Parallel-Converter System Grid Current Switching Ripples Reduction Using a Simple Decentralized Interleaving PWM Approach

A simple decentralized interleaving PWM approach is proposed for parallel grid-tied converters, in order to achieve significant reduction of switching current ripples at the point of common couplings (PCC). First, the remote PCC voltage phase angle information is calculated through only the local measurement of a distribution generation (DG) unit converter and the estimation of the corresponding feeder voltage drops. With simple interpolations, the discretized PCC voltage angle information at a DG local controller is used as a novel synchronizer to effectively identify the carrier angle of DG units at the exact time instant of the PCC voltage phase angle zero crossing. Then, the relative digital carrier phase angles of parallel DG units are adaptively adjusted in a high-resolution manner until they are properly interleaved. It has been validated that the proposed modulation approach is effective under adverse situations with mismatched feeder impedances, processor crystal oscillator frequency deviations, and notable grid voltage frequency/magnitude disturbances.