Pre-charging method of electric automobile

Abstract

The invention discloses a pre-charging method for an electric vehicle, which comprises the following steps: receiving a vehicle power-on instruction, and sending a reverse pre-charging command to a direct current-direct current converter; controlling the direct current-direct current converter to be switched to an open-loop control forward and reverse excitation mode, and pre-charging the high-voltage bus capacitor; if the direct current-direct current converter meets the push-pull condition, the direct current-direct current converter is controlled to be switched to a closed-loop control push-pull mode, and a high-voltage bus capacitor is pre-charged; and if the high-voltage bus capacitor meets the pre-charging completion condition, controlling the DC-DC converter to quit the reverse pre-charging mode. According to the invention, the high-voltage bus capacitor is pre-charged in the forward and reverse shock mode and then pre-charged in the push-pull mode by multiplexing the original direct current-direct current converter of the electric vehicle, so that the high-voltage bus capacitor of the electric vehicle is pre-charged safely, stably and efficiently.

Description

Technical Field

[0001] The invention relates to the technical field of high-voltage bus capacitor precharging, and in particular to a precharging method for an electric vehicle. Background Art

[0002] With the rapid development of the electric vehicle industry, the safety and efficiency of high-voltage electrical systems have become the focus of industry attention. In electric vehicles, the power main relay is a key component that connects the battery pack with high-voltage loads such as the motor controller and air-conditioning compressor. The voltage and current of its connection process are directly related to the overall performance and safety of the vehicle. Therefore, the high-voltage bus capacitor needs to be pre-charged before the electric vehicle power main relay is connected. The traditional high-voltage bus capacitor pre-charging solution usually relies on an independent pre-charging resistor and a pre-charging relay combination. Although this solution is effective, it has the disadvantages of large space occupation, high cost, and easy burning and failure of the resistor, which limits the further lightweighting, cost optimization, and reliability and stability of electric vehicles.

[0003] In order to solve the above problems, some companies have proposed to drive the switch tube in push-pull mode to achieve reverse pre-charging. However, in push-pull mode, when the duty cycle exceeds 0.5 and the starting current is large, the VDS (drain-source voltage) oscillation voltage of the low-voltage side switch tube will be large; if the VDS oscillation voltage is suppressed by current limiting, the pre-charging time of the high-voltage bus capacitor will be longer, affecting the power-on efficiency of electric vehicles.

[0004] In view of this, it is necessary to provide an electric vehicle precharging method that can simultaneously meet the requirements of high efficiency, safety and low cost. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing electric vehicle high-voltage bus capacitor precharging technology, and to provide an electric vehicle precharging method that can simultaneously meet the requirements of high efficiency, safety and low cost. The method reuses the original DC-DC converter of the electric vehicle, and before the DC-DC converter meets the push-pull condition, the high-voltage bus capacitor is precharged in a forward-flyback mode, and after the DC-DC converter meets the push-pull condition, the DC-DC converter is switched to a push-pull mode to precharge the high-voltage bus capacitor. By reusing the original DC-DC converter of the electric vehicle, the high-voltage bus capacitor can be precharged in a forward-flyback mode and a push-pull mode respectively without adding additional precharging equipment or circuits, which not only avoids the disadvantage of the push-pull mode causing a large oscillation voltage when the initial current is large, but also utilizes the characteristics of the smooth start of the forward-flyback mode precharging, and the high efficiency of the push-pull mode precharging.

[0006] The technical solution of the present invention provides a pre-charging method for an electric vehicle, comprising:

[0007] Upon receiving a vehicle power-on command, a reverse pre-charge command is issued to the DC-DC converter;

[0008] Controlling the DC-DC converter to switch to the forward-flyback mode of open-loop control to pre-charge the high-voltage bus capacitor;

[0009] If the DC-DC converter meets the push-pull condition, controlling the DC-DC converter to switch to a push-pull mode of closed-loop control to pre-charge the high-voltage bus capacitor;

[0010] If the high-voltage bus capacitor meets the pre-charging completion condition, the DC-DC converter is controlled to exit the reverse pre-charging mode.

[0011] In one of the optional technical solutions, the DC-DC converter includes a phase-shifted full-bridge topology and a flyback module;

[0012] The phase-shifted full-bridge topology includes a primary module, a main transformer T1 and a secondary module connected in sequence, the secondary module is connected to a low-voltage battery, and the power battery and the high-voltage bus capacitor are respectively connected to the primary module;

[0013] The flyback module includes a flyback transformer T2 and a flyback loop connected to both ends of the high-voltage bus capacitor, and the flyback loop is connected to the secondary module through the flyback transformer T2.

[0014] In one of the optional technical solutions, the primary side module includes a bridge rectifier circuit, the secondary side circuit includes a full-wave rectifier circuit, the secondary side module can switch between a positive half-cycle output state, a negative half-cycle output state and an inductive energy storage state, and the primary side module can switch between a forward input state, a reverse input state and a power-off state.

