Power generation control method for extended-range electric vehicle

Abstract

The invention discloses a power generation control method for an extended-range electric vehicle, which comprises the following steps: step S10, performing power-on initialization, loading high-voltage read on the whole vehicle, and enabling a driver to control the vehicle to run; s20, the battery state is monitored in real time through the VCU, whether the APU needs to be started or not is judged, if yes, an APU starting instruction is sent to the RCU through the VCU, the next step is carried out, and if not, judgment is repeated; s30, judging whether the engine is successfully started or not through the RCU, if yes, sending that the APU is successfully started to the VCU through the RCU, and executing the next step, and if not, repeating judgment; and S40, after the APU is successfully started, a start success flag bit is sent to the VCU, the VCU judges that the APU is successfully started after receiving the start success flag bit, and the VCU sends a power generation control mode which is a voltage control mode to the RCU. According to the invention, the operation capability of the whole vehicle after failure is effectively improved, the after-sales maintenance cost of the vehicle is reduced, the vehicle use experience of a driver is improved, the situation that the battery is not allowed to be charged due to extremely low environment temperature is avoided, and the service life of the battery is protected.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy vehicles, and in particular, relates to a method for controlling power generation of an extended-range electric vehicle. Background Art

[0002] Existing extended-range electric vehicles are equipped with a range extender (hereinafter referred to as "APU"), and the whole vehicle is driven by pure electricity. The pure electric drive system is powered by a high-voltage battery and an APU. When the whole vehicle is fully charged, the battery is discharged alone to power the pure electric drive system. When the battery power is low, the APU starts to generate electricity to power the drive system. The whole vehicle has dual-source power and a continuous supply of energy, which solves the pain points of insufficient battery life and inconvenient energy replenishment of pure electric vehicles. When the APU generates electricity, the generator adopts speed control and the engine adopts torque control, that is, the APU works in speed and torque control mode, the generator adopts a permanent magnet synchronous motor (hereinafter referred to as "PMSM"), and the control architecture adopts rotor field oriented control (hereinafter referred to as "FOC"). For the speed control of the generator, based on the dual closed-loop structure of the speed outer loop and the current inner loop, the VCU calculates the required power generation of the APU based on the vehicle energy management strategy, and sends it to the range extender assembly controller (hereinafter referred to as "RCU") for execution through the bus message signal. After receiving the power generation demand of the VCU, the RCU performs power decoupling, sends the speed command to the generator controller (hereinafter referred to as "GCU") for execution, and sends the torque command to the engine control unit (hereinafter referred to as "EMS") for execution. For the FOC of PMSM, it is necessary to perform speed closed-loop control based on stable external high voltage.

[0003] However, for existing extended-range electric vehicles, if the battery has an abnormality and reports a serious fault, and the entire vehicle needs to operate at high voltage or zero power, the VCU in the conventional control strategy will make a decision and then control the entire vehicle to operate at high voltage or zero power. High voltage or zero power processing will cause the entire vehicle to be unable to drive. Summary of the invention

[0004] The present invention provides a method for controlling power generation of an extended-range electric vehicle, which solves the problems raised in the above-mentioned background technology.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for controlling power generation of an extended-range electric vehicle, comprising the following steps: Step S10, power on and initialize, the whole vehicle is ready with high voltage, and then the driver controls the vehicle to drive; Step S20, monitor the battery status in real time through the VCU, and determine whether the APU needs to be started. If yes, send an APU start instruction to the RCU through the VCU, and proceed to the next step. If no, repeat the determination; Step S30, the RCU determines whether the engine is started successfully. If yes, the RCU sends a message to the VCU that the APU is started successfully and proceeds to the next step. If no, the determination is repeated. Step S40: After the APU is successfully started, it will send a startup success flag to the VCU. After receiving the flag, the VCU determines that the APU has been successfully started, and the VCU will send a power generation control mode to the RCU as the voltage control mode; Step S50: The RCU executes a voltage control mode.

