兼顾提升功率分配精度与抑制电压偏差的自适应下垂控制

Adaptive sag control with improved power distribution accuracy and voltage deviation suppression

直流微电网孤岛运行时,为实现下垂参数跟随直流微电网各光伏单元出口线路阻抗和本地负载分布情况自调整,提出一种基于麻雀搜索算法(sparrow search algorithm,SSA)的自适应下垂控制策略。将下垂参数、变换器输出电压参考值以函数变量的形式构成优化目标函数,利用麻雀搜索算法寻找目标函数的极小值,实时找到同时使系统运行过程中的功率偏差、母线电压偏差最小化的解。即利用麻雀搜索算法将下垂参数和电压参考值调节问题转化为函数极值寻优问题,实现了下垂系数可依据光伏出口线路阻抗、本地负载变化及光照强度变化自调整的目标。同时通过动态调节变换器输出电压参考值,减小母线电压偏差,解决了功率分配精度与母线电压偏差的固有矛盾。利用PSCAD/EMTDC建立系统仿真模型,仿真结果证明所提控制策略正确、有效。

To realize droop parameter self-adaptation in islanded operation of DC microgrids according to the impedance and local load distribution of each photovoltaic unit’s output line within the microgrid,a self-adaptive droop control strategy based on the sparrow search algorithm(SSA)is proposed.To begin with,an objective function that incorporates the droop parameters and converter output voltage reference is constituted in the form of function variable.The SSA is then used to search and determine in real-time the local minima that also minimize both the power deviation and bus voltage deviation during operation.In other words,the proposed strategy transforms what should otherwise be a trade-off problem between droop parameter and voltage reference into a local extremum search problem using SSA.It thereby fulfils the objective of droop parameter self-adaptation under variations in photovoltaic output line impedance,local load,and solar irradiance.At the same time,the act of dynamically adjusting the converter’s output voltage reference values also reduces the bus voltage deviation and resolves the inherent contradiction between power allocation accuracy and bus voltage deviation.A simulation run using a system model created with PSCAD/EMTDC proves the validity and effectiveness of the proposed control strategy.