[0015] In one of the optional technical solutions, the forward-flyback mode includes four working modes that are executed in sequence in a cycle, including:

[0016] In the first forward mode, the secondary module switches to the positive half-cycle output state, the primary module switches to the forward input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology;

[0017] In the first flyback mode, the secondary module and the primary module are both powered off, the flyback transformer T2 is activated, and the low-voltage battery charges the high-voltage bus capacitor through the flyback circuit;

[0018] In the second forward mode, the secondary module switches to the negative half-cycle output state, the primary module switches to the reverse input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology;

[0019] In the second flyback mode, the secondary module and the primary module are both powered off, the flyback transformer T2 is activated, and the low-voltage battery charges the high-voltage bus capacitor through the flyback circuit.

[0020] In one of the optional technical solutions, the push-pull mode includes four working modes that are executed in sequence and in a cycle, including:

[0021] In the first push-pull mode, the secondary side module is switched to the inductive energy storage state, and the primary side module is powered off;

[0022] In the second push-pull mode, the secondary module switches to the positive half-cycle output state, the primary module switches to the forward input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology;

[0023] In the third push-pull mode, the secondary module is switched to the inductive energy storage state, and the primary module is powered off;

[0024] In the fourth push-pull mode, the secondary module is switched to the negative half-cycle output state, the primary module is switched to the reverse input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology.

[0025] In one of the optional technical solutions, the main transformer T1 includes a primary winding and a secondary winding, and the secondary winding includes a central end and two ends;

[0026] The full-wave rectifier circuit includes a switch tube Q5, a switch tube Q6, a filter inductor Lf, a leakage inductor Lk, a resistor R and a transient voltage suppressor TVS;

[0027] The central end of the secondary winding is connected to the positive electrode of the low-voltage battery, and the two ends of the secondary winding are connected to the negative electrode of the low-voltage battery through the switch tube Q5 and the switch tube Q6 respectively;

[0028] A filter inductor Lf and a leakage inductor Lk are connected in series between the positive pole of the low-voltage battery and the central end of the secondary winding. A resistor R is connected in parallel with the filter inductor Lf and the leakage inductor Lk, and a transient voltage suppressor TVS is connected in series with the resistor R. One side winding of the flyback transformer T2 is connected in parallel with the filter inductor Lf, and the other side winding of the flyback transformer T2 is connected to the flyback circuit.

[0029] In one of the optional technical solutions, in the forward-flyback mode, the switch tube Q5, the switch tube Q6 and the flyback transformer T2 are alternately turned on;

[0030] In the push-pull mode, the switch tube Q5 and the switch tube Q6 are alternately switched between a simultaneous conduction state and a separate conduction state.

[0031] In one of the optional technical solutions, in the positive half-cycle output state, the switch tube Q5 is turned off and the switch tube Q6 is turned on;

[0032] In the negative half-cycle output state, the switch tube Q5 is turned on and the switch tube Q6 is turned off;

[0033] In the inductor energy storage state, the switch tube Q5 and the switch tube Q6 are turned on at the same time.

[0034] In one of the optional technical solutions, the bridge rectifier circuit includes a switch tube Q1, a switch tube Q3, a switch tube Q2, a switch tube Q4, a diode D1, a diode D2, a resonant inductor Lr and a DC blocking capacitor Cb;

[0035] The high-voltage bus capacitor, the switch tube Q1 and the switch tube Q3 connected in series, the switch tube Q2 and the switch tube Q4 connected in series, and the diode D1 and the diode D2 connected in series are sequentially connected in parallel;

[0036] One end of the primary winding is connected between the switch tube Q1 and the switch tube Q3 through the resonant inductor Lr, and the other end of the primary winding is connected between the switch tube Q2 and the switch tube Q4 through the DC blocking capacitor Cb.

[0037] In one of the optional technical solutions, in the forward input state, the high-voltage bus capacitor, the switch tube Q4, the DC blocking capacitor Cb, the primary winding and the diode D1 are turned on in sequence to form a loop;

[0038] In the reverse input state, the high-voltage bus capacitor, the diode D2, the primary winding, the DC blocking capacitor Cb and the switch tube Q2 are turned on in sequence to form a loop.

[0039] In one of the optional technical solutions, if the DC-DC converter meets the push-pull condition, controlling the DC-DC converter to switch to a push-pull mode of closed-loop control includes:

[0040] Acquiring the output duty cycle of the DC-DC converter in real time;

[0041] If the output duty cycle of the DC-DC converter is greater than or equal to a preset duty cycle threshold, determining that the DC-DC converter meets the push-pull condition;

[0042] The DC-DC converter is controlled to switch to a push-pull mode of closed-loop control, and the bus capacitor is pre-charged in the push-pull mode.

[0043] The above technical solution has the following beneficial effects:

[0044] The precharging method of the electric vehicle provided by the present invention switches the state by reusing the original DC-DC converter of the electric vehicle to achieve the effect of precharging the high-voltage bus capacitor efficiently, smoothly and at low cost, so as to improve the user experience. When the electric vehicle is powered on, the DC-DC converter is first controlled to precharge the high-voltage bus capacitor continuously and smoothly through the forward-flyback mode. After the DC-DC converter meets the push-pull condition, the DC-DC converter is controlled to switch to the push-pull mode to precharge the high-voltage bus capacitor with high power, thereby significantly improving the efficiency of precharging.

