detection that enable to diag nose a wide range of faults is a motivation of many researchers. In this paper, the theory of IGBT power loss in NPC inverter is introduced and a detecting method of IGBT degradation for diode neutral-point-clamped (NPC) multilevel inverters based on infrared thermography is proposed. Firstly, infrared images of NPC inverter are acquired based on the software FloTHERM and background of the image removed through Otsu’s statistical threshold selection algorithm. Then, the RGB image is turned into a gray image and segmented into small ones. Lastly, hotspots of the image are extracted and an improved detecting method is proposed to diagnose whether the IGBT is in degradation or normal condition. The simulation results prove the feasibility of the proposed method and its advantages in good detecting accuracy.

Lifetime estimation of IGBT modules for MMC-HVDC application

Modular multilevel converters (MMCs) usually work in harsh operating environments due to their compact layouts and adverse mission profiles, which accelerate the thermomechanical fatigue process in insulated-gate bipolar transistor modules (IGBTs). Accurate lifetime estimation is desired to conduct reliability prediction and develop maintenance policies. This paper presents an analytical approach to estimating the lifetimes of IGBTs for MMC-HVDC application based on the thermal cycles, which are influenced by the transmission power profile and ambient temperature profile. The structure and operating principle of MMCs are studied to develop an analytical model for computing the IGBT power loss. A thermal equivalent network in the form of a Foster model is adopted to link the power losses and junction temperature. Next, an RC equivalent circuit analytical method for characterizing the fundamental-frequency thermal cycles, developed using electrothermal analogy theory, is proposed. The rainflow counting algorithm is applied to extract the low-frequency thermal cycles from the annual junction temperature data computed at every minute. The Bayerer model is employed to predict the IGBTs lifetime. Finally, the lifetime distribution, mission profiles and comparison of different IGBTs are analyzed via case studies.

Optimisation of the number of IGBT devices in a series–parallel string

High-power semiconductor switches can be realised by connecting existing devices in series and parallel. The number of devices in series depends on the operating voltage of an application and the individual device voltage rating. For a given application, the use of higher voltage rated IGBTs leads to a fewer number of devices and vice versa. The total power loss of the series string equals to the sum of individual IGBT power losses and total loss increases with the increase in operating frequency. The level of increase in power loss depends on the device characteristics. For high current operation, the minimum number of devices depends on the current rating of individual device. In this paper, series IGBT string of six 1.2kV, four 1.7kV, two 3.3kV and a single 6.5kV IGBTs are simulated for a 4.5kV/100A application and power losses are analysed for different frequencies and duty cycles. This power loss analysis is extended for commercial IGBTs to compare the simulation results. The number of devices for minimum power loss depends on operating frequencies and power savings are significant both at low and high frequencies. In addition to the power losses, the other important issues in optimising the number of IGBTs are described in this paper. When IGBT modules are connected in parallel the principle of derating is applied to obtained reliable operation. This is explained with some examples.

Optimisation of 1000 V Epitaxial IGBT Device for a 2 k W Zero Current Resonant Converter

SummaryThe Use of epitaxial IGBT in ZCOR (Zero Current Quasi Reasonant) Converters needs the optimisation of both the device structure and of the Working Conditions.The most critical issue is the life time of minority carrier in the epitaxial layer which involves a trade-off between static and dynamic performance of the IGBTs.A Correct design of the converter contributes also improving the working condition of the IGBT so reducing the switching losses.This paper investigates methods of reducing IGBT power losses in a ZCQRC and shows how a correctly adjusted lifetime makes a 1000V epitaxial IGBT suitable for operation at high frequency

Influence of age of in vitro matured oocytes and electrical stimulations on the development of cattle nuclear transfer embryos

High-power semiconductor switches can be realised by connecting existing devices in series and parallel. The number of devices in series depends on the operating voltage of an application and the individual device voltage rating. For a given application, the use of higher voltage rated IGBTs leads to a fewer number of devices and vice versa. The total power loss of the series string equals to the sum of individual IGBT power losses and total loss increases with the increase in operating frequency. The level of increase in power loss depends on the device characteristics. For high current operation, the minimum number of devices depends on the current rating of individual device. In this paper, series IGBT string of six 1.2 kV, four 1.7 kV, two 3.3 kV and a single 6.5 kV IGBTs are simulated for a 4.5 kV/100 A application and power losses are analysed for different frequencies and duty cycles. This power loss analysis is extended for commercial IGBTs to compare the simulation results. The number of devices for minimum power loss depends on operating frequencies and power savings are significant both at low and high frequencies. In addition to the power losses, the other important issues in optimising the number of IGBTs are described in this paper. When IGBT modules are connected in parallel the principle of derating is applied to obtained reliable operation. This is explained with some examples.