Boost charging method and circuit for electric vehicle, vehicle, storage medium and program product

Abstract

The invention relates to the technical field of vehicle charging, and discloses an electric vehicle boost charging method and circuit, a vehicle, a storage medium and a program product, an upper bridge arm power switch tube of a direct current boost charging circuit is integrated with a body diode, and the method comprises the following steps: obtaining a direct current charging current, and identifying whether a target charging scene is satisfied based on the direct current charging current; the charging current of the target charging scene is smaller than a preset current threshold; when the target charging scene is met, a power switch tube of the inverter is controlled in an intermittent conduction mode, and the intermittent conduction mode is used for controlling an upper bridge arm power switch tube to be kept closed in each control period of direct current charging and controlling a lower bridge arm power switch tube to be conducted for preset time. According to the invention, in a low-current boost charging scene, the heating of the magnetic ring is in a controllable range, and continuous charging is realized.

Description

Technical Field

[0001] This invention relates to the field of vehicle charging technology, specifically to a method, circuit, vehicle, storage medium, and program product for boosting the charging of electric vehicles. Background Technology

[0002] As electric vehicle voltages evolve towards higher levels like 750V and 1000V, existing 500V and 750V DC charging piles on the market are insufficient for compatibility. The industry generally adopts DC boost charging circuits that reuse motor windings and motor controllers. Simultaneously, to reduce overall vehicle energy consumption, the switching speed of motor controllers under driving conditions is increasing, leading to a more pronounced problem of bearing electro-corrosion. To address this bearing electro-corrosion issue, three-phase magnetic rings need to be added to the three-phase output side of the inverter to suppress common-mode voltage. However, adding three-phase magnetic rings introduces a series of problems under boost charging conditions. During low-current charging, the three-phase magnetic rings experience high hysteresis losses, generating significant heat and posing a high thermal risk. Related technologies further ensure safety by limiting the minimum charging current, but this leads to new problems such as the battery not being fully charged and poor compatibility with low-power charging piles. Therefore, balancing the thermal safety of the magnetic rings with charging performance is a problem that needs to be solved. Summary of the Invention

[0003] This invention provides a method, circuit, vehicle, storage medium, and program product for boost charging of electric vehicles, in order to solve the problem that boost charging cannot simultaneously ensure the thermal safety of the magnetic ring and the charging performance.

[0004] In a first aspect, the present invention provides a method for boost charging of electric vehicles, applied to a motor controller in a DC boost charging circuit. The upper arm power switch of the inverter in the DC boost charging circuit integrates a body diode. The method includes: acquiring a DC charging current and identifying whether a target charging scenario is met based on the DC charging current, wherein the charging current of the target charging scenario is less than a preset current threshold; when the target charging scenario is met, using an intermittent conduction mode to control the power switch of the inverter, wherein the intermittent conduction mode is used to keep the upper arm power switch closed in each control cycle of DC charging and to control the lower arm power switch of the inverter to conduct for a preset time.

[0005] In some optional implementations, the identification of whether the target charging scenario is met based on the DC charging current includes: obtaining the current control mode; if the current control mode is a continuous conduction mode or an initialization mode, the target charging scenario is determined to be met when the DC charging current is less than a first preset current threshold. The continuous conduction mode is used to control the upper bridge arm power switch and the lower bridge arm power switch to conduct alternately in each control cycle of DC charging, and the initialization mode is used to characterize the state of the DC charging pile at the initial moment of charging the battery; if the current control mode is an intermittent conduction mode, the target charging scenario is determined to be met when the DC charging current is less than a second preset current threshold, and the second preset current threshold is greater than the first preset current threshold.

[0006] In some alternative implementations, the first preset current threshold is 10A and the second preset current threshold is 12A.

[0007] In some optional implementations, the upper arm power switch includes a first power switch, a third power switch, and a fifth power switch, and the lower arm power switch includes a second power switch, a fourth power switch, and a sixth power switch. When the target charging scenario is met, the inverter's power switches are controlled using an intermittent conduction mode, including: controlling the second, fourth, and sixth power switches to conduct simultaneously within their respective control cycles, and controlling the second, fourth, and sixth power switches to turn off simultaneously after a preset conduction time; and controlling the first, third, and fifth power switches to remain off.

[0008] In some optional implementations, when the target charging scenario is met, the power switches of the inverter are controlled in an intermittent conduction mode, including: controlling the second, fourth and sixth power switches to conduct at a preset angle with phase shift within their respective control cycles, and controlling the second, fourth and sixth power switches to turn off after a preset conduction time; and controlling the first, third and fifth power switches to remain off.

[0009] In some alternative implementations, the method further includes: controlling the power switching transistors of the inverter in a continuous conduction mode when the target charging scenario is not met.

[0010] In some optional implementations, when the target charging scenario is not met, the inverter's power switches are controlled in a continuous conduction mode, including: controlling the second, fourth, and sixth power switches to conduct simultaneously within their respective control cycles, and controlling the second, fourth, and sixth power switches to turn off simultaneously after a preset conduction time; within the control cycle of the second power switch, when the second power switch is off, controlling the first power switch to conduct, and when the second power switch is on, controlling the first power switch to turn off; within the control cycle of the fourth power switch, when the fourth power switch is off, controlling the third power switch to conduct, and when the fourth power switch is on, controlling the third power switch to turn off; within the control cycle of the sixth power switch, when the sixth power switch is off, controlling the fifth power switch to conduct, and when the sixth power switch is on, controlling the fifth power switch to turn off.

[0011] In some optional implementations, when the target charging scenario is not met, the inverter's power switches are controlled in a continuous conduction mode, including: controlling the second, fourth, and sixth power switches to conduct at a preset angle with phase shift within their respective control cycles, and controlling the second, fourth, and sixth power switches to turn off after a preset conduction time; within the control cycle of the second power switch, when the second power switch is off, controlling the first power switch to conduct, and when the second power switch is on, controlling the first power switch to turn off; within the control cycle of the fourth power switch, when the fourth power switch is off, controlling the third power switch to conduct, and when the fourth power switch is on, controlling the third power switch to turn off; within the control cycle of the sixth power switch, when the sixth power switch is off, controlling the fifth power switch to conduct, and when the sixth power switch is on, controlling the fifth power switch to turn off.

