On the Parametric Dependence of the Stability of a Current Controlled Grid Tied Inverter

Stability of a Grid Tied Inverter at the point of common coupling is subject to interaction between the inverter control and the passive elements of the grid. Stability study of such a system is performed using the Impedance based criteria. The overall impedance of an inverter is a function of the control system and therefore its parameters plays a critical role in preserving the stability. The paper derives the sensitivity of the impedance return ratio to change in controller gains and explores their dependence on the overall stability. Sensitivity functions has been formulated with respect to each design parameters i.e the controller gains. It has been observed that return ratio shaping at low frequency will be dominated by PLL controller gain changes, whereas for mid to high frequency range, the current controller gain change will play a vital role. The reference parameters for the current control also plays a significant role in improving the return ratio trajectory at low frequency range.