A pre-charging control system and method for high-voltage direct current charging of electric vehicles

Abstract

The present invention provides a pre-charging control system and method for high-voltage direct current charging of electric vehicles. The pre-charging control system includes a charging circuit, a voltage sampling module and a control module. The charging circuit includes: a power supply; a motor controller; a motor; a capacitor C 2 The voltage sampling module is connected to the two ends of any one of the first phase, the second phase, and the third phase of the motor controller to form a sampling voltage; the control module samples the current of the first winding, the second winding, and the third winding at the middle moment of each sampling cycle to form a first sampling current, a second sampling current, and a third sampling current, and calculates the capacitance C in a single sampling cycle. 2 The voltage change during the sampling period is accumulated until the capacitor C 2 The voltage estimation value is the target voltage value. After adopting the above technical solution, the closed-loop sampling and control of the pre-charge voltage is realized by alternating the charge control and the zero current sampling and iterative convergence method.

Description

Technical Field

[0001] The present invention relates to the field of electric vehicle control, and in particular to a pre-charging control system and method for high-voltage direct current charging of electric vehicles. Background Art

[0002] Electric vehicles are developing rapidly with the general direction of new energy development. Among them, for electric vehicle users, the most concern is the battery life of electric vehicles, that is, they are particularly concerned about the charging efficiency of electric vehicles.

[0003] In order to realize high-voltage DC charging of electric vehicles, a high-voltage DC interface with high-speed charging function can be provided in the built charging station to greatly reduce the charging time. Correspondingly, a charging circuit is provided on the electric vehicle. At the same time, in order to make the high-voltage DC interface identify the electric vehicle, an input side capacitor is provided on the charging circuit. When the boost charging is started, the input side capacitor needs to be pre-charged so that the high-voltage DC interface can be regarded as a battery to be charged. Therefore, the configuration of the input side capacitor and the real-time voltage control of the input side capacitor become the pre-issues of charging electric vehicles.

[0004] In the case of a center-tapped charging circuit for electric vehicles, the capacitor voltage cannot be accurately sampled when the inductor current is present because the motor controller is separated from the capacitor by the motor inductance. If a flying wire is made on the input capacitor through the outside to perform voltage sampling, additional interface costs and safety issues will be incurred.

[0005] Therefore, a new pre-charging control system and method for high-voltage DC charging of electric vehicles is needed, which can solve the problem of inapplicability of the traditional pre-charging closed-loop control loop due to sampling position limitations. Summary of the invention

[0006] In order to overcome the above technical defects, the purpose of the present invention is to provide a pre-charging control system and method for high-voltage DC charging of electric vehicles, which realizes pre-charging voltage closed-loop sampling and control through a method of alternating charge control and zero current sampling and iterative convergence.

[0007] The present invention discloses a pre-charging control system for high-voltage direct current charging of an electric vehicle, which is arranged in the electric vehicle. The pre-charging control system comprises a charging circuit, a voltage sampling module and a control module.

[0008] The charging circuit includes:

[0009] A power source, provided on the charging circuit;

[0010] A motor controller is connected in parallel to both ends of the power supply, including a first phase, a second phase, and a third phase forming a three-phase circuit;

[0011] A motor, comprising a first winding, a second winding and a third winding forming a three-phase winding, wherein the first winding, the second winding and the third winding are connected in parallel to the first phase, the second phase and the third phase respectively;

[0012] A capacitor C2, one end of which is connected to the parallel connection position of the first phase, the second phase and the third phase in the motor, and the other end of which is connected to the motor controller to be connected in parallel to the interface circuit of the charging circuit;

[0013] The voltage sampling module is connected in parallel to two ends of any one of the first phase, the second phase and the third phase to form a sampling voltage;

[0014] The control module samples the current of the first winding, the second winding and the third winding at the middle moment of each sampling cycle of the motor controller to form a first sampling current, a second sampling current and a third sampling current, and calculates the voltage change of the capacitor C2 within a single sampling cycle based on the first sampling current, the second sampling current and the third sampling current;

[0015] The control module continuously accumulates the voltage variation within the sampling period until the voltage estimation value of the capacitor C2 reaches the target voltage value.

