分布式光储直流供电系统非线性平滑可微控制方法

Nonlinear Differential Flatness Control of Distributed Photovoltaic-Energy Storage DC Generation System

针对分布式光储直流供电系统变流装置传统拓扑占空比调节方式约束电压输出范围的问题,提出四相交错式变流器的设计架构,有效拓宽输出电压范围,同时抑制光伏输出电压波动。系统拓扑中,光伏单元四相交错升压变流器设计改进的极值搜索法,实现光伏输出的最大功率点跟踪,提高光照阶跃变化情况下系统的快速性和稳定性;储能电池四相交错双向变流器设计非线性平滑可微控制方法,实现光储最优协调控制,确保存在负载突变或控制参数摄动的情况下,系统依然能够保持直流母线电压平稳,输出功率平滑。仿真与实验结果表明:较传统的比例—积分(PI)控制方法,所提出的非线性平滑可微控制方法具有结构简单、自由度宽、稳态误差小、系统稳定性好等特点。

As the traditional converters in distributed photovoltaic-energy storage direct current（ DC） generation system will be limited when the power increases or is at higher step-up ratios,four-phase parallel converters are adopted in the proposed system,which can broaden the range of output voltage and suppress oscillation of photovoltaic output voltage. For photovoltaic four-phase parallel boost converters,an improved extremum seeking algorithm is designed to achieve maximun power point tracing and improve the system rapidity and stability in light step change. For energy storage four-phase parallel bidirectional converters,a novel nonlinear control law based on the flatness principle is proposed,which is a simple solution to smooth the output power and stabilize the system with a load mutation or control parameter perturbation. Compared with the conventional proportional-integral control method, the nonlinear differential flatness control algorithm has broader degrees of freedom,fewer steady-state errors and better system stability as proved by simulation and experimental results.