Method and system for starting with capacitor residual voltage and related equipment

Abstract

The invention provides a capacitor residual voltage starting method and system and related equipment, and the method comprises the steps: collecting the capacitor residual voltage of a pre-charging capacitor of a pre-charging circuit of an electric vehicle, and calculating the current resonant cavity voltage difference; according to the current resonant cavity voltage difference and the capacitor residual voltage, setting an external phase shift angle and a starting frequency of a pre-charging circuit; and starting the pre-charging circuit according to the set external shift phase angle and the starting frequency of the pre-charging circuit so as to carry out the pre-charging process of the electric vehicle. According to the scheme, the external shift phase angle and the starting frequency of the pre-charging circuit are set according to the current resonant cavity voltage difference of the pre-charging circuit and the capacitor residual voltage of the pre-charging capacitor, and then the pre-charging circuit is started according to the set external shift phase angle and the starting frequency so as to carry out the pre-charging process of the electric automobile, so that starting with the capacitor residual voltage is realized; and the problem of generation of MOS tube voltage stress is avoided.

Description

Technical Field

[0001] This invention relates to the field of vehicle control technology, and specifically to a method, system, and related equipment for starting a vehicle with residual voltage from a capacitor. Background Technology

[0002] The pre-charge capacitor in electric vehicles typically has a capacity of 1000uF or higher. If the energy of the pre-charge capacitor is consumed solely by parasitic resistance, the residual voltage on the pre-charge capacitor will decay very slowly. This will result in residual capacitor voltage on the high-voltage side during reverse pre-charging. If the starting frequency and duty cycle used during zero-voltage pre-charging on the high-voltage side are still applied when residual capacitor voltage exists, a mismatch between the frequency and the resonant cavity voltage difference will occur, leading to voltage stress on the MOSFET of the low-voltage side switching transistor. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a method, system and related equipment for starting up with residual voltage of capacitor, so as to avoid the problem of voltage stress on the MOSFET of the low-voltage side switching transistor.

[0004] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0005] The first aspect of this invention discloses a method for starting up with residual voltage using a capacitor, the method comprising:

[0006] Collect the residual voltage of the pre-charging capacitor in the pre-charging circuit of the electric vehicle and calculate the current resonant cavity voltage difference;

[0007] Based on the current resonant cavity voltage difference and the residual capacitor voltage, the external phase shift angle and start-up frequency of the pre-charging circuit are set;

[0008] The pre-charging circuit is started according to the set outward phase angle and start frequency to perform the pre-charging process of the electric vehicle.

[0009] Preferably, the phase shift angle and start-up frequency of the pre-charging circuit are set according to the current resonant cavity voltage difference and the residual capacitor voltage, including:

[0010] Determine whether the residual voltage of the capacitor is less than a first preset voltage;

[0011] If the residual voltage of the capacitor is less than the first preset voltage, a target operating frequency that matches the current resonant cavity voltage difference is determined using a preset fitting function;

[0012] The external phase shift angle of the pre-charging circuit is set to a preset phase shift amount, and the start-up frequency of the pre-charging circuit is set to the target operating frequency.

[0013] If the residual voltage of the capacitor is greater than or equal to the first preset voltage, the pre-charging circuit is controlled to discharge until the residual voltage of the capacitor is less than the first preset voltage, and the step of calculating the target operating frequency that matches the current resonant cavity voltage difference is performed.

[0014] Preferably, controlling the pre-charging circuit to discharge until the residual voltage of the capacitor is less than the first preset voltage includes:

[0015] Control the pre-charging circuit to perform closed-loop discharge until the preset discharge conditions are met.

[0016] After the preset discharge conditions are met, the pre-charge circuit is controlled to perform open-loop discharge until the residual voltage of the capacitor is less than the first preset voltage.

[0017] Preferably, the pre-charging circuit includes a first voltage side and a second voltage side, wherein the voltage of the first voltage side is higher than the voltage of the second voltage side;

[0018] The preset discharge condition is that both the first duration and the second duration are greater than the preset duration;

[0019] Wherein, the first duration is the duration during which the residual voltage of the capacitor is continuously less than the second preset voltage, the second duration is the duration during which the output current on the second voltage side is continuously less than the preset current, and the second preset voltage is greater than the first preset voltage.

[0020] Preferred options also include:

[0021] During the startup of the pre-charging circuit, the outward phase angle of the pre-charging circuit is gradually reduced to 0.

[0022] Preferably, determining the target operating frequency that matches the current resonant cavity pressure difference using a preset fitting function includes:

[0023] Using a preset fitting function, a target operating frequency that matches the current resonant cavity pressure difference is determined. The fitting function is obtained by fitting multiple sets of pre-collected resonant cavity pressure differences of the pre-charge circuit with the operating frequency of the pre-charge circuit.

[0024] Preferably, controlling the pre-charge circuit to perform closed-loop discharge until the preset discharge conditions are met includes:

[0025] The reference output voltage on the second voltage side is set to a fixed voltage, and the reference output current on the second voltage side is set to a fixed current, in order to perform closed-loop discharge.

[0026] A second aspect of this invention discloses a system for starting up with residual voltage using a capacitor, the system comprising:

[0027] The processing unit is used to collect the residual voltage of the pre-charging capacitor in the pre-charging circuit of the electric vehicle and calculate the current resonant cavity voltage difference.

[0028] The setting unit is used to set the outer phase shift angle and start-up frequency of the pre-charging circuit according to the current resonant cavity voltage difference and the capacitor residual voltage;

[0029] The starting unit is used to start the pre-charging circuit to perform the pre-charging process of the electric vehicle according to the set outward phase angle and starting frequency of the pre-charging circuit.

[0030] A third aspect of the present invention discloses a computer device, comprising: a processor and a memory, the processor and the memory being connected via a bus; wherein, the processor is used to call and execute a program stored in the memory; the memory is used to store the program, the program being used to implement the method for starting up with residual voltage with capacitor disclosed in the first aspect of the present invention.

[0031] A fourth aspect of the present invention discloses a storage medium storing computer-executable instructions for executing the method for starting up with residual voltage with capacitor disclosed in the first aspect of the present invention.

[0032] The fifth aspect of the present invention discloses an electric vehicle, which includes at least a pre-charging circuit and a controller, wherein the controller is used to execute the method for starting the vehicle with residual voltage with a capacitor disclosed in the first aspect of the present invention.

