Air conditioner heating PTC power control method

Abstract

The invention relates to the technical field of new energy automobile control, in particular to an air conditioner heating PTC (Positive Temperature Coefficient) power control method which specifically comprises the following steps: S1, judging whether an enabling permission condition of a PTC heater is met or not, S2, sending a PTC control enabling signal, controlling a contactor in a high-voltage loop to be closed and controlling the PTC heater to release heating power, and S3, controlling the PTC heater to release heating power. S4, the VCU calculates the available power of a motor system in real time, and the VCU calculates the available maximum torque of a motor in real time, so that the problem that the power of the whole vehicle is possibly insufficient due to the fact that power consumption calculation is inaccurate at the present stage and the dynamic property of the whole vehicle is weakened at some key times is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicle control, and in particular to a method for controlling PTC power of air-conditioner heating. Background Art

[0002] Pure electric vehicles do not have traditional engines and cannot provide heating water for air conditioning. Therefore, electric vehicles are usually equipped with PTC heaters for heating to meet the heating needs of the cockpit. PTC generally refers to semiconductor materials or components with a large positive temperature coefficient. The PTC usually mentioned refers to positive temperature coefficient thermistors, or PTC thermistors for short. PTC thermistors are a typical semiconductor resistor with temperature sensitivity. In electric vehicles, PTC is a high-voltage component and a resistive component with its own characteristics. When the air conditioning and heating needs are turned on during driving, the power battery of the vehicle will be consumed, which has a great impact on the vehicle's endurance, power, and comfort.

[0003] There are many models equipped with PTC heaters on the market, but most PTCs do not have controllers. Therefore, when performing energy management, many common methods directly calibrate the power consumption of PTC to a maximum value. This setting method will cause the high-voltage PTC to consume a large amount of power on some large trucks. For example, some may exceed 10kw. If the power consumption is not calculated accurately, the power of the entire vehicle will be weakened at certain critical times, which may cause the entire vehicle to be underpowered, such as being unable to climb hills, affected acceleration performance, and the maximum speed not meeting the driver's expectations. Especially in cold winter, drivers usually turn on the air conditioner for heating. If the PTC power value is not handled properly, the power of the entire vehicle will be worse. Summary of the invention

[0004] The present invention provides an air-conditioning heating PTC power control method, which uses a reasonable PTC power request value to manage the power demand of the whole vehicle, so that the power flow of the whole vehicle can be better distributed and managed, and the power performance of the whole vehicle can be guaranteed. The problem that the power consumption calculation at the current stage is inaccurate will weaken the power performance of the whole vehicle at certain critical times, thereby causing the whole vehicle to have insufficient power can be solved.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: an air conditioning heating PTC power control The method specifically includes the following steps: Step S1, judging whether the following enabling conditions of the PTC heater are met: 1.1, the vehicle high voltage is ready; 1.2, the battery discharge power is greater than the calibration threshold; 1.3, the vehicle battery soc is greater than the calibration value threshold; 1.4, the driver requests to turn on the PTC heating function; Step S2: after all the conditions in Step S1 are met, a PTC control enabling signal will be issued to control the contactor in the high-voltage circuit to close, at which time the PTC heater will obtain high voltage electricity, thereby releasing heating power; Step S3, the VCU calculates the available power of the motor system in real time, and the calculation formula is: motor available power = battery current maximum discharge power - heater PTC rated power consumption - DCDC power consumption - high-voltage air conditioning refrigeration power consumption - vehicle other high-voltage power consumption; Step S4, the VCU calculates the available maximum torque of the motor in real time, T = motor available power * 9550 / N, N is the real-time speed of the motor.

[0006] It is further defined that the power consumption of the heater PTC = U* (U / R), where U represents the high voltage value loaded on the PTC, and R is the resistance value when the PTC is just turned on. The calibration curve set in the VCU can be obtained by looking up the table. The input is the ambient temperature, and the output is the resistance of the PTC heater. After the PTC is heated for a certain period of time, the PTC power value tends to stabilize. At this time, the power value of the PTC heater is the power calibration value when the PTC is at a basically constant temperature.

