Generalized DPWM for Thermal Capability Enhancement of Grid-Tied Converters During Asymmetrical Faults

Power electronic converters (PECs) are essential in modern power grids, enabling efficient electrical energy conversion and renewable integration. Grid codes require PEC-based units to remain connected during voltage drops (LVRT) and inject reactive currents to support stability during severe faults. However, the overcurrent capability of PECs is limited by device thermal constraints, primarily represented by their maximum allowable junction temperature. While thermally compensated modulation techniques such as Discontinuous PWM (DPWM) can enhance PEC thermal capability under symmetrical faults, they are less effective during asymmetrical faults, which impose uneven thermal stress across the converter legs. This challenge is remarked by the IEEE 2800-2022 standard, which mandates negative-sequence current injection during LVRT operation. This paper investigates the application of Generalized DPWM (GDPWM) under asymmetrical grid faults and for different positive/negative sequence current injection strategies, focusing on its potential to improve the thermal performance of overloaded converters. The effectiveness of GDPWM is demonstrated through detailed simulations and validated experimentally.