摘要
直流微电网孤岛运行状态下,由于分布式电源(distributed generation,DG)的不确定性,需要加入储能单元进行补充.对于传统下垂控制,线路阻抗差异造成输出电流无法精确分配,对储能单元荷电状态(state of charge,SOC)的均衡效果造成影响,且随着SOC的降低,收敛速度变慢,同时没有考虑DG波动对母线电压的影响.因此,提出一种改进下垂控制策略,通过计算输出电流偏差量,引入对电流偏差的积分环节,消除线路阻抗差异的影响,并且设计加速项和自适应变化的加速系数,提高了SOC均衡速度.当DG波动时调整输出电流增发量,满足负荷功率平衡,保持电压稳定.经过仿真验证,所提控制策略在考虑线路阻抗时的SOC收敛误差小于 0.1%,收敛速度较对比方法提高 20%,并且电压降落小于3%.
Abstract
Due to the uncertainty of distributed generation(DG)in islanding DC microgrids,it is necessary to add an energy storage unit for a supplement.In traditional droop control,the output current cannot be accurately distributed due to line impedance difference,which affects the balancing effect of the energy storage unit's state of charge(SOC).Besides,the convergence rate slows down as SOC decreases.Also,the influence of DG fluctuation on bus voltage is not considered.Therefore,an improved droop control strategy is proposed.By calculating the output current deviation,the authors introduce an integrator for the current deviation to eliminate the influence of the line impedance difference.Acceleration term and adaptive acceleration factor are also designed to increase the SOC balancing speed.When the DG fluctuates,the output current increment is adjusted to meet the load power balance and keep the voltage stable.The simulation results show that the SOC convergence error of the proposed control strategy is less than 0.1%when considering the line impedance.Convergence speed increases by 20%compared with the method referred,and the voltage drop is less than 3%.
基金项目
国家自然科学基金资助项目(62273170)
辽宁省教育厅重点攻关项目(JZL201915401)
维普
万方数据