利用有功功率扰动的微网孤岛下垂控制策略

对于孤岛模式运行的微网中的并联逆变器,其功率分配主要受逆变器输出阻抗和输出端与公共连接点之间线路阻抗差异的影响。以感性输出阻抗为例,从逆变器并联的功率传输特性出发,分析了线路阻抗差异对并联逆变器无功功率分配的影响。为了提高无功功率的均分精度,提出了一种改进型下垂控制策略,在有功频率下垂中加入无功功率,利用有功扰动反映无功分配偏差,在无功幅值下垂中加入可调下垂系数,通过消除有功扰动调节下垂系数补偿线路阻抗差异实现稳态时无功均分。仿真和实验验证了改进下垂控制策略的正确性和有效性。

Droop Control Strategy in Microgrid Isolated Island Mode Using Active Power Disturbance

The power distribution of the parallel inverters in the microgrid operation with the island mode,is mainly influenced by the output impedance of the inverter and the difference of the line impedance between the output end and the common connection point. Started from power transmission char-acteristics of parallel inverters,the influence of line impedance difference on reactive power sharing between inductive inverters was analyzed. In order to improve the reactive power sharing accuracy,an improved droop control strategy was proposed. A term of reactive power was added to the conventional real power-frequency droop control and an adjustable droop coefficient was added to the conventional reactive power-voltage droop control. The transient real power variation caused by reactive power was captured to realize adjustable droop coefficient tuning. With the regulation of droop coefficient,line impedance difference was compensated and accurate reactive power sharing was realized at the steady state. Simulations and experimental results prove the correctness and effectiveness of the improved droop control strategy.