[0033] Based on the above embodiments of the present invention, a method, system, and related equipment for starting the vehicle with residual capacitor voltage are provided. The method involves: acquiring the residual capacitor voltage of the pre-charging capacitor in the pre-charging circuit of the electric vehicle and calculating the current resonant cavity voltage difference; setting the outer phase angle and starting frequency of the pre-charging circuit according to the current resonant cavity voltage difference and the residual capacitor voltage; and starting the pre-charging circuit according to the set outer phase angle and starting frequency to perform the pre-charging process of the electric vehicle. This solution sets the outer phase angle and starting frequency of the pre-charging circuit based on the current resonant cavity voltage difference and the residual capacitor voltage of the pre-charging capacitor, and then starts the pre-charging circuit according to the set outer phase angle and starting frequency to perform the pre-charging process of the electric vehicle, achieving start-up with residual capacitor voltage and avoiding MOSFET voltage stress problems. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0035] Figure 1 This is a topology example diagram of the pre-charging circuit provided in an embodiment of the present invention;

[0036] Figure 2 This is an example waveform diagram of the response to start-up with residual voltage of capacitor provided in an embodiment of the present invention;

[0037] Figure 3 This is another example waveform diagram of the response waveform for starting up with residual voltage of capacitor provided in an embodiment of the present invention;

[0038] Figure 4 A flowchart of a method for starting up with residual voltage using a capacitor, provided by an embodiment of the present invention;

[0039] Figure 5 A flowchart illustrating the gradual reduction of the outer phase shift angle provided in an embodiment of the present invention;

[0040] Figure 6 A flowchart for setting the outer phase shift angle and starting frequency of the pre-charging circuit provided in an embodiment of the present invention;

[0041] Figure 7 A flowchart illustrating the process of controlling the pre-charge circuit to discharge, provided in an embodiment of the present invention;

[0042] Figure 8 This is an overall flowchart of a method for starting up with residual voltage using a capacitor, provided by an embodiment of the present invention.

[0043] Figure 9 This is a pre-charge effect diagram of capacitor residual voltage start-up provided in an embodiment of the present invention;

[0044] Figure 10 This is another pre-charge effect diagram provided by an embodiment of the present invention for starting the machine with residual voltage using a capacitor;

[0045] Figure 11 This is a structural block diagram of a system with capacitor residual voltage start-up provided in an embodiment of the present invention. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0048] The pre-charge capacitor in electric vehicles typically has a capacity of 1000uF or higher. If the energy of the pre-charge capacitor is consumed solely by parasitic resistance without an external load, the residual voltage on the pre-charge capacitor will decay very slowly. This results in residual capacitor voltage on the high-voltage side during reverse pre-charging. Furthermore, users frequently start and stop the vehicle. When the interval between starting and stopping the vehicle is short, the residual capacitor voltage on the pre-charge capacitor will be more pronounced. If the starting frequency and duty cycle used for zero-voltage pre-charging on the high-voltage side are still employed, a mismatch between the frequency and the resonant cavity voltage difference will occur, leading to voltage stress on the MOSFET of the low-voltage side switch.

[0049] The current conventional approach is to discharge the residual voltage of the capacitor to zero voltage by discharging the capacitor on the high-voltage side, and then pre-charge and start the vehicle from zero voltage. However, this requires a lot of discharge time, which prevents the equipment in the vehicle from being connected to the DC power supply in time.

[0050] To avoid the extra time required to release the residual voltage of the capacitor to zero, it is necessary to ensure that pre-charging can be completed normally even when the capacitor has residual voltage.

[0051] The inventors discovered through research that the pre-charging circuit of an electric vehicle (usually a DC-DC converter or an LLC resonant converter) has a high matching requirement for the starting frequency when starting under different capacitor residual voltages (i.e., pre-charge start-up). If the starting frequency is out of balance with the resonant cavity voltage difference, it will cause the MOS transistor voltage stress on the low-voltage side switching transistor to exceed the specification.

[0052] To address this, this invention proposes a method, system, and related equipment for starting the electric vehicle with residual voltage of a capacitor. The method sets the external phase angle and starting frequency of the pre-charging circuit by using the current resonant cavity voltage difference of the pre-charging circuit and the residual voltage of the pre-charging capacitor. The pre-charging circuit is then started according to the set external phase angle and starting frequency to perform the pre-charging process of the electric vehicle, thereby achieving starting with residual voltage of the capacitor and avoiding the problem of voltage stress on the MOS transistor.

[0053] To better understand the following content of this invention, we will first provide a detailed explanation of the pre-charging circuit and the implementation principle of this invention.

[0054] I. Explanation regarding the pre-charging circuit:

[0055] like Figure 1 As shown in the example diagram of the pre-charging circuit topology, the pre-charging circuit includes a high-voltage side on the left (i.e., the first voltage side mentioned later) and a low-voltage side on the right (i.e., the second voltage side mentioned later). The output terminal of the transformer secondary is connected to a low-voltage battery (whose voltage is denoted as U). LV The energy from the low-voltage battery is transferred to the resonant cavity on the first voltage side by alternately driving the switching transistors SR1 and SR2 on the second voltage side. The switching transistors S1, S2, S3, and S4 on the first voltage side charge the pre-charge capacitor (denoted as C) through a suitable control method. Pre ) and the input capacitance of the pre-charging circuit itself (denoted as C) HV ) charging, when the voltage of the pre-charge capacitor (U) Pre ) and the voltage of the power battery (U Battery When the pressure difference enters the set range, it indicates the end of the pre-charge process, and the pre-charge relay is activated.

[0056] Among them, L r For resonant inductance, C r For resonant capacitor, L m L1 is the magnetizing inductance, L2 is the leakage inductance of the transformer secondary side, and N is the turns ratio (e.g., N=21:1).

[0057] It should be noted that, Figure 1 The L shown in the pre-charge circuit r C r and L m The resonant cavity is formed by the voltage difference between two locations within the resonant cavity. Figure 1 The pre-charge circuit shown is u ct This is the resonant cavity pressure difference (u) ct =u tr -u AB ), or rather, u ct = U LV *N- U HV .

[0058] It should be further explained that, Figure 1 The pre-charging circuit shown is for illustrative purposes only and is not intended to limit the specific form of the pre-charging circuit of the present invention.

[0059] II. Explanation of the implementation principle of this invention:

[0060] For the case of pre-charging with residual capacitor voltage, the following two operating conditions can be distinguished according to the residual capacitor voltage on the first voltage side.

[0061] It should be noted that the theoretical maximum gain of the pre-charging circuit is denoted as the first voltage matching point (U). Pre_opt1 ), U Pre_opt1 =U LV *N.

[0062] The first operating condition: When the pre-charge capacitor on the first voltage side has a high residual voltage, especially when the residual voltage is higher than the theoretical maximum gain of the pre-charge circuit, according to the normal operation of resonant pre-charge, the operating frequency of the pre-charge circuit is already close to the highest frequency.