[0006] Preferably, the step S20 includes the following steps: Step S21, monitoring the fault reported by the battery in real time through the fault monitoring system of the VCU; Step S22, determining whether the battery has a level 4 or level 5 serious fault, if so, sending an APU start instruction to the RCU through the VCU, if not, repeating the determination; Step S23: This step is executed synchronously with step S21, and the battery capacity monitoring system of the VCU monitors the minimum temperature of the battery cell and the charge and discharge capacity of the battery in real time; Step S24, determining whether the peak charging and continuous discharging capabilities of the battery are both lower than the threshold, if so, proceed to the next step, if not, repeat the determination; Step S25, determining whether the available peak discharge of the battery is greater than the power required to start the APU at the current temperature, if so, sending an APU start instruction to the RCU via the VCU, if not, repeating the determination.

[0007] Preferably, the step S30 includes the following steps: Step S31, after receiving the start command from the VCU, the RCU sends a speed control command to the GCU; Step S32, the GCU outputs three-phase AC power to drive the PMSM to run and then drive the engine to run; Step S33, determine whether the engine speed is greater than a threshold, if so, the RCU will send an injection command to the EMS, if not, repeat the determination; Step S34, EMS controls the engine fuel injection and ignition; Step S35, the RCU determines whether the engine is started successfully. If so, the RCU sends a message to the VCU to start the APU successfully. If not, the determination is repeated.

[0008] Preferably, the step S40 includes the following steps: Step S41, controlling the power consumption of high-voltage accessories through the VCU; Step S42, determine whether the DC bus current is less than a threshold value, if so, the VCU immediately sends a command to disconnect the main positive relay and the main negative relay to the BMS, and proceeds to the next step, if not, continue to determine; Step S43, the BMS controls the battery main positive relay and the main negative relay in the high-voltage circuit to be disconnected; Step S44, the VCU immediately sends a signal to the RCU that the power generation control mode is the voltage control mode.

[0009] Preferably, the step S50 includes the following steps: Step S51, RCU controls APU to enter voltage control mode to maintain constant voltage output; Step S52, the VCU calculates the required APU power generation in real time according to the vehicle energy management strategy and sends it to the RCU for execution; Step S53, the RCU calculates the engine target torque based on the APU power generation power required by the VCU combined with the preset system efficiency and current speed and sends it to the EMS for execution; Step S54, the EMS controls the throttle opening and the fuel injection amount based on the air-fuel ratio target coefficient being 1; Step S55, determining whether the battery fault has disappeared, or the battery charge and discharge capacity is greater than a threshold value, if so, the VCU controls the power consumption of the high-voltage components, and immediately controls the execution of the high-voltage process, if not, repeating the determination; Step S56, the VCU immediately sends to the RCU that the power generation control mode is the speed torque control mode.

[0010] The beneficial effects of adopting the above technical solution are: 1. In the present invention, when a high-voltage battery fails or the ambient temperature is extremely low, resulting in an extremely low battery discharge capacity, the generator adopts a voltage control mode, so that after the high-voltage battery is cut off, the APU can still have a certain power generation capacity to support the vehicle to enter the limp home mode, effectively improving the vehicle's post-failure operating capacity, reducing vehicle after-sales maintenance costs, and improving the driver's car experience. It also avoids the problem of battery overcharging due to the extremely low ambient temperature that the battery is not allowed to charge, the APU power following control, and the delayed response of the APU to reduce power generation when driving to coasting or braking, thereby protecting the battery life.

[0011] 2. In the present invention, after the APU enters the voltage control mode, the VCU will immediately control the battery main positive relay and the main negative relay in the high-voltage circuit to disconnect, and control the power consumption of the high-voltage accessories during disconnection to prevent the main positive relay from disconnecting when the DC bus current exceeds the threshold, causing arcing and sparking, affecting the life of the main positive relay, and causing the main positive relay to stick in severe cases. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the overall architecture diagram provided by the present invention; Figure 2 is a control strategy flow chart of step S20; Figure 3is a control strategy flow chart of step S30; Figure 4 is a control strategy flow chart of step S40; Figure 5 It is a control strategy flow chart of step S50. DETAILED DESCRIPTION

