• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.229-230
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• 2011

This paper presents deadbeat controller for output current in the utility-interactive inverter. The time delay related with deadbeat controller is compensated by using prediction control. By computer simulation and experiment, the dynamic characteristics of deadbeat controller is verified.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.11-14
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• 2007

In recent years, installation of the new and renewable energy system is rapidly increasing. Because the new and renewable energy system is a practical distributed generation system to save energy resources and to keep environments clean. Conventional single-phase utility interactive inverter controls output current by using PI current controller. However, this method is insufficient to suppress harmonic current resulted from nonlinear loads in grid line. In this paper, in order to suppress periodic waveform distortion and improve THD(Total Harmonic Distortion), new type current controller added a parallel repetitive controller is proposed and then performance of the proposed controller was verified with computer simulation.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.238-243
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• 2003

The solar cells should be operated at the maximum power point because its output characteristics are greatly fluctuated on the variation of insolation, temperature and load. The output power of solar cell is DC, therefore it is necessary to install an inverter among electric power converts. The inverter have to supply a sinusoidal current and voltage to the load and the interactive utility line. In the paper, the proposes a photovoltaic system designed with a step up chopper and single phase PWM voltage source inverter. Synchronous signal and control signal was processed by microprocessor for stable modulation. The step up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power point of solar cell without any influence on the variation of insolation and temperature because solar cell has typical dropping character. The single phase PWM voltage source inverter consists of complex type of electric power converter to compensate for the defect, that is, solar cell cannot be developed continuously by connecting with the source of electric power, from 10 to $20\%$. The single phase PWM voltage source inverter operates in situation that its output voltage is in same phase with the utility voltage. The inverter supplies an ac power with high factor and low level of harmonics to the load and the utility power system.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.215-217
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• 2002

In this paper, a new converter for utility interactive photovoltaic system is proposed, the conventional utility interactive photovoltaic system is composed of a PWM inverter and a DC converter. However, the increased switching loss and the high frequency switching noise become a problem. the control accuracy of the system is made to lower by the dead time of the switching devices. and it becomes a cause of the lower conversion efficiency. In order to resolve those problems, we applied a non- dissipative snubber circuit to a converter, which generates the single phase absolute value of sinusoidal current. the converter consists of two switching devices and one capacitor which constitute a non-dissipative snubber circuit. the proposed circuit is very useful to minimize and increase efficiency, when it is used to an utility interactive photovoltaic system. it is confirmed by simulation that the proposed converter for new photovoltaic system has stable operation and good output.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.1
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• pp.72-78
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• 2006

Distributed generation (DG) systems go to intentional islanding operation to back up private emergency loads when the main grid is out of electric power. Conventional utility interactive inverters normally operated in current control mode in DG system must change their operation mode into voltage control mode to ensure stable voltage source to the emergency loads when intentional islanding operation occurs. During the transfer between current control mode and voltage control mode, serious transient problem may occur on the output terminal voltage of the utility interactive inverter. This paper proposes reasonal inverter topology and its control algorithm for seamless transfer of DG systems in intentional islanding operation. Filter design guide line and data for a LCL filter that is appropriate for the proposed control algorithm are also presented by the authors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.317-324
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• 2007

Most conventional hybrid systems using renewable energy sources have been applied for stand-alone operation, but Utility-interface may be an useful and viable option for hybrid systems. Grid-connected operation may have benefits such as reduced losses in power system distribution, utility support in demand side management, and peak load shaving. This paper addresses power control and dynamic performance of a grid-connected PV/wind/BESS hybrid system. At all times the PV way and the wind turbine are individually controlled to generate the maximum energy from given weather conditions. The battery energy storage system (BESS) charges or discharges the battery depending on energy gap between grid invertger generation and production from the PV and wind system. The BESS should be also controlled without too frequently repeated shifts in operation mode, charging or discharging. The grid inverter regulates the generated power injection into the grid. Different control schemes of the grid inverter are presented for different operation modes, which include normal operation, power dispatching, and power smoothing. Simulation results demonstrate that the effectiveness of the proposed power control schemes for the grid-interactive hybrid system.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.312-319
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• 2014

When distributed generation such as a wind power system is connected to the grid, it should meet grid requirements like IEEE Std. 1547, which regulates the anti-islanding method. Since the islanding may cause damage on electrical equipments or safety hazards for utility line worker, a distributed generation should detect it as soon as possible. This paper proposes a hybrid anti-islanding method coupled with the active and passive detection methods. To enhance the harmonic extraction capability for an active harmonic injection method, cascaded second-order band-pass filter and signal processing scheme are employed. Simulation and experiments are carried out under the islanding test condition specified in IEEE Std. 1547. Passive over/under voltage and over/under frequency methods are combined with the active method to improve the detection speed under certain condition. The simulation and experimental results are presented to verify that the proposed hybrid anti-islanding method can effectively detect the islanding.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.360-369
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• 2008

The solar cells should be operated at the maximum power point because its output characteristics were greatly fluctuated on the variation of insolation, temperature and load. It is necessary to install an inverter among electric power converts by means of the output power of solar cell is DC. The inverter is operated supply a sinusoidal current and voltage to the load and the interactive utility line. In this paper, the proposes a photovoltaic system is designed with a step up chopper and single phase PWM voltage source inverter. Synchronous signal and control signal was processed by one-chip microprocessor for stable modulation. The step up chopper is operated in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power point of solar cell without any influence on the variation of insolation and temperature for solar cell has typical dropping character. The single phase PWM voltage source inverter is consists of complex type of electric power converter to compensate for the defect, that is, solar cell cannot be develop continuously by connecting with the source of electric power for ordinary using. It can be cause the efect of saving electric power, from 10 to 20%. The single phase PWM voltage source inverter operates in situation, that its output voltage is in same phase with the utility voltage. The inverter are supplies an ac power with high factor and low level of harmonics to the load and the utility power system.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.236-238
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• 1999

This paper presents a model and analysis results of 3 phase utility interactive photovoltaic power generation system. The control system is composed of feed forward, feedback and PID system. The voltage source inverter system provides sinusoidal PWM at current for the loads of utility system. A phase to ground fault and 3 phase fault are analyzed, and the results are discussed.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1050-1052
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• 2000

An investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential system (3-5kW) that interface with a 220V single phase utility connection. As the result of this investigation. a 3kW high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage. Even though the high frequency link system used more power semiconductors, a net size, weight, and parts cost saving result compared to the other systems due to elimination of 60Hz transformer.