面向光伏能量收集应用的实时MPPT预估算法研究

Research on real-time MPPT predictive algorithm for photovoltaic energy harvesting applications

对于环境中存在的各种类型能量源,其往往具有不同的阻抗特性以及输出功率范围。为了提高能量收集系统的能量萃取能力,合理的接口电路设计是关键。基于此,通过对环境中光伏(Photovoltaic,PV)能量源微弱直流特性以及高效率收集和转化的研究,在传统开路电压法(Open-Circuit Voltage,OCV)的基础上,结合输入电压纹波控制,提出了一种可实时最大功率点追踪(Maximum Power Point Tracking,MPPT)的预估算法。该预估算法根据能量源的输出特性,采用了分数开路电压法(Fractional Open-Circuit Voltage,FOCV),并根据纹波大小动态调节变换器的工作模式,实现阻抗匹配。为了尽可能减小因采样带来的能量损失,采用可片上全集成的较小的采样电容,并逐周期的进行开路电压采样和计算,实现了对源功率变化的高精度追踪。仿真结果表明,所提出的追踪算法能够实时监测能量源的状态,具有高的追踪速度和追踪精度,且采样时间仅需100 ns。能量源功率在1μW~10 mW范围内变化时,最短的追踪时间仅需4.37μs,追踪精度可达99.7%。

The various types of energy sources exist in the environment tend to have different impedance characteristics as well as output power ranges.In order to improve the energy extraction capacity of the energy harvesting system,reasonable design of interface circuit is crucial.Based on this,by focusing on the study of weak DC characteristics and high-efficiency collection and conversion of Photovoltaic(PV)energy sources in the environment,and building upon the conventional Open-Circuit Voltage(OCV)method,this work proposes a predictive algorithm for real-time Maximum Power Point Tracking(MPPT).This algorithm adopts the fractional Open-Circuit Voltage Method(FOCV)according to the output characteristics of the energy source,and dynamically adjusts the operating mode of the converter according to the ripple size to achieve impedance matching.In order to minimize the energy loss caused by sampling,a compact on-chip sampling capacitor is employed,enabling per-cycle open-circuit voltage sampling and computing for highly accurate tracking of source power variations.The simulation results show that the proposed tracking algorithm can monitor the status of the energy source in real time,with high tracking speed and tracking accuracy,and the sampling time is only 100 ns.When the energy source power varies in the range of 1μW-10 mW,the shortest tracking time is only 4.37μs,and the tracking accuracy can reach 99.7%.