• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.11
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• pp.1827-1834
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• 2016

This paper presents a high efficient generator with PM(Permanent Magnet) exciter. The proposed PM exciter for the generator can produce a linear output voltage according to the engine speed. This output voltage is directly used to control the field current of the generator to adjust the generator output voltage. In the proposed generator system, since the field winding current can be supplied by the PM exciter, the generator can self-start without any battery or an external power supply due to the low residential flux. Furthermore, the operating efficiency of the generator is higher than a conventional winding exciter. The main problem of the proposed generator system, the field winding current controller has to be embedded inside the generator, and it rotates according to the generator shaft. In this paper, the proper embedded current controller is designed for the proposed generator system. Due to the embedded controller cannot be connected to the outside the generator controller, the measured instantaneous output voltage of the generator is transferred by the photo isolated communication using shaft aligned infrared transmitter and receiver to keep the constant generator output voltage. In this paper, 10kW, 380V engine generator with PM exciter and the embedded DAVR(Digital Automatic Voltage Regulator) are described. The proposed high efficiency generator is simulated and tested to verify the effectiveness.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.2
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• pp.103-107
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• 2009

PI controller is widely used as voltage control system of generator. However when a generator system has various characters of continuance, a new PI parameter decision for accurate control is a hard task as method of solving this problem, in this paper, the method to generator voltage control using Neural Network self adaptive control is presented. A property continuous feedback control gain of voltage control system is decided by a rule of delta learning. The function of proposed control method is verified by voltage control experiment results of DC generator.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.74-75
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• 2017

This paper proposes a control scheme of the voltage ripple suppression for the permanent magnet exciter generator. The output voltage of the permanent magnet excitation generator is affected by the field current, load current and the engine speed. The engine speed can be controlled by the governor. But, the actual frequency is changed at the starting and a sudden load variation. As a result, output voltage overshoot and undershoot can decrease the power quality in the grid system. The proposed control scheme uses a frequency factor to control the field current of the generator for the voltage ripple reduction. Because of the linkage flux is proportional to the frequency, the instantaneous frequency can consider the linkage flux. The proposed control method shows the improved control performance for the permanent magnet excitation generator through simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.3
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• pp.286-293
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• 2004

This paper presents the result of a study on the starter control for a turbo generator. Because a starter in gear box type turbo-generator system is composed of gearbox and brush DC motor, it should be replaced with High Speed Generator(HSG)) in HSG type Turbo-generator. There-ore, it is necessary to design a new starting algorithm and starter. In gearbox type system, brush DC motor is rotated to the designed speed using low voltage-high current battery power. After brush DC motor speed is increased to several times by gearbox, gas turbine engine can be rotated to designed starting speed. If we implement a starter with High Speed Generator(HSG), it is necessary to drive high-speed generator to high-speed motor. High-speed generator with permanent magnet on rotor has a low leakage inductance fur driving high-speed rotation, and it is necessary high DC link voltage for inverter when High-speed generator is driven to high speed. This paper presents result of development of the boost converter for converting high voltage DC from low battery voltage and design of the inverter for controlling a high frequency current to be injected to motor winding. Also, we show performance of the designed starter by driving the turbo generator.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.580-582
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• 2008

The object of this paper is develope the PC based controlled high voltage power supply and studies 1.2kW(120kV, 10mA) pulse power X-ray generator possible to adapt fluoroscopy of Dental CT X-ray generator and industrial X-ray pulse power equipment. The developed pulse power X-ray generator consisted of mono-block tank include X-ray tube and high voltage X-ray power supply circuit and high voltage control unit with RS232C/422 communication port. The PC control program of pulse power X-ray generator uses LabVIEW, and the size of high voltage transformer and high voltage generator is minimized by high voltage high frequency inverter has 100kHz switching frequency. Also this paper shows result of X-ray tube voltage and tube current correspond to variable load.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2002.11a
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• pp.151-156
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• 2002

The output voltage of Synchronous Generator is regulated constantly by field current control in excitation system. A synchronous generator is equipped with an automatic voltage regulator(AVR), which is responsible for keeping the constant output voltage under normal operating conditions about various levels. High frequency PWM converter (Current Mode Control Buck converter) type excitation system for synchronous generator is able to sustain output voltage level properly when the fault condition happened. This paper deals with the design and evaluation of the excitation system controller for a synchronous generator to improve the steady state and transient stability. The simulation and experimental results show that the proposed excitation system is improve the respons time by the AVR(automatic voltage regulator) of 50kW synchronous generator that is applied the current mode control excitation system.

