盲区小的燃料电池并网系统孤岛检测方法

Islanding Detection Method of Grid-connected Fuel Cell System with Smaller Non-detected Zone

为保护系统及人身安全、保障用户供电质量,燃料电池并网系统必须具备孤岛检测功能。文中提出一种检测速度快、盲区小的新型孤岛检测方法——ASMS_Q法。该方法对滑模频率偏移法进行改进,在偏离工频较大区域加入加速增益,并结合q轴无功电流扰动法,在电网断开后,进行更快速地频率扰动,使其超出正常范围,达到过/欠频保护。而且电网正常工作时,给电网注入扰动量很小,对逆变器输出电能质量没有影响。在Q_f-f_0和Q_(f_0)-C_(norm)坐标系下,对比分析了ASMS_Q法及两种传统方法的盲区。仿真和实验结果表明,ASMS_Q法比传统的主动式检测方法盲区更小,检测速度更快,适用于高品质因素的负载。

The function of islanding detection is required of the grid-connected fuel cell system to protect safety of equipment and humans and to maintain the quality of power supply.A novel active islanding detection method with short detecting time and small non-detected zone is proposed.This method is a combination of the adaptive slide mode frequency shift method that adds acceleration gain when frequency is drifted out of grid＇s operational frequency and the q-axis reactive current disturbance method.As the grid is disconnected,the islanding phenomenon is detected by making the frequency disturbance faster and drifting the frequency out of the allowed normal range to result in under/over frequency protection.Moreover,very small disturbance is added to the control signal in this method so that there is no negative impact on power quality when the grid works in the normal state.In the coordinates of Qf-f0 and Qf0-Cnorm,the non-detected zone of the proposed method and two traditional methods are analyzed.Simulation and experimental results show that the method proposed is applicable to loads with high quality factor,shortens the time of islanding detection and is suitable for smaller non-detected zones in comparison to previous methods.