• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.367-375
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• 2022

Generally, a proportional-resonant controller is used to eliminate steady-state errors during the voltage-current control of a double-conversion uninterruptible power supply (UPS) in a stationary reference frame. Additionally, the feed-forward control compensating for the load current, which can be considered a disturbance of the voltage controller, can be used to improve the disturbance rejection performance. However, during the parallel operation of UPSs, circulating current can occur between UPS modules when performing both feed-forward control and droop control because feed-forward control reduces the circulating current impedance. This study proposes a feed-forward compensation technique that considers the impedance of circulating current. An additional feed-forward compensation technique is developed to enhance the disturbance rejection performance. The validity of the proposed feed-forward compensation technique is verified by the experiment results of the parallel operation of a 500 W double-conversion UPS module.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.1969-1982
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• 2015

The virtual inertia control (VIC) of wind turbine with directly-driven permanent-magnet synchronous generator (D-PMSG) can act similarly to the conventional synchronous generator in inertia response and frequency control, thereby supporting the system frequency stability. However, because the wind speed is inconstant and changeable to a certain extent and the D-PMSG is a complex nonlinear system, there are great difficulties in the virtual inertia optimal control of the D-PMSG. Based on the design principle of the active disturbance rejection control (ADRC), this paper presents a new VIC strategy for the D-PMSG from the perspective of power disturbance suppression in the system. The strategy helps fulfill the power grid disturbance estimation and compensation by means of the extended state observer (ESO) so as to improve the disturbance-resisting performance of the system. Compared with conventional proportional-derivative virtual inertia control (PDVIC), this method, which is of better adaptability and robustness, can not only improve the property of the D-PMSG responding to the system frequency but also reduce the influence of wind speed disturbance. The simulation and experiment results have verified the effectiveness and feasibility of the VIC based on the ADRC.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.262-267
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• 2004

This paper is concerned with a design method of two-degree-of-freedom controller by Coefficient Diagram Method (CDM). The two-degree-of-freedom control system satisfies both of tracking and disturbance rejection performances, but requires tuning of many parameters. By the proposed design method, these parameters can be obtained properly without any adjustment. Furthermore, the tracking and disturbance rejection performances can be simultaneously designed. The effectiveness of the proposed method is demonstrated by the simulation.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.341-344
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• 1993

This paper presents the general MRAC algorithm design, it's real time implementation and investigates the effect of purely deterministic disturbances to adaptive control algorithm. The design of adaptive control algorithm to reject the disturbances properly is also presented. In real time application, adaptive control algorithm is considered to investigate its performance by using DC motor. Disturbance rejection algorithm is investigated in simulation.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.878-883
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• 1990

There have been many approaches to solve the disturbance rejection problem in the control of LTI systems with state independent disturbances or possibly nonlinear state dependent disturbances. From the view point of each actuator, robot manipulators can be modeled as the second class of systems. With this model, M.Nakao et al. [1] introduced a decentralized control scheme based on interference estimation which is simple in its implementation and robust to the coupled dynamics and parameter variations. This paper systematically generalizes the control scheme to arbitrary finite dimensional LTI systems with disturbances. In doing so, we develop a disturbance observer theory for solving the disturbance rejection problem. We also present a discrete version of the theory with discussion of sampling and time-delay effects.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.6
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• pp.425-434
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• 2003

The disturbance observer(DOB) has been widely used in high speed and high precision motion control applications and the characteristics of DOB have been investigated in depth. Though most of DOB's have been implemented as the discrete-time form in digital devices, we are still short of the researches on discrete-time DOB (DDOB) in spite of rich references on continuous-time DOB. In this paper, we discuss about the disturbance rejection property and measurement noise effect of discrete-time DOB. Especially, we will focus on revealing the role of sampling time in designing the discrete-time DOB and show the validity of analysis through simulations and experiments for optical disk drive systems.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.705-707
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• 2004

In this paper, we propose a robust control technique against parameter uncertainties as well as external disturbances. It is robust control scheme using discrete-time state space disturbance observer. It does not require disturbance modeling, plant inverse modeling and/or Q filter. In frequency domain, its performance is evaluated in terms of sensitivity and complementary sensitivity as well as gain and phase margin. Finally we discuss design criterion of state space disturbance observer considering its performance in frequency domain.

• Journal of IKEEE
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• v.24 no.3
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• pp.877-882
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• 2020

This paper presents performance comparison study of current control methods for grid connected inverter (GCI) system. Different current control methods have been developed for GCI systems and each controller has its own advantages and limitations. Steady state and transient dynamic performance of the GCI current controllers are compared in this paper. The performance of the proposed command feedforward control (CFFC) and disturbance rejection control (DRC) is analyzed before and after application to all GCI current controllers. The proposed CFFC and DRC control algorithms is analyzed in a frequency domain and the simulation and experiment models of each GCI current control methods are developed for verification of the performance.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.2
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• pp.73-80
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• 1996

This paper proposes a stabilizing controller for the multirate sampled-data systems which have a periodic output measurement scheme. A sufficient condition for maintaining observability in the multirate sampled-data system is derived and a design strategy for disturbance rejection is proposed. The proposed controller has IMC structure, and can be decomposed into the disturbance estimator and the inverse of the fast uniform sampled plant. We assume that the plant is open-loop stable and the disturbance consists of a sum of finite number of sinusoids with different frequencies. An example is presented for illustrations.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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• pp.1234-1239
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• 2013

This paper provides a technical review of speed control using variable gain PI algorithm for BLDC(Brushless DC) motor. Usually the PI control is used in many motor applications, but a general PI control has problems of overshooting and disturbance for response. By the change of PI gain in motor control operation, these problems can be solved. To find the optimized PI gains for BLDC motor control, many control methods have been proposed. In this paper, the control algorithm with a variable PI gain is applied to improve overshooting response in transient region and rapid load disturbance rejection. Fixed gain and variable gain PI controls are compared. The validity of the propose method is verified by experiment.