Design of D-Σ digital controlled hybrid-frequency inverters with lcl filter for grid-connected applications

This study presents design of D-Σ digital controlled hybrid-frequency inverters with LCL filter for grid-connected applications. Hybrid-frequency inverters consist of inverters with different frequencies and power ratings connected in parallel. The lower frequency inverter has higher power rating, while the higher frequency inverter has lower one. The inverters are controlled to cancel out low-frequency switching-current ripples, and their equivalent switching frequency and dynamic response are dominated by the high switching frequency, reducing filter size. With different frequencies and power ratings, the inverters have extra power scheduling and control freedom. Moreover, with hybrid-frequency-inverter systems, it is no need to use high power high frequency switching devices. Features of smaller current ripples, passive filter size and better dynamic performance comparing to single frequency and conventional interleaved inverters are verified by simulation results.