Simplified discrete-time modeling and dynamic characteristics analysis of PI-controlled voltage source inverter

The characteristic of voltage source inverter under Pi-control is much more complex than under P-control. When system parameters are not properly designed, this system may appear unstable oscillation at different frequency. The stability boundary of control parameters have both upper and lower limit. in previous works on discrete-time modeling and analysis, P-controller is always taken as object of study for simplicity, which is different from practical applications where Pi-controller is often adopted. Therefore, previous works have limited research significance. in this paper, a simplified discrete-time model of voltage source inverter under Pi-control is derived. Based on analysis of the proposed model, different unstable phenomenon and mechanism corresponding to upper and lower stability boundary have been revealed. Moreover, high accuracy stability boundary has been derived and verified by experiment.