[0016] Preferably, the control module samples the current of the first winding, the second winding and the third winding at each valley position of the triangular wave formed in the switching cycle of the three-phase circuit;

[0017] The control module calculates the voltage change of capacitor C2 within a single sampling period based on the following formula:

[0018] Where Δu c2 is the voltage change of capacitor C2, i u 、i v 、i ω are the first sampling current, the second sampling current and the third sampling current of the first phase, the second phase and the third phase respectively, T s is the sampling period;

[0019] The control module continuously accumulates the voltage change within the sampling period based on the following formula:

[0020] u c2 (k) = u c2 (k-1)+Δu c2 (k), k=1, 2, 3, ...;

[0021] where u c2 (k) is the voltage estimation value of the current sampling period, u c2 (k-1) is the voltage estimate of the previous sampling period, Δu c2(k) is the voltage change in the current sampling period.

[0022] Preferably, a target voltage value and an initial voltage value are preset in the control module;

[0023] The motor controller controls the switch tube of the three-phase circuit to open and close periodically to charge the capacitor C2. When the control module calculates that the voltage estimate value of the capacitor C2 is stably close to the initial voltage value, it sends a switch-off instruction to the motor controller to make the first sampling current, the second sampling current and the third sampling current zero, and at this time, the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value;

[0024] The control module calculates a voltage correction value based on the estimated voltage value of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value;

[0025] The control module superimposes the voltage correction value onto the initial voltage value to form a control voltage value, and sends an open-tube instruction to the motor controller. When the control module calculates that the voltage estimation value of the capacitor C2 is stably close to the control voltage value, the control module sends a close-tube instruction to the motor controller to make the first sampling current, the second sampling current and the third sampling current zero, and at this time, the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value;

[0026] The control module updates the voltage correction value based on the estimated voltage value of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value;

[0027] The control module repeatedly iterates the above updating process until the voltage estimation value converges to the target voltage value.

[0028] Preferably, the control module calculates the voltage correction value based on the following formula:

[0029]

[0030] Where ΔV ref (i) is the voltage correction value, V s is the actual voltage value, V q is the voltage estimate, V ref_final is the target voltage value, c1 is the first iteration coefficient, and c2 is the second iteration coefficient;

[0031] The control module calculates the control voltage value based on the following formula:

[0032] V ref (i+1)=V ref (i)+ΔV ref (i)

[0033] Where V ref(i+1) is the control voltage value in the current iteration process, V ref (i) is the control voltage value in the previous iteration process.

[0034] Preferably, an error rate is preset in the control module. When the ratio of the difference between the actual voltage value and the voltage estimation value to the actual voltage value is less than or equal to the error rate, and the voltage estimation value is maintained within an oscillation interval for more than a time threshold, it indicates that the voltage estimation value of capacitor C2 is stably approaching the control voltage value.

[0035] Preferably, the initial voltage value is 60% of the target voltage value;

[0036] When the time of the iteration process is greater than a specified time T, the control module ends the iteration process.

[0037] The present invention also discloses a pre-charging control method for high-voltage direct current charging of an electric vehicle, comprising the following steps:

[0038] A charging circuit, a voltage sampling module and a control module are configured, and the charging circuit includes: a power supply, which is arranged on the charging circuit; a motor controller, which is connected in parallel to both ends of the power supply, including a first phase, a second phase and a third phase forming a three-phase circuit; a motor, which includes a first winding, a second winding and a third winding forming a three-phase winding, and the first winding, the second winding and the third winding are connected in parallel with the first phase, the second phase and the third phase respectively; a capacitor C2, one end of which is connected to the parallel connection position of the first phase, the second phase and the third phase in the motor, and the other end is connected to the motor controller, so as to be connected in parallel to the interface circuit of the charging circuit;

[0039] The voltage sampling module is connected in parallel to two ends of any one of the first phase, the second phase and the third phase to form a sampling voltage;

[0040] The control module samples the current of the first winding, the second winding and the third winding at the middle moment of each sampling cycle of the motor controller to form a first sampling current, a second sampling current and a third sampling current, and calculates the voltage change of the capacitor C2 within a single sampling cycle based on the first sampling current, the second sampling current and the third sampling current;

[0041] The control module continuously accumulates the voltage variation within the sampling period until the voltage estimation value of the capacitor C2 reaches the target voltage value.

[0042] Preferably, the control module samples the current of the first winding, the second winding and the third winding at the middle moment of each sampling cycle of the motor controller to form a first sampling current, a second sampling current and a third sampling current, and the step of calculating the voltage change of the capacitor C2 within a single sampling cycle based on the first sampling current, the second sampling current and the third sampling current includes:

[0043] The control module samples the current of the first winding, the second winding and the third winding at each valley position of the triangular wave formed in the switching cycle of the three-phase circuit;

[0044] The control module calculates the voltage change of capacitor C2 within a single sampling period based on the following formula:

[0045] Where Δu c2 is the voltage change of capacitor C2, i u 、i v 、i ω are the first sampling current, the second sampling current and the third sampling current of the first phase, the second phase and the third phase respectively, T s is the sampling period;

[0046] The control module continuously accumulates the voltage change within the sampling period based on the following formula:

[0047] u c2 (k) = u c2 (k-1)+Δu c2 (k), k=1, 2, 3, ...;

[0048] where u c2 (k) is the voltage estimation value of the current sampling period, u c2 (k-1) is the voltage estimate of the previous sampling period, Δu c2 (k) is the voltage change in the current sampling period.

