High voltage direct current fast charging system and method based on inductive energy extraction

Abstract

This invention discloses a high-voltage DC fast charging system and method based on inductor-based energy extraction, comprising a front-end rectification and energy replenishment module and a back-end charging and energy harvesting module. The rectification and energy replenishment module includes an AC rectifier circuit, a DC voltage divider circuit, and an energy replenishment circuit. The charging and energy harvesting module includes an energy harvesting inductor and a chopper switch. Specifically, the DC voltage output of the AC rectifier circuit is connected to the DC voltage divider circuit, and the energy replenishment circuit is connected in parallel with the DC voltage divider circuit to charge and replenish the DC voltage divider circuit through external pulse width modulation. The energy harvesting inductor is connected to the DC voltage divider circuit to extract energy, and the output charging current is controlled by the operation of the chopper switch.

Description

Technical Field

[0001] This invention relates to the field of power electronics and electric transportation vehicle charging technology, specifically to a high-voltage DC fast charging system and method based on inductive energy extraction. Background Technology

[0002] As the range of electric vehicles, ships, and other transportation vehicles continues to improve, the capacity of large automotive battery systems is gradually increasing to 180kWh and above, while that of marine battery systems is gradually increasing to 1900kWh and above. DC voltage is also gradually rising to 1000V or 1500V platforms. However, traditional DC fast charging systems typically operate at 400V or 800V DC platforms, with rated power mostly at 120kW or 250kW, which is insufficient to meet the energy replenishment needs of large-capacity, high-voltage batteries in a short time (e.g., 10 minutes). For example, traditional low-voltage AC input solutions generally use similar... Figure 1 The principle is as follows: the voltage is stepped down by the power frequency transformer, and the low-voltage AC enters the PWM rectifier to charge the battery. This method is suitable for lower battery voltages. If the battery has a large charge, the current will be very large. Usually, devices or modules need to be connected in parallel, but this will cause serious heat generation and thicker wires. As a result, the charging power and charging speed are limited.

[0003] High-voltage direct connection technology eliminates the need for a power frequency step-down transformer, allowing direct connection to the power grid. Existing high-voltage direct connection technologies generally employ similar methods. Figure 2 The principle is as follows: N H-bridge modules are connected in series in each of the three phases A, B, and C (typical value: 8-12 per phase, total 24-36 modules). The three-phase star or delta connection (CHB) is then directly connected to the 10kV power grid. A dual active bridge converter (DAB) receives the high-voltage DC output from the CHB modules, achieving electrical isolation, voltage level conversion, and bidirectional power transmission (supporting V2G). A DC / DC converter converts the DC output from the DAB into a wide-range adjustable voltage / current required by the battery, enabling precise charging control. However, this high-voltage direct connection technology also has many drawbacks, such as system complexity, high module cost, difficulty in voltage and current sharing among multiple modules, high control complexity, the need to coordinate carrier phase shift (CHB), phase shift control (DAB), and current sharing control (DC-DC), and high requirements for controller computing power. The reason is that the DAB itself is a dual active full-bridge circuit with many components. In addition, the CHB and DC / DC are both active modules. The superposition of three active modules inevitably makes the system complex and the module cost high. Moreover, the CHB requires grid-side current loop, module voltage equalization, and zero-sequence / differential mode control, the DAB requires phase-shift control, soft-switching range, and power balance, and the DC / DC requires constant current and constant voltage, current limiting protection. The closed-loop coupling control between the three active modules results in high control complexity, high computing power requirements, and long debugging cycle.

[0004] In related technologies, patent application CN118713158A addresses the issue of hybrid energy storage by dividing the DC voltage through an inductor connected in series with N SM modules. Each SM module consists of a bidirectional DC-DC converter, and a supercapacitor is incorporated within each SM module to smooth out instantaneous power fluctuations, absorb inrush currents, and protect the battery from prolonged high-power energy throughput. However, due to the series connection of the SM modules, the batteries are effectively separated and connected in series within each module, resulting in a relatively low voltage level for each battery. In contrast, patent application CN105207476A proposes a capacitor-based voltage divider for DC-DC conversion, focusing on high-voltage DC voltage division. This involves using multiple capacitors for equal voltage division, and the auxiliary circuit includes six switching transistors alternately connected to inductors. This approach, however, involves a more complex control process for the high-voltage DC transformer.

[0005] In summary, to address the issues of low power density and high system complexity in the existing technologies and to achieve an ultra-fast charging experience for large-capacity, high-voltage batteries, there is an urgent need for a relatively simplified, high-power-density, megawatt-level high-voltage DC fast charging solution. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to achieve high-voltage DC fast charging of large-capacity, high-voltage batteries.

