Hyunjae Yoo

System Integration and Power-Flow Management for a Series Hybrid Electric Vehicle Using Supercapacitors and Batteries

In this paper, system integration and power-flow management algorithms for a four-wheel-driven series hybrid electric vehicle (HEV) having multiple power sources composed of a diesel-engine-based generator, lead acid battery bank, and supercapacitor bank are presented. The super-capacitor is utilized as a short-term energy storage device to meet the dynamic performance of the vehicle, while the battery is utilized as a mid-term energy storage for the electric vehicle (EV) mode operation due to its higher energy density. The generator based on an interior permanent magnet machine (IPMM), run by a diesel engine, provides the average power for the normal operation of the vehicle. Thanks to the proposed power-flow management algorithm, each of the energy sources is controlled appropriately and also the dynamic performance of the vehicle has been improved. The proposed power-flow management algorithm has been experimentally verified with a full-scale prototype vehicle.

System Integration and Power Flow Management for a Series Hybrid Electric Vehicle using Super-capacitors and Batteries

In this paper, the power flow management algorithms for a 4-wheel driven series hybrid electric vehicle (HEV) is presented, that has multiple power sources composed of diesel engine based generator, lead-acid battery bank, and super-capacitor bank. Super-capacitor is utilized as short term energy storage means to meet dynamic performance of the vehicle, while the battery is utilized as a mid term energy storage for the electric vehicle (EV) mode operation due to their higher energy density. The generator based on interior permanent magnet machine (IPMM), run by a diesel engine, provides average power for the normal operation of the vehicle. Thanks to the proposed power flow management algorithm, not only the dynamic performance but also the fuel efficiency and reliability of the vehicle have been improved. The proposed power flow management algorithm has been experimentally verified with a full scale prototype vehicle.

A new circuit design and control to reduce input harmonic current for a three-phase ac machine drive system having a very small dc-link capacitor

This paper presents a new circuit topology to meet the input harmonic current standard for an ac machine drive system which has a very small dc-link capacitor. The proposed circuit topology is based on a harmonic current injection method, and it keeps up size and cost competitiveness of an ac machine drive system having a very small dc-link capacitor. Also, this paper proposes an appropriate control algorithm and a stability analysis for the proposed circuit topology. Experimental results reveal the validity of the proposed circuit topology and its control method. Also, it is confirmed that the harmonic current standard can be satisfied with the proposed circuit and its control method.

LCL filter design and control for grid-connected PWM converter

This paper describes LCL filter design and control for grid-connected PWM converter. To attenuate switching harmonics on grid side with an LCL filter, cost-effectiveness must be considered to select filter parameters. This paper proposes a filter design method based on a computer simulation tool. Depending on users optimal cost function, filter parameters are chosen without tedious and repetitive mathematical calculations. On the other hand, damping factors must be introduced in control of LCL filter to suppress the inherent resonant characteristics. Since the resonance phenomenon is minimized by increasing the ratio of switching frequency to fundamental grid frequency in most conventional researches, it is difficult to be employed in high power system due to the limited switching frequency of power semiconductors in the converter. In this paper, a novel current controller with generalized gain determination is suggested. Discrete time controller based on only grid voltages and currents information is introduced, which yields desirable dynamic response even in lower switching frequency of PWM converter. Simulations and experimental results are presented to validate the proposed design and control procedures.

A Novel Approach to Reduce Line Harmonic Current for a Three-phase Diode Rectifier-fed Electrolytic Capacitor-less Inverter

This paper describes a three-phase high power factor rectifier for an electrolytic capacitor-less inverter based on the current injection scheme. The rectifier injects the machine side zero sequence current into the grid side through three bi-directional switches. This paper also introduces the modified circuit topology which is suitable for an electrolytic capacitor-less inverter. A bulky dc or ac reactor can be removed due to small capacitance of the proposed circuit topology. The principle of current injection and a proper current control method based on a feed-forward control concept have been described in this paper. The validity of the proposed circuit topology has been confirmed by simulation and experimental results.

Design of a Variable Speed Compressor Drive System for Air-Conditioner without Electrolytic Capacitor

This paper presents an electrolytic capacitor-less variable speed drive system for the compressor of an air-conditioner to enhance cost and size competitiveness and reliability. The electrolytic capacitor in the DC link of the inverter is replaced by a small film capacitor, whose capacitance is around a couple thousandth of the conventional drive system. Due to the small capacitance, not only the size of the DC link capacitor can be reduced, but also the initial charging circuit of the inverter can be saved. Furthermore, the total harmonic current of the AC source side can be reduced to one third of the conventional system. The effectiveness of the proposed system has been verified by several experimental results using a commercial air-conditioner with the modified inverter.

A power flow control strategy for optimal fuel efficiency of a variable speed engine-generator based series hybrid electric vehicle

This paper presents a new power flow control strategy for a variable speed engine-generator based series hybrid electric vehicle. The specific fuel consumption map of the internal combustion engine (ICE) has been obtained by off-line experiments to achieve optimal fuel efficiency. The proposed power flow controller makes it possible that the ICE operates at its optimal fuel efficiency points without degrading desired dynamic performance. Experimental results of the actual vehicle test as well as the laboratory based load test are shown to verify the proposed power flow control strategy.

Nine-phase Permanent Magnet motor drive system for ultra high-speed elevator

In this paper, a 9-phase Permanent Magnet (PM) synchronous motor drive system based on multiple 3-phase conventional drive systems has been proposed. A 9-phase motor has been developed as a traction motor for a world record ultra high speed elevator. The simplified mathematical model, which can be incorporated with 3-phase current controller, has been derived. The feasibility and the validity of the proposed drive system have been demonstrated by experimental results of the scaled version of a prototype 9-phase motor.

Novel current control strategy for maximum tracking operation under saturated voltage condition

A synchronous frame proportional integral (PI) current controller has been widely used in AC electric machine drive system. This current controller should contain an anti-windup scheme to prevent the integral term in the controller from blowing up. This paper addresses the reference tracking performance of current controller with the anti-windup when the output of the PWM inverter is saturated due to limitation of DC bus voltage. The problem of the conventional PI current controller caused by the inverter saturation is identified in a viewpoint of the reference tracking, and a novel current control strategy is proposed. The proposed current control strategy shows the better tracking performance without blowing up the integral term in controller even in the case of inverter saturation. Experimental and computer simulation results are shown to verify the effectiveness of the proposed strategy.

Minimum torque ripple pulse width-modulation with reduced switching frequency for multi-megawatt motor drive

In this paper, the characteristics of ripple current of multi-megawatt induction motor fed by a PWM inverter is investigated. And, based on the investigation a novel PWM scheme is devised to reduce the switching loss of the inverter under the same torque ripple of the induction motor. The proposed PWM is composed with two parts. One is Minimum Torque Ripple Pulse-Width Modulation (MTRPWM) which is optimized in terms of minimum torque ripple in high Modulation Index. The other is a part to decide a minimum switching frequency while keeping the average torque ripple under the allowable value at the various operating conditions. It is named RSF. Consequently, only changing PWM method from conventional fixed switching frequency CPWM to the proposed PWM with RSF, the switching loss of inverter driving 3.5MW induction motor has been reduced by 51.6%, when MI is 1.12.