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Yongsug Suh,Yuran Go,Dohwan Rho IEEE 2011 IEEE transactions on industry applications Vol.47 No.3
<P>This paper investigates unbalance compensating control algorithms for the active front-end rectifier employed in high-power motor drive systems. The generic voltage-source-converter topology of the three-level neutral-point clamped rectifier is selected for the comparative study. Three different control algorithms have been formulated based on the symmetrical components and dq synchronous frames under generalized unbalanced operating conditions. Control algorithms have been investigated with respect to major design factors in large drive systems: fault ride-through capability, harmonic distortions, and efficiency. The control algorithm having zero amplitude of negative-sequence input current shows the most optimized and cost-effective performance regarding the fault ride-through capability and efficiency aspects. The control algorithm nullifying the oscillating components of the instantaneous active power generates the least harmonic distortions. A combination of these two control algorithms depending on system requirements and operating modes provides improved performance factors of fault ride-through capability, low harmonic distortions, and efficiency under generalized unbalanced operating conditions.</P>
Yongsug Suh,Yongjoong Lee,Steimer, P.K. IEEE 2009 IEEE transactions on industrial electronics Vol.56 No.6
<P>This paper compares several medium-voltage power conversion systems for plasma torch application. The thermal plasma torch rated for 3 MW, 2 kA with the physical size of 1 m long is selected. The dynamic characteristics of the dc arc in a plasma torch are investigated using advanced 3-D magnetohydrodynamics simulation. The arc voltage noise of plusmn10% due to the periodic pressure wave is modeled as a sawtooth waveform in arc power loss term. The parameters of the Cassie-Mayr arc model are calculated based on 3-D simulation. A 12-pulse thyristor rectifier and two-phase staggered three-level step-down dc-dc converter having 12-pulse front-end diode rectifier are compared under the same dynamic operating condition. The three-level dc-dc converter has superior dynamic performance over the 12-pulse thyristor rectifier under the existence of arc disturbance noise. This power converter topology provides higher ignition voltage around 5 kV during ignition phase and higher arc stability.</P>
A Power Conversion System for AC Furnace With Enhanced Arc Stability
Suh, Yongsug,Park, Hyeoncheol,Lee, Yongjoong,Steimer, Peter K. IEEE 2010 IEEE transactions on industry applications Vol.46 No.6
<P>This paper proposes a criterion for ac arc stability and an optimal converter topology for a nonferrous metal ac arc furnace. The ac arc furnace rated for 36 kA/224 V/21 MW has been investigated. The key parameters of modified Cassie-Mayr arc model have been calculated by the electromagnetic and flow simulations for electric arc. The used arc simulation model has been validated by a laboratory free-burning arc setup. It has been shown that the steepness of arc current at zero-crossing determines the arc stability, and the associated peak arc resistance can be used as its quantitative measure. Among the evaluated three power converter systems, the forced commutated inverter topology with a six-step modulation realizes the steepest current at zero-crossing resulting in the best arc stability. The proposed converter topology having a high degree of arc stability is expected to bring about reliable operation of ac arc furnace and enhanced productivity of the total furnace system.</P>
Beomseok Chae,Yongsug Suh,Tahyun Kang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5
This paper proposes a three-phase three-switch buck-type converter as the MSC of a wind turbine system. Owing to a novel switching modulation scheme that can eliminate the unwanted diode rectifier mode switching state, the proposed system exhibits a satisfying ac voltage and current waveform quality and torque ripple up to the level of a typical current source rectifier even under a wide power factor operating range. The proposed system has been verified through simulations and HILS tests on a PMSG wind turbine model of 5MW/4160V. The proposed converter has been shown to provide a stator current THD of 3.9% and a torque ripple of 1% under the rated power condition. In addition to the inherent advantage of the reduced switch count of three-phase three-switch buck-type converters, the proposed switching modulation technique can make this converter a viable solution for the MSC placed inside of a nacelle, which is under severe volume, weight and mechanical vibration design limits.
Loss Analysis and Comparison of High Power Semiconductor Devices in 5MW PMSG MV Wind Turbine Systems
Kihyun Lee,Yongsug Suh,Yongcheol Kang 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.5
This paper provides a loss analysis and comparison of high power semiconductor devices in 5MW Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) Wind Turbine Systems (WTSs). High power semiconductor devices of the press-pack type IGCT, module type IGBT, press-pack type IGBT, and press-pack type IEGT of both 4.5kV and 6.5kV are considered in this paper. Benchmarking is performed based on the back-to-back type 3-level Neutral Point Clamped Voltage Source Converters (3L-NPC VSCs) supplied from a grid voltage of 4160V. The feasible number of semiconductor devices in parallel is designed through a loss analysis considering both the conduction and switching losses under the operating conditions of 5MW PMSG wind turbines, particularly for application in offshore wind farms. This paper investigates the loss analysis and thermal performance of 5MW 3L-NPC wind power inverters under the operating conditions of various power factors. The loss analysis and thermal analysis are confirmed through PLECS Blockset simulations with Matlab Simulink. The comparison results show that the press-pack type IGCT has the highest efficiency including the snubber loss factor.
Medium Voltage Power Supply with Enhanced Ignition Characteristics for Plasma Torches
Kyungsub Jung,Yongsug Suh 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.4
This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torches. A series resonant half-bridge topology is presented as a suitable ignition circuitry. The ignition circuitry is integrated into the main power conversion system of a multi-phase staggered three-level dc-dc converter with a diode front-end rectifier. A plasma torch rated at 3㎿, 2㎄ and having a physical size of 1m is selected to be the high enthalpy source for a waste disposal system. The steady-state and transient operations of a plasma torch are simulated. The parameters of a Cassie-Mary arc model are calculated based on 3D magneto-hydrodynamic simulations. The circuit simulation waveform shows that the ripple of the arc current can be maintained within ±10% of its rated value under the presence of a load disturbance. This power conversion configuration provides a high enough ignition voltage, around 5KA, during the ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance plasma torch system.