中文摘要：

级联H桥光伏逆变器各级功率单元可以实现独立的最大功率点跟踪（maximum power point tracking,MPPT）控制,有助于提高系统的效率。但由于遮挡或组件损坏等因素的影响,光伏组件间输出功率不平衡,会使输出功率正常的光伏组件对应的功率单元过调制,导致输出电流性能变差甚至系统不稳定。为此,提出一种具有无功补偿功能的集中控制策略,遵循有功按比例分配和无功按需求分配的原则,保证功率严重不平衡时所有功率单元均不会过调制。仿真结果和实验结果都验证了所提控制策略的有效性。

英文摘要：

Each power unit of the cascaded H-bridge photovoltaic inverter can accomplish maximum power point tracking （MPPT） control independently, which will contribute to increasing efficiency. However, affected by the factor of partial shading or damaged solar cells, the unbalanced output power among solar cells make the normal power units over-modulation, which results in deteriorated grid current even instability. To address power unbalance, a centralized control with the function of reactive compensation is proposed. Following the principle of distributing active power proportionally and reactive power according to requirement, it can ensure that all power units do not suffer from over-modulation. Simulation and experimental results verify the effectiveness of proposed solution.