[0007] The present invention solves the above-mentioned technical problems through the following technical means:

[0008] A high-voltage DC fast charging system based on inductor-based energy extraction is proposed, comprising a front-end rectifier and energy replenishment module and a back-end charging and energy harvesting module. The rectifier and energy replenishment module includes an AC rectifier circuit, a DC voltage divider circuit, and an energy replenishment circuit. The charging and energy harvesting module includes an energy harvesting inductor and a chopper switch, wherein: The DC voltage output of the AC rectifier circuit is connected to the DC voltage divider circuit, and the power supply circuit is connected in parallel with the DC voltage divider circuit to charge and replenish the DC voltage divider circuit through external pulse width modulation. The energy extraction inductor is connected to the DC voltage divider circuit to extract energy, and the output charging current is controlled by the operation of the chopper switch.

[0009] Furthermore, the AC rectifier circuit includes an AC circuit breaker and a three-phase rectifier bridge, wherein the three-phase AC power is input to the three-phase rectifier bridge via the AC circuit breaker to be converted into DC power output.

[0010] Furthermore, the DC voltage divider circuit includes a capacitor branch formed by several high-voltage capacitors connected in series and a resistor branch formed by several resistors connected in series. The resistor branch is connected in parallel with the capacitor branch, and the number of high-voltage capacitors in the capacitor branch is the same as the number of resistors in the resistor branch.

[0011] Furthermore, the high-voltage capacitor at the end of the capacitor branch is a large-capacity high-voltage capacitor, while the other high-voltage capacitors in the capacitor branch are small-capacity high-voltage capacitors; the capacitance value of the large-capacity high-voltage capacitor is much larger than that of the small-capacity high-voltage capacitor.

[0012] Furthermore, the power replenishment circuit includes the same number of switching transistors as the small-capacity high-voltage capacitors in the capacitor branch, with each switching transistor connected in series and then connected to the two ends of the corresponding small-capacity high-voltage capacitor.

[0013] Furthermore, the source and drain of each switch are connected to the two ends of a corresponding small-capacity high-voltage capacitor and a resistor, respectively, and the gate of each switch is used to receive the power-up PWM drive signal.

[0014] Furthermore, the positive terminal of the high-voltage capacitor at the end of the capacitor branch serves as a reference energy node. One end of the energy harvesting inductor is connected to the reference energy node via a DC circuit breaker to extract and store energy. The chopper switch is connected between the other end of the energy harvesting inductor and the negative terminal of the high-voltage capacitor at the end of the branch. The anode of the anti-reverse diode is connected to the other end of the energy-collecting inductor, the cathode of the anti-reverse diode is connected to one end of the capacitor, the other end of the capacitor is connected to the negative terminal of the high-voltage capacitor in the final stage, and the capacitor is connected in parallel with the battery to be charged.

[0015] Furthermore, the source of the chopper switch is connected to one end of the energy harvesting inductor, the drain of the chopper switch is connected to the negative terminal of the high-voltage capacitor in the final stage via a DC circuit breaker, and the gate of the chopper switch is used to receive the charging PWM drive signal.

[0016] Furthermore, the positive terminal of the high-voltage capacitor at the end of the capacitor branch serves as a reference energy node. One end of the energy harvesting inductor is connected to the reference energy node via a DC circuit breaker to extract and store energy. A chopper switch is connected in series between the reference energy node and the energy harvesting inductor. The cathode of the reverse protection diode is connected to one end of the energy harvesting inductor, and the anode of the reverse protection diode is connected to the negative terminal of the high-voltage capacitor at the end of the branch. The other end of the energy harvesting inductor is connected to a capacitor connected in parallel across the two ends of the battery to be charged.

[0017] Furthermore, the source of the chopper switch is connected to the reference energy node via a DC circuit breaker, the drain of the chopper switch is connected to one end of the energy harvesting inductor, and the gate of the chopper switch is used to receive the charging PWM drive signal.

[0018] Furthermore, the front-end rectifier and power replenishment module can be configured to have a single-gun front-end capacity or a substation-level capacity.

[0019] Furthermore, this invention also proposes a control method for a high-voltage DC fast charging system based on inductive energy extraction, the method comprising: When the high-voltage AC input is connected, the high-voltage AC power is converted into high-voltage DC power through the AC rectifier circuit and output to the DC voltage divider circuit; The charging power harvesting module of the later stage is connected to the device to be charged and enters the constant current charging mode. The current error signal is calculated based on the current setpoint and the effective current value sampled in real time on the device to be charged. The first charging PWM drive signal is generated based on the current error signal to control the duty cycle of the chopper switch so that the charging current output by the power harvesting inductor is kept at the set constant current reference value. The difference between the actual voltage of the DC voltage divider circuit and the voltage setting threshold is used to generate a supplementary PWM drive signal, and the supplementary PWM drive signal is used to control the supplementary circuit to charge and supplement the DC voltage divider circuit.

