A Study on dc Current Ripple Compensation for Single-Phase Current-sourced Inverters

• Main Authors: Yun Shen Lin, 林運昇
• Other Authors: W. L. Chen
• Format: Others
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/81206475598606828536

碩士 === 長庚大學 === 電機工程學系 === 100 === With single-phase inverters there are second-order harmonic at dc-link circuit accompanying the power pulsations that can be a troublesome in applications. Solutions have been sought to this problem by the utilization of passive LC filter or variable modulation index for the inverter. The prior method is effective in alleviating the second-order harmonic at the dc-link circuit and keeping the harmonic out of the inverter ac output. However, the passive filter is so bulky that it is not suitable for practical use. The former method does not aim to suppress the current ripple but vary the modulation index with the second-order harmonic in order to improve the quality of the inverter ac output. Due to the oscillatory nature of the harmonic, the dc component at dc-link circuit should be high enough for modulating the inverter to ride over the notch caused by the second-order harmonic, which would limit the power range of the single-phase inverter. To facilitate the single-phase inverter operating over a wide power range with reasonable average dc current, an active dc current ripple compensator for current-sourced inverters is presented. The dc current ripple compensator is essentially a buck converter whose output is controlled to imitate the voltage across a passive filter thereby alleviating the ripple at dc-link circuit. To further expedite the voltage tracking capability for the buck converter, a proportional-resonant (PR) controller is adopted. A laboratory prototype, based on a 500W grid-tied single-phase current-sourced inverter, has been implemented. The comparative experimental results confirm that the proposed strategy is superior to the existing solutions.