[0007] Further limitation, VCU will correct the PTC power according to the wind speed gear sent by the air-conditioning system. When the air-conditioning wind speed gear is 1, the wind speed is 2m / s, and the corresponding correction coefficient f=0.4; when the air-conditioning wind speed gear is 2, the wind speed is 4m / s, and the corresponding correction coefficient f=0.6; when the air-conditioning wind speed gear is 3, the wind speed is 6m / s, and the corresponding correction coefficient f=0.8; when the air-conditioning wind speed gear is 4, the wind speed is 8m / s, and the corresponding correction coefficient f=1. The correction coefficient can be tested and the value can be changed according to the vehicle condition.

[0008] It is further defined that after the PTC has worked for a certain period of time, the power will have a corresponding attenuation, and the power attenuation strategy must be designed to calculate the attenuated power after the rated voltage is applied for running time. Logic settings are performed in the VCU, and a one-dimensional table is set. The input signal of the table is the PTC cumulative working time h, and the output is the power attenuation coefficient f.

[0009] It is further defined that the calculation formula for the available power of the motor system described in step S3 is: motor available power = battery current maximum discharge power - (heater PTC rated power consumption * f air conditioner wind speed gear adjustment coefficient * rate attenuation coefficient f) - DCDC power consumption - high-voltage air conditioning refrigeration power consumption - power consumption of other high-voltage components of the vehicle.

[0010] The beneficial effects of adopting the above technical solution are: By correcting and calculating the PTC heater power by taking into account the resistance at the beginning of startup, the air-conditioning gear wind speed adjustment coefficient, and the PTC working cumulative time power attenuation coefficient, the motor drive system can obtain accurate available power, thereby protecting the battery from over-discharge and minimizing the impact on the vehicle's power. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a logic control flow chart of the present invention; Figure 2 It is a dependence diagram of the resistance and temperature of the PTC in the present invention; Figure 3 This is a graph showing the influence of PTC power and wind speed in the present invention. DETAILED DESCRIPTION

[0012] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0013] The present invention is a PTC power control method for air conditioning heating. It uses a reasonable PTC power request value to manage the power demand of the whole vehicle, so that the power flow of the whole vehicle can be better distributed and managed, ensuring the power of the whole vehicle, and solving the problem that the power consumption calculation at the current stage is inaccurate, which will weaken the power of the whole vehicle at certain critical times, thereby causing the whole vehicle to have insufficient power. Specifically, Figure 1-Figure 3As shown, it specifically includes the following steps: Step S1, judging whether the following enabling conditions of the PTC heater are met: 1.1, the vehicle high voltage is ready; 1.2, the battery discharge power is greater than the calibration threshold; 1.3, the vehicle battery soc is greater than the calibration value threshold; 1.4, the driver requests to turn on the PTC heating function; Step S2: After all the conditions in step S1 are met, a PTC control enabling signal will be issued to control the contactor in the high-voltage circuit to close. At this time, the PTC heater will obtain high voltage electricity, thereby releasing heating power; Step S3, the VCU calculates the available power of the motor system in real time, and the calculation formula is: Motor available power = battery current maximum discharge power - heater PTC rated power consumption - DCDC power consumption - high-voltage air conditioning refrigeration power consumption - other high-voltage power consumption of the vehicle; Step S4, VCU calculates the maximum available torque of the motor in real time, T = motor available power * 9550 / N, N is the real-time speed of the motor, the torque of the motor is related to the power of the vehicle, such as climbing grade, maximum speed, acceleration performance, etc. The motor torque is related to the available power of the motor, and the available power of the motor is related to the power consumption of the heater PTC. Therefore, it is unreasonable to directly calibrate the PTC power value to the maximum power value of the PTC, which will affect the power of the vehicle. The resistance value of the PTC is not a constant value, and has a certain relationship with its own temperature. When calculating the power consumption of the PTC, the following calculation method is used, where the heater PTC power consumption = U * (U / R), U represents the high voltage value loaded on the PTC, and R is the resistance value when the PTC is just turned on. The calibration curve set in the VCU can be obtained by looking up the table. The input is the ambient temperature and the output is the PTC heater The resistance of PTC, after a certain period of PTC heating, the PTC power value tends to be stable. At this time, the power value of the PTC heater is the power calibration value of the PTC at the moment of basic constant temperature. At the same time, the VCU will correct the PTC power according to the wind speed gear sent by the air-conditioning system. When the air-conditioning wind speed gear is 1, the wind speed is 2m / s, and the corresponding correction coefficient is f=0.4. When the air-conditioning wind speed gear is 2, the wind speed is 4m / s, and the corresponding correction coefficient is f=0.6. When the air-conditioning wind speed gear is 3, the wind speed is 6m / s, and the corresponding correction coefficient is f=0.8. When the air-conditioning wind speed gear is 4, the wind speed is 8m / s, and the corresponding correction coefficient is f=1. The correction coefficient can be tested and changed according to the vehicle condition. After the PTC has been working for a certain period of time, the power will be attenuated accordingly, and the power attenuation must be strategically designed. For example: in a windless state, the power attenuation rate after applying the rated voltage for 1000 hours is measured, and the power attenuation rate is required to be approximately 8 %; the specific attenuation data can be obtained by experimental testing on the bench; then the VCU logic setting can set a one-dimensional table, the input signal of the table is the PTC cumulative working time h, and the output is the power attenuation coefficient f.