[0049] Preferably, the pre-charging control method further comprises the following steps:

[0050] A target voltage value and an initial voltage value are preset in the control module;

[0051] The motor controller controls the switch tube of the three-phase circuit to open and close periodically to charge the capacitor C2. When the control module calculates that the voltage estimate value of the capacitor C2 is stably close to the initial voltage value, it sends a switch-off instruction to the motor controller to make the first sampling current, the second sampling current and the third sampling current zero, and at this time, the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value;

[0052] The control module calculates a voltage correction value based on the estimated voltage value of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value;

[0053] The control module superimposes the voltage correction value onto the initial voltage value to form a control voltage value, and sends an open-tube instruction to the motor controller. When the control module calculates that the voltage estimation value of the capacitor C2 is stably close to the control voltage value, the control module sends a close-tube instruction to the motor controller to make the first sampling current, the second sampling current and the third sampling current zero, and at this time, the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value;

[0054] The control module updates the voltage correction value based on the estimated voltage value of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value;

[0055] The control module repeatedly iterates the above updating process until the voltage estimation value converges to the target voltage value.

[0056] Preferably, the control module calculates the voltage correction value based on the following formula:

[0057]

[0058] Where ΔV ref (i) is the voltage correction value, V s is the actual voltage value, V q is the voltage estimate, V ref_final is the target voltage value, c1 is the first iteration coefficient, and c2 is the second iteration coefficient;

[0059] The control module calculates the control voltage value based on the following formula:

[0060] V ref (i+1)=V ref (i)+ΔV ref (i)

[0061] Where V ref (i+1) is the control voltage value in the current iteration process, V ref (i) is the control voltage value in the previous iteration process.

[0062] Compared with the prior art, the above technical solution has the following beneficial effects:

[0063] 1. No external sampling circuit or flying wire is added to achieve closed-loop control, and ultimately the voltage estimation value is accurately controlled at the target pre-charge voltage value;

[0064] 2. Compared with pure open-loop control, better dynamic response characteristics can be obtained, current overshoot and oscillation in the pre-charging process can be reduced, and vehicle jitter can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1A schematic diagram of a circuit topology of a charging circuit in a pre-charging control system in accordance with a preferred embodiment of the present invention;

[0066] Figure 2 A schematic diagram of current sampling in a pre-charging control system in accordance with a preferred embodiment of the present invention;

[0067] Figure 3 A schematic diagram of voltage estimation value-time domain variation in a pre-charging control system in accordance with a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0068] The advantages of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments.

[0069] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0070] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms of "a", "said" and "the" used in this disclosure and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0071] It should be understood that although the terms first, second, third, etc. may be used in the present disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0072] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0073] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0074] In the following description, the suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present invention, and have no specific meanings. Therefore, "module" and "component" can be used interchangeably.

[0075] See also Figure 1 , shows a schematic diagram of the circuit topology of the charging circuit in the pre-charging control system in a preferred embodiment of the present invention. In this embodiment, the pre-charging control system is arranged in an electric vehicle and is used to charge the electric vehicle with high-voltage direct current. Specifically, the pre-charging control system includes a charging circuit, a voltage sampling module and a control module, wherein the charging circuit includes:

[0076] -power supply

[0077] The power source, such as a battery or a battery pack, is a device installed in an electric vehicle to provide electric energy output for the electric vehicle. When the power in the power source is used up, it needs to be charged. Therefore, the power source is installed in a charging circuit, and the charging circuit can be connected to an external charging device, such as a charging pile, a DC charging stand, etc.

[0078] -Motor controller

[0079] The motor controller is usually the nerve center connecting the motor and the battery, which is used to adjust the various performances of the electric vehicle. It not only plays a role in ensuring the basic safety and precise control of the vehicle, but also allows the battery and the motor to exert sufficient strength. In this embodiment, the motor controller is different from the original function (or on the basis of the original function), and adds a configuration for power charging. That is to say, the motor controller in this embodiment is used for both the control of the motor and the charging control of the power supply. Specifically, the motor controller is connected in parallel at both ends of the power supply, and has a first phase, a second phase, and a third phase forming a three-phase circuit, that is, the commonly understood U, V, and W phases (the corresponding relationship between the first phase, the second phase, and the third phase and the U, V, and W phases is not limited in the present invention, and any phase can be regarded as the first phase, and so on). Similarly, in this embodiment, in addition to being used for controlling the motor, the three-phase circuit will also affect the charging state of the charging circuit to the power supply.

