A battery heating control method suitable for rapid cold start in extremely cold environments

Abstract

This invention provides a battery heating control method suitable for rapid cold start in extremely cold environments. It allows for the flexible construction of a system with heating and charging functions for extreme conditions such as extreme cold in the wild. It offers three operating modes: on-board power, mobile power, and stationary power, each executing various control methods to heat and charge the internal battery and the external battery in the vehicle, as well as to rapidly start the vehicle in conjunction with a starter generator. Compared to existing technologies, this invention significantly reduces the complexity of the system structure and control strategy while achieving rapid battery warming and vehicle starting. Furthermore, it designs closed-loop control strategies for each mode that can adjust the heating current amplitude and frequency, as well as the charging voltage and current in real time, achieving numerous beneficial effects such as higher heating efficiency and uniformity, and effectively reducing low-temperature battery damage.

Description

Technical Field

[0001] This invention belongs to the field of battery thermal management technology, specifically relating to a battery heating control method suitable for rapid cold start in extremely cold environments. Background Technology

[0002] When used in extremely cold environments, batteries often fail to maintain the same performance levels as in normal temperatures. Temperature variations can also lead to reduced lifespan and safety hazards. For vehicles performing special operations in the field, batteries in low temperatures often cannot provide sufficient power to start the engine, significantly limiting vehicle use. Existing heating methods for vehicle batteries mostly employ external heating with PTC heating elements or circulation systems, which suffer from low heating efficiency, encroachment on limited vehicle space, and high costs. While some heating systems utilizing readily available vehicle components can reduce the size and cost of these existing technologies, the stall torque generated when the vehicle is stationary is difficult to eliminate, severely impacting vehicle movement. Therefore, it is necessary to improve vehicle rapid cold start and fast charging methods for extreme conditions such as extreme cold in the field. Summary of the Invention

[0003] In view of this, and in response to the technical problems existing in this field, the present invention provides a battery heating control method suitable for rapid cold start in extremely cold environments, which performs corresponding control for three working modes: vehicle power supply, mobile power supply and stationary power supply.

[0004] First, a control system including the following modules is constructed: internal battery E1, internal battery E2, 3 sets of bridge arms, supporting capacitors, 3 inductors, DC bus, external battery, and AC / DC module; for any operating mode, 6 power switching transistors are used to form the 3 sets of bridge arms, with each pair of power switching transistors forming one bridge arm. The neutral point of each bridge arm serves as the AC side and is connected to one end of an inductor and a current sensor respectively; the two ends of each bridge arm are connected to both sides of the DC bus respectively.

[0005] For the vehicle-mounted power supply mode, the coil windings of the vehicle's starter generator and the switching elements in the drive module are used as the inductors and bridge arms, and the neutral points of E1 and E2 are connected to the neutral point of the motor through a switch. For the mobile power supply mode and the stationary power supply mode, the vehicle's starter battery is used as the external battery, and it is connected to the control system together with the supporting capacitor. One end of the external battery is connected to the other end of one of the inductors, and the other end of the external battery is connected to the negative line of the DC bus, while the positive line of the DC bus is left floating. The two ends of the supporting capacitor are respectively connected to the two sides of the DC bus.

[0006] In the mobile power bank mode, the other two inductors are connected to the two ends of the internal batteries E1 and E2 respectively, and the negative ends of the internal batteries E1 and E2 are connected to the non-floating side of the DC bus. In the fixed power bank mode, the other two inductors are not connected to the system, and the AC / DC module replaces the internal batteries E1 and E2 to establish a connection with both sides of the DC bus.

[0007] After the control system is built, the following controls are executed based on PWM modulation for cold start-up in extremely cold environments for each working mode:

[0008] In the vehicle power mode, the switching of each power switch is controlled to switch the current direction in the system circuit, so that the internal batteries E1 and E2 and each inductor can exchange power to each other and execute the AC heating cycle. When the internal battery temperature and charge meet the starting conditions, the control system operates in inverter mode to drive the starter generator to start the engine. After the engine speed stabilizes, the control system switches to rectification mode to charge the internal battery.

