| Abstract |
For the selection of the DC link capacitor in voltage source inverters, the AC current through the capacitor is very important, as it increases the internal temperature by power
dissipation and so influences the life time of the capacitor. In bidirectional power converters, the line side and the motor side inverter make a contribution on the current in the DC link capacitor. In the paper these currents are analysed at first. The influence of the operating point is shown with respect to the speed range of an inverter drive. Relating to the stress of the DC link capacitor by AC current two different cases can be distinguished: for unequal
switching frequencies of the line side and the motor side inverter the harmonics in the currents in the DC link are independent from each other and form their. own RMS values. In the other case the switching frequencies are equal; the superposition of the harmonics yields the RMS value, which depends among other things on the displacement angle between the
pulse patterns of both inverters. This additional degree of freedom can be used to minimize ·the AC current of the DC link capacitor. |
