Discharge control method applied to high-voltage electrical system of electric vehicle and ripple signal suppression method thereof

Abstract

The invention provides a discharge control method applied to a high-voltage electrical system of an electric vehicle and a ripple signal suppression method thereof, and the suppression method comprises the steps: controlling an isolated DC-DC converter in a vehicle-mounted charger to be in a working state in the running process of the electric vehicle, therefore, an energy storage unit in the vehicle-mounted charger outputs positive and negative alternating compensation current to the outside, so that a ripple signal generated in the discharging process of the high-voltage electrical system is suppressed. According to the ripple suppression method of the high-voltage electrical system, provided by the invention, in the running process of the electric vehicle, on the basis of absorbing pulse ripples by utilizing the high-voltage direct-current bus capacitor, the isolated DC-DC converter in the vehicle-mounted charger is controlled to be in a working state; and the ripple signal of the input end of the inverter is dynamically compensated again through the energy storage unit in the vehicle-mounted charger, so that the loss and heating of the power battery and the high-voltage direct-current bus capacitor are reduced, the service lives of the power battery and the high-voltage direct-current bus capacitor are prolonged, noise vibration is relieved, and the output torque precision and rotating speed precision of the driving motor are also improved.

Description

Technical Field

[0001] The present invention relates to the field of electric vehicle drive control, and particularly to a discharge control method applied to a high-voltage electrical system of an electric vehicle and a method for suppressing its ripple signal. Background Art

[0002] With the development of electric vehicles, a charging circuit and a discharging circuit are provided in the high-voltage electrical system of the electric vehicle. The power battery provides electrical energy for the drive motor through an inverter, so that the drive motor outputs the required rotational speed and torque; the AC power grid charges the power battery through an on-vehicle charger, where the on-vehicle charger includes an isolated DC-DC converter and a power factor correction unit. During the driving process of the electric vehicle, the on-vehicle charger does not work, and the switching devices in the inverter perform switching operations at a fixed switching frequency and duty cycle, so that the current at the input end of the inverter has a pulse ripple related to the switching frequency. In the related art, a high-voltage DC bus capacitor is provided between the power battery and the inverter to absorb the pulse ripple. Although the pulse ripple is somewhat suppressed, the pulse ripple still exists; due to the impedance characteristics of the high-voltage DC bus capacitor and the power battery, there is also a certain ripple in the voltage across the high-voltage DC bus capacitor.

[0003] During the driving process of the vehicle, the pulse ripple at the output end of the power battery will cause large losses and heat generation, reduce the service life of the power battery, and there is also a situation of resonance with the structure of the power battery, thus generating noise and vibration; a part of the pulse ripple at the input end of the inverter is absorbed by the high-voltage DC bus capacitor, which will cause large losses and heat generation in the high-voltage DC bus capacitor and reduce the service life of the high-voltage DC bus capacitor; the voltage ripple across the high-voltage DC bus capacitor will reduce the torque accuracy and rotational speed accuracy of the drive motor output. If the capacitance value of the high-voltage DC bus capacitor is directly increased, the manufacturing cost will increase.

[0004] Therefore, how to provide a technical solution that can further suppress the ripple signal during the discharge process of the high-voltage electrical system without increasing the manufacturing cost is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the present invention provides a technical solution for suppressing the ripple signal during the discharge process of the high-voltage electrical system of an electric vehicle to solve at least one of the above-mentioned technical problems.

[0006] To achieve the above object and other related objects, the technical solutions provided in the present application are as follows.

[0007] According to the first aspect of the embodiments of the present application, a method for suppressing a ripple signal in a high-voltage electrical system of an electric vehicle is provided, including:

[0008] The high-voltage electrical system includes a power battery, an inverter, a drive motor, an on-vehicle charger, and a controller. The on-vehicle charger includes an isolated DC-DC converter and an energy storage unit. The power battery is respectively connected to the inverter and the isolated DC-DC converter. The output end of the inverter is connected to the drive motor. The controller is respectively connected to the inverter and the isolated DC-DC converter. The suppression method includes:

[0009] When the electric vehicle is in the driving process, control the isolated DC-DC converter to be in the working state. The energy storage unit in the on-vehicle charger responds to the working state and outputs a positive and negative alternating compensation current to suppress the ripple signal at the input end of the inverter by using the compensation current.

[0010] In an embodiment of the present invention, the method for controlling the on-vehicle charger to be in the working state includes: obtaining a predicted electrical signal input to the inverter, the real-time input and output voltage of the isolated DC-DC converter, and the real-time stored voltage of the energy storage unit. Among them, the predicted electrical signal is predicted based on the switching frequency of the inverter, and the electrical signal includes a current component and a voltage component; determining a first control signal according to the predicted electrical signal, the target electrical signal of the inverter, and the compensation current; generating a second control signal according to the real-time stored voltage, the safety threshold voltage of the energy storage unit, and the first control signal; generating a driving pulse signal based on the second control signal and the real-time input and output voltage to drive the isolated DC-DC converter to work.