[0009] In the power bank mode, the system first determines whether heating the internal battery is required. If heating is required, the system controls the switching of power switches to change the current direction in the system circuit, allowing the internal batteries E1 and E2 to exchange power with the inductors, executing an AC heating cycle to reach the predetermined temperature. If heating the internal battery is not required or has already been completed, the system controls the current direction in the system circuit to allow the internal batteries E1 and E2, the inductors, the supporting capacitor, and the external battery to exchange power with each other, executing an AC heating cycle to raise the temperature of the external battery. Once the external battery reaches the predetermined temperature, the system determines whether charging the external battery is required. If so, the system uses the switching of power switches to enable the internal batteries E1 and E2, the corresponding bridge arms, and the inductors to form a DC charging circuit, and then charges the external battery.

[0010] In the fixed power supply mode, it first determines whether the external battery needs to be heated. If heating is required, it controls the switching of each power switch to select one bridge arm to work, so that the external battery and its connected inductor can mutually transfer power to perform an AC heating cycle. When the external battery reaches the predetermined temperature, it determines whether the external battery needs to be charged. If so, it uses the industrial frequency AC power input through the AC / DC module to charge the external battery.

[0011] Furthermore, during the PWM modulation process in the vehicle power mode, the temperature and state of charge of the internal batteries E1 and E2 are collected in real time to calculate the optimal AC heating current amplitude and frequency. The amplitude and phase error between the reference current and the collected three-phase current of the starter generator are tracked to provide a reference voltage for PWM modulation. By controlling the upper and lower switches of the three bridge arms to be turned on or off synchronously, the amplitude and phase of the current are adjusted, thereby achieving AC heating without motor output torque, so that the internal batteries E1 and E2 are heated to the predetermined temperature.

[0012] Furthermore, during the PWM modulation process in the mobile power bank mode, the temperature, voltage, and state of charge of each internal and external battery are collected in real time to calculate the optimal AC heating current amplitude and frequency or the voltage and current during the charging process. The calculation results and the current errors of the internal and external batteries collected in real time are tracked to perform individual closed-loop control of each bridge arm, thereby completing the heating of the internal battery, the heating of the external battery, and constant current or constant voltage DC charging.

[0013] Furthermore, during the PWM modulation process in the fixed power supply mode, the temperature and voltage of each internal and external battery are collected in real time, and the optimal AC heating current amplitude and frequency or the voltage and current during AC charging are calculated. The error between the calculation results and the current of the external battery collected in real time is tracked to perform closed-loop control on the selected bridge arm, thereby completing the heating or AC charging of the external battery.

[0014] The battery heating control method for rapid cold starting in extremely cold environments provided by the present invention can flexibly construct a system with heating and charging functions for extreme conditions such as extreme cold in the wild. It provides three operating modes: on-board power, mobile power, and stationary power, and executes various control methods for heating and charging the internal battery and the external battery in the vehicle, as well as for rapidly starting the vehicle in conjunction with the starter generator. Compared with existing technologies, the present invention significantly reduces the complexity of the system structure and control strategy while achieving rapid battery heating and vehicle starting. Furthermore, it designs closed-loop control strategies for each mode that can adjust the heating current amplitude and frequency, and the charging voltage and current in real time, achieving many beneficial effects such as higher heating efficiency and uniformity, and effectively reducing battery low-temperature damage. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the method provided by the present invention;

[0016] Figure 2 The circuit schematic diagram of the system provided by this invention;

[0017] Figure 3(a) is a circuit diagram of AC heating in vehicle power mode;

[0018] Figure 3(b) is a schematic diagram of the control principle of AC heating in vehicle power mode;

[0019] Figure 4(a) is a circuit diagram of AC heating in mobile power supply mode;

[0020] Figure 4(b) is a control principle diagram of AC heating in mobile power supply mode;

[0021] Figure 5(a) is a circuit diagram of AC heating under fixed power supply mode;

[0022] Figure 5(b) is a schematic diagram of the control principle of AC heating under fixed power supply mode. Detailed Implementation

[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a battery heating control method suitable for rapid cold start in extremely cold environments, such as... Figure 1 As shown, corresponding controls are executed for the three working modes: vehicle power supply, mobile power supply, and stationary power supply.

[0025] like Figure 2 As shown, a control system including the following modules is first constructed: internal battery E1, internal battery E2, 3 sets of bridge arms, supporting capacitor C1, 3 inductors L1, L2, L3, DC bus, external battery, and AC / DC module; for any operating mode, 6 power switching transistors Q1 to Q6 are used to form the 3 sets of bridge arms, with each pair of power switching transistors forming one bridge arm. The neutral points P11, P21, and P31 of each bridge arm serve as the AC side and are respectively connected to one end of an inductor and a current sensor; the two ends of each bridge arm are connected to both sides of the DC bus.

