Power Electronics Europe February/March 2022

16 APEC 2022 www.apec-conf.org/ Issue 1 2022 Power Electronics Europe www.power-mag.com industry and in the way that we do the roadmapping. Along with increased participation from the community, our methodology has adapted to the times to stay relevant, with an aim to provide wide ranging perspectives to the growth and evolution of power conversion technology. In this talk, we will walk down memory lane and track the evolution of the PSMA PTR –from a single, in-person, roundtable event in the early years to a multidimensional, multimedia, multiyear activity to track key trends across a broad variety of power conversion markets. See how the community anticipated industry trends such as efficiency, digital control and the shift from Silicon to wide bandgap materials. And revisit what we got wrong. The PTR will continue to evolve. The last keynote covers “Inverters for the Future Grid – Challenges and Opportunities” , to be presented by Professor Deepakraj Divan, GRA Eminent Scholar, and Director, GT Center for Distributed Energy, ECE Georgia Institute of Technology. Hundreds of gigawatts of PV solar, wind and storage are being deployed globally on the grid every year. Over the next 5-10 years, millions of geo-dispersed inverters will replace the rotating synchronous generators that are the heart of today’s grid. These inverters will have to work together collectively and autonomously to also form and sustain the grid as an ecosystem and will have to do so without causing stability issues or interacting with each other or with other grid elements. This will require new hardware, software and control principles. It will also drive the industry towards multiport power converters that are flexible, modular and scalable, and which can simultaneously and safely interface with PV solar, batteries, generators and loads, managing power flows between various sources/loads and ensuring stable operation under normal, transient and fault conditions. Fast-moving technologies, lagging standards, diverse communications protocols, cybersecurity issues, hundreds inverter vendors, and hundreds of grid codes to comply with, pose a very challenging set of issues – but they need to be solved soon. Availability of a next generation inverter for the future grid can be a key factor in addressing climate change and saving the only planet that we have. After the keynotes the exhibition covering all major names will be opened. Example session Most of the sessions checked in the extensive program reveal that the majority come from academics with a high portion of Chinese authors, illustrating that the region far east has already catched up in power electronics technology. As an example I have selected the session “T04 GaN/Silicon/Passive Devices” on the Tuesday morning with its abstracts. The first paper “Overvoltage Ruggedness and Dynamic Breakdown Voltage of P-Gate GaN HEMTs in High-Frequency Switching Up to Megahertz” will be presented by Ruizhe Zhang from Virginia Polytechnic Institute and State University, Blacksburg/USA. This work developed a testbed for high-voltage GaN HEMTs enabling continuous overvoltage testing up to 1- MHz switching frequency. Two types of 600/650-V commercial p-gate GaN HEMTs were tested under overvoltage at an switching frequency up to 0.2-1 MHz. The Gate Injection Transistor showed a nearly frequency-independent dynamic BV, while the Schottky-type p-gate GaN HEMT showed a decreasing BV at higher, e.g., 120-V lower when Fsw increases from 2 kHz to 200 kHz. The behaviors were explained by the buffer trapping/de-trapping in two types of GaN HEMTs. This work unveils the true overvoltage margin of GaN HEMTs in high-frequency converters. “Short-Circuit Protection for GaN Power Devices with Integrated Current Limiter and Commercial Gate Driver” is the subject of Davide Bisi, Member of Technical Staff at Transphorm Inc., Goleta, California/USA. He will demonstrate a short-circuit protection technology for GaN power devices paired with a commercial gate driver. The GaN power devices are equipped with integrated Short-Circuit Current Limiter (SCCL) to achieve a sufficiently long short-circuit withstanding time of 1.2 ?s at 400 V with a relatively small penalty in on-resistance (+0.2x). The gate-driver is equipped with desaturation detection (DESAT) and soft shutdown circuitry to achieve a fast protection response (less than 600 ns) with high noise immunity (tested up to 70 V/ns). The combination of GaN power devices with SCCL and a commercial gate driver with fast DESAT