[0011] In an embodiment of the present invention, the predicted electrical signal includes a predicted voltage signal and a predicted current signal, and the target electrical signal includes a target voltage signal and a target current signal. Determining a first control signal according to the predicted electrical signal, the target electrical signal, and the compensation current includes: determining an initial voltage compensation signal according to the predicted voltage signal and the target voltage signal, and dynamically adjusting the initial voltage compensation signal according to the compensation current to obtain a voltage control signal; determining an initial current compensation signal according to the predicted current signal and the target current signal, and dynamically adjusting the initial current compensation signal according to the compensation current to obtain a current control signal; performing a proportional operation on the voltage control signal and the current control signal according to a preset ripple compensation mapping relationship to obtain the first control signal; where the ripple compensation mapping relationship is the compensation ratio parameter of voltage and current of different high-voltage electrical systems.

[0012] In an embodiment of the present invention, determining an initial voltage compensation signal according to the predicted voltage signal and the target voltage signal, and dynamically adjusting the initial voltage compensation signal according to the compensation current to obtain a voltage control signal includes: calculating an initial compensation voltage according to the predicted voltage signal and the target voltage signal; determining a compensation voltage based on the compensation current, and determining a voltage compensation error value based on the compensation voltage and the initial compensation voltage; using the voltage compensation error value to correct and adjust the initial compensation voltage to reduce the voltage compensation error value, and generating the voltage control signal.

[0013] In an embodiment of the present invention, generating a second control signal according to the real-time stored voltage, the safety threshold voltage of the energy storage unit, and the first control signal includes: generating a lower limit adjustment signal and an upper limit adjustment signal related to the real-time stored voltage, where the lower limit adjustment signal is used to constrain the voltage of the energy storage unit not to be lower than the lower limit of the safety threshold voltage, and the upper limit adjustment signal is used to constrain the voltage of the energy storage unit not to be higher than the upper limit of the safety threshold voltage; performing an extreme value selection on the upper limit adjustment signal, the lower limit adjustment signal, and the first control signal to obtain the second control signal.

[0014] In an embodiment of the present invention, the safety threshold voltage includes a voltage lower limit threshold and a voltage upper limit threshold. Generating a lower limit adjustment signal and an upper limit adjustment signal corresponding to the real-time stored voltage and the safety threshold voltage includes: calculating a lower limit difference between the real-time stored voltage and the voltage lower limit threshold, and performing a proportional-integral control adjustment on the lower limit difference to obtain the lower limit adjustment signal; calculating an upper limit difference between the real-time stored voltage and the voltage upper limit threshold, and performing a proportional-integral control adjustment on the upper limit difference to obtain the upper limit adjustment signal.

[0015] In an embodiment of the present invention, performing an extreme value selection on the upper limit adjustment signal, the lower limit adjustment signal, and the first control signal to obtain the second control signal includes: comparing the first control signal with the lower limit adjustment signal, and selecting the smaller value of the two as a first intermediate signal; comparing the first intermediate signal with the upper limit adjustment signal, and selecting the larger value of the two as the second control signal.

[0016] In an embodiment of the present invention, the high-voltage electrical system further includes an additional energy storage device, the additional energy storage device is arranged at the AC input end of the on-vehicle charger, and the suppression method further includes: when the real-time stored voltage exceeds the voltage upper limit threshold, controlling the power factor correction unit in the on-vehicle charger to work, so as to absorb the ripple signal through the additional energy storage device.

[0017] According to the second aspect of the embodiments of the present application, a discharge control method applied to the high-voltage electrical system of an electric vehicle is further provided. The discharge control method includes the ripple signal suppression method applied to the high-voltage electrical system of an electric vehicle as described above, and includes: obtaining a vehicle driving instruction; pre-charging an energy storage unit in an on-vehicle charger according to the vehicle driving instruction; controlling a power battery to provide power to a drive motor based on the vehicle driving instruction, and controlling an isolated DC-DC converter to be in a working state to generate a positive and negative alternating compensation current to suppress the ripple signal of an input inverter.

[0018] In another embodiment of the present invention, pre-charging the energy storage unit in the on-vehicle charger according to the vehicle driving instruction includes: generating a charging pulse signal according to the vehicle driving instruction, and controlling the isolated DC-DC converter to provide a charging current to the energy storage unit based on the charging pulse signal; charging the energy storage unit through the power battery until the real-time storage voltage of the energy storage unit is within a safety threshold voltage, and completing the pre-charging of the energy storage unit.

[0019] The present application provides a discharge control method applied to the high-voltage electrical system of an electric vehicle and a method for suppressing its ripple signal. The method for suppressing the ripple signal includes: during the driving process of the electric vehicle, controlling the isolated DC-DC converter in the on-vehicle charger to be in a working state, so that the energy storage unit in the on-vehicle charger outputs a positive and negative alternating compensation current, thereby suppressing the ripple signal generated during the discharge process of the high-voltage electrical system. For the ripple suppression method of the high-voltage electrical system provided by the present application, during the driving process of the electric vehicle, on the basis of using a high-voltage DC bus capacitor to absorb pulse ripples, controlling the isolated DC-DC converter in the on-vehicle charger to be in a working state, and dynamically compensating the ripple signal at the input end of the inverter again through the energy storage unit in the on-vehicle charger, thereby reducing the loss and heat generation of the power battery and the high-voltage bus capacitor, extending the service life of both, alleviating noise and vibration, and also improving the torque accuracy and speed accuracy of the drive motor output.