[0063] Setting the pre-charge circuit's startup frequency (also known as the start-up frequency) to 155kHz will result in a startup response waveform with a relatively high capacitor residual voltage, as shown below. Figure 2 As shown, due to the high residual voltage of the capacitor, energy leakage will occur on the first voltage side, and the transformer will be unilaterally energized during the startup phase, resulting in transformer saturation.

[0064] Figure 2 The high-frequency band, high-capacitance residual voltage pre-charge start-up response waveform shown is divided into five stages: "0-t1", "t1-t2", "t2-t3", "t3-t4", and "t4-t5". The following is a combination of these stages... Figure 1 The pre-charging circuit shown is used to analyze the situation in each of the five stages.

[0065] It should be noted that, Figure 2 The diagram provided is an example of the response waveform of a pre-charge circuit with capacitor residual voltage start-up, which includes a half-bridge circuit structure. PWM1A is the pulse width modulation (PWM) waveform of the upper transistor of the half-bridge in the pre-charge circuit, PWM3A is the PWM waveform of the switching transistor SR1, and PWM3B is the PWM waveform of the switching transistor SR2.

[0066] It should be noted that the upper switch in the half-bridge refers to the upper switch in the half-bridge structure of the pre-charging circuit (i.e., the upper switch on the high-voltage side).

[0067] Figure 2 The "0-t1" stage: from Figure 2 It can be seen that u AB ( Figure 1 The amplitude of the voltage between points A and B (or the inter-bridge voltage in a half-bridge structure) is higher than u. tr ( Figure 1 Inductance L m The amplitude of the voltage between the two ends indicates that the residual voltage of the capacitor on the first voltage side is relatively high. At time 0, the PWM3A driven by the switching transistor SR1 is turned on, u tr If positive, the excitation current i Lm Forward excitation begins. Due to the high residual voltage of the capacitor on the first voltage side, the resonant cavity voltage difference u...ct negative (u) ct =u tr -u AB Therefore, the resonant cavity current i Lr It can only flow in the reverse direction, and because of u AB and u tr The smaller the voltage difference, the smaller the resonant cavity current i. Lr The amplitude is relatively small. (Through "i") L1 =(i Lm +i Lr )*N” can determine i L1 It remains positive and continues to increase.

[0068] Figure 2 During the "t1-t2" phase: At time t1, the PWM3A drive goes low, and the second voltage-side switch SR1 is turned off. However, the current in switch SR1 flows from the drain (D) to the source (S), resulting in a hard turn-off with forward current. The transformer leakage inductance L1 instantaneously generates a large reverse voltage, and the voltage stress V of switch SR1... ds = U LV - u tr1 -u L1 u L1 Since the voltage is L1, the switching transistor will experience a large turn-off peak stress. Because the transformer itself is inductive, a sudden interruption of the current on the second voltage side will also cause a significant drop in the voltage across the second voltage side transformer. tr1 A reverse impulse voltage occurs, and this impulse voltage, when referred to the first voltage side, will cause u ct The rapid reverse decrease further intensifies the changing trend of the resonant cavity current, while the excitation current i Lm It will also decrease rapidly until the transformer's u tr1 Returned to normal. Meanwhile, due to i L1 It was quickly shut down, |i Lr |<|i Lm This results in a differential current still flowing through the anti-parallel diode of the switching transistor SR2, at which point the voltage u of the leakage inductance L2... L2 It is a positive pressure.

[0069] Figure 2 During the "t2-t3" phase: At time t2, PWM3B goes high, and at this time, the switching transistor SR2 is turned on. Since the current of the switching transistor SR2 is still decreasing negatively, the voltage u of the leakage inductance L2... L2 Continue with positive pressure. (U) tr2 =-U LV +V ds2 +u L2 "It can be known that V" ds2 It is approximately 0, therefore u tr2Some voltage will be lost due to leakage inductance voltage u L2 offset, resulting in u tr2 The amplitude decreases significantly, which, when referred to the first voltage side, also reduces the excitation inductor voltage on the first voltage side. Under low negative voltage, i Lm Although it can be reduced towards zero crossing, the excitation current cannot be converted to a negative current during the conduction time of "0-t1". This is achieved through "u ct =u tr -u AB "It can be known that u" tr The resonant cavity voltage u is negative. ct Since it is a very large negative value, the resonant cavity current i Lr The current of the switching transistor SR2 increases rapidly at a faster rate in the reverse direction until it turns off with an extremely large forward current at time t3, generating greater turn-off stress.

[0070] Figure 2 The "t3-t4" stage: The "t3-t4" stage is the same as the "t1-t2" stage. The freewheeling current on the second voltage side causes a reverse voltage surge in the transformer, resulting in an instantaneous i Lr and i Lm As the current increases in the reverse direction, the voltage spike disappears after the current turns from negative to positive. During this stage, the energy from the first voltage side is reversed to the second voltage side.

[0071] Figure 2 The "t4-t5" stage: The "t4-t5" stage is the same as the "0-t1" stage, the switching transistor SR1 is turned on, and in u tr Under the action of positive voltage, the excitation current i Lm If forward excitation continues on top of the initial positive excitation, this constitutes single-sided transformer excitation, which can easily lead to transformer saturation. Because u tr and u AB The voltage u in the resonant cavity remains essentially unchanged. ct It remains unchanged (continuing to remain negative), but the resonant capacitor voltage u cr It has been charged to a relatively high voltage level, via "u Lr =-u cr +u ct "It is evident that u" cr It is already greater than u ct The calculated resonant inductor voltage u Lr Since the value is positive, the resonant cavity circuit will discharge to the resonant capacitor, i Lr Negative decrease.

[0072] Through adjustments over multiple control cycles, when the voltage of the resonant capacitor is charged to a stable operating condition, the resonant current i Lr and excitation current i Lm It will gradually return to a symmetrical state.

[0073] The above analysis shows that when the residual voltage of the capacitor on the first voltage side is high, problems such as unilateral transformer excitation and high voltage stress on the switching transistor on the second voltage side will occur. The root cause is that the transformer voltage referred to the first voltage side is not as high as the residual voltage of the pre-charged capacitor, causing the resonant cavity current to flow in only one direction during the start-up transient process, resulting in hard turn-off. Furthermore, the longer the conduction time, the greater the turn-off current and voltage stress. If the residual voltage of the capacitor on the first voltage side is smaller, the unilateral excitation problem can be avoided. Therefore, at the first voltage matching point (U... Pre_opt1 =U LV *N) The following implements startup with residual voltage of capacitor.

