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This paper presents a comparative study on high-frequency active rectifier-based zero voltage soft-switching (ZVS) resonant dc-dc power converters with Gallium Nitride Heterojunction-Field-Effect-Transistor (GaN-HFET) for inductive power transfer (IPT) systems. The two types of active rectifiers, i.e. high-frequency bridgeless rectifier (BLREC) and totem-pole rectifier (TPREC) are adopted for the...
This paper addresses the modeling and controller design of large scale dc microgrids with nonlinear loads. First, the dynamic models of the sources and loads are discussed in detail, placing particular emphasis on generators with passive rectification and Constant Power Loads (CPLs) with input filters. These models will be defined as source and load nodes which along with internal nodes, will be integrated...
Although the hybrid switch consisting of high power Si IGBT and low power SiC MOSFET achieves reduction of losses and cost, there is a severe concern of its short-circuit capability due to its internal SiC MOSFET with small die size. Experimental study shows that the short-circuit capability of hybrid switch is limited by that of SiC MOSFET. The physical mechanism of short-circuit capability of SiC...
In a magnetically coupled resonant (MCR) wireless power transfer (WPT) system, adding repeating coils is an effective way to lengthen transmission distance and improve the transferred power in a wide range. This paper investigated a 3-coil MCR WPT system. Based on fundamental harmonic analysis on the equivalent circuit model, the relationship between the transmission characteristics and the spatial...
Research conducted previously has shown that a battery electric vehicle (BEV) motor design incorporating drive-cycle optimization can lead to achievement of a higher torque density motor that consumes less energy over the drive-cycle in comparison to a conventionally designed motor. Such a motor indirectly extends the driving range of the BEV. Firstly, in this paper, a baseline fractional slot concentrated...
High performance power conversion equipment is currently gaining an increasing interest for aircraft applications. In particular, isolated bidirectional DC/DC converters are often proposed for modern HVDC aircraft distribution systems. For such reason an evaluation of several isolated DC/DC converter topology is carried out considering the proposed application, interfacing a 270V DC network with a...
To address the active power feeding issue in the parallel Uninterruptible Power Supply (UPS) system, a DC-link Voltage Protection (DCVP) control strategy is proposed in this paper. The proposed control method only relies on local load information, which increases the system reliability and robustness. Moreover, virtual resistance based regulation strategies are proposed for solving the active power...
Cascaded or distributed module-level inverters are becoming increasingly desirable for photovoltaic applications. The authors have demonstrated an AC-stacked topology that allows each inverter to operate completely autonomously from all the others. The only required communications is a low-bandwidth synchronization signal communicated from the point-of-grid-connection. This paper describes the communications...
This paper presents an isolated DB LLC resonant converter with frequency adaptive phase-shift modulation control which overcomes the unity gain problem of conventional DB converter. The proposed control maintains the Zero Voltage Switching (ZVS) to all switches under all operating voltage and load variations. The control proposed for this circuit based on two control variables: switching frequency...
This paper focuses on the control of three-phase brushless asynchronous excitation system (TBAES) of the aircraft wound-field synchronous starter-generator system. Since the closed-loop control of the field current of synchronous starter-generator is hard to achieve, generally, the TBAES is powered by the onboard three-phase power system during the low speed region and cut off one phase of the onboard...
This paper presents an analytical model to provide a rapid estimation of the steady-state averaged power loss of a T-type STATCOM with Virtual Zero level Modulation (VZM) to balance the neutral point voltage. A case study is then conducted on a 54kVA rated T-type STATCOM system to investigate the power loss distribution over power devices and variations over switching frequency. A comparison is made...
While investigations on short-circuit ruggedness of discrete SiC MOSFET are widely encountered in the scientific literature, there is not so much research dealing with the operational robustness of high power SiC MOSFET modules. In this paper, the short-circuit (SC) ruggedness under hard switching fault (HSF) of a commercial 1.2 kV/180 A SiC MOSFET power module in half-bridge configuration will be...
Bi-directional switches, also called four quadrant switches (FQS), are the basic building blocks in many power converter circuits, such as cyclo-converters, matrix converters etc. Conventional approaches to realize bi-directional switch involves combination of unidirectional controllable blocking device (IGBT or MOSFET) and diode. In this approach, current flows through multiple devices for any direction...
Gallium Nitride (GaN) high electron mobility transistor (HEMT) is one of the promising candidates to replace existing switches in high-frequency high power converter applications. Reliability of GaN HEMT is an important issue for its commercial deployment. Online prognosis of this transistor ensures robust reliability for mission critical applications. Online prognosis requires identification of fault...
This paper investigates the torque production and the torque ripple reduction of 6-stator/7-rotor-pole (6/7) variable flux reluctance machine (VFRM). Based on the harmonic analysis, the instantaneous torque equation is firstly derived by considering the spectra of the armature inductance and current. The average torque is found to be mainly produced by the mutual inductances between the field and...
Inductor current in the high speed switching converters is used as a feedback signal for current mode control and over current fault protection. Sensing inductor current for the use of digital controllers require high bandwidth current sensors and also need high speed Analog to Digital Converter (ADC) to convert the sensed current into digital domain. Use of high bandwidth current sensors and high...
Modular multilevel converters (MMC) have many advantages owing to their power-stage modularity. However, this modularity does not extend directly to the control. Particularly, the balancing control usually requires central coordination and increases in complexity with the system size. This paper presents a balancing control method for a more general modular multilevel converter with series and parallel...
In this paper, a cost-effective and reliable equivalent series resistance (ESR) estimation method for aluminium electrolytic capacitors used as DC-link capacitors in front-end rectifier fed inverters is proposed. The proposed method is based on the extraction of switching frequency components of DC-link voltage and current using band-pass filters. A limiting value of switching frequency is identified,...
Transformer-less single-phase grid-tied inverter is attractive due to low cost, high efficiency, and small size. However, leakage current and second-order ripple power have to be well dealt with. Because the leakage current is a potential threat for body safety and the ripple power will decrease overall efficiency and system reliability. Both issues become obstacles for practical applications. This...
Solid state transformers (SSTs) can be interconnected with each other through a distribution feeder to form a smart grid. When the main grid is disconnected, SSTs form an islanded microgrid. With available communications, master-slave microgrid control structure can be adopted. The system-level stability analysis can be simplified by considering only the grid interface stage of the SST. The loop feeder...
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