矿用NPC三电平逆变器开关管开路故障诊断方法

Open-circuit fault diagnosis method for switching tube of mine NPC three-level inverter

矿井提升机、带式输送机中电动机驱动系统的变频器大多采用中点钳位式(NPC)三电平逆变器,该逆变器开关管数量多、运行频率高,在短时间内高频率切换开关工作状态和在复杂工作环境下容易出现开关管开路故障,且故障信号具有非平稳特性。现有NPC三电平逆变器开关管故障诊断方法存在故障特征提取困难、计算量大、故障准确率较低等问题。针对上述问题,提出了一种基于概率神经网络(PNN)的矿用NPC三电平逆变器开关管开路故障诊断方法。首先利用示波器采集逆变器三相相电压信号,并对相电压信号进行去噪、归一化等处理。然后利用Clark与Park变换将三相相电压转换为两相旋转(d−q)坐标系电压,利用经验模态分解(EMD)将d轴电压分解为多个本征模态分量(IMF),对于不同的开路故障,计算各IMF的方差贡献率,得出第2、第3、第8个IMF的方差贡献率相差较大,以这3个IMF代表不同的开路故障,并计算出它们的均值、均方差和方差,作为逆变器开关管开路故障特征向量。最后将特征向量输入PNN中进行训练与分类,实现NPC三电平逆变器开关管开路故障诊断。实验结果表明,与基于卷积神经网络(CNN)和支持向量机(SVM)的故障诊断方法相比,基于PNN的矿用NPC三电平逆变器开关管故障诊断方法具有更高的故障诊断准确率,平均故障诊断准确率达97.75%。

The inverter of the motor drive system in the mine hoist and belt conveyor mostly adopts neutral point clamped(NPC) three-level inverter. This inverter has a large number of switching tubes and high running frequency. Switching the working state of the switching tubes at high frequency in a short time and in complex working environment are prone to open-circuit fault. The fault signal has non-stationary characteristics. The existing fault diagnosis method for switching tube of NPC three-level inverter has the problems of difficult fault feature extraction, large calculation amount, and low fault accuracy. In order to solve the above problems, an open-circuit fault diagnosis method for switching tube of mine NPC three-level inverter based on probabilistic neural network(PNN) is proposed. Firstly, the phase voltage signals of three-phase of inverter are collected by oscilloscope. The phase voltage signals are processed by denoising and normalization. Secondly, the three-phase voltage is converted into two-phase rotating(d-q) coordinate system voltage by Clark transform and Park transform. The d-axis voltage is decomposed into multiple intrinsic mode function(IMF) using empirical mode decomposition(EMD). For different open-circuit faults, the variance contribution rate of each IMF is calculated.The variance contribution rates of the second, third and eighth IMF differ greatly. The three IMF represent different open-circuit faults. The mean, mean square and variance of the second, third and eighth IMF are calculated as the open-circuit fault feature vector of the inverter switching tube. Finally, the feature vector is input into the PNN for training and classification. The open-circuit fault diagnosis of the NPC three-level invert switching tube is realized. The experimental results show that the fault diagnosis method based on PNN has higher fault diagnosis accuracy than the fault diagnosis method based on CNN and SVM, and the average fault diagnosis accuracy reaches 97.75%.