[0074] The second operating condition: When the residual voltage of the pre-charge capacitor on the first voltage side does not exceed the first voltage matching point, although the problem of unilateral excitation is avoided, it is necessary to ensure that the operating frequency of the pre-charge circuit and the voltage difference u of the resonant cavity are consistent. ct They must be matched; otherwise, the MOSFET voltage stress problem of the second voltage-side switch will still occur during the boost and frequency increase process.

[0075] Although the residual capacitor voltage is below the first voltage matching point, for the first wave, if the switch on the second voltage side starts to conduct, i L1 It will flow in the forward direction, and the leakage inductance L1 will be in the current i L1 Under its influence, a positive voltage u will be established. L1 u can be determined using Kirchhoff's Voltage Law (KVL). tr1 Below U LV And u tr1 and U LV The amplitude difference depends on the current i L1 The rise rate and the magnitude of leakage inductance L1. At this time, the problems of small resonant cavity voltage difference and resonant cavity current still exist, and the MOS stress problem of the second voltage side switch transistor cannot be avoided during startup. Therefore, it is necessary to add an external phase shift angle to the pre-charge circuit in the early stage of startup. The purpose of adding the external phase shift angle is to: short-circuit the resonant cavity and reduce the transformer voltage u. tr Fully applied to the resonant cavity voltage u ct Increase the resonant cavity current, and at the resonant cavity current i Lr When reversed, the reverse amplitude is greater than i. Lm This enables soft shutdown.

[0076] It should be noted that the external phase shift angle is the lag angle of the first voltage-side drive relative to the second voltage-side drive.

[0077] The response waveform of starting with a low residual capacitor voltage is as follows: Figure 3 As shown, Figure 3The response waveform of the low capacitor residual voltage pre-charge start-up shown is divided into four stages according to the switching state: "0-t1", "t1-t2", "t2-t3" and "t3-t4".

[0078] Figure 3 In the diagram, PWM1B is the PWM waveform of the lower half-bridge transistor in the pre-charging circuit, PWM3A is the PWM waveform of the switching transistor SR1, and PWM3B is the PWM waveform of the switching transistor SR2.

[0079] It should be noted that the lower switch in the half-bridge refers to the lower switch (high-voltage side lower switch) in the half-bridge structure of the pre-charging circuit.

[0080] Figure 3 During the "0-t1" phase: Due to the addition of the external phase shift angle, at time 0, the drives of PWM1B and PWM3A are simultaneously turned on, and at this time the transformer voltage u tr All injected into the resonant cavity voltage u ct The excitation current and the resonant cavity current increase simultaneously in the positive direction, and the resonant capacitor voltage u... cr It is also increasing rapidly.

[0081] Figure 3 During the "t1-t2" phase: at time t1, the first voltage-side drive PWM1B signal disappears, and PWM1A is turned on. Due to the effect of the outward phase shift, the resonant capacitor voltage is charged to a higher voltage level. According to KVL, "u" can be calculated. Lr =-u cr +u tr -U HV "At this point, the resonant inductor voltage is negative, the resonant inductor begins to discharge, the resonant cavity current begins to decrease, and it continues to charge the resonant capacitor. Until the resonant cavity current reaches 0, the resonant capacitor begins to release the stored energy from the previous stage to the resonant inductor, and the resonant cavity current begins to commutate. When the resonant capacitor voltage drops to 0, the resonant cavity current reaches its maximum reverse current, which, after canceling out the excitation current, results in the lowest current in the switching transistor on the second voltage side." Figure 3 Point P in the diagram is also the optimal turn-off point. After point P, the excitation current continues to increase due to the conduction of switch SR1, while the resonant cavity current, which recharges the resonant capacitor, begins to decrease. Therefore, the second voltage-side current i... L1 It also begins to rise until SR1 turns off with a positive current at time t2. At this time, it is a hard switch, which will generate a high voltage stress on the MOSFET.

[0082] Figure 3 During the "t2-t3" phase: at time t2, SR2 corresponding to PWM3B starts to conduct, and the transformer voltage u trAs the excitation current shifts from positive to negative, it begins to decrease in the reverse direction. At this time, the upper MOSFET PWM1A remains on due to the phase shift, and the resonant inductor continues to increase in the negative direction under the negative voltage of the transformer voltage and the residual voltage on the first voltage side. The resonant capacitor continues to charge. When the voltage of the resonant capacitor equals the sum of the voltages of the two voltages mentioned above, the resonant inductor, the pre-charge capacitor, and the transformer will simultaneously charge the resonant capacitor until PWM1A is turned off at time t3.

[0083] Figure 3 During the "t3-t4" phase: the lower transistor is re-turned on under the action of PWM1B, the resonant capacitor voltage has been charged to a higher voltage level, and the resonant inductor can only continue to discharge. When the resonant inductor discharges to 0, the resonant capacitor will continue to feed energy back to the resonant inductor. At this time, the resonant cavity current increases in reverse. After being superimposed with the excitation current of approximately 0, the current of SR2 on the second voltage side begins to reverse. When the time reaches t4, the SR2 drive disappears, and at this time, with the reverse current i L2 The system was successfully shut down, achieving a soft shutdown.

[0084] The above analysis shows that when the residual voltage of the capacitor on the first voltage side is lower than the first voltage matching point, starting the power-on with the residual voltage of the capacitor by applying an external phase shift can achieve soft turn-off of the switching transistor on the second voltage side, thereby reducing the failure problem of the MOSFET caused by voltage stress. Therefore, for the first operating condition, when the residual voltage of the capacitor is higher than the first voltage matching point, the residual voltage of the capacitor can be released to below the first voltage matching point by discharging, and then starting the power-on with the residual voltage of the capacitor can be achieved by applying an external phase shift.

[0085] It should be noted that, in the process of implementing capacitor-assisted residual voltage start-up, in order to avoid sampling errors and tolerances between different components, a first preset voltage (which can be called the second voltage matching point, denoted as U) can be used. Pre_opt2 ) to replace the first voltage matching point (U) Pre_opt1 To achieve start-up with residual capacitor voltage, specifically, when the residual capacitor voltage on the first voltage side is lower than the first preset voltage, start-up with residual capacitor voltage is achieved directly by adding an external phase angle; when the residual capacitor voltage exceeds the first preset voltage, it is first discharged and then start-up with residual capacitor voltage is achieved by adding an external phase angle.

[0086] In some examples, the first preset voltage = the first voltage matching point - the first preset value, i.e., U Pre_opt2 =U LV *N - First preset value, where N is the turns ratio of the transformer in the pre-charging circuit.

[0087] The above is an explanation of the pre-charging circuit and the implementation principle of this invention.

