Stepwise Design Methodology and Heterogeneous Integration Routine of Air-Cooled SiC Inverter for Electric Vehicle

Carrying on SiC devices, the air-cooled inverter of the electric vehicle (EV) can eliminate the traditional complicated liquid-cooling system in order to obtain a light and compact performance of the powertrain, which is considered as the trend of next-generation EV. However, the air-cooled SiC inverter lacks strategic design methodology and heterogeneous integration routine for critical components. In this article, a stepwise design methodology is proposed for the air-cooled SiC inverter in the power module, dc-link capacitor, and heat sink levels. In the power module level, an electrical-thermal-mechanical multiphysics model is proposed. The multidimension stress distribution principles in a six-in-one SiC power module are demonstrated. An improved power module is presented and confirmed by using the observed multiphysics design principles. In the dc-link capacitor level, ripple modeling of the inverter and capacitor are created. Considering the tradeoffs among ripple voltage, ripple current, and cost, optimal strategies to determine the material and minimize the capacitance of the dc-link capacitor are proposed. In the heat sink level, thermal resistance of air-cooled heat sink is modeled. Structure and material properties of the heat sink are optimally designed by using a comprehensive electro-thermal analysis. Based on the optimal design results, the prototypes of the customized SiC power module and heterogeneously integrated air-cooled inverter are fabricated. Experimental results are presented to demonstrate the feasibility of the designed and manufactured air-cooled SiC inverter.Ministry of Education (MOE)Nanyang Technological UniversityThis work was supported in part by the National Natural Science Foundation of China under Grant 51607016, in part by the National Key Research and Development Program of China under Grant 2017YFB0102303, and in part by the Singapore ACRF Tier 1 Grant RG 85/18. The work of X. Zhang was supported by the NTU Startup Grant (SCOPES)

Review of multiport power converters for distribution network applications

Multiport power converters integrate three or more energy devices into a single (potentially highly controllable and efficient) hub. These characteristics suggest that multiport power converters may be valuable for the decarbonisation of distribution networks, where the increase of converter-interfaced devices has degraded system reliability and efficiency. This review analyses the suitability of a wide range of multiport power converter solutions for four example distribution network applications (where previous studies have focussed on a limited range of topologies or applications) and the research areas that can progress their maturity. A review of grid codes and standards overviews the base capability that multiport power converters are likely to require, some of which are carried forward as requirements for a novel comparison tool. The comparison tool is developed to qualify and score reviewed topologies in terms of a range of features that are weighted for the applications. Isolated and partially-isolated topologies perform well due to their flexibility to be configured for the specifications and their operational capabilities (including modularity and voltage decoupling). Further research should focus on the complex control interactions between ports and scaling of these topologies for medium voltages. In contrast, many direct current non-isolated topologies do not qualify due to their low flexibility to be configured for the applications. This suggests that future research could focus on the development of a more flexible non-isolated multiport power converter configuration to take advantage of the high efficiency and low footprint that these topologies might otherwise offer for low voltage applications

Design and Control of Power Converters for High Power-Quality Interface with Utility and Aviation Grids

Power electronics as a subject integrating power devices, electric and electronic circuits, control, and thermal and mechanic design, requires not only knowledge and engineering insight for each subarea, but also understanding of interface issues when incorporating these different areas into high performance converter design.Addressing these fundamental questions, the dissertation studies design and control issues in three types of power converters applied in low-frequency high-power transmission, medium-frequency converter emulated grid, and high-frequency high-density aviation grid, respectively, with the focus on discovering, understanding, and mitigating interface issues to improve power quality and converter performance, and to reduce the noise emission.For hybrid ac/dc power transmission,• Analyze the interface transformer saturation issue between ac and dc power flow under line unbalances.• Proposed both passive transformer design and active hybrid-line-impedance-conditioner to suppress this issue.For transmission line emulator,• Propose general transmission line emulation schemes with extension capability.• Analyze and actively suppress the effects of sensing/sampling bias and PWM ripple on emulation considering interfaced grid impedance.• Analyze the stability issue caused by interaction of the emulator and its interfaced impedance. A criterion that determines the stability and impedance boundary of the emulator is proposed.For aircraft battery charger,• Investigate architectures for dual-input and dual-output battery charger, and a three-level integrated topology using GaN devices is proposed to achieve high density.• Identify and analyze the mechanisms and impacts of high switching frequency, di/dt, dv/dt on sensing and power quality control; mitigate solutions are proposed.• Model and compensate the distortion due to charging transition of device junction capacitances in three-level converters.• Find the previously overlooked device junction capacitance of the nonactive devices in three-level converters, and analyze the impacts on switching loss, device stress, and current distortion. A loss calculation method is proposed using the data from the conventional double pulse tester.• Establish fundamental knowledge on performance degradation of EMI filters. The impacts and mechanisms of both inductive and capacitive coupling on different filter structures are understood. Characterization methodology including measuring, modeling, and prediction of filter insertion loss is proposed. Mitigation solutions are proposed to reduce inter-component coupling and self-parasitics

REGULATED TRANSFORMER RECTIFIER UNIT FOR MORE ELECTRIC AIRCRAFTS

The impending trends in the global demand of more-electric-aircrafts with higher efficiency, high power density, and high degree of compactness has opened up numerous opportunities in front of avionic industries to develop innovative power electronic interfaces. Traditionally, passive diode-bridge based transformer rectifier units (TRU) have been used to generate a DC voltage supply from variable frequency and variable voltage AC power out of the turbo generators. These topologies suffer from bulky and heavy low-frequency transformer size, lack of DC-link voltage regulation flexibility, high degree of harmonic contents in the input currents, and additional cooling arrangement requirements. This PhD research proposes an alternative approach to replace TRUs by actively controlled Regulated Transformer Rectifier Units (RTRUs) employing the advantages of emerging wide band gap (WBG) semiconductor technology. The proposed RTRU utilizing Silicon Carbide (SiC) power devices is composed of a three-phase active boost power factor correction (PFC) rectifier followed by an isolated phase-shifted full bridge (PSFB) DC-DC converter. Various innovative control algorithms for wide-range input frequency operation, ultra-compact EMI filter design methodology, DC link capacitor reduction approach and novel start-up schemes are proposed in order to improve power quality and transient dynamics and to enhance power density of the integrated converter system. Furthermore, a variable switching frequency control algorithm of PSFB DC-DC converter has been proposed for tracking maximum conversion efficiency at all feasible operating conditions. In addition, an innovative methodology engaging multi-objective optimization for designing electromagnetic interference (EMI) filter stage with minimized volume subjected to the reactive power constraints is analyzed and validated experimentally. For proof-of-concept verifications, three different conversion stages i.e. EMI filter, three-phase boost PFC and PSFB converter are individually developed and tested with upto 6kW (continuous) / 10kW (peak) power rating, which can interface a variable input voltage (190V-240V AC RMS) variable frequency (360Hz – 800Hz) three-phase AC excitation source, emulating the airplane turbo generator and provide an AC RMS voltage of 190V to 260V. According to the experimental measurements, total harmonic distortion (THD) as low as 4.3% and an output voltage ripple of ±1% are achieved at rated output power. The proposed SiC based RTRU prototype is ~8% more efficient and ~50% lighter than state-of-the art TRU technologies