An online thermal monitoring method for converter system based on the extraction of DC bus leakage current

The majority of converter failures are caused by overheating and temperature fluctuation. Therefore, online thermal monitoring methods for converters are necessary to enhance the reliable operation capacity. Conventional thermal monitoring methods mainly focus on a single semiconductor device. The monitoring cost is high, and measuring circuits are difficult for integration. Moreover, converter structure must be adjusted in industrial applications for these methods. To solve these problems, a novel online thermal monitoring method for IGBT-based converter system is proposed. The aim is to obtain an overall temperature evaluation of the converter. First, the leakage current in DC bus (I leakDC ) is selected as an indicator for converter thermal monitoring. Theoretical analysis and offline experiments prove that I leakDC is quasi-exponential to temperature. Second, temperature-related parameters (T CONU and T CONL ) are defined corresponding to I leakDC respectively to characterize the thermal state of converters. Third, an extraction method for I leakDC is proposed based on the state-delay converter control method. Using the online extracted I leakDC , a novel thermal monitoring strategy is developed. Online experiments validate the effectiveness of the proposed strategy in different operating condition. The proposed method gains advantages in low cost, easy integration, feasible and convenient implementation for system-level thermal management.