基于运行模式分析的逆变器功率管开路故障诊断方法

A Novel Diagnostic Technique for Open-switch Faults of Inverters Based on Operating Mode Analysis

提出一种新型逆变器功率管开路故障的在线诊断与定位方法。该方法在逆变器开关函数模型和运行模式分析的基础上,根据故障和正常状态下桥臂下管承受电压的不同,采用简单的硬件电路来实现,具有成本低、可靠性高、诊断时间短、适用性强等优点。对逆变器的运行模式进行研究,分别对正常状态和上下管开路故障状态时下管电压的实际值进行分析。分析结果表明,与由开关函数模型得到的下管电压估计值相比,上管和下管开路故障将产生不同的误差电压。另外,功率管开关延时、死区时间及测量噪声也会引起误差电压的产生,为了保障诊断的有效性需要加以消除。对于开关延时及测量噪声带来的误差电压,采用阈值比较和脉宽限制的方法将其滤除;同时通过将误差电压与开关信号进行调制,有效地消除了死区时间内的误差电压。给出硬件实现方法,在永磁同步电机矢量控制系统中进行实验验证。该方法不受闭环控制策略的影响,从表现出故障态到诊断输出的时间在10μm以内。

A novel real-time diagnostic and locating technique for open-switch faults in inverters was proposed in this paper. Based on the switching function model and operating modes of the inverter, the method is implemented with simple hardware circuits according to different voltages of the lower switches between faulty and normal conditions, which has advantages of low cost, high reliability, short diagnostic time and good applicability. The operating modes of inverters were researched and the real voltages of the lower switches under both normal condition and the upper and lower switches open-circuit faults were analyzed. The analytic results indicate that different error voltages are derived by the upper and lower switches open-circuit faults respectively, comparing with the estimated voltages of lower switches deduced from the switching function model. Otherwise, error voltages can be developed by switching delay, dead time and measurement noise, which need to be eliminated. Threshold compares and pulse-width limits are used to filter the error voltages coming with switching delay and measurement noise. In addition, in order to eliminate the error voltages during the dead time, the error voltages are modulated with corresponding switching signals. This paper presented a realization scheme using hardware circuits, and simulations and experiments were completed in field-oriented control system of permanent magnet synchronous motor. The results validate the proposed method and indicate that the method is immune to closed loop control strategies. Fault detection can be achieved within 10 μm.