[0045] The present invention reuses the original DC-DC converter of the electric vehicle and can pre-charge the high-voltage bus capacitor through the forward-flyback mode and the push-pull mode respectively without adding any additional pre-charging equipment or circuits. This avoids the disadvantage of the push-pull mode that a large oscillation voltage is caused when the initial current is large, and utilizes the characteristics of the smooth pre-charging start-up of the forward-flyback mode and the high pre-charging efficiency of the push-pull mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. It should be understood that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In the drawings:

[0047] Figure 1 A flowchart of a pre-charging method for an electric vehicle provided by an embodiment of the present invention;

[0048] Figure 2 is a schematic diagram of a circuit current in a first forward mode according to an embodiment of the present invention;

[0049] Figure 3 is a schematic diagram of a circuit current in a first flyback mode according to an embodiment of the present invention;

[0050] Figure 4 is a schematic diagram of a circuit current in a second forward mode according to an embodiment of the present invention;

[0051] Figure 5 is a schematic diagram of a circuit current in a second flyback mode according to an embodiment of the present invention;

[0052] Figure 6 is a schematic diagram of a circuit current in a first push-pull mode according to an embodiment of the present invention;

[0053] Figure 7 is a schematic diagram of a circuit current in a second push-pull mode according to an embodiment of the present invention;

[0054] Figure 8 is a schematic diagram of a circuit current in a third push-pull mode according to an embodiment of the present invention;

[0055] Fig. 9 is a schematic diagram of a circuit current in a fourth push-pull mode according to an embodiment of the present invention;

[0056] Fig.10 A schematic diagram of state parameter changes of a pre-charging method for an electric vehicle provided by an embodiment of the present invention;

[0057] Fig.11 A schematic diagram of state parameter changes for precharging a high-voltage bus capacitor in a push-pull manner;

[0058] Fig.12 A schematic diagram of state parameter changes for precharging a high-voltage bus capacitor in a push-pull manner with current suppression;

[0059] Fig.13 A structural diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0060] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0061] It should be noted that in the motor controller, the DC power of the power battery is used as the input power source and needs to be connected to the motor controller through a DC bus. This method is called DC support. The capacitor on the bus is the bus capacitor or support capacitor. Since the motor controller may generate very high pulse voltages on the DC support when receiving the pulse current provided by the power battery, these voltages may exceed the tolerance of the motor controller, so it is necessary to set a high-voltage bus capacitor for buffering and stabilization.

[0062] Before the electric vehicle is powered on at high voltage, the high-voltage bus capacitor needs to be pre-charged to reduce the impact current during power-on, thereby protecting the motor controller, main relay and other components from being damaged by the impact of instantaneous high current. The reverse pre-charging described below refers to pre-charging the high-voltage bus capacitor with the power of the low-voltage battery in reverse.

[0063] like Figure 1 A pre-charging method for an electric vehicle provided by an embodiment of the present invention is shown, comprising:

[0064] Step S101: receiving a vehicle power-on command, and sending a reverse pre-charging command to the DC-DC converter.

[0065] Step S102: Control the DC-DC converter to switch to the forward-flyback mode of open-loop control to pre-charge the high-voltage bus capacitor.

[0066] Step S103: If the DC-DC converter meets the push-pull condition, the DC-DC converter is controlled to switch to a push-pull mode of closed-loop control to pre-charge the high-voltage bus capacitor.

[0067] Step S104: If the high-voltage bus capacitor meets the pre-charging completion condition, the DC-DC converter is controlled to exit the reverse pre-charging mode.

[0068] When the push-pull mode is used to pre-charge the high-voltage bus capacitor, the duty cycle exceeds 0.5. Fig.11 In the case shown in the figure, if the current is not limited, the starting current of the low-voltage battery will increase sharply, which will cause the VDS oscillation voltage of the switch tube on the low-voltage side to be large. Although efficient pre-charging can be achieved, current and voltage shocks will occur in the initial stage of pre-charging, which is not conducive to the stability of the internal components of the system. Fig.12 As shown, if the push-pull mode with current limiting is adopted, the VDS oscillation voltage can be suppressed, but it will also cause the pre-charging time of the high-voltage bus capacitor to be longer, and the overall pre-charging process is not smooth, which will also affect the power-on efficiency of the electric vehicle and thus affect the user experience.

[0069] To this end, the present invention passes through the above steps, step S101 determines that the electric vehicle needs to be powered on at high voltage, and the main control module in the vehicle issues a corresponding pre-charging instruction to the DC-DC converter. It is also necessary to calculate the voltage difference between the high-voltage bus capacitor and the power battery, and if the voltage difference is greater than or equal to 10V, it is determined that the high-voltage bus capacitor needs to be pre-charged.

[0070] Step S102 controls the DC-DC converter to switch to the forward-flyback mode to perform forward-flyback continuous low-power pre-charging on the high-voltage bus capacitor, and at the same time prepares for the internal period of the DC-DC converter, so that the internal period of the DC-DC converter has enough time to prepare for the high voltage and high current of the push-pull mode, thereby avoiding the VDS oscillation voltage or damage to the internal components due to the impact of the push-pull mode when the DC-DC converter is used as a pre-charging device for the high-voltage bus capacitor.

[0071] Preferably, step S103 includes:

[0072] The output duty cycle of the DC-DC converter is obtained in real time.

[0073] If the output duty cycle of the DC-DC converter is greater than or equal to a preset duty cycle threshold, it is determined that the DC-DC converter meets the push-pull condition.

