Showing papers by "Seung-Ki Sul published in 2010"
TL;DR: In this paper, the authors compared several structures of the hybrid excavator with the supercapacitor and compared them with each other from the aspect of fuel efficiency, the additional cost due to the hybridization, and the expected payback time.
Abstract: This paper shows several structures of the hybrid excavator with the supercapacitor and compares them with each other from the aspect of fuel efficiency, the additional cost due to the hybridization, and the expected payback time. According to the comparison result, it can be concluded that a compound-type hybrid structure is a better solution than others because of its short expected payback time and higher reliability. In addition, the power control algorithm of the engine and the supercapacitor is proposed. To verify the proposed algorithm, the computer simulation and the engine dynamo test were performed, and the results are presented. The results show that the proposed control algorithm can achieve balance of the power and the energy between the energy sources and the load, and by hybridization, the fuel consumption can be reduced by about 24% compared with the conventional hydraulic excavator. The hardware implementation is now in progress for a 22-ton class excavator.
99 citations
18 Mar 2010
TL;DR: In this paper, a new circuit topology is proposed to meet the input harmonic current standard for an ac machine drive system which has a very small dc-link capacitor, and it keeps up size and cost competitiveness.
Abstract: 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.
56 citations
18 Mar 2010
TL;DR: In this article, the authors presented a new maximum torque per ampere (MTPA) control method for interior permanent magnet synchronous machine (IPMSM) drives, which uses the conventional speed control scheme, where speed control loop produces the magnitude of the stator current reference.
Abstract: This paper presents a new maximum torque per ampere (MTPA) control method for Interior Permanent Magnet Synchronous Machine (IPMSM) drives. The proposed method uses the conventional speed control scheme, where speed control loop produces the magnitude of the stator current reference. According to the current angle in the rotor reference frame, θ, the current reference is decomposed to the d-/q-axis current references. To operate IPMSM in the MTPA mode, this paper presents the new MTPA tracking method using signal injection. This method works based on the inherent definition of MTPA, which is that the torque variation due to the current angle variation should be zero at the specific torque. The proposed method detects the accurate current angle where the magnitude of the stator current is the minimum at the specific torque without any pre-made look-up tables and machine parameters.
42 citations
TL;DR: In this article, a new pulsewidth modulation (PWM) method for the matrix converter is proposed to generally use these three virtual dc-link voltages, which can create the identical switching sequences to those created by the conventional space vector PWM (SVPWM), and a new switching sequence that reduces output current switching ripple can be easily adopted within the proposed PWM method.
Abstract: A matrix converter interfaces with three-phase ac voltage source, which creates three different virtual dc-link voltages. In this paper, a new pulsewidth modulation (PWM) method for the matrix converter is proposed to generally use these three virtual dc-link voltages. By using the two higher line-to-line voltages as the virtual dc-link voltages, the proposed method can create the identical switching sequences to those created by the conventional space vector PWM (SVPWM) method. Moreover, the proposed method is able to select the appropriate virtual dc-link voltage, according to the PWM purpose and/or load condition. In this paper, the virtual dc-link voltages adjacent to the output voltage reference are introduced to reduce output-current switching ripples. The feasibility of the proposed PWM method was verified by a computer simulation and experimental results. The output voltage and current waveforms produced by using the proposed method can be equal or better than those created using the conventional SVPWM method. Moreover, a new switching sequence that reduces output-current switching ripple can be easily adopted within the proposed PWM method. The harmonic characteristics of output current created using the proposed method are markedly improved over those using the conventional PWM method.
33 citations
TL;DR: In this article, a disturbance observer is used for relative position control, where the position reference is considered as the result of a disturbance, and the position control can be performed by both the disturbance observer and a position controller.
Abstract: This paper presents an application of a disturbance observer for a relative position control system. In this system, since the prefixed motion profile is not defined ex ante, the acceleration state which is generated based on the profile is also not available. Therefore, feedforward acceleration controls cannot be used, and the position control performance is restricted solely by the bandwidth of the position controller. To enhance the control performance, disturbance observers can be utilized actively. The proposed method considers the position reference just as the result of a disturbance. Therefore, the relative position control can be performed by a disturbance observer as well as a position controller. As a result, the position control performance of the proposed method has been enhanced by up to 30% compared with that of the conventional method. The feasibility of the proposed method has been verified by experimental results using a high-precision linear motion control system as well as by analysis based on Bode plots.
30 citations
21 Jun 2010
TL;DR: In this paper, a new maximum efficiency operation method of SynRM based on a signal injection was introduced, which can trace the maximum efficiency operating point without dependency on the machine parameters.
