多串光伏升压变换器中受电缆不确定性影响的直流母线电容在线退化故障预测

In the application of multistring photovoltaic (PV) power generation, each dc string has a boost converter and the degradation fault of its dc-link capacitor can cause power outage. A comprehensive fault prognosis technology is proposed using the measurable busbar voltage and per-string cable current. The challenge is to avoid the effect of multistring cable uncertainties. First, a 3-D plane y = f is optimized with the information of the series resistance ( R_x ) and capacitance ( C_x ) of dc-link capacitor. The mathematical proof is presented that based on y = f , R_x and C_x are estimated separately by decoupling the cable parameter. Second, a novel degradation indicator D is proposed that combines increasing trends of both R_x and C_x^-1 . The D-based evaluation sensitivity is improved compared with the single estimated parameter. Simulation verifies that the D-based performance is robust to multistring cable uncertainties and varying operating conditions of PV module and load. Online experiments upon the grid-connected platform clarify that the maximum error of parameter estimation is 1.6% and the D-based evaluation resolution relative to R_x is 1.18 dis/m . The breakthrough lies in the mitigation of uncertain cable effect using neither voltage nor current across dc-link capacitors. Convenient implementation and robust performance are emphasized.