[0013] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0014] Specifically, Figures 1 to 5 As shown, a method for controlling power generation of an extended-range electric vehicle comprises the following steps: Step S10, power on and initialize, the whole vehicle is ready with high voltage, and then the driver controls the vehicle to drive; Step S20, monitor the battery status in real time through the VCU, and determine whether the APU needs to be started. If yes, send an APU start instruction to the RCU through the VCU, and proceed to the next step. If no, repeat the determination; Step S30, the RCU determines whether the engine is started successfully. If yes, the RCU sends a message to the VCU that the APU is started successfully and proceeds to the next step. If no, the determination is repeated. Step S40: After the APU is successfully started, it will send a startup success flag to the VCU. After receiving the flag, the VCU determines that the APU has been successfully started, and the VCU will send a power generation control mode to the RCU as the voltage control mode; Step S50: The RCU executes a voltage control mode.

[0015] It should be noted that for extended-range electric vehicles, if the battery has an abnormality and reports a serious fault that requires the entire vehicle to operate at high voltage or zero power, the VCU in the conventional control strategy will make a decision and then control the entire vehicle to operate at high voltage or zero power limit. High voltage or zero power processing will cause the entire vehicle to be unable to drive. The ordinary fault handling strategy does not fully utilize the advantages of dual-source power. If the high-voltage battery can be cut off from the high-voltage circuit after the battery reports a serious fault, allowing the APU to generate electricity independently and allow the entire vehicle to continue driving, it will greatly improve the operating capacity of the entire vehicle after a fault, provide great convenience for the driver to drive the vehicle to the after-sales maintenance center in time, reduce the vehicle's after-sales maintenance costs, and improve the driver's car experience.

[0016] In this embodiment, after the high-voltage battery fails or the ambient temperature is extremely low, resulting in an extremely low battery discharge capacity, the generator adopts a voltage control mode, so that after the high-voltage battery is cut off, the APU can still have a certain power generation capacity to support the vehicle to enter limp mode, effectively improving the vehicle's post-failure operating capability, reducing vehicle after-sales maintenance costs, and improving the driver's car experience. It also avoids the problem of the battery overcharging caused by the extremely low ambient temperature, the APU power following control, and the delayed response of the APU to reduce power generation when the drive switches to coasting or braking, thereby protecting the battery life.

[0017] The step S20 comprises the following steps: Step S21, monitoring the fault reported by the battery in real time through the fault monitoring system of the VCU; Step S22, determining whether the battery has a level 4 or level 5 serious fault, if so, sending an APU start instruction to the RCU through the VCU, if not, repeating the determination; Step S23: This step is executed synchronously with step S21, and the battery capacity monitoring system of the VCU monitors the minimum temperature of the battery cell and the charge and discharge capacity of the battery in real time; Step S24, determining whether the peak charging and continuous discharging capabilities of the battery are both lower than the threshold, if so, proceed to the next step, if not, repeat the determination; Step S25, determining whether the available peak discharge of the battery is greater than the power required to start the APU at the current temperature, if so, sending an APU start instruction to the RCU via the VCU, if not, repeating the determination.

[0018] It should be noted that the fault monitoring system of the VCU will monitor the faults reported by the battery in real time. If the battery reports a high-level fault (such as a fault above level 4, excluding thermal runaway faults, involving safety and requiring immediate high voltage evacuation of the vehicle), causing the vehicle to perform zero torque processing or delay high voltage, the VCU believes that a serious fault has occurred in the battery and that protective measures need to be taken for the battery. In the conventional control strategy, the VCU will immediately take zero torque processing or delay high voltage (processing is set according to the fault level). This processing strategy immediately deprives the vehicle of its operating ability after a serious battery fault occurs, and even basic comfort functions such as air conditioning cannot be used. Therefore, it will have a great impact on the driving experience. The driver needs to tow the vehicle in time and troubleshoot and repair the vehicle, which increases the vehicle maintenance cost. In addition, the battery capacity monitoring system of the VCU will monitor the minimum temperature of the battery cell and the charging and discharging capacity in real time. When the minimum battery temperature is lower than the threshold, and the battery's continuous charging capacity and continuous discharging capacity are both lower than the threshold, the VCU believes that the ambient temperature is extremely low and the battery has lost a large discharge capacity to power the drive system. If the APU works at a larger power generation power, after the vehicle drive switches to coasting, that is, after the driver releases the accelerator, or after the drive switches to braking, that is, after the driver releases the accelerator and steps on the brake pedal, the APU's power generation power decreases slowly due to the physical characteristics of the engine's slow response to torque control, while the drive motor responds quickly (in tens of milliseconds). The APU's excess power generation will flow to the battery, causing the battery to recharge overcurrent or severe recharge overcurrent, seriously affecting the battery life. At the same time, the battery will report a high-level fault, and the vehicle will also perform protection processing to affect vehicle driving.