[0012] In some optional implementations, in the intermittent conduction mode, the preset time for controlling the conduction of the lower bridge arm power switch is determined by the following steps: A volt-second balance equation is established based on a first duty cycle parameter, a second duty cycle, the charging pile output voltage, and the battery voltage. The volt-second balance equation indicates that the average voltage across the inductor in the motor winding is zero within one control cycle. The first duty cycle parameter is an unknown parameter for the duty cycle controlling the conduction of the lower bridge arm power switch, and the second duty cycle is the duty cycle of the freewheeling current of the body diode in the upper bridge arm power switch. A power balance equation is established based on the charging pile output voltage, battery voltage, battery current, the equivalent inductance of the motor during boost charging, and the control cycle. The power balance equation indicates that the motor output power and battery input power are balanced within one switching cycle. The volt-second balance equation and the power balance equation are solved simultaneously to obtain the first duty cycle parameter. The preset time is determined based on the product of the first duty cycle and the control cycle.

[0013] Secondly, the present invention provides a boost charging circuit for electric vehicles, comprising a motor controller, a motor, an inverter, a bus capacitor, a three-phase magnetic ring, a main positive relay, and a main negative relay; wherein the positive terminal of the DC charging pile is connected to the neutral point of the motor, the negative terminal of the DC charging pile is connected to the common source terminal of the lower arm power switch of the inverter, the common drain terminal of the upper arm power switch of the inverter is connected to the positive terminal of the battery through the main positive relay, the negative terminal of the battery is connected to the common source terminal of the lower arm power switch through the main negative relay, the three-phase output terminal of the inverter is connected to the three-phase input terminal of the motor, a bus capacitor is connected between the common drain terminal of the upper arm power switch and the common source terminal of the lower arm power switch, the motor controller is connected to the control terminals of the upper arm power switch and the lower arm power switch respectively, the three-phase magnetic ring is disposed at the three-phase output terminal of the inverter, and the upper arm power switch integrates a body diode; the motor controller is used to execute the method provided in the first aspect and any one of the first aspects.

[0014] In some optional implementations, the upper arm power switch includes a first power switch, a third power switch, and a fifth power switch, and the lower arm power switch includes a second power switch, a fourth power switch, and a sixth power switch. The output terminals of the first and second power switches are connected to the same phase input terminal of the motor, the output terminals of the third and fourth power switches are connected to the same phase input terminal of the motor, and the output terminals of the fifth and sixth power switches are connected to the same phase input terminal of the motor.

[0015] Thirdly, the present invention provides a vehicle in which the electric vehicle boost charging circuit provided in the second aspect is deployed.

[0016] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to perform the method described in the first aspect or any corresponding embodiment thereof.

[0017] Fifthly, the present invention provides a computer program product, including computer instructions for causing a computer to perform the method described in the first aspect or any corresponding embodiment thereof.

[0018] The technical solution provided by this invention has the following advantages:

[0019] This invention achieves dual protection for the thermal safety of the three-phase magnetic ring and the performance of boost charging by identifying low-current scenarios and switching to intermittent conduction mode. Addressing the overheating issue caused by fluctuations in electromagnetic intensity across ranges during low-current charging, this invention controls the upper bridge arm power switch to remain completely off via intermittent conduction mode, relying solely on the body diode for freewheeling. This prevents reverse flow of the motor inductor current and confines the electromagnetic intensity to the first quadrant. Even at a low current of 5A, the magnetic ring temperature remains stable below the safe threshold, resolving the risk of thermal failure. Simultaneously, it eliminates the need to limit the minimum charging current, enabling stable charging even with low currents and achieving full battery charging, thus overcoming compatibility bottlenecks. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a DC boost charging circuit according to an embodiment of the present invention; Figure 2 This is another schematic diagram of a DC boost charging circuit according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a vehicle charging scenario according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the BH curve according to an embodiment of the present invention; Figure 5 This is a schematic diagram of CCM mode parameters under 50A charging conditions according to an embodiment of the present invention; Figure 6 This is a schematic diagram of CCM mode parameters under 10A charging conditions according to an embodiment of the present invention; Figure 7 This is a schematic diagram of CCM mode parameters under 5A charging conditions according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the first step of a method for boosting the charging voltage of an electric vehicle according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the DCM mode parameters under a 5A charging condition according to an embodiment of the present invention; Figure 10 This is a timing diagram for switching between CCM mode and DCM mode according to an embodiment of the present invention; Figure 11 This is a schematic diagram of a second process for a method of boosting the charging voltage of an electric vehicle according to an embodiment of the present invention; Figure 12 This is a schematic diagram of the third process of a method for boosting the voltage of an electric vehicle according to an embodiment of the present invention; Figure 13 This is a schematic diagram of the fourth process of a method for boosting the voltage of an electric vehicle according to an embodiment of the present invention; Figure 14 This is a schematic diagram of the structure of a tram boost charging circuit according to an embodiment of the present invention. Detailed Implementation

[0022] 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 with reference to the accompanying drawings. 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.

[0023] It is understood that before using the technical solutions disclosed in the various embodiments of the present invention, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in the present invention and their authorization should be obtained in accordance with relevant laws and regulations through appropriate means.

[0024] With the rapid iteration of new energy vehicle technology, the battery voltage platform of electric vehicles is evolving from the early 500V to higher voltage levels such as 750V and 1000V to meet user demands for longer driving range and faster charging. However, the upgrading speed of charging piles, as charging infrastructure, lags behind the development of vehicle technology. Currently, a large number of 500V DC charging piles still exist on the market. These low-voltage charging piles cannot directly charge high-voltage batteries such as 750V and 1000V, creating a core contradiction between "vehicle high-voltage demand" and "charging pile low-voltage supply." To resolve this contradiction, the industry generally adopts methods such as... Figure 1 and Figure 2 A boost charging scheme for a reused drive motor system.