[0074] The DC-DC converter is controlled to switch to a push-pull mode of closed-loop control, and the bus capacitor is pre-charged in the push-pull mode.

[0075] Step S103 controls the DC-DC converter that meets the push-pull condition to switch to the push-pull mode, and continues to pre-charge the high-voltage bus capacitor with high efficiency in the push-pull mode. Preferably, the push-pull condition is to determine whether the duty cycle of the DC-DC converter output is greater than or equal to 0.5. When the DC-DC converter pre-charges the high-voltage bus capacitor in the forward-flyback mode, the duty cycle gradually increases from 0. When the duty cycle is greater than or equal to 0.5, it is considered that the push-pull condition has been met. At this time, the DC-DC converter will not cause the internal switch tube to have an excessive VDS oscillation voltage due to entering the push-pull mode, thereby ensuring system stability.

[0076] Step S104 detects the voltage of the high-voltage bus capacitor. When the voltage of the high-voltage bus capacitor meets the preset conditions, specifically, the voltage difference between the high-voltage bus capacitor and the power battery is less than 10V, the DC-DC converter is controlled to exit the reverse pre-charging mode, so that the DC-DC converter resumes normal current conversion and rectification functions.

[0077] As a preference, pre-charging in the push-pull mode is performed under voltage and current limiting conditions. In the push-pull mode, the pre-charging voltage is limited to a value not exceeding the voltage of the power battery.

[0078] like Fig.10 As shown, the pre-charging method of the electric vehicle provided by the embodiment of the present invention first enters the forward-flyback mode and then switches to the push-pull mode. In the early stage of pre-charging, the charging current and charging voltage in the forward-flyback mode rise rapidly to a higher level at a steady rate, and then slowly decrease until the duty cycle reaches 0.5, and the DC-DC converter is switched to the push-pull mode, and the charging voltage and charging current rise steadily again to achieve a smooth and efficient pre-charging process. During the whole process, the voltage increase rate of the high-voltage bus capacitor maintains a steady rate for faster pre-charging, and the current impact on the internal components is small, which can ensure that the DC-DC converter can maintain overall stability when used as a pre-charging device, and avoid reducing its service life and working stability due to the reuse of the DC-DC converter as a pre-charging device.

[0079] In the aforementioned method steps, the DC-DC converter realizes pre-charging mode switching through a phase-shifted full-bridge topology, wherein the phase-shifted full-bridge topology is a topology structure used in a DC-DC converter, and the core principle is to utilize the combination of phase-shifted control technology and a full-bridge converter to realize the regulation of the input voltage and the stable control of the output voltage. Compared with the traditional DC-DC converter, the DC-DC converter provided in this embodiment not only includes a phase-shifted full-bridge topology, but also adds a flyback module. Through the flyback circuit and flyback transformer T2 in the flyback module, the DC-DC converter can be switched to a forward flyback mode to pre-charge the high-voltage bus capacitor in a forward flyback mode. Through simple structural improvements, the phase-shifted full-bridge topology can be switched to a pre-charging mode at a relatively low cost, and no additional pre-charging equipment is required, which can save space in the vehicle.

[0080] In summary, the pre-charging method of an electric vehicle provided by an embodiment of the present invention realizes the effect of pre-charging the high-voltage bus capacitor efficiently, smoothly and at low cost by reusing the original DC-DC converter of the electric vehicle for state switching, so as to improve the user experience. When the electric vehicle is powered on, the DC-DC converter is first controlled to pre-charge the high-voltage bus capacitor continuously and smoothly through the forward-flyback mode. After the DC-DC converter meets the push-pull condition, the DC-DC converter is controlled to switch to the push-pull mode to pre-charge the high-voltage bus capacitor at high power, thereby significantly improving the efficiency of pre-charging.

[0081] The embodiment of the present invention reuses the original DC-DC converter of the electric vehicle and can pre-charge the high-voltage bus capacitor through the forward-flyback mode and the push-pull mode respectively without adding any additional pre-charging equipment or circuits. This avoids the disadvantage of the push-pull mode that causes a large oscillation voltage when the initial current is large, and utilizes the characteristics of smooth pre-charging start-up in the forward-flyback mode and high pre-charging efficiency in the push-pull mode.

[0082] In one embodiment, the DC-DC converter includes a phase-shifted full-bridge topology and a flyback module.

[0083] The phase-shifted full-bridge topology includes a primary module, a main transformer T1 and a secondary module connected in sequence, the secondary module is connected to a low-voltage battery, and the power battery and the high-voltage bus capacitor are respectively connected to the primary module.

[0084] The flyback module includes a flyback transformer T2 and a flyback loop connected to both ends of the high-voltage bus capacitor, and the flyback loop is connected to the secondary module through the flyback transformer T2.

[0085] In this embodiment, by adopting a DC-DC converter design combining a phase-shifted full-bridge topology and a flyback module, an efficient and flexible high-voltage bus pre-charging process is achieved. The phase-shifted full-bridge topology can provide a stable energy transmission path, while the flyback module, through its unique flyback characteristics, continues to charge the high-voltage bus capacitor during power failure, thereby improving the pre-charging efficiency. This design not only simplifies the circuit structure, but also reduces the system cost, while improving the overall performance of the electric vehicle.