[0019] The step S30 comprises the following steps: Step S31, after receiving the start command from the VCU, the RCU sends a speed control command to the GCU; Step S32, the GCU outputs three-phase AC power to drive the PMSM to run and then drive the engine to run; Step S33, determine whether the engine speed is greater than a threshold, if so, the RCU will send an injection command to the EMS, if not, repeat the determination; Step S34, EMS controls the engine fuel injection and ignition; Step S35, the RCU determines whether the engine is started successfully. If so, the RCU sends a message to the VCU to start the APU successfully. If not, the determination is repeated.

[0020] It should be noted that the VCU enables the voltage control mode of the APU and controls the APU to start running and enter the voltage control mode at an appropriate time. Starting the APU at an appropriate time means that when the APU enters the voltage control mode, it needs to provide the rated working voltage externally to enter.

[0021] The step S40 comprises the following steps: Step S41, controlling the power consumption of high-voltage accessories through the VCU; Step S42, determine whether the DC bus current is less than a threshold value, if so, the VCU immediately sends a command to disconnect the main positive relay and the main negative relay to the BMS, and proceeds to the next step, if not, continue to determine; Step S43, the BMS controls the battery main positive relay and the main negative relay in the high-voltage circuit to be disconnected; Step S44, the VCU immediately sends a signal to the RCU that the power generation control mode is the voltage control mode.

[0022] It should be noted that after the VCU controls the battery main positive relay and the main negative relay to be disconnected, the VCU sends the APU required power generation power calculated by the vehicle energy management module to the APU for execution. It should be noted that at this time, since the vehicle is in an abnormal operating condition, in order to ensure the safety of the vehicle's operation and the safety of its components, it is necessary to control the vehicle's maximum speed to be set at the limp home setting threshold, and the vehicle's total required power is lower than the limp home setting threshold.

[0023] In detail, before the main positive relay is closed, it is still necessary to ensure that the bus current does not exceed the threshold value, so as to prevent the main positive relay from closing when the DC bus current exceeds the threshold value, causing arcing and sparking, which will affect the life of the main positive relay and cause the main positive relay to stick in severe cases.

[0024] After that, the APU runs in the voltage control generation mode. The RCU needs to set the upper limit Utop and lower limit Ubottom of the generator speed range controlled by the GCU in the voltage control mode. The upper limit depends on the upper limit of the working voltage range of the high-voltage system components, and the lower limit depends on the lower limit of the working voltage range of the high-voltage system components. The purpose is to ensure that when the APU runs in the voltage control generation mode, when the generator speed is adjusted, its output voltage changes within a reasonable range, so that the high-voltage components can work normally. For AC motors, the induced electromotive force of each phase of the stator is: E=4.44*N*K*f*ψ, 4.44*N*K is a constant determined by the structure of the motor itself. When the motor is in a stable working state, the resistance voltage division and the induced electromotive force on the stator winding can be ignored, so the terminal voltage can be used to approximately replace the induced electromotive force. From the formula, it can be seen that the magnetic flux is proportional to E / f, so keeping the ratio of E / f unchanged can ensure that the air gap flux ψ remains unchanged, that is, the ratio of the GCU output power supply voltage and the modulation frequency is maintained to make the air gap flux maximum and the ratio remains unchanged. In this way, the generator output torque is maximized under the same current and the efficiency is higher. If the ratio of the power supply voltage and the modulation frequency exceeds the maximum value of the air gap flux, it will cause magnetic circuit saturation, and in severe cases, the motor will be burned. Therefore, in order to keep the air gap flux unchanged, it is required to change the output voltage synchronously during frequency conversion. The output voltage needs to be controlled within the above-mentioned upper limit Utop and lower limit Ubottom, and the corresponding modulation frequency has a corresponding variation range [ftop, fbottom].

