Resonance Damping in Active Power Decoupled Single-Phase Grid-tied Differential Buck Inverter

The single-phase differential buck inverter allows active decoupling of the double-line frequency ripple power without employing the additional switching devices. The ripple energy storage is realized by two filter capacitors connected between the ac side terminals and the negative dc bus. The grid current control is attained by controlling the differential mode voltage of the ac side capacitors. The active power decoupling is achieved by controlling the common mode voltage such that the ripple power on the dc side is eliminated, allowing the use of a small and reliable film capacitor on the dc side sufficient to avoid the switching frequency current from the dc source. The present work comprehensively details the plant modeling and control design for the differential buck grid-tied inverter. It is analytically shown that the system’s differential mode and common mode plants are highly under damped due to the presence of LCL and LC resonances, respectively. Subsequently, the design of active damping loops is presented and shown to improve system stability. Further, the controller designs for grid current and active power decoupling are discussed. Finally, simulation results are presented to validate the analytical inferences derived in the paper.