基于阻抗在线观测的光伏逆变器控制策略研究

Research on Control Strategy of PV Inverter Based on Impedance On-line Estimation

光伏逆变器通常采用最大功率跟踪算法尽全力向电网注入有功功率,并不参与电网电压的控制。只有当电网电压超过了保护阈值,光伏逆变器才停止工作以避免引发过电压故障。提出一种光伏逆变器的电网电压控制策略,用以改善电网电压水平,使得光伏逆变器在非最优电网电压情况下依然可以向电网输送电能。根据电网电压控制效果由电网阻抗的阻抗比R/X决定的基本原理,所提出的控制策略在线观测电网阻抗比,实时控制光伏逆变器注入电网的有功功率和无功功率,改善光伏逆变器的电网电压控制效果。所提出的控制策略不仅适用于光伏逆变器,同样也适用于其他类型的分布式发电并网逆变器。

PV inverters commonly do not participate in the grid voltage control and use maximum power point tracking algorithm to inject power into the grid as much as they can.Only when the grid voltage level surpasses the protection threshold,the inverters shut themselves down to avoid overvoltage faults.A grid voltage control strategy of PV inverter was proposed to improve the grid voltage level,so that the PV inverters can still generate power to the grid under the condition of suboptimal grid voltage.According to the basic principle that the grid voltage control effect depends on the grid impedance ratio R/X,the proposed control strategy observes the grid impedance ratio on-line and controls the active power and reactive power injected into the grid by the PV inverter in real time,to improve the grid voltage control effect of the PV inverter.The proposed control strategy is not only suitable for PV inverters,but also suitable for other types of distributed generation grid-connected converters as well.