Part one? Limitations of heat pump system
At present, the air conditioning system of all new energy vehicles mainly has cooling function and heating function, and the refrigeration basically adopts electric compression refrigeration. The heating scheme mainly includes? PTC (liquid/air) and heat pump system. Heat pump is a device that transfers heat energy from low heat source to high heat source, and changes the heat transfer direction by exchanging the functions of evaporator and condenser. The types of heat pump systems mainly include direct heat pump air conditioning system, indirect heat pump air conditioning system and direct heat pump air conditioning system with air supply and enthalpy increase. The limitation of low temperature is that the outdoor heat exchanger is frosted, and the COP heating energy efficiency ratio is strongly related to the ambient temperature (the ratio of refrigeration/heating generated in refrigeration/heating cycle to the power consumed by refrigeration/heating). The direction in the industry is the change of refrigerants and auxiliary measures, as shown in the following figure.
Figure 1? Combination of heat pump and +PTC in existing electric vehicle air conditioning system
Part two? Tesla's method
Tesla cancelled the high-voltage PTC in the design (the hydrothermal PTC was cancelled on Model 3), but in Model? Y is equipped with a low-voltage PTC integrated in the blower of the air conditioning system. Vehicle heat pump system includes compressor, engine room condenser, engine room evaporator, engine room blower and cooler, which integrates battery system, power electronics PCS+ drive system and system loop of the whole vehicle.
The whole physical structure is shown in the following figure:
Figure 2? Tesla model? Practice of y
As shown below, Tesla amplifier 12V? PTC is also a supplementary puzzle of heat pump system, which is completely a green leaf in terms of the cost and power of heat generation.
Figure 3? Models? Y's heat pump system
In this system, I am surprised that the working mode set by Tesla is set according to external parameters, and the whole system is very complicated. As shown in the figure below, Tesla has divided 12 working modes:
Table 1? Working mode of vehicle thermal management system
However, the kernel is divided according to the ambient temperature and battery temperature, as shown in the following figure:
●? COP= 1: The heat pump system does not work, mainly when the ambient temperature is very low (-20℃). A special way is adopted here. According to the previous treatment method, the driving system is blocked, the control algorithm of the compressor is changed, and a motor is used as the heater. (that? Control? Electronic? May? Control? That? Compressor? Where to? Operation? Are you online? Answer? Lossy? mode？ Are you online? Which one? That? Compressor? Generation? Heat)
●? COP= 1~2: When the temperature ranges from-10℃ to 10℃, the mixing mode will be started, and when the heat is from 12V? PTC, and then partial self-heat pump.
●? COP>& gt 1: This is the high efficiency area of heat pump, and the heat pump system is the most important heating mode at this time.
Figure 4? There are different modes to divide COP of heat pump.
In fact, these 12 modes are operated by vehicles themselves. The main input parameters include the destination and route that the owner needs to drive, the environment (temperature), the weather (humidity), the internal parameters of the vehicle (including the operating parameters of battery SOC, Soh and thermal management) and so on. This is a very delicate process, and there may be different working modes and requirements definition and division in the experimental verification environment. In fact, it may be more than that, or it may be simplified to a certain extent. This method can only be carried out in the upper controller with high computing power, and then the commands are issued one by one.
Figure 5? Working mode of heat pump 1
Figure 6? Operating mode of heat pump 2
The previous motor waste heat heating mode actually exists in the above specific mode, that is, the use of compressor has also been migrated and entered the high loss mode. I think Tesla's penetration of the way parts are used has really pushed the parts manufacturers into the corner. You just need to know about hardware design and manufacturing? Whatever you want. Don't worry about how to use it I'll do it. Follow the basic warranty and life terms, and the subsequent processing will be adjusted according to the practice of the software.
Figure 7? In several modes, the compressor becomes a heater.
Summary:
I think from several aspects, Tesla has changed the relationship between software and hardware, changed the relationship between car companies and suppliers, and changed the cooperative concept of different system designs within car companies. This new organization method is difficult for traditional car companies to keep up in the short term.
Author's brief introduction: Zhu Yulong, senior engineer of three electric systems and automotive electronics for electric vehicles, is the author of Hardware Design of Automotive Electronics.
Figure | Zhu Yulong? Network and related screenshots
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.