[0020] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present invention. Description of the Drawings

[0021] The drawings here are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present invention, and are used together with the specification to explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0022] Figure 1is a block diagram of a high-voltage electrical system in the prior art;

[0023] Figure 2 is a schematic curve diagram of voltage ripple and current ripple existing on the input side of an inverter in the prior art;

[0024] Figure 3 is a structural block diagram of a high-voltage electrical system shown in an exemplary embodiment of the present invention;

[0025] Figure 4 is a specific structural schematic diagram of a controller shown in an exemplary embodiment of the present invention;

[0026] Figure 5 is a structural block diagram of adding an accessory energy storage device in a high-voltage electrical system shown in an exemplary embodiment of the present invention;

[0027] Figure 6 is a schematic flow diagram of a discharge control method for a high-voltage electrical system shown in an exemplary embodiment of the present invention;

[0028] Reference numerals: 310 - power battery; 320 - high-voltage DC bus capacitor; 330 - inverter; 340 - drive motor; 350 - controller; 360 - on-vehicle charger; 361 - isolated DC-DC converter; 362 - energy storage unit; 370 - AC power grid; 380 - additional energy storage device. Detailed implementation manners

[0029] The following will describe the implementation manners of the present invention with reference to the drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for explaining the present invention, rather than for limiting the protection scope of the present invention.

[0030] It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the drawings, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0031] In the following description, numerous details are explored to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0032] The PI controller (Proportional-Integral Controller) is a classic feedback control algorithm widely used in industrial automation, process control, motor drive and other fields. It combines the proportional (P) and integral (I) control actions to achieve stable control of the system and eliminate the steady-state error.

[0033] The PR controller (Proportional-Resonant Controller) adds a resonant (R) control on the basis of the PI controller and is mainly used to track or suppress AC signals (such as sine waves) of specific frequencies.

[0034] The PID controller (Proportional-Integral-Derivative Controller) adds a derivative (D) control on the basis of PI to further improve the dynamic response and suppress overshoot.

[0035] Model Predictive Control (MPC) is an advanced control strategy based on models and rolling optimization, which generates control commands by predicting future states and solving optimization problems. The control principle of model predictive control includes: a prediction model (using the system mathematical model to predict future outputs), an optimization solution (minimizing the objective function under constraint conditions), and a rolling time domain (only executing the optimal control quantity at the current moment and re-optimizing in the next cycle).

[0036] With the development of electric vehicles, a charging circuit and a discharging circuit are provided in the high-voltage electrical system of the electric vehicle. As Figure 1 shown, the power battery is connected to one end of the inverter, and the other end of the inverter is connected to the drive motor, forming a discharging circuit; the power battery is also connected to the DC end of the on-vehicle charger, and the AC end of the on-vehicle charger is connected to the AC power grid. The power battery provides electrical energy for the drive motor through the inverter, so that the drive motor outputs the required speed and torque; the AC power grid charges the power battery through the on-vehicle charger, where the on-vehicle charger includes an isolated DC-DC converter, an intermediate bus capacitor, a power factor correction unit (Power Factor Correction, PFC), etc.

[0037] During the driving process of an electric vehicle, when the on-vehicle charger is not working and the inverter is working, it will control the switching devices inside it to perform switching actions at a fixed switching frequency and duty cycle according to the required speed and torque of the drive motor, so that the current I at the input end of the inverter inv has pulse ripples consistent with the switching frequency and with a large amplitude (up to several hundred amperes). In related technologies, as Figure 1 shown, a high-voltage DC bus capacitor (with a general capacitance of 0.5 - 2 mF) is set between the power battery and the inverter to absorb this pulse ripple, so that the current ripple I output by the power battery bat is somewhat suppressed, but the current ripple I bat still exists; further, due to the impedance characteristics of the high-voltage DC bus capacitor and the power battery, there is also a certain voltage ripple at both ends of the high-voltage DC bus capacitor U inv .

[0038] As Figure 2 shown, during the driving process of the vehicle, the current pulse ripple I at the output end of the power battery bat will generate relatively large losses and heat, reducing the service life of the power battery. The current pulse ripple I bat may also resonate with the structure of the power battery, thus generating noise and vibration; a part of the current pulse ripple I at the input end of the inverter inv is absorbed by the high-voltage DC bus capacitor, which will cause the high-voltage DC bus capacitor to generate relatively large losses and heat, reducing the service life of the high-voltage DC bus capacitor; the voltage ripple U at both ends of the high-voltage DC bus capacitor bat will reduce the torque accuracy and speed accuracy of the drive motor output. If the capacitance value of the high-voltage DC bus capacitor is directly increased, it will lead to an increase in manufacturing cost.

[0039] To solve the above problems, the present application provides a suppression scheme for ripple signals in the high-voltage electrical system of an electric vehicle. When the electric vehicle is in the driving process, this suppression scheme controls the isolated DC-DC converter in the on-vehicle charger to be in the working state, so that the energy storage unit in the on-vehicle charger outputs positive and negative alternating compensation currents, and suppresses the ripple signals between the power battery and the inverter through this compensation current.

