Centralized Thermal Stress Oriented Dispatch Strategy for Paralleled Grid-Connected Inverters Considering Mission Profiles

Abstract

One of the major failure causes in the power modules comes from the severe thermal stress in power semiconductor devices. Recently, some local control level methods have been developed to balance the power loss, dealing with the harsh mission profile, in order to reduce the thermal stress. However, there is not any specific system level strategy to leverage these local control level methods responding to the multiple inverters situation. Besides, the impacts of these methods on the thermal cycle and lifetime of the power modules in the long-term time scale have not been evaluated and compared yet. Hence, in this article, a centralized thermal stress oriented dispatch (TSOD) strategy is proposed to take full advantage of these local control level methods, including the switching frequency variation and the reactive power injection, to reduce the thermal stresses for multiple inverters. In addition to the PI controller, the finite control set model predictive control (FCS-MPC) is also explored to synergize with the proposed strategy. The results from the real-time model-in-the-loop testing on a four-paralleled-inverters platform, the reliability assessment, and the experiments all validate the effectiveness of the proposed centralized TSOD strategy on the thermal stress reduction.