LLC converter is widely applied to PV micro-inverter due to such good characteristics as high efficiency,broad ranging gain and vast changing load.An MPPT algorithm utilizing iterative approaches was proposed here to improve the imprecise MPPT resulting from imprecise input current detection in the front-end LLC converter stage.Power calculation through detections in back-end inverter stage was handled with interval iterative approaches for precise MPPT.The back stage power calculating,not only offers a more precise calculated power thanks to avoidance of input current detecting error,but also brings a micro-inverter with low cost and less complexity because of removing two isolated detecting circuit on input side of front stage.Finally,a PV micro-inverter of 250 W was built.The prototype indicates that the adopted MPPT is of excellent precision and fast response,thus verifying the validity of the proposed scheme.%针对LLC变换器作为前级拓扑时在输入侧电流采样不准确所导致的MPPT跟踪精度问题,提出了采用迭代式的MPPT方法.采用后级逆变侧采样量进行功率计算,通过区间迭代收敛的方式进行MPPT跟踪.后级功率计算避免了LLC变换器输入电流采样误差,提高了功率计算精度,复用已有采样电路减少了前级输入侧两个隔离采样电路,有效降低了微功率逆变器的硬件成本及复杂度.最后研制了一台250 W的微功率光伏逆变器试验样机.试验表明,采用MPPT方法跟踪速度快、精度高,验证了所提方案的正确性.
展开▼