Abstract: This paper introduces a new maximum efficiency operation method of Synchronous Reluctance Machine (SynRM) based on a signal injection. To control SynRM in the maximum efficient operating point, the sum of the copper losses and the iron losses should be minimized. Although many kinds of efficient operating method had been introduced, most of them were dependent upon the machine parameters. The inaccuracy of the machine parameters, especially d-/q-axis inductances which are known to vary extremely according to the operating condition, makes the maximum efficiency operating point be out of the target. In this paper, a new maximum efficiency operating method of SynRM is proposed. Adopting the high frequency signal injection concept, the maximum efficiency operating point can be traced without dependency on the machine parameters. The effectiveness of the method is verified by experimental results.
20 citations
18 Mar 2010
TL;DR: Compared to the PWM current ripple of the conventional single inverter system, that of the proposed scheme can be conspicuously reduced without the voltage drop at the inductors.
Abstract: This paper describes a topology with a parallel operation of PWM inverters for high speed motor drive systems. High speed motors have been widely used in industries to reduce system size and improve power conversion efficiency. However, the high speed motors sometimes suffer from core losses caused by PWM current ripples; noting that the phase inductance, L s , of a high speed motor is smaller than that of ordinary motors, it is significant that the current ripple generated by a Pulse Width modulation(PWM) inverter becomes noticeable in the high speed motor. In the proposed topology, three PWM inverters are connected in parallel through nine coupled inductors. Compared to the PWM current ripple of the conventional single inverter system, that of the proposed scheme can be conspicuously reduced without the voltage drop at the inductors. In this paper, a theoretical analysis of the output voltage of the proposed topology is presented, and then the validity of the proposed method is verified by experimental results.
16 citations
01 Nov 2010
TL;DR: In this paper, a sensorless control for induction machines using a square wave voltage injection is presented, where the error signal has lower harmonics than that of the conventional sinusoidal injection method.
Abstract: This paper presents a sensorless control for induction machines using a square-wave voltage injection. Multiple saliencies and a saliency orientation shift are considered in this paper. The multiple saliencies make the position error signal distorted and the estimation of the flux position difficult. And, due to the saliency orientation shift, the estimated rotor flux position drifts from the actual rotor flux position according to torque and speed. When the square-wave voltage is injected into the estimated synchronous reference d-q frame, the error signal has lower harmonics than that of the conventional sinusoidal injection method. In addition, by injecting the square-wave into q axis of the estimated synchronous reference frame, the flux can be estimated with less error compared to the injection into d axis. Because of the enhanced rotor flux estimation performance, the square wave injection into q axis reveals better torque controllability compared to the sine wave injection into d axis.
9 citations
21 Jun 2010
TL;DR: In this paper, an enhanced sensorless method to estimate rotor position for PMSM is presented, which is based on the estimation of the back-EMF using a state observer.
Abstract: This paper presents an enhanced sensorless method to estimate rotor position for PMSM. The proposed method is based on the estimation of the back-EMF using a state observer. The conventional sensorless methods based on back-EMF estimation has problem of model discordance to the real motor model in electrical or mechanical dynamic state. An analysis is performed to verify how this problem deteriorates the estimation performance in the dynamic situations. Proposed method modifies state observer to match to the real motor model even in a fast accelerating situation. In order to verify feasibility of the proposed method, experimental results in a steady state and a dynamic state are presented.
9 citations
01 Nov 2010
TL;DR: This paper deals with a separate double-winding 12-phase BLDC motor fed from individual H-bridge inverters, which is fault tolerant in that continuous operation is possible under fault conditions and has the same torque ripple reduction effect as 24-phase counterpart.
Abstract: This paper deals with a separate double-winding 12-phase BLDC motor fed from individual H-bridge inverters. The system is fault tolerant in that continuous operation is possible under fault conditions. Every phase is electrically independent from each other and doubly wound to intensify the redundancy of the system. Furthermore, each phase is asymmetrically 15 degrees apart to have the same torque ripple reduction effect as 24-phase counterpart. Two partial windings in each phase are taken control of by one inverter module. One module consists of two single phase H-bridge inverters and can be detached from other modules to be repaired or replaced while it is out of operation. In terms of motor drive, sinusoidal wave currents are applied to the stators for minimizing torque ripples and the operating efficiency at low rotational speed of motor is improved by series connection of the partial windings. Simulations and experimental studies are conducted to evaluate the performance of the system based on a prototype motor.
8 citations
21 Jun 2010
TL;DR: In this article, a power converter configuration for the compound type hybrid excavator with an ultra capacitor, which is directly connected in parallel to dc-link capacitor without DC/DC converter, is presented.
