单相级联H桥光伏并网逆变器功率平衡控制策略研究

Research on Power Balance Control Strategy for Single-phase Cascaded H-bridge Photovoltaic Grid-connected Inverter

级联H桥CHB(cascaded H-bridge)光伏并网逆变器采用独立的最大功率点跟踪MPPT(maximum power point tracking)控制可以有效地提高对太阳能的利用率。但是,独立MPPT控制时由于光照不均匀等因素会使得CHB逆变器出现输出功率不平衡的问题,从而导致并网电流质量变差,甚至系统工作不稳定。针对这一问题,提出了一种利用多个占空比前馈补偿分量结合多维调制原理对各个级联单元的调制信号分别进行控制的功率平衡方法。该方法使得各单元直流侧光伏板的最大输入功率与交流侧的输出功率保持平衡,同时还能够改善光照不均匀时的并网电流质量。仿真实验结果验证了该方法的有效性和正确性。

The independent maximum power point tracking(MPPT)control of a cascaded H-bridge(CHB)photovoltaic grid-connected inverter can effectively improve the utilization of solar energy.However,due to factors including illumination imbalance,the problem of power imbalance may arise in the CHB inverter,which results in deteriorated grid current or even system instability.In this paper,a power balance control method is proposed,in which the modulation signal of each cascaded unit is controlled separately by combining several duty cycle feed-forward compensation amount and the multi-dimensional modulation principle.As a result,the output power on the AC side of each unit is balanced with the maximum input power of the PV panel on the DC side.Meanwhile,it can improve the quality of gridconnected current when the illumination is uneven.Simulation and experimental results verified the validity and correctness of the proposed method.