[0025] as follows Figure 3 As shown, the left side shows a charging station ①, and the right side shows electric vehicles equipped with various charging solutions. If... Figure 3 If charging station ① is an AC charging station, then it can be used with the on-board charger ④ to charge the battery. If charging station ① is a DC charging station, and the voltage level of the charging station is higher than that of the electric vehicle (e.g., the charging station is 750V and the electric vehicle is 500V), then it can be used with the direct charging line ② to directly charge the battery. If charging station ① is a DC charging station, and the voltage level of the charging station is lower than that of the electric vehicle (e.g., the charging station is 500V and the electric vehicle is 800V), then it needs to be used with... Figure 3The DC boost charging circuit ③ in the invention charges the battery after being boosted by the electric drive system. The technical solution provided in this embodiment is applied in the DC boost charging scenario of electric vehicles, i.e., in conjunction with... Figure 3 The DC boost charging circuit ③ in the middle charges the battery after being boosted by the electric drive system.

[0026] The core of a DC boost charging circuit is to utilize the motor windings and motor controller in the original drive system of an electric vehicle to construct a system like... Figure 1 The DC boost charging circuit shown includes a motor controller, a motor, an inverter, a bus capacitor, a three-phase magnetic ring, a main positive relay, and a main negative relay. The positive terminal of the DC charging pile is connected to the neutral point of the motor, and the negative terminal of the DC charging pile is connected to the common source terminal of the lower arm power switch of the inverter. The common drain terminal of the upper arm power switch of the inverter is connected to the positive terminal of the battery through the main positive relay, and the negative terminal of the battery is connected to the common source terminal of the lower arm power switch through the main negative relay. The three-phase output terminal of the inverter is connected to the three-phase input terminal of the motor. A bus capacitor is connected between the common drain terminal of the upper arm power switch and the common source terminal of the lower arm power switch. The motor controller is connected to the control terminals of the upper arm power switch and the lower arm power switch respectively. The three-phase magnetic ring is located at the three-phase output terminal of the inverter.

[0027] The motor windings are equivalent to the inductors required for voltage boosting, and the six power switching transistors in the inverter (such as...) Figure 1 As shown in the internal circuit diagram of the drive motor system, the first power switch (S1 to the sixth power switch (S6)) is controlled by the motor controller and acts as an electronic switch, working in conjunction with the main positive / main negative relay to achieve the "energy storage-energy release" boost process. The upper bridge arm power switches include the first power switch S1, the third power switch S3, and the fifth power switch S5, while the lower bridge arm power switches include the second power switch S2, the fourth power switch S4, and the sixth power switch S6. The output terminals of the first and second power switches S1 and S2 are connected to the same phase input terminal of the motor, the output terminals of the third and fourth power switches S3 and S4 are connected to the same phase input terminal of the motor, and the output terminals of the fifth and sixth power switches S5 and S6 are connected to the same phase input terminal of the motor.

[0028] Specifically, when the lower axle arm power switch is turned on, the charging pile current flows into the motor's three-phase windings, converting electrical energy into magnetic energy for storage. When the upper axle arm power switch is turned on, the motor windings release magnetic energy, which is then superimposed with the charging pile voltage and output to the high-voltage battery. Therefore, during charging, the motor controller controls the upper and lower axle arm switches of the inverter to alternately turn on, thereby enabling the low-voltage charging pile to charge the high-voltage battery without the need for an additional independent boost converter, significantly reducing the overall vehicle cost and space occupation.

[0029] However, in this solution, to reduce overall vehicle energy consumption, the switching speed of the motor controller increases during driving (a higher switching frequency of the inverter's power switching transistors reduces battery energy waste). This causes the bearing electro-corrosion problem to become increasingly prominent as current flows through the aforementioned boost charging circuit. To address this bearing electro-corrosion issue, a three-phase magnetic ring needs to be added to the inverter's three-phase output side to suppress the common-mode voltage (such as...) that triggers bearing electro-corrosion. Figure 2 (The magnetic ring structure next to the motor). Its principle is to reduce the common-mode current and lower the common-mode voltage across the bearing, thereby preventing bearing electro-corrosion.

[0030] However, the addition of a three-phase magnetic ring has brought new technical challenges. Under boost charging conditions, the loss and heat generation of the magnetic ring depend entirely on the current characteristics passing through it. The magnitude of the charging current directly determines the working area of ​​the magnetic ring, which can be analyzed in conjunction with the current flow direction and the variation law of the magnetic field strength H of the magnetic ring. From the working principle of magnetic rings, such as Figure 4 As shown, the magnetic flux density B-magnetic field strength H curve of the three-phase magnetic ring exhibits two key operating regions: the "saturation region" and the "linear region." When the magnetic field strength H inside the ring exceeds 15 A / m, the ring enters the saturation region, where hysteresis loss is minimal and almost no heat generation occurs. When H ≤ 15 A / m, the ring operates in the linear region or the linear-critical saturation region, where hysteresis loss increases dramatically with varying magnetic field strength H, resulting in severe heat generation. The magnitude of the magnetic field strength H is determined by the common-mode current of the three-phase windings of the motor, and the direction and magnitude of the common-mode current are directly related to the charging current.

[0031] High-current charging scenarios (e.g., 50A, Figure 5 At this time, the charging pile output current is large, and the currents iU, iV, and iW flowing through the three-phase windings of the motor have high amplitudes. The common-mode current formed by the superposition of the three-phase currents is also large, making the internal H of the magnetic ring > 120A / m, far exceeding the saturation threshold of 15A / m. The magnetic ring works stably in the saturation region with low loss and no heat risk. Medium current charging scenarios (e.g., 10A, Figure 6 As the charging current decreases, the amplitudes of the currents iU, iV, and iW in the three-phase windings of the motor decrease, and the common-mode current decreases accordingly. This causes the magnetic field strength H inside the magnetic ring to fluctuate between -23A / m and 113A / m. At this time, the magnetic field strength H will frequently switch between the "linear region (H≤15A / m)" and the "saturation region (H>15A / m)". The hysteresis loss of the magnetic ring increases significantly (hysteresis loss is proportional to the range of H change, that is, the larger the area enclosed in the BH curve, the higher the loss). The magnetic ring will generate obvious heat, posing a thermal risk. Low-current charging scenarios (e.g., 5A, Figure 7The charging current is further reduced, the amplitudes of the three-phase winding currents iU, iV, and iW are lower, the common-mode current fluctuations are smoother, and the range of magnetic field strength H is reduced to -50A / m to 90A / m. At this time, the magnetic field strength H repeatedly switches between the negative linear region (H=-50A / m~-15A / m), the positive linear region (H=-15A / m~15A / m), and the positive saturation region (H>15A / m). Figure 4 The loss area enclosed by the BH curve shown reaches its maximum, the hysteresis loss increases sharply, the magnetic ring heats up severely, and there is even a risk of thermal failure.