[0088] Based on the implementation principle of the present invention described above, see [link to relevant documentation]. Figure 4The flowchart illustrates a method for starting up with residual voltage using a capacitor, as provided in an embodiment of the present invention. The method includes:

[0089] Step S401: Collect the residual voltage of the pre-charging capacitor in the pre-charging circuit of the electric vehicle and calculate the current resonant cavity voltage difference.

[0090] In the specific implementation of step S401, the residual voltage of the pre-charge capacitor in the pre-charge circuit and the low-voltage battery voltage on the second voltage side (low-voltage side) of the pre-charge circuit are collected by the voltage detection device, and the current resonant cavity voltage difference is calculated using the residual voltage and the low-voltage battery voltage.

[0091] For example, combining Figure 1 As shown in the example diagram of the pre-charging circuit, the U-series capacitors are collected. HV and U LV And through "u ct = U LV *NU HV Calculate the current resonant cavity pressure difference u ct .

[0092] Step S402: Set the external phase shift angle and start-up frequency of the pre-charge circuit according to the current resonant cavity voltage difference and capacitor residual voltage.

[0093] It should be noted that, as can be seen from the above "II. Explanation of the Implementation Principle of the Invention", the start-up with residual capacitor voltage is divided into two working conditions: high residual capacitor voltage and low residual capacitor voltage. When the residual capacitor voltage of the pre-charged capacitor is lower than the first preset voltage, the start-up with residual capacitor voltage is performed by adding an external phase angle. When the residual capacitor voltage of the pre-charged capacitor is higher than the first preset voltage, the residual capacitor voltage is first released to below the first preset voltage by active discharge, and then the start-up with residual capacitor voltage is performed by adding an external phase angle.

[0094] In the specific implementation of step S402, if the collected residual voltage of the capacitor is less than the first preset voltage, the external phase shift angle of the pre-charging circuit is set to the preset phase shift amount (e.g., 10%), and the start-up frequency of the pre-charging circuit is set to the target operating frequency.

[0095] If the collected residual voltage of the capacitor is greater than or equal to the first preset voltage, the residual voltage of the capacitor is released to below the first preset voltage by active discharge. Then, the external phase shift angle of the pre-charging circuit is set to the preset phase shift amount, and the start-up frequency of the pre-charging circuit is set to the target operating frequency.

[0096] It should be noted that how to set the outer phase shift angle and start-up frequency of the pre-charge circuit will be discussed later. Figure 6 The illustrated embodiments will be described in detail.

[0097] In some embodiments, the first preset voltage is UPre_opt2 That is, the first preset voltage = U LV *N - First preset value. In practical applications, to ensure that the capacitor residual voltage is below the first preset voltage during startup, the actual first preset voltage can be adjusted according to the actual situation. For example: Actual first preset voltage = U Pre_opt2 -Second preset value.

[0098] Step S403: Start the pre-charging circuit according to the set phase shift angle and start frequency of the pre-charging circuit to carry out the pre-charging process of the electric vehicle.

[0099] In the specific implementation of step S403, after setting the outer phase shift angle of the pre-charging circuit to a preset phase shift amount (e.g., 10%) and setting the starting frequency of the pre-charging circuit to the target operating frequency, the pre-charging circuit is started according to the set outer phase shift angle and starting frequency to carry out the pre-charging process of the electric vehicle, that is, starting with capacitor residual voltage according to the set outer phase shift angle and starting frequency.

[0100] It should be noted that phase shifting will significantly increase the amplitude of the resonant cavity current in the pre-charging circuit, and the voltage of the resonant capacitor will also increase accordingly. In order to avoid high resonant capacitor withstand voltage stress, the external phase shift angle needs to be adjusted to 0 after the pre-charging circuit is started.

[0101] In some embodiments, during the initiation of the pre-charge circuit, the outward phase angle of the pre-charge circuit is gradually reduced to 0.

[0102] In other words, during the process of starting the pre-charging circuit, the external phase shift angle of the pre-charging circuit is gradually reduced from the preset phase shift amount to 0.

[0103] In practical applications, in order to avoid the system step response caused by the sudden elimination of the outer phase angle of the pre-charge circuit, the outer phase angle of the pre-charge circuit can be gradually reduced to 0 over multiple control cycles, thereby restoring the pre-charge circuit to a zero-phase-shift state.

[0104] The following is passed Figure 5 The flowchart shown illustrates a process for gradually reducing the outer phase shift angle, using a practical application scenario to explain how to gradually reduce the outer phase shift angle of the pre-charging circuit to 0. The preset phase shift amount is 10%. Figure 5 Includes the following steps:

[0105] Step S501: Set the outer phase shift angle α of the pre-charge circuit to 10%.

[0106] Step S502: Control cycle n=0.

[0107] Step S503: Determine if n is greater than or equal to 10. If yes, the outward phase angle α has been reduced to 0; if no, proceed to step S504.

[0108] Step S504: a = a - 1%, n = n + 1, return to step S503.

[0109] As can be seen from the contents of steps S501-S504 above, during the start-up of the pre-charging circuit, the outward phase angle of the pre-charging circuit can be reduced by 1% in each control cycle, and the outward phase angle of the pre-charging circuit is reduced to 0 after 10 control cycles.

[0110] Through the above embodiments, one application scenario of the present invention is as follows: the pre-charging circuit is started according to the set external phase angle and start-up frequency of the pre-charging circuit. After 10 control cycles, the external phase angle is reduced to 0, and the operating frequency of the pre-charging circuit gradually increases. If the pre-charging circuit is not charged to the target voltage after the operating frequency reaches the maximum frequency, the gain is increased by adding an external phase angle until the pre-charging circuit is charged to the target voltage.

[0111] In this embodiment of the invention, the outward phase angle and start-up frequency of the pre-charging circuit are set by the current resonant cavity voltage difference of the pre-charging circuit and the residual voltage of the pre-charging capacitor. Then, the pre-charging circuit is started according to the set outward phase angle and start-up frequency to carry out the pre-charging process of the electric vehicle, so as to realize the start-up with residual capacitor voltage and avoid the problem of MOS tube voltage stress.

[0112] According to the embodiments of the present invention Figure 4 Step S402 involves setting the outer phase shift angle and start-up frequency of the pre-charge circuit, see [link / reference]. Figure 6 This document illustrates a flowchart of setting the outer phase shift angle and starting frequency of the pre-charging circuit according to an embodiment of the present invention. Figure 6 Includes the following steps:

[0113] Step S601: Determine whether the residual voltage of the capacitor is less than the first preset voltage. If the residual voltage of the capacitor is less than the first preset voltage, proceed to steps S602 and S603. If the residual voltage of the capacitor is greater than or equal to the first preset voltage, proceed to step S604.