[0040] In the first aspect, the present application provides a method for suppressing ripple signals in the high-voltage electrical system of an electric vehicle, as Figure 3As shown in the figure, the high-voltage electrical system includes a power battery 310, an inverter 330, a drive motor 340, an on-vehicle charger 360, and a controller 350. The on-vehicle charger 360 includes an isolated DC-DC converter 361 and an energy storage unit 362. The power battery 310 is respectively connected to the inverter 330 and the isolated DC-DC converter 361. The output end of the inverter 330 is connected to the drive motor 340. The controller 350 is respectively connected to the inverter 330 and the isolated DC-DC converter 361. The suppression method includes:

[0041] When the electric vehicle is in the driving process, control the isolated DC-DC converter 361 to be in the working state, and the energy storage unit 362 in the on-vehicle charger 360 outputs a positive and negative alternating compensation current I in response to this working state. obc to utilize the compensation current I obc to suppress the ripple signal at the input end of the inverter 330.

[0042] Specifically, as Figure 3 shown in the figure, the high-voltage electrical system includes a power battery 310, a high-voltage DC bus capacitor 320, an inverter 330, a drive motor 340, a controller 350, an on-vehicle charger 360, an AC power grid 370, and an AC relay K1. The on-vehicle charger includes an isolated DC-DC converter 361, an energy storage unit 362, and a power factor correction unit 363 (Power Factor Correction, PFC). The power battery 310 is respectively connected to the inverter 330 and the isolated DC-DC converter 361. The output end of the inverter 330 is connected to the drive motor 340. A high-voltage bus capacitor 320 is arranged between the power battery 310 and the inverter 330. The high-voltage bus capacitor 320 is used to absorb part of the ripple signal. The controller 350 is respectively connected to the inverter 330 and the isolated DC-DC converter 361. The isolated DC-DC converter 361 is also connected to the energy storage unit 362. The energy storage unit 362 is also connected to the power factor correction unit 363. The AC end of the power factor correction unit 363 is connected to the AC power grid 370 through the AC relay K1.

[0043] It should be noted that the controller can be a single control unit or multiple control units, which are used to control the inverter 310 and the isolated DC-DC converter 361 respectively; the energy storage unit 362 is an intermediate bus capacitor arranged between the isolated DC-DC converter 361 and the power factor correction unit 363.

[0044] When the electric vehicle is in the driving process, the power battery 310 supplies electrical energy to the drive motor 340 through the inverter 330, so that the drive motor 340 outputs the required torque and speed; the controller 350 generates a pulse signal according to the working information output by the inverter 330, and inputs the pulse signal into the isolated DC-DC converter 361 in the on-vehicle charger 360 to control the operation of the isolated DC-DC converter 361, and the energy storage unit 362 responds to the working state of the isolated DC-DC converter 361 to generate a positive and negative alternating compensation current I obc , so as to pass the compensation current I obc to suppress the ripple signal at the input side of the inverter 330, improve the accuracy of the output torque and speed of the drive motor 340, and extend the service life of the high-voltage electrical system.

[0045] Specifically, the method for controlling the isolated DC-DC converter to be in the working state includes: obtaining the predicted electrical signal input to the inverter, the real-time input and output voltages of the isolated DC-DC converter, and the real-time stored voltage of the energy storage unit. Among them, the predicted electrical signal is predicted based on the switching frequency of the inverter, and the electrical signal includes a current component and a voltage component; determining a first control signal according to the predicted electrical signal, the target electrical signal of the inverter and the compensation current; generating a second control signal according to the real-time stored voltage, the safety threshold voltage of the energy storage unit and the first control signal; generating a drive pulse signal based on the second control signal and the real-time input and output voltages to drive the isolated DC-DC converter to work. Specifically, as Figure 3 shown, the first input and output terminal of the isolated DC-DC converter 361 in the on-vehicle charger 360 is connected to the input and output terminal of the power battery 310, the second input and output terminal of the isolated DC-DC converter 361 is connected to the pure energy unit 362, and the controller 350 obtains the switching frequency and duty ratio of the inverter 330, predicts the real-time predicted voltage value and real-time predicted current value at the input terminal of the input inverter 330 according to the switching frequency, and also obtains the real-time sampled voltage and real-time sampled current at the input and output terminals of the isolated DC-DC converter 361 in real time, and obtains the real-time stored voltage of the energy storage unit 362. Determine the first control signal according to the real-time predicted voltage value and real-time predicted current value, target voltage value and target current value at the input terminal of the inverter 330, and the compensation current; generate the second control signal based on the real-time stored voltage, the safety threshold voltage of the energy storage unit 362 and the first control signal; as Figure 4 shown, through the second control signal and the real-time sampled voltage (U dc-in , U dc-out)Perform isolated DC-DC modulation to determine parameters such as the switching frequency, internal phase shift angle, and external phase shift angle in the isolated DC-DC converter, and generate a drive pulse signal according to the above-mentioned parameters such as the switching frequency, internal phase shift angle, and external phase shift angle, so as to control the operation of the isolated DC-DC converter 361 by using the drive pulse signal.

