The Experts below are selected from a list of 52722 Experts worldwide ranked by ideXlab platform
Longya Xu - One of the best experts on this subject based on the ideXlab platform.
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sensorless field orientation control of induction machines based on a mutual mras scheme
IEEE Transactions on Industrial Electronics, 1998Co-Authors: L Zhen, Longya XuAbstract:A mutual model reference adaptive system (MRAS) is proposed to implement a position sensorless field-orientation control (FOC) of an induction machine. The reference model and adjustable model used in the mutual MRAS scheme are interchangeable. Therefore, it can be used to identify both Rotor Speed and the stator resistance of an induction machine. For the Rotor Speed estimation, one model is used as a reference model and another is the adjustable model. Pure integration and stator leakage inductance are removed from the reference model, resulting in robust performance in low and high Speed ranges. For the stator resistance identification, the two models switch their roles. To further improve estimation accuracy of the Rotor Speed and stator resistance, a simple on-line Rotor time constant identification is included. Computer simulations and experimental results are given to show its effectiveness.
Yong Cheol Kang - One of the best experts on this subject based on the ideXlab platform.
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power smoothing of a variable Speed wind turbine generator in association with the Rotor Speed dependent gain
IEEE Transactions on Sustainable Energy, 2017Co-Authors: Yeonhee Kim, Eduard Muljadi, Moses Kang, Jungwook Park, Yong Cheol KangAbstract:This paper proposes a power-smoothing scheme for a variable-Speed wind turbine generator (WTG) that can smooth out the WTG's fluctuating power caused by varying wind Speeds, and thereby keep the system frequency within a narrow range. The proposed scheme employs an additional loop based on the system frequency deviation that operates in conjunction with the maximum power point tracking (MPPT) control loop. Unlike the conventional, fixed-gain scheme, its control gain is modified with the Rotor Speed. In the proposed scheme, the control gain is determined by considering the ratio of the output of the additional loop to that of the MPPT loop. To improve the contribution of the scheme toward maintaining the frequency while ensuring the stable operation of WTGs, in the low Rotor Speed region, the ratio is set to be proportional to the Rotor Speed; in the high Rotor Speed region, the ratio remains constant. The performance of the proposed scheme is investigated under varying wind conditions for the IEEE 14-bus system. The simulation results demonstrate that the scheme successfully operates regardless of the output power fluctuation of a WTG by adjusting the gain with the Rotor Speed, and thereby improves the frequency-regulating capability of a WTG.
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Disturbance-Adaptive Short-Term Frequency Support of a DFIG Associated With the Variable Gain Based on the ROCOF and Rotor Speed
IEEE Transactions on Power Systems, 2017Co-Authors: Min Hwang, Eduard Muljadi, Gilsoo Jang, Yong Cheol KangAbstract:This paper proposes a disturbance-adaptive short-term frequency support scheme of a doubly fed induction generator (DFIG) that can improve the frequency-supporting capability while ensuring stable operation. In the proposed scheme, the output of the additional control loop is determined as the product of the frequency deviation and adaptive gain, which is modified depending on the rate of change of frequency (ROCOF) and Rotor Speed. To achieve these objectives, the adaptive gain is set to be high during the early stage of a disturbance, when the ROCOF and Rotor Speed are high. Until the frequency nadir (FN), the gain decreases with the ROCOF and Rotor Speed. After the FN, the gain decreases only with the Rotor Speed. The simulation results demonstrate that the proposed scheme improves the FN and maximum ROCOF while ensuring the stable operation of a DFIG under various wind conditions irrespective of the disturbance conditions by adaptively changing the control gain with the ROCOF and Rotor Speed, even if the wind Speed decreases and a consecutive disturbance occurs.
