• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.97-104
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• 2004

As a device that returns surplus energy, regenerated from trains to d.c. source, to a.c. system and reuses it, the thyristor Inverter has been widely used. Because the conventional thyristor inverter is a unidirectional phase-controlled device, it Is Impossible to control the power factor of its output. Moreover, harmonics emission is high and it needs to take a additional filter. In this paper, to solve the problems stated above, the inverter, which can control real and reactive power by adopting IGBT modules as switching elements and being controlled by means of space vector PWM, is developed. Considering high economical efficiency and reliability in order to apply to the system for commercial use, the developed inverter is equipped with fully digital control system and low pass filter, and reduces harmonics and has compact size. The detail description about the developed inverter is stated in various respects: design criteria, technical description, power circuits, control techniques, the developed system, test results, etc.

• Journal of Industrial Technology
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• v.18
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• pp.323-328
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• 1998

A current controlled VSI-PWM rectifier and inverter with capacitor dc link is regarded as one of the most promising structures for three-phase to three-phase to three-phase power conversion. This type of converter normally requires twelve switches for a rectifier and inverter composed of self turn-off switch such as a bi-polar transistor or IGBT with an anti-parallel diode. In this paper, a new three-phase to three-phase converter for ac motor drives is proposed. The proposed converter employs only eight switches and has the capability of delivering sinusoidal input currents with unity power factor and bidirectional power flow. This paper describes the feasibility and the operational limitations of the proposed structure. A mathematical model of the system is derived using generalized modulation theory and experimental results for steady state and dynamic behavior are presented to verify the developed model.

• Journal of the Korean Society of Radiology
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• v.5 no.3
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• pp.127-134
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• 2011

In this paper we propose an improved PV generation systems. Improved systems for temperature and humidity controlled heating and air conditioning offers a pleasant environment within the building, set up chopper and consists of a PWM voltage type inverter. The proposed system is stable modulation for a one-chip microprocessor using the synchronous signal and control signals was treated. The proposed system is a PWM voltage type inverter and phase of the synchronous to the grid voltage to detect the system voltage and inverter output to drive the statue, so surplus power to connection was able to, certain buildings such as buildings or hospitals, temperature and humidity sensor is applied to the good dynamic characteristic could be obtained. In addition, the system was applied to the high power factor and low-frequency harmonics by maintaining the output load and grid to power to be supplied to a stable control could get a good result.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.2
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• pp.53-57
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• 2012

The mathematical model of a three-phase voltage source pulse-width modulation (PWM) DC/AC inverter is non-linear, and in view of the traditional linear control strategy it can not meet the requirements of designing a high-performance inverter. What's more, when the loads are not pure resistive loads, the inverter further requires that the controller possess high-performance. This paper proposes a nonlinear control strategy for the inverter called Passivity-based Control. We can alter the inverter model in three-phase abc coordinate to two-phase synchronous rotating dq coordinate for establishing the port-control Hamiltonian (PCH) model for this system. We can control the distribution of energy in the system to achieve the control aim. Simulation results show that the passivity-based control method can make this system possess a level of high-performance that is both robust and dynamic.

• Journal of information and communication convergence engineering
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• v.6 no.4
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• pp.417-420
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• 2008

Solar electric systems have very little impact on environment, making them one of the cleanest power-generating technologies available. While they are operating, PV systems produce no air pollution, hazardous waste, or noise, and they require no transportable fuels. In PV system design, the selection and proper installation of appropriately-sized components directly affect system reliability, lifetime, and initial cost. In this research, we have studied the PWM(Pulse Width Modulation) signals. I proposed an efficient photovoltaic power interface circuit incorporated with a DC-DC converter and a sine-pwm control method full-bridge inverter. In grid-connected solar power systems, the DC-DC converter operates at high switching frequency to make the output current a sine wave, whereas the full-bridge inverter operates at low switching frequency which is determined by the ac frequency. Thus, it can reduce the switching losses incurred by the full-bridge inverter. Full-bridge converter is controlled by using microprocessor control method, and its operation is verified through computer aided simulations.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.148-150
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• 1988