[0046] Specifically, as Figure 4 shown, the predicted electrical signal includes the predicted voltage signal U InvPred and the predicted current signal i InvPred . The target electrical signal includes the target voltage signal and the target current signal. The steps of determining the first control signal according to the predicted electrical signal, the target electrical signal, and the compensation current include: calculating the initial voltage compensation signal U InvPred based on the predicted voltage signal U ObcDes and the target voltage signal, and dynamically adjusting the initial voltage compensation signal U Obc according to the compensation voltage U obc corresponding to the compensation current I ObcDes to obtain the voltage control signal; determining the initial current compensation signal I InvPred based on the predicted current signal i ObcDes and the target current signal, and dynamically adjusting the initial current compensation signal according to the compensation current I Obc to obtain the current control signal; querying the ripple compensation mapping relationship of the current high-voltage electrical system during vehicle driving, that is, the compensation parameter ratio between voltage and current, and performing a proportional operation on the voltage control signal and the current control signal through the compensation ratio parameter to obtain the first control signal; where the ripple compensation mapping relationship is the compensation ratio parameter between the voltage and current of different high-voltage electrical systems; in extreme cases, one of the voltage or current compensation ratios can be 0, canceling the corresponding compensation parameter.

[0047] More specifically, as Figure 4 shown, determining the initial voltage compensation signal according to the predicted voltage signal and the target voltage signal, and dynamically adjusting the initial voltage compensation signal according to the compensation current to obtain the voltage control signal, includes: calculating the initial compensation voltage according to the predicted voltage signal and the target voltage signal; determining the compensation voltage based on the compensation current, and determining the voltage compensation error value based on the compensation voltage and the initial compensation voltage; using the voltage compensation error value to adjust the initial compensation voltage to reduce the voltage compensation error value and generate the voltage control signal. Specifically, as Figure 4 shown in the voltage compensation loop in InvPred , subtracting the predicted voltage signal U ObcDes from the target voltage signal to obtain the initial compensation voltage U obc , determining the compensation voltage U obc for the high-voltage DC bus capacitor according to the compensation current i obc , and calculating the initial compensation voltage UObcDes The difference from the actual compensation voltage U obc results in a voltage compensation error value U linErr . Using the voltage compensation error value U obcErr through a PI controller + PR controller to perform dynamic loop regulation on the initial voltage compensation value U ObcDes to obtain a voltage control signal.

[0048] More specifically, as shown in the current compensation loop of Figure 4 , subtracting the predicted current signal I InvPred from the target current signal to obtain an initial compensation current i ObcDes . Calculating the difference between the initial compensation current i ObcDes and the actual compensation current i obc results in a current compensation error value i obcDes . Using the current compensation error value i obcErr through a PI controller + PR controller to perform dynamic loop regulation on the initial current compensation value i ObcDes to obtain a current control signal.

[0049] It should be emphasized that the PI controller and PR controller can be replaced by other controllers, such as a PID controller, a model predictive controller, etc.

[0050] Specifically, generating a second control signal according to the real-time stored voltage, the safety threshold voltage of the energy storage unit, and the first control signal, including: generating a lower limit adjustment signal and an upper limit adjustment signal related to the real-time stored voltage, where the lower limit adjustment signal is used to constrain the voltage of the energy storage unit not to be lower than the lower limit of the safety threshold voltage, and the upper limit adjustment signal is used to constrain the voltage of the energy storage unit not to be higher than the upper limit of the safety threshold voltage; performing an extreme value selection on the upper limit adjustment signal, the lower limit adjustment signal, and the first control signal to obtain the second control signal. Specifically, as shown in Figure 4 , generating an upper limit adjustment signal and a lower limit adjustment signal according to the real-time stored voltage U link of the energy storage unit, the safety threshold voltage (U LinkMinDes , U LinkMaxDes ). The upper limit adjustment signal controls the compensation current so that during the process of suppressing the ripple signal, the real-time stored voltage U link does not exceed the upper voltage threshold U LinkMaxDes of the energy storage unit, and the lower limit adjustment signal controls the compensation current so that during the process of suppressing the ripple signal, the real-time stored voltage U link is not lower than the lower voltage threshold U LinkMinDes of the energy storage unit; obtaining the second control signal by performing an extreme value selection on the upper limit adjustment signal, the lower limit adjustment signal, and the first control signal.

[0051] Specifically, the safety threshold voltage includes a lower voltage threshold and an upper voltage threshold. Generating a lower adjustment signal and an upper adjustment signal corresponding to the real-time storage voltage and the safety threshold voltage includes: calculating a lower difference between the real-time storage voltage and the lower voltage threshold, and performing proportional-integral control adjustment on the lower difference to obtain a lower adjustment signal; calculating an upper difference between the real-time storage voltage and the upper voltage threshold, and performing proportional-integral control adjustment on the upper difference to obtain an upper adjustment signal. As Figure 4 shown, in the intermediate bus voltage limiting loop, subtracting the real-time storage voltage U link from the lower voltage threshold U LinkMinDes to obtain a lower difference U LinkErr1 , and performing proportional-integral adjustment on the lower difference U LinkErr1 through a PI controller to obtain a lower adjustment signal; subtracting the real-time storage voltage U link from the upper voltage threshold U LinkMaxDes to obtain an upper difference U LinkErr2 , and performing proportional-integral adjustment on the upper difference U LinkErr2 through a PI controller to obtain an upper adjustment signal.