[0086] In one embodiment, if Figure 2-9 As shown, the primary side module includes a bridge rectifier circuit, the secondary side circuit includes a full-wave rectifier circuit, the secondary side module can switch between a positive half-cycle output state, a negative half-cycle output state and an inductive energy storage state, and the primary side module can switch between a forward input state, a reverse input state and a power-off state.

[0087] In this embodiment, the primary module adopts a bridge rectifier circuit, and the secondary module adopts a full-wave rectifier circuit, and a flexible switching mechanism is used to achieve seamless conversion between the positive half cycle, the negative half cycle and the inductive energy storage state. This design enables the DC-DC converter to automatically adjust the working mode according to the charging state of the high-voltage bus capacitor to ensure the smooth progress of the pre-charging process. At the same time, the combination of the bridge rectifier circuit and the full-wave rectifier circuit improves the efficiency of energy conversion and reduces energy loss.

[0088] In one embodiment, the forward-flyback mode includes four operating modes that are executed in sequence in a cycle, including:

[0089] The first forward mode, such as Figure 2 As shown, the secondary module switches to the positive half-cycle output state, the primary module switches to the forward input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology.

[0090] The first flyback mode, such as Figure 3 As shown, the secondary module and the primary module are both powered off, the flyback transformer T2 is activated, and the low-voltage battery charges the high-voltage bus capacitor through the flyback circuit.

[0091] The second forward mode, such as Figure 4 As shown, the secondary module is switched to the negative half-cycle output state, the primary module is switched to the reverse input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology.

[0092] The second flyback mode, such as Figure 5 As shown, the secondary module and the primary module are both powered off, the flyback transformer T2 is activated, and the low-voltage battery charges the high-voltage bus capacitor through the flyback circuit.

[0093] In this embodiment, the four working modes of the forward-flyback mode are alternately executed to realize the interval between forward charging and flyback charging. Specifically, the first forward mode, the first flyback mode, the second forward mode and the second flyback mode are alternately executed in sequence to realize a continuous and stable pre-charging process. In the forward mode, the low-voltage battery directly charges the high-voltage bus capacitor through the phase-shifted full-bridge topology; in the flyback mode, the energy storage and release characteristics of the flyback transformer are utilized to directly charge the high-voltage bus capacitor through the flyback circuit during the power-off period of the phase-shifted full-bridge topology. Thereby achieving the effect of continuously charging the high-voltage bus capacitor in each mode. In the forward-flyback mode, when the secondary module switches the direction of the output current by changing the state of the switch tube, the state of the switch tube in the primary module is changed accordingly to change the direction of the received current, so that the current enters the high-voltage bus capacitor in the same direction.

[0094] In one embodiment, the push-pull mode includes four working modes that are executed in sequence in a cycle, including:

[0095] The first push-pull mode, such as Figure 6 As shown, the secondary side module is switched to the inductive energy storage state, and the primary side module is powered off.

[0096] The second push-pull mode, such as Figure 7 As shown, the secondary module switches to the positive half-cycle output state, the primary module switches to the forward input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology.

[0097] The third push-pull mode, such as Figure 8 As shown, the secondary side module is switched to the inductive energy storage state, and the primary side module is powered off.

[0098] The fourth push-pull mode, such as Fig. 9 As shown, the secondary module is switched to the negative half-cycle output state, the primary module is switched to the reverse input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology.

[0099] In this embodiment, the DC-DC converter is alternately executed in the four working modes of the push-pull mode, specifically, it is alternately executed in the first push-pull mode, the second push-pull mode, the third push-pull mode and the fourth push-pull mode in sequence, and the pre-charging of the high-voltage bus capacitor is achieved by accurately controlling the on and off of the switch tube. In the push-pull mode, the secondary module switches between the inductor energy storage state and the positive and negative half-cycle output states, while the primary module switches between the forward input state, the reverse input state and the power-off state. The push-pull mode can achieve a high-power charging effect for the high-voltage bus capacitor by changing the inductor energy storage and discharge state. When the secondary module switches the direction of the output current by changing the state of the switch tube, the state of the switch tube in the primary module is changed accordingly to change the direction of the received current, so that the current enters the high-voltage bus capacitor in the same direction.

[0100] In one embodiment, if Figure 2-9 As shown, C1 is a high-voltage bus capacitor, and the two ends of the power battery are connected to the two ends of the high-voltage bus capacitor through relays S1 and S2. The main transformer T1 includes a primary winding and a secondary winding, and the secondary winding includes a central terminal and two ends.

[0101] The full-wave rectifier circuit includes a switch tube Q5, a switch tube Q6, a filter inductor Lf, a leakage inductor Lk, a resistor R and a transient voltage suppressor TVS.

[0102] The central end of the secondary winding is connected to the positive electrode of the low-voltage battery, and the two ends of the secondary winding are connected to the negative electrode of the low-voltage battery through the switch tube Q5 and the switch tube Q6 respectively.

[0103] A filter inductor Lf and a leakage inductor Lk are connected in series between the positive pole of the low-voltage battery and the central end of the secondary winding. A resistor R is connected in parallel with the filter inductor Lf and the leakage inductor Lk, and a transient voltage suppressor TVS is connected in series with the resistor R. One side winding of the flyback transformer T2 is connected in parallel with the filter inductor Lf, and the other side winding of the flyback transformer T2 is connected to the flyback circuit.