The output characteristics of VSI by transistor depend upon bias signal with drive circuit. As the CTI is one of the VSI, takes case PWM output voltage. This Inverter operation is based upon position and negative of sinusoldal PWM signal by carrier triangular wave and compared sine one. Besides, the Inverter operation system required digital signal for microprocessor, sampling method of Inverter driver signals study for get rid of generated signal is error. In the paper, the method of 3 level PWM signal for CTI was studied. This method of signals depend upon caculated switching position of natural sampling with $10^{-6}$ modulation error for time flowchart programs.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1995.10a
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• pp.101-104
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• 1995

The linear control of DC Link voltage in PWM inverter is very importent to estimate the goodness of PWM method. In motor control system, for the maximum torque on full region operating, the whole of DC Link voltage region must be used. 3 phase sinusoidal PWM inverter has a low efficienty at the using of output voltage. according to make better the efficiency, new improved PWM control method is proposed. The results of experimentation and simulation are included to verify the validity of this method.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.3
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• pp.239-246
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• 2015

A novel control method of a three-phase PWM inverter with LC filter is proposed. The transfer function of LC filter is the same as that of second-order low pass filter(LPF), which has a zero damping ratio. A simple method of implementing second-order LPF with damping ratio is to add a resistor in an LC circuit. However, in a real power system, adopting damping resistors is impractical because it results in losses proportional to the square of the current flowing through the resistors. Instead of inserting resistors, the proposed control strategy utilizes the measured capacitor voltages to control the oscillation of LC circuit. The overall transfer function of the proposed method is the same as a second-order LPF, and its damping ratio is controllable via control variables. The current controller can have overshoots caused by LC filter. Improved current controller is implemented by an equivalent second-order of LC filter. A 7.5 kVA PWM converter and a PWM inverter with a 5.5 kW induction motor are set up to verify the proposed control algorithm. Test waveforms are also presented to verify the proposed LC filter control algorithm.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.3
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• pp.328-334
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• 1999

A fish pump makes very important roles in an automation system of an aquaculture farm, thus it has been used widely in order to transfer fishes from one place to the other place automatically. In spite of its significant roles, the efforts for developing performance and promoting efficiency of the fish pump are not sufficient yet. In this paper, a method which makes the fish pump automation system is suggested. Automation of the fish pump can be accomplished by using variable voltage and variable frequency inverter system including induction motors. Especially, very simple logic to generate Pulse width Modulation(PWM) wave to control induction motor efficiently and three steps speed control method to regulate liquid quantity of the fish pump simply are suggested. Owing to the simplifies speed control and PWM wave generation technique, a cheaper microprocessor, 80C196KC, than a digital signal Processor(DSP) can be used to operate control algorithm in induction motor systems for real time control Also, a new idea of remote control for the simplifies novel inverter system by Programmable logic Controller(PLC) without special output unit, digital to analog converter(D/A), is suggested in this paper. Consequently the function of reliability, availability and serviceability of the fish pump system are developed. It will be expected to contribute expanding of application of the fish pump in aquaculture farms because the system can reduce energy consumption and some difficulties according to manual operation prominently.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.328-335
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• 1999

Three phase full bridge rectifier has been used to obtain dc voltage from three phase ac voltage source. The rectifier system has drawbacks that power factor is low and power flow is unidirectional. Therefore, when dc voltage increases due to regeneration of power the dynamic resister for dissipation of regeneration power must be installed. But three phase PWM converter can be controlled to operate with unity power factor and bidirectional power flow. Therefore when the PWM converter is used as do supply system, the dissipating resistor is not necessary. On this thesis, in order to design a controller having good performance, the hee phase PWM converter is completely modeled by using circuit DQ-transformation and thus a general and simple instructive equivalent circuit is obtained; the inductor set becomes a second order gyrator-coupled system and three phase inverter becomes a transformer as well. Under given phase angle(${\alpha}$) and modulation index(MI) of the three phase inverter, the dc and ac characteristics are obtained by analysis of the transformed equivalent circuit The validity of the equivalent circuit is confirmed through PSPICE simulation. And based on the dc and ac characteristics a controller with unity power factor is proposed.