[0052] More specifically, performing an extreme value selection on the upper adjustment signal, the lower adjustment signal, and the first control signal to obtain a second control signal includes: comparing the first control signal with the lower adjustment signal, and selecting the smaller value of the two as the first intermediate signal; comparing the first intermediate signal with the upper adjustment signal, and selecting the larger value of the two as the second control signal. Specifically, as Figure 4 shown, after obtaining the lower adjustment signal, select the minimum value of the lower difference signal and the first control signal as the first intermediate signal, and then compare the first intermediate signal with the upper adjustment signal, and select the maximum value of the two as the second control signal.

[0053] Exemplarily, taking the intermediate bus voltage limiting loop as an example, the safety threshold voltage of the energy storage unit is 2V to 50V, the first control signal is 1. If the real-time storage voltage U link is 20V, subtract the real-time storage voltage U link 20V from the lower voltage threshold U LinkMinDes 2V, the difference is 18, and then through the proportional-integral of the PI controller, the lower adjustment signal is 100. Select the smaller value of the lower adjustment signal 100 and the first control signal 1 as the first intermediate signal, and the first intermediate signal is 1; subtract the real-time storage voltage U link 20V from the upper voltage threshold U LinkMaxDesThe difference between 50V and a certain value is -30. After passing through the proportional-integral of the PI controller, the upper limit adjustment signal obtained is -260. The larger value between the upper limit adjustment signal -260 and the first intermediate signal 1 is selected as the second control signal, and the second control signal is 1. Thus, it can be seen that when the real-time stored voltage is between the safety threshold voltages, no voltage limit adjustment is performed on the compensation current.

[0054] Similarly, the safety threshold voltage of the energy storage unit is 2V to 50V, and the first control signal is 1. If the real-time stored voltage U link is 1V, subtract the real-time stored voltage U link 1V from the lower voltage threshold U LinkMinDes 2V. The difference is -1. After passing through the proportional-integral of the PI controller, the lower limit adjustment signal obtained is -20. The smaller value between the lower limit adjustment signal -20 and the first control signal 1 is selected as the first intermediate signal, and the first intermediate signal is -20. Subtract the real-time stored voltage U link 1V from the upper voltage threshold U LinkMaxDes 50V. The difference is -49. After passing through the proportional-integral of the PI controller, the upper limit adjustment signal obtained is -500. The larger value between the upper limit adjustment signal -500 and the first intermediate signal -20 is selected as the second control signal, and the second control signal is -20. When the second control signal is negative, it is necessary to reduce the value of the compensation current and charge the energy storage unit in a timely manner to ensure that the real-time stored voltage U link is within the safety threshold voltage.

[0055] The safety threshold voltage of the energy storage unit is 2V to 50V, and the first control signal is 1. If the real-time stored voltage U link is 55V, subtract the real-time stored voltage U link 55V from the lower voltage threshold U LinkMinDes 2V. The difference is 53. After passing through the proportional-integral of the PI controller, the lower limit adjustment signal obtained is 600. The smaller value between the lower limit adjustment signal 600 and the first control signal 1 is selected as the first intermediate signal, and the first intermediate signal is 1. Subtract the real-time stored voltage U link 55V from the upper voltage threshold U LinkMaxDes 50V. The difference is 5. After passing through the proportional-integral of the PI controller, the upper limit adjustment signal obtained is 200. The larger value between the upper limit adjustment signal 200 and the first intermediate signal 1 is selected as the second control signal, and the second control signal is 200. When the second control signal is positive, it is necessary to increase the value of the compensation current and discharge the energy storage unit in a timely manner to ensure that the real-time stored voltage U link is within the safety threshold voltage.

[0056] Specifically, the high-voltage electrical system further includes an additional energy storage device, which is disposed at the input end of the alternating current of the on-vehicle charger. The suppression method further includes: when the real-time stored voltage exceeds the voltage upper limit threshold, controlling the power factor correction unit in the on-vehicle charger to operate, so as to absorb the ripple signal through the additional energy storage device. Specifically, as Figure 5 shown, an additional energy storage device 380 is disposed at the AC end of the on-vehicle charger 360. The controller 350 is also connected to the power factor correction unit 363 in the on-vehicle charger 360. During the driving process of the electric vehicle, the AC relay K1 is in the off state. When the real-time stored voltage U link in the energy storage unit 362 is greater than the voltage upper limit threshold U LinkMaxDes , a drive signal is sent to the power factor correction unit 363 in the on-vehicle charger 360 through the controller 350 to drive the power factor correction unit 363 in the on-vehicle charger 360 to operate, and the ripple signal on the discharge loop of the high-voltage electrical system is absorbed through the additional energy storage device 380.

[0057] It should be emphasized that, as Figure 5 shown, a switch relay K2 is disposed on the connection branch between the on-vehicle charger 360 and the additional energy storage device 380. The first end of the switch relay K2 is connected to the common end of the AC relay K1 and the power factor correction unit 363, the second end of the switch relay K2 is connected to the first input / output end of the additional energy storage device 380, and the second input / output end of the additional energy storage device 380 is connected to the common end of the power factor correction unit 363 and the AC power grid 370. When the additional energy storage device 380 is in the working state, the switch relay K2 is first closed; when the additional energy storage device 380 does not need to work, the switch collector K2 is controlled to be disconnected.