[0080] -Motor

[0081] The motor is a device in an electric vehicle that converts electrical energy into mechanical energy. In this embodiment, the motor includes a first winding, a second winding, and a third winding forming a three-phase winding, and the first winding, the second winding, and the third winding are respectively connected in parallel with the first phase, the second phase, and the third phase to complete the basic control of the motor by the motor controller.

[0082] -Capacitor C2

[0083] One end of the capacitor C2 is connected to the parallel connection position of the first phase, the second phase and the third phase in the motor, and the other end is connected to the motor controller to be connected in parallel to the interface circuit of the charging circuit.

[0084] With the above configuration, when the DC charging station is connected to the charging circuit through the charging head, the three-phase winding of the motor forms a three-phase inductor, and the first phase, the second phase, and the third phase will be used as the switch bridge of the boost charging circuit formed by the capacitor C2. Furthermore, the specific components of the charging circuit can be configured as follows: the first phase includes a switch tube S1 and a switch tube S2 connected in series, and connected in parallel to the charging circuit; the second phase includes a switch tube S3 and a switch tube S4 connected in series, and connected in parallel to the charging circuit; the third phase includes a switch tube S5 and a switch tube S6 connected in series, and connected in parallel to the charging circuit; one end of the first winding is connected between the switch tube S1 and the switch tube S2; one end of the second winding is connected between the switch tube S3 and the switch tube S4; one end of the third winding is connected between the switch tube S5 and the switch tube S6.

[0085] In order to sample the voltage of capacitor C2 without setting a flying line, a voltage sampling module is connected at both ends of any one of the first phase, the second phase, and the third phase (specifically, between the middle position of switch tube S1 and switch tube S2 and the negative pole of the power supply, between the middle position of switch tube S3 and switch tube S4 and the negative pole of the power supply, and between the middle position of switch tube S5 and switch tube S6 and the negative pole of the power supply), and the voltage of capacitor C2 can be sampled to form a sampled voltage. Due to the influence of the three-phase winding of the motor, the sampled voltage obtained by the voltage sampling module can be understood to have a certain deviation from the actual voltage of capacitor C2, so a relevant correction mechanism is required.

[0086] Specifically, when the switch tube in the motor controller is periodically turned on and off, the inductor current of each phase will be generated in the motor. It can be understood that within one cycle, the inductor current of each phase changes linearly. Where T s is the sampling period, i sFor a phase current, the charge integral in each cycle can be calculated, which means the charge of each phase obtained by the capacitor in each cycle. Therefore, in order to calculate the charge amount in a cycle as accurately as possible, the control module samples the current of the first winding, the second winding and the third winding at the middle moment of each sampling cycle of the motor controller to form the first sampling current, the second sampling current and the third sampling current, thereby avoiding the need for multiple sampling by virtue of the characteristic that the sampling current at the middle moment is basically equivalent to the average current in the sampling cycle. Further, after having, the voltage value of the capacitor C2 in a sampling cycle can be calculated, thereby calculating the voltage change of its voltage change compared with the voltage value of the capacitor C2 in the previous sampling cycle. As the sampling cycle continues to progress, the control module will continue to accumulate on the basis of the voltage change obtained in the previous sampling cycle until the voltage estimate of the capacitor C2 reaches or approaches the target value. When the target value is reached, it means that the pre-charging of the capacitor C2 has been basically completed, and the high-voltage charging seat can be controlled to charge the power supply.

[0087] With the above configuration, firstly, the configuration of flying wires is eliminated to reduce hardware cost, and secondly, the accuracy of the sampled current ensures the accuracy of the voltage estimation value.

[0088] In a preferred embodiment, in order to achieve closed-loop control, after the voltage estimate of capacitor C2 is obtained, it will be continuously compared with the target voltage value, for example, through the voltage loop control of the PI comparator, the PWM signal of the motor is modulated to change the middle moment of the sampling cycle (the middle moment can be determined by the middle position of the PWM signal in each sampling cycle), so as to continuously adjust the voltage estimate in a closed loop so that it continuously approaches the target voltage value, rather than blindly waiting for the voltage estimate to slowly rise to the target voltage value.

