Kyungsub Jung

Comparison of high power semiconductor devices losses in 5MW PMSG MV wind turbines

This paper provides a comparison of high power semiconductor devices in 5MW-class Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) wind turbines. High power semiconductor devices of 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 neutral point clamped 3-level back-to-back type voltage source converter supplied from grid voltage of 4160V. The feasible number of semiconductor devices in parallel is designed through the loss analysis considering both conduction and switching losses under the given operating conditions of 5MW-class PMSG wind turbines, particularly for the application in offshore wind farms. The loss analysis is confirmed through PLECS simulations. The comparison result shows that press-pack type IGBT and IGCT semiconductor device have the highest efficiency considering the snubber loss of IGCT.

Arc Stability Control of a High-Power Thyristor Rectifier System in a DC Arc Furnace

Fundamental features of the arc stability in a dc arc furnace of 720 V/100 kA/72 MW have been investigated. The Cassie-Mayr arc model has been employed and applied for the target dc arc furnace. In order to characterize the parameters of the Cassie-Mayr arc model and the behavior of unstable arc dynamics, the advanced arc simulations of magneto-hydrodynamics (MHD) have been performed. From the results of MHD simulation, the dc arc dynamic resistance is proposed to be an effective arc stability function reflecting the instability of dynamic arc behavior. A control strategy of the 12-pulse thyristor rectifier system to regulate the arc stability function is also proposed in this paper. The simulation and experimental results confirm the usefulness of the proposed dynamic arc resistance as the arc stability function along with the active control strategy. The proposed arc stability function can be regarded as an effective criterion for the overall power conversion system to maintain highly stable arcing operation leading to better productivity and reliability in a dc arc furnace.

Analysis and comparison of high power semiconductor device losses in 5MW PMSG MV wind turbines

This paper provides a comparison of high power semiconductor devices in 5MW-class Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) wind turbines. High power semiconductor devices of press-pack type IGCT, module type IGBT, press-pack type IEGT, and press-pack type IGBT of both 4.5kV and 6.5kV are considered in this paper. Benchmarking is performed based on neutral point clamped 3-level back-to-back type voltage source converter supplied from grid voltage of 4160V. The feasible number of semiconductor devices in parallel is designed through the loss analysis considering both conduction and switching losses under the given operating conditions of 5MW-class PMSG wind turbines, particularly for the application in offshore wind farms. The loss analysis is confirmed through PLECS simulations. The comparison result shows that press-pack IGCT type semiconductor device has the highest efficiency.

Control algorithm of high power rectifier system in DC arc furnace for improved arc stability

Fundamental features of the arc stability in DC arc furnace of 720V/100kA/72MW have been investigated. Cassie-Mayr arc model has been employed and applied for the target DC arc furnace. In order to characterize the parameters of Cassie-Mayr arc model and the behavior of unstable arc dynamics, the advanced arc simulations of magneto-hydrodynamics (MHD) has been performed. From the results of MHD simulation, DC arc dynamic resistance is proposed to be an effective arc stability function reflecting the instability of dynamic arc behavior. A control strategy of high power rectifier system to regulate the arc stability function is also proposed in this paper. The simulation and experimental result confirm the usefulness of proposed dynamic arc resistance as arc stability function along with the active control strategy. The proposed arc stability function can be regarded as an effective criterion for the overall power conversion system to maintain highly stable arcing operation leading to better productivity and reliability in a DC arc furnace.

Medium Voltage Power Supply with Enhanced Ignition Characteristics for Plasma Torches

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.

Analysis of neutral point deviation in 3-level NPC converter under unbalanced 3-phase AC grid

This paper presents a neutral point deviation compensating control algorithm applied to a 3-level NPC converter. The neutral point deviation is analyzed with a focus on the current flowing out of or into the neutral point of the dc-link. Based on the zero sequence components of the reference voltages, this paper analyzes the neutral point deviation and balancing control for 3-level NPC converter. An analytical method is proposed to calculate the injected zero sequence voltage for neutral point balancing based on average neutral current. This paper also proposes a control scheme compensating for the neutral point deviation under generalized unbalanced grid operating conditions. The positive and negative sequence components of the pole voltages and ac input currents are employed to accurately explain the behavior of 3-level NPC converter. Simulation results are shown to verify the validity of the proposed algorithm.

Compensation of neutral point deviation in 3-level NPC converter under unbalanced grid conditions

This paper presents a neutral point deviation compensating control algorithm applied to a 3-level NPC converter. The neutral point deviation is analyzed with a focus on the current flowing out of or into the neutral point of the dc-link. Based on the zero sequence components of the reference voltages, this paper analyzes the neutral point deviation and balancing control for 3-level NPC converter. An analytical method is proposed to calculate the injected zero sequence voltage for neutral point balancing based on average neutral current. This paper also proposes a control scheme compensating for the neutral point deviation under generalized unbalanced grid operating conditions. The positive and negative sequence components of the pole voltages and ac input currents are employed to accurately explain the behavior of 3-level NPC converter. Simulation and experimental results for a test set up of 30kW are shown to verify the validity of the proposed algorithm.

Arc stability control of high power thyristor rectifier system in DC arc furnace

Fundamental features of the arc stability in DC arc furnace of 720V/100kA/72MW have been investigated. Cassie-Mayr arc model has been employed and applied for the target dc arc furnace. In order to characterize the parameters of Cassie-Mayr arc model and the behavior of unstable arc dynamics, the advanced arc simulations of magneto-hydrodynamics (MHD) has been performed. From the results of MHD simulation, dc arc dynamic resistance is proposed to be an effective arc stability function reflecting the instability of dynamic arc behavior. A control strategy to regulate the arc stability function is also proposed in this paper. The simulation and experimental result confirm the usefulness of proposed dynamic arc resistance as arc stability function along with the active control strategy. The proposed arc stability function can be regarded as an effective criterion for the overall power conversion system to maintain highly stable arcing operation leading to better productivity and reliability in a dc arc furnace.

A medium voltage power supply with enhanced ignition characteristics for plasma torch in waste disposal system

This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torch in waste disposal system. Series resonant half-bridge topology is presented to be 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. The plasma torch rated for 3MW, 2kA and having the physical size of 1m long is selected to be a high enthalpy source in waste disposal system. The steady-state and transient operations of plasma torch are simulated. Circuit simulation waveform shows that the ripple of arc current can be maintained within ±10% of its rated value under the existence of load disturbance. This power conversion configuration provides high enough ignition voltage around 30kV during ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance and reliable plasma torch system.