[0025] The step S50 comprises the following steps: Step S51, RCU controls APU to enter voltage control mode to maintain constant voltage output; Step S52, the VCU calculates the required APU power generation in real time according to the vehicle energy management strategy and sends it to the RCU for execution; Step S53, the RCU calculates the engine target torque based on the APU power generation power required by the VCU combined with the preset system efficiency and current speed and sends it to the EMS for execution; Step S54, the EMS controls the throttle opening and the fuel injection amount based on the air-fuel ratio target coefficient being 1; Step S55, determining whether the battery fault has disappeared, or the battery charge and discharge capacity is greater than a threshold value, if so, the VCU controls the power consumption of the high-voltage components, and immediately controls the execution of the high-voltage process, if not, repeating the determination; Step S56, the VCU immediately sends to the RCU that the power generation control mode is the speed torque control mode.

[0026] It should be noted that the following steps are provided between step S53 and step S54: 1. When the APU power generation power required by the VCU changes, the APU will obtain the target speed of the generator and the target torque of the engine based on the power decoupling map. After the target speed of the generator changes, the fundamental frequency needs to be calculated based on the characteristics of the voltage control mode; 2. When the operating speed of the generator changes, the GCU output three-phase fundamental frequency is calculated based on the speed, and the power supply voltage keeps changing synchronously, so that the air gap flux is always kept at the maximum value; 3. When the APU switches from the current speed operating point to other speed operating points, in order to ensure that the generator control does not lose step or oscillate, it is necessary to ensure a smooth transition of the speed change. If the step change or speed is too fast, the motor speed will be abnormal; 4. When the GCU controls the speed point switching, a ramp function is added to make the frequency have a smooth and gentle change process, and then the GCU controls the output fundamental frequency according to the power supply frequency corresponding to the new target speed operating condition point; 5. In order to obtain more accurate power generation, it is necessary to conduct bench sweep test on the generator operating condition points in voltage control mode. The dynamometer monitors the engine mechanical power, the power analyzer measures the output electric power, and then calculates the overall efficiency, so as to obtain accurate power generation efficiency at each operating speed point in voltage control mode.

[0027] 6. EMS adopts a throttle opening-based adjustment method for engine torque control. The engine of the APU is a gasoline engine. The target basic throttle opening is obtained by looking up the table for different target torques and current speeds. The final target throttle opening is obtained after correction based on the throttle correction factor. Then, fuel injection control is performed based on the target air-fuel ratio coefficient of 1, and the ignition angle is the optimal ignition angle.

[0028] To judge whether the battery fault has disappeared, after the VCU monitors that the high-level fault reported by the battery has been cured, or monitors that the battery's charge and discharge capabilities are higher than the threshold, the VCU believes that the battery fault has disappeared, or the ambient temperature has risen to the normal range, and the battery's charge and discharge capabilities have been restored. The VCU determines that the APU can perform normal power generation control at this time, and will first control the execution of the high-voltage process to close the main negative relay and the main positive relay. After the relay is closed, it will immediately send a signal to the APU that the power generation control mode is the speed torque control mode. After receiving the signal, the RCU will perform normal speed torque power generation control.

[0029] Regarding the characteristics of the voltage control mode in the above point 2, it is based on the relationship that the motor speed is proportional to the power input frequency n = 60 f (1-s) / p, (where n, f, s, and p represent the speed, input frequency, motor slip, and number of motor poles, respectively). For PMSM, the slip is 0, and the purpose of changing the generator speed is achieved by changing the working power frequency of the generator.

