Power Devices In Converters Research Articles

On-line junction temperature identification of converter power devices

Abstract Traction converters often fail or age due to long operation hours, complex conditions, and frequent braking, mainly caused by overheating or temperature fluctuations. Monitoring the temperature at the junction of power device is crucial for system reliability. To achieve this, the electric-heat coupling models of IGBT are studied. Models for IGBT’s switching and conduction processes were created using its data sheet, yielding a power loss model linked to junction temperature. A Foster thermal network model for IGBT was then established, deriving the equation for temperature change when losses act as heat sources. Combining these models, an electric-heat coupling model was built on the SIMULINK platform, applied to predict and simulate junction temperature in a two-level inverter, generating a temperature-time image. Finally, an experimental test platform for a two-level SVPWM-modulated inverter was set up, using an infrared sensor to measure IGBT’s steady-state junction temperature. This was compared with simulation results to verify the model’s accuracy.

Thermal Analysis and Junction Temperature Estimation under Different Ambient Temperatures Considering Convection Thermal Coupling between Power Devices

The convection thermal coupling between adjacent power devices in power converters is dependent on the ambient temperature. When the ambient temperature changes, the convection thermal coupling also changes. This results in an inaccurate thermal model that causes errors in the prediction of the thermal distribution and junction temperature based on a fixed ambient temperature for power devices in converters application. To solve this variable-ambient-temperature-related issue, a thermal coupling experiment for semiconductor power devices (the MOSFET and diode) was performed to discuss the influence of the thermal coupling effect between adjacent devices and the FEM (Finite Element Method) thermal models for the power devices considering the convection thermal coupling are established. Through these simulations, the junction temperatures of devices under different ambient temperatures were obtained, and the relationships between the junction temperature and ambient temperatures were established. Moreover, the junction temperatures of power devices under different ambient temperatures were calculated and temperature distributions are analyzed in this paper. This method shows a strong significance and has potential applications for high-efficiency and high-power density converter designs.

A Fault-Tolerant Strategy for Three-Level Flying-Capacitor DC/DC Converter in Spacecraft Power System

With the development of space exploration, high-power and high-voltage power systems are essential for future spacecraft applications. Because of the effects of space radiation such as single event burnout (SEB), the rated voltage of power devices in converters for a spacecraft power system is limited to a level much lower than that for traditional ground applications. Thus, multi-level DC/DC converters are good choices for high-voltage applications in spacecraft. In this paper, a fault-tolerant strategy is proposed for a three-level flying capacitor DC/DC converter to increase the reliability with minimal cost. There is no extra hardware needed for the proposed strategy; the fault tolerance of the converter is only achieved by changing the software control strategy. A stage analysis of the proposed strategy is provided in detail for different fault locations and ratios between the input and output voltage. Finally, a simulation model and prototype are built to verify the effectiveness of the proposed strategy.

Suppression effectiveness research on multi-level EMI filter in thermal electromagnetic interactive filed of explosion-proof three-level NPC converter

As a system, the explosion-proof three-level NPC (Neutral-Point-Clamped) converter has the characteristics of nonlinear, high complexity, and multiple thermal electromagnetic fields, among which multiple magnetic fields interfere with each other and affect the system stability. In order to solve this problem, the conducted electromagnetic interference principle was analyzed in the converter filed firstly in this paper, and transmission paths were illustrated as well. Secondly, on the basis of IGBT (Insulated Gate Bipolar Translator) transient state analysis, the EMI (Electro-Magnetic Interference) mechanism analysis of three-level converter power devices was completed for EMI filter design. Finally, a novel multi-level EMI filter was designed to weaken mutual interference of small magnetic field group in the system and to solve the EMI suppression problem of inner cavity interaction of explosion-proof three-level NPC converter. The research target is to optimize the filter and enhance the system ability of resistance to thermal and electromagnetic interference. The suppression effectiveness of multi-level EMI filter was proved by the experiment conducted on a 1 MW (Million Watt) explosion-proof three-level NPC converter platform.

Fault tolerant ac–dc–ac single-phase to three-phase converter

A fault tolerant system considering a single-phase to three-phase power conversion has been proposed in this work. Two kinds of failures occurring in the converter power devices, open-circuit and short-circuit, can be compensated by the proposed strategy. The fault compensation is achieved by reconfiguring the power converter topology with the help of isolation and connection devices. These devices are used to redefine the post-fault converter topology. A proposed control strategy allows to keep the post-fault topology operating at same power rate of the pre-fault topology. Simulated and experimental results demonstrate the validity of the proposed systems.

Fault-Tolerant Voltage-Fed PWM Inverter AC Motor Drive Systems

This paper shows how to integrate fault compensation strategies into two different types of configurations of induction motor drive systems. The proposed strategies provide compensation for open-circuit and short-circuit failures occurring in the converter power devices. The fault compensation is achieved by reconfiguring the power converter topology with the help of isolating and connecting devices. These devices are used to redefine the post-fault converter topology. This allows for continuous free operation of the drive after isolation of the faulty power switches in the converter. Experimental results demonstrate the validity of the proposed systems.