The semi sealed compressor in a cold storage is used in a vapor compression refrigeration system to elevate the refrigerant from low pressure to high pressure, and continuously circulate the refrigerant, thereby allowing the system to continuously discharge internal heat into an environment higher than the system temperature. The refrigeration compressor is the heart of the refrigeration system, which inputs electrical energy through the compressor to discharge heat from low-temperature environments to high-temperature environments. The energy efficiency ratio of the refrigeration compressor determines the energy efficiency ratio of the entire refrigeration system. Due to the frequent changes in ambient temperature, the compressor is mostly in a partial load state, so the compressor needs to have energy regulation.