[0032] To avoid overheating and damage to the three-phase magnetic ring, the only feasible solution is to "limit the minimum charging current." This involves setting a minimum charging current threshold (e.g., 10A) through software, forcing the charging current to remain at a level that allows the magnetic ring to enter the saturation region. However, this solution has significant drawbacks. First, towards the end of charging, when the battery is close to full charge, the charging current will naturally drop below 10A. At this point, to protect the magnetic ring from overheating, charging will automatically stop, preventing the battery from reaching 100% SOC (fully charged state), thus affecting the user experience. Second, when facing low-power DC charging piles on the market (e.g., those that can only output 5A~8A current), the vehicle cannot activate the boost charging function because the current is below the threshold, resulting in poor charging pile compatibility and limiting the vehicle's charging scenarios.

[0033] In summary, the relevant technologies are caught in a contradiction between "protecting the bearing" and "ensuring charging performance." Although three-phase magnetic rings can prevent bearing electro-corrosion, the magnetic rings generate significant heat during low-current charging. Limiting the minimum charging current to protect the magnetic rings, however, leads to incomplete battery charging and poor charging pile compatibility. How to solve the magnetic ring overheating problem during low-current charging while retaining the three-phase magnetic rings, and simultaneously ensuring the integrity and compatibility of boost charging, has become a pressing technical challenge for current electric vehicle boost charging systems.

[0034] To address the aforementioned problems, according to an embodiment of the present invention, a method for boosting the charging voltage of an electric vehicle is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0035] This embodiment provides a method for boost charging of electric vehicles, which can be used in the aforementioned DC boost charging circuit. The upper arm power switch of the inverter in the DC boost charging circuit integrates a body diode. Figure 8 This is a flowchart of a method for boosting the voltage of an electric vehicle according to an embodiment of the present invention. The process includes the following steps: Step S101: Obtain the DC charging current and identify whether the target charging scenario is met based on the DC charging current. The charging current of the target charging scenario is less than the preset current threshold. Step S102: When the target charging scenario is met, the power switching transistors of the inverter are controlled in an intermittent conduction mode. The intermittent conduction mode is used to keep the upper bridge arm power switching transistors off in each control cycle of DC charging and to control the lower bridge arm power switching transistors to conduct for a preset time.

[0036] Specifically, the electric vehicle boost charging method provided in this embodiment of the invention is applicable to, for example, Figure 2 The DC boost charging circuit shown features a three-phase magnetic ring on the three-phase output side of the inverter, and all power switches in the upper bridge arms of the inverter (such as the first, third, and fifth power switches) integrate body diodes. The body diode is a naturally formed PN junction structure in the power switch manufacturing process, located between the source and drain of the switch. It requires no external connection and provides a current freewheeling path under specific operating conditions, preventing the switch from being damaged by voltage spikes. For example, power switches with integrated body diodes must be power MOSFETs (metal-oxide-semiconductor field-effect transistors), and BJTs (bipolar junction transistors) without integrated body diodes cannot be used as power switches.

[0037] In real-world charging scenarios, when a vehicle connects to a DC charging station for boost charging, the DC charging current is first acquired, and the system then determines whether the target charging scenario is met based on this current. The DC charging current refers to the real-time current output from the DC charging station and flowing through the DC boost charging circuit. This current can be directly acquired by a current sensor connected in series in the circuit, such as a Hall effect current sensor, which can provide real-time feedback of the current value. The target charging scenario refers to a condition where the charging current is lower than a preset current threshold. This threshold needs to be set in conjunction with the thermal safety characteristics of the three-phase magnetic ring.

[0038] Because three-phase magnetic rings have a "saturation region" and a "linear region," when the current is large enough, the ring enters the saturation region (magnetic field strength H > 15 A / m), resulting in low hysteresis loss and no thermal risk. When the current is too low, the ring operates in the linear region or the linear-critical saturation region, leading to a sharp increase in losses. For example, a three-phase magnetic ring in a certain vehicle model, according to actual tests, frequently switches between multiple regions when the current is below 10 A, significantly increasing the thermal risk. Therefore, the criterion for determining the "target charging scenario" can be set as "DC charging current < 10 A." For example, in application, the vehicle's control unit will read the values ​​collected by the current sensor in real time. If the current is detected to be 8 A, which is below the 10 A threshold, the target charging scenario is deemed to be met.

[0039] When the target charging scenario is met, this embodiment of the invention executes discontinuous conduction mode control of the inverter's power switches. Discontinuous conduction mode (DCM mode) is a control strategy relative to continuous conduction mode (CCM mode). Its core characteristic is that in each control cycle of DC charging, the upper bridge arm power switch remains off, while only the lower bridge arm power switch is controlled to conduct for a preset duty cycle for a preset time. In this embodiment, the control cycle refers to the switching cycle of the inverter's power switches, which is determined by the switching frequency of the motor controller. For example, if the switching frequency is set to 10kHz, the control cycle is 100μs (1 / 10kHz). The preset time, i.e., the conduction duration of the lower bridge arm switch, needs to be calculated based on the boost requirements and will not be elaborated here.