[0089] Further, see Figure 2 The control module samples the current of the first winding, the second winding and the third winding at each valley position of the triangular wave formed in the switching cycle of the three-phase circuit; the control module calculates the voltage change of the capacitor C2 in a single sampling cycle based on the following formula: Where Δu c2 is the voltage change of capacitor C2, i u 、i v 、i ω are the first sampling current, the second sampling current and the third sampling current of the first phase, the second phase and the third phase respectively, T s is the sampling period, C2 is the actual capacitance value of capacitor C2, which can be obtained when the charging circuit is established. Based on the voltage change of capacitor C2 obtained above, the control module continuously accumulates the voltage change within the sampling period based on the following formula: c2 (k) = u c2 (k-1)+Δuc2 (k), k = 1, 2, 3, ...; where u c2 (k) is the voltage estimation value of the current sampling period, u c2 (k-1) is the voltage estimate of the previous sampling period, Δu c2 (k) is the voltage change in the current sampling period. Therefore, according to the control of the switch tube, the voltage estimation value of the capacitor C2 is updated after each sampling period, so as to facilitate the real-time grasp of its boosting situation.

[0090] In a preferred embodiment, in order to eliminate the static difference between the voltage estimation value and the target voltage value, prevent current overshoot and oscillation during the pre-charging process, and suppress the vibration of the vehicle, the voltage boosting process and estimation process of the capacitor C2 have a repeated confirmation and calibration process. Specifically, a target voltage value and an initial voltage value are preset in the control module. Figure 3 The motor controller controls the switch tube of the three-phase circuit to open and close periodically to charge the capacitor C2, so that the capacitor C2 is nonlinearly boosted. When the control module calculates that the voltage estimate of the capacitor C2 is stable and close to the initial voltage value, the control module will send a shut-down instruction to the motor controller to shut down the switch tube on the three-phase circuit so that the first sampling current, the second sampling current and the third sampling current are zero. In this state, since the motor no longer generates electricity, the capacitor C2 will stabilize at the capacitance value at the shut-down moment. At this time, the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value. The control module then calculates a voltage correction value based on the voltage estimate of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value. The voltage correction value indicates whether the error between the voltage estimate value and the actual voltage value obtained by the software calculation is within an acceptable range under the first comparison, and further, the error is compensated. Specifically, the control module superimposes the voltage correction value on the initial voltage value to form a control voltage value, and uses the control voltage value as the target for capacitor C2 to be boosted in a new iteration process, and sends an open-tube instruction to the motor controller at the same time. As capacitor C2 is boosted again, the control module calculates that the voltage estimate of capacitor C2 is stable and close to the control voltage value, and sends a close-tube instruction to the motor controller again to make the first sampling current, the second sampling current and the third sampling current zero, and at this time the voltage sampling module samples the voltage of capacitor C2 to form an actual voltage value, that is, the previous process is executed again. Similarly, the control module updates the voltage correction value based on the voltage estimate of capacitor C2 and the actual voltage value of capacitor C2, and based on the actual voltage value of capacitor C2 and the target voltage value; the control module repeatedly iterates the above update process until the voltage estimate converges to the target voltage value. Through the above process, the accuracy judgment of the voltage estimate is no longer completed at the target voltage value, but is corrected in a step-by-step manner to reduce steady-state errors and prevent electric vehicles from shaking.

[0091] Furthermore, the control module calculates the voltage correction value based on the following formula: Where ΔV ref (i) is the voltage correction value, V s is the actual voltage value, V q is the voltage estimate, V ref_final is the target voltage value, c1 is the first iteration coefficient, c2 is the second iteration coefficient. In different embodiments, the first iteration coefficient and the second iteration coefficient can be adjusted continuously. Under different first iteration coefficients and second iteration coefficients, the number of iterations may be different. It can be understood that the more iterations there are, the more accurate the correction of the voltage estimation value is. At the same time, the control module calculates the control voltage value based on the following formula: V ref (i+1)=V ref (i)+ΔV ref (i) Where V ref (i+1) is the control voltage value in the current iteration process, V ref (i) is the control voltage value in the previous iteration process. For the time control of the boost process and the shut-off process, in a preferred embodiment, each boost process can be 0.15 seconds, and the shut-off process can be 0.05 seconds, so as to confirm as soon as possible whether the voltage estimation value of capacitor C2 is steady state.

[0092] After the above correction, the control voltage value in the next iteration process will be determined by the voltage estimation value and the control voltage value in the previous iteration process, and in each steady state, the difference between the control voltage value and the voltage estimation value will become smaller as the number of iterations increases until the voltage estimation value converges to the target voltage value.

