Thermal performance analysis of 3L-ANPC rotor-side converters for DFIG wind drivetrain

In DFIG drivetrain, traditional two-level (2L) rotor-side converter (RSC) suffers from high thermal stress during its operation with high rotor current at low slip frequency. This paper presents the application of a three-level (3L) ANPC converter as the RSC in DFIG drivetrain. The thermal performance of the 3L-ANPC RSC is analyzed in details through numerical simulator approach for a wide operating range of DFIG RSC, and compared with the traditional 2L RSC employing continuous PWM and 60° DPWM modulation. The results show that 3L-ANPC RSC can effectively reduce device thermal stress across a wide operating range, especially at low slip frequency operation, of the RSC. This benefit enables improved reliability and lifetime of the RSC and DFIG wind drivetrain, and also indicates the capability to increase power rating and power density of the system.