扰动观测法控制MPPT系统运动特性分析

扰动观测法是光伏系统MPPT算法中最常用的追踪算法.为了准确实现扰动观测法的追踪效果,该文基于扰动观测法等同于分段恒压控制的思想,推导了扰动观测法控制的调整时间公式,分析了扰动观测法控制MPPT系统工作点在光强突变时的运动特性,提出了"错误保持"、"正确保持"、"判断错误"和"判断正确"四个概念,总结了扰动观测法控制MPPT系统工作点的十二种运动情形及其动态效果,仿真结果和实验结果验证了四种典型运动情形.以此十二种运动情形为依据提出了一种对等评价不同扰动观测法控制性能优劣的评判方法,并应用该方法研究固定步长和变步长的暂态性能,结果表明,当判断错误时,变步长控制的动态性能比定步长的更差.该文研究结果有助于改善干扰控制法的动态性能.

Motion Characteristics Analysis of P&Q Control MPPT System

A perturb and observe (P&Q) method is the most commonly used MPPT (maximum power point tracing) algorithm for photovoltaic system.For achieving accurate tracking effect,based on the idea of P&Q method equivalent to piecewise constant voltage method,the settled time formula of the P&Q control MPPT system was deduced in this paper.The motion characteristics of MPPT system operating point were analyzed when the light intensity changes,and then four concepts such as "wrong maintaining","right maintaining","misjudgment" and "good judgment",are proposed.It is summarized that 12 movement situations of P&Q control MPPT system operating point correspond to a dozen different dynamic effects;finally the simulations and experimental results verify 4 typical motions.Based on 12 motions,the fair evaluation method for different implementation of the P&Q method is presented,and then the method is used to study the fixed step and variable step method.Simulation results show that when a misjudgment occurs,the dynamic performance of a variable step size is less than the fixed step size.The results contribute to the improvement of the dynamic performance of the P&Q method.