[0020] Furthermore, the method also includes: When the voltage across the device to be charged reaches the set threshold, the charging mode switches from constant current charging mode to constant voltage charging mode. The voltage error signal is calculated based on the real-time detected voltage across the device and the voltage setpoint. A second charging PWM drive signal is generated based on the voltage error signal to control the duty cycle of the chopper switch so that the charging current output by the energy harvesting inductor is reduced.

[0021] Furthermore, the method also includes: The switching transistors in the energy replenishment circuit are synchronously driven according to the energy replenishment PWM drive signal, so as to adjust the conduction time of each switching transistor to charge the final high-voltage capacitor in the energy storage circuit.

[0022] The advantages of this invention are: (1) The present invention sets up a front-end rectifier and energy replenishment module and a back-end charging and energy harvesting module. The front-end adopts high-voltage direct-connected rectification technology, which can directly connect to the AC power grid without the need for a power frequency step-down transformer, and converts the AC voltage into DC voltage output to the DC voltage divider circuit. The energy harvesting inductor in the back-end charging and energy harvesting module directly connects to the DC voltage divider circuit to extract and store energy. When the device to be charged is being charged, the energy is transferred in a controlled manner through the high-frequency switching action of the chopper switch, thereby completing the high-voltage DC fast charging. Since the energy harvesting inductor will cause the voltage of the DC voltage divider circuit to drop, the external pulse width modulation is used to drive the energy replenishment circuit to charge and replenish the DC voltage divider circuit to maintain its constant voltage and ensure the power balance between the front and back stages. The present invention does not require a large number of cascaded H-bridges and DC / DC converters composed of power electronics. The structure and control of the designed high-voltage DC fast charging system are simpler. It can meet the fast charging requirements of DC high-voltage battery platforms and provides a new system solution for large-capacity and ultra-fast charging. It has good engineering feasibility and scalability and is suitable for large-scale deployment.

[0023] (2) In the DC voltage divider circuit, high voltage capacitors with different capacitance values ​​are set to form capacitor branches to achieve unequal voltage division. The capacitance value of the final high voltage capacitor is much larger than that of the small high voltage capacitor, so the initial voltage of the final high voltage capacitor can be set at about 800V, which greatly facilitates the selection of subsequent circuit components. Moreover, there is no need to use a dual active DAB system for voltage level conversion, which simplifies the structure, makes component selection easy, and makes control less complicated.

[0024] (3) Since the voltage of the final high-voltage capacitor will drop rapidly after outputting energy, and the capacitor is AC-passing and DC-blocking, this design cleverly uses a series of switching transistors to form a power replenishment circuit to charge the final high-voltage capacitor with high-frequency pulses.

[0025] (4) The front and rear stages of the high voltage DC fast charging system designed in this invention can be separated. The front stage can complete the single-gun port capacity or large-capacity substation level, and the rear stage DC is directly led out to the charging pile level. It can be designed according to the capacity of each gun port, which is more flexible and has a higher cost performance.

[0026] (5) The present invention controls the duty cycle of the two control sections of the high voltage DC fast charging system in real time by monitoring and comparing the production duty cycle, and drives the switching transistors of the front and rear stages through the PI regulator to maintain the power balance between the front and rear stages of the system, thereby realizing MW-level power charging.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] Figure 1 This is a schematic diagram of the traditional low-voltage AC input principle mentioned in the background section of this invention; Figure 2 This is a schematic diagram of the principle of traditional high-voltage direct connection technology mentioned in the background section of this invention; Figure 3 This is a schematic diagram of a high-voltage DC fast charging system based on inductive energy extraction, according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the chopper K connected in series in the charging circuit in one embodiment of the present invention; Figure 5 This is a schematic diagram of the capacity configuration of the front-end rectification and power supply module in one embodiment of the present invention; Figure 6 This is a schematic diagram of a simulation circuit built in one embodiment of the present invention; Figure 7 This is a schematic diagram of the simulation result waveform of the simulation circuit in one embodiment of the present invention; Figure 8 This is a flowchart illustrating a control method for a high-voltage DC fast charging system based on inductive energy extraction, as proposed in an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0031] like Figure 3 As shown, the first embodiment of the present invention proposes a high-voltage DC fast charging system based on inductor-based energy extraction, including a front-end rectifier and energy replenishment module 10 and a back-end charging and energy harvesting module 20. The rectifier and energy replenishment module 10 includes an AC rectifier circuit, a DC voltage divider circuit, and an energy replenishment circuit. The charging and energy harvesting module 20 includes an energy harvesting inductor and a chopper switch, wherein: The DC voltage output of the AC rectifier circuit is connected to the DC voltage divider circuit, and the power supply circuit is connected in parallel with the DC voltage divider circuit to charge and replenish the DC voltage divider circuit through external pulse width modulation. The energy extraction inductor is connected to the DC voltage divider circuit to extract energy, and the output charging current is controlled by the operation of the chopper switch.

