Akio Toba

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.

Analytical method and suppression technique of conducted EMI noise in a multi-converter system

A method is proposed for the analysis of conducted electromagnetic interference (EMI) in multiple power converters connected to the same power line. This method is focused on the phase differences of the sub-harmonic modulation carrier signal for each power converter. It is confirmed that the phase difference among the power converters determines the EMI noise value in a multi-converter system by analyzing waveform of the common-mode current. In addition, EMI noise suppressions based on a novel phase-difference control technique are also proposed. In order to reduce volume of EMI filter effectively, phase difference θ should be set to 360/nN°, here n is high-order harmonic component near 150 kHz, and N is the number of power converters. On the other hand, in order to prevent radio disturbance, another phase-difference τ should be set to 180fc/fx° not depending on the number of converters (N), here fC is carrier frequency of the converters, and fX is center frequency of frequency band of AM radio. Therefore, Conducted EMI noise can be reduced effectively based on the proposed phase-control for any purpose.

Analysis of EMI filter attenuation characteristics for a multi-converter system

A method is proposed for analysis of the attenuation characteristics of electromagnetic interference (EMI) filters for multiple power converters connected to same power line. The analysis results indicate that increase of the conducted EMI noise may occur, because the cut-off frequencies of the EMI-filter are varied according to the number of power converters. A mathematical solution for the cut-off frequencies is derived by simplification of the circuit configuration based on Thevenins theorem. Finally, an effective design method of EMI filters is proposed to avoid such problem of a multi-converter system.

PWM Rectifier with DC Reverse-Blocking Diode for High-Reliability Generating Apparatus and Its Application to Gas Heat Pump System.

High reliability generating apparatus with a PWM rectifier equipped with a DC reverse-blocking diode is proposed. The PWM rectifier adjusts the power from a permanent magnet synchronous generator by means of position sensorless control. Due to the DC diode, the PWM rectifier is shoot-through free, i.e. the switches in one arm are not broken with their simultaneous turning-on caused by electromagnetic interferences, etc. The apparatus is applied to the gas heat pump system (GHP), which is an efficient air-conditioning system powered by fueling gas, to satisfy its requirement of high reliability to the electrical equipment. There is a control issue in the proposed circuit, that is the DC bus capacitor is electrically separated from the switches when the DC diode is reverse-blocking, which results in the voltage fluctuation at the switches side. This is overcome by adding a stabilization control. The system is tested with a 1.5 kW-class experimental setup, which demonstrates desirable performances as expected, and it is confirmed that the rectifier is durable to the simultaneous turning-on of the switches in one arm