Single-phase grid-connected power decoupling inverter based on Buck converter

In single-phase grid-connected inverter, the inherent double frequency pulsating power at the grid side will lead to the non-ideal low-frequency ripple of the DC bus voltage/current. The common solution is to connect large capacity electrolytic capacitors in parallel on the DC bus. The service life of electrolytic capacitor is low and will lead to a significant reduction in system power density. In order to remove the electrolytic capacitor from the design, this paper designs an active power decoupling circuit with Buck structure to compensate for the second harmonic power fluctuation. The reference value of decoupling capacitor voltage can be obtained by the instantaneous power feedforward at the grid side. The active decoupling control of the second harmonic power is realized by using the double closed-loop control method of the outer loop of the capacitor voltage and the inner loop of the inductance current. The effectiveness of the control strategy is verified by Matlab/Simulink simulation.