[0026] For the vehicle-mounted power supply mode, the coil windings of the vehicle's starter generator and the switching elements in the drive module are used as the inductors and bridge arms, and the neutral points of E1 and E2 are connected to the neutral point of the motor through a switch. For the mobile power supply mode and the stationary power supply mode, the vehicle's starter battery is used as the external battery, and it is connected to the control system together with the supporting capacitor. One end of the external battery is connected to the other end of one of the inductors, and the other end of the external battery is connected to the negative line of the DC bus, while the positive line of the DC bus is left floating. The two ends of the supporting capacitor are respectively connected to the two sides of the DC bus.

[0027] In the mobile power bank mode, the other two inductors are connected to the two ends of the internal batteries E1 and E2 respectively, and the negative ends of the internal batteries E1 and E2 are connected to the non-floating side of the DC bus. In the fixed power bank mode, the other two inductors are not connected to the system, and the AC / DC module replaces the internal batteries E1 and E2 to establish a connection with both sides of the DC bus.

[0028] After the control system is built, the following controls are executed based on PWM modulation for cold start-up in extremely cold environments for each working mode:

[0029] In the vehicle power mode, the switching of each power switch is controlled to switch the current direction in the system circuit, so that the internal batteries E1 and E2 and each inductor can exchange power to each other and execute the AC heating cycle. When the internal battery temperature and charge meet the starting conditions, the control system operates in inverter mode to drive the starter generator to start the engine. After the engine speed stabilizes, the control system switches to rectification mode to charge the internal battery.

[0030] In the power bank mode, the system first determines whether heating the internal battery is required. If heating is required, the system controls the switching of power switches to change the current direction in the system circuit, allowing the internal batteries E1 and E2 to exchange power with the inductors, executing an AC heating cycle to reach the predetermined temperature. If heating the internal battery is not required or has already been completed, the system controls the current direction in the system circuit to allow the internal batteries E1 and E2, the inductors, the supporting capacitor, and the external battery to exchange power with each other, executing an AC heating cycle to raise the temperature of the external battery. Once the external battery reaches the predetermined temperature, the system determines whether charging the external battery is required. If so, the system uses the switching of power switches to enable the internal batteries E1 and E2, the corresponding bridge arms, and the inductors to form a DC charging circuit, and then charges the external battery.

[0031] In the fixed power supply mode, it first determines whether the external battery needs to be heated. If heating is required, it controls the switching of each power switch to select one bridge arm to work, so that the external battery and its connected inductor can mutually transfer power to perform an AC heating cycle. When the external battery reaches the predetermined temperature, it determines whether the external battery needs to be charged. If so, it uses the industrial frequency AC power input through the AC / DC module to charge the external battery.

[0032] In a preferred embodiment of the present invention, the system composition and control strategy for each working mode are specifically explained as follows:

[0033] For the on-board power supply mode, as shown in Figure 3(a), the system specifically includes: internal battery E1, internal battery E2, supporting capacitor C1, three sets of bridge arms composed of upper power switches Q1, Q2, Q3 and lower power switches Q4, Q5, Q6 respectively, starter generator M1 and its internal three-phase windings L4, L5, L6, and neutral point connection switch SW1. The leads of the on-board starter generator's three-phase windings L4, L5, and L6 are connected to the other ends of the inductors P12, P22, and P32 respectively. The neutral point of the on-board starter generator is connected to the neutral point of the starting batteries E1 and E2 through the neutral point switch SW1.

[0034] The optional workflow for onboard power modes is as follows: Figure 1 As shown, the process includes: First, determining whether heating of the starter battery is necessary based on its temperature and state of charge. If heating is not required, the neutral point connection switch SW1 is open, and the starter generator M1 is controlled to run rapidly to drive the engine via power switches Q1, Q2, Q3, Q4, Q5, and Q6. If heating is required, the neutral point connection switch SW1 is closed, and Q1, Q2, and Q3 are simultaneously turned on, as are Q4, Q5, and Q6, with the former and latter being complementary. Current flows through L4 / 5 / 6. When the battery reaches a suitable temperature and has sufficient charge, it enters inverter mode to drive the motor and start the engine. Once the engine speed stabilizes, it switches to rectification mode to charge the starter battery and supply power to the vehicle's electrical equipment.