[0093] Among them, the steady state can be judged in the following way: an error rate (for example, ±20%) is preset in the control module. When the ratio of the difference between the actual voltage value and the voltage estimate value to the actual voltage value is less than or equal to the error rate, and the voltage estimate value is maintained for more than a time threshold (for example, 0.03 seconds) within an oscillation range (that is, within a certain period of time, the fluctuation rate of the voltage estimate value does not exceed 10% or 5%), it indicates that the voltage estimate value of capacitor C2 is stably approaching the control voltage value.

[0094] In a preferred embodiment, the cut-off condition of the iteration process can be that the deviation between the voltage estimation value and the target voltage value is less than 10V, or when the time of the iteration process is greater than a specified time T, the control module ends the iteration process to prevent the pre-charging time from being too long. In addition, in any of the above embodiments, the initial voltage value is 60% of the target voltage value, and the specific size of the value can be determined according to the expected number of iterations and the time allowed for pre-charging.

[0095] The present invention also discloses a pre-charging control method for high-voltage direct current charging of an electric vehicle, comprising the following steps: configuring a charging circuit, a voltage sampling module and a control module, wherein the charging circuit comprises: a power supply, which is arranged on the charging circuit; a motor controller, which is connected in parallel to both ends of the power supply, and comprises a first phase, a second phase and a third phase forming a three-phase circuit; a motor, which comprises a first winding, a second winding and a third winding forming a three-phase winding, and the first winding, the second winding and the third winding are connected in parallel to the first phase, the second phase and the third phase respectively; a capacitor C2, one end of which is connected to the parallel connection position of the first phase, the second phase and the third phase in the motor, and the other end is connected to the electric The motor controller is connected in parallel to the interface circuit of the charging circuit; the voltage sampling module is connected in parallel to both ends of any one of the first phase, the second phase and the third phase to form a sampling voltage; the control module samples the current of the first winding, the second winding and the third winding at the middle moment of each sampling cycle of the motor controller to form a first sampling current, a second sampling current and a third sampling current, and calculates the voltage change of the capacitor C2 within a single sampling cycle based on the first sampling current, the second sampling current and the third sampling current; the control module continuously accumulates the voltage change within the sampling cycle until the voltage estimation value of the capacitor C2 is the target voltage value.

[0096] Preferably, the control module performs current sampling on the first winding, the second winding and the third winding at the middle moment of each sampling cycle of the motor controller to form a first sampling current, a second sampling current and a third sampling current, and the step of calculating the voltage change amount of the capacitor C2 within a single sampling cycle based on the first sampling current, the second sampling current and the third sampling current includes: the control module performs current sampling on the first winding, the second winding and the third winding at each valley position of the triangular wave formed in the switching cycle of the three-phase circuit; the control module calculates the voltage change amount of the capacitor C2 within a single sampling cycle based on the following formula: Where Δu c2 is the voltage change of capacitor C2, i u 、i v 、i ω are the first sampling current, the second sampling current and the third sampling current of the first phase, the second phase and the third phase respectively, T s is the sampling period; the control module continuously accumulates the voltage change within the sampling period based on the following formula: c2 (k) = u c2 (k-1)+Δu c2 (k), k = 1, 2, 3, ...; where u c2 (k) is the voltage estimation value of the current sampling period, u c2 (k-1) is the voltage estimate of the previous sampling period, Δu c2 (k) is the voltage change in the current sampling period.

[0097] Preferably, the pre-charging control method further includes the following steps: a target voltage value and an initial voltage value are preset in the control module; the motor controller controls the switch tube of the three-phase circuit to open and close periodically to charge the capacitor C2, and when the control module calculates that the voltage estimate value of the capacitor C2 is stably close to the initial voltage value, a tube closing instruction is sent to the motor controller to make the first sampling current, the second sampling current and the third sampling current zero, and at this time the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value; the control module calculates the voltage correction value based on the voltage estimate value of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value; the control module The control module superimposes the voltage correction value on the initial voltage value to form a control voltage value, and sends an open-tube instruction to the motor controller. When the control module calculates that the voltage estimate value of the capacitor C2 is stably close to the control voltage value, the control module sends a close-tube instruction to the motor controller to make the first sampling current, the second sampling current and the third sampling current zero, and at this time the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value; the control module updates the voltage correction value based on the voltage estimate value of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value; the control module repeatedly iterates the above updating process until the voltage estimate converges to the target voltage value.

