分切合整數位控制能夠精確追蹤參考電流命令並涵蓋寬廣感值變化，已成功應用於單相/三相雙向LC換流器。然而，當換流器操作在併網模式時，市電對電流諧波和因開關切換造成的電流漣波相當於短路，因此高頻的開關切換漣波會大量注入市電，而不能被LC濾波器中的濾波電容所吸收。為了避免漣波電流注入市電，提高電網電流品質，減少對電網的污染，需選用LCL濾波器。LCL濾波器存在著穩定性問題，容易發散和振盪，這將轉而導致電網電流失真。當市電存在顯著的電壓諧波時，同樣會影響電網電流，造成電網電流嚴重失真，並且濾波器中電容電流也會含有諧波成份。爲了使注入市電的電流是基頻弦波電流，換流器的電流追蹤命令必須被更新為新的參考電流，因此本研究提出了基於分切合整控制的電容電流補償機制，此控制機制將分切合整計算所得的參考電流命令與濾波電容電流相加得到新的參考電流命令，使得電流諧波能夠經靠近換流器之濾波電感來補償，從而降低電網電流諧波。經由詳細的理論分析與模擬驗證，此控制機制不僅可有效抑制市電諧波的影響，提高電網電流品質，而且使得換流器的輸出阻抗和電網阻抗在低頻到高頻都具有80°以上的相位裕度，並可以抑制39次高頻諧波電壓的影響，即使連接的電網阻抗較高，換流器也可正常運行。最後，實作出一部5 kW單相雙向換流器，並由實測結果驗證本研究之理論與可行性。

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.

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