A heating control method and device of a power battery heater

Abstract

The application relates to the field of battery heating control, and discloses a heating control method and device of a power battery heater, which are applied to a system comprising a single-stage OBC, a high-voltage bus, a PTC heater, a bidirectional DCDC converter and a vehicle-mounted low-voltage storage battery; the method comprises the following steps: S1, collecting a real-time output voltage VHV output by the single-stage OBC in real time; S2, presetting a first voltage threshold V1 and a second voltage threshold V2, and the first voltage threshold V1 is greater than the second voltage threshold V2; S3, comparing the output voltage VHV with the first voltage threshold V1 and the second voltage threshold V2, determining a voltage interval in which the output voltage VHV is located, and adaptively and cooperatively controlling the output power of the single-stage OBC and the working mode and power flow direction of the bidirectional DCDC converter according to the voltage interval. The application can inhibit the influence of the single-stage OBC pulsating output on the bus voltage and maintain the heating stability of the PTC heater.

Description

Technical Field

[0001] This application relates to the field of battery heating control, and in particular to a heating control method and apparatus for a power battery heater. Background Technology

[0002] With the increasing popularity of new energy vehicles, low-temperature heating technology for power batteries is becoming increasingly important. In low-temperature environments, the activity and charge / discharge performance of power batteries decrease significantly. Therefore, vehicles are usually equipped with PTC (Positive Temperature Coefficient) heaters to preheat the power batteries.

[0003] Currently, when vehicles are plugged in for charging and the battery is at a low temperature requiring preheating, the on-board charger (OBC) typically draws power from the mains to supply power to the PTC heater on the high-voltage bus. To reduce costs, decrease size, and improve charging efficiency, some vehicle models are beginning to use single-stage OBCs instead of the traditional two-stage OBCs (which include a PFC stage and a DC / DC stage). However, because single-stage OBCs omit the PFC (Power Factor Correction) stage, their output DC voltage exhibits significant low-frequency ripple (typically 100Hz / 120Hz).

[0004] Under normal charging conditions, since the power battery is directly connected in parallel to the high-voltage bus, the huge capacitance effect inside the power battery can act as a natural "voltage stabilizer," absorbing the pulsating current of the single-stage OBC and maintaining the stability of the bus voltage. However, under dedicated PTC heating conditions, for battery protection strategies (to prevent damage during low-temperature charging), the BMS (Battery Management System) usually controls the high-voltage contactor to disconnect, physically isolating the power battery from the high-voltage bus. At this time, only the PTC heater and the high-voltage side of the DC-DC converter are connected in parallel on the high-voltage bus, losing the voltage stabilization support of the large capacitance of the power battery.

[0005] Regarding the aforementioned technologies, under PTC heating conditions where the power battery is disconnected, the pulsating output of a single-stage OBC causes severe fluctuations in the high-voltage bus voltage. At the peak of the pulsation, excess power has nowhere to be absorbed, easily leading to a surge in bus voltage and even triggering system overvoltage protection shutdown. At the trough of the pulsation, insufficient output power causes a sudden drop in bus voltage, resulting in undervoltage shutdown or frequent start-stop of the PTC heater. This not only seriously affects the stability and efficiency of battery preheating but may even damage high-voltage components. However, increasing the capacity of the bus voltage regulator capacitor to smooth out the fluctuations presents problems of high cost, large size, and difficulty in placing it within the vehicle's interior space. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a heating control method and apparatus for a power battery heater.

[0007] Firstly, the heating control method for a power battery heater provided in this application adopts the following technical solution: A heating control method for a power battery heater is applied to a system including a single-stage OBC, a high-voltage bus, a PTC heater, a bidirectional DC-DC converter, and an on-board low-voltage battery. The output terminal of the single-stage OBC is connected to the high-voltage bus. The high-voltage side of the PTC heater and the bidirectional DC-DC converter are both connected in parallel to the high-voltage bus. The low-voltage side of the bidirectional DC-DC converter is connected to the on-board low-voltage battery. Under the condition that the power battery is disconnected from the high-voltage bus and the PTC heater is used for low-temperature preheating of the power battery, the method includes the following steps: S1, real-time acquisition of the output of the single-stage OBC... S2. Real-time output voltage VHV; S3. Preset a first voltage threshold V1 and a second voltage threshold V2, wherein the first voltage threshold V1 is greater than the second voltage threshold V2; S4. Compare the output voltage VHV with the first voltage threshold V1 and the second voltage threshold V2 to determine the voltage range in which the output voltage VHV is located. Based on the voltage range, adaptively and collaboratively control the output power of the single-stage OBC and the working mode and power flow of the bidirectional DC-DC converter to suppress the influence of the pulsating output of the single-stage OBC on the bus voltage and maintain the heating stability of the PTC heater.

[0008] By adopting the above technical solution, the output voltage pulsation problem caused by the lack of a PFC stage in a single-stage OBC, and the lack of a large capacitor for voltage regulation on the bus due to the disconnection of the power battery under PTC heating conditions, are addressed. The output voltage VHV of the OBC is collected in real time and divided into intervals. The bidirectional DC-DC converter is activated from the traditional unidirectional power supply mode to a bidirectional collaborative regulation mode. According to the interval where the voltage pulsation occurs, the output power of the OBC and the power flow direction of the DC-DC converter are adaptively adjusted. The DC-DC converter absorbs or supplements electrical energy on the high-voltage side, suppressing the impact of the pulsating output of the single-stage OBC on the high-voltage bus voltage, and ensuring the stable operation of the PTC heater under the condition of no parallel connection of the power battery.

[0009] Optionally, according to the voltage range, the adaptive cooperative control includes the following steps: when the output voltage VHV ≥ the first voltage threshold V1, it is determined that the bus heating power is excessive, and the bidirectional DC-DC converter is controlled to transfer the excess power of the high-voltage bus to the vehicle low-voltage battery for storage, while the single-stage OBC is controlled to enter the power reduction mode to suppress the continuous rise of the bus voltage.

[0010] By adopting the above technical solution, in response to the situation where the bus voltage is too high (peak) due to the pulsating output of the OBC, the excess energy is transferred to the low-voltage battery through the positive output of the DC-DC converter to achieve energy recovery. At the same time, the OBC is linked to reduce power to reduce energy input from the source, forming a dual suppression mechanism to prevent the bus from shutting down due to overvoltage.

[0011] Optionally, the voltage output of the single-stage OBC is continuously monitored. When the output voltage VHV falls below the first voltage threshold V1, the single-stage OBC is controlled to exit the power reduction mode and restore the reference output power corresponding to the PTC heating requirement.

[0012] By adopting the above technical solution, the OBC reference power can be restored in a timely manner when the voltage drops, thus ensuring heating efficiency.

[0013] Optionally, according to the voltage range, the adaptive cooperative control further includes the following steps: when the second voltage threshold V2 < the output voltage VHV < the first voltage threshold V1, determine the bus power balance, control the bidirectional DC-DC converter to maintain the current working state of transmitting electrical energy from the high-voltage side to the low-voltage side, and control the single-stage OBC to output a constant reference power according to the heating requirements of the PTC heater.

[0014] By adopting the above technical solution, when the bus voltage is within the normal operating range between the two thresholds, the power supply and demand of the high-voltage bus achieve dynamic balance, eliminating the need for switching the operating mode of the bidirectional DC-DC converter or adjusting the power of the single-stage OBC. This allows the bidirectional DC-DC converter to stably maintain a positive high-to-low voltage power transmission state, ensuring stable heating of the PTC heater while replenishing the vehicle's low-voltage battery. At the same time, the single-stage OBC maintains a constant output reference power, avoiding current fluctuations and device switching losses caused by frequent power adjustments, maintaining steady-state system operation, and improving the stability of the PTC preheating process and the overall high-voltage power distribution efficiency of the vehicle.

[0015] Optionally, according to the voltage range, the adaptive cooperative control further includes the steps of: when the output voltage VHV ≤ the second voltage threshold V2, determining that the output power of the single-stage OBC is insufficient to maintain the operation of the PTC heater; controlling the bidirectional DC-DC converter to switch to the reverse working mode, transmitting the power of the vehicle low-voltage battery to the high-voltage bus, and jointly powering the PTC heater with the single-stage OBC.

[0016] By adopting the above technical solution, in the case of low bus voltage (valley) caused by OBC pulsating output, the energy of the low-voltage battery is pumped into the high-voltage bus by using DC-DC reverse boost to make up for the PTC power gap and prevent the PTC from shutting down or interrupting heating due to undervoltage.

[0017] Optionally, the voltage output of the single-stage OBC is continuously monitored. When the output voltage VHV rises above the second voltage threshold V2, the bidirectional DC-DC converter is controlled to gradually exit the reverse working mode and return to the forward working state where the high-voltage bus transmits electrical energy to the vehicle low-voltage battery.

[0018] By adopting the above technical solution, the system gradually exits the reverse mode after the voltage recovers, preventing current surges caused by instantaneous switching and ensuring a smooth system transition.

[0019] Optionally, when the operating states corresponding to different voltage ranges switch between each other, voltage matching and current limiting soft-start control logic is executed to suppress the current surge caused by the switching of operating conditions.

[0020] By adopting the above technical solution, when the DC-DC working mode is switched (such as from forward to reverse) and the OBC power changes suddenly, the current change rate is limited by the soft-start logic, which can prevent the huge current surge caused by transient switching, protect the power devices, and improve the electrical reliability of the system.

[0021] Optionally, a voltage-stabilizing capacitor is connected in parallel on the high-voltage bus. The voltage-stabilizing capacitor, in conjunction with the dynamic adjustment of the bidirectional DC-DC converter, performs peak shaving and valley filling on the pulsating output power of the single-stage OBC.

[0022] By adopting the above technical solution, a voltage-stabilizing capacitor is introduced as a passive buffer, which works in conjunction with the active dynamic adjustment of the DC-DC converter. The capacitor absorbs high-frequency spikes, and the DC-DC converter processes low-frequency pulsations, forming a "active + passive" synergistic peak-shaving and valley-filling mechanism, further reducing the instantaneous power burden of the DC-DC converter.

[0023] Secondly, the heating control device for a power battery heater provided in this application adopts the following technical solution: A heating control device for a power battery heater includes: a single-stage OBC with its output end connected to a high-voltage bus; a bidirectional DC-DC converter with its high-voltage side connected in parallel to the high-voltage bus and its low-voltage side connected to an on-board low-voltage battery; a PTC heater connected in parallel to the high-voltage bus for low-temperature preheating of the automotive power battery; and a controller including: a voltage sampling module for real-time acquisition of the real-time output voltage VHV of the single-stage OBC; an interval comparison module for interval comparison of the output voltage VHV with a preset first voltage threshold V1 and a second voltage threshold V2; and a mode control module for outputting control signals to the single-stage OBC and the bidirectional DC-DC converter based on the comparison results, adaptively and collaboratively controlling the output power of the single-stage OBC and the operating mode and power flow of the bidirectional DC-DC converter.

[0024] By adopting the above technical solution, this device addresses the output voltage pulsation problem caused by the lack of a PFC stage in single-stage OBCs and the deficiency of a lack of large capacitor voltage regulation on the high-voltage bus due to the disconnection of the power battery under PTC heating conditions. Through the collaborative design of the controller, this device activates the bidirectional DC-DC converter from the traditional unidirectional power supply mode into a bidirectional power regulation channel. The voltage sampling module and the interval comparison module work together to accurately identify the pulsation state of the OBC output. The mode control module adaptively adjusts the output power of the OBC accordingly and changes the power flow direction of the bidirectional DC-DC converter. It uses the vehicle's low-voltage battery as an energy buffer to absorb or supplement electrical energy on the high-voltage side. Thus, without adding additional large-capacity voltage regulation hardware, it suppresses the impact of single-stage OBC pulsation output on the high-voltage bus voltage and ensures the stable operation of the PTC heater under conditions without parallel connection of the power battery.

[0025] Optionally, it also includes an AC-EMI filter, an HV-EMI filter, and a voltage stabilizing capacitor; the AC-EMI filter is disposed between the mains power and the input terminal of the single-stage OBC, the HV-EMI filter is disposed between the output terminal of the single-stage OBC and the high-voltage bus, the voltage stabilizing capacitor is connected in parallel to the high-voltage bus, and the sampling point of the voltage sampling module is disposed between the output terminal of the single-stage OBC and the HV-EMI filter.

[0026] By adopting the above technical solution, the EMC design and voltage regulation design are improved in terms of hardware topology. Furthermore, by setting the voltage sampling point before the HV-EMI filter (at the OBC output end), the pulsating output state of the OBC can be reflected most realistically and with low delay. This reduces the smoothing delay effect of the HV-EMI filter on voltage feedback and improves the response speed and accuracy of the control system.

[0027] In summary, this application includes at least one of the following beneficial technical effects: 1. By real-time acquisition of OBC output voltage and comparison with dual thresholds, adaptive and coordinated control of OBC output power and bidirectional DC-DC working mode and power flow direction is achieved, overcoming the pulsating output defect of single-stage OBC under the condition of no parallel power battery, suppressing the violent fluctuation of bus voltage, and maintaining the stable operation of PTC heater. 2. By using a bidirectional DC-DC converter to recover excess energy to the low-voltage battery when the bus voltage is too high and to replenish energy in the reverse direction when the bus voltage is too low, peak shaving and valley filling of pulsating power and comprehensive energy utilization are achieved, preventing PTC shutdown due to undervoltage or system overvoltage protection. 3. By introducing voltage matching and current-limiting soft-start logic during operating condition switching, combined with passive filtering of the high-voltage bus voltage stabilizing capacitor, smooth coordinated regulation of "active + passive" is achieved, suppressing the current surge during mode switching and improving the electrical safety of the system. The voltage sampling point is set between the OBC output terminal and the HV-EMI filter in the device, eliminating the delay and smoothing effect of the filtering stage on the sampling signal, ensuring that the controller can accurately capture the original pulsation state of the OBC, and improving the speed and accuracy of closed-loop control. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the PTC heating system structure of a power battery based on a single-stage OBC provided in an embodiment of this application; Figure 2 This is a structural block diagram of the PTC heating system for a power battery based on a single-stage OBC, provided in an embodiment of this application, regarding the controller. Figure 3 This is a flowchart of the heating control method for a power battery heater provided in an embodiment of this application; Figure 4 This is a working condition switching logic diagram of the heating control method for the power battery heater provided in the embodiments of this application; Figure 5 This is a closed-loop logic flowchart of the heating control method for a power battery heater provided in the embodiments of this application.

[0029] Explanation of reference numerals in the attached figures: 10. Single-stage OBC; 20. Bidirectional DC-DC converter; 30. Vehicle low-voltage battery; 40. High-voltage bus; 50. PTC heater; 60. Automotive power battery; 70. Voltage stabilizing capacitor; 80. AC-EMI filter; 90. HV-EMI filter; 100. Controller. Detailed Implementation

[0030] The following is in conjunction with the appendix Figure 1-5 This application will be described in further detail.

[0031] Before describing the technical solution of this application in detail, a brief explanation of the technical background involved in this application will be given first.

[0032] In the field of new energy vehicles, the activity of power batteries decreases significantly in low-temperature environments, and their charge and discharge performance degrades severely. Therefore, vehicles are usually equipped with PTC heaters to preheat the power batteries before plugging in for charging. Under these conditions, the on-board charger (OBC) draws power from the mains and supplies power to the PTC heater through the high-voltage bus. To reduce costs, decrease size, and improve charging efficiency, some models use a single-stage OBC instead of the traditional two-stage OBC (which includes a PFC stage and a DC / DC stage). However, because the single-stage OBC omits the PFC (Power Factor Correction) stage, its output DC voltage exhibits significant low-frequency pulsations (typically 100Hz or 120Hz).

[0033] Under normal charging conditions, the power battery is directly connected in parallel to the high-voltage bus. The huge equivalent capacitance inside the power battery (typically reaching hundreds of farads) can act as a natural "voltage stabilizer," absorbing the pulsating current of the single-stage OBC and maintaining the bus voltage relatively stable. However, under dedicated PTC heating conditions, for battery protection strategies (to prevent lithium dendrite precipitation and battery damage due to low-temperature charging), the BMS (Battery Management System) usually controls the high-voltage contactor to disconnect, physically isolating the power battery from the high-voltage bus. At this time, the high-voltage bus only has the PTC heater, the high-voltage side of the DC-DC converter, and a limited-capacity voltage stabilizing capacitor connected in parallel, losing the large-capacity voltage stabilizing support of the power battery. Under these conditions, the pulsating output of the single-stage OBC will cause severe fluctuations in the high-voltage bus voltage: at the peak of the pulsation, excess power has nowhere to be absorbed, the bus voltage spikes, and it is easy to trigger the system overvoltage protection shutdown; at the trough of the pulsation, the output power is insufficient, the bus voltage drops sharply, causing the PTC heater to shut down due to undervoltage or frequently start and stop.

[0034] This application addresses the aforementioned technical problems by providing a heating control method and apparatus for a power battery heater.

[0035] This application first discloses a heating control device for a power battery heater. (Refer to...) Figure 1 , Figure 1 The power topology of a power battery PTC heating system based on a single-stage OBC is shown. The heating control device includes a single-stage OBC 10, a bidirectional DC-DC converter 20, an on-board low-voltage battery 30, a high-voltage bus 40, a PTC heater 50, an AC-EMI filter 80, an HV-EMI filter 90, and a controller 100. The high-voltage bus 40 is the high-voltage power distribution link for the entire vehicle, with a rated operating voltage range of 300V to 450V. The on-board low-voltage battery 30 is a 9V to 12V low-voltage power supply battery for the entire vehicle, mainly used to provide operating power and constant power to the vehicle's low-voltage electrical equipment such as lights, instruments, body controllers, and electronic control modules.

[0036] Reference Figure 1 The input of the single-stage OBC 10 is connected to AC power via an AC-EMI filter 80 to obtain AC power from the AC power supply and convert it into DC high-voltage output. The output of the single-stage OBC 10 is connected to the high-voltage bus 40. An HV-EMI filter 90 is installed between the output of the single-stage OBC 10 and the high-voltage bus 40 to suppress the conduction of high-frequency electromagnetic interference from the output of the single-stage OBC 10 to the high-voltage bus 40.

[0037] The PTC heater 50 is connected in parallel to the high-voltage bus 40 to preheat the automotive power battery 60 at low temperatures. The PTC heater 50 obtains electrical energy from the high-voltage bus 40 and converts it into heat energy to heat the power battery pack.

[0038] The high-voltage side of the bidirectional DC-DC converter 20 is connected in parallel to the high-voltage bus 40, and the low-voltage side is connected to the vehicle's low-voltage battery 30. The bidirectional DC-DC converter 20 can realize bidirectional power transfer between the high-voltage and low-voltage sides: in forward operating mode, it steps down the power from the high-voltage bus 40 and transfers it to the vehicle's low-voltage battery 30 for storage; in reverse operating mode, it steps up the power from the vehicle's low-voltage battery 30 and transfers it to the high-voltage bus 40.

[0039] The power battery module is connected to the high-voltage bus 40 via a high-voltage contactor (shown as a dashed box in the diagram). Under PTC heating conditions, the BMS controls the high-voltage contactor to disconnect, physically isolating the vehicle's power battery 60 from the high-voltage bus 40.

[0040] In one embodiment, a voltage stabilizing capacitor 70 (labeled C in the figure) is connected in parallel to the high-voltage bus 40. The voltage stabilizing capacitor 70 is used to perform preliminary passive filtering and buffering of voltage fluctuations on the high-voltage bus 40, absorbing high-frequency spike components.

[0041] Understandably, the AC-EMI filter 80 is positioned between the mains power supply and the input of the single-stage OBC 10 to suppress electromagnetic interference from the mains side entering the OBC and to prevent harmonic currents generated by the OBC from flowing back into the power grid. The HV-EMI filter 90 is positioned between the output of the single-stage OBC 10 and the high-voltage bus 40 to suppress the transmission of high-frequency switching ripple from the OBC output to the high-voltage bus. The voltage regulator 70 works in conjunction with the dynamic adjustment of the bidirectional DC-DC converter 20 to smooth and fill the pulsating output power of the single-stage OBC 10, forming an active + passive synergistic regulation mechanism: the voltage regulator 70 absorbs high-frequency spikes, while the bidirectional DC-DC converter 20 handles low-frequency pulsations; the two complement each other, reducing the instantaneous power load of the DC-DC converter.

[0042] Reference Figure 2 , Figure 2A block diagram of the controller 100 is shown. The controller 100 includes a voltage sampling module, an interval comparison module, and a mode control module.

[0043] The voltage sampling module is used to acquire the real-time output voltage VHV of the single-stage OBC 10.

[0044] It should be noted that, in a preferred embodiment, the sampling point of the voltage sampling module is located between the output terminal of the single-stage OBC 10 and the HV-EMI filter 90, that is, sampling is performed before the high-voltage DC voltage passes through the HV-EMI filter 90. The purpose of this arrangement is that the HV-EMI filter 90 smooths and delays the signal; if sampling occurs after the filter, the pulsation characteristics in the sampled signal will be partially attenuated and delayed, making it difficult for the controller to capture the true pulsation state of the OBC output in a timely manner. Setting the sampling point before the filter allows for the most accurate and low-latency reflection of the original pulsation output state of the OBC, improving the response speed and accuracy of the closed-loop control. In another embodiment, the sampling point of the voltage sampling module can also be located on the high-voltage bus 40 side downstream of the HV-EMI filter 90, which also achieves the voltage sampling and closed-loop control functions of this application.

[0045] The interval comparison module is used to compare the output voltage VHV with a preset first voltage threshold V1 and a second voltage threshold V2 to determine the voltage interval in which the output voltage VHV is located. Among them, the first voltage threshold V1 is greater than the second voltage threshold V2.

[0046] The mode control module is used to output control signals to the single-stage OBC 10 and the bidirectional DC-DC converter 20 based on the comparison results of the interval comparison module, and adaptively and collaboratively control the output power of the single-stage OBC 10 and the operating mode and power flow of the bidirectional DC-DC converter 20.

[0047] In one embodiment, the specific values ​​of the first voltage threshold V1 and the second voltage threshold V2 are determined based on the rated operating voltage range of the PTC heater 50, the system overvoltage protection threshold, and the rated output voltage of the single-stage OBC 10. For example, when the rated operating voltage of the PTC heater 50 is 400V and the system overvoltage protection threshold is 450V, the first voltage threshold V1 can be set to 420V and the second voltage threshold V2 can be set to 380V, so that the interval between V1 and V2 covers the normal operating voltage range of the PTC heater 50.

[0048] This application also discloses a heating control method for a power battery heater, applied to the aforementioned heating control device. (Refer to...) Figure 3 , Figure 3 A flowchart of the heating control method is shown. The method includes the following steps: Step S1: Real-time acquisition of the real-time output voltage VHV of the single-stage OBC 10.

[0049] Specifically, the voltage sampling module of controller 100 acquires the DC output voltage VHV in real time at the sampling point between the output of the single-stage OBC 10 and the HV-EMI filter 90. The sampling frequency should be higher than the frequency of the output pulsation of the single-stage OBC 10 (100Hz or 120Hz) to ensure accurate capture of the peak and valley values ​​of the pulsation waveform. In one embodiment, preferably, the sampling frequency is set to 1kHz to 10kHz.

[0050] Step S2: Preset a first voltage threshold V1 and a second voltage threshold V2, wherein the first voltage threshold V1 is greater than the second voltage threshold V2.

[0051] The first voltage threshold V1 is the upper limit threshold for determining the bus voltage. When the output voltage VHV exceeds V1, it indicates that the OBC pulsating output is at its peak, and the power supply on the bus is greater than the consumption of the PTC heater 50 and the bidirectional DC-DC converter 20, posing an overvoltage risk. The second voltage threshold V2 is the lower limit threshold for determining the bus voltage. When the output voltage VHV is lower than V2, it indicates that the OBC pulsating output is at its trough, and the power supply on the bus is insufficient to maintain the normal operation of the PTC heater 50, posing an undervoltage risk. The interval between V1 and V2 is the normal operating range of the bus voltage, and the system is in a power balance state.

[0052] Step S3: Compare the output voltage VHV with the first voltage threshold V1 and the second voltage threshold V2 to determine the voltage range in which the output voltage VHV is located. Based on the voltage range, adaptively and collaboratively control the output power of the single-stage OBC 10 and the working mode and power flow of the bidirectional DC-DC converter 20 to suppress the influence of the pulsating output of the single-stage OBC 10 on the bus voltage and maintain the heating stability of the PTC heater 50.

[0053] Reference Figure 4 , Figure 4 The diagram illustrates the operating condition switching logic of the heating control method, showing the operating states corresponding to the three voltage ranges and the conditions for their switching. The adaptive cooperative control strategies corresponding to each of the three voltage ranges are explained in detail below.

[0054] Step S31: When the output voltage VHV ≥ the first voltage threshold V1, it is determined that the bus heating power is sufficient.

[0055] At this time, the pulsating output of the single-stage OBC 10 is at its peak, and the output power exceeds the power consumption of the PTC heater 50. If the excess electrical energy is not absorbed in time, it will cause the bus voltage to continue to rise, triggering the system overvoltage protection.

[0056] The mode control module of controller 100 performs two control actions simultaneously: First, the bidirectional DC-DC converter 20 is controlled to operate in forward mode, meaning that excess electrical energy on the high-voltage bus 40 is transferred from the high-voltage side to the low-voltage side via the bidirectional DC-DC converter 20 to charge and store the on-board low-voltage battery 30. Under this condition, the on-board low-voltage battery 30 acts as an energy buffer, absorbing excess power during OBC peaks. The forward output power of the bidirectional DC-DC converter 20 can be proportionally adjusted according to the extent to which VHV exceeds V1: the greater the exceedance of VHV by V1, the greater the forward output power of the DC-DC converter, thus accelerating the absorption of excess energy.

[0057] Second, the single-stage OBC 10 is controlled to enter a power reduction mode, reducing the output power of the OBC. This reduces the power input to the high-voltage bus 40 from the energy source, forming a dual suppression mechanism with the energy transfer from the DC-DC converter, and working together to prevent the bus voltage from continuously rising.

[0058] Furthermore, during the power reduction mode, the controller 100 continuously monitors the output voltage VHV. When VHV falls below the first voltage threshold V1, it indicates that the excess power on the bus has been eliminated. The controller 100 then controls the single-stage OBC 10 to exit the power reduction mode and restore the output power to the reference output power corresponding to the PTC heating demand (the reference output power is the constant output power calibrated by the single-stage OBC 10 under rated operating conditions of the PTC heater 50 and the mains input, providing rated power support for the normal preheating of the PTC heater), ensuring that the heating efficiency is not affected in the long term. (Refer to...) Figure 4 This response path corresponds to the switching logic from the "DC-CDC forward operation / OBC reduce output power" state to the "DC-CDC forward operation / OBC normal forward operation" state via "OBC stops reducing power".

[0059] Step S32: When the second voltage threshold V2 < output voltage VHV < first voltage threshold V1, determine that the bus power is balanced.

[0060] At this time, the output voltage of the single-stage OBC 10 is in the normal operating range between V1 and V2, the power supply on the bus is basically balanced with the consumption of the PTC heater 50, and the system is working in an ideal state.

[0061] Controller 100 controls the bidirectional DC-DC converter 20 to maintain its current positive operating state of transferring electrical energy from the high-voltage side to the low-voltage side (powering the on-board low-voltage battery 30), and controls the single-stage OBC 10 to output a constant reference power according to the PTC heating demand. Within this range, the system does not perform any active power regulation intervention, relying solely on the voltage regulator capacitor 70 to passively absorb residual small fluctuations. (Refer to...) Figure 4This state is the central steady state of the operating condition switching logic, namely the "DCDC forward operation / OBC normal forward operation" state.

[0062] Step S33: When the output voltage VHV ≤ the second voltage threshold V2, it is determined that the output power of the single-stage OBC 10 is insufficient to maintain the operation of the PTC heater 50.

[0063] At this time, the pulsating output of the single-stage OBC 10 is in a trough, and the output power is lower than the power required by the PTC heater 50. If no compensation is made, the bus voltage will continue to drop, causing the PTC heater 50 to shut down or reduce its power due to undervoltage, which will affect the battery preheating effect.

[0064] The controller 100 controls the bidirectional DC-DC converter 20 to switch to reverse operating mode, boosting the electrical energy from the low-voltage side of the vehicle's low-voltage battery 30 and transmitting it to the high-voltage bus 40, where it, together with the single-stage OBC 10, supplies power to the PTC heater 50. At this time, the vehicle's low-voltage battery 30 releases the energy stored in step S31 (as well as its original electrical energy), which is then boosted in reverse by the bidirectional DC-DC converter 20 and injected into the high-voltage bus 40 to compensate for the power gap during OBC troughs, maintaining the stability of the bus voltage and PTC heating power.

[0065] Furthermore, the controller 100 continuously monitors the output voltage VHV. When VHV rises above the second voltage threshold V2, it indicates that the OBC's output power has recovered to a level sufficient to maintain the normal operation of the PTC. The controller 100 then controls the bidirectional DC-DC converter 20 to gradually exit the reverse operating mode and return to the forward operating state, where power is transferred from the high-voltage bus 40 to the on-board low-voltage battery 30. (Refer to...) Figure 4 This response path corresponds to the switching logic from the "DCDC reverse operation / OBC normal forward operation" state to the "DCDC forward operation / OBC normal forward operation" state via "DCDC exit reverse operation".

[0066] It should be noted that steps S31, S32, and S33 are not executed in a strictly fixed order, but rather dynamically switch according to the range of the real-time acquired output voltage VHV. Within one pulse cycle of the single-stage OBC 10 (approximately 10ms or 8.3ms), the output voltage VHV may sequentially undergo a change from trough to peak and back to trough. The controller 100 determines the current voltage range in real time within each sampling cycle and executes the corresponding control strategy, forming a continuous closed-loop regulation.

[0067] Reference Figure 4, The operating condition switching logic diagram fully shows all the switching paths between the three working states and their triggering conditions. The central state is "DCDC forward operation / OBC normal forward operation" (V2 < VHV < V1). When VHV rises above V1, it switches to the "DCDC forward operation / OBC reduced output power" state on the left. When VHV drops below V2, it switches to the "DCDC reverse operation / OBC normal forward operation" state on the right. Clear voltage threshold triggering conditions are set for the switching between each state, and a recovery path to return to the central steady state is set for each non-steady state.

[0068] Refer to Figure 5 As shown, the following is the complete closed-loop logic execution process of the heating control method of this application. The specific closed-loop control logic steps are as follows: First, after the system starts, it enters a continuous sampling loop, and continuously samples the real-time output voltage VHV output by the single-stage OBC (10). In the first step, it is determined whether the real-time output voltage VHV is greater than the first voltage threshold V1: If it is determined that VHV ≥ V1, the control system enters the DCDC forward working state and at the same time the OBC operates with reduced power, and continuously monitors the bus voltage VHV; when it is detected that VHV drops below V1, control the OBC to exit the reduced power mode, return to the normal reference output, and return to the main loop sampling; If it is determined that VHV < V1, it is further determined whether the real-time output voltage VHV is greater than the second voltage threshold V2: When VHV > V2, it is determined that the bus power is in the normal balance range, maintain the DCDC forward operation and the OBC normal constant power output, and continuously loop and sample for monitoring; when VHV ≤ V2, it is determined that the bus voltage falls into the trough undervoltage range, control the bidirectional DCDC converter (20) to switch to the reverse energy supplement mode, and the OBC keeps running normally; at the same time, continuously monitor the bus voltage. When it is detected that VHV rises above V2, control the bidirectional DCDC converter (20) to gradually exit the reverse energy supplement mode, restore the forward power transmission state from high voltage to low voltage, and return to the voltage sampling closed-loop process again.

[0069] It can be understood that through conditional judgment, branch execution, state maintenance, conditional regression, and closed-loop cycle logic, a complete software control closed-loop architecture is formed to ensure that the system can achieve real-time adaptive collaborative regulation within the full pulsation period of the single-stage OBC.

[0070] In one embodiment, when the working states corresponding to each voltage range are switched to each other, the voltage matching and current-limiting soft start control logic is executed to suppress the current impact generated by the operating condition switching.

[0071] Specifically, taking the bidirectional DCDC converter 20 switching from the forward working mode to the reverse working mode as an example, the soft start control logic includes the following sub-steps: First, after the switching command is issued, the controller 100 does not immediately jump the power command of the bidirectional DC-DC converter 20 from full forward power to full reverse power. Instead, it gradually reduces the forward output power to zero at a preset slope. During this power reduction process, the controller 100 monitors the output current on the high-voltage side of the bidirectional DC-DC converter 20 in real time to ensure that the rate of change of current does not exceed a preset current limiting threshold (e.g., not exceeding 10% of the rated current per millisecond; in engineering applications, a fixed slope threshold can be calibrated according to the voltage and current withstand rating of the power devices).

[0072] Secondly, when the forward output power drops to zero, the controller 100 checks whether the output voltage on the high-voltage side of the bidirectional DC-DC converter 20 matches the current voltage of the high-voltage bus 40. Reverse operation mode is only allowed to start when the voltage difference between the two is within a preset matching window (e.g., the difference is less than 5V). This voltage matching step prevents inrush current from being generated during mode switching due to excessive voltage differences between the high and low voltage sides.

[0073] Finally, after confirming voltage matching, the controller 100 controls the bidirectional DC-DC converter 20 to gradually increase the reverse output power at a preset power ramp rate until the required reverse output power value for the current operating condition is reached. During the power ramp-up process, the output current is continuously monitored. If the current exceeds the current limiting threshold, the power ramp-up is paused until the current drops back down.

[0074] Understandably, the voltage matching and current-limiting soft-start control logic described above is also applicable to other mode-switching scenarios, including: switching back from reverse operating mode to forward operating mode, OBC entering throttling mode from reference power, and OBC returning to reference power from throttling mode. Each time power or mode changes, power ramp control and current limiting are used to suppress transient impacts, protecting the power devices, Zener capacitor 70, and PTC heater 50 in the system, thereby improving the electrical reliability and lifespan of the system.

[0075] It should be noted that the soft-start slope parameter and current limiting threshold can be calibrated based on the actual system's power level, the DC-DC converter's response bandwidth, and the capacitance of the regulated capacitor 70. A smaller slope results in smoother switching but a slower response; a larger slope results in a faster response but a larger current surge. In practical engineering applications, the optimal parameters can be determined through a combination of simulation and experimentation to achieve a balance between switching smoothness and response speed.

[0076] The implementation principle of the heating control method for a power battery heater in this application embodiment is as follows: Under PTC heating conditions, since the vehicle power battery 60 is disconnected from the high-voltage bus 40, the high-voltage bus 40 loses the large capacitor voltage stabilization support of the power battery, and the pulsating output of the single-stage OBC 10 will cause the bus voltage to fluctuate violently. This application collects the voltage VHV at the OBC output terminal in real time through the controller 100 and compares it with the preset first voltage threshold V1 and second voltage threshold V2. According to the voltage range where VHV is located, the output power of the OBC and the working mode of the bidirectional DC-DC converter 20 are adaptively and collaboratively controlled: when VHV≥V1, it indicates that it is at the peak of the pulsation wave, the DC-DC converter operates in the forward direction to absorb excess energy to the vehicle low-voltage battery 30, and at the same time the OBC reduces power, forming a dual voltage suppression mechanism; when V2<VHV<V1, the system is in a power balance state and maintains normal operation; when VHV≤V2, it indicates that it is at the trough of the pulsation wave, the DC-DC converter operates in the reverse direction to pump the energy of the vehicle low-voltage battery 30 into the high-voltage bus 40 to supplement the power gap. Through the above strategy, the bidirectional DC-DC converter 20 is activated from the traditional unidirectional power supply mode to a bidirectional power regulation channel. The on-board low-voltage battery 30 is used as an energy buffer, and together with the voltage stabilizing capacitor 70 on the high-voltage bus 40, a collaborative peak-shaving and valley-filling mechanism of "active dynamic regulation + passive filtering" is formed. Without adding additional large-capacity voltage stabilizing hardware, the impact of the pulsating output of the single-stage OBC on the high-voltage bus voltage is effectively suppressed, ensuring the stable operation of the PTC heater 50 under the condition of no parallel connection of power battery.

[0077] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A heating control method for a power battery heater, characterized in that, It is applied to systems including single-stage OBC (10), high-voltage bus (40), PTC heater (50), bidirectional DC-DC converter (20) and vehicle low-voltage battery (30); The output terminal of the single-stage OBC (10) is connected to the high-voltage bus (40). The high-voltage side of the PTC heater (50) and the bidirectional DC-DC converter (20) are both connected in parallel to the high-voltage bus (40). The low-voltage side of the bidirectional DC-DC converter (20) is connected to the vehicle low-voltage battery (30). Under the condition that the vehicle power battery (60) is disconnected from the high-voltage bus (40) and the PTC heater (50) is used for low-temperature preheating of the vehicle power battery (60), the method includes the following steps: S1. Real-time acquisition of the real-time output voltage VHV of the single-stage OBC (10); S2. A first voltage threshold V1 and a second voltage threshold V2 are preset, and the first voltage threshold V1 is greater than the second voltage threshold V2; S3. The output voltage VHV is compared with the first voltage threshold V1 and the second voltage threshold V2 to determine the voltage range in which the output voltage VHV is located. Based on the voltage range, the output power of the single-stage OBC (10) and the working mode and power flow of the bidirectional DC-DC converter (20) are adaptively and collaboratively controlled to suppress the influence of the pulsating output of the single-stage OBC (10) on the bus voltage and maintain the heating stability of the PTC heater (50).

2. The heating control method for a power battery heater according to claim 1, characterized in that, Based on the voltage range, the adaptive cooperative control includes the following steps: S31. When the output voltage VHV ≥ the first voltage threshold V1, it is determined that the bus heating power is excessive. The bidirectional DC-DC converter (20) is controlled to transfer the excess power of the high voltage bus (40) to the vehicle low voltage battery (30) for storage. At the same time, the single-stage OBC (10) is controlled to enter the power reduction mode to suppress the continuous rise of the bus voltage.

3. The heating control method for the power battery heater according to claim 2, characterized in that, It also includes the following steps: The voltage output of the single-stage OBC (10) is continuously monitored. When the output voltage VHV falls below the first voltage threshold V1, the single-stage OBC (10) is controlled to exit the power reduction mode and restore the reference output power corresponding to the heating requirements of the PTC heater (50).

4. The heating control method for a power battery heater according to claim 1, characterized in that, Based on the voltage range, the adaptive cooperative control further includes the following steps: S32. When the second voltage threshold V2 < the output voltage VHV < the first voltage threshold V1, the bus power balance is determined, the bidirectional DC-DC converter (20) is controlled to maintain the current working state of transmitting electrical energy from the high voltage side to the low voltage side, and the single-stage OBC (10) is controlled to output constant power according to the reference power corresponding to the heating requirements of the PTC heater (50).

5. The heating control method for a power battery heater according to claim 1, characterized in that, Based on the voltage range, the adaptive cooperative control further includes the following steps: S33. When the output voltage VHV ≤ the second voltage threshold V2, it is determined that the output power of the single-stage OBC (10) is insufficient to maintain the operation of the PTC heater (50); the bidirectional DC-DC converter (20) is controlled to switch to the reverse working mode, and the power of the vehicle low-voltage battery (30) is transmitted to the high-voltage bus (40) to supply power to the PTC heater (50) together with the single-stage OBC (10).

6. The heating control method for a power battery heater according to claim 5, characterized in that, It also includes the following steps: The voltage output of the single-stage OBC (10) is continuously monitored. When the output voltage VHV rises above the second voltage threshold V2, the bidirectional DC-DC converter (20) is controlled to gradually exit the reverse working mode and return to the positive working state where the high-voltage bus (40) transmits electrical energy to the vehicle low-voltage battery (30).

7. The heating control method for a power battery heater according to claim 1, characterized in that, When switching between operating states corresponding to different voltage ranges, voltage matching and current limiting soft-start control logic is executed to suppress current surges caused by operating condition switching.

8. The heating control method for a power battery heater according to claim 1, characterized in that, A voltage stabilizing capacitor (70) is connected in parallel on the high-voltage bus (40). The voltage stabilizing capacitor (70) works in conjunction with the dynamic adjustment of the bidirectional DC-DC converter (20) to smooth out the peaks and fill the valleys of the pulsating output power of the single-stage OBC (10).

9. A heating control device for a power battery heater, using the heating control method for a power battery heater as described in any one of claims 1-8, characterized in that, include: A single-stage OBC (10) is connected to a high-voltage bus (40) at its output end. A bidirectional DC-DC converter (20) is connected in parallel to the high-voltage bus (40) on the high-voltage side and connected to the vehicle low-voltage battery (30) on the low-voltage side. A PTC heater (50) is connected in parallel to the high-voltage bus (40) for low-temperature preheating of the automotive power battery (60); The controller (100) includes: a voltage sampling module for real-time acquisition of the real-time output voltage VHV output by the single-stage OBC (10); The interval comparison module is used to compare the output voltage VHV with the preset first voltage threshold V1 and second voltage threshold V2 in the interval; the mode control module is used to output control signals to the single-stage OBC (10) and the bidirectional DC-DC converter (20) according to the comparison results, and adaptively and collaboratively control the output power of the single-stage OBC (10) and the working mode and power flow of the bidirectional DC-DC converter (20).

10. The heating control device for the power battery heater according to claim 9, characterized in that, It also includes an AC-EMI filter (80), an HV-EMI filter (90), and a voltage regulator capacitor (70); the AC-EMI filter (80) is disposed between the mains power and the input terminal of the single-stage OBC (10), the HV-EMI filter (90) is disposed between the output terminal of the single-stage OBC (10) and the high-voltage bus (40), the voltage regulator capacitor (70) is connected in parallel on the high-voltage bus (40), and the sampling point of the voltage sampling module is disposed between the output terminal of the single-stage OBC (10) and the HV-EMI filter (90).

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