[0098] Preferably, the control module calculates the voltage correction value based on the following formula: Where ΔV ref (i) is the voltage correction value, V s is the actual voltage value, V q is the voltage estimate, V ref_final is the target voltage value, c1 is the first iteration coefficient, and c2 is the second iteration coefficient; the control module calculates the control voltage value based on the following formula: V ref (i+1)=V ref (i)+ΔV ref (i) Where V ref (i+1) is the control voltage value in the current iteration process, V ref (i) is the control voltage value in the previous iteration process.

[0099] It should be noted that the embodiments of the present invention have better practicability and do not impose any form of limitation on the present invention. Any technician familiar with the field may use the technical content disclosed above to change or modify it into an equivalent effective embodiment. However, any modification or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A pre-charging control system for high-voltage direct current charging of electric vehicles, arranged in the electric vehicle, characterized in that: The pre-charging control system includes a charging circuit, a voltage sampling module and a control module. The charging circuit comprises: A power source, provided on the charging circuit; A motor controller connected in parallel to both ends of the power supply, including a first phase, a second phase, and a third phase forming a three-phase circuit; A motor, comprising a first winding, a second winding and a third winding forming a three-phase winding, wherein the first winding, the second winding and the third winding are connected in parallel to the first phase, the second phase and the third phase respectively; A capacitor C2, one end of which is connected to the parallel connection position of the first phase, the second phase and the third phase in the motor, and the other end of which is connected to the motor controller to be connected in parallel to the interface circuit of the charging circuit; The voltage sampling module is connected to both ends of any one of the first phase, the second phase and the third phase to form a sampling voltage; The control module samples the current of the first winding, the second winding and the third winding in the middle of each sampling cycle of the motor controller to form a first sampling current, a second sampling current and a third sampling current, and calculates the voltage change of the capacitor C2 within a single sampling cycle based on the first sampling current, the second sampling current and the third sampling current; the control module continuously accumulates the voltage change within the sampling cycle until the voltage estimation value of the capacitor C2 is the target voltage value.

2. The pre-charging control system according to claim 1, characterized in that: The control module samples the current of the first winding, the second winding and the third winding at each valley position of the triangular wave formed in the switching cycle of the three-phase circuit; The control module calculates the voltage change of capacitor C2 within a single sampling period based on the following formula: Where Δu c2 is the voltage change of capacitor C2, i u 、i v 、i ω are the first sampling current, the second sampling current and the third sampling current of the first phase, the second phase and the third phase respectively, T s is the sampling period; The control module continuously accumulates the voltage change within the sampling period based on the following formula: at c2 (k)=u c2 (k-1)+Δu c2 (k),k=1,2,3,…; where u c2 (k) is the voltage estimation value of the current sampling period, u c2 (k-1) is the voltage estimate of the previous sampling period, Δu c2 (k) is the voltage change in the current sampling period.

3. The pre-charging control system according to claim 1, characterized in that: The control module is preset with a target voltage value and an initial voltage value; The motor controller controls the switch tube of the three-phase circuit to open and close periodically to charge the capacitor C2. When the voltage estimation value of the capacitor C2 calculated by the control module stably approaches the initial voltage value, the control module sends a switch-off instruction to the motor controller to make the first sampling current, the second sampling current and the third sampling current zero, and at this time, the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value; The control module calculates a voltage correction value based on the estimated voltage value of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value; The control module superimposes the voltage correction value on the initial voltage value to form a control voltage value, and sends an open-tube instruction to the motor controller. When the voltage estimation value of the capacitor C2 calculated by the control module stably approaches the control voltage value, the control module sends a close-tube instruction to the motor controller to make the first sampling current, the second sampling current and the third sampling current zero, and at this time, the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value; The control module updates the voltage correction value based on the estimated voltage value of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value; The control module repeatedly iterates the updating process until the voltage estimation value converges to the target voltage value.

4. The pre-charging control system according to claim 3, characterized in that: The control module calculates the voltage correction value based on the following formula: Where ΔV ref (i) is the voltage correction value, V s is the actual voltage value, V q is the voltage estimate, V ref_final is the target voltage value, c1 is the first iteration coefficient, and c2 is the second iteration coefficient; The control module calculates the control voltage value based on the following formula: V ref (i+1)=V ref (i)+ΔV ref (i) Where V ref (i+1) is the control voltage value in the current iteration process, V ref (i) is the control voltage value in the previous iteration process.

5. The pre-charging control system according to claim 4, characterized in that: An error rate is preset in the control module. When the ratio of the difference between the actual voltage value and the voltage estimation value to the actual voltage value is less than or equal to the error rate, and the voltage estimation value is maintained for more than a time threshold within an oscillation interval, it indicates that the voltage estimation value of the capacitor C2 is stably approaching the control voltage value.

