The Harmonic Optimization of High-Power Converter Based on The LLCL Filter

A T-type three-level bidirectional converter based on the LLCL filter was constructed using transformer integrated filtering technology. The dual closed loop control is designed using the grid voltage vector-oriented control strategy, and the principle of controller parameter design based on the LLCL filter model is discussed. Low-order harmonic amplification occurs due to the presence of the ripple current and deadband. The transmission relations of harmonic components in the control loop are analyzed to find out the paths to suppress the lower order harmonics of grid side currents. Quasi-proportional resonance (Q-PR) controller and the second-order bandstop filter were used to remove the introduction of harmonic content in the control loop, effectively filtering out the pulsating voltage of the DC-side voltage without affecting the dynamic performance of the control system and improving the quality of transmitted power.