[0014] The available power of the motor system in step S3 can be expressed as: available power of the motor = current maximum discharge power of the battery - (rated power consumption of heater PTC * f air conditioner wind speed gear adjustment coefficient * rate attenuation coefficient f) - DCDC power consumption - high-voltage air conditioning refrigeration power consumption - power consumption of other high-voltage components of the vehicle. By considering the resistance at the beginning of startup, the air conditioner gear wind speed adjustment coefficient, and the power attenuation coefficient of the accumulated working time of the PTC to correct and calculate the power of the PTC heater, the motor drive system can obtain accurate available power, thereby protecting the battery from over-discharge and minimizing the impact on the power of the vehicle.

[0015] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above-mentioned concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A PTC power control method for air conditioning heating, Features: The specific steps include: Step S1, determining whether the following PTC heater enabling conditions are met: 1.

1. The whole vehicle is high voltage ready; 1.

2. The battery discharge power is greater than the calibration threshold; 1.

3. The vehicle battery SOC is greater than the calibration threshold; 1.

4. The driver requests to turn on the PTC heating function; Step S2: After all conditions in step S1 are met, a PTC control enable signal is issued to control the contactor in the high-voltage circuit to close. At this time, the PTC heater will receive high voltage electricity, thereby releasing heating power. Step S3, the VCU calculates the available power of the motor system in real time, and the calculation formula is: motor available power = battery current maximum discharge power - heater PTC rated power consumption - DCDC power consumption - high-voltage air conditioning refrigeration power consumption - other high-voltage power consumption of the vehicle; Step S4, VCU calculates the maximum available torque of the motor in real time, T=motor available power*9550 / N, N is the real-time speed of the motor.

2. The air conditioning heating PTC power control method according to claim 1, Features: The power consumption of the PTC heater = U* (U / R), where U represents the high voltage value loaded on the PTC, and R is the resistance value when the PTC is just turned on. The calibration curve set in the VCU can be obtained by looking up the table. The input is the ambient temperature, and the output is the resistance of the PTC heater. After the PTC is heated for a certain period of time, the PTC power value tends to stabilize. At this time, the power value of the PTC heater is the power calibration value when the PTC is basically at a constant temperature.

3. The air conditioning heating PTC power control method according to claim 2, Features: VCU will correct the PTC power according to the wind speed level sent by the air conditioning system.

4. The air conditioning heating PTC power control method according to claim 3, Features: After the PTC has worked for a certain period of time, its power will decay accordingly. It is also necessary to design a strategy for power decay. The decayed power after the rated voltage is applied for running time is calculated. The logic setting is performed in the VCU, and a one-dimensional table is set. The input signal of the table is the cumulative working time h of the PTC, and the output is the power attenuation coefficient f.

5. The air conditioning heating PTC power control method according to claim 4, Features: The calculation formula of the available power of the motor system described in step S3 is: Motor available power = battery current maximum discharge power - (heater PTC rated power consumption * f air conditioner wind speed gear adjustment coefficient * rate attenuation coefficient f) - DCDC power consumption - high-voltage air conditioning refrigeration power consumption - power consumption of other high-voltage components of the vehicle.

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