具有非正弦功率解耦能力的光伏微逆变器有源功率解耦改进前馈控制

In single-phase power conversion systems, there is an inherent difference between the dc-side constant and ac-side oscillating power, and power decoupling is required especially in applications like photovoltaic (PV) inverters. Active power decoupling (APD) converters are often used to balance instantaneous power while reducing the size of dc link capacitors and improving the system reliability. Conventionally, APD converters are controlled to decouple only sinusoidal power at double-line frequency. However, the control is further complicated when nonsinusoidal power is delivered due to nonlinear circuit components, nonlinear loads, or grid distortions. This article proposes an improved feedforward APD control scheme with the capability of decoupling nonsinusoidal power, which has application in single-phase systems, particularly all types of PV microinverters. The proposed feedforward control includes the capacitor voltage calculation under arbitrary power harmonics and a dead-time compensation to increase the accuracy of duty prediction. The proposed algorithm can work as open-loop control to eliminate APD sensors and can serve as a feedforward term in closed-loop control to improve power decoupling performance, thereby simplifying the controller design. The proposed approach is experimentally verified using a dc-parallel APD prototype, a 50 V 250 W microinverter with nonlinear ac capacitor, and a diode rectifier load.