[0114] It should be noted that the closer the residual voltage of the capacitor is to the first preset voltage (U), the better. Pre_opt2 ), resonant cavity pressure difference u ct The smaller the voltage, the smaller the resonant cavity current will be. To avoid sampling errors, the actual first preset voltage can be further reduced from the original value. When the capacitor residual voltage is lower than the first preset voltage, the machine can be started directly with the capacitor residual voltage.

[0115] In practical applications, the higher the battery voltage on the second voltage side (i.e., the low voltage side) of the pre-charging circuit, the higher the transformer voltage will be, and the excitation current will increase accordingly. At this time, the amplitude of the reverse current that needs to be offset by the resonant cavity inductor current will also be larger. Therefore, the battery voltage on the second voltage side needs to be set to a fixed voltage value (e.g., 15V).

[0116] In the specific implementation of step S601, the residual voltage of the pre-charged capacitor is compared with a first preset voltage. If the residual voltage is less than the first preset voltage, steps S602 and S603 are executed. If the residual voltage is greater than or equal to the first preset voltage, step S604 is executed.

[0117] Step S602: Determine the target operating frequency that matches the current resonant cavity pressure difference using a preset fitting function.

[0118] It should be noted that, as seen in Section II, "Explanation of the Implementation Principle of the Invention," if the start-up frequency is inappropriate, there exists an optimal turn-off point during the turn-off process. If the resonant cavity voltage difference and the operating frequency do not match, the different turn-off points will cause the switching transistor to enter the hard turn-off region. Therefore, it is necessary to determine a fitting function, which is a functional relationship between the operating frequency and the resonant cavity voltage difference.

[0119] In the specific implementation, the pre-charging circuit is fully pre-charged once (from 0 to the target voltage), and the operating frequency and resonant cavity voltage difference of each control cycle during the pre-charging process are recorded in a static array. This static array includes multiple sets of corresponding "resonant cavity voltage difference of the pre-charging circuit" and "operating frequency of the pre-charging circuit". Each set of "resonant cavity voltage difference of the pre-charging circuit" and "operating frequency of the pre-charging circuit" has a corresponding relationship.

[0120] After pre-filling is complete, the data in the static array is exported to a table to establish a fitting relationship, thereby obtaining the fitting function.

[0121] It should be noted that when exporting data from the static array to a table to establish a fitting relationship, only the switching frequency and resonant cavity voltage difference below the first preset voltage need to be considered. The final fitted function can be used to calculate the corresponding operating frequency based on different resonant cavity voltage differences.

[0122] That is, the fitting function is obtained by fitting the resonant cavity voltage difference of multiple sets of corresponding pre-charge circuits with the operating frequency of the pre-charge circuit.

[0123] In the specific implementation of step S602, a target operating frequency that matches the current resonant cavity pressure difference is determined using a preset fitting function.

[0124] In other words, by inputting the current resonant cavity pressure difference into the fitting function, the target operating frequency corresponding to the current resonant cavity pressure difference can be calculated using the fitting function.

[0125] Step S603: Set the external phase shift angle of the pre-charge circuit to a preset phase shift amount, and set the start-up frequency of the pre-charge circuit to the target operating frequency.

[0126] It should be noted that different external phase shift angles have a significant impact on the energy storage capacity of the resonant capacitor. In order to save workload, the worst operating condition can be selected to determine the largest external phase shift angle as the preset phase shift amount. For example, the preset phase shift amount can be set to 10%, that is, regardless of the voltage range of the capacitor residual voltage, the external phase shift angle of the pre-charging circuit will be set to a fixed preset phase shift amount.

[0127] Step S604: Control the pre-charging circuit to discharge until the residual voltage of the capacitor is less than the first preset voltage, and execute steps S602 and S603.

[0128] In the specific implementation of step S604, if the residual voltage of the capacitor is greater than or equal to the first preset voltage, there will be a problem of single-sided excitation and voltage stress on the MOS transistor on the second voltage side upon startup. Therefore, it is necessary to control the pre-charge circuit to discharge until the residual voltage of the capacitor is less than the first preset voltage before executing steps S602 and S603. That is, the residual voltage of the capacitor on the first voltage side (i.e., the high voltage side) is discharged until it is less than the first preset voltage before executing steps S602 and S603.

[0129] In some embodiments, the pre-charging circuit includes a first voltage side and a second voltage side, wherein the voltage of the first voltage side is higher than the voltage of the second voltage side. The specific implementation of controlling the pre-charging circuit to discharge is as follows: the pre-charging circuit is controlled to perform closed-loop discharge until a preset discharge condition is met; after the preset discharge condition is met, the pre-charging circuit is then controlled to perform open-loop discharge until the residual capacitor voltage is less than a first preset voltage.

[0130] The preset discharge condition is that both the first duration and the second duration are greater than the preset duration.

[0131] The first duration is the duration during which the residual voltage of the capacitor is continuously less than the second preset voltage, the second duration is the duration during which the output current on the second voltage side is continuously less than the preset current, and the second preset voltage is greater than the first preset voltage.

[0132] It should be noted that the second preset voltage, preset current, and preset duration can be calibrated according to the actual situation.

[0133] For example: the second preset voltage = the first preset voltage + the third preset value, and the preset current is set to the fourth preset value.

[0134] In other words, the process of controlling the pre-charging circuit to discharge is divided into two stages: closed-loop discharge and open-loop discharge. Through these two stages of discharge, the residual voltage of the capacitor is released to a level lower than the first preset voltage. The closed-loop discharge and open-loop discharge are explained in detail below.

[0135] During the discharge process, a closed-loop discharge method is used to balance the discharge speed and the charging health of the low-voltage battery (the battery on the second voltage side), as well as to avoid uncontrollable damage to the low-voltage battery during discharge. The closed-loop discharge is implemented by calling the forward charging buck control program, setting the reference output voltage on the second voltage side to a fixed voltage, and setting the reference output current on the second voltage side to a fixed current, so as to perform closed-loop discharge.

[0136] It should be noted that, in order to prevent the low-voltage battery from continuing to feed energy back to the first voltage side, the switching transistors SR1 and SR2 need to be turned off simultaneously during the discharge process.

[0137] Because of the maximum gain problem in the pre-charge circuit, when the capacitor residual voltage discharges to near the first preset voltage, the output voltage on the second voltage side cannot reach the reference output voltage, and the discharge fails at this time. In order to improve the discharge speed, reduce the pre-charge waiting time and improve the user experience, when the output voltage gain on the second voltage side is insufficient, it is necessary to use an open-loop discharge method to speed up the discharge process.

[0138] The open-loop discharge is achieved by increasing the operating frequency of the pre-charge circuit (for example, setting the operating frequency to a fixed frequency) according to the characteristics of the pre-charge circuit to enter the hard-switching region, and increasing the discharge speed through high-frequency hard switching.

