• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1864-1869
• /
• 2003

A novel piezoelectric micropump using active check valves in place of conventional passive check valves in inlet and outlet has been proposed and investigated. It actively controls open/close motion of check valves using piezoelectric actuator for expansion/contraction of pump chamber. In this paper, bi-directional flow characteristics and load characteristics are experimentally investigated using an adequate timing control for valve closing motion with a prototype micropump fabricated with the effective size of $17{\times}8{\times}11mm^{3}$. From the experimental results, it is ascertained that optimal values of phase shift against voltage to drive pump chamber for realization of a miniaturized but powerful micropump, are $15^{\circ}$ in inlet check valve and $195^{\circ}$ in outlet. Based on the obtained results, a sheet-type active shuttle valve that has a unified valve-body for inlet and outlet check valves is proposed. A micropump with the effective size of $10{\times}10{\times}10mm^{3}$ is fabricated and basic characteristics are experimentally investigated.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.6
• /
• pp.2971-2978
• /
• 2013

Recently, with the world-wide issues about global warming and CO2 reduction, a number of distributed generations(DGs) such as photovoltaic(PV) and wind power(WP), are interconnected with the distribution systems. However, DGs can change the direction of the power flow from one-direction to bi-direction, and also change the direction and amount of fault current of existing distribution systems. Therefore, it may cause the critical problems on the power quality and protection coordination. This paper proposes an operation algorithm for bi-directional protection coordination using and apply it for the evaluation system for protection coordination. From the simulation results It is found that the proposed method is more effective and convenient than existing method.

• Proceedings of the KIPE Conference
• /
• 2015.07a
• /
• pp.389-390
• /
• 2015

This paper proposes renewable energy system related with flow battery system which is divided into two system, converter and inverter. The Interleaved Boost Converter circuit was used for DC - DC Converter and Full-Bridge Inverter was used for Grid connected Inverter. This paper design each system and uses methods to operate converter and inverter in high efficiency.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.6 no.2
• /
• pp.14-21
• /
• 2009

The typical hydraulic hoisting system of the rack-bar type sluice gate is composed of a hydraulic supply unit using an uni-directional pump, a direction control valve, a hydraulic motor, a counter balance valve, and flow control valves. Here, the hydrostatic transmission is applied to the hoisting system of rack-bar type sluice gate to simplify the operation of gate such that the upward and downward direction of gate is simply controlled by the direction of pump rotation. The new hydraulic hoisting system is composed of a bi-directional pump, a hydraulic motor, two counter balance valves, two check valves, two pilot-operated check valves, two relief valves and a shuttle valve. The characteristics of a suggested system are analyzed by computer simulations.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.7 no.4
• /
• pp.15-22
• /
• 2010

The typical hydraulic hoisting system of the rack-bar type sluice gate is composed of a hydraulic supply unit using an uni-directional pump, a direction control valve, a hydraulic motor, a counter balance valve, and flow control valves. Here, the hydrostatic transmission is applied to the hoisting system of rack-bar type sluice gate to simplify the operation of gate such that the upward and downward direction of gate is simply controlled by the direction of pump rotation. The new hydraulic hoisting system is composed of a bi-directional pump, a hydraulic motor, a counter balance valve, two check valves, two pilot-operated check valves, two relief valves and a shuttle valve. The characteristics of a suggested system are analyzed by computer simulations and experiments.

• Transactions of the Korean hydrogen and new energy society
• /
• v.28 no.4
• /
• pp.407-418
• /
• 2017

Battery heat management is essential for high power and high energy battery system because it affects its performance, longevity, and safety. In this paper, we investigated the temperature of the 18650 Lithium Ion Battery Module used in a Energy Storage System (ESS) and the cooling method to minimize cell-to-cell temperature variation of battery module. For uniform temperature distribution within a battery module, the flow direction of the coolant in a battery module has been changed according to the time interval, and studied the effect of the cooling method on the temperature uniformity in a battery module which includes a number of battery cells. The experimental results show that bi-directional battery cooling method can effectively reduce the cell-to-cell temperature variation compared with the one-directional battery cooling. Furthermore, it is also found that bi-directional battery cooling can reduce the maximum temperature in a battery module.

• Journal of the Korea Convergence Society
• /
• v.2 no.2
• /
• pp.35-45
• /
• 2011

Recently, with the increasement of the interest about global warming, pollutions, and so on, a number of distributed generations(DGs) such as photovoltaic(PV) and wind power(WP), are interconnected with distribution systems. However, installing of DGs makes power flow changes such as directions, one-direction to bi-direction, and increasing/decreasing of fault current. Therefore, it may cause the critical problems. This paper proposes an evaluation algorithm for bi-directional protection coordination and presents an evaluation system for protection coordination based on this algorithm. Additionally, the result shows that the existing method may cause critical problems, and also the effectiveness of proposed method is verified.

• International Journal of Control, Automation, and Systems
• /
• v.6 no.5
• /
• pp.670-676
• /
• 2008

While the matrix converter has many advantages that include bi-directional power flow, a size reduction, a long lifetime, and sinusoidal input currents, it is vulnerable to the input voltage disturbances, because it directly exchanges the input voltage to the output voltage. So, in this paper, a critical evaluation of the effect of various abnormal voltage conditions like unbalanced power supply, balanced non-sinusoidal power supply, input voltage sags and short time blackout of power supply on matrix converter fed induction motor drives is presented. The operation under various abnormal conditions has been analyzed. For this, a 230V, 250VA three phase to three phase matrix converter (MC) fed induction motor drive prototype is implemented using DSP based controller and tests have been carried out to evaluate and improve the stability of system under typical abnormal conditions. Digital storage oscilloscope & power quality analyzer are used for experimental observations.

• Proceedings of the KIPE Conference
• /
• 2014.11a
• /
• pp.25-26
• /
• 2014

Renewable energy sources such as wind and solar power are free and can be easily harvested everywhere. However, one of the biggest problems when using this kind of energy source is how to increase the efficiency of power conversion system. This paper introduces a modified 3-phase inverter in order to increase the power conversion efficiency. By adding 3 bi-directional switches at output of the inverter, the current flow back DC source during zero state is prevented to minimize leakage current, so that the efficiency of whole system is increased. The proposed topology also improves the power quality to satisfy the total harmonics distortion (THD) requirement. In order to verify the effectiveness of the proposed topology, simulation results are carried out using Simulink in MATLAB.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2001.05a
• /
• pp.21-27
• /
• 2001

This paper describes numerical analysis of the impulse turbine with fixed guide vanes, a high performance bi-directional air turbine having simple structure for wave energy conversion. The numerical analysis of the 2-dimensional incompressible viscous flow based on the full Reynold-averaged Navier-Stokes equations which was made to investigate the internal flow behavior. Numerical results are compared with experimental data obtained by T.Setoguchi laboratory. As a result, as suitable choice of design factor has been clarified with the understanding of the internal flow from the numerical analysis.