[0040] The specific control process is as follows: In each control cycle, the control unit sends a shutdown signal to the first power switch S1, the third power switch S3, and the fifth power switch S5 (upper bridge arm power switches), keeping them in the off state at all times. At this time, current cannot actively flow through the upper bridge arm switches. Simultaneously, it sends a same-direction control or phase-out control turn-on signal to the second power switch S2, the fourth power switch S4, and the sixth power switch S6 (lower bridge arm power switches), turning them on for a preset duty cycle time. This stage is the "energy storage stage." The charging pile current flows into the three-phase windings of the motor through the turned-on lower bridge arm switches. The motor windings are equivalent to step-up inductors, converting electrical energy into magnetic energy for storage, and the current gradually increases from 0 to its peak value. After the "energy storage phase" ends, the control unit sends a shutdown signal to the lower bridge arm power switch to disconnect it for the remainder of the control cycle. At this time, the energy release phase begins, and the magnetic energy stored in the motor windings begins to be released. The current flows through the body diode of the upper bridge arm switch to the battery terminal. After being superimposed with the charging pile voltage, the voltage is boosted, thus enabling boost charging.

[0041] The principle behind reducing magnetic ring heat generation by using intermittent conduction mode to address increased magnetic ring losses is as follows: In a three-phase parallel Boost circuit constructed by reusing motor windings and a motor controller, the intermittent conduction mode enables the three-phase magnetic ring to avoid overheating during low-current charging. The core reason is that it limits the direction and range of the motor inductor current by controlling the conduction logic of the power switching transistor, thereby reducing the variation range of the magnetic field strength H inside the three-phase magnetic ring and fundamentally reducing hysteresis loss.

[0042] From the circuit's operating logic perspective, after determining that the target charging scenario is met and switching to DCM mode, the second power switch S2, the fourth power switch S4, and the sixth power switch S6 of the inverter's lower bridge arm conduct in the first half of their respective control cycles, guiding the DC charging pile current into the motor's three-phase windings. At this time, the equivalent inductor element of the motor windings stores magnetic energy, and the three-phase current gradually increases. When entering the second half of the control cycle, the lower bridge arm power switches turn off, while the first power switch S1, the third power switch S3, and the fifth power switch S5 of the upper bridge arm remain off. At this time, the magnetic energy stored in the motor windings cannot be actively released through the upper bridge arm switches, but instead flows through the body diode integrated in the upper bridge arm switches. The current flows to the battery along the path of "motor winding → body diode → battery". During the freewheeling process, the three-phase current will continuously decrease. When the current drops to 0, the body diode will naturally cut off due to reverse bias, unlike the continuous conduction mode where the current reverses due to the active conduction of the upper bridge arm switches, thus reducing the heating of the magnetic ring.

[0043] like Figure 9 The diagram shows the characteristics of the three-phase current and the three-phase magnetic ring current in DCM mode at a charging current of 5A. The common-mode current flowing through the magnetic ring only exists in the positive flow phase, with no negative current component. The corresponding magnetic field strength H is strictly limited to the first quadrant of the BH curve (magnetic field strength H ranges from 0 to 49 A / m), meaning that the magnetic field strength H only changes within the positive saturation region (H>15 A / m). In the saturation state, the magnetic permeability of the magnetic ring decreases significantly, and the hysteresis loss decreases. Even under a small current of 5A, the heat generated by the magnetic ring can be dissipated in time through its own heat dissipation structure, preventing overheating risks.

[0044] In CCM mode, when the lower bridge arm power switch is off, if the upper bridge arm power switch is turned on, the circuit will enter synchronous rectification mode. When the three-phase current drops to 0, the bus capacitor voltage and the DC charging pile voltage work together to reverse the three-phase current. This current reversal causes the magnetic field strength H to fluctuate between positive and negative ranges (e.g., ...). Figure 7 As shown, when the charging current is 5A, the magnetic field strength H varies from -50 to 90A / m, which causes the magnetic ring to overheat severely.

[0045] The table below shows the simulation results of the variation range and trend of magnetic field strength H under different control modes and charging currents when the DC charging pile voltage is 450V and the battery pack voltage is 950V.

[0046]

[0047] Simulation data also provides a clear verification: when the DC charging pile voltage is 450V, the battery pack voltage is 950V, and the charging current decreases from 15A to 4A, the maximum value of the magnetic field strength H in DCM mode steadily decreases from 113A / m to 42.3A, while the minimum value remains at 0, with no negative fluctuations throughout. In contrast, in CCM mode, the minimum value of the magnetic field strength H gradually extends negatively as the current decreases (e.g., Hmin = -50A / m at 5A), and the fluctuation range continues to expand. Actual test results further demonstrate that CCM mode requires a charging current ≥10A to ensure the magnetic ring does not overheat, while DCM mode can stably control the magnetic ring temperature below 130℃ (the industry safety threshold is typically 150℃) even at 5A or lower currents, fully verifying the role of DCM mode in ensuring the thermal safety of the magnetic ring.

[0048] This invention accurately identifies low-current charging scenarios and switches to intermittent conduction mode, limiting the magnetic field strength variation range of the three-phase magnetic ring to the saturation region of a single quadrant. This significantly reduces hysteresis losses, solves the problem of magnetic ring overheating during low-current charging, and eliminates the risk of thermal failure. There is no need to limit the minimum charging current; even if the current drops below 5A at the end of the charging process, stable charging can still be achieved, resulting in 100% battery charging. It is also compatible with low-power DC charging piles, improving compatibility with charging stations. Furthermore, freewheeling is achieved using the body diode integrated in the upper bridge arm switch, eliminating the need for external diodes, simplifying the circuit structure, reducing overall vehicle cost and space occupation, and avoiding additional losses from external components.

[0049] In some optional implementations, step S101 above includes: Step a1: Obtain the current control mode; Step a2: If the current control mode is continuous conduction mode or initialization mode, when the DC charging current is less than the first preset current threshold, it is determined that the target charging scenario is met. The continuous conduction mode is used to control the upper bridge arm power switch and the lower bridge arm power switch to conduct alternately in each control cycle of DC charging. The initialization mode is used to characterize the state of the DC charging pile at the initial moment of charging the battery. Step a3: If the current control mode is intermittent conduction mode, when the DC charging current is less than the second preset current threshold, it is determined that the target charging scenario is met. The second preset current threshold is greater than the first preset current threshold.