[0035] For the mobile power bank mode, as shown in Figure 4(a), the system specifically includes: internal battery E1, internal battery E2, external battery E3 (such as a starting battery in a vehicle), supporting capacitor C1, and three bridge arms composed of upper power switches Q1, Q2, Q3 and lower power switches Q4, Q5, Q6 respectively. Internal battery E1, internal battery E2, and external battery E3 are each connected to the other end of any external inductor. Figure 4(a) shows one specific connection method: internal battery E1 is connected to inductor L1, internal battery E2 is connected to inductor L2, and external battery E3 is connected to inductor L3, with the supporting capacitor connected to the positive and negative terminals of the busbar respectively.

[0036] The optional workflow for power bank mode is as follows: Figure 1As shown, the process includes: First, determining whether internal battery heating is needed based on its temperature and state of charge. If internal battery heating is not required, then determining whether external battery heating is needed based on its temperature and state of charge. If external battery heating is not required, then the internal battery charges the external battery. If the internal battery temperature is too low, internal batteries E1 and E2 first perform AC heating through mutual charging and discharging until the temperature is suitable for AC heating or charging of the external battery. If the external battery temperature is too low, internal batteries E1 and E2 are connected in parallel to perform AC heating of the external battery E3 through mutual charging and discharging until the temperature is suitable for charging or cold start discharge. When the external battery E3 reaches a suitable temperature, if charging is required, internal batteries E1 and E2 are connected in parallel to charge it until the required starting power is reached; otherwise, the connection is disconnected.

[0037] For the fixed mobile power supply mode, as shown in Figure 5(a), the system specifically includes: a 220V AC power supply U3, an AC / DC module U2, a supporting capacitor C1, three bridge arms consisting of upper power switches Q1, Q2, Q3 and lower power switches Q4, Q5, Q6 respectively, and a battery E4 to be charged. The 220V AC power supply U3 is connected to the AC input terminal of the AC / DC module U2, and the DC output terminal of the AC / DC module U2 is connected to the positive and negative terminals P41 and P42 of the DC bus respectively. The battery E4 to be charged is connected to any one of the ports P12, P22, and P32 of the fast cold start system.

[0038] Selectable workflows for fixed power supply mode include: Figure 1 As shown, the process includes: first, determining whether heating is needed based on the temperature and state of charge of the battery being charged. If heating is not needed, charging is performed directly; otherwise, AC heating is applied to the battery until it is fully charged.

[0039] The method of the present invention provides corresponding control strategies for three working modes, as shown in Figures 3(b), 4(b), and 5(b), including: optimal AC heating current strategy, charging strategy, calculation of instantaneous sinusoidal current value, current closed-loop control, PWM pulse width modulation, and bridge arm allocation control (only effective in mobile power supply mode).

[0040] For both internal and external batteries, it is preferable to use a sinusoidal current to heat the battery being heated.

[0041] In the above control strategy, the optimal AC heating current frequency and amplitude I can be calculated in real time by utilizing the collected temperature and state of charge of the heated battery. Amp The optimal AC heating current is one that maximizes the heating rate of the starting battery while minimizing power consumption and damage. The heat generation rate Q is calculated as follows:

[0042]

[0043] In the formula, R re The real part of the battery impedance, which varies with battery temperature T and current frequency f, can be obtained through offline electrochemical impedance spectroscopy.

[0044] The maximum safe operating value for the AC heating current amplitude can be set as follows:

[0045]

[0046] In the formula, U oc U is the open-loop voltage of the battery at the current temperature and state of charge; max U represents the maximum permissible terminal voltage of the battery in its current state. min This represents the minimum permissible terminal voltage of the battery in its current state.

[0047] In the vehicle power mode, the method of this invention can simultaneously perform the functions of AC heating and conventional starting and generating units. It utilizes the three-phase windings and neutral line of the motor to form an AC circuit, therefore, control to eliminate stall torque is necessary. Depending on the motor rotor position, parameters including but not limited to I can be provided. q =0 reference current.

[0048] Closed-loop feedback controls the actual current, and the reference regulating voltage can be obtained by means of PID control, fuzzy control, etc.

[0049] PWM pulse width modulation converts the reference phase voltage into a control signal for the power switching transistor. Specific modulation methods can be selected, including but not limited to SPWM.

