Trade-off study of heat sink and output filter volume in a GaN HEMT based single phase inverter

This paper presents the trade-off study of heat sink and output filter volume of a GaN HEMT based single phase inverter. The selected topology is three-level Active Neutral point Clamped (ANPC) inverter, and the main aim is to explore the benefits of the GaN HEMTs at 600 V blocking class on the system level efficiency, and power density under wide range of operating conditions. The paper starts by introducing the inverter topology, selected PWM scheme and followed by the device features, static and dynamic characterisation and continues with presenting and discussing the results of extensive experimental and analytical characterisation. After this, the impact of GaN HEMTs on inverter volume is discussed in terms of heat sink and output filter volume analysis under different switching frequency and heat sink temperature conditions. The calculation of heat sink volume and single stage LC output filter volume are presented with respect to experimental results of single phase prototype. The findings from static, dynamic characterisation and single phase prototype results clearly show that GaN HEMT has excellent switching performance under wide load current and heat sink temperature conditions. The high performance of the inverter lead to reduction of the combined total volume, including output filter and heat sink volume

Device loss model of a fully SiC based dual active bridge considering the effect of synchronous rectification and deadtime

It is becoming a great interest to employ SiC based power devices in dual active bridge (DAB) converter as an alternative to conventional Si-IGBT, due to its higher switching frequency potential, smaller switching losses as well as the capability to operate at synchronous rectification (SR) condition. This paper introduces the device loss model of a SiC MOSFET power module based DAB converter considering the effect of synchronous rectification, and the dead-time effect is also discussed. The calculated device loss for both SiC-MOSFET and Si-IGBT are discussed. The results show that the overall device loss is reduced by 40%, where the conduction loss is reduced by 38% because of SR capability of SiC-MOSFET, and the switching loss is reduced by 48% due to the faster transient of SiC-MOSFET during dead-time. On the other hand, the device losses are not even between the primary bridge and the secondary bridge of the DAB converter, and it is more significant for SiC-MOSFET based DAB due to the effect of SR with a maximum of 20%. At last, the dead-time range is given based on the device properties

A physics-based compact model of SiC power MOSFETs

The presented compact model of SiC power MOSFETs is based on a thorough consideration of the physical phenomena which are important for the device characteristics and its electrothermal behavior. The model includes descriptions of the dependence of channel charge and electron mobility on the charge of interface traps and a simple but effective calculation of the voltage-dependent drain resistance. Comparisons with both physical 2-D device simulations and experiments validate the correctness of the modeling approach and the accuracy of the results

Optimization of thermal management and power density of small-scale wind turbine applications using SiC-MOSFETs

This paper presents an optimized design of 12kW 2L-FB inverter for small-scale wind turbine, taking into account some specific behavioral features of SiC power MOSFETs. Power converters used in renewable energy conversion have to deal with intermittent and variable power availability from the source, which implies that they actually work at their maximum rated power for only a small fraction of their operational time. Still, traditional thermal management design of power modules has to refer to maximum load conditions. SiC-MOSFETs exhibit a very stable performance over a broad temperature range [1-3]; this feature enables to design the cooling device for nominal operational conditions, typically corresponding to a much lower than maximum power rating. When this capability is added to the decrease in the size of passive filter elements, which can be gained by the higher switching frequency capability of SiC MOSFETs, the result is a significant increase of the converter powe, density

Single-phase T-type inverter performance benchmark using Si IGBTs, SiC MOSFETs and GaN HEMTs

