Energy storage power supplies generally adopt water-cooled or air-cooled methods to dissipate heat from energy storage components. In energy storage power supplies that use air-cooled heat dissipation, multiple fans are generally installed and distributed in different positions within the energy storage power supply. The energy storage power supply mentioned in this article is the main power source of the vehicle, which uses cold air discharged from the air conditioning system to dissipate heat from the energy storage power supply. Heat dissipation management mainly controls the start and stop of fans in the energy storage power supply and detects fan faults.
1. Overall design of heat dissipation management
The heat dissipation management of energy storage power supply is to control the heat dissipation fan based on the temperature of the energy storage power supply. The fan sucks the air conditioning waste into the energy storage power supply, allowing the waste air to flow through the surface of the energy storage components to achieve cooling. There are a total of 12 fans configured in the energy storage power supply, evenly distributed on both sides of the wall. Divide 12 fans into 3 groups, with 4 fans in each group. The fan drive is controlled at the positive pole of the fan, and the negative pole is uniformly connected to the negative pole of the control power supply. The feedback signal is directly connected to the controller IO interface because it shares ground with the power supply.
The heat dissipation controller obtains the temperature collected by the temperature acquisition unit through the CAN network, analyzes it, takes the average value, and obtains the temperature of the energy storage power supply as the input for control. The cooling controller controls the start and stop of the fan group based on the temperature, and detects the fault status of the fan that is turned on. The control and fault information are sent to the main controller through the 485 bus.
2. Hardware principle of heat dissipation control
The cooling control hardware is mainly divided into CPU minimum system, fan drive circuit, fan detection circuit, CAN and RS485 communication circuit parts. The CPU uses SMT32F103 as the control chip, while STM32F103 is a Cortex-M3 based microcontroller with low cost and two CAN communication interfaces, which can be used for network communication redundancy backup. The system requires that under static conditions, the fan should be in the default off state. Therefore, the positive pole of the fan is connected to the normally open contact of the relay, and ULN2004 is selected as the driving chip, with a driving current of up to 500 mA. Fan detection adopts optocoupler isolation detection. SMT32F103 comes with a CAN controller, and Zhou Ligong’s CTM1051 and RSM3485 transceivers are used for CAN communication and RS485 communication, respectively.
3. Software process
According to system requirements, the fan self checks before entering the temperature control process when turned on. When designing the software, a 75 second power on self-test process is designed to turn on the first, second, and third groups of fans respectively, while detecting the fault status of the fans included in the fan groups that are turned on. After the fan self check is completed, it enters the temperature control process. According to system requirements, turn on the second set of fans when the temperature of the energy storage power supply is ≥ 30 ℃, and turn on all three sets of fans when the temperature of the energy storage power supply is ≥ 35 ℃.
3.1 Fan drive process
In the design of the fan drive process, considering the critical temperature of the fan, in order to avoid frequent fan start and stop caused by temperature collection errors, the temperature amplitude is increased in the design. During the temperature rise process, the second group of fans is turned on when the temperature is between 30 ℃ and 33 ℃, and all three groups of fans are turned on when the temperature is above 35 ℃; During the temperature drop, turn off all fans below 28 ℃.
3.2 Fault detection process
Since the fault signal detected by the fan after control startup is valid, the fan fault is not detected when controlling a certain fan to stop running.
4. Experimental testing
In the tested system platform, 12 fans are divided into 3 groups. The first group contains fans 1, 4, 7, and 10, the second group contains fans 2, 5, 8, and 11, and the third group contains fans 3, 6, 9, and 12. After powering on and starting, the controller enters the fan self check process. The upper computer simulates the temperature of the energy storage power supply to be 21 ℃ and is detecting the first set of fans. After the self check is completed and temperature control is entered, the 5th, 8th, and 11th fans are blocked. When the temperature of the energy storage power supply is simulated to be 35 ℃, all three sets of fans are turned on, and a fault is detected in the 5th, 8th, and 11th fans.
5. Conclusion
A cooling management and control scheme for energy storage power supply has been implemented, which specifically describes the hardware and software scheme of the controller. The cooling fan is controlled based on the input temperature of the energy storage power supply and can detect fan faults in real time. The principle and software strategy of this heat dissipation management can be continuously used in energy storage vehicle applications, with low cost and simple portability.