[0104] In this embodiment, the central end of the secondary winding of the main transformer is connected to the positive electrode of the low-voltage battery, and the two ends are connected to the negative electrode of the low-voltage battery through the switch tube. Compared with the traditional DC-DC converter, the filter inductor Lf, leakage inductor Lk, resistor R and transient voltage suppressor TVS are added to the entire rectifier circuit to ensure that the flyback transformer can operate normally and improve the stability and safety of the circuit. The filter inductor Lf and leakage inductor Lk are used to smooth the current waveform and reduce harmonic interference; the resistor R and transient voltage suppressor TVS are used to limit overvoltage and protect the circuit from transient voltage shocks. The flyback transformer T2 is connected in parallel with the filter inductor Lf, and is connected to the flyback circuit through the other side winding, realizing the effective transfer and storage of energy.

[0105] In one embodiment, if Figure 2-5 As shown, in the forward-flyback mode, the switch tube Q5, the switch tube Q6 and the flyback transformer T2 are alternately turned on.

[0106] In the push-pull mode, the switch tube Q5 and the switch tube Q6 are alternately switched between a simultaneous conduction state and a separate conduction state.

[0107] Furthermore, in the positive half-cycle output state, the switch tube Q5 is turned off, and the switch tube Q6 is turned on.

[0108] In the negative half-cycle output state, the switch tube Q5 is turned on, and the switch tube Q6 is turned off.

[0109] In the inductor energy storage state, the switch tube Q5 and the switch tube Q6 are turned on at the same time.

[0110] In this embodiment, in the forward-flyback mode, the alternating conduction of the switch tube Q5, the switch tube Q6 and the flyback transformer T2 ensures the continuity and stability of the pre-charging process, and only one of the switch tube Q5, the switch tube Q6 and the flyback transformer T2 is turned on each time. When the flyback transformer T2 is turned on, the switch tube Q5 and the switch tube Q6 are both disconnected, and only the flyback circuit in the entire system is energized, so that the low-voltage battery charges the high-voltage bus capacitor through the flyback transformer T2 and the flyback circuit. In the push-pull mode, the switch tube Q5 and the switch tube Q6 alternate between the simultaneous conduction state and the single conduction state. When the switch tube Q5 and the switch tube Q6 are turned on at the same time, the secondary module does not transmit power to the primary module, but enters the state of filtering inductor energy storage, so that when the switch tube Q5 and the switch tube Q6 are turned on separately, a high-power charging current can be output, so as to ensure the efficiency of the pre-charging of the high-voltage bus capacitor, and ensure that the pre-charging method of switching the forward-flyback mode to the push-pull mode does not significantly reduce the pre-charging speed.

[0111] In one embodiment, the bridge rectifier circuit includes a switch tube Q1, a switch tube Q3, a switch tube Q2, a switch tube Q4, a diode D1, a diode D2, a resonant inductor Lr and a DC blocking capacitor Cb.

[0112] The high-voltage bus capacitor, the switch tube Q1 and the switch tube Q3 connected in series, the switch tube Q2 and the switch tube Q4 connected in series, and the diode D1 and the diode D2 connected in series are connected in parallel in sequence.

[0113] One end of the primary winding is connected between the switch tube Q1 and the switch tube Q3 through the resonant inductor Lr, and the other end of the primary winding is connected between the switch tube Q2 and the switch tube Q4 through the DC blocking capacitor Cb.

[0114] In this embodiment, the structure of the bridge rectifier circuit adapts the direction of the output current by switching the forward input state and the reverse input state, thereby ensuring that the charging current direction of the high-voltage bus capacitor is consistent in any state.

[0115] In one embodiment, if Figure 6-9 As shown, in the forward input state, the high-voltage bus capacitor, the switch tube Q4, the DC blocking capacitor Cb, the primary winding and the diode D1 are turned on in sequence to form a loop.

[0116] In the reverse input state, the high-voltage bus capacitor, the diode D2, the primary winding, the DC blocking capacitor Cb and the switch tube Q2 are turned on in sequence to form a loop.

[0117] In this embodiment, the DC blocking capacitor Cb ensures effective isolation of the DC component and avoids transformer bias.

[0118] In the forward input state, the high-voltage bus capacitor is charged through the loop formed by the switch tube Q4, the DC blocking capacitor Cb, the primary winding and the diode D1. At this time, the current direction of the secondary module output is positive, which is consistent with the charging direction of the high-voltage bus capacitor, realizing effective energy transfer. In the reverse input state, the high-voltage bus capacitor is charged through the loop formed by the diode D2, the primary winding, the DC blocking capacitor and the switch tube Q3 to match the reverse current direction of the secondary module output, so as to ensure that the charging current direction of the high-voltage bus capacitor is consistent in any state.

[0119] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0120] like Fig.13The figure shows a hardware structure diagram of an electronic device of the present invention, including a memory 1302, a processor 1301 and an electronic device program on the memory 1302, and the processor 1301 executes the electronic device program to implement the steps of the pre-charging method of the electric vehicle in any of the above embodiments.

[0121] Fig.13 A processor 1301 is taken as an example.

