Jeihoon Baek

Development of 1-MW Inductive Power Transfer System for a High-Speed Train

Design and fabrication of a 1-MW inductive power transfer (IPT) system that supplies power to the vehicle in real time without any battery charge is proposed for a high-speed train. The IPT system consists of a 1-MW resonant inverter, a 128-m transmitter, four pickups, including rectifiers, and a wireless feedback network to maintain a constant output voltage of the pickups. The operating frequency of the system is 60 kHz to achieve efficient power transfer with a large air gap. The measured efficiency of the IPT system at the 818-kW output power of the pickups for the 5-cm air gap is 82.7%. The electromagnetic field and the induced voltage at the rail are also measured for safety evaluation. The fabricated IPT system was adapted to the high-speed train, and the train successfully accelerates to a speed of 10 km/h according to startup procedures.

Iterative Condition Monitoring and Fault Diagnosis Scheme of Electric Motor for Harsh Industrial Application

This paper presents a robust diagnosis technique by iteratively analyzing the pattern of multiple fault signatures in a motor current signal. It is mathematically and experimentally proved that the proposed diagnosis algorithm provides highly accurate monitoring performance while minimizing both false detection and miss detection rate under high noise and nonlinear machine operating condition. These results are verified on a digital-signal-processor-based motor drive system where motor control and fault diagnosis are performed in real time.

Soft-Switching AC-Link Three-Phase AC–AC Buck–Boost Converter

In this paper, the soft-switching ac-link ac-ac buck-boost converter will be studied in more detail. This single-stage converter, which is, in essence, an extension of the dc-dc buck-boost converter, can be an excellent alternative to dc-link converters. Being a buck-boost converter, this converter is capable of both stepping-up and stepping-down the voltage. The link current and voltage are both alternating, and their frequency can be as high as permitted by the switches and the sampling time of the microcontroller. This eliminates the need for dc inductors or dc electrolytic capacitors, and the main energy storage element is an ac inductor (L). Moreover, in this converter, galvanic isolation can be provided by adding a single-phase high-frequency transformer to the link. Therefore, the proposed converter is expected to be more compact compared to the conventional dc-link converter. The other advantage of this converter is the soft switching of the switches, which is feasible by adding a small capacitor (C) to the link. In this paper, the design and analysis of this converter will be studied in detail. In order to accurately analyze this converter, the effect of the LC link resonance on the performance of the converter will be studied. This analysis helps in evaluating the performance of the converter at low power levels when the resonating time of the LC link is not negligible. Using this analysis, the link peak current and the link frequency may be calculated at any point of operation. The accuracy of this method is verified through simulations and experiments. Detailed comparison of the proposed converter with the dc-link converter will be also presented in this paper. It will be shown that, despite having more switches, the current rating of the switches is lower in this converter. Moreover, the efficiencies of the two converters will be compared. Finally, the performance of the soft-switching ac-link ac-ac buck-boost converter is experimentally evaluated in this paper. It will be shown that the converter has the possibility of changing both the frequency and the voltage. Both step-up and step-down operations will be verified through experiments.

Optimal design of five-phase permanent magnet assisted synchronous reluctance motor for low output torque ripple

This paper presents the optimal design of five-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM) for low torque ripple. PMa-SynRMs are similar to interior permanent magnet (IPM) motors in structure but with reduced permanent magnets, PMa-SynRMs are more economical. In this study, lumped parameter model (LPM) is used in the approach to initially design the five-phase PMa-SynRM. Thousands of models are designed by LPM, which are then converged to optimized model using differential evolution strategy (DES). Optimization is done with maximum efficiency and minimum torque ripple as objective. The optimized 3 kW five-phase PMa-SynRM is then analyzed by finite element method (FEM) for fine tuning. Simulation results for back electromotive force (EMF), developed torque, torque ripple, cogging torque, and other necessary motor parameters such as d and q-axis inductances variation over respective axis currents are verified by fabricated prototype.

Optimal Design and Performance Analysis of Permanent Magnet Assisted Synchronous Reluctance Portable Generators

In this paper, design and performance analysis of robust and inexpensive permanent magnet-assisted synchronous reluctance generators (PMa-SynRG) for tactical and commercial generator sets is studied. More specifically, the optimal design approach is investigated for minimizing volume and maximizing performance for the portable generator. In order to find optimized PMa-SynRG, stator winding configurations and rotor structures are analyzed using the lumped parameter model (LPM). After comparisons of stator windings and rotor structure by LPM, the selected stator winding and rotor structure are optimized using a differential evolution strategy (DES). Finally, output performances are verified by finite element analysis (FEA) and experimental tests. This design process is developed for the optimized design of PMa-SynRG to achieve minimum magnet and machine volume as well as maximum efficiency simultaneously.