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releasable kinetic energy based inertial control of a dfig wind power plant
IEEE Transactions on Sustainable Energy, 2016Co-Authors: Jinsik Lee, Eduard Muljadi, Poul Ejnar Sorensen, Yong Cheol KangAbstract:Wind turbine generators (WTGs) in a wind power plant (WPP) contain different levels of releasable kinetic energy (KE) because of the wake effects. This paper proposes a releasable KE-based inertial control scheme for a doubly fed induction generator (DFIG) WPP that differentiates the contributions of the WTGs depending on their stored KE. The proposed KE-based gain scheme aims to make use of the releasable KE in a WPP to raise the frequency nadir. To achieve this, two additional loops for the inertial control are implemented in each DFIG controller: the rate of change of frequency and droop loops. The proposed scheme adjusts the two loop gains in a DFIG controller depending on its Rotor Speed so that a DFIG operating at a higher Rotor Speed releases more KE. The performance of the proposed scheme was investigated under various wind conditions. The results clearly indicate that the proposed scheme successfully improves the frequency nadir more than the conventional same gain scheme by releasing more KE stored in a WPP, and it helps all WTGs to ensure stable operation during inertial control by avoiding the Rotor Speed reaching the minimum Speed limit.
Eduard Muljadi - One of the best experts on this subject based on the ideXlab platform.
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power smoothing of a variable Speed wind turbine generator in association with the Rotor Speed dependent gain
IEEE Transactions on Sustainable Energy, 2017Co-Authors: Yeonhee Kim, Eduard Muljadi, Moses Kang, Jungwook Park, Yong Cheol KangAbstract:This paper proposes a power-smoothing scheme for a variable-Speed wind turbine generator (WTG) that can smooth out the WTG's fluctuating power caused by varying wind Speeds, and thereby keep the system frequency within a narrow range. The proposed scheme employs an additional loop based on the system frequency deviation that operates in conjunction with the maximum power point tracking (MPPT) control loop. Unlike the conventional, fixed-gain scheme, its control gain is modified with the Rotor Speed. In the proposed scheme, the control gain is determined by considering the ratio of the output of the additional loop to that of the MPPT loop. To improve the contribution of the scheme toward maintaining the frequency while ensuring the stable operation of WTGs, in the low Rotor Speed region, the ratio is set to be proportional to the Rotor Speed; in the high Rotor Speed region, the ratio remains constant. The performance of the proposed scheme is investigated under varying wind conditions for the IEEE 14-bus system. The simulation results demonstrate that the scheme successfully operates regardless of the output power fluctuation of a WTG by adjusting the gain with the Rotor Speed, and thereby improves the frequency-regulating capability of a WTG.
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Disturbance-Adaptive Short-Term Frequency Support of a DFIG Associated With the Variable Gain Based on the ROCOF and Rotor Speed
IEEE Transactions on Power Systems, 2017Co-Authors: Min Hwang, Eduard Muljadi, Gilsoo Jang, Yong Cheol KangAbstract:This paper proposes a disturbance-adaptive short-term frequency support scheme of a doubly fed induction generator (DFIG) that can improve the frequency-supporting capability while ensuring stable operation. In the proposed scheme, the output of the additional control loop is determined as the product of the frequency deviation and adaptive gain, which is modified depending on the rate of change of frequency (ROCOF) and Rotor Speed. To achieve these objectives, the adaptive gain is set to be high during the early stage of a disturbance, when the ROCOF and Rotor Speed are high. Until the frequency nadir (FN), the gain decreases with the ROCOF and Rotor Speed. After the FN, the gain decreases only with the Rotor Speed. The simulation results demonstrate that the proposed scheme improves the FN and maximum ROCOF while ensuring the stable operation of a DFIG under various wind conditions irrespective of the disturbance conditions by adaptively changing the control gain with the ROCOF and Rotor Speed, even if the wind Speed decreases and a consecutive disturbance occurs.
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releasable kinetic energy based inertial control of a dfig wind power plant
IEEE Transactions on Sustainable Energy, 2016Co-Authors: Jinsik Lee, Eduard Muljadi, Poul Ejnar Sorensen, Yong Cheol KangAbstract:Wind turbine generators (WTGs) in a wind power plant (WPP) contain different levels of releasable kinetic energy (KE) because of the wake effects. This paper proposes a releasable KE-based inertial control scheme for a doubly fed induction generator (DFIG) WPP that differentiates the contributions of the WTGs depending on their stored KE. The proposed KE-based gain scheme aims to make use of the releasable KE in a WPP to raise the frequency nadir. To achieve this, two additional loops for the inertial control are implemented in each DFIG controller: the rate of change of frequency and droop loops. The proposed scheme adjusts the two loop gains in a DFIG controller depending on its Rotor Speed so that a DFIG operating at a higher Rotor Speed releases more KE. The performance of the proposed scheme was investigated under various wind conditions. The results clearly indicate that the proposed scheme successfully improves the frequency nadir more than the conventional same gain scheme by releasing more KE stored in a WPP, and it helps all WTGs to ensure stable operation during inertial control by avoiding the Rotor Speed reaching the minimum Speed limit.
