Analytical Controller Synthesis Techniques for Integral Dominant Dual-Loop Stationary Frame Voltage Regulators

Abstract

This paper presents analytical synthesis relationships for cascaded dual loop voltage regulated voltage source inverters (VSIs) incorporating second order inductive-capacitive (LC) filters with integral-dominant frequency response characteristics. This family of control system is characterized by improved stability properties with a passive terminal impedance characteristic to provide better robustness in grid-tied scenarios. The synthesis technique is developed in the Laplace domain and accounts for the outer and inner loop controllers, active damping of the LC resonance and transport delay due to the modulator. Bode frequency analysis enables selection of the outer loop voltage regulator parameters, and consequently enforces a damping condition on the inner-loop current regulator. Matching discrete time pole-zero maps and switched PSIM simulations validate the synthesis strategy.