多电平并网逆变器H桥功率跟踪及功率匹配控制

摘要

The H⁃bridge cascaded multilevel inverter can realize the single⁃stage grid⁃connection of photovoltaic(PV)cell. However,as this system has only once energy conversion in each H⁃bridge module,besides the conventional inverter control and grid⁃connected control,the maximum power point tracking(MPPT)of PV cell connected with each H⁃bridge module and H⁃bridge power matching should also be considered. The control method of adding a MPPT controller into each H⁃bridge module is proposed to make the PV cells connected with each H⁃bridge module work at the maximum power point respectively,which can improve the MPPT accuracy and stability of each H⁃bridge module effectively in the condition of imbalance illumination. According to the voltage error of each H⁃bridge module in the maximum power tracking process,the amplitude of SPWM modu⁃lating wave of each H⁃bridge module is controlled proportionally to match the maximum output power of PV cells with each H⁃bridge transmission power. The system was tested on Matlab/Simulink simulation platform. The system feasibility and reliability were verified by taking 7⁃level cascaded H⁃bridge PV grid⁃connected inverter as an instance.%H桥级联多电平逆变器可实现光伏电池单级式并网，但是由于该系统只在各H桥单元存在一次能量变换，除了要考虑常规逆变器控制及并网控制外，还需要同时考虑到各H桥单元所接光伏电池最大功率点跟踪（MPPT）及H桥传输功率匹配的问题。对此提出对每个H桥单元加入一个MPPT控制器的控制方法，使得各H桥所接光伏电池均能工作在各自的最大功率点，能有效提高各H桥单元光照不均衡条件下MPPT跟踪的准确性和稳定性，同时基于各H桥单元最大功率跟踪过程中的电压误差，对各H桥的SPWM调制波幅值进行比例调节，从而实现各H桥传输功率与光伏电池最大输出功率相匹配。最后在Matlab/Simulink仿真平台上进行了系统的仿真实验，结果表明以七电平级联光伏并网逆变器为例证实了该系统的可行性和可靠性。