Hyung-Lae Baek

A study on the tracking photovoltaic system by program type

In order to increase the efficiency of PV system, it is generally used three method the first is the increasing the efficiency of solar cell, the second is the energy conversion system included MPPT control algorithm and the third is the using solar tracking system. In solar tracking system, it is used DC motors, special motors like step motors, servo motors, real time actuators, to operate moving parts. DC motors are normally used to operate solar tracking system but it is highly expensive to maintain and repair. In this paper, it is proposed 150 W solar tracking system. Proposed system designed as the normal line of the solar cell always runs parallel the ray of the sun. In this paper proposed system can minimize the solar cosign loss of the photovoltaic system

Performance analysis of the DTC using a closed loop stator flux observer for induction motor in the low speed range

Direct torque control (DTC) of an AC motor has the fast torque and flux dynamic responses even though it has very simple scheme to implement. However, DTC do not show good performance at low speed range with conventional open loop stator flux observer when stator resistance varied. Therefore, authors propose a new nonlinear stator flux observer in order to estimate the stator flux of induction motor at low speed and show its simulation results.

Speed control of AC servo motor using neural networks

Recently intelligent control has received increased attention in various applications. With PID controllers, it is difficult to obtain gain suitable to the load because of disturbances, parameter variations and measurement noise. In order to reduce mechanical parameter variations, and to obtain good dynamic performance, PID controllers and neural network controllers for AC servomotor control are investigated. The microprocessor provides an output to the difference in command. The servo system improves the characteristics of speed control. When the motor is running at the same speed as set by the reference signal, the speed encoder also provides a signal of the same frequency. From the viewpoint of wide control range, a good dynamic performance and a cost effective approach, the NNE of an adaptive neural network controller is used to identify the parameters and characteristics of the AC servomotor. To train the controller, the weights are dynamically adjusted using the backpropagation algorithm. Neural networks are used so PID control can control, efficiently, the speed of the AC servomotor. Finally experimental results prove the excellent performance of this control system.

Direct torque control for the 4-phase switched reluctance motor drives

This paper presents a novel control method for the sensorless four phase switched reluctance motor drives, i.e. 8 stator and 6 rotor. The sensorless control is based on direct torque control with direct flux compensation (DFC) for switched reluctance motor drives. The use of direct torque control, implemented in AC drives with a varies degree of success, has yet been completely applied for SRM especially 8/6, 4-phase SRM. Direct torque control strategy implemented to control unit, well known advantages such as simple and robust structure, wide torque speed range and no maintenance. In this paper, we propose a novel way to utilize the 8/6 4 phase switched reluctance motor and the paper then explains the algorithm to be employed in new DTC scheme in SRM drives with simulation results are presented.

Performance evaluation and analysis of 50kW grid-connected PV system

This paper summarizes the results of these efforts by offering a photovoltaic system structure in 50 kW large scale applications installed in Chosun University dormitory roof. The status of PV system components, are inter-connection and safety equipment monitoring system will be summarized as this article. This describes configuration of utility interactive photovoltaic system which generated power supply for dormitory. In this paper represent 50 kW utility PV system examination result.

A novel detecting noise reduction scheme for voltage-regulated current-fed power filter

Active power filters have been developed to solve the harmonics disturbance problems on power system networks. Particularly for current-type active power filters, a voltage regulation scheme is considered to control the voltage of capacitor at the input side of a nonlinear load. For precise control, the value of voltage drop at the AC side must be included. Because of the reactance of the filter, external noises are added to the detected voltage drop signal and hence the resultant signals will be seriously distorted, particularly where an electronic differentiator is used. To reduce these noises, a novel detected noise reduction scheme with an observer based algorithm is proposed. The designed observer algorithm is applied and then investigated by digital simulation. Also the experimental results are shown to verify the validity of proposed scheme.

A study on the reduction of in-rush current for energy saving of single phase induction motor

In this paper, an analog controller is proposed to reduce in-rush current that happens during starting of a single phase induction motor within 200% of rated current depending on an international standard. The soft start method is used as the main conventional method that reduces inrush current and controls the input current through the main winding control. Capacitor starting of a single phase induction motor requires large starting torque. If the input electric power is less, the starting torque decreases and because starting time is delayed, electric power loss increases. Therefore, this paper discusses improved reduction of starting torque at main winding control which controls the auxiliary winding that is paralleled with the main winding that uses an electrical starting switch, and leads to energy saving during starting.

Starting characteristics by auxiliary winding sequence control for a single-phase induction motor

The most common method of starting a single-phase induction motor (SPIM) is to install a starting condenser and a centrifugal switch in series with the auxiliary winding. Even though this capacitor start method is embodied simply, it is feasible because of motor failure from malfunction of the centrifugal switch and the starting condenser. Moreover, it is hard to improve the performance characteristics of the SPIM. In this paper, the voltage and phase angle sequence control strategy of the auxiliary winding of the SPIM is employed to eliminate the centrifugal switch and the starting condenser. The proposed control system is superior to a conventional system in the starting performance of SPIM. Finally, the improved starting characteristics of the SPIM is obtained with this strategy through simulation and experimental results.