微网逆变器并联运行的改进下垂控制策略

Improved Droop Control Strategy for Inverters Parallel Operation in Micro-Grid

逆变器并联系统采用有功-电压频率(P-f)和无功-电压幅值(Q-U)下垂控制方法实现功率均分时,由于采用固定下垂参数,输出电压精度与功率均分效果之间存在矛盾;同时负荷发生剧烈突变时易造成输出电流振荡,从而影响系统的稳定运行。此外,为获得稳定准确的系统功率输出,功率计算环节须引入低通滤波器,低通滤波器的延迟特性将会对系统的动态性能产生影响。为此,提出了一种改进的逆变器自适应下垂控制方法,该方法在传统控制方法基础上分别引入功率与下垂系数的一次函数项和功率与时间的微分项,既实现了下垂系数随功率变化的自适应调节,又及时反映出功率的变化趋势,有效提高了系统的稳定运行性能和动态响应能力。实验结果验证了所提方法的有效性。

In the inverters parallel system which using the P-f and Q-U droop control method, the fixed droop coefficients are used to realize the power sharing, which will cause the contradiction between the output voltage precision and the power sharing effect. In addition, the output current oscillations caused by the loading variation could occur, which will decrease the stable operation performance of the whole system. Furthermore, the dynamics of the overall system are strongly influenced by the delaying characteristics of the low-pass filters which introduced to achieve the precise power calculation. To solve the problems mentioned above, an improved adaptive droop method is investigated for the control of the inverters. In the proposed method, a linear function of the power and droop coefficient is introduced to realize the adaptive regulation for the droop coefficients with the power variation, while a power derivative term is introduced to instantaneously reflect the trend of power, which effectively improving the stable operation performance and dynamic response capability. Finally, experimental results are used to validate the proposed droop control method.