[0050] Specifically, the first step is to obtain the current control mode. The current control mode refers to the motor controller's current control strategy for the inverter's power switches, primarily including three modes: CCM mode, DCM mode, and initialization mode. CCM mode is used during high-current charging, controlling the upper and lower bridge arm power switches to alternately conduct, ensuring continuous current flow. Initialization mode specifically refers to the initial moment when the DC charging pile first establishes a connection with the vehicle and begins charging the battery (usually 0-3 seconds after charging starts), at which point the charging system has not yet entered a stable control state.

[0051] The first preset current threshold is a low-current judgment standard set for CCM mode and initialization mode, and needs to be determined in conjunction with the thermal safety characteristics of the three-phase magnetic ring. For example, in this embodiment of the invention, when the charging current is lower than 10A, the magnetic ring is prone to operating in the linear region, resulting in heat generation. Therefore, the first preset current threshold can be set to 10A. This embodiment of the invention is only an example and is not limited thereto. In some optional embodiments, the first preset current threshold value ranges from 5A to 10A.

[0052] For example, in a specific scenario, such as Figure 10 As shown, the current control mode is CCM mode, and the charging current is 8A as collected by the Hall current sensor. Since 8A < 10A and the mode is CCM, it is determined that the target charging scenario is met, and it is necessary to switch to DCM mode.

[0053] Scenario 2: The current control mode is initialization mode (charging pile has just started charging). The initial charging current is 5A. Since 5A < 10A, the target charging scenario is also met, and DCM mode is directly activated. It should be noted that the first preset current threshold is used directly in initialization mode. Considering that the current fluctuates greatly in the initial stage of charging, entering DCM mode in advance can avoid instantaneous overheating of the magnetic ring when the current drops sharply.

[0054] The second preset current threshold is a threshold set for DCM mode and must be greater than the first preset current threshold (e.g., set to 12A in this solution; in some optional embodiments, the second preset current threshold can be set to be 2A greater than the first preset current threshold). This acts as a "hysteresis" mechanism, preventing frequent mode switching when the charging current fluctuates around the first threshold. For example, when the vehicle is already in DCM mode, and the charging current increases from 9A to 11A, since 11A < 12A (the second preset current threshold), the target charging scenario is still considered met, and DCM mode is maintained. Only when the current continues to rise to 13A (> 12A) will it exit DCM mode and switch to CCM mode. Conversely, if the threshold for switching from CCM mode to DCM mode is 10A, and the threshold for switching back from DCM mode to CCM mode is 12A, the 2A hysteresis between the two effectively prevents charging instability caused by repeated mode switching when the current fluctuates between 10A and 12A. Figure 10The red area represents the waveform output status of the motor controller for the upper bridge arm power switches (first power switch S1, third power switch S3, and fifth power switch S5), while the blue area represents the waveform output status of the motor controller for the lower bridge arm power switches (second power switch S2, fourth power switch S4, and sixth power switch S6). A high waveform output status indicates that the corresponding switch needs to be turned on.

[0055] This invention achieves accurate identification of low-current scenarios by setting different thresholds based on different control modes. This prevents the magnetic ring from overheating when the current is below the first preset current threshold in CCM mode, and also prevents frequent mode switching caused by small current fluctuations in DCM mode. Furthermore, the second preset current threshold is higher than the first preset current threshold, utilizing the hysteresis effect to improve system stability, ensuring a continuous and smooth charging process, and balancing magnetic ring thermal safety with a superior charging experience.

[0056] In some optional implementations, step S102 above includes: Step b1: Control the second power switch, the fourth power switch and the sixth power switch to be turned on simultaneously within their respective control cycles, and control the second power switch, the fourth power switch and the sixth power switch to be turned off simultaneously after a preset on time; Step b2: Keep the first power switch, the third power switch, and the fifth power switch off.

[0057] Specifically, when the target charging scenario is met, the embodiments of the present invention execute the DCM mode through the control logic of synchronously turning on and off the lower bridge arm power switch and turning off the upper bridge arm power switch throughout the process, so as to ensure the boost effect.

[0058] The second power switch S2, the fourth power switch S4, and the sixth power switch S6, as lower bridge arm power switches, each have an independent control cycle (i.e., an independent switching timing cycle for each phase winding). However, due to the adoption of an in-phase switching strategy, their control cycles are completely synchronized. In other words, the turn-on start time, turn-on duration, and turn-off time of the second power switch S2, the fourth power switch S4, and the sixth power switch S6 are completely synchronized, with no timing difference.

[0059] The preset time, i.e., the synchronous conduction duration of the second power switch S2, the fourth power switch S4, and the sixth power switch S6, needs to be determined based on the duty cycle calculated according to the boost demand. For example... Figure 11As shown, during the actual control process, the motor controller's control module simultaneously sends conduction signals to the second power switch S2, the fourth power switch S4, and the sixth power switch S6. Within the conduction duty cycle of the control period, all three are synchronously in the conduction state. At this time, the current path of the DC charging pile is "charging pile positive terminal → motor neutral point → motor three-phase winding → conducting lower bridge arm power switch → lower bridge arm source common terminal → charging pile negative terminal." The motor's three-phase winding is equivalent to three parallel boost inductors, simultaneously receiving charging pile current and storing magnetic energy. The three-phase current synchronously rises linearly from 0 to its peak value. When the conduction time ends, the control module simultaneously sends a shutdown signal to the lower bridge arm power switch, and all three are synchronously disconnected, ending the energy storage phase and entering the energy release and boost phase.

[0060] During the above process, the first power switch S1, the third power switch S3, and the fifth power switch S5 are kept off. The upper bridge arm power switch remains off throughout the entire intermittent conduction mode charging process, not actively participating in current conduction, and only relying on its integrated body diode to provide a freewheeling path. When the second power switch S2, the fourth power switch S4, and the sixth power switch S6 are simultaneously disconnected, the magnetic energy stored in the motor's three-phase windings begins to be released. The current path switches to "motor three-phase windings → upper bridge arm power switch body diode → main positive relay → battery positive terminal → battery negative terminal → main negative relay → lower bridge arm source common terminal → motor three-phase windings". The magnetic energy released by the windings is superimposed with the charging pile voltage, and the battery is charged at a voltage higher than that of the charging pile, realizing the boost function.