[0139] In other words, when the residual voltage of the capacitor discharges to near the first preset voltage, the gain of the closed-loop discharge is insufficient (i.e., the output voltage on the second voltage side does not reach the voltage U of the low-voltage battery). LV When the capacitor can no longer release energy to the low-voltage battery, it needs to further consume the residual voltage of the capacitor through high-frequency hard switching. The whole process is called open-loop discharge.

[0140] It should be noted that, in order to further improve the discharge speed, for a pre-charge circuit using a half-bridge topology, the discharge speed can be increased by reducing the duty cycle (for example, by adjusting the duty cycle to 0.1); for a pre-charge circuit using a full-bridge topology, the discharge speed can be increased by adding an inner phase shift angle on the first voltage side.

[0141] In addition, to avoid accidentally entering the open-loop discharge process, the present invention sets preset discharge conditions, and only when the preset discharge conditions are met will the open-loop discharge process begin.

[0142] To better understand how to perform closed-loop and open-loop discharge, the following will explain... Figure 7 The flowchart shown illustrates the process of controlling the pre-charge circuit to discharge. Figure 7 Includes the following steps:

[0143] Step S701: Control the pre-charge circuit to perform closed-loop discharge.

[0144] In the specific implementation step S701, the reference output voltage of the second voltage side is set to 14.5V, the reference output current of the second voltage side is set to 20A, and then the discharge process is executed to perform closed-loop discharge.

[0145] Step S702: Sample the residual voltage of the capacitor and the output current on the second voltage side.

[0146] Step S703: Determine whether the residual voltage of the capacitor is less than the second preset voltage and whether the output current is less than the preset current. If not, return to step S701 to continue closed-loop discharge; if yes, proceed to step S704.

[0147] Step S704: Determine whether both the first duration and the second duration are greater than a preset duration. If both the first duration and the second duration are greater than the preset duration, proceed to step S705; if the first duration and / or the second duration are not greater than the preset duration, return to step S701 to continue closed-loop discharge.

[0148] Step S705: Control the pre-charge circuit to perform open-loop discharge.

[0149] Step S706: Determine whether the residual voltage of the capacitor is less than the first preset voltage; if yes, end; if no, return to step S705 to continue open-loop discharge.

[0150] above Figure 7 This is an example of controlling the pre-charge circuit to discharge. After releasing the residual voltage of the capacitor to below the first preset voltage, the machine is started with the residual voltage of the capacitor according to the set external phase angle and start-up frequency.

[0151] Overall, the implementation process of this invention is as follows: Figure 8 The overall flowchart of a method for starting up with residual voltage using a capacitor is shown. Figure 8 Includes the following steps:

[0152] Step S801: Sample the residual voltage of the capacitor and calculate the current resonant cavity voltage difference.

[0153] Step S802: Determine whether the residual voltage of the capacitor is less than the first preset voltage. If not, discharge the capacitor and proceed to step S801; if yes, proceed to step S803.

[0154] Step S803: Use the fitting function to determine the target operating frequency that matches the current resonant cavity pressure difference.

[0155] Step S804: Set the external phase shift angle of the pre-charge circuit to the preset phase shift amount, and set the start-up frequency of the pre-charge circuit to the target operating frequency.

[0156] Step S805: Start the pre-charging circuit according to the set phase shift angle and start frequency of the pre-charging circuit to carry out the pre-charging process of the electric vehicle.

[0157] Step S806: Gradually reduce the outward phase angle of the pre-charge circuit to 0.

[0158] above Figure 8 This is an example illustrating the overall implementation process of the present invention.

[0159] From the practical application effect of this invention, the effect of starting with residual voltage of different capacitors is as follows: Figure 9 and Figure 10 As shown, Figure 9 This is a diagram illustrating the pre-charge effect when starting the device with a 100V capacitor residual voltage. Figure 10 This is a diagram illustrating the pre-charge effect when starting the machine with residual 820V capacitor voltage. Figure 9 and Figure 10 In this diagram, CH1 represents the pre-charge voltage on the first voltage side, CH2 represents the voltage stress of switch SR1, CH3 represents the voltage stress of switch SR2, and CH4 represents the charging current on the second voltage side.

[0160] from Figure 9 and Figure 10 As shown in the pre-charge effect diagram, when using the present invention for capacitor-assisted residual voltage start-up, the V of the second voltage-side MOS transistor... ds The turn-off voltage stress is generally low, ensuring the safety of the MOSFET.

[0161] Corresponding to the method for starting up with residual voltage with capacitor provided in the above embodiments of the present invention, see also... Figure 11 The present invention also provides a structural block diagram of a system with capacitor residual voltage start-up, the system including: a processing unit 1101, a setting unit 1102 and a start-up unit 1103.

[0162] The processing unit 1101 is used to collect the residual voltage of the pre-charge capacitor in the pre-charge circuit of the electric vehicle and calculate the current resonant cavity voltage difference.

[0163] Setting unit 1102 is used to set the external phase shift angle and start-up frequency of the pre-charge circuit according to the current resonant cavity voltage difference and capacitor residual voltage.

[0164] The starting unit 1103 is used to start the pre-charging circuit to carry out the pre-charging process of the electric vehicle according to the set out phase angle and starting frequency of the pre-charging circuit.

[0165] In this embodiment of the invention, the outward phase angle and start-up frequency of the pre-charging circuit are set by the current resonant cavity voltage difference of the pre-charging circuit and the residual voltage of the pre-charging capacitor. Then, the pre-charging circuit is started according to the set outward phase angle and start-up frequency to carry out the pre-charging process of the electric vehicle, so as to realize the start-up with residual capacitor voltage and avoid the problem of MOS tube voltage stress.

[0166] Preferred, combined Figure 11 The set unit 1102, as shown, includes a judgment module, a calculation module, a setting module, and a discharge module. The execution principle of each module is as follows:

[0167] The judgment module is used to determine whether the residual voltage of the capacitor is less than the first preset voltage.

[0168] The calculation module is used to determine the target operating frequency that matches the current resonant cavity voltage difference if the residual voltage of the capacitor is less than the first preset voltage, using a preset fitting function.

[0169] In some embodiments, the calculation module is specifically used to: determine a target operating frequency that matches the current resonant cavity pressure difference using a preset fitting function, wherein the fitting function is obtained by fitting the resonant cavity pressure difference of multiple pre-charge circuits and the operating frequency of the pre-charge circuits that have been pre-collected.

[0170] The setting module is used to set the external phase shift angle of the pre-charge circuit to a preset phase shift amount and to set the start-up frequency of the pre-charge circuit to the target operating frequency.

