State feedback decoupling with in-loop lead compensator in stand-alone VSIs

The performance of current and voltage regulators during transients and steady-state is of primary concern for power converters intended for stand-alone applications. Dynamics performance and command tracking capability are enhanced by actively decoupling the controlled states variables. To further widen the current loop bandwidth while still preserving a well-damped system a lead compensator structure on the forward loop is proposed. A 3 kHz bandwidth with 0.707 damping factor is achieved for the inner current controller. Accordingly, also the voltage regulator bandwidth can be widen, thus requiring even more a proper anti-wind up scheme to avoid saturation of the integral term during demanding transients. Lab-tests are performed in accordance with standards imposed to uninterruptible power supplies, verifying the theoretical analysis.