[0058] In a second aspect, the present application further provides a discharge control method applied to the high-voltage electrical system of an electric vehicle. The discharge control method controls the operation of the isolated DC-DC converter based on the ripple signal suppression method applied to the high-voltage electrical system of the electric vehicle as described above. As Figure 6 shown, the discharge control method at least includes steps 610 to 630:

[0059] S610. Obtain a vehicle driving instruction.

[0060] The controller 350 receives the vehicle driving instruction sent by the electric vehicle.

[0061] S620. Pre-charge the energy storage unit in the on-vehicle charger according to the vehicle driving instruction.

[0062] Specifically, the process of the controller 350 pre-charging the energy storage unit 361 in the on-vehicle charger 360 according to the vehicle driving instruction includes: generating a charging pulse signal according to the vehicle driving instruction, and sending the charging pulse signal to the isolated DC-DC converter 361 in the on-vehicle charger 360, so that the isolated DC-DC converter 361 provides a charging current to the energy storage unit 362, and charging the energy storage unit 362 through the power battery 310 until the real-time storage voltage U link of the energy storage unit 362 is within the safety threshold voltage, and the pre-charging of the energy storage unit 362 is completed.

[0063] S630. Based on the vehicle driving instruction, control the power battery to provide power for the drive motor, and control the isolated DC-DC converter to be in the working state to generate a positive and negative alternating compensation current to suppress the ripple signal of the input inverter.

[0064] After the pre-charging of the energy storage unit is completed, the controller 350 generates a driving signal for the switching device of the inverter according to the vehicle driving signal. The power battery 310 provides electrical energy for the drive power 340, so that the power battery 310 outputs the required torque and speed, and generates a pulse driving signal for controlling the isolated DC-DC converter 361 according to the working information of the inverter 330. The isolated DC-DC converter 361 works, so that the energy storage unit 362 outputs a positive and negative alternating compensation current, thereby suppressing the ripple signal of the input inverter 330.

[0065] Specifically, the discharge control method further includes: when the controller 350 receives the vehicle stop instruction, the controller 350 generates a discharge pulse signal according to the vehicle stop instruction, and controls the energy storage unit 362 to release the stored electrical energy to the power battery 310 side for storage through the discharge pulse signal, so as to save electrical energy.

[0066] The present application provides a discharge control method for an electric vehicle high-voltage electrical system and a method for suppressing its ripple signal. The method for suppressing the ripple signal includes: during the driving process of the electric vehicle, controlling the isolated DC-DC converter in the on-vehicle charger to be in a working state, so that the energy storage unit in the on-vehicle charger responds to this working state and outputs a positive and negative alternating compensation current, thereby suppressing the ripple signal generated during the discharge process of the high-voltage electrical system. It can not only control the real-time voltage of the energy storage unit, but also absorb the excess ripple through an additional energy storage device when the upper voltage threshold of the energy storage unit is exceeded. For the ripple suppression method of the high-voltage electrical system provided by the present application, during the driving process of the electric vehicle, on the basis of using the high-voltage DC bus capacitor to absorb the pulse ripple, the isolated DC-DC converter in the on-vehicle charger is controlled to be in a working state, and the ripple signal at the input end of the inverter is dynamically compensated again through the energy storage unit in the on-vehicle charger, thereby reducing the loss and heat generation of the power battery and the high-voltage bus capacitor, prolonging the service life of both, alleviating noise and vibration, and also improving the torque accuracy and speed accuracy of the drive motor output, and enhancing the ripple signal suppression ability of the high-voltage electrical system.

[0067] The above embodiments are only used to exemplarily illustrate the principles and effects of the present invention, rather than to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for suppressing ripple signals in a high-voltage electrical system of an electric vehicle, characterized in that: The high-voltage electrical system includes a power battery, an inverter, a drive motor, an on-board charger, and a controller. The on-board charger includes an isolated DC-DC converter and an energy storage unit. The power battery is connected to the inverter and the isolated DC-DC converter respectively. The output terminal of the inverter is connected to the drive motor. The controller is connected to the inverter and the isolated DC-DC converter respectively. The suppression method includes: When the electric vehicle is in the driving process, the isolated DC-DC converter is controlled to be in a working state, and the energy storage unit in the on-board charger outputs a positive and negative alternating compensation current to the outside in response to the working state, so as to utilize the compensation current to suppress the ripple signal at the input end of the inverter.

2. The method for suppressing ripple signals in a high voltage electrical system of an electric vehicle according to claim 1, characterized in that: The method of controlling the isolated DC-DC converter to be in a working state includes: Acquire a predicted electrical signal input to the inverter, a real-time input and output voltage of the isolated DC-DC converter, and a real-time storage voltage of the energy storage unit, wherein the predicted electrical signal is predicted based on the switching frequency of the inverter, and the electrical signal includes a current component and a voltage component; Determining a first control signal according to the predicted electrical signal, the target electrical signal of the inverter and the compensation current; Generate a second control signal according to the real-time storage voltage, the safety threshold voltage of the energy storage unit and the first control signal; A driving pulse signal is generated based on the second control signal and the real-time input and output voltage to drive the isolated DC-DC converter to operate.