[0171] The discharge module is used to control the pre-charging circuit to discharge until the capacitor residual voltage is less than the first preset voltage if the residual voltage of the capacitor is greater than or equal to the first preset voltage, and then execute the calculation module.

[0172] In some embodiments, the discharge module is specifically used to: control the pre-charge circuit to perform closed-loop discharge until a preset discharge condition is met; after the preset discharge condition is met, control the pre-charge circuit to perform open-loop discharge until the capacitor residual voltage is less than a first preset voltage.

[0173] The pre-charging circuit includes a first voltage side and a second voltage side, with the voltage on the first voltage side being higher than the voltage on the second voltage side. The preset discharge condition is that both the first duration and the second duration are greater than a preset duration.

[0174] The first duration is the duration during which the residual voltage of the capacitor is continuously less than the second preset voltage, the second duration is the duration during which the output current on the second voltage side is continuously less than the preset current, and the second preset voltage is greater than the first preset voltage.

[0175] In one specific embodiment, the discharge module controls the pre-charge circuit to perform closed-loop discharge, which includes setting the reference output voltage on the second voltage side to a fixed voltage and setting the reference output current on the second voltage side to a fixed current, so as to perform closed-loop discharge.

[0176] Preferred, combined Figure 11 The system also includes, as shown, the following:

[0177] The adjustment unit is used to gradually reduce the outward phase angle of the pre-charge circuit to 0 during the start-up process.

[0178] Preferably, the present invention also provides a computer device, including: a processor and a memory, the processor and the memory being connected via a bus; wherein, the processor is used to call and execute a program stored in the memory; the memory is used to store the program, the program being used to implement the method of starting with residual voltage with capacitor provided in the above method embodiments.

[0179] Preferably, the present invention also provides a storage medium storing computer-executable instructions for executing the method for starting up with residual voltage with capacitor provided in the above method embodiments.

[0180] Preferably, embodiments of the present invention also provide an electric vehicle, including at least a pre-charging circuit and a controller, wherein the controller is used to execute the method for starting with residual voltage of capacitor provided in the above method embodiments.

[0181] In summary, the embodiments of the present invention provide a method, system, and related equipment for starting the electric vehicle with residual voltage of a capacitor. The method sets the external phase angle and starting frequency of the pre-charging circuit by using the current resonant cavity voltage difference of the pre-charging circuit and the residual voltage of the pre-charging capacitor. The pre-charging circuit is then started according to the set external phase angle and starting frequency to perform the pre-charging process of the electric vehicle, thereby realizing starting the electric vehicle with residual voltage of a capacitor and avoiding the problem of voltage stress on the MOS transistor.

[0182] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0183] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0184] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for starting up with residual voltage using a capacitor, characterized in that, The method includes: Collect the residual voltage of the pre-charging capacitor in the pre-charging circuit of the electric vehicle and calculate the current resonant cavity voltage difference; Based on the current resonant cavity voltage difference and the residual capacitor voltage, the external phase shift angle and start-up frequency of the pre-charging circuit are set; The pre-charging circuit is started according to the set outward phase angle and start frequency to perform the pre-charging process of the electric vehicle.

2. The method according to claim 1, characterized in that, Based on the current resonant cavity voltage difference and the residual capacitor voltage, the outer phase shift angle and start-up frequency of the pre-charging circuit are set, including: Determine whether the residual voltage of the capacitor is less than a first preset voltage; If the residual voltage of the capacitor is less than the first preset voltage, a target operating frequency that matches the current resonant cavity voltage difference is determined using a preset fitting function; The external phase shift angle of the pre-charging circuit is set to a preset phase shift amount, and the start-up frequency of the pre-charging circuit is set to the target operating frequency. If the residual voltage of the capacitor is greater than or equal to the first preset voltage, the pre-charging circuit is controlled to discharge until the residual voltage of the capacitor is less than the first preset voltage, and the step of calculating the target operating frequency that matches the current resonant cavity voltage difference is performed.

3. The method according to claim 2, characterized in that, Controlling the pre-charging circuit to discharge until the residual voltage of the capacitor is less than the first preset voltage includes: Control the pre-charging circuit to perform closed-loop discharge until the preset discharge conditions are met. After the preset discharge conditions are met, the pre-charge circuit is controlled to perform open-loop discharge until the residual voltage of the capacitor is less than the first preset voltage.

4. The method according to claim 3, characterized in that, The pre-charging circuit includes a first voltage side and a second voltage side, wherein the voltage of the first voltage side is higher than the voltage of the second voltage side; The preset discharge condition is that both the first duration and the second duration are greater than the preset duration; Wherein, the first duration is the duration during which the residual voltage of the capacitor is continuously less than the second preset voltage, the second duration is the duration during which the output current on the second voltage side is continuously less than the preset current, and the second preset voltage is greater than the first preset voltage.

5. The method according to claim 1, characterized in that, Also includes: During the startup of the pre-charging circuit, the outward phase angle of the pre-charging circuit is gradually reduced to 0.

6. The method according to claim 2, characterized in that, The step of determining the target operating frequency that matches the current resonant cavity pressure difference using a preset fitting function includes: Using a preset fitting function, a target operating frequency that matches the current resonant cavity pressure difference is determined. The fitting function is obtained by fitting multiple sets of pre-collected resonant cavity pressure differences of the pre-charge circuit with the operating frequency of the pre-charge circuit.

7. The method according to claim 4, characterized in that, The control of the pre-charge circuit to perform closed-loop discharge until the preset discharge conditions are met includes: The reference output voltage on the second voltage side is set to a fixed voltage, and the reference output current on the second voltage side is set to a fixed current, in order to perform closed-loop discharge.

8. A system for starting up with residual voltage from a capacitor, characterized in that, The system includes: The processing unit is used to collect the residual voltage of the pre-charging capacitor in the pre-charging circuit of the electric vehicle and calculate the current resonant cavity voltage difference. The setting unit is used to set the outer phase shift angle and start-up frequency of the pre-charging circuit according to the current resonant cavity voltage difference and the capacitor residual voltage; The starting unit is used to start the pre-charging circuit to perform the pre-charging process of the electric vehicle according to the set outward phase angle and starting frequency of the pre-charging circuit.

9. A computer device, characterized in that, include: A processor and a memory are connected via a bus; wherein the processor is used to call and execute a program stored in the memory; The memory is used to store a program for implementing the method of starting with residual voltage with capacitor as described in any one of claims 1-7.

10. A storage medium, characterized in that, The storage medium stores computer-executable instructions for performing the method of starting with residual voltage with capacitor as described in any one of claims 1-7.

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