• The Transactions of the Korean Institute of Power Electronics
• /
• v.7 no.4
• /
• pp.359-365
• /
• 2002

Three-phase four-wire electrical distribution systems have been widely employed in manufacturing plants, commercial and residential buildings. Due to the nonlinear loads, the neutral conductor carries excessive harmonic currents resulting in wiring failure of the neutral conductor, overloading of the distribution transformer and a voltage drop between the neutral and the ground. This paper proposes a reduced rating active power filter to suppress neutral current harmonics in three-phase four-wire electrical distribution systems. The proposed system is simple in control and the VA rating of the inverter could be significantly reduced since only the fundamental current due to unbalanced loading flows through the inverter switch. The experimental results on a prototype validate the proposed control approach.

• Journal of IKEEE
• /
• v.18 no.1
• /
• pp.159-164
• /
• 2014

This paper targets the development of micro-converter such as a power converter for photovoltaic module. In corresponding to the poor performance of centralized PV system under partial shading, the power converter for single PV module to maximize the energy harvest from PV module. The power converter is constantly tracking the maximum power point of photovoltaic system and increases energy output power. To minimize the quantity of devices and switchs, 320W solar micro-converter is developed using synchronous rectifier. From the basis of these results, through simulations and experiments were verified efficiency.

• Journal of Korean Society of Water and Wastewater
• /
• v.28 no.5
• /
• pp.609-614
• /
• 2014

Researcher of this study improved conventional circle secondary settling basin, through the way such as extend of inlet pipe length, introduction of device for inducting uniforming of flow, keeping of height of sludge interface. Also, we compared conventional circle settling basin to improved circle settling basin the water treatment efficiency. Result of research, when SVI is average 117, improvement rate of SS and BOD were 51.0%, 37.0% approximately compared to conventional settling basin. And when SVI is average 178, improvement rate of SS and BOD were 22.7%, 36.0% approximately. Also when SVI is average 196, improvement rate of SS and BOD were 24.7%, 30.3% approximately. When it's winter, improvement rate of SS, BOD, COD, TN and TP were 20.6%, 17.9%, 13.9%, 13.5%, 12.4% approximately. Therefore, we can be the judge, this improved settling basin can be used as the final settling basin in the waste water treatment plant.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.13 no.6
• /
• pp.461-468
• /
• 2008

This paper presents a novel series connected DC/DC converter and a proper variable phase shift switching method in order to obtain high voltage ratio for fuel cell system. The proposed series connected DC/DC converter has same rectifier and LC filter for DC output voltage, so it can reduce the number of passive devices regardless of the converter number. In the conventional constant phase shift switching method, the proposed series connected DC converters have inverse bias output voltage. In order to overcome this problem, a simple but proper variable phase shift switching method is proposed in the a novel series connected DC/DC converter. In order to verify the proposed system, simulation and experiments are implemented.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.4
• /
• pp.5-10
• /
• 2014

It is possible for the nation's largest flowmeter calibration system in K-water to calibrate flow rate up to $2,700m^3/h$ and diameter 800mm. However, the calibration and measurement capability of K-water's system is not satisfied in comparison with other developed countries. In this study, we find the dominant factors related to the uncertainty of weight and time measurement for gravimetric flowmeter calibration system. As a results of improving the system, the combined standard uncertainty has been improved $1.099{\times}10^{-3}$ to $2.332{\times}10^{-4}$. So calibration and measurement capability got 0.08 percent of the relative expanded uncertainty for maximum flow rate using the coverage factor(k=2).

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.16 no.2
• /
• pp.235-240
• /
• 2010

In order to substitute incandescent lamps, a power supply device for 7W class LED lamps which are environmentally friendly and energy saving is designed LED lamps consist of a multitude of chip LED connected in parallel and series. 11ms it is necessary to supply LED lamps with DC voltage and current. However, when LED lamps are in use, they are connected directly to AC 220V. This is why we need to have AC/DC, DC/DC power converters including a control system of voltage and current. For this, a transformerless and simple LED lamp driver is designed 조ich can control the current and output voltage for LED string of LED lamp.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.6 no.1
• /
• pp.64-73
• /
• 2001

This paper presents a Zero Voltage and Zero Current Switching (ZVZCS) 3-Level DC/DC converter. This converter overcomes the drawbacks presented by the conventional Zero Voltage Switching(ZVS) 3-Level converter, such as high circulating energy, severe parastic ringing on the rectifier diodes, and limited ZVS load range for the inner switches. The converter presented in this paper uses a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switches. Additionally, the converter uses an energy recovery snubber to reset the primary current during the free-wheeling stage to achieve ZCS for the inner switches. The proposed converters are analyzed and verified on 6kW, 39kHz experimental prototype.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.20 no.4
• /
• pp.375-387
• /
• 2015

This study investigates an economic and highly efficient power-converter topology and its modulation scheme for 60 kW rapid EV charger system. The target system is a three-phase three-switch buck-type rectifier topology. A new carrier-based PWM scheme, which is characterized by simple implementation using logic gates, is introduced in this paper. This PWM scheme replaces the diode rectifier equivalent switching state with an active switching state to produce the same effective current flowing path. As a result, the distortion of input current during the polarity reversal of capacitor line voltage can be mitigated. The proposed modulation technique is confirmed through simulation verification. The proposed modulation technique and its implementation scheme can expand the operation range of the three-phase three-switch buck-type rectifier with high-quality AC input and capacitor ripple current.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.13 no.1
• /
• pp.15-21
• /
• 2008

This paper presented a actual conditions on a false-tripping of ELB(Earth Leakage Breakers) and an assessment of the harmonics due to non-linear electronic equipment such as personal computers, rectifier, electric furnace and test equipments in factory electrical installation. Actual conditions on a failure of ELB were surveyed and analyzed by making up a question to safety managers of factory electrical installation. Also, power quality measurements such as harmonic currents, voltage and current waveform and current imbalance were made at various factory electrical installation where nuisance tripping of ELB is often occurred. The results of this study can be used in making decisions regarding cause of ELB trip and operating and tripping characteristics test of ELB when subjected to distorted current waveform.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.4 no.3
• /
• pp.268-274
• /
• 1999

The problem of power factor and hmmonics are occurred in convelter system which used to SCRs and diodes as p power semiconductor devices. IGBT power device with selh:ommutation type was solved that problem. maintain the l input line current with sinusoidal wave CUlTent of input power source voltage. It was estimated that improvement of t transient state characteristics with feedfolward compensator added in the diode rectifier with single phase voltage type i inverter was used to simulation load. As a results it was verified that the transient state characteristics with voltage t type PWM convelter control was improved.