• Journal of Power Electronics
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• v.10 no.5
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• pp.538-547
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• 2010

This paper deals with a stand-alone wind energy conversion system (WECS) with an isolated asynchronous generator (IAG) and voltage and frequency (VF) control feeding three-phase four-wire loads. The reference generator currents are estimated using the instantaneous symmetrical component theory to control the voltage and frequency of an IAG system. A three-leg voltage source converter (VSC) with an isolated star/delta transformer is used as an integrated VSC. An integrated VSC with a battery energy storage system (BESS) is used to control the active and reactive powers of the WECS. The WECS is modeled and simulated in MATLAB using the Simulink and the Sim Power System (SPS) toolboxes. The proposed VF controller functions as a voltage and frequency regulator, a load leveler, a load balancer and a harmonic eliminator in the WECS. A comparison is made on the rating of the VSC with and without ac capacitors connected at the terminals of an IAG. Simulation and test results are presented to verify the control algorithm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.1
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• pp.36-41
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• 2011

Medical X-ray has been brought many changes according to the rapid development of high technology. Especially, for high-voltage generator which is the most important in X-ray generation the traditional way is to use high-voltage electric transformers primarily. However, since it is large and heavy and the ripple rate of DC high-voltage applied to X-ray tube is too big, it has a disadvantage of low X-ray production efficiency. To solve these problems, the studies about high-voltage power supply are now proceeding. At present, the high-voltage generator that generates high-voltage by making high frequency using inverter control circuit consisting of semiconductor device is mainly used. High-voltage generator using inverter has advantages in the diagnosis using X-ray including high performance with short-term use, miniaturization of power supply and ripple reduction. In this study, the X-ray high-voltage device with inverter type using pulse width modulation scheme to the control of tube voltage and tube current was designed and produced. For performance evaluation of produced device, the control signal analysis, irradiation dose change and beam quality depending on the load variation of tube voltage and tube current were evaluated.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1261-1268
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• 2013

This study proposes a voltage and reactive coordinative control strategy with distributed generator (DG) in a distribution power system. The aim is to determine the optimum dispatch schedules for an on-load tap changer (OLTC), distributed generator settings and all shunt capacitor switching on the load and DG generation profile in a day. The proposed method minimizes the real power losses and improves the voltage profile using squared deviations of bus voltages. The results indicate that the proposed method reduces the real losses and voltage fluctuations and improve receiving power factor. This paper proposes coordinated voltage and reactive power control methods that adjust optimal control values of capacitor banks, OLTC, and the AVR of DGs by using a voltage sensitivity factor (VSF) and dynamic programming (DP) with branch-and-bound (B&B) method. To avoid the computational burden, we try to limit the possible states to 24 stages by using a flexible searching space at each stage. Finally, we will show the effectiveness of the proposed method by using operational cost of real power losses and voltage deviation factor as evaluation index for a whole day in a power system with distributed generators.

• Journal of Power Electronics
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• v.8 no.1
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• pp.10-22
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• 2008

The wind-driven doubly fed induction generator (DFIG) is currently under pressure to be more grid-compatible. The main concern is the fault ride-through (FRT) requirement to keep the generator connected to the grid during faults. In response to this, the paper introduces a novel model and new control scheme for the DFIG. The model provides a means of direct stator power control and considers the stator transients. On the basis of the derived model, a robust linear quadratic (LQ) controller is synthesized. The control law has proportional and integral actions and takes account of one sample delay in the input owing to the microprocessor's execution time. Further, the influence of the grid voltage imperfection is mitigated using frequency shaped cost functional method. Compensation of the rotor current pulsations is proposed to improve the FRT capability as well as the generator performance under grid voltage unbalance. As a consequence, the control system can achieve i) fast direct power control without instability risk, ii) alleviation of the problems associated with the DFIG operation under unbalanced grid voltage, and iii) high probability of successful grid FRT. The effectiveness of the proposed solution is confirmed through simulation studies on 2MW DFIG.