Study of Applicability of Simple Closed Loop Input Impedance Model for Grid-Tie Inverters

In recent years the need for DC distribution buses
has increased considerably. As it can be noticed in the transport
for example the distribution systems of the more electric
aircrafts, ships, or electric cars. Given the complexities of the
systems presented above, the need to use more and more
switched power converters has arisen. The main problem of the
connection of multiple controlled switched converters acting as
source and load is the degradation of stability that occurs on the
DC distribution bus due to the converter interactions. To study
the stability in the distribution bus there are some wellestablished
criteria. These criteria require knowledge of the
input impedance of the converters that act as load and the output
impedance of the equipment that acts as source. In order to
reduce the complexity of obtaining the input impedance a model
based on a controlled converter acting as a constant power load
(CPL) is commonly used. This article studies the accuracy of this
model for a commonly used topology in distribution systems
nowadays, Two Level Voltage Source Converter (2L-VSC),
studying different scenarios that make the model become
inaccurate.