Hybrid electric vehicles are one of the long-term technical approaches for reducing environmental pollution and energy consumption in the automotive industry. The hybrid control unit (HCU) is a key component of hybrid electric vehicles; the core of a hybrid electric vehicle is its hybrid system, whose performance directly determines the overall vehicle performance. Hybrid powertrains, classified by power transmission path, can be series, parallel or series-parallel.

The thermal management system (TMS) ensures the safest possible battery operation and improves battery efficiency by properly managing the temperatures of the drive motor system, traction battery and passenger cabin. The thermal management systems of new-energy vehicles differ significantly from those of conventional internal combustion engine vehicles: battery packs on new-energy vehicles are often temperature-controlled via air conditioning, so the thermal management system must consider not only the cooling of battery packs, power electronics and motors and the heating of battery packs in low-temperature environments, but also the coupled effects with air conditioning and the passenger cabin.