Impedance-Based Stability Analysis for a Dead - Beat-Controlled Grid-Forming Inverter Using Cross-Correlation Methods

A voltage-controlled voltage-source inverter is re-sponsible for providing a high-quality voltage to a set of loads re-gardless of their nature. Even in scenarios with a high penetration of power electronics devices and nonlinear, distorting loads, the voltage quality must be ensured via an efficient control strategy. Furthermore, stability assessment of such a system is quite important inasmuch as the overall stability depends both on the inverter impedance and on the time-variant equivalent impedance of the load. This paper describes a dead-beat controller design procedure for voltage-source inverters with LC output filter. A harmonic-stability analysis via the impedance-based criteria is presented taking into account the existence of unstable poles in the impedance ratio. The pseudo-random binary sequence technique and the cross-correlation method are employed to identify the impedances associated with the system stability.