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a conservative control strategy for variable Speed stall regulated wind turbines
19th American Society of Mechanical Engineers (ASME) Wind Energy Symposium Reno NV (US) 01 10 2000--01 13 2000, 2000Co-Authors: Eduard Muljadi, K Pierce, P MiglioreAbstract:Simulation models of a variable-Speed, fixed-pitch wind turbine were investigated to evaluate the feasibility of constraining Rotor Speed and power output without the benefit of active aerodynamic control devices. A strategy was postulated to control rotational Speed by specifying the demanded generator torque. By controlling Rotor Speed in relation to wind Speed, the aerodynamic power extracted by the blades from the wind was manipulated. Specifically, the blades were caused to stall in high winds. In low and moderate winds, the demanded generator torque and the resulting Rotor Speed were controlled to cause the wind turbine to operate near maximum efficiency. Using the developed models, simulations were conducted of operation in turbulent winds. Results indicated that Rotor Speed and power output were well regulated. Preliminary investigations of system dynamics showed that, compared to fixed-Speed operation, variable-Speed operation caused cyclic loading amplitude to be reduced for the turbine blades and low-Speed shaft and slightly increased for the tower loads. This result suggests a favorable impact on fatigue life from implementation of the proposed control strategy.
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control strategy for variable Speed stall regulated wind turbines
American Control Conference, 1998Co-Authors: Eduard Muljadi, K Pierce, P MiglioreAbstract:A variable-Speed, constant-pitch wind turbine was investigated to evaluate the feasibility of constraining its Rotor Speed and power output without the benefit of active aerodynamic control devices. A strategy was postulated to control rotational Speed by specifying the demanded generator torque. By controlling Rotor Speed in relation to wind Speed, the aerodynamic power extracted by the blades from the wind was manipulated. Specifically, the blades were caused to stall in high winds. In low and moderate winds, the demanded generator torque and the resulting Rotor Speed were controlled to cause the wind turbine to operate near maximum efficiency. A computational model was developed, and simulations were conducted of operation in high turbulent winds. Results indicated that Rotor Speed and power output were well regulated.
L Zhen - One of the best experts on this subject based on the ideXlab platform.
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sensorless field orientation control of induction machines based on a mutual mras scheme
IEEE Transactions on Industrial Electronics, 1998Co-Authors: L Zhen, Longya XuAbstract:A mutual model reference adaptive system (MRAS) is proposed to implement a position sensorless field-orientation control (FOC) of an induction machine. The reference model and adjustable model used in the mutual MRAS scheme are interchangeable. Therefore, it can be used to identify both Rotor Speed and the stator resistance of an induction machine. For the Rotor Speed estimation, one model is used as a reference model and another is the adjustable model. Pure integration and stator leakage inductance are removed from the reference model, resulting in robust performance in low and high Speed ranges. For the stator resistance identification, the two models switch their roles. To further improve estimation accuracy of the Rotor Speed and stator resistance, a simple on-line Rotor time constant identification is included. Computer simulations and experimental results are given to show its effectiveness.
Ivo Herman - One of the best experts on this subject based on the ideXlab platform.
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ac drive observability analysis
IEEE Transactions on Industrial Electronics, 2013Co-Authors: Pavel Vaclavek, P Blaha, Ivo HermanAbstract:AC induction motors and permanent magnet synchronous drives became very popular for motion control applications due to their simple and reliable construction. Sensorless drive control is required in many applications to reduce drive production costs. While many approaches to magnetic flux, Rotor Speed, or other quantities needed to control electrical machine were proposed, conditions under which these quantities can be estimated are not often sufficiently investigated. In this paper, induction machine and permanent-magnet-synchronous-machine drive state observability analysis is presented, together with conditions allowing reliable Rotor Speed and position estimation. A method based on the nonlinear dynamical system state observability theory is proposed, resulting in a unified approach to the ac drive observability analysis.