3. The method for suppressing ripple signals in a high voltage electrical system of an electric vehicle according to claim 2, characterized in that: The predicted electrical signal includes a predicted voltage signal and a predicted current signal, the target electrical signal includes a target voltage signal and a target current signal, and determining a first control signal according to the predicted electrical signal, the target electrical signal and the compensation current includes: determining an initial voltage compensation signal according to the predicted voltage signal and the target voltage signal, and dynamically adjusting the initial voltage compensation signal according to the compensation current to obtain a voltage control signal; determining an initial current compensation signal according to the predicted current signal and the target current signal, and dynamically adjusting the initial current compensation signal according to the compensation current to obtain a current control signal; Performing a proportional operation on the voltage control signal and the current control signal according to a preset ripple compensation mapping relationship to obtain the first control signal; The ripple compensation mapping relationship is the compensation ratio parameters of voltage and current of different high-voltage electrical systems.

4. The method for suppressing ripple signals in a high voltage electrical system of an electric vehicle according to claim 3, characterized in that: Determining an initial voltage compensation signal according to the predicted voltage signal and the target voltage signal, and dynamically adjusting the initial voltage compensation signal according to the compensation current to obtain a voltage control signal, including: Calculating an initial compensation voltage according to the predicted voltage signal and the target voltage signal; determining a compensation voltage based on the compensation current, and determining a voltage compensation error value based on the compensation voltage and the initial compensation voltage; The initial compensation voltage is corrected and adjusted using the voltage compensation error value to reduce the voltage compensation error value and generate the voltage control signal.

5. The method for suppressing ripple signals in a high voltage electrical system of an electric vehicle according to claim 2, characterized in that: Generating a second control signal according to the real-time storage voltage, the safety threshold voltage of the energy storage unit and the first control signal includes: Generate a lower limit adjustment signal and an upper limit adjustment signal related to the real-time storage voltage, wherein the lower limit adjustment signal is used to constrain the voltage of the energy storage unit to not be lower than the lower limit of the safety threshold voltage, and the upper limit adjustment signal is used to constrain the voltage of the energy storage unit to not be higher than the upper limit of the safety threshold voltage; The upper limit adjustment signal, the lower limit adjustment signal and the first control signal are subjected to extreme value selection to obtain the second control signal.

6. The method for suppressing ripple signals in a high voltage electrical system of an electric vehicle according to claim 5, characterized in that: The safety threshold voltage includes a voltage lower threshold and a voltage upper threshold, and generating a lower limit adjustment signal and an upper limit adjustment signal reflecting that the real-time storage voltage corresponds to the safety threshold voltage includes: Calculating a lower limit difference between the real-time stored voltage and the voltage lower limit threshold, performing proportional integral control adjustment on the lower limit difference, and obtaining the lower limit adjustment signal; An upper limit difference between the real-time stored voltage and the voltage upper limit threshold is calculated, and proportional integral control is performed on the upper limit difference to obtain the upper limit adjustment signal.

7. The method for suppressing ripple signals in a high voltage electrical system of an electric vehicle according to claim 5, characterized in that: The upper limit adjustment signal, the lower limit adjustment signal and the first control signal are subjected to extreme value selection to obtain the second control signal, including: Compare the first control signal with the lower limit adjustment signal, and select the smaller value between the two as the first intermediate signal; The first intermediate signal is compared with the upper limit adjustment signal, and the larger value of the two is selected as the second control signal.

8. The method for suppressing ripple signals in a high voltage electrical system of an electric vehicle according to claim 6, characterized in that: The high-voltage electrical system further includes an additional energy storage device, which is disposed at an input end of the AC power of the on-board charger, and the suppression method further includes: When the real-time storage voltage exceeds the voltage upper limit threshold, the power factor correction unit in the on-board charger is controlled to operate so as to absorb the ripple signal through the additional energy storage device.

9. A discharge control method applied to a high-voltage electrical system of an electric vehicle, the discharge control method comprising the method for suppressing a ripple signal applied to a high-voltage electrical system of an electric vehicle as claimed in any one of claims 1 to 8, comprising: Obtain vehicle driving instructions; pre-charging the energy storage unit in the on-board charger according to the vehicle driving instruction; Based on the vehicle driving instruction, the power battery is controlled to provide power for the drive motor, and the isolated DC-DC converter is controlled to be in a working state to generate a positive and negative alternating compensation current to suppress the ripple signal of the input inverter.

10. The discharge control method applied to the high voltage electrical system of an electric vehicle according to claim 9, characterized in that: Pre-charging the energy storage unit in the on-board charger according to the vehicle driving instruction includes: generating a charging pulse signal according to the vehicle driving instruction, and controlling the isolated DC-DC converter to provide a charging current to the energy storage unit based on the charging pulse signal; The energy storage unit is charged by the power battery until the real-time storage voltage of the energy storage unit is within a safety threshold voltage, thereby completing the pre-charging of the energy storage unit.

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