基于电容电流状态估计的MMC多管开路故障诊断方法

MMC Multiple IGBT Open-circuit Fault Diagnosis Method Based on Capacitor Current State Estimation

目前,模块化多电平换流器(modular multilevel converter,MMC)多管开路故障定位方法存在故障阈值难选择、计算过程复杂、需增加额外检测环节等难题。为了解决上述问题,文中基于故障状态下子模块电容电流实际路径与理论路径对比分析,提出将子模块电容电流的理论值和实际值误差作为新的故障诊断特征。采用无模型、鲁棒性强的最小二乘支持向量机最小二乘支持向量机(least square support vector machine,LSSVM)网络作为新的故障定位方案,实现子模块多管开路故障的快速定位。所提方法通过建立子模块电容电流估计方程,基于一阶欧拉近似原理,可通过子模块电容电压估计其电流值,无需增加额外的电流传感器。且相较于现有基于电容电压的故障特征,该特征可在电容电压未严重偏离正常值时,快速反映子模块故障状态。最后,通过Simulink仿真和StarSim硬件在环实验平台,验证所提故障定位策略的有效性。

At present,the fault location method of modular multilevel converter(MMC)has many problems,such as difficult fault threshold selection,complicated calculation process and extra detection link.In order to solve the above problems,this paper proposes the error between the theoretical and actual values of submodule capacitance current as a new fault diagnosis feature based on the comparison analysis between the actual and theoretical paths of sub-module capacitance current under the fault state.A model-free and robust least square support vector machine(LSSVM)network is used as a new fault location scheme to realize the fast location of submodule multi-tube open-circuit faults.The proposed method can estimate the current value of a submodule from its capacitance voltage without adding additional current sensors by establishing the submodule capacitance current estimation equation based on the first-order Euler approximation principle.Compared with existing capacitor voltage-based fault signatures,this feature can quickly reflect submodule fault conditions when the capacitor voltage has not deviated significantly from normal values.Finally,the correctness and effectiveness of the proposed fault location strategy are verified by using Simulink simulation and StarSim hardware-in-the-loop experimental platform.