[0122] The electronic device may further include: an input device 1303 and a display device 1304 .

[0123] The processor 1301, the memory 1302, the input device 1303 and the display device 1304 may be connected via a bus or other means, and the figure takes the connection via a bus as an example.

[0124] The memory 1302 is a non-volatile electronic device readable storage medium, which can be used to store non-volatile software programs, non-volatile electronic device executable programs and modules, such as program instructions / modules corresponding to the electric vehicle pre-charging method in the embodiment of the present application. The processor 1301 executes various functional applications and data processing by running the non-volatile software programs, instructions and modules stored in the memory 1302, that is, the electric vehicle pre-charging method in the above embodiment is implemented.

[0125] The memory 1302 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created according to the use of the pre-charging method of the electric vehicle, etc. In addition, the memory 1302 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage component, a flash memory component, or other non-volatile solid-state storage components. In some embodiments, the memory 1302 may optionally include a memory remotely arranged relative to the processor 1301, and these remote memories may be connected to a device for executing the pre-charging method of the electric vehicle via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0126] The input device 1303 may receive inputted user clicks and generate signal inputs related to user settings and function control of the pre-charging method of the electric vehicle. The display device 1304 may include display devices such as a display screen.

[0127] The one or more modules are stored in the memory 1302 , and when executed by the one or more processors 1301 , the pre-charging method for an electric vehicle in any of the above method embodiments is executed.

[0128] When the electronic device disclosed by the present invention is in operation, it can execute all the steps of the above-mentioned precharging method of the electric vehicle, and by reusing the original DC-DC converter of the electric vehicle, the high-voltage bus capacitor is precharged in the forward-flyback mode before the DC-DC converter meets the push-pull condition, and after the DC-DC converter meets the push-pull condition, the DC-DC converter is switched to the push-pull mode to precharge the high-voltage bus capacitor. By reusing the original DC-DC converter of the electric vehicle, the high-voltage bus capacitor can be precharged in the forward-flyback mode and the push-pull mode respectively without adding additional precharging equipment or circuits, which not only avoids the disadvantage of the push-pull mode causing a large oscillation voltage when the initial current is large, but also utilizes the characteristics of the smooth start of the forward-flyback mode precharging, and the characteristics of the high precharging efficiency of the push-pull mode, so as to achieve the purpose of completing the precharging of the high-voltage bus capacitor efficiently, smoothly and at low cost.

[0129] An embodiment of the present invention provides an electronic device readable storage medium, which stores an electronic device program / instruction. When the electronic device program / instruction is executed by the processor 1301, all steps of the electric vehicle pre-charging method as described above are implemented.

[0130] In the context of the present disclosure, a storage medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or apparatus. The storage medium may be a machine-readable signal medium or a machine-readable storage medium. Alternatively, the storage medium may be a non-temporary electronic device readable storage medium, for example, a non-temporary electronic device readable storage medium may be a ROM, a random access memory (Random Access Memory, RAM), a compact disc read-only memory (Compact Disc ROM, CD-ROM), a magnetic tape, a floppy disk, and an optical data storage device, etc.

[0131] An embodiment of the present invention provides an electronic device program product, including an electronic device program / instruction, which implements the steps of the electric vehicle pre-charging method as described above when executed by a processor.

[0132] By running the electronic device program product, all steps of the pre-charging method of the electric vehicle as described above can be executed, and by reusing the original DC-DC converter of the electric vehicle, the high-voltage bus capacitor is pre-charged in a forward-flyback mode before the DC-DC converter meets the push-pull condition, and after the DC-DC converter meets the push-pull condition, the DC-DC converter is switched to a push-pull mode to pre-charge the high-voltage bus capacitor. By reusing the original DC-DC converter of the electric vehicle, the high-voltage bus capacitor can be pre-charged in a forward-flyback mode and a push-pull mode respectively without adding additional pre-charging equipment or circuits, which avoids the disadvantage of the push-pull mode causing a large oscillation voltage when the initial current is large, and utilizes the characteristics of the smooth start of the pre-charging in the forward-flyback mode, and the high pre-charging efficiency in the push-pull mode, so as to achieve the purpose of completing the pre-charging of the high-voltage bus capacitor efficiently, smoothly and at low cost.

[0133] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A pre-charging method for an electric vehicle, It is characterized in that include: Upon receiving a vehicle power-on command, a reverse pre-charge command is issued to the DC-DC converter; Controlling the DC-DC converter to switch to the forward-flyback mode of open-loop control to pre-charge the high-voltage bus capacitor; If the DC-DC converter meets the push-pull condition, controlling the DC-DC converter to switch to a push-pull mode of closed-loop control to pre-charge the high-voltage bus capacitor; If the high-voltage bus capacitor meets the pre-charging completion condition, the DC-DC converter is controlled to exit the reverse pre-charging mode.

2. The pre-charging method of an electric vehicle according to claim 1, It is characterized in that The DC-DC converter includes a phase-shifted full-bridge topology and a flyback module; The phase-shifted full-bridge topology includes a primary module, a main transformer T1 and a secondary module connected in sequence, the secondary module is connected to a low-voltage battery, and the power battery and the high-voltage bus capacitor are respectively connected to the primary module; The flyback module includes a flyback transformer T2 and a flyback loop connected to both ends of the high-voltage bus capacitor, and the flyback loop is connected to the secondary module through the flyback transformer T2.