In this paper, benchmark of Si IGBT, SiC MOSFET and GaN HEMT power switches at 600V class is conducted in single-phase T-type inverter. Gate driver requirements, switching performance, inverter efficiency performance, heat sink volume, output filter volume and dead-time effect for each technology is evaluated. Gate driver study shows that GaN has the lowest gate driver losses above 100kHz and below 100kHz, SiC has lowest gate losses. GaN has the best switching performance among three technologies that allows high efficiency at high frequency applications. GaN based inverter operated at 160kHz switching frequency with 97.3% efficiency at 2.5kW output power. Performance of three device technologies at different temperature, switching frequency and load conditions shows that heat sink volume of the converter can be reduced by 2.5 times by switching from Si to GaN solution at 60°C case temperature, and for SiC and GaN, heat sink volume can be reduced by 2.36 and 4.92 times respectively by increasing heat sink temperature to 100°C. Output filter volume can be reduced by 43% with 24W, 26W and 61W increase in device power loss for GaN, SiC and Si based converters respectively. WBG devices allow reduction of harmonic distortion at output current from 3.5% to 1.5% at 100kHz

Modular plug-in high performance integrated single-phase inverter

The recent research exercises have targeted the transfer of the sandwich package benefits to application bespoke switch design, including flip-chip and device stacking topology [1]. This work presents the development of a highly integrated power switch, based on 70μm thin IGBTs and diodes rated at 600V/200A along with customized connectors to interface quickly the gate driver, the input, and the load side PCBs. This modular system has been designed with the aim to achieve high performance including the modularity and maintainability of power converter that can be worse in a system integrated into a single package

Extracting structure functions of power devices in induction motor drives

This paper proposes the extraction of structure function from power devices on-board induction motor drives. It puts forward the issues and methodology related to on-board measurement of the cooling curve and derivation of the structure function during idle times in induction motor drives for maintenance purposes. The structure function uses the thermal resistances and capacitances in the Cauer form to identify changes in the device structure. The advantage of the structure function is that it does not only reveal the value but also the location of the thermal resistance and capacitance in the heat flow path. The novelty in this work is the methodology used to achieve the measurement of the cooling curve and the derivation of the structure function despite issues related to freewheeling current due to energy stored as a result of motor inductance

Novel multilevel hybrid inverter topology with power scalability

In this paper, a novel multilevel hybrid inverter is presented. The inverter is based on 2 floating capacitors and 16 active switches for five-level voltage waveform between the output of the inverter and neutral point of DC link. The proposed inverter structure, switching states and commutation scheme for different output voltage levels are presented. The proposed topology is simulated and verified experimentally. The simulation results show that proposed topology can achieve higher efficiency in comparison to state-of-the-art hybrid topologies due to reduced conduction and switching losses at low modulation index and light load conditions. Experimental results show that the converter is successfully operated up to 1 kV DC link voltage and 12 kW output power

Prognostic System for Power Modules in Converter Systems Using Structure Function

This paper proposes an on-board methodology for monitoring the health of power converter modules in drive systems, using vector control heating and structure function to check for degradation. It puts forward a system that is used on-board to measure the cooling curve and derive the structure function during idle times for maintenance purposes. The structure function is good tool for tracking the magnitude and location of degradation in power modules. The ability to keep regular track of the actual degradation level of the modules enables the adoption of preventive maintenance, reducing or even eliminating altogether the appearance of failures during operation, significantly improving the availability of the power devices. The novelty in this work is the complete system that is used to achieve degradation monitoring; combining the heating technique and the measurement without additional power components except the measurement circuit which can be integrated into the gate drive board and the challenges encountered. Experimental results obtained from this show that it is possible to implement an on-board health monitoring system in converters which measures the degradation on power modules

Measuring structure functions of power devices in inverters

This paper proposes the measuring of structure function from power devices on-board induction motor drives and multilevel converters. It puts forward the issues and methodology related to on-board measurement of the cooling curve and derivation of the structure function during idle times in induction motor drives for maintenance purposes. The structure function uses the thermal resistances and capacitances in the Cauer form to identify changes in the device structure. The advantage of the structure function is that it does not only reveal the value but also the location of the thermal resistance and capacitance in the heat flow path. The novelty in this work is the methodology used to achieve the measurement of the cooling curve and obtaining the structure function despite issues related to freewheeling current due to energy stored as a result of motor inductance. A detailed description of the measurement circuit is presented. The possibility of applying this technique to multilevel converters in different application is also elaborated