Rejeki Simanjorang

Design of high power density converter for aircraft applications

This paper presents a design methodology for high power density converter (HPDC) operating as an AC aircraft bus provider, which presents a particular gravimetric power density challenge. High power rating 3-phase AC-DC converter design with weight minimization is elaborated. By considering sizing of major converter parts that contribute to total converter weight, optimal switching frequency to yield highest power density is evaluated. The design evaluation for 50 kW converter with SiC power modules yields overall gravimetric power density of 3.76-5.35 kW/kg at optimal switching frequency of 60 kHz and volumetric power density of 7.04-7.38 kW/l respectively.

A novel gate assisted circuit to reduce switching loss and eliminate shoot-through in SiC half bridge configuration

The trend towards SiC-based high power density converter requires to drive SiC MOSFET with high-speed switching. However, it tends to aggravate dv/dt effect due to the impact of parasitic parameters, resulting in shoot-through and high device stress in the half bridge configuration. In this work, a novel gate assisted circuit is proposed to eliminate shoot-through issue without compromise on switching speed. The mathematical model for the gate assisted circuit is developed. Then the switching test experiment is set up to validate its performance with commercial SiC half bridge module, which shows a high dv/dt up to 20 and 31 V/ns at turn-on and turn-off respectively and a 34% reduction of switching loss without any shoot-through issue.

Gate driver optimization to mitigate shoot-through in high-speed switching SiC half bridge module

The high-speed switching of SiC MOSFET allows power converter to operate with higher frequency and lower switching loss. However, it tends to aggravate dv/dt effect due to the impact of parasitic parameters, resulting in shoot-through and high device stress in the half bridge configuration. In this study, a compact and high-speed gate driver is developed and optimized for SiC half bridge module. The impact of various circuit parameters including Miller capacitance, common source inductance, gate resistance and gate inductance is evaluated. The improved gate drivers with additional features are compared and optimized to eliminate shoot-through.

Magnetic Integration of Three-Phase LCL filter with Delta-Yoke Composite Core

The magnetic component is considered one of the major factors that dominate the power density of power converters. In this paper, magnetic integration of inductors of a three-phase LCL filter on delta-yoke composite core is explored and investigated. Using the conventional rectangular core as the baseline design reference, the proposed delta-yoke core achieved a weight reduction of close to 10% without affecting the filters performance. The inductances based on both shapes were calculated and verified through magnetic circuit analysis and three dimensional finite element analysis simulation. Hardware prototypes of the integrated inductor with both the conventional rectangular and the proposed delta-yoke cores were fabricated and tested with a three-phase inverter circuit to verify the design validity.

LCL Filter Design of a 50-kW 60-kHz SiC Inverter with Size and Thermal Considerations for Aerospace Applications

To achieve high power density, increasing the switching frequency of the power converter has become a trend. The LCL filter is a major contributor of the overall weight of a high-power-density converter (HPDC), especially the inverter-side inductor, which requires to suppress higher frequency harmonic contents at the inverter side. This paper describes a comprehensive design flow of the LCL filter for a 50-kW, 60-kHz two-level silicon carbide (SiC) inverter for high-power aerospace applications with space constraint and harsh ambient temperature environment. To meet the space constraint requirement and reduce the inductor size, specific design attention is made on a customized amorphous cored inductor with a comprehensive study on the relationships of inductor weight, core width, and total surface area with respect to air gap length. To overcome the harsh ambient temperature environment, a liquid cooling system of the amorphous cored inductor is also described.

A 99% efficiency SiC three-phase inverter using synchronous rectification

The reactive power in power converter with inductive load (motor drive e.g.) requires a current commutation path for the freewheeling current. Due to the high voltage drop of body diode of SiC MOSFET, a SiC Schottky diode is normally recommended as the anti-parallel freewheeling diode for SiC MOSFET to suppress the conduction of body diode. However, since the MOSFET can work as synchronous rectifier, the freewheeling diode only conducts during the dead time, leading to a low utilization rate of device. In this work, the three-phase SiC inverter using synchronous rectification is investigated. The analytical model for inverter power loss with and without freewheeling diode is built. Based on the switching characterization, the inverter with synchronous rectification permits a surprising higher efficiency than that with freewheeling diode due to the reduced current overshoot at turn-on. And a 5 kW prototype of three-phase inverter is developed, which shows a 99% high efficiency at the switching frequency of 40 kHz. This work confirms the possibility to remove the freewheeling diode in SiC inverter without degrading the efficiency.

Evaluation on filter topologies in high power density converter design for power quality and EMI control

This paper evaluates different passive filter topologies of the grid-connected high power density converter (HPDC) for the purpose power quality control and electromagnetic interference (EMI) reduction. The harmonics generated by the switching circuits in the HPDC affect power quality at lower frequency as well as EMI at higher frequency. Various common passive filter topologies are carefully evaluated in terms of reduction of total harmonic distortion (THD) and EMI.

An Accurate Subcircuit Model of SiC Half-Bridge Module for Switching-Loss Optimization

The increasing demand for high power density requires power converter to operate in high switching frequency. SiC power module is regarded as one of the most promising candidates for high-frequency applications due to the superior switching speed and low switching loss. The conventional strategy to optimize switching loss is normally achieved by repetitive double pulse tests, which is time-consuming to find an optimum gate resistance to achieve the trade-off between switching loss and EMI issues. In this work, an accurate SiC module subcircuit model is proposed. It considers the physical behavior of the device and can be directly extracted from the datasheet information. Good agreements are achieved between the PSpice simulation and experimental results in both switching waveform and switching loss. It also provides a guidance for gate driver design with a reasonable accuracy.

A 50-kW High-Frequency and High-Efficiency SiC Voltage Source Inverter for More Electric Aircraft

High power density is required for power converter in more electric aircraft due to the strict demands of volume and weight, which makes silicon carbide (SiC) extremely attractive for this application. In this paper, a prototype of 50-kW SiC two-level three-phase voltage source inverter is demonstrated with a gravimetric power density of 26 kW/kg (without inclusion of filter). A gate assisted circuit is introduced to reduce the switching loss. In addition, the ringings of voltage and current due to parasitic parameters during the switching transition can also be mitigated. A mathematical model with consideration of various parasitic parameters is developed, which illustrates the parasitic effects in high-speed switching SiC power module. The converter is operated at a switching frequency up to 100 kHz and a narrow dead band of 250 ns. The measured efficiency is 97.91%.

Online junction temperature estimation of IGBT modules for Space Vector Modulation based inverter system

This paper presents a junction temperature estimation model for space vector modulated IGBT inverter system for a real time implementation. Advances in power electronics, control systems, motor drives, and electrical machines helped in developing new technologies of Variable speed constant frequency (VSCF) system for more aircraft application. It is estimated that about 21% of the faults in the variable speed drive system are due to failure of power devices, Most of the inverters use insulated gate bipolar transistor so these applications require well designed thermal management systems to ensure the protection of IGBTs from thermal runaway. Therefore estimating the junction temperature has become essential to predict the fault and to assist in IGBT heath monitoring system. The proposed junction temperature estimation method is based on the power loss approach. Electro-thermal models for the commonly used Space Vector Modulation (SVM) techniques namely the alternate SVM and the Null V0V7 SVM are developed. The efficacy of the proposed junction temperature estimation model is verified using the measured junction temperature from the experimental setup.