[0032] It should be noted that the three-phase AC power is converted into high-voltage DC power by the front-end rectifier and power supply module. The high-voltage DC power is then divided by a DC voltage divider circuit. The energy harvesting inductor is connected to the DC voltage divider circuit to extract energy. The chopper switch is driven by an external pulse width modulation (PWM) signal to switch on and off at high frequency, and the current is obtained from the energy harvesting inductor to complete the rapid charging of the battery. Since the voltage of the DC voltage divider circuit drops during the charging process, the power supply circuit replenishes the DC voltage divider circuit with energy to maintain its voltage constant and ensure the power balance between the front and rear stages.

[0033] As a further preferred technical solution, the AC rectifier circuit includes an AC circuit breaker and a three-phase rectifier bridge, wherein the three-phase AC power is input to the three-phase rectifier bridge via the AC circuit breaker to be converted into DC power output.

[0034] Specifically, such as Figure 3 As shown, 10kV three-phase AC power enters the system through AC circuit breaker ACCB, and is converted into high-voltage DC power of about 14kV by a three-phase rectifier bridge formed by six-phase diodes D1 to D6.

[0035] As a further preferred technical solution, the DC voltage divider circuit includes a capacitor branch formed by several high-voltage capacitors connected in series and a resistor branch formed by several resistors connected in series. The resistor branch is connected in parallel with the capacitor branch, and the number of high-voltage capacitors in the capacitor branch is the same as the number of resistors in the resistor branch.

[0036] Specifically, such as Figure 3 As shown, this embodiment uses four high-voltage capacitors C1, C2, C3, and C4 connected in series to form a capacitor branch, and four resistors R1, R2, R3, and R4 connected in series to form a resistor branch. The resistor branch and the capacitor branch are connected in parallel, and the high-voltage DC current is divided by the high-voltage capacitors C1, C2, C3, and C4. The resistor branch serves as a protective measure to make the DC voltage divider circuit safer.

[0037] As a further preferred technical solution, the high-voltage capacitor at the end of the capacitor branch is a large-capacity high-voltage capacitor, while the other high-voltage capacitors in the capacitor branch are small-capacity high-voltage capacitors; the capacitance value of the large-capacity high-voltage capacitor is much larger than that of the small-capacity high-voltage capacitor.

[0038] Specifically, to ensure a lower voltage for the subsequent charging and energy harvesting module, facilitating design and control, and particularly in the selection of the chopper switch K (eliminating the need for series connection and easy duty cycle selection), this embodiment sets high-voltage capacitors C1+C2+C3 to withstand a higher voltage, while the final-stage high-voltage capacitor C4 withstands a lower voltage (not exceeding 800V) as an energy pool. Therefore, the capacitance of high-voltage capacitor C4 is much larger than that of high-voltage capacitors C1, C2, and C3. For example, consider a set of parameters: , , .

[0039] It should be noted that this embodiment achieves unequal voltage division by setting high-voltage capacitors with different capacitance values ​​in the DC voltage divider circuit to form capacitor branches. The capacitance value of the final high-voltage capacitor is set to be much larger than that of the small-capacity high-voltage capacitor, which can establish the initial voltage of the final high-voltage capacitor at about 800V. This greatly facilitates the selection of subsequent circuit components and eliminates the need to use a dual active DAB system for voltage level conversion, making the structure simple, the components easy to select, and the control uncomplicated.

[0040] As a further preferred technical solution, the power replenishment circuit includes the same number of switching transistors as the small-capacity high-voltage capacitors in the capacitor branch, with each switching transistor connected in series and then connected to the two ends of the corresponding small-capacity high-voltage capacitor.