and high noise immunity allows short-circuit protection and fail-safe operation of GaN power electronics for additional robustness in motor drive applications. “Thermal Design Considerations for GaN-Based Power Adapters with Multi-Heat Sources” are analyzed by Rahil Samani, University of Calgary/Canada. GaN transistors have paved the way to enable high power density and high efficiency in AC adapters. As power density increases and size reduces, more attention to thermal management across the components inside the adapter increases. This paper presents some general design rules for the thermal management of GaN-based AC adapters. Moreover, a mutual thermal resistance study is conducted to isolate the impact of heat sources on GaN. This enables the designers to prioritize the thermal optimization based on the contribution of each heat source. These analyses are conducted using finite element method (FEM). A “Characterization of GaN HEMT Under short-Circuit Events” will be performed by Javier Galindos from CEI UPM in Spain. In this digest, an analysis of the failure mechanisms and degradation indicators of GaN HEMTs is presented. Understanding how this technology fails is critical, especially for space applications. Due to radiation, a common failure mechanism in space applications for GaN devices is the short-circuit event. A systematic method is proposed to perform on-board measurement of the critical electrical parameters and analyze the behavior of DUTs under short-circuit failures to build a reliability model. A setup to characterize GaN HEMTs devices is developed, and multiple tests at different conditions have been performed. The reliability challenge of GaN devices could be addressed by having on- board, in-system prognostics and device health monitoring techniques to predict device failures well ahead of time. “Short Circuit Capability Design and Thermal Management for High Efficiency Solid-State Contactor” will be introduced by Yuzhi Zhang, ABB APEX/USA. This paper introduces the design of short circuit capability and thermal management of a solid-state contactor for high efficiency ac motor application. This solid-state contactor employs a hybrid combination of semiconductor devices which involves Thyristors (SCR) and Field Effect Transistors (FET) in a parallel arrangement. The key design factors such as wire bond, semiconductor short circuit capability, power module design, and heatsink design are presented. The performance of the thermal and short- circuit of the proposed solid-state contactor are validated through the circuit simulation and full power experimental validation for a 480 V, 7.5 hp induction motor. “Operation and Characterization of Low-Loss Bidirectional Bipolar Junction Transistor” is the subject of Alireza Mojab, Director of Device Engineering at Ideal Power Inc./USA. A detailed operation and characterization of the recently developed B-TRAN as a very low-loss power semiconductor device is provided in this paper. DC characterization of B-TRAN has been already performed by probing the device on wafer-level setup and will be verified again at package- level measurement. The breakdown voltage, on-state voltage, and current gain (?) were measured to be about 1280 V, 0.2-0.5 V, and 3, respectively. A special 4-terminal TO package with double-sided cooling capability and a bidirectional driver have been designed and developed for the product sampling. Switching characterization will be performed on the TO package, using the designed bidirectional driver, and transient performance parameters will be reported. “K-TEM: KEMET Thermal Expectancy Model” will be explained byDario Zuffi, R&D Product Engineer at KEMET Bologna/Italy. The KEMET Thermal Expectancy Model is an effective tool for estimating the thermal behavior of film capacitors under different electrical conditions. The applied ripple current or ripple voltage at different frequencies and ambient temperatures are used as inputs to provide a thermal map among 3D surfaces through an element finite analysis of the capacitor. The thermal expectancy model gives a temperature map considering different convection and cooling conditions and steady-state or transient analysis. Finally, a “Paralleled SiC MOSFETs DC Circuit Breaker with SiC MPS Diode As Avalanche Voltage Clamping” is proposed by Taro Takamori, Tokyo Metropolitan University/Japan. This paper proposes a solid-state DC circuit breaker consists of SiC MOSFETs and SiC diode using avalanche voltage clamping. To realize a solid-state DC circuit breaker it is necessary to reduce