基于空间轨迹分类网络模型的T型逆变器开路故障诊断方法

Open-circuit fault diagnosis method for t-type inverter based on space trajectory classification network model

T型三电平逆变器系统相对传统逆变器具有功率和耐压等级高、电磁干扰小、开关损耗低等优势,广泛应用于中高压交流传动、有源电力滤波以及电力系统无功补偿等领域。随之而来的是T型三电平逆变器功率管的增多带来器件故障率的上升。功率管主要表现为开路故障,这种故障不易发现,将会给系统安全运行带来严重影响,甚至造成整个变流系统的瘫痪。针对T型三电平逆变器功率管开路故障,提出一种基于空间轨迹诊断网络模型的故障诊断方法,以输出相电流为故障诊断变量,对正常、单个功率管开路故障以及多个功率管开路故障情况下的电流空间轨迹进行分析。对于不同情况下的开路故障,空间轨迹的畸变规律与故障表征各不相同。根据空间轨迹故障特征,提出基于分类网络模型的相电流空间轨迹集故障定位方法。该模型将空间轨迹转化为数据点集并进行归一化,利用对称函数与置换网络对数据点集进行处理,得到具备特征辨识能力的故障诊断模型。通过dSPACE实验平台验证,提出的方法可以实现单个及2个功率管故障的有效诊断。同时,该方法在开关频率变化、负载变化以及调制度变化时具有较好的鲁棒性。此外,该方法也适用于轨道车辆两电平及多电平逆变器的开路故障诊断。

Compared with traditional inverters, T-type three-level inverter has the advantages of high power and withstand voltage level, low electromagnetic interference and low switching loss. It is widely used in the fields of medium and high voltage AC drive, active power filter and reactive power compensation of power system.Subsequently, the increase of switch brings the increase of device failure rate. The main fault of switch is open-circuit fault. This fault is not easy to find, which can seriously affect the safe operation of the system, and even can cause the paralysis of the whole converter system. This paper proposed an open-circuit fault diagnosis method for T-type inverter based on space trajectory classification network model. Firstly, phase currents were used as the fault diagnosis variables. The space trajectory under the conditions of normal, single-, and double-switch open-circuit faults were analyzed. For different open-circuit faults, the distortion of space trajectory and fault characterization were different. According to the fault characteristics of space trajectory, a fault diagnosis method based on space trajectory classification network model was proposed. The space trajectory was normalized and transformed into data point set. Then, symmetry function and permutation network were used to form a fault diagnosis model. The model was verified on a dSPACE platform. The results show that it can distinguish both single-and double-switch open-circuit faults effectively. Moreover, the proposed method is robust to different switching frequencies, load condition, and modulation depth. With minor modifications, it can be used in the railway application.