[0041] Specifically, such as Figure 3As shown, this embodiment uses three switching transistors K1, K2, and K3 connected in series to form a power replenishment circuit. The source of switching transistor K1 is connected to the positive terminal of capacitor C1 and one end of resistor R1, and the drain is connected to the negative terminal of capacitor C1 and the other end of resistor R1. The source of switching transistor K2 is connected to the positive terminal of capacitor C2 and one end of resistor R2, and the drain is connected to the negative terminal of capacitor C2 and the other end of resistor R2. The source of switching transistor K3 is connected to the positive terminal of capacitor C3 and one end of resistor R3, and the drain is connected to the negative terminal of capacitor C3 and the other end of resistor R3. The drain of switching transistor K1 is connected to the source of switching transistor K2, and the drain of switching transistor K2 is connected to the source of switching transistor K3. The gates of switching transistors K1, K2, and K3 are used to receive the power replenishment PWM drive signal, and are switched on and off at high frequency under the drive of the external pulse width modulation PWM signal to replenish energy to capacitor C4.

[0042] Since the voltage of the high-voltage capacitor C4 drops rapidly after it outputs energy, and the capacitor is AC-passing and DC-blocking, this embodiment cleverly uses the switching transistors K1, K2, and K3 to charge C4 with high-frequency pulses.

[0043] As a further preferred technical solution, the positive terminal of the high-voltage capacitor at the end of the capacitor branch serves as a reference energy node. One end of the energy harvesting inductor is connected to the reference energy node via a DC circuit breaker for extracting and storing energy. A chopper switch is connected between the other end of the energy harvesting inductor and the negative terminal of the high-voltage capacitor at the end of the branch. The anode of the reverse protection diode is connected to the other end of the energy harvesting inductor, and the cathode of the reverse protection diode is connected to one end of the capacitor. The other end of the capacitor is connected to the negative terminal of the high-voltage capacitor at the end of the branch, and the capacitor is connected in parallel with the battery to be charged.

[0044] The source of the chopper switch is connected to one end of the power inductor, the drain of the chopper switch is connected to the negative terminal of the high-voltage capacitor in the final stage via a DC circuit breaker, and the gate of the chopper switch is used to receive the charging PWM drive signal.

[0045] Specifically, such as Figure 3 As shown, high-voltage capacitor C4 serves as a high-frequency energy pool and node voltage source. The positive terminal of high-voltage capacitor C4 is used as a 1kV reference energy node. Energy harvesting inductor L1 is connected to the reference energy node in the DC voltage divider circuit to extract and store energy. Chopper switch K is connected in parallel in the energy harvesting and charging circuit. Specifically, chopper switch K is connected between the negative terminal of inductor L1 and high-voltage capacitor C4. High-frequency switching is achieved by chopper switch K under the drive of an external pulse width modulation (PWM) signal. Through high-frequency switching ("breathing") and reverse protection diode VD, megawatt-level energy is transferred in a controlled manner. Current continuously charges the battery from L1, thereby completing high-voltage DC fast charging.

[0046] It should be noted that in this embodiment, the inductor L1 in the subsequent charging and energy harvesting module is not used for filtering, but rather as an energy storage element. It cleverly harvests energy from the reference energy node of the high-voltage capacitor C4, so that there is no need to add a DC / DC converter to work with the battery. Instead, the goal of energy harvesting, energy storage, and charging is achieved directly through the "breathing" of the inductor L1 in conjunction with the chopper switch K.

[0047] As a further preferred technical solution, such as Figure 4 As shown, the chopper switch K can also be connected in series in the energy harvesting and charging circuit. The positive terminal of the high-voltage capacitor at the end of the capacitor branch serves as the reference energy node. One end of the energy harvesting inductor is connected to the reference energy node via a DC circuit breaker to extract and store energy. The chopper switch is connected in series between the reference energy node and the energy harvesting inductor. The cathode of the reverse protection diode is connected to one end of the energy harvesting inductor, and the anode of the reverse protection diode is connected to the negative terminal of the high-voltage capacitor at the end of the circuit. The other end of the energy harvesting inductor is connected to the capacitor connected in parallel across the battery to be charged.

[0048] The source of the chopper switch is connected to the reference energy node via a DC circuit breaker, the drain of the chopper switch is connected to one end of the energy harvesting inductor, and the gate of the chopper switch is used to receive the charging PWM drive signal.

[0049] Furthermore, this embodiment can be configured with a first PI regulator and a second PI regulator. The input of the first PI regulator is the actual voltage of the high-frequency energy pool and the voltage setting threshold. The output of the first PI regulator is connected to the gates of switching transistors K1, K2, and K3, respectively. The first PI regulator performs PI regulation based on the difference between the actual voltage of the high-frequency energy pool and the voltage setting threshold, and outputs a supplementary energy PWM drive signal to synchronously drive and adjust the conduction time of switching transistors K1, K2, and K3 to supplement energy to the high-frequency energy pool. During the constant current charging stage, the input of the second PI regulator is the real-time sampled current and the current setpoint from the device to be charged. During the constant voltage charging stage, the input of the second PI regulator is the real-time sampled voltage and the voltage setpoint from the device to be charged. The output of the second PI regulator is connected to the gate of the chopper switch. The second PI regulator performs PI calculation based on the current difference between the real-time sampled current and the current setpoint from the device to be charged, or performs PI calculation based on the voltage difference between the real-time sampled voltage and the voltage setpoint from the device to be charged, generating a charging PWM drive signal to drive the chopper switch to charge the device under test.

