• Proceedings of the KIEE Conference
• /
• 2000.07b
• /
• pp.1267-1269
• /
• 2000

New switching signal pattern for four switches is proposed to prevent the shortage of PWM ac choppers. In the proposed technique, four signals to four power switches are generated without current transformer, while the conventional technique requires sensing the polarity of input voltage by voltage comparator and checking the direction of input current by the current transformer. The signal circuit built by the proposed technique is simple, and reduces also the switching loss.

• Proceedings of the KIPE Conference
• /
• 2002.07a
• /
• pp.63-68
• /
• 2002

In a utility interactive photovoltaic generation system, a PWM inverter is used for the connection between the photovoltaic arrays and the utility. The do current becomes pulsated when the conventional inverter system operates in the continuous current mode and dc current pulsation causes the distortion of the ac current waveform. To reduce pulsation of dc input current, This paper presents a Buck-Boost PWM power inverter and its application for residential photovoltaic system. The PWM power inverter is realized by combining two sets of a high frequency Buck-Boost chopper and by making it operate in the discontinuous conduction mode. In this paper, we show the Buck-Boost PWM power inverter circuit, its equivalent circuit and basic differential equations and the power flow characteristics are clarified when the proposed Inverter is interconnected with the utility lines. In conclusion, the proposed inverter system provides a sinusoidal ac current for domestic loads and the utility line with unity power factor

• Proceedings of the KIPE Conference
• /
• 1999.07a
• /
• pp.278-281
• /
• 1999

In a utility interactive photovoltaic system, a PWM inverter is used for the connection between the photovoltaic arrays and the utility. The DC current becomes pulsated causes the distortion of the AC current waveform. This paper presents the reduced pulsation of DC input current by operating the inverter with buck-boost chopper in the discontinuous conduction mode. The DC current with contains harmonics component is analyzed by means of separating into two terms of a ripple component and a direct component. The constant DC current without pulsation is supplied from photovoltaic array to the inverter. The proposed inverter system provide a sinusoidal AC current for domestic loads and the utility line with unity power factor.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.40 no.12
• /
• pp.1230-1241
• /
• 1991

Asymmetrical pulse width modulated(APWM) control technique for AC chopper is proposed which can improve the input power factor. The ideal switching function for the proposed technique is derived and its optimal slope to maintain the input power factor to unity is calculated. By digital simulation several characteristics are investigated theoretically and then compared with those of the conventional PWM and the phase angle control technique. In order to maintain the input power factor to unity the optimal slope and the average value of the ideal switching function are calculated. The experimental results show a good agreement with the calculated ones, which proves the feasibility of the proposed technique.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.4 no.4
• /
• pp.325-331
• /
• 1999

In a utility interactive photovoltaic generation system. a PWM inverter is used for the connection between the p photovoltaic arrays and the utility. The dc current becomes pulsated when the conventional inverter system operates i in the continuous current mode and de current pulsation causes the distortion of the accurrent waveform. This paper p presents the reduced pulsation of de input current by operating the inverter with buck-boost chopper in the d discontinuous conduction mode. The dc current which contains harmonic component is analyzed by means of s separating into two terms of a ripple component and a direct component. The constant dc current without p pulsation is supplied from photovoltaic array to the inverter. The proposed inverter system provides a sinusoidal ac c current for domestic loads and the utility line with unity power factor.

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

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.9 no.2
• /
• pp.360-369
• /
• 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
• /
• 2002.07b
• /
• pp.1075-1077
• /
• 2002

This paper describes a three-phase step-down AC voltage regulator using AC chopper and auxiliary transformer which is series connected with main input. It has many advantages such as fast voltage control, high efficiency and low THD. The operation principle and PWM method of the proposed regulator are described. Experimental results show that it can be used as step-down AC voltage regulator for power saving purpose very efficiently.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.50 no.9
• /
• pp.445-452
• /
• 2001

Two switching signal patterns are proposed to prevent short circuit of PWM ac choppers. The voltage detection method and the current detection method are proposed to execute two switching signal patterns. In the voltage detection method, the dead-time has to be inserted to the switching signals after polarity of input voltage is checked by voltage transducer at input side. In the current detection method, the direction of load current is checked by current transducer at output side, and the dead-time delay is not considered. Controlling circuit built by current detection method is simple because the dead-time delay is considered. The experimental results are presented to prevent short circuit of ac chopper safely.

• Proceedings of the KIEE Conference
• /
• 2000.07b
• /
• pp.1151-1154
• /
• 2000

Phase angle control ac drives system gains a high popularity due to their simple implementation despite the disadvantage of their poor input power factor especially for large values of phase delay angle. Furthermore it generates subharmononic current at specific phase angle. As input current of do drive systems are sinusoidal, the power factor and subharmonic current characteristics are improve. This paper presents the application of a PWM control technique of do chopper system to reduce the subharmonic current and its characteristics using single-phase dc chopper drive system of universal motor.