Abstract: This paper presents a power converter configuration for the compound type hybrid excavator with an ultra capacitor, which is directly connected in parallel to dc-link capacitor without DC/DC converter. With this structure, the efficiency of the system has been improved compared to the conventional compound type hybrid excavator where an ultra capacitor was connected via DC/DC converter. And, a power control strategy for the suggested configuration is described. To suppress the oscillation of the voltage of the ultra capacitor, an observer for the internal voltage of the ultra capacitor is devised. To evaluate the effectiveness of the proposed configuration and power control strategy, extensive computer simulations have been performed and the results are discussed. The feasibility of the simulation results is experimentally verified based on mid-sized excavator.
01 Nov 2010
TL;DR: In this paper, a series-connected Universal Link (SUL) converter is proposed to transfer the power via the high frequency transformers and single phase full bridge converters, which can increase the power density and the efficiency significantly.
Abstract: This paper presents a novel AC/DC power converter topology for the future energy conversion network. The proposed Series-connected Universal Link (SUL) converter transfers the power via the high frequency transformers and single phase full bridge converters. The shape of input AC source current is sinusoidal without PWM switching of the input side converter. Thanks to the reduced reactive components and high frequency transformer, the proposed converter can increase the power density and the efficiency significantly. It is expected that the SUL converter can be easily adapted to various renewable energy sources and energy storage system. Experimental results with prototype show the effectiveness of the proposed power converter topology.
Patent•
23 Apr 2010
TL;DR: In this article, a motor control apparatus has a current-command divider (109) configured to divide a given command-current amplitude value to a command current by a phase-angle command value, a current controller (106) configures to control a current for outputting a command voltage so that the command current is equal to a current flowing through a motor, a torque-variation calculator (110) calculated to calculate motor electric power based on the command voltage and the motor current and to calculate a torque variation using the motor electric powers, and a phase angle generator (111
Abstract: PROBLEM TO BE SOLVED: To perform high-efficiency motor control by which convergence of a current phase angle on an operating point corresponding to maximum torque control, minimum current control or minimum power loss is quickly achieved and which is not influenced by variation in motor parameters. SOLUTION: A motor control apparatus has a current-command divider (109) configured to divide a given command-current amplitude value to a command current by a phase-angle command value, a current controller (106) configured to control a current for outputting a command voltage so that the command current is equal to a current flowing through a motor, a torque-variation calculator (110) configured to calculate motor electric power based on the command voltage and the motor current and to calculate a torque variation using the motor electric power, and a phase angle generator (111) configured to generate a phase angle based on the torque variation. COPYRIGHT: (C)2011,JPO&INPIT
20 Jun 2010
TL;DR: In this article, three PWM inverters are connected in parallel through nine coupled inductors, and a theoretical analysis of the output voltage of the proposed topology is presented, and then the validity of the method is verified by experimental results.
Abstract: High speed motors have been widely used in industries to reduce system size and improve power conversion efficiency. However, the high speed motors sometimes suffer from core losses caused by PWM current ripple; noting that the phase inductance, , of high speed motor is smaller than that of ordinary motors. In the proposed topology, three PWM inverters are connected in parallel through nine coupled inductors. Compared to the PWM current ripple of the conventional single inverter system, that of the proposed scheme can be conspicuously reduced without the voltage drop at the inductors. In this paper a theoretical analysis of the output voltage of the proposed topology is presented, and then the validity of the proposed method is verified by experimental results.
01 Nov 2010
TL;DR: A bidirectional isolated AC-AC converter for grid connection of various loads or energy sources that can be utilized for interfacing renewable energy sources to the grid as well as traditional motor drives is proposed.
Abstract: This paper proposes a bidirectional isolated AC-AC converter for grid connection of various loads or energy sources. The converters can be utilized for interfacing renewable energy sources to the grid as well as traditional motor drives. It does not employ any line-frequency transformer, large electrolytic capacitors, and inductors to diminish the volume and enhance the reliability of the converter. Instead, it uses high-frequency transformers and small film capacitors. Also, Because of its modular structure, it can be extended easily according to the system voltage. Its configuration and the concept of power flow are introduced and the simulation results are presented.
01 Jul 2010
TL;DR: In this article, an active voltage balancing approach using a forward fly-back power converter is presented, where cell with the higher voltage is selected to extract the extra energy and then a proportion of this extracted energy is distributed to other supercapacitors via the proposed circuit.
Abstract: This paper presents an active voltage balancing approach using a forward fly-back power converter. In the proposed balancing scheme, cell with the higher voltage is selected to extract the extra energy and then a proportion of this extracted energy is distributed to other supercapacitors via the proposed circuit. A system structure consisting of five supercapacitors is built up to verify operation of the proposed scheme.