An LCCL filter and its application to a Half-Bridge APF

In this paper, a novel high order power filter is proposed, named the LCCL filter. Compared with the traditional LCL filter, the LCCL filter composes a parallel resonant branch loop at the switching frequency by paralleling a small capacitor with the line side inductor. The parallel resonance enables the line side branch loop to exhibit infinite impedance at the switching frequency. Particularly, it can attenuate the switching frequency current ripple components much better than the LCL filter, thus decreases grid current THD. Compared with an LLCL filter, the LCCL filter exhibits better attenuation ability in the high frequency domain when the source impedance is considered. Besides, a capacitor-current-based active damping controller is easy to design on the basis of the LCCL filter. A half-bridge APF is taken as an example in this paper to discuss the parameter selection and the controller design method based on the LCCL filter. At last, simulation and experimental results validate the feasibility of the proposed LCCL filter.