• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.437-442
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• 2000

An alternative inverse feedback structure for adaptive active control of periodic noise is introduced for systems with nonminimum phase cancellation path. To obtain the inverse model of the nonminimum phase cancellation path, the cancellation path model can be factorized into a minimum phase term and a maximum phase term. The maximum phase term containing unstable zeros makes the inverse model unstable. To avoid the instability, we alter the inverse model of the maximum phase system into an anti-causal FIR one. An LMS predictor estimates the future samples of the noise, which are necessary for causality of both anti-causal FIR approximation for the stable inverse of the maximum phase system and time-delay existing in the cancellation path. The proposed method has a faster convergence behavior and a better transient response than the conventional FX-LMS algorithms with the same internal model control structure since a filtered reference signal is not required. We compare the proposed methods with the conventional methods through simulation studies.

• Structural Engineering and Mechanics
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• v.87 no.2
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• pp.117-127
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• 2023

To efficiently attenuate seismic responses of a structure, a novel pneumatic-driven active dynamic vibration absorber (PD-ADVA) is proposed in this study. PD-ADVA aims to realize closed-loop control using a simple and intuitive control algorithm, which takes the structure velocity response as the input signal and then outputs an inverse control force to primary structure. The corresponding active control theory and phase control mechanism of the system are studied by numerical and theoretical methods, the system's control performance and amplitude-frequency characteristics under seismic excitations are explored. The capability of the proposed active control system to cope with frequency-varying random excitation is evaluated by comparing with the optimum tuning TMD. The analysis results show that the control algorithm of PD-ADVA ensures the control force always output to the structure in the opposite direction of the velocity response, indicating that the presented system does not produce a negative effect. The phase difference between the response of uncontrolled and controlled structures is zero, while the phase difference between the control force and the harmonic excitation is π, the theoretical and numerical results demonstrate that PD-ADVA always generates beneficial control effects. The PD-ADVA can effectively mitigate the structural seismic responses, and its control performance is insensitive to amplitude. Compared with the optimum tuning TMD, PD-ADVA has better control performance and higher system stability, and will not have negative effects under seismic wave excitations.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1838-1842
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• 2004

Gain and phase margins of a first order plus delayed time (FOPDT) process controlled by generalized predictive controller (GPC) are related to the control parameters ${\lambda}$ (control move suppression parameter) and ${\alpha}$ (smoothing filter coefficient) and the normalized delay of the process. Variation ranges of gain and phase margins are determined. It is shown that the margins cannot be assigned independently for a wide range of variation and the range is narrowing by increase of the normalized delay of the process. And finally curves are given to use for adjustment of the controller parameters in order to obtain a specific pair of gain and phase margins.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.472-476
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• 2012

In this paper, a sensorless control scheme for a three-phase bi-directional voltage-type PWM rectifier in wind power generation system that operates without the input AC voltage sensors (generator side) is described. The basic principles and classification of the PWM rectifier are analyzed, and then the three-phase mathematical model of the input AC voltage sensorless PWM rectifier control system is established. The proposed scheme has been developed in order to lower the cost of the three-phase PWM rectifier but still achieve excellent output voltage regulation, limited current harmonic content, and unity input power factor.

• Journal of Power Electronics
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• v.10 no.6
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• pp.717-723
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• 2010

This paper proposes a new torque control algorithm for BLDC motors to get the maximum torque in the high speed region. The delay of the phase currents is severe due to the stator reactance. The torque fluctuations of BLDC motors increase and the average torque is decreases due to a slow rise in the phase current when compared to the back EMF. In this paper, the phase current of BLDC motors under the high speed condition is analyzed and a torque maximization control is developed on the basis of using numerical analysis. Computer simulations and experimental results show the usefulness of the proposed control algorithm.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.531-534
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• 1989

In this paper, the way that input voltage and input line current as a control variable is provided as one unit is projected. Till no, have denied with three phase balanced load. But, in that case, total power factor compensation is difficult, for to control each phase at unbalanced load. Therefor, in this paper suggest of the scheme that three phase unbalanced load is controlled by each phase and input total power factor is compensated unit input factor. therefore, in this paper suggest that three phase unbalanced load is controlled and the method in compensation of unit input factor to be attended by unbalanced load. Besides, the object of control is calculating quantity for input voltage and input line current for the point at issuse make to improve of control method at unbalanced load. As a result, control system of each phase could maintain as a unit input total power factor has been state diviation error of 2% with unbalanced load.

• The Transactions of the Korean Institute of Power Electronics
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• v.28 no.1
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• pp.22-29
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• 2023

A grid-connected inverter can be used in grid-connected or stand-alone modes. Generally, a grid-connected inverter operates in a grid-connected mode, but the inverter operates in stand-alone mode if grid faults occur. In the stand-alone mode, the grid-connected inverter must supply electric power to a critical load that needs to receive stable power even though grid faults occur. Generally, three-phase loads are used as critical loads, but a single phase is configured in some cases. In these conditions, the critical load is required to unbalance the load power consumption, which makes the three-phase load voltage unbalancd. This unbalanced voltage problem can cause fatal problems to the three-phase critical loads, and thus must be addressed. Hence, this paper proposes an algorithm to solve this unbalanced voltage problem by the individual phase current control. The proposed method is verified using Psim simulation and experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.1
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• pp.89-93
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• 2017

This study proposes a grid voltage estimation scheme without a phase delay in the voltage-sensorless control of a grid-connected inverter to enhance its economic feasibility, such as manufacturing cost and system complexity. The proposed scheme estimates grid voltages using a disturbance observer (DOB)-based current controller to control the grid-connected inverter without grid-side voltage sensors. The proposed voltage-sensorless control scheme can be applied successfully to grid-connected inverters, which should be operated with synchronization to the grid, considering the phase angle of the grid can be effectively detected through estimating the grid voltages by DOB. However, a problem associated with the phase delay in estimated grid voltages remains because the DOB has dynamic behavior similar to low-pass filter. Hence, the estimated grid voltages are compensated by a phase lead compensator to overcome the limitation. The effectiveness of the proposed control and estimation schemes is proven through simulations and experiments using a 2 kVA prototype inverter.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.94-100
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• 2018

Generally, in a single-phase energy storage system (ESS) for households, AC ripple component with twice the fundamental frequency exists inevitably in the DC link voltage of single-phase PCS. In the grid-connected mode of a single-phase inverter, the AC ripple component in the DC link voltage causes low-order harmonics on grid-side current that deteriorates power quality on an AC grid. In this work, a control system adopting a feedforward controller is established to eliminate the AC ripple interference on the DC link side. Optimal battery nominal voltage design method is also proposed by considering the voltage loss and AC ripple voltage on DC link side in a single-phase ESS. Finally, the control system and battery nominal voltage design method are verified through simulations and experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.356-362
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• 2015

This paper presents a current control strategy in the synchronous reference frame for a single-phase PWM converter, which ensures sinusoidal input current control under the distorted source voltage and frequency condition. Given that the distorted source voltage distorts the phase angle for PWM converter control, the input current contains the same harmonics as the source voltage. Aside from the distorted voltage, the variation in source frequency reduces the performance of input current control. To achieve sinusoidal input current control under the distorted source voltage and frequency condition, this paper proposes a compensation strategy of current reference with the distortion component extracted from the phase angle and a detection strategy of frequency variation from the output of a synchronous reference frame phase-lock loop. The experimental results confirm the validity of the proposed method under the distorted source voltage and frequency condition.