Mitsuo Shioya

A method for calculating harmonic currents of a three-phase bridge uncontrolled rectifier with DC filter

A practical method is proposed for calculating the harmonic currents of a three-phase bridge uncontrolled rectifier with a DC filter, taking into account the AC source reactance. The method is based on the frequency-domain method and the rectifier switching functions. Analytical equations for the harmonic currents on both the DC and AC sides are derived. The validity of the method is demonstrated by comparison with the results of time simulation. The approach can be extended to the harmonic analysis of a thyristor rectifier as well as a rectifier with unbalanced line conditions. >

Auxiliary resonant commutated pole inverter using two internal voltage-points of DC source

This paper presents a new auxiliary resonant commutated pole inverter that has series-connected batteries as the DC source. This inverter has two main switches and two auxiliary switches, and of all these devices achieve soft switching. The resonant operations are employed only during the commutating intervals; therefore, pulsewidth modulation (PWM) can be applied to the circuit. This circuit has the feature of using two internal voltage points of the DC source. Consequently, the circuit has the advantages of stability, simplicity in control, and high efficiency. The principle of the circuit operation and the experimental results are described in this paper.

Five-stepped PWM inverter used in photovoltaic systems

A PWM (pulse-width-modulated) inverter that has five-stepped output-voltage levels is introduced. In this inverter, the waveform of the output voltage has a smaller harmonic content than that of a conventional PWM inverter. A novel PWM technique is analyzed. The PWM pulses included in the waveform of the output voltage are formed using a criterion based on the calculation that each area of voltage pulses is equal to the integrated value of each time shared area of a reference sinusoidal waveform. This PWM technique for the five-stepped PWM inverter is superior to the conventional PWM technique, and the experimental results coincided with the calculation obtained using the fast Fourier transform. In addition, the relations between the number of PWM pulses and the harmonic contents of the output voltage are described. >

Characteristics of electric power transmission on high-frequency inverter having distributed constant line at load side

An induction heating system aimed at improving the characteristics of high-frequency power supplied from the high-frequency, inverter to the parallel resonant load circuit is proposed, and its transmission efficiency is studied. In this system, high-frequency power can be supplied by lowering the effect of the inductance component accompanied by wiring between the inverter circuit and the resonant load circuit. Impedance matching between the inverter and the resonant circuit and high-efficiency power transmission from the inverter to the load circuit are possible. If a flexible coaxial cable is used as the distributed constant line, it is easy to cope with the case in which comparative distance exists between the inverter part and the heating part or the case in which the heating part is moved. >

New control method of resonant DC-DC converter in small scaled photovoltaic system

The authors describe a control method for a resonant DC-DC converter in a small-scale photovoltaic system linked up with storage batteries. The converter is suitable for tracking control of storage battery charging. The control method and experimental results are presented. Optimum operation was achieved by the application of the improved control circuit presented. With this circuit, it is possible to implement tracking control for various intensities of solar radiation.<<ETX>>

New type of ballast for HID lamps using series resonant circuit

A new type of solid state ballast, which can provide the high-frequency power to high intensity discharge (HID) lamps without an acoustic resonance, is presented. A ballast is needed to lighten the HID images, and is expected to be small and stably operating. The ballast equipment is composed of an inverter circuit, having variable switching frequency, a series resonant circuit, and a starting capacitor of the HID lamps. The operating characteristics of the ballast circuit are presented. The proposed circuit is useful for the HID lamps due to the small size and the low switching losses.<<ETX>>

Improved operating characteristics of linear pulse motor using resonant current

The linear pulse motor (LPM) requires strong thrust force and smooth movement with suppression of its pulsation and pulling-out. To respond to these requirements, several methods have been reported. But there are some defects such as large power loss, complicated additional circuits, deterioration of thrust force characteristics at high operating speed and so on. This paper describes the new control circuit improving these defects, in which the variable capacitor or switched variable capacitor circuit is connected with a motor winding in series. This capacitor is controlled to maintain the resonant condition that is achieved by the capacitor and the inductance of the motor windings, and this circuit makes the exciting current waveform sinusoidal. It is confirmed that the resonant current of the sinusoidal waveform causes the smooth movement and improves the thrust force characteristics over the wide range of pulse rates.<<ETX>>

Battery charging characteristics in small scaled photovoltaic system using resonant DC-DC converter with electric isolation

The system described is a small-scale photovoltaic system with storage batteries. A theoretical analyses is presented of the photovoltaic system using a resonant DC-DC power converter in order to clarify a desirable circuit condition. The experimental results of the battery charging characteristics are presented.<<ETX>>

New quasi-resonant PWM inverter using two internal voltage-points of DC source

This paper presents a new quasi-resonant PWM inverter which has series-connected batteries as the DC-source. The inverter includes two main switches and two additional switches, and all these devices achieve soft switching operation. Resonant operations are employed only during the commutating intervals, then the circuit behaves as an ordinary PWM inverter except during these intervals. This circuit has the feature of using two internal voltage-points of the DC source. Consequently, the circuit has the advantages of stability, simplicity in control, and high efficiency. The principle of the circuit operation and the experimental results are described in this paper.<<ETX>>

Advanced circuit of five-level PWM inverter with an inductive load

The authors present a type of PWM (pulse-width-modulated) inverter for a small-scale photovoltaic power system. It has five voltage levels, including the earth level, which is composed of charging two storage battery units in series or parallel combination. The waveform of the output voltage is more sinusoidal than that of the conventional PWM inverter. In the case of an inductive load, however, the waveform shows some deteriorations. The operation of this PWM inverter with an inductive load is analyzed. An advanced circuit is devised to eliminate these deteriorations. It is verified that the experimental results agree well with the theoretical results obtained using FFT (fast Fourier transform) analysis. A resonant-type five-level PWM inverter is also presented.<<ETX>>