Research on Highly Reliable GTO PWM Inverter Systems

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Highly reliable GTO PWM multi-inverter systems were studied in this project. The results were as follows,1. Parallel runnings of the two inverters were carried out with individual reactors for each inverter instead of the center-tap-reactors. The performance was satisfactory, although the output voltage regulations increase a little.2. In order to know possibility of separate triangular waveforms for the PWM pulse generation, higher harmonic components of the circulating currents between two inverters were measured with changing the amplitude and phase of the two triangular waveforms. The magnitudes of the harmonic components were minimum when the phase difference of the two triangular waveforms was 180゜.3. The transient phenomena between the single running and the parallel running were studied. The special gate pulse sequences realized smooth transients.4. The dc power sources were separated to increase reliability of the system. The control of the inverters for the case was studied.5. Parallel running of inverters with different capacities are necessary when new sets of inverters are connected to old sets. Therefore, two kinds of power control were contrived and realized using feedback of the circulating currents.6. The detection circuits of the circulating currents were improved so that the system might allow the transient change of the output frequencies.From these results, the GTO PWM multi-inverter systems were realized using the principle of the individual control.