| Summary: | 碩士 === 國立清華大學 === 電機工程學系 === 102 === Division-Summation (D-Σ) digital control has been successfully applied to the single-phase bi-directional inverter with an LC filter, which can cover wide inductance variation and achieve precise inverter current tracking. However, high frequency ripple current injection to the grid cannot be avoided, and an LCL filter is therefore required. Since there typically exists grid voltage harmonics, the injected grid current will contain harmonic components due to the effect of the LCL-filter-capacitor. This paper presents an extended application of the D-Σ digital control associated with a filter-capacitor-current compensation to reduce the injected grid-current harmonics. The control laws of the inverter with the D-Σ digital control and compensation approach are derived in detail, and the reduction of grid-current harmonics is analyzed. With the proposed approaches, the phase margin between the output impedance of the inverter and grid impedance can be higher than 80° from low to high frequencies, and the inverter can achieve high harmonic voltage rejection ratio up to 39th harmonic, which is relatively suitable for weak grid condition. Experimental results measured from a 5 kW single-phase bi-directional inverter have verified the feasible application of the D-Σ digital control and proposed compensation.
|
|---|