[0030] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above-mentioned concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for controlling power generation of an extended-range electric vehicle, It is characterized in that The following steps are involved: Step S10, power on and initialize, the whole vehicle is ready with high voltage, and then the driver controls the vehicle to drive; Step S20, monitor the battery status in real time through the VCU, and determine whether the APU needs to be started. If yes, send an APU start instruction to the RCU through the VCU, and proceed to the next step. If no, repeat the determination; Step S30, the RCU determines whether the engine is started successfully. If yes, the RCU sends a message to the VCU that the APU is started successfully and proceeds to the next step. If no, the determination is repeated. Step S40: After the APU is successfully started, it will send a startup success flag to the VCU. After receiving the flag, the VCU determines that the APU has been successfully started, and the VCU will send a power generation control mode to the RCU as the voltage control mode; Step S50: The RCU executes a voltage control mode.

2. A method for controlling power generation of an extended-range electric vehicle according to claim 1, It is characterized in that The step S20 comprises the following steps: Step S21, monitoring the fault reported by the battery in real time through the fault monitoring system of the VCU; Step S22, determining whether the battery has a level 4 or level 5 serious fault, if so, sending an APU start instruction to the RCU through the VCU, if not, repeating the determination; Step S23: This step is executed synchronously with step S21, and the battery capacity monitoring system of the VCU monitors the minimum temperature of the battery cell and the charge and discharge capacity of the battery in real time; Step S24, determining whether the peak charging and continuous discharging capabilities of the battery are both lower than the threshold, if so, proceed to the next step, if not, repeat the determination; Step S25, determining whether the available peak discharge of the battery is greater than the power required to start the APU at the current temperature, if so, sending an APU start instruction to the RCU via the VCU, if not, repeating the determination.

3. A method for controlling power generation of an extended-range electric vehicle according to claim 1, It is characterized in that The step S30 comprises the following steps: Step S31, after receiving the start command from the VCU, the RCU sends a speed control command to the GCU; Step S32, the GCU outputs three-phase AC power to drive the PMSM to run and then drive the engine to run; Step S33, determine whether the engine speed is greater than a threshold, if so, the RCU will send an injection command to the EMS, if not, repeat the determination; Step S34, EMS controls the engine fuel injection and ignition; Step S35, the RCU determines whether the engine is started successfully. If so, the RCU sends a message to the VCU to start the APU successfully. If not, the determination is repeated.

4. A method for controlling power generation of an extended-range electric vehicle according to claim 1, It is characterized in that The step S40 comprises the following steps: Step S41, controlling the power consumption of high-voltage accessories through the VCU; Step S42, determine whether the DC bus current is less than a threshold value, if so, the VCU immediately sends a command to disconnect the main positive relay and the main negative relay to the BMS, and proceeds to the next step, if not, continue to determine; Step S43, the BMS controls the battery main positive relay and the main negative relay in the high-voltage circuit to be disconnected; Step S44, the VCU immediately sends a signal to the RCU that the power generation control mode is the voltage control mode.

5. A method for controlling power generation of an extended-range electric vehicle according to claim 1, It is characterized in that The step S50 comprises the following steps: Step S51, RCU controls APU to enter voltage control mode to maintain constant voltage output; Step S52, the VCU calculates the required APU power generation in real time according to the vehicle energy management strategy and sends it to the RCU for execution; Step S53, the RCU calculates the engine target torque based on the APU power generation power required by the VCU combined with the preset system efficiency and current speed and sends it to the EMS for execution; Step S54, the EMS controls the throttle opening and the fuel injection amount based on the air-fuel ratio target coefficient being 1; Step S55, determining whether the battery fault has disappeared, or the battery charge and discharge capacity is greater than a threshold value, if so, the VCU controls the power consumption of the high-voltage components, and immediately controls the execution of the high-voltage process, if not, repeating the determination; Step S56, the VCU immediately sends to the RCU that the power generation control mode is the speed torque control mode.

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