• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.123-126
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• 1996

In this paper, optimal modulation controller is designed to improve the stability of A.C. and A.C.-D.C. power system, and optimal theory is applied to select optimal modulation controller input signal Optimal modulation controller for speed governor and exciter controller system is constructed in A.C. power system, while the controller is constructed to the both control systems like AC. power system, considering ACR-AVR, APR-$A{\gamma}R$ as the control method of direct current system. It is considered that the stability of A.C. power system only and A.C.-D.C. power system against load fluctuations and disturbances under case of optimal modulation control.

• Current Photovoltaic Research
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• v.4 no.4
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• pp.131-139
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• 2016

This paper shows the series power device in the massive roof-top PVs and domestic loads. D-UPFC as the series power device controls the distribution voltage during voltage rise (or fall) condition. D-UPFC consists of the bi-directional ac-ac converter and the transformer. In order to verify the D-UPFC voltage control, the distribution model is used in the case study. D-UPFC enables the voltage control in the distribution voltage range. Dynamic voltage control from voltage rise and voltage fall conditions is performed. Scaled-down experimental test of the D-UPFC is verified the voltage control and it is well performed without high voltage spikes in the inductive load.

• Journal of Power Electronics
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• v.15 no.3
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• pp.577-586
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• 2015

The combination of voltage feedforward and feedback control is a conventional approach for correcting the power factor in single-phase ac-dc boost converters. The feedback duty ratio increases significantly with an increase of the line frequency and input inductance. Therefore, the performance of the conventional approach is highly dependent on the bandwidth of the feedback controller. As a result, the input power quality can be significantly exacerbated due to uncompensated duty ratios if the feedback controller is limited. This paper proposes an input impedance and current feedforward control method to reduce the control portion of the feedback controller. The findings in this paper are 1) the theoretical derivation and analysis of variations of line frequency and input inductance on a power factor correction approach, 2) guaranteed consistent performance in a wide range of conditions, and 3) that a low switching frequency can be utilized by the proposed method. A MATLAB/Simulink model and a 1.2kW dual boost converter are built to demonstrate the effectiveness of the proposed method.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.163-167
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• 2000

This paper presents the digital control of single-phase power factor correction(PFC) converter which has the variable gain according to the condition of inner control loop error. Generally the gain of inner current control loop in single-stage PFC converter has a constant magnitude. This has a bad influence on the power factor because current loop doesn't operate smoothly in the condition that input voltage is low In particular a digital controller has more time delay than an analog controller and degrades This drops the phase margin of the total digital PFC system,. It causes the problem that the gain of current control loop isn't increased enough. In addition the oscillation happens in the peak value of the input voltage open loop PFC system gain changes according to ac input voltage. These aspects make the design of the digital PFC controller difficult The digital PFC controller presented in this paper has a variable gain of current control loop according to input voltage. The 1kW converter was used to verify the efficiency of the digital PFC controller.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.3
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• pp.140-151
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• 2004

This paper presents the HVDC system modelling for analysis of subsynchronous oscillation and the design of the subsynchronous oscillation damping controller in HVDC system with the aid of novel eigenvalue analysis program. The HVDC system models include both the steady-state model for power flow calculation and the dynamic model for constructing the state matrix. The design procedures of the subsynchronous oscillation damping controller (SODC), which is integrated with PI controller at rectifier, consist of three steps:1) to identify the dominant torsional oscillation mode in the AC/DC system;2) to determine the parameters of the SODC for compensating the phase lagging due to the rectifier controller;3) to validate the control parameters and to determine the appropriate gain using a time-domain simulation program. The proposed design method has been tested against two AC/DC systems for validation.

• Journal of Drive and Control
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• v.12 no.2
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• pp.14-20
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• 2015

This paper focuses on the issue of force synchronizing control for the injection servomechanism of injection molding machines. Prior to the controller design, a virtual design model was developed for the injection mechanism with an AC servomotor-ball screw. A synchronizing controller is designed and combined with the PID control to accommodate the mismatches between the real plant and the linear model plant used. Due to the plant uncertainty, the stiffness and the damping of the mechanism were considered. From the tracking control simulations based on the virtual design model, it is shown that a significant reduction in force synchronizing error is achieved through the use of a proposed control scheme.

• Journal of Power Electronics
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• v.13 no.3
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• pp.419-428
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• 2013

The modular multilevel cascade converter (MMCC) is a new family of multilevel power converters with modular realization and a cascaded pattern for submodules. The MMCC family can be classified by basic configurations and submodule types. One member of this family, the Hexverter, is configured as Double-Delta Full-Bridge (DDFB). It is a novel multilevel AC/AC converter with direct power conversion and comparatively fewer required components. It is appropriate for connecting two three-phase systems with different frequencies and driving an AC motor directly from a utility grid. This paper presents the dq model of a Hexverter with both of its AC systems by state-space representation, which then simplifies the continuous time-varying model into a periodic discrete time-invariant one. Then a generalized multivariable optimal control strategy for regulating the Hexverter's independent currents is developed. The resulting control structure can be adapted to other MMCCs and is flexible enough to include other control criterion while guaranteeing the original controller performance. The modeling method and control design are verified by simulation results.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.479-481
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• 1996

This paper describes a simulation model to analyze the dynamic performance of Unified Power Flow Controller which ran flexibly adjust the active and reactive power flow through the ac transmission line. An equivalent circuit to analyze the basic principle for the whole system operation was developed and a control system for the Unified Power Flow Controller was derived using vector control method. A computer simulation model with EMTP code was also conceived to evaluate the performance of the Unified power Flow Controller. The simulation results show that Unified Power flow Controller is very effective for controlling the power flow and damping the subsynchronous resonance in the power system.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.342-345
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• 1999

This paper describes a current regulated PWM boost type rectifier based on modified trapezoidal PWM. Each switch of a converter has no switching for one third period of a fundamental line current. Therefore, the switching loss of the proposed scheme is less than that of the hysteresis current controller. Operating principle is described and controller. Operating principle is described and simulations and experiments are carried out.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.392-396
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• 1994

A method which improves the efficiency of induction motor by controlling the input voltage by the three phase AC voltage controller is studied at the sides of theory and practice. At first, the principle of decreasing the input power and improving the efficiency by adjusting the amplitude of the input voltage according to the load rate is shown. Secondarily, the mathematical model of the three phase AC voltage controller-induction motor system is drived to translate the dynamic characteristics. The validity of the dynamic model is verified by simulation. The new driving method is also proposed, which regulates the rated speed's driving by the speed estimation from the firing angle and the magnitude reverse induced-voltage information. As a result, the digital control system is constructed. Expermintal results show desirable characteristics of proposed system.