• The Transactions of the Korean Institute of Electrical Engineers P
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• v.54 no.3
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• pp.111-118
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• 2005

Since the residential load is an AC load and the output of solar cell is DC power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation, it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper, DC/AC converter is three phase PWM converter with smoothing reactor. And then, feed-forward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.139-143
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• 2001

Recently, the interest on power quality has been hot issue. The equipments cause voltage disturbance and has become more sensitive to the voltage disturbance. This paper deals with 5-Level H-Bridge Line-Inter active Dynamic Voltage Restorer(LIDVR) system. The LIDVR has following advantages in comparison with the DVR with series injection transformer It has the power factor near to unity under normal source voltage, can compensate the harmonic current of the load and the instant interruption, and has the fast response. First, the construction, the operation mode and algebraic modeling of LIDVR are reviewed. And then a voltage controller is proposed to get sinusoidal load voltage with constant amplitude. To find PWM method suitable for H-Bridge converter, two PWM methods are compared and analyzed. Finally, simulation results verify the proposed 5-level H-Bridge LIDVR system.

• Journal of Power Electronics
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• v.11 no.4
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• pp.533-541
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• 2011

The redundant operation of a parallel AC to DC converter via a serial communication bus is presented. The proposed system consists of three isolated CUK power factor correction modules. The controller for each converter is a dsPIC30F6010 microcontroller while a RS485 communication bus and the clock signal are used for synchronizing the data communication. The control strategy of the redundant operation relies on the communication of information among each of the modules, which communicate via a RS485 serial bus. This information is received from the communication checks of the converter module connected to the system to share the load current. Performance evaluations were conducted through experimentation on a three-module parallel-connected prototype, with a 578W load and a -48V dc output voltage. The proposed system has achieved the following: the current sharing is quite good, both the transient response and the steady state. The converter modules can perform the current sharing immediately, when a fault is found in another converter module. In addition, the transient response occurs in the system, and the output voltages are at their minimum overshoot and undershoot. Finally, the proposed system has a relatively simple implementation for the redundant operation.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1253-1255
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• 2003

Since the residential load is an AC load and the output of solar cell is a DC Power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation. it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper DC/AC converter is three phase PWM converter with smoothing reactor. And then, feedforward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.6
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• pp.424-432
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• 2018

This study presents a single-phase single-stage three-level AC/DC converter with a wide controllable output voltage. The proposed AC/DC converter is designed to extend the application of e-mobility, such as electric vehicles. The single-stage converter integrates a PFC converter and a three-level DC/DC converter, operates at a fixed frequency, and provides a wide controllable output voltage (approximately 200-430Vdc) with high efficiencies over a wide load range. In addition, the input boost inductors operate in a discontinuous mode to improve the input power factor. The switching devices operate with ZVS, and the converter's THD is small, especially at full load. The feasibility of the proposed converter is verified by the experimental results of a 1.5 kW prototype.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.865-876
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• 2015

Voltage stability is one of the most critical security issues which has not yet been well resolved to date. In this paper, an analytical method called PQ plane analysis with consideration of the reactive power capability of wind turbine generator and the wake effect of wind farm is proposed for voltage stability study. Two voltage stability indices based on the proposed PQ plane analysis method incorporating the uncertainties of load-increasing direction and wind generation are designed and implemented. Cases studies are conducted to investigate the impacts of wind power incorporation with different control modes. Simulation results demonstrate that the constant voltage control based on reactive power capability significantly enhances voltage stability in comparison of the conventional constant power factor control. Some meaningful conclusions are obtained.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.226-227
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• 2007

The purpose of this study for photovoltaic (PV) generation system is to keep the output power of photovoltaic cells maximized under any weather conditions. In a conventional MPPT (Maximum Power Point Tracking) control method, both voltage and current coming out from PV array have to be fedback. Thus, the system has a complex structure, and may fail to track MPP of PV array when unexpected weather conditions happen. This paper proposes a novel PV Output Senseless (POS) control method to solve the mentioned problem. The main advantage of this method is that the current flowing into load is the only one considerable factor. In case of a huge PV generation system, it can be operated much more safely than the conventional system. To verify this theory, results that compare and analyze the simulated data with experimental data under real weather condition of the manufactured PV generation system are shown in this paper. Authors vividly states that this theory uses constant resistors and variable resistors of DC-DC converter in PV system. Authors emphasize that it is a very useful method to maximize power from PV cells to load with only the feedback of load current. Authors also emphasize that this theory is applicable in case of the PCS in PV power generation system.

• Journal of the Korean Solar Energy Society
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• v.38 no.4
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• pp.55-66
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• 2018

nZEH (net-Zero Energy House) is defined as a self-sufficient energy building where the sum of energy output generated from new & renewable energy system and annual energy consumption is zero. The electricity generated by new & renewable energy system with the form of distributed generation is preferentially supplied to electrical demand, and surplus electricity is transmitted back to grid. Due to the recent expansion of houses with photovoltaic system and the nZEH mandatory by 2025, the rapid increase of distributed generation is expected. Which means, we must prepare for an electricity-power accident and stable electricity supply. Also electricity charges have to be reduce and the grid-connected should be operated efficiently. The introduction of ESS is suggested as a solution, so the analysis of the load matching and grid interaction is required to optimize ESS design. This study analyzed the load matching and grid interaction by expected consumption behavior using actual data measured in one-minute intervals. The experiment was conducted in three nZEH with photovoltaic system, called all-electric houses. LCF (Load Cover Factor), SCF (Supply Cover Factor) and $f_{grid}$ (Grid Interaction Index) were evaluated as an analysis indicator. As a result, LCF, SCF and $f_{grid}$ of A house were 0.25, 0.23 and 0.27 respectively; That of B house were 0.23, 0.23, 0.19, and that of C were 0.20, 0.19, 0.27 respectively.

• Journal of the Korean Institute of Telematics and Electronics
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• v.14 no.1
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• pp.23-28
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• 1977

This paper describes the practical design of a SCR inverter which is suposed to be very much suitable for high frequency induction heating power source. In this design an optimum control technique was applied to maintain constant output power and constant power factor to various heating load by the use of frequency control. Some appreciable characteristics was obtained for some design guide of large ndstrial heating power sources by the test of the 3KHz, 3KW inverter which was designed in this study.

• 전기의세계
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• v.23 no.4
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• pp.60-65
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• 1974

This paper is to study on the pilot work of bi-directional S.C.R. power converter adopted by the method of diode-bridge type circuit. This apparatus acts as a converter when it is used in convering 3-phase a.c source to d.c output, and it can be used as an inverter which recovering surplus d.c power to a.c source when d.c load become active to cause the induced voltage higher than the presetted point of d.c output voltage. At the same time, its d.c voltage varies continuously in the presetted range of positive and/or negative polarity. As a result of test, the AC/DC bi-directional power converter represents maximum converting efficiency of 91% and power factor of 0.98. Furthermore, this converter also can be applied as a cycleconverter by varying the period of gate triggering signal.