6. The pre-charging control system according to claim 5, characterized in that: The initial voltage value is 60% of the target voltage value; When the time of the iteration process is greater than a specified time T, the control module ends the iteration process.

7. A pre-charging control method for high voltage direct current charging of electric vehicles, characterized in that: The following steps are involved: A charging circuit, a voltage sampling module and a control module are configured, wherein the charging circuit comprises: a power supply, which is arranged on the charging circuit; a motor controller, which is connected in parallel to both ends of the power supply, and comprises a first phase, a second phase and a third phase forming a three-phase circuit; a motor, which comprises a first winding, a second winding and a third winding forming a three-phase winding, and the first winding, the second winding and the third winding are respectively connected in parallel with the first phase, the second phase and the third phase; a capacitor C2, one end of which is connected to the parallel connection position of the first phase, the second phase and the third phase in the motor, and the other end is connected to the motor controller, so as to be connected in parallel to the interface circuit of the charging circuit; The voltage sampling module is connected to both ends of any one of the first phase, the second phase and the third phase to form a sampling voltage; The control module samples the current of the first winding, the second winding and the third winding in the middle of each sampling cycle of the motor controller to form a first sampling current, a second sampling current and a third sampling current, and calculates the voltage change of the capacitor C2 within a single sampling cycle based on the first sampling current, the second sampling current and the third sampling current; the control module continuously accumulates the voltage change within the sampling cycle until the voltage estimation value of the capacitor C2 is the target voltage value.

8. The precharge control method as claimed in claim 7, wherein: The control module samples the current of the first winding, the second winding and the third winding at the middle moment of each sampling cycle of the motor controller to form a first sampling current, a second sampling current and a third sampling current, and the step of calculating the voltage change of the capacitor C2 within a single sampling cycle based on the first sampling current, the second sampling current and the third sampling current includes: The control module samples the current of the first winding, the second winding and the third winding at each valley position of the triangular wave formed in the switching cycle of the three-phase circuit; The control module calculates the voltage change of capacitor C2 within a single sampling period based on the following formula: Where Δu c2 is the voltage change of capacitor C2, i u 、i v 、i ω are the first sampling current, the second sampling current and the third sampling current of the first phase, the second phase and the third phase respectively, T s is the sampling period; The control module continuously accumulates the voltage change within the sampling period based on the following formula: at c2 (k)=u c2 (k-1)+Δu c2 (k),k=1,2,3,…; where u c2 (k) is the voltage estimation value of the current sampling period, u c2 (k-1) is the voltage estimate of the previous sampling period, Δu c2 (k) is the voltage change in the current sampling period.

9. The precharge control method as claimed in claim 7, wherein: The pre-charging control method further comprises the following steps: a target voltage value and an initial voltage value are preset in the control module; The motor controller controls the switch tube of the three-phase circuit to open and close periodically to charge the capacitor C2. When the voltage estimation value of the capacitor C2 calculated by the control module stably approaches the initial voltage value, the control module sends a switch-off instruction to the motor controller to make the first sampling current, the second sampling current and the third sampling current zero, and at this time, the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value; The control module calculates a voltage correction value based on the estimated voltage value of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value; The control module superimposes the voltage correction value on the initial voltage value to form a control voltage value, and sends an open-tube instruction to the motor controller. When the voltage estimation value of the capacitor C2 calculated by the control module stably approaches the control voltage value, the control module sends a close-tube instruction to the motor controller to make the first sampling current, the second sampling current and the third sampling current zero, and at this time, the voltage sampling module samples the voltage of the capacitor C2 to form an actual voltage value; The control module updates the voltage correction value based on the estimated voltage value of the capacitor C2 and the actual voltage value of the capacitor C2, and based on the actual voltage value of the capacitor C2 and the target voltage value; The control module repeatedly iterates the updating process until the voltage estimation value converges to the target voltage value.

10. The precharge control method according to claim 9, wherein: The control module calculates the voltage correction value based on the following formula: Where ΔV ref (i) is the voltage correction value, V s is the actual voltage value, V q is the voltage estimate, V ref_final is the target voltage value, c1 is the first iteration coefficient, and c2 is the second iteration coefficient; The control module calculates the control voltage value based on the following formula: V ref (i+1)=V ref (i)+ΔV ref (i) Where V ref (i+1) is the control voltage value in the current iteration process, V ref (i) is the control voltage value in the previous iteration process.

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