Peculiar Dynamics of the Stand-Alone Current Source Converter Based Photovoltaic System

The voltage source inverters (VSI) are usually used in Photo Voltaic (PV) systems as the converter for renewable energy system. However due to the inherent low voltage level of the PV cells, a DC/DC boost converter is needed to connect the PV to the inverter. Current Source Converters (CSI) on the other hand are voltage boost converters in nature. More so, the dc side inductors in CSI are more reliable when compared to the capacitors of VSI. The stress on the switches is lower due the fact that both switches on the same leg can be turned on at the same time. Prior to the controller design, inherent characteristics of the PV module connected to the CSI should be studied to determine the best operating point of the PV. PV generators can be considered as voltage or current sources depending on the operating regions. Although both regions are valid from power production point of view, the study of dynamic properties of a PV generator reveals that depending on the type of converter used; only one of these two regions is appropriate from the control point of view. This paper focuses on the use of the steady state results of both operation regions of the PV as well as the eigen-values and zero dynamic system of the system to locate the most stable and minimum phase region of operation.