光伏微逆变器电流传感器和功率管开路故障诊断

当电流传感器出现性能蜕化、故障或失效时,光伏微逆变器系统的输出会受到严重影响,甚至微逆变器系统其他部件有可能被直接损坏而导致整个系统永久失效;微逆变器系统中反激式变换器功率管的开路故障会引起2个交错支路电流不平衡,导致输出电流波形畸变率变大.为此,提出一种基于状态观测器的光伏微逆变器电流传感器和功率管开路故障诊断方法.建立两路反激式变换器的数学模型;构建状态观测器以实现对两路反激式变换器原边电流的在线估计,并生成残差;将残差与阈值进行比较,实现对微逆变器系统中电流传感器与功率管的实时故障诊断.仿真结果验证该方法可行且有效.

Fault diagnosis on current sensors and open-circuited transistor of photovoltaic micro-inverter

Current sensors are an essential part of the photovoltaic micro-inverter system, the control loop rely heavily on the current sensors. Erroneous or corrupted measurements, due to current sensors failures, perturb seriously the performance of the micro-inverter system and may cause system shutdown. In addition, an open-switch fault in the converters may cause unbalanced input dc currents between the two lines of interleaved flyback converters, which increases of the output current distortion rate. In this paper, an observer-based fault diagnosis method for current sensors and an open-switch fault are proposed for a micro-inverter system. First, a mathematical model of the two flyback converters is established; second, a state observer is applied to estimate the two currents of the flyback converters online and generate corresponding residuals. Finally, the faults are detected by comparing the residuals with the thresholds. The feasibility and effectiveness of the proposed method has been verified by the simulation results.