[0050] It should be noted that, as Figure 2 As shown in Table 1, the components in the high-voltage DC fast charging system based on inductive energy extraction proposed in this embodiment are described as follows: Table 1

[0051] The high-voltage DC fast charging system based on inductive energy extraction mainly includes: charging circuit: C4 → L1 → K → VD → battery; energy replenishment circuit: K1, K2, K3 → C4; rectifier circuit: ABC → D1~D6 → 14kV.

[0052] The specific implementation process of charging using the high-voltage DC fast charging system based on inductive energy extraction proposed in this embodiment includes: During system startup, the high-voltage AC input is connected, the rectifier unit outputs high-voltage DC power, and charges the voltage divider capacitors.

[0053] During the charging phase, the duty cycle of the high-voltage DC chopper K is first controlled to keep the output charging current at the set constant current reference value; when the battery terminal voltage is detected to reach the set threshold, the control mode is switched from constant current mode to constant voltage mode.

[0054] During the energy replenishment phase, the capacitor voltage drops due to energy extraction from the inductor. K1, K2, and K3 then charge the capacitor using high-frequency pulses to replenish its energy.

[0055] As a further preferred technical solution, the front-end rectifier and power replenishment module can be configured with a single-gun front-end capacity or a substation-level capacity.

[0056] Specifically, such as Figure 5 As shown, in the high-voltage DC fast charging system based on inductive energy extraction proposed in this embodiment, the front-end and back-end hardware and control systems are independent. The front-end can be configured as a single-gun front-end system in a 1:1 ratio. Figure 5 (b) can also be configured as a high-capacity, substation-level system with multiple guns (e.g., a 1:10 system). Figure 5 (a)). The DC output to the charging pile can be directly led out, and the design can be based on the capacity of each single charging port, which is more flexible and cost-effective. The 1:N configuration method is more advantageous for large-scale sites, including in terms of land area and initial investment.

[0057] This embodiment demonstrates building a simulation circuit in MATLAB-SimLink, as follows: Figure 6 As shown, Figure 6 The circuit and component parameters are consistent with those in Table 1 above.

[0058] Control section: The control signals of the three series-connected switching transistors K1, K2, and K3 are the same. They are powered by a 20kHz pulse signal to provide high-frequency switching power to C4 and stabilize the voltage of capacitor C4. The charging power extraction logic is to subtract the voltage set value from the detected value and then use a PI regulator to adjust the duty cycle of the output to control the switching transistor K to charge the battery.

[0059] During the charging process, a constant current mode is initially used. When the battery's SOC reaches 80%, a constant voltage mode is switched, i.e., CC → CV mode. Constant current charging involves subtracting the current setpoint from the detected value, and then using a PI controller to adjust the output duty cycle to control the voltage of the capacitor connected in parallel with the battery, thus indirectly controlling the current magnitude. Similarly, constant voltage charging involves subtracting the voltage setpoint from the detected value, and then using a PI controller to adjust the output duty cycle to control the voltage of the capacitor connected in parallel with the battery.

[0060] The simulation result waveform is shown as follows Figure 7 As shown, where Figure 7 (a) in the figure is the battery SOC curve; Figure 7 (b) in the diagram is the battery charging current waveform. Figure 7 (c) in the diagram is the battery voltage waveform; Figure 7 (c) in the figure represents the charging power waveform. Observing the charging power waveform, the instantaneous power reaches 1MW, which basically meets the design requirements.

[0061] In addition, such as Figure 8 As shown, the second embodiment of the present invention also proposes a control method for a high-voltage DC fast charging system based on inductive energy extraction, which includes the following steps: S1. Connect the high-voltage AC input, and convert the input high-voltage AC power into high-voltage DC power through the AC rectifier circuit and output it to the DC voltage divider circuit; S2. Connect the charging power harvesting module of the later stage to the device to be charged and enter the constant current charging mode. Calculate the current error signal based on the current setpoint and the effective current value sampled in real time on the device to be charged. Generate the first charging PWM drive signal based on the current error signal to control the duty cycle of the chopper switch so that the charging current output by the power harvesting inductor is kept at the set constant current reference value. S3. Generate a supplementary energy PWM drive signal based on the difference between the actual voltage of the DC voltage divider circuit and the voltage setting threshold, and control the supplementary energy circuit to charge and supplement the DC voltage divider circuit based on the supplementary energy PWM drive signal.

