基于自适应虚拟阻抗的微电网无功均分控制

在微电网多逆变器并联系统中,由于微电网各逆变器之间存在输出阻抗和馈线阻抗不匹配现象,采用传统的下垂控制方法难以根据下垂系数合理地进行无功分配,同时还会产生无功环流问题。为提高无功均衡的精度,提出了一种基于自适应虚拟阻抗控制的控制策略。该方法在固定虚拟阻抗的基础上增加了积分环节,结合了改进的无功功率需求值来自适应调节分布式电源单元,最终补偿馈线阻抗失配,从而精确均分无功功率。此控制策略不仅无需提前预知馈线阻抗值,而且不需要通讯平台的参与,可在结构复杂的微电网中应用。研究结果表明:提出的虚拟阻抗无功均分控制方法相比于传统虚拟阻抗方法,其自适应能力和无功均衡性能更佳。

Reactive Power Sharing Control Method Based on Adaptive Virtual Impedance

In the multi-inverter parallel system of micro-grid, due to the mismatch between output impedance and feeder impedance between inverters in micro-grid, it is difficult to realize a rational reactive power distribution according to the sag coefficient by using the traditional droop control method, with even the problem of reactive power circulation to be generated. For an improvement of the accuracy of reactive power balance, a control strategy based on adaptive virtual impedance control has thus been proposed. With an integral link added on the basis of a fixed virtual impedance, the proposed method combines the improved reactive power demand value from the adaptively adjusted Distributed Generation (DG) unit, and compensates the impedance mismatch of the feeder, thus accurately dividing the reactive power evenly. Free of the dependence on the prediction of the impedance of feeders in advance, as well as on the participation of communication platform, this control strategy is applicable in the microgrid with complex structure. The results show that the proposed method is characterized with a better adaptive ability and reactive power balance than the traditional ones.