并网逆变器直接并联运行时，可使系统体积减少、成本降低。但并网逆变器直接并联时会产生环流。为此，详细分析了并网逆变器直接并联运行时环流产生的机理，建立了并网逆变器并联运行时旋转坐标系下的状态平均模型。在这模型的基础上，分析并网逆变器并联运行时的相互影响；分析了并网逆变器采用间矢量脉宽调制（SVPWM）算法时零矢量对环流的影响。通过控制SVPWM 算法中不同零矢量在每一个PWM 周期的作用时间来抑制环流。对并网逆变器在不同情况下的并联运行进行了实验。实验结果表明：该控制策略能有效的抑制环流，从而验证该控制策略的可行性和正确性。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.关键词：并网逆变器；直接并联；环流；平均模型KEY WORDS: grid-connected inverter; direct parallel operation ; circulating current; average model