[0062] As a further preferred technical solution, the method further includes: When the voltage across the device to be charged reaches the set threshold, the charging mode switches from constant current charging mode to constant voltage charging mode. The voltage error signal is calculated based on the real-time detected voltage across the device and the voltage setpoint. A second charging PWM drive signal is generated based on the voltage error signal to control the duty cycle of the chopper switch so that the charging current output by the energy harvesting inductor is reduced.

[0063] As a further preferred technical solution, the method further includes: The switching transistors in the energy replenishment circuit are synchronously driven according to the energy replenishment PWM drive signal, so as to adjust the conduction time of each switching transistor to charge the final high-voltage capacitor in the energy storage circuit.

[0064] Specifically, this system can achieve independent real-time control of the front-end and back-end stages, thus reducing the complexity of the control system: Front-end stage: Three series-connected switching transistors K1, K2, and K3 are synchronously driven to stabilize the voltage of capacitor C4. The control strategy uses an 800V voltage threshold as a reference. After comparing the actual voltage of capacitor C4 with the threshold, the difference between the actual voltage of C4 and the threshold voltage is output as a duty cycle signal via a PI regulator. This PI regulation, based on the negative feedback of the voltage difference, adjusts the conduction time of the three switching transistors, thereby achieving energy feedback regulation from the rear stage to the front stage. The duty cycle of the front stage dynamically changes with the battery charging power: when the voltage drops rapidly (i.e., the charging power increases), the duty cycle increases to enhance energy feedback; conversely, it decreases to maintain a constant voltage in C4.

[0065] The subsequent stage employs a dual closed-loop control strategy to achieve constant current and constant voltage charging of the battery. In the constant current charging (CC) stage, current closed-loop control is the core. Specifically, the given current value of 750A is compared with the real-time sampled effective current value from the battery side. The error signal is processed by a PI regulator to generate a PWM duty cycle, which is then adjusted based on the current difference negative feedback to control the chopper switch K. When the battery's state of charge (SOC) reaches 80%, the subsequent control system switches to constant voltage charging (CV) mode. The real-time detected battery voltage value is compared with the given voltage value (1200V). The error is then fed back to the chopper switch K via a PI regulator, which adjusts the voltage difference negative feedback, reducing the charging current and consequently lowering the charging power.

[0066] It should be noted that the duty cycle of both the front and rear control sections is dynamically adjusted by the PI regulator based on real-time monitoring and comparison of the production duty cycle, thereby driving the front and rear switching transistors to maintain the power balance of the front and rear systems and achieve MW-level power charging.

[0067] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0068] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" or "several" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0069] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Similar DC high voltage division, energy extraction, and chopping methods are also within the scope of the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A high-voltage DC fast charging system based on inductive energy extraction, characterized in that, It includes a front-end rectification and power supply module and a back-end charging and power harvesting module. The rectification and power supply module includes an AC rectifier circuit, a DC voltage divider circuit, and a power supply circuit. The charging and power harvesting module includes a power harvesting inductor and a chopper switch. The DC voltage output of the AC rectifier circuit is connected to the DC voltage divider circuit, and the power supply circuit is connected in parallel with the DC voltage divider circuit to charge and replenish the DC voltage divider circuit through external pulse width modulation. The energy extraction inductor is connected to the DC voltage divider circuit to extract energy, and the output charging current is controlled by the operation of the chopper switch.

2. The high-voltage DC fast charging system based on inductive energy extraction as described in claim 1, characterized in that, The AC rectifier circuit includes an AC circuit breaker and a three-phase rectifier bridge. The three-phase AC power is input to the three-phase rectifier bridge through the AC circuit breaker and converted into DC power output.

3. The high-voltage DC fast charging system based on inductive energy extraction as described in claim 1, characterized in that, The DC voltage divider circuit includes a capacitor branch formed by several high-voltage capacitors connected in series and a resistor branch formed by several resistors connected in series. The resistor branch is connected in parallel with the capacitor branch, and the number of high-voltage capacitors in the capacitor branch is the same as the number of resistors in the resistor branch.

4. The high-voltage DC fast charging system based on inductive energy extraction as described in claim 3, characterized in that, The high-voltage capacitor at the end of the capacitor branch is a large-capacity high-voltage capacitor, while the other high-voltage capacitors in the capacitor branch are small-capacity high-voltage capacitors; the capacitance value of the large-capacity high-voltage capacitor is much larger than that of the small-capacity high-voltage capacitor.

