Multi-Motor AC Battery Heating With D-Axis Current Control

The patent enables the battery pack to heat itself by utilizing the AC current drawn during charging. The battery's internal resistance converts electrical energy directly into thermal energy, eliminating the need for external heating devices or complex thermal management systems. This self-heating approach resolves the contradiction by maintaining optimal battery temperature without adding system complexity.

The patent converts the previously harmful effect of resistive heating (which was considered energy loss and heat generation to be managed) into a beneficial self-heating mechanism. By intentionally utilizing the battery's internal resistance during AC charging, the system transforms what was a thermal management problem into a solution, eliminating the need for external heating systems.

The patent implements a feedback control system that continuously monitors motor temperature and adjusts d-axis current injection accordingly. Temperature sensors provide real-time feedback to the controller, which modulates the heating current to maintain motors within safe temperature ranges while still delivering effective battery heating. This feedback mechanism resolves the contradiction by balancing heating power delivery with motor thermal protection.

The system applies d-axis current injection at levels that provide sufficient battery heating without exceeding motor thermal capacity. Rather than applying maximum possible heating power continuously, the system uses controlled, partial action that achieves the necessary battery temperature rise while keeping motor temperatures within acceptable limits through moderate current levels and intermittent application.