Analysis of the zero dynamics of three-phase current source inverters using a complex-valued approach

This paper analyzes the zero dynamics of three-phase current source inverters fed from a voltage source and connected to a local resistive load or the electrical power grid. The zero dynamics is the remaining dynamics of a system when it exactly meets the control objectives. It is important for understanding the system behaviour, and its limitations, and designing efficacious controllers. The analysis concludes that, when the power source is modelled from its Thévenin equivalent circuit, some stability problems occur in the dc link if the control scheme only tracks the output voltage. The paper includes an alternative nested-loop controller that overcomes the internal dc-current instability.