[0061] This invention employs synchronous on / off switching of the lower bridge arm switch, resulting in simple control logic and eliminating the need for complex timing calibration, thus reducing the software development difficulty of the motor controller. Furthermore, the three-phase windings simultaneously store and release energy, achieving high boost efficiency and quickly meeting the battery's charging voltage requirements. The upper bridge arm switch remains off throughout the entire circuit, with discontinuous current achieved through body diode freewheeling. This strictly limits the H-value variation range of the magnetic ring, ensuring stable charging at low currents below 10A while preventing thermal failure of the magnetic ring, thus balancing charging compatibility and thermal safety.

[0062] In some optional implementations, step S102 above further includes: Step c1: Control the second power switch, the fourth power switch and the sixth power switch to conduct at a preset angle with phase shift within their respective control cycles, and control the second power switch, the fourth power switch and the sixth power switch to turn off after a preset conduction time. Step c2: Keep the first power switch, the third power switch, and the fifth power switch off.

[0063] Specifically, when the target charging scenario is met, this implementation method executes the DCM mode through the control logic of phase-shift control of the lower bridge arm power switch and full shutdown of the upper bridge arm power switch. This ensures the thermal safety of the magnetic ring while further reducing current ripple and improving charging stability.

[0064] First, the second power switch S2, the fourth power switch S4, and the sixth power switch S6 are controlled to conduct at a preset angle with phase shift within their respective control cycles, and then turned off after a preset conduction time. It should be clarified that the second power switch S2, the fourth power switch S4, and the sixth power switch S6, as lower bridge arm power switches, each have an independent control cycle, and the length of their control cycles is exactly the same, but there is a fixed preset angle difference in the start time of conduction. For example... Figure 12 As shown, in this embodiment, the preset angle is 60°, that is, the control cycle of the fourth power switch S4 is 60° behind the second power switch S2, and the control cycle of the sixth power switch S6 is 60° behind the fourth power switch S4, forming a timing logic of "sequential lag and cyclic conduction".

[0065] The preset time, i.e., the independent conduction duration of each lower bridge arm switch, needs to be determined based on the boost demand and phase reversal timing calculations. For example, under the condition of a charging pile voltage of 450V and a battery voltage of 950V, the preset time is 30μs (corresponding to a duty cycle of 0.3). In the actual control process, it is assumed that the motor controller's control module sends control signals according to the following timing sequence: The control cycle of the second power switch S2 (assumed to be 100μs) sends an on signal within 0~30μs and an off signal within 30~100μs; The control cycle of the fourth power switch S4 is out of phase by 60° (corresponding to a time difference of 60° / 360°×100μs≈16.7μs). A turn-on signal is sent within 16.7~46.7μs, and the fourth power switch S4 is in the turn-on state; a turn-off signal is sent within 46.7~100μs and 0~16.7μs, and the fourth power switch S4 is in the turn-off state. The control cycle of the sixth power switch S6 is out of phase by 60° compared to the fourth power switch S4 (total time difference ≈ 33.4 μs). A turn-on signal is sent within 33.4~63.4 μs, and the sixth power switch S6 is in the turn-on state; a turn-off signal is sent within 63.4~100 μs and 0~33.4 μs, and the sixth power switch S6 is in the turn-off state.

[0066] During the period of 63.4~100μs, the second power switch S2, the fourth power switch S4, and the sixth power switch S6 are all disconnected, and the three-phase windings enter the energy release stage.

[0067] During the entire phase-shifting process, the energy storage phases of the three-phase windings partially overlap, ensuring the continuous flow of the charging pile's output current and avoiding voltage fluctuations caused by current interruption. At the same time, the peak current of each phase winding is controlled within a reasonable range.

[0068] During the above process, the first power switch S1, the third power switch S3, and the fifth power switch S5 are kept off. The upper bridge arm power switches are always in the off state and do not actively participate in current conduction, relying solely on their integrated body diodes to provide a freewheeling path.

[0069] Through the aforementioned technical means, this embodiment of the invention controls the lower bridge arm switch to conduct in a staggered phase, significantly reducing the ripple amplitude of the charging current, avoiding voltage fluctuations caused by current concentration, and improving the stability of the charging process. Furthermore, the energy storage and release processes of the three-phase windings are sequentially connected, ensuring continuous current flow in the charging pile and improving energy utilization efficiency. The upper bridge arm switch is completely off, and the current is discontinuous through the body diode freewheeling. Combined with staggered phase control, the H-value variation law of the magnetic ring is further optimized. While ensuring stable charging with a small current below 10A, the heat loss of the magnetic ring is minimized, balancing charging stability, efficiency, and thermal safety.

[0070] In some alternative implementations, the method further includes: Step S103: When the target charging scenario is not met, the power switching transistor of the inverter is controlled in continuous conduction mode.

[0071] Specifically, such as Figure 13 As shown, when the DC charging current is used to identify that the preset low-current charging scenario is not met (i.e., the charging current is greater than or equal to the preset current threshold), this embodiment uses CCM mode to control the power switching transistors of the inverter. By alternating the conduction of the lower bridge arm switching transistor for energy storage and the upper bridge arm switching transistor for energy release, the current is ensured to flow continuously, taking into account both the high-current charging efficiency and the thermal safety of the three-phase magnetic ring.

[0072] In some optional implementations, step S103 above includes: Step d1: Control the second power switch, the fourth power switch and the sixth power switch to be turned on simultaneously within their respective control cycles, and control the second power switch, the fourth power switch and the sixth power switch to be turned off simultaneously after a preset on time; Step d2: During the control cycle of the second power switch, when the second power switch is off, the first power switch is turned on; when the second power switch is on, the first power switch is turned off. Step d3: During the control cycle of the fourth power switch, when the fourth power switch is off, the third power switch is turned on; when the fourth power switch is on, the third power switch is turned off. Step d4: During the control cycle of the sixth power switch, when the sixth power switch is off, the fifth power switch is turned on; when the sixth power switch is on, the fifth power switch is turned off.