[0050] It should be understood that the sequence number of each step in the embodiments of the present invention does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A battery heating control method suitable for rapid cold start in extremely cold environments, characterized in that: The corresponding controls are executed for the three working modes: vehicle power supply, mobile power supply, and stationary power supply. First, a control system including the following modules is constructed: internal battery E1, internal battery E2, 3 sets of bridge arms, supporting capacitor, 3 inductors, DC bus, external battery, and AC / DC module; for any operating mode, 6 power switching transistors are used to form the 3 sets of bridge arms, with each bridge arm consisting of two power switching transistors. The neutral point of each bridge arm serves as the AC side and is connected to one end of an inductor and a current sensor respectively; the two ends of each bridge arm are connected to both sides of the DC bus respectively. For the vehicle-mounted power supply mode, the coil windings of the vehicle's starter generator and the switching elements in the drive module are used as the inductors and bridge arms, and the neutral points of E1 and E2 are connected to the neutral point of the motor through a switch. For the mobile power supply mode and the stationary power supply mode, the vehicle's starter battery is used as the external battery, and it is connected to the control system together with the supporting capacitor. One end of the external battery is connected to the other end of one of the inductors, and the other end of the external battery is connected to the negative line of the DC bus, while the positive line of the DC bus is left floating. The two ends of the supporting capacitor are respectively connected to the two sides of the DC bus. In the mobile power bank mode, the other two ends of the remaining two inductors are connected to the two ends of the internal battery E1 and the internal battery E2 respectively, and the negative ends of the internal batteries E1 and E2 are connected to the non-floating side of the DC bus; in the fixed power bank mode, the remaining two inductors are not connected to the system, and the AC / DC module replaces the internal batteries E1 and E2 to establish a connection with both sides of the DC bus. After the control system is built, the following controls are executed based on PWM modulation for cold start-up in extremely cold environments for each working mode: In the vehicle power mode, the switching of each power switch is controlled to switch the current direction in the system circuit, so that the internal batteries E1 and E2 and each inductor can exchange power to each other and execute the AC heating cycle. When the internal battery temperature and charge meet the starting conditions, the control system operates in inverter mode to drive the starter generator to start the engine. After the engine speed stabilizes, the control system switches to rectification mode to charge the internal battery. In the power bank mode, the system first determines whether heating the internal battery is required. If heating is required, the system controls the switching of power switches to change the current direction in the system circuit, allowing the internal batteries E1 and E2 to exchange power with the inductors, executing an AC heating cycle to reach the predetermined temperature. If heating the internal battery is not required or has already been completed, the system controls the current direction in the system circuit to allow the internal batteries E1 and E2, the inductors, the supporting capacitor, and the external battery to exchange power with each other, executing an AC heating cycle to raise the temperature of the external battery. Once the external battery reaches the predetermined temperature, the system determines whether charging the external battery is required. If so, the system uses the switching of power switches to enable the internal batteries E1 and E2, the corresponding bridge arms, and the inductors to form a DC charging circuit, and then charges the external battery. In the fixed power supply mode, it first determines whether the external battery needs to be heated. If heating is required, it controls the switching of each power switch to select one bridge arm to work, so that the external battery and its connected inductor can mutually transfer power to perform an AC heating cycle. When the external battery reaches the predetermined temperature, it determines whether the external battery needs to be charged. If so, it uses the industrial frequency AC power input through the AC / DC module to charge the external battery.

2. The method as described in claim 1, characterized in that: During the PWM modulation process in the vehicle power mode, the temperature and state of charge of the internal batteries E1 and E2 are collected in real time. The optimal AC heating current amplitude and frequency are calculated. The amplitude and phase error between the reference current and the collected three-phase current of the starter generator are tracked to provide a reference voltage for PWM modulation. By controlling the upper and lower switches of the three bridge arms to be turned on or off synchronously, the amplitude and phase of the current are adjusted, thereby achieving AC heating without motor output torque, so that the internal batteries E1 and E2 are heated to the predetermined temperature.

3. The method as described in claim 1, characterized in that: During the PWM modulation process in the mobile power bank mode, the temperature, voltage, and state of charge of each internal and external battery are collected in real time to calculate the optimal AC heating current amplitude and frequency or the voltage and current during the charging process. The calculation results and the current errors of the internal and external batteries collected in real time are tracked to perform individual closed-loop control of each bridge arm, thereby completing the heating of the internal battery, the heating of the external battery, and constant current or constant voltage DC charging.

4. The method as described in claim 1, characterized in that: In the fixed power supply mode, the temperature and voltage of each internal and external battery are collected in real time during the PWM modulation process. The optimal AC heating current amplitude and frequency or the voltage and current during AC charging are calculated. The error between the calculation result and the current of the external battery collected in real time is tracked to perform closed-loop control on the selected bridge arm, thereby completing the heating or AC charging of the external battery.

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