5. The high-voltage DC fast charging system based on inductive energy extraction as described in claim 4, characterized in that, The power replenishment circuit includes the same number of switching transistors as the small-capacity high-voltage capacitors in the capacitor branch, with each switching transistor connected in series and then connected to the two ends of the corresponding small-capacity high-voltage capacitor.

6. The high-voltage DC fast charging system based on inductive energy extraction as described in claim 5, characterized in that, The source and drain of each switching transistor are connected to the two ends of a corresponding small-capacity high-voltage capacitor and a resistor, respectively, and the gate of each switching transistor is used to receive the power-up PWM drive signal.

7. The high-voltage DC fast charging system based on inductive energy extraction as described in claim 4, characterized in that, The positive terminal of the high-voltage capacitor at the end of the capacitor branch serves as a reference energy node. One end of the energy harvesting inductor is connected to the reference energy node via a DC circuit breaker to extract and store energy. The chopper switch is connected between the other end of the energy harvesting inductor and the negative terminal of the high-voltage capacitor at the end of the branch. The anode of the anti-reverse diode is connected to the other end of the energy-collecting inductor, the cathode of the anti-reverse diode is connected to one end of the capacitor, the other end of the capacitor is connected to the negative terminal of the high-voltage capacitor in the final stage, and the capacitor is connected in parallel with the battery to be charged.

8. The high-voltage DC fast charging system based on inductive energy extraction as described in claim 7, characterized in that, The source of the chopper switch is connected to one end of the power harvesting inductor, the drain of the chopper switch is connected to the negative terminal of the high-voltage capacitor in the final stage via a DC circuit breaker, and the gate of the chopper switch is used to receive the charging PWM drive signal.

9. The high-voltage DC fast charging system based on inductive energy extraction as described in claim 4, characterized in that, The positive terminal of the high-voltage capacitor at the end of the capacitor branch serves as a reference energy node. One end of the energy harvesting inductor is connected to the reference energy node via a DC circuit breaker to extract and store energy. A chopper switch is connected in series between the reference energy node and the energy harvesting inductor. The cathode of the reverse protection diode is connected to one end of the energy harvesting inductor, and the anode of the reverse protection diode is connected to the negative terminal of the high-voltage capacitor at the end of the branch. The other end of the energy harvesting inductor is connected to a capacitor connected in parallel across the two ends of the battery to be charged.

10. The high-voltage DC fast charging system based on inductive energy extraction as described in claim 9, characterized in that, The source of the chopper switch is connected to the reference energy node via a DC circuit breaker, the drain of the chopper switch is connected to one end of the energy harvesting inductor, and the gate of the chopper switch is used to receive the charging PWM drive signal.

11. The high-voltage DC fast charging system based on inductive energy extraction as described in any one of claims 1-10, characterized in that, The front-end rectifier and power replenishment module can be configured as a single-gun front-end capacity or a substation-level capacity.

12. A control method for a high-voltage DC fast charging system based on inductive energy extraction as described in any one of claims 1-11, characterized in that, include: When the high-voltage AC input is connected, the high-voltage AC power is converted into high-voltage DC power through the AC rectifier circuit and output to the DC voltage divider circuit; The charging power harvesting module of the later stage is connected to the device to be charged and enters the constant current charging mode. The current error signal is calculated based on the current setpoint and the effective current value sampled in real time on the device to be charged. The first charging PWM drive signal is generated based on the current error signal to control the duty cycle of the chopper switch so that the charging current output by the power harvesting inductor is kept at the set constant current reference value. The difference between the actual voltage of the DC voltage divider circuit and the voltage setting threshold is used to generate a supplementary PWM drive signal, and the supplementary PWM drive signal is used to control the supplementary circuit to charge and supplement the DC voltage divider circuit.

13. The control method for the high-voltage DC fast charging system based on inductive energy extraction as described in claim 12, characterized in that, The method further includes: When the voltage across the device to be charged reaches the set threshold, the charging mode switches from constant current charging mode to constant voltage charging mode. The voltage error signal is calculated based on the real-time detected voltage across the device and the voltage setpoint. A second charging PWM drive signal is generated based on the voltage error signal to control the duty cycle of the chopper switch so that the charging current output by the energy harvesting inductor is reduced.

14. The control method for the high-voltage DC fast charging system based on inductive energy extraction as described in claim 12, characterized in that, The method further includes: The switching transistors in the energy replenishment circuit are synchronously driven according to the energy replenishment PWM drive signal, so as to adjust the conduction time of each switching transistor to charge the final high-voltage capacitor in the energy storage circuit.

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