[0073] Specifically, when the target charging scenario is not met, the inverter power switching transistors are controlled in CCM mode. The core of this control is to ensure the continuous flow of motor inductor current through the alternating conduction of "synchronous energy storage in the lower bridge arm and corresponding freewheeling in the upper bridge arm," thus adapting to the high-current, high-efficiency charging requirements. For example, the specific control process is as follows: The second power switch S2, the fourth power switch S4, and the sixth power switch S6 serve as the lower bridge arm switches. Although each has an independent control cycle, their control cycles are perfectly aligned due to the adoption of a phase-in-phase control strategy, ensuring synchronous conduction and shutdown. The preset time is the synchronous conduction duration of the lower bridge arm, determined by the boost voltage requirement. During this stage, the lower bridge arm conducts synchronously while the upper bridge arm remains completely off. The current path is: "charging pile positive terminal → motor neutral point → three-phase winding → lower bridge arm power switch → lower bridge arm source common terminal → charging pile negative terminal." The three-phase windings store energy synchronously, and the current increases linearly.

[0074] When the preset time ends, the lower bridge arm power switch is simultaneously turned off, and immediately the corresponding upper bridge arm's first power switch S1, third power switch S3, and fifth power switch S5 are turned on. The turning-off action of the upper bridge arm and the corresponding lower bridge arm are seamlessly connected, ensuring that the motor inductor current continues to flow through the turned-on upper bridge arm switch, forming a continuous cycle of energy storage in the lower bridge arm and energy release in the upper bridge arm, thus achieving boost charging.

[0075] Through the above technical means, under high current scenarios (≥10A in this embodiment), the three-phase magnetic ring works stably in the saturation region with minimal hysteresis loss, which not only ensures high current charging efficiency but also eliminates concerns about magnetic ring overheating, thus adapting to high power charging requirements.

[0076] In some optional implementations, step S103 above further includes: Step e1: Control the second power switch, the fourth power switch and the sixth power switch to conduct at a preset angle with phase shift within their respective control cycles, and control the second power switch, the fourth power switch and the sixth power switch to turn off after a preset conduction time. Step e2: During the control cycle of the second power switch, when the second power switch is off, the first power switch is turned on; when the second power switch is on, the first power switch is turned off. Step e3: During the control cycle of the fourth power switch, when the fourth power switch is off, the third power switch is turned on; when the fourth power switch is on, the third power switch is turned off. Step e4: During the control cycle of the sixth power switch, when the sixth power switch is off, the fifth power switch is turned on; when the sixth power switch is on, the fifth power switch is turned off.

[0077] Specifically, the embodiments of the present invention implement phase-shift control in CCM mode. By storing energy in phase-shift mode in the lower bridge arm and corresponding freewheeling in the upper bridge arm, ripple is reduced while ensuring current continuity, thus adapting to high-current, high-efficiency charging.

[0078] The second power switch S2, the fourth power switch S4, and the sixth power switch S6 each have independent control cycles, and are turned on at a preset 60° phase shift. The control cycle of the fourth power switch S4 lags behind that of the second power switch S2 by 60°, and the control cycle of the sixth power switch S6 lags behind that of the fourth power switch S4 by 60°. The on-time is uniformly set based on the boost voltage requirement. The three switches are turned on and off sequentially to achieve timed energy storage of the three-phase windings, avoiding excessively high ripple peaks caused by current concentration.

[0079] Furthermore, when the lower bridge arm is turned off, the corresponding upper bridge arm is turned on. After the second power switch S2 is turned off, the first power switch S1 of the corresponding upper bridge arm immediately turns on, and the same applies to the third power switch S3 and the fifth power switch S5. The control cycles of the upper bridge arm and the corresponding lower bridge arm are synchronized and phase-shifted, ensuring that the motor inductor current flows continuously through the turned-on upper bridge arm switch (without interruption), forming a continuous cycle of time-sharing energy storage and release. This achieves both boost charging and further reduces current ripple through phase-shift control. In high-current scenarios, the three-phase magnetic ring operates stably in the saturation region with low hysteresis loss, balancing charging efficiency and stability.

[0080] In some optional implementations, in intermittent conduction mode, the preset time for controlling the conduction of the lower arm power switch is determined by the following steps: Step f1: Based on the first duty cycle parameter, the second duty cycle, the charging pile output voltage and the battery voltage, establish the volt-second balance equation. The volt-second balance equation is used to indicate that the average voltage across the inductor in the motor winding is zero within one control cycle. The first duty cycle parameter is the unknown parameter of the duty cycle for controlling the lower bridge arm power switch to conduct. The second duty cycle is the duty cycle of the freewheeling current of the body diode in the upper bridge arm power switch. Step f2: Based on the charging pile output voltage, battery voltage, battery current, motor equivalent inductance during boost charging, and control cycle, establish a power balance equation. The power balance equation is used to represent the balance between motor output power and battery input power within one switching cycle. Step f3: Solve the volt-second balance equation and the power balance equation simultaneously to obtain the first duty cycle parameter and thus the first duty cycle. Step f4: Determine the preset time based on the product of the first duty cycle and the control cycle.

[0081] Specifically, this invention provides a method for calculating the conduction time (i.e., preset time) of the lower arm power switch in a vehicle motor boost charging system when the circuit operates in DCM mode. By following the inductor volt-second balance and system power balance, the precise duty cycle is solved by solving simultaneous equations, thereby achieving precise control of the switch and ensuring the stability and high efficiency of the system over a wide load range.

[0082] First, establish the volt-second balance equation. Within a complete control cycle, the current in the equivalent inductance of the motor winding rises from zero, then falls back to zero and remains there for a period, exhibiting a discontinuous triangular waveform. According to the inductor volt-second balance principle, under steady state, the integral of the voltage across the inductor over one cycle is zero. This process involves two conduction phases. In the first phase, the lower bridge arm power switch is turned on, and its duty cycle is unknown, denoted as the first duty cycle parameter D, which is then solved. At this time, the voltage across the inductor is the charging pile output voltage Vin. In the second phase, the lower bