Method and system for controlling dc-dc output voltage of a hybrid vehicle

Abstract

The application discloses a DCDC output voltage control method and control system of a hybrid vehicle, and belongs to the technical field of vehicle electronics. The method comprises the following steps: when a DCDC converter is in a step-down working mode, it is judged whether the vehicle is in a high-power output demand state or an engine abnormal shutdown state; if yes, the output voltage of the DCDC converter is set as a normal target voltage, so that the DCDC converter is controlled to output according to the normal target voltage; otherwise, it is judged whether a low-voltage load has a charging voltage boosting demand, and when the low-voltage load has the charging voltage boosting demand and the electric quantity of a high-voltage battery is greater than an electric quantity threshold value, the output voltage of the DCDC converter is set as a voltage level corresponding to the charging voltage boosting demand, so that the charging demand of the low-voltage load is met. The DCDC output voltage control method and control system can optimize the fuel economy of a hybrid power assembly system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vehicle electronics, in particular to a DCDC output voltage control method and control system for a hybrid vehicle. BACKGROUND

[0002] For a hybrid vehicle, the low voltage electrical loads including 12V battery, engine ignition coil, fuel injector, instrument cluster, display screen, all controllers, etc. are powered by a voltage converter DCDC. For a traditional non-hybrid vehicle, the above low voltage loads are powered by an intelligent generator.

[0003] For a traditional vehicle equipped with a conventional generator, the engine drives the generator to generate power at a constant voltage, which is not conducive to improving the economy of the engine. For a traditional vehicle equipped with an intelligent generator, the engine ECU can flexibly adjust the generator voltage according to the operating conditions of the vehicle and the engine, and the state of the battery, so as to flexibly adjust the load of the generator under different conditions, thereby optimizing the fuel economy of the engine.

[0004] For a hybrid vehicle, the conventional generator driven by a belt is usually cancelled, and instead, the hybrid motor is used to generate power to charge the high-voltage battery system, and then the DCDC converts the high-voltage direct current into low-voltage power required by the low-voltage power supply loop. The DCDC can also quickly adjust its output voltage within a certain range. In order to achieve the purpose of optimizing the fuel economy of the hybrid powertrain system, the output voltage needs to be adjusted by a special control strategy. SUMMARY

[0005] In view of the above problems, the present application is proposed to provide a DCDC output voltage control method and control system for a hybrid vehicle, which can overcome the above problems or at least partially solve the above problems.

[0006] One object of the first aspect of the present application is to provide a DCDC output voltage control method for a hybrid vehicle, which can optimize the fuel economy of the hybrid powertrain system.

[0007] Another object of the first aspect of the present application is to ensure the basic operation of the vehicle.

[0008] One object of the second aspect of the present application is to provide a DCDC output voltage control system for implementing the above control method, which can optimize the fuel economy of the hybrid powertrain system.

[0009] In particular, according to a first aspect of an embodiment of the present application, there is provided a DCDC output voltage control method for a hybrid vehicle, the vehicle comprising a DCDC converter for converting and outputting a voltage of a high-voltage battery as a low-voltage voltage for use by a low-voltage load of the vehicle when in a step-down operation mode, the method comprising:

[0010] determining whether the vehicle is in a high-power output demand state or an engine abnormal shutdown state when the DCDC converter is in the step-down operation mode;

[0011] if so, setting an output voltage of the DCDC converter to a normal target voltage to control the DCDC converter to output according to the normal target voltage;

[0012] otherwise, determining whether the low-voltage load has a charging voltage boost demand, and setting the output voltage of the DCDC converter to a voltage level corresponding to the charging voltage boost demand to meet a charging demand of the low-voltage load when the low-voltage load has the charging voltage boost demand and the high-voltage battery has an amount of power greater than an amount of power threshold.

[0013] Optionally, the method further comprises, before the step of determining whether the vehicle is in a high-power output demand state or an engine abnormal shutdown state when the DCDC converter is in the step-down operation mode:

[0014] determining whether the vehicle is in a DCDC enabled state;

[0015] controlling the DCDC converter to prepare for voltage conversion and timing when the vehicle is in the enabled state and receives a step-down request instruction, and controlling the DCDC converter to switch to the step-down operation mode when the timing time reaches a preset delay time.

[0016] Optionally, the step of determining whether the vehicle is in a DCDC enabled state comprises:

[0017] determining that the DCDC converter is in a pre-enabled state when a high-voltage battery of the vehicle is in a power-supplyable state, the vehicle receives a start request instruction, the high-voltage battery is in a state capable of maintaining a preset amount of power, the DCDC converter is in a state capable of normally receiving and transmitting signals, and a high-voltage system is fault-free;

[0018] determining that the DCDC converter is in an enabled state when an ignition signal is received and it is determined that a motor of the vehicle is fault-free when the DCDC converter is in the pre-enabled state.

[0019] Optionally, the high power output demand state includes at least one of a launch state, a full throttle acceleration state, a running large throttle launch state, and a creep launch gear state.

[0020] Optionally, the step of determining whether the vehicle is in a high power output demand state includes:

[0021] The vehicle is determined to be in the launch state when an engine of the vehicle is started for a first time in a same drive cycle for less than a first limit or started for a non-first time for less than a second limit, wherein the first limit is greater than the second limit.

[0022] Optionally, the step of determining whether the vehicle is in a high power output demand state includes:

[0023] The vehicle is determined to be in the full throttle acceleration state when a throttle pedal opening of the vehicle is greater than a first opening limit, the vehicle is in a forward gear or a reverse gear, and a time that the throttle pedal opening is greater than the first opening limit is less than a third limit.

[0024] Optionally, the step of determining whether the vehicle is in a high power output demand state includes:

[0025] The vehicle is determined to be in the running large throttle launch state when an engine of the vehicle is in a running state, a vehicle speed is less than a launch vehicle speed threshold, a reserve torque of the engine is less than a torque threshold, an opening of a throttle pedal of the vehicle is greater than a second opening limit, a difference between a maximum torque of the engine and a requested torque of a driver is less than a difference threshold, and a current air conditioning compressor power is greater than a power limit.

[0026] Optionally, the step of determining whether the vehicle is in a high power output demand state includes:

[0027] The vehicle is determined to be in the creep launch gear state when the engine of the vehicle is in the running state and a start time is less than a fourth limit, the vehicle speed is less than the launch vehicle speed threshold, the reserve torque of the engine is less than the torque threshold, an opening information of the throttle pedal is not received, and the vehicle is in the forward gear or the reverse gear.

[0028] Optionally, the step of determining whether the vehicle is in an engine abnormal stall state includes:

[0029] The vehicle is determined to be in the engine abnormal stall state when the engine of the vehicle is in the running state, a speed of the engine is less than a target idle speed and an absolute value of a difference between the speed of the engine and the target idle speed is greater than a speed difference limit, an acceleration of the speed of the engine is negative and an absolute value of the acceleration of the speed of the engine is less than an acceleration limit, and a predicted speed of the engine is less than a stall speed threshold.

[0030] Optionally, the step of determining whether the low-voltage load has a charging voltage boosting requirement comprises:

[0031] determining whether a catalyst of the vehicle is in a fast heating demand state;

[0032] determining whether an oil pump of the vehicle is in a high load demand state;

[0033] determining whether a fan of the vehicle is in a high load state;

[0034] when one or more of the catalyst being in the fast heating demand state, the oil pump being in the high load demand state, and the fan being in the high load state, determining that the low-voltage load has the charging voltage boosting requirement.

[0035] Optionally, the step of determining whether a catalyst of the vehicle is in a fast heating demand state comprises:

[0036] when a temperature of a coolant of an engine of the vehicle is higher than a temperature threshold, an exhaust temperature upstream of the catalyst is reliable, and the exhaust temperature is lower than an air temperature threshold, determining that the catalyst is in the fast heating demand state.

[0037] Optionally, the step of determining whether an oil pump of the vehicle is in a high load demand state comprises:

[0038] when a load of the oil pump is greater than a load threshold, determining that the oil pump is in the high load demand state.

[0039] Optionally, the step of determining whether a fan of the vehicle is in a high load state comprises:

[0040] when an opening degree of the fan is greater than an opening degree threshold, determining that the fan is in the high load state.

[0041] Optionally, the step of setting the output voltage of the DCDC converter according to a voltage level corresponding to the charging voltage boosting requirement comprises:

[0042] when one of the catalyst being in the fast heating demand state, the oil pump being in the high load demand state, and the fan being in the high load state occurs, controlling the DCDC converter to output the voltage according to a voltage level corresponding to the occurred state;

[0043] when at least two of the catalyst being in the fast heating demand state, the oil pump being in the high load demand state, and the fan being in the high load state occur, controlling the DCDC converter to output the voltage according to a highest voltage level among voltage levels corresponding to the occurred states.

[0044] Optionally, the voltage level corresponding to the condition that the catalytic converter is in a fast heating demand is lower than the voltage level corresponding to the condition that the oil pump is in a high load demand.

[0045] The voltage level corresponding to the condition that the oil pump is in a high load demand is the same as the voltage level corresponding to the condition that the fan is in a high load demand.

[0046] In particular, according to the second aspect of the embodiments of the present application, a DCDC output voltage control system of a hybrid vehicle is provided, comprising a control unit, the control unit comprising a memory and a processor, the memory storing a control program, the control program being executed by the processor to implement the DCDC output voltage control method according to any one of the above.

[0047] The DCDC converter of the present application determines the charging demand of the low-voltage load when the vehicle is neither in a high power output demand state nor in an engine abnormal shutdown state, and if the low-voltage load has a charging voltage boost demand and the amount of electricity of the high-voltage battery is greater than the amount of electricity threshold at this time, the output voltage is set according to the voltage level corresponding to the specific situation of the charging voltage boost demand. The output voltage of the DCDC converter is not boosted when the vehicle is in a high power output demand state or an engine abnormal shutdown state. That is, the setting method of the output voltage of the DCDC converter is specifically defined, and the output voltage of the DCDC converter is controlled and adjusted according to the operating state of the vehicle and the situation of the low-voltage load, which can optimize the fuel economy of the hybrid powertrain system.

[0048] Further, setting the output voltage of the DCDC converter according to the voltage level corresponding to the charging voltage boost demand can meet the charging demand of the low-voltage load under different charging voltage boost demands, and further ensure the fuel economy of the vehicle.

[0049] Further, the present application further sends a request to reduce the power of the low-voltage load when the vehicle is in a high power output demand state or an engine abnormal shutdown state, so as to reduce the consumption of the amount of electricity by the low-voltage load as much as possible when the vehicle is in a high power output demand state or an engine abnormal shutdown state, thereby ensuring the basic operation of the vehicle.

[0050] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, the content of the specification can be implemented, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described.

[0051] According to the detailed description of the specific embodiments of the present application in combination with the drawings below, those skilled in the art will more clearly understand the above and other purposes, advantages and features of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0052] Some specific embodiments of the present application will be described in detail below with reference to the attached drawings. The same or similar components or parts are designated by the same or similar reference numerals in the drawings. It should be understood by those skilled in the art that the drawings are not necessarily drawn to scale. In the drawings:

[0053] Figure 1 is a flowchart of a DCDC output voltage control method according to an embodiment of the present application;

[0054] Figure 2 is a flowchart of a DCDC output voltage control method according to another embodiment of the present application;

[0055] Figure 3 is a schematic diagram of a DCDC output voltage control system according to an embodiment of the present application. DETAILED DESCRIPTION

[0056] Exemplary embodiments of the present disclosure will be described below in greater detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be embodied in various forms without being limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thoroughly and completely understood, and will fully convey the scope of the present disclosure to those skilled in the art.

[0057] Figure 1 is a flowchart of a DCDC output voltage control method according to an embodiment of the present application. The DCDC output voltage control method of the present application is used in a hybrid vehicle including a DCDC converter for converting and outputting a voltage of a high-voltage battery as a low-voltage voltage for use in low-voltage loads of the vehicle when in a step-down operation mode. As shown in Figure 1 , in one embodiment, the method includes:

[0058] Step S100, when the DCDC converter is in the step-down operation mode, determining whether the vehicle is in a high-power output demand state or an engine abnormal shutdown state, if so, proceeding to step S200, otherwise proceeding to step S300.

[0059] Step S200, setting an output voltage of the DCDC converter to a normal target voltage to control the DCDC converter to output according to the normal target voltage. Generally, the normal target voltage is a voltage value between 12.2-15V, which is set according to the 12V battery SOC and its charge / discharge current.

[0060] Step S300, judging whether the low-voltage load has a charging voltage boosting demand, and setting the output voltage of the DCDC converter according to the voltage level corresponding to the charging voltage boosting demand when the low-voltage load has the charging voltage boosting demand and the electric quantity of the high-voltage battery is greater than the electric quantity threshold, so as to meet the charging demand of the low-voltage load. The electric quantity threshold is taken as the electric quantity value capable of meeting the boosted DCDC output voltage, for example, when the SOC of the high-voltage battery is greater than 32%, the DCDC converter is allowed to boost the output voltage.

[0061] The DCDC converter of the embodiment judges the charging demand of the low-voltage load when the vehicle is neither in the high-power output demand state nor in the engine abnormal flameout state, and sets the corresponding output voltage according to the voltage level corresponding to the specific situation of the charging voltage boosting demand when the low-voltage load has the charging voltage boosting demand and the electric quantity of the high-voltage battery is greater than the electric quantity threshold. The output voltage of the DCDC converter is not boosted when the vehicle is in the high-power output demand state or the engine abnormal flameout state. That is, the setting mode of the output voltage of the DCDC converter is defined, and the output voltage of the DCDC converter is controlled and adjusted according to the running state of the vehicle and the situation of the low-voltage load, which can optimize the fuel economy of the hybrid power assembly system.

[0062] Further, the output voltage of the DCDC converter is set according to the voltage level corresponding to the charging voltage boosting demand, which can meet the charging demand of the low-voltage load under different charging voltage boosting demands, and further guarantees the fuel economy of the vehicle.

[0063] Figure 2 is a flowchart of the DCDC output voltage control method according to another embodiment of the application. In another embodiment, as shown in Figure 2 , step S100 further includes:

[0064] Step S20, judging whether the vehicle is in the DCDC enabled state, and entering step S40 if yes.

[0065] Step S40, judging whether a voltage reduction request instruction is received, and entering step S60 if yes.

[0066] Step S60, controlling the DCDC converter to prepare for voltage conversion and timing, and controlling the DCDC converter to switch to the voltage reduction working mode when the timing time reaches the preset delay time.

[0067] In the embodiment, when the vehicle is in the DCDC enabled state and receives the voltage reduction request instruction, the vehicle enters the delay state, i.e. the DCDC converter does not immediately enter the voltage reduction working mode, but delays for a period of time to improve the voltage and prepare for voltage conversion. When the delay time is up, the state of the DCDC converter is transitioned to the voltage reduction working mode. Of course, there should be no fault of prohibiting voltage conversion during the process, and once there is such a fault, the DCDC converter stops working, for example, the hardware of the DCDC converter fails, etc., to ensure normal voltage conversion. The embodiment sets the delay state to ensure that the DCDC converter is ready for voltage when entering the voltage reduction working mode, thereby ensuring the smooth progress of the voltage reduction work.

[0068] In a further embodiment, the step S20 includes a determination process of the pre-enabled state and the enabled state. When the high-voltage battery of the vehicle is in the power supply state, the vehicle receives the start request instruction, the high-voltage battery is in the state capable of maintaining the preset power, the DCDC converter is in the state capable of normally receiving and transmitting signals, and the high-voltage system has no fault, it is determined that the DCDC converter is in the pre-enabled state. Alternatively, when the engine electronic control module (ECM) of the vehicle has sent a request to the power battery energy control module (BECM) to attract the high-voltage battery main relay, and the ECM has received the feedback information from the BECM that the high-voltage battery main relay has been attracted, it is determined that the high-voltage battery is in the power supply state. Alternatively, the start request instruction is the start request input by the driver or the remote start request, at this time the vehicle is in the state of partially powering the low-voltage accessories, but not ignited. Alternatively, when the SOC of the high-voltage battery is not too low (for example, the SOC is less than 25%) and cannot be charged, or is in the case of large current power consumption (for example, the power consumption current is greater than 1A), it is determined that the high-voltage battery is in the state capable of maintaining the preset power. Alternatively, when there is no case that the relay of the high-voltage battery has been requested to be attracted for a certain period of time but the DCDC cannot be enabled, and there is no case that the DCDC has been requested to be enabled but the DCDC cannot be enabled (which can be determined according to the feedback signal of the DCDC), the DCDC converter is in the state capable of normally receiving and transmitting signals.

[0069] When the DCDC converter is in the pre-enabled state, if the ignition signal (KL15 power-on) is received and it is determined that the motor of the vehicle has no fault, it is determined that the DCDC converter is in the enabled state, i.e. the DCDC enabled state.

[0070] The embodiment defines the DCDC enabled state, at this time the DCDC converter is in the state of having been powered on and can normally receive and transmit signals, i.e. the initialization state of not receiving the voltage conversion request.

[0071] In one embodiment, the high power output demand state includes at least one of a start-up state, a full throttle acceleration state, a running high throttle start-up state, and a crawl start-up gear engagement state. That is, the step of determining whether the vehicle is in the high power output demand state or the engine abnormal shutdown state in step S100 includes:

[0072] In step S102, it is determined whether the vehicle is in at least one of the start-up state, the full throttle acceleration state, the running high throttle start-up state, the crawl start-up gear engagement state, and the engine abnormal shutdown state.

[0073] In one embodiment, the vehicle is determined to be in the start-up state when the engine of the vehicle is started for the first time in the same driving cycle for less than a first limit value or is started for a non-first time for less than a second limit value, wherein the first limit value is greater than the second limit value. Optionally, the first limit value is any value in the range of 10-20s and the second limit value is any value in the range of 5-10s. Since the first start-up consumes more power, the first limit value is set to be larger.

[0074] When the vehicle is in the start-up state, the power consumption is large, and thus the load power consumption needs to be reduced, and the event of triggering the DCDC converter to boost the output voltage cannot be triggered.

[0075] In one embodiment, the vehicle is determined to be in the full throttle acceleration state when the throttle pedal opening of the vehicle is greater than a first opening limit value, the vehicle is in a forward gear or a reverse gear, and the time for which the throttle pedal opening is greater than the first opening limit value is less than a third limit value. The first opening limit value is defined as the full throttle acceleration limit value of the vehicle, i.e., greater than the first opening limit value indicates that the vehicle has a demand for full throttle acceleration.

[0076] In one embodiment, the vehicle is determined to be in the running high throttle start-up state when the engine of the vehicle is in a running state, the vehicle speed is less than a start-up vehicle speed threshold value, the reserve torque of the engine is less than a torque threshold value, the opening of the throttle pedal of the vehicle is greater than a second opening limit value, the difference between the maximum torque of the engine and the requested torque of the driver is less than a difference threshold value, and the current air conditioner compressor power is greater than a power limit value. The reserve torque is the difference between the maximum torque of the engine and the current actual torque. Optionally, the vehicle speed threshold value is 20kph, the second opening limit value is 5%, the difference threshold value is 50Nm, and the torque threshold value is any value in the range of 50-100Nm. The difference between the maximum torque of the engine and the requested torque of the driver being less than the difference threshold value indicates that the requested torque of the driver is close to the maximum torque of the engine.

[0077] In one embodiment, the vehicle is determined to be in a creeping start-up state when the engine is running and the starting time is less than the fourth limit, the vehicle speed is less than the starting speed threshold, the engine's reserve torque is less than the torque threshold, no accelerator pedal opening information is received, and the vehicle is in drive or reverse gear. Optionally, the fourth limit is 1000s. When the vehicle is in a creeping start-up state, the engine speed may drop when cold; in this case, the DC-DC converter should be prohibited from increasing the output voltage.

[0078] In one embodiment, the vehicle is determined to be in an abnormal engine shutdown state when the vehicle's engine is running, the engine speed is less than the target idle speed and the absolute value of the difference between the two is greater than a speed difference limit, the engine speed acceleration is negative and the absolute value of the speed acceleration is less than an acceleration limit, and the predicted engine speed is less than a shutdown speed threshold. Optionally, the target idle speed is 400 rpm, the acceleration limit is 5 rpm / s, and the shutdown speed threshold is 500 rpm. Here, the predicted engine speed refers to the next speed predicted based on the current speed and speed acceleration.

[0079] In another embodiment, when the vehicle is in a high power output demand state or the engine is abnormally shut down, the following is also included:

[0080] Step S250: Send a request to reduce the power of the low-voltage load. For example, control accessories may be turned off, fan opening may be reduced, and air conditioning power may be reduced, thereby minimizing the power consumption of the low-voltage load when the vehicle is in a high power output demand state or the engine is abnormally shut down, thus ensuring the basic operating needs of the vehicle.

[0081] like Figure 2 As shown, step S300, which involves determining whether the low-voltage load requires a charging voltage boost, includes:

[0082] Step S302: Determine whether one of the following conditions occurs: the vehicle's catalytic converter is in a state of rapid heating demand, the vehicle's oil pump is in a state of high load demand, or the vehicle's fan is in a state of high load. If so, determine that the low-voltage load has a charging voltage boosting demand.

[0083] In one embodiment, the catalytic converter is determined to be in a rapid heating demand state when the engine coolant temperature is above a temperature threshold, the exhaust temperature upstream of the catalytic converter is reliable, and the exhaust temperature is below an ambient temperature threshold. Optionally, the temperature threshold is 18°C, and the ambient temperature threshold is 170°C. Whether the exhaust temperature is reliable can be determined by the accuracy of the signal. When the catalytic converter is in a rapid heating demand state, the catalytic converter temperature needs to rise more quickly to ensure the vehicle's emissions.

[0084] In one embodiment, when the load on the oil pump is greater than the load threshold, the oil pump is determined to be in a high-load demand state.

[0085] In one embodiment, when the opening of the fan is greater than the opening threshold, it is determined that the fan is in a high load state. Optionally, the opening threshold is 60%. Here, the fan refers to the fan of the thermal management system of the vehicle.

[0086] In a further embodiment, as shown in FIG. 3, the step of setting the output voltage of the DCDC converter to the voltage level corresponding to the charging voltage boosting requirement in step S300 includes: Figure 2

[0087] In step S304, when one of the following conditions occurs: the catalytic converter is in a fast heating requirement state, the oil pump is in a high load requirement state, and the fan is in a high load state, the DCDC converter is controlled to output voltage according to the voltage level corresponding to the occurred condition.

[0088] In step S306, when at least two of the following conditions occur: the catalytic converter is in a fast heating requirement state, the oil pump is in a high load requirement state, and the fan is in a high load state, the DCDC converter is controlled to output voltage according to the voltage level with the highest level among the voltage levels corresponding to the occurred conditions.

[0089] In one embodiment, the voltage level corresponding to the catalytic converter being in a fast heating requirement state is lower than the voltage level corresponding to the oil pump being in a high load requirement state. The voltage level corresponding to the oil pump being in a high load requirement state is the same as the voltage level corresponding to the fan being in a high load state. The corresponding output voltage can be determined according to the voltage level.

[0090] For example, the voltage levels corresponding to the oil pump being in a high load requirement state and the fan being in a high load state are both set to 3, and the corresponding output voltage of the DCDC converter is 15.2V; the voltage level corresponding to the catalytic converter being in a fast heating requirement state is set to 2, and the corresponding output voltage of the DCDC converter is 14V. Of course, the voltage levels are not limited to the above two, and can also include levels 0 and 1, corresponding to 12.2-15V (i.e. the normal target voltage mentioned above) and 13.6V, respectively, to cope with other vehicle states. The division of voltage levels is not limited to this, and is not limited herein.

[0091] ​The application further provides a DCDC output voltage control system of a hybrid vehicle, comprising a control unit, the control unit comprising a memory and a processor, the memory storing a control program, the control program being executed by the processor to implement the DCDC output voltage control method according to any one of the above embodiments or a combination of the above embodiments. The processor can be a central processing unit (CPU) or a digital processing unit, etc. The processor transmits and receives data through a communication interface. The memory is used to store the program executed by the processor. The memory is any medium capable of carrying or storing desired program code in the form of instructions or data structures and capable of being accessed by a computer, and can also be a combination of multiple memories. The above-mentioned control program can be downloaded to the corresponding computing / processing device from the computer-readable storage medium or downloaded to the computer or external storage device via a network (such as the Internet, a local area network, a wide area network, and / or a wireless network).

[0092] Figure 3 is a schematic diagram of a DCDC output voltage control system according to an embodiment of the application. In one embodiment, as shown in Figure 3 the hybrid vehicle comprises a battery energy control module (BECM), an engine electronic control module (ECM), a motor controller (IGM), a gateway (VDDM), a vehicle electronic controller (CEM), and a 12V battery voltage sensor.

[0093] The engine electronic control module is in communication connection with the battery energy control module, and can obtain information about whether the main relay of the high-voltage battery is attracted through the battery energy control module. For example, the engine electronic control module sends a high-voltage battery attraction request to the battery energy control module, and when receiving the information that the battery energy control module has been attracted, it is determined that the main relay of the high-voltage battery has been attracted.

[0094] The engine electronic control module is also in communication connection with the motor controller, and sends a DCDC enable request to the motor controller. The motor controller is used to monitor whether the DCDC converter is in an enabled state and feed back the enabled state information to the engine electronic control module. When the engine electronic control module receives the state information that the DCDC converter has been enabled, it determines the voltage level of the DCDC converter according to the state of the vehicle. The engine electronic control module is also used to send the voltage level to the vehicle electronic controller through the gateway, so that the vehicle electronic controller sets the output voltage of the DCDC converter according to the battery state fed back by the 12V battery voltage sensor and the voltage level, and forwards the set output voltage to the motor controller through the gateway, so that the motor controller controls the DCDC converter to output voltage according to the set output voltage.

[0095] At this point, those skilled in the art will appreciate that although exemplary embodiments of the present application have been shown and described herein, many changes and modifications can be made to the described embodiments without departing from the spirit and scope of the present application. Accordingly, the scope of the present application should be understood to cover all such changes and modifications.

Claims

1. A DCDC output voltage control method of a hybrid vehicle, the vehicle comprising a DCDC converter for converting and outputting a voltage of a high-voltage battery to a low-voltage voltage for use by a low-voltage load of the vehicle when in a step-down operation mode, the method comprising: determining whether the vehicle is in a high-power output demand state or an engine abnormal shutdown state when the DCDC converter is in the step-down operation mode; setting an output voltage of the DCDC converter to a normal target voltage to control the DCDC converter to output according to the normal target voltage if the vehicle is in the high-power output demand state or the engine abnormal shutdown state; otherwise, determining whether the low-voltage load has a charging voltage boost demand, and setting the output voltage of the DCDC converter according to a voltage level corresponding to the charging voltage boost demand if the low-voltage load has the charging voltage boost demand and a state of charge of the high-voltage battery is greater than a state of charge threshold, so as to meet a charging demand of the low-voltage load; the step of determining whether the low-voltage load has the charging voltage boost demand comprises: determining whether a catalyst of the vehicle is in a rapid heating demand state; determining whether an oil pump of the vehicle is in a high-load demand state; determining whether a fan of the vehicle is in a high-load state; determining that the low-voltage load has the charging voltage boost demand if one or more of the following conditions occurs: the catalyst is in the rapid heating demand state, the oil pump is in the high-load demand state, and the fan is in the high-load state; the step of setting the output voltage of the DCDC converter according to the voltage level corresponding to the charging voltage boost demand comprises: controlling the DCDC converter to output the voltage according to a voltage level corresponding to an occurred condition if one of the following conditions occurs: the catalyst is in the rapid heating demand state, the oil pump is in the high-load demand state, and the fan is in the high-load state; or controlling the DCDC converter to output the voltage according to a highest voltage level among voltage levels corresponding to occurred conditions if at least two of the following conditions occur: the catalyst is in the rapid heating demand state, the oil pump is in the high-load demand state, and the fan is in the high-load state, wherein the voltage level corresponding to the catalyst being in the rapid heating demand state is lower than the voltage level corresponding to the oil pump being in the high-load demand state, and the voltage level corresponding to the oil pump being in the high-load demand state is the same as the voltage level corresponding to the fan being in the high-load state; and the method further comprises, before the step of determining whether the vehicle is in the high-power output demand state or the engine abnormal shutdown state when the DCDC converter is in the step-down operation mode: determining whether the vehicle is in a DCDC enabled state; controlling the DCDC converter to prepare for voltage conversion and timing when the vehicle is in the enabled state and a step-down request instruction is received, and controlling the DCDC converter to switch to the step-down operation mode when a timing time reaches a preset delay time; and the step of determining whether the vehicle is in the DCDC enabled state comprises: determining whether a DCDC switch of the vehicle is in an on state. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2. The DCDC output voltage control method according to claim 1, wherein, ​ ​ ​ 3. The DCDC output voltage control method according to claim 2, wherein, ​ determining that the DCDC converter is in a pre-enabled state when the high-voltage battery of the vehicle is in a power-supplyable state, the vehicle receives a start request instruction, the high-voltage battery is in a state capable of maintaining a preset power amount, the DCDC converter is in a state capable of normally transmitting and receiving signals, and the high-voltage system is in a fault-free state; determining that the DCDC converter is in an enabled state when an ignition signal is received and it is determined that the motor of the vehicle is in a fault-free state when the DCDC converter is in the pre-enabled state.

4. The DCDC output voltage control method according to any one of claims 1 to 3, wherein the high-power output demand state includes at least one of a start-up state, a full-throttle acceleration state, a running large-throttle start-up state, and a crawl start-up gear engagement state.

5. The DCDC output voltage control method according to claim 4, wherein, the step of determining whether the vehicle is in a high-power output demand state includes: determining that the vehicle is in the start-up state when the first start-up time of the engine of the vehicle in the same driving cycle is less than a first limit value or the non-first start-up time is less than a second limit value, wherein the first limit value is greater than the second limit value.

6. The DCDC output voltage control method of claim 4, wherein, the step of determining whether the vehicle is in a high-power output demand state includes: determining that the vehicle is in the full-throttle acceleration state when the opening degree of the accelerator pedal of the vehicle is greater than a first opening degree limit value, the vehicle is in a forward gear or a reverse gear, and the time for which the opening degree of the accelerator pedal is greater than the first opening degree limit value is less than a third limit value.

7. The DCDC output voltage control method of claim 4, wherein, the step of determining whether the vehicle is in a high-power output demand state includes: determining that the vehicle is in the running large-throttle start-up state when the engine of the vehicle is in a running state, the vehicle speed is less than a start-up vehicle speed threshold value, the reserve torque of the engine is less than a torque threshold value, the opening degree of the accelerator pedal of the vehicle is greater than a second opening degree limit value, the difference between the maximum torque of the engine and the requested torque of the driver is less than a difference threshold value, and the current air conditioner compressor power is greater than a power limit value.

8. The DCDC output voltage control method of claim 4, wherein, the step of determining whether the vehicle is in a high-power output demand state includes: determining that the vehicle is in the crawl start-up gear engagement state when the engine of the vehicle is in a running state, the start-up time is less than a fourth limit value, the vehicle speed is less than a start-up vehicle speed threshold value, the reserve torque of the engine is less than a torque threshold value, no opening degree information of the accelerator pedal is received, and the vehicle is in a forward gear or a reverse gear.

9. The DCDC output voltage control method of claim 1, wherein, the step of determining whether the vehicle is in an engine abnormal flameout state includes: determining that the vehicle is in an engine abnormal flameout state when the engine of the vehicle is in a running state, the rotational speed of the engine is less than a target idle speed, the absolute value of the difference between the two is greater than a rotational speed difference limit value, the rotational speed acceleration of the engine is negative, the absolute value of the rotational speed acceleration is less than an acceleration limit value, and the predicted rotational speed of the engine is less than a flameout rotational speed threshold value.

10. The DCDC output voltage control method of claim 1, wherein, the step of determining whether the catalytic converter of the vehicle is in a rapid heating demand state includes: determining that the catalytic converter is in a rapid heating demand state when the temperature of the coolant of the engine of the vehicle is higher than a temperature threshold value, the exhaust gas temperature upstream of the catalytic converter is reliable, and the exhaust gas temperature is lower than an air temperature threshold value.

11. The DCDC output voltage control method of claim 1, wherein, The step of determining whether the oil pump of the vehicle is in a high load demand state includes: determining that the oil pump is in a high load demand state when a load of the oil pump is greater than a load threshold.

12. The DCDC output voltage control method of claim 1, wherein, The step of determining whether the fan of the vehicle is in a high load state includes: determining that the fan is in a high load state when an opening of the fan is greater than an opening threshold.

13. A DCDC output voltage control system of a hybrid vehicle, comprising a control unit including a memory and a processor, a control program being stored in the memory and being executed by the processor to implement the DCDC output voltage control method according to any one of claims 1-12.

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