Sparse AC-Link Buck–Boost Inverter

Due to their remarkable merits, the soft-switching ac-link universal power converters have received noticeable attention during the last few years. These converters, which can be configured as dc-dc, dc-ac, ac-dc, or ac-ac, are compact, reliable, and offer longer life time compared to the other types of converters. However, they require more switches, which make the control process more complicated. This paper proposes a modified configuration for the dc-ac power conversion, which reduces the number of switches without changing the principles of operation. This converter, which is named sparse ac-link buck-boost inverter, reduces the number of switches from 20 to 18. Despite reducing the number of switches, the partial resonant time, during which no power is transferred, is as short as the original configuration. An important feature of this inverter is that it can be fabricated by IGBT modules, which are more compact and more cost-effective compared to the discrete devices. This paper presents the principles of the operation of this configuration, and compares the efficiency, the failure rate, and the current rating of the switches in the proposed and original inverters. It is shown that the failure rates of the sparse configuration are lower than the original configuration. Therefore, they have longer lifetime. The efficiency of the sparse configuration is slightly lower than that of the original configuration. However, by using reverse blocking IGBTs in the sparse configuration, the efficiency of the proposed inverter will be improved significantly. This paper evaluates the performance of the proposed inverter through simulation and experiment.

Optimal design of PM assisted synchronous reluctance generators using lumped parameter model and Differential Evolution Strategy

This paper presents the design of high performance permanent magnet-assisted synchronous reluctance generators (PMa-SynRG) for the 3kW tactical quiet generator set. By introducing a proper quantity of permanent magnets into the synchronous reluctance generator rotor core an extended constant power-speed range at high efficiency and high power factor can be achieved. Different stator winding configurations i.e. distributed winding and concentrated winding of PMa-SynRG are compared using an analytical model based on lumped parameter model (LPM). For comparison, initially the distributed winding machine is optimized using differential evolution strategy (DES) and then the rotor structure of concentrated winding machine is optimized using the same stator. Finally, output performances are compared using finite element analysis. This design process is developed for optimized design of PMa-SynRG with minimum magnet volume, cogging torque and maximum efficiency and power factor.

Comparison of optimized permanent magnet assisted synchronous reluctance motors with three-phase and five-phase systems

This paper presents comparison of optimized permanent magnet assisted synchronous reluctance motor (PMa-SynRM) with three-phase and five-phase architectures. The three-phase and five-phase PMa-SynRMs are designed with magnetic equivalent circuits (lumped parameter model (LPM)) and 2D finite element analysis (FEA) approach. Objective function with torque ripple, motor cost and efficiency is used to derive optimal design of each motor. Multiple parametric simulations are done to minimize the objective function through differential evolution strategy (DES). Both PMa-SynRMs are fabricated with same power rating (3kW) and same volume. Torque pulsation, back electromotive force (EMF), flux linkage, d- and q-axis inductances versus their respective currents and cogging torque are intensively simulated through FEA and are experimentally tested on the prototypes.

Optimal design and comparison of stator winding configurations in permanent magnet assisted synchronous reluctance generator

This paper presents design of high performance permanent magnet-assisted synchronous reluctance generators (PMa-SynRG) for 3kW tactical quiet generator set. Adding the proper quantity of permanent magnets into the synchronous reluctance generator rotor core can offer large constant power-speed range, high efficiency and high power factor. Different stator winding configurations such as distributed windings and concentrated windings are compared using lumped parameter model (LPM). For this comparison, the distributed winding machine is optimized by differential evolution strategy (DES) and the rotor structure of the concentrated winding machine is optimized based on the same stator. Finally, output performances are compared using finite element analysis. The design is optimized for achieving the minimum magnet volume, minimum cogging torque, maximum efficiency, and maximum power factor.

Bidirectional Soft-Switching Series AC-Link Inverter

This paper proposes a novel bidirectional inverter, named series ac-link inverter. This three-phase inverter belongs to a new class of partial resonant ac-link converters in which the link is formed by a series ac inductor/capacitor (LC) pair having low reactive ratings. The input and output of this converter can be either dc, ac, single-phase, or multiphase. Therefore, they can appear as dc-dc, dc-ac, ac-dc, and ac-ac configurations. In all of these configurations, the ac capacitor is the main energy-storage element, and the inductor is merely added to facilitate the zero-current turnoff of the switches and their soft turn-on. Due to the zero-current turnoff of the switches in the proposed converter, the use of SCRs with natural commutation is possible as well. Since the current and voltage of the link are both alternating, no bulky dc-electrolytic capacitors are required in this converter. This paper mainly focuses on bidirectional dc to three-phase ac conversion. This single-stage inverter can step up or step down the voltage in a wide range. If galvanic isolation is required a single-phase high-frequency transformer can be added to the link. In the proposed inverter, the power can flow in both directions, and therefore, it is an excellent candidate for battery-utility interface and electric vehicle applications. In this paper, the principles of the operation of the proposed inverter, along with its design and analysis, are studied. Moreover, the performance of the proposed configuration is evaluated in this paper. Both simulation and experimental results are included.