On Investigating the Effect of DC Biased Ripple Voltages Over the Insulation of Bus Capacitor of Power Inverters: Possibility and Limitations

With the growing advances in semiconductor technology and introduction of new topologies in power networks, the implementation of power converters has dramatically increased. Such variations may impose additional electrical stresses and lead to failures in insulation systems. In this regard, understanding the behavior of insulation is of paramount importance. Conventionally, the spectroscopy of insulations is performed under sinusoidal voltage waveforms, while there are certain conditions, where the insulation is subjected to a nonsinusoidal voltage waveform with a possible dc bias. A good example of this situation could be the bus capacitor of power converters, where the capacitor on the dc voltage side provides a low-impedance loop for current ripple originating from the converter topology or load behavior. In this article, the complex permittivity of the insulation was extracted under dc-biased sinusoidal and nonsinusoidal voltage waveforms. The challenges associated with such measurements have been addressed, and finally, the results over a typical sample are presented and discussed.