3. The pre-charging method of an electric vehicle according to claim 2, It is characterized in that The primary side module includes a bridge rectifier circuit, the secondary side circuit includes a full-wave rectifier circuit, the secondary side module can switch between a positive half-cycle output state, a negative half-cycle output state and an inductive energy storage state, and the primary side module can switch between a forward input state, a reverse input state and a power-off state.

4. The pre-charging method of an electric vehicle according to claim 3, Features: The forward-flyback mode includes four working modes that are executed in sequence, including: In the first forward mode, the secondary module switches to the positive half-cycle output state, the primary module switches to the forward input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology; In the first flyback mode, the secondary module and the primary module are both powered off, the flyback transformer T2 is activated, and the low-voltage battery charges the high-voltage bus capacitor through the flyback circuit; In the second forward mode, the secondary module switches to the negative half-cycle output state, the primary module switches to the reverse input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology; In the second flyback mode, the secondary module and the primary module are both powered off, the flyback transformer T2 is activated, and the low-voltage battery charges the high-voltage bus capacitor through the flyback circuit.

5. The pre-charging method of the electric vehicle according to claim 3, Features: The push-pull mode includes four working modes that are executed in sequence and in a cycle, including: In the first push-pull mode, the secondary side module is switched to the inductive energy storage state, and the primary side module is powered off; In the second push-pull mode, the secondary module switches to the positive half-cycle output state, the primary module switches to the forward input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology; In the third push-pull mode, the secondary module is switched to the inductive energy storage state, and the primary module is powered off; In the fourth push-pull mode, the secondary module is switched to the negative half-cycle output state, the primary module is switched to the reverse input state, and the low-voltage battery charges the high-voltage bus capacitor through the phase-shifted full-bridge topology.

6. The pre-charging method of an electric vehicle according to claim 3, Features: The main transformer T1 includes a primary winding and a secondary winding, and the secondary winding includes a central end and two ends; The full-wave rectifier circuit includes a switch tube Q5, a switch tube Q6, a filter inductor Lf, a leakage inductor Lk, a resistor R and a transient voltage suppressor TVS; The central end of the secondary winding is connected to the positive electrode of the low-voltage battery, and the two ends of the secondary winding are connected to the negative electrode of the low-voltage battery through the switch tube Q5 and the switch tube Q6 respectively; A filter inductor Lf and a leakage inductor Lk are connected in series between the positive pole of the low-voltage battery and the central end of the secondary winding. A resistor R is connected in parallel with the filter inductor Lf and the leakage inductor Lk, and a transient voltage suppressor TVS is connected in series with the resistor R. One side winding of the flyback transformer T2 is connected in parallel with the filter inductor Lf, and the other side winding of the flyback transformer T2 is connected to the flyback circuit.

7. The pre-charging method of an electric vehicle according to claim 6, Features: In the forward-flyback mode, the switch tube Q5, the switch tube Q6 and the flyback transformer T2 are alternately turned on; In the push-pull mode, the switch tube Q5 and the switch tube Q6 are alternately switched between a simultaneous conduction state and a separate conduction state.

8. The pre-charging method of an electric vehicle according to claim 6, Features: In the positive half-cycle output state, the switch tube Q5 is turned off and the switch tube Q6 is turned on; In the negative half-cycle output state, the switch tube Q5 is turned on and the switch tube Q6 is turned off; In the inductor energy storage state, the switch tube Q5 and the switch tube Q6 are turned on at the same time.

9. The pre-charging method of an electric vehicle according to claim 6, Features: The bridge rectifier circuit includes a switch tube Q1, a switch tube Q3, a switch tube Q2, a switch tube Q4, a diode D1, a diode D2, a resonant inductor Lr and a DC blocking capacitor Cb; The high-voltage bus capacitor, the switch tube Q1 and the switch tube Q3 connected in series, the switch tube Q2 and the switch tube Q4 connected in series, and the diode D1 and the diode D2 connected in series are sequentially connected in parallel; One end of the primary winding is connected between the switch tube Q1 and the switch tube Q3 through the resonant inductor Lr, and the other end of the primary winding is connected between the switch tube Q2 and the switch tube Q4 through the DC blocking capacitor Cb.

10. The pre-charging method of an electric vehicle according to claim 9, Features: In the forward input state, the high-voltage bus capacitor, the switch tube Q4, the DC blocking capacitor Cb, the primary winding and the diode D1 are turned on in sequence to form a loop; In the reverse input state, the high-voltage bus capacitor, the diode D2, the primary winding, the DC blocking capacitor Cb and the switch tube Q2 are turned on in sequence to form a loop.

11. The pre-charging method of an electric vehicle according to claim 1, It is characterized in that If the DC-DC converter satisfies the push-pull condition, controlling the DC-DC converter to switch to a push-pull mode of closed-loop control comprises: Acquiring the output duty cycle of the DC-DC converter in real time; If the output duty cycle of the DC-DC converter is greater than or equal to a preset duty cycle threshold, determining that the DC-DC converter meets the push-pull condition; The DC-DC converter is controlled to switch to a push-pull mode of closed-loop control, and the bus capacitor is pre-charged in the push-pull mode.

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