并網逆變器直接并聯運行時，可使系統體積減少、成本降低。但并網逆變器直接并聯時會產生環流。為此，詳細分析了并網逆變器直接并聯運行時環流產生的機理，建立了并網逆變器并聯運行時旋轉坐標系下的狀態平均模型。在這模型的基礎上，分析并網逆變器并聯運行時的相互影響；分析了并網逆變器采用間矢量脈寬調制（SVPWM）算法時零矢量對環流的影響。通過控制SVPWM 算法中不同零矢量在每一個PWM 周期的作用時間來抑制環流。對并網逆變器在不同情況下的并聯運行進行了實驗。實驗結果表明：該控制策略能有效的抑制環流，從而驗證該控制策略的可行性和正確性。
ABSTRACT: It is desirable to have a directly connected structure for grid-connected inverter because of compact size and low cost. The circulating current will be generated when grid-connected inverters are in direct parallel operation. So the mechanism of circulating current is analysed in detail for grid-connected inverters in direct parallel operation and the state average model of the parallel grid-connected inverters is constructed in rotating coordinates. Based on this model, interaction between the parallel grid-connected inverters is analyzed and the influence on circulating current when it is adopted zero vector with space vector pulse width modulation(SVPWM) is also analysed. The circulating current can be effectively inhibited by controlling the operation time for different zero vectors in each PWM cycle. The parellel grid-connected inverters are tested under different circumstance. The experimental results show that the control strategy can effectively inhibite circulating current, so the feasibility and correctness for the control strategy is verified.
關鍵詞：并網逆變器；直接并聯；環流；平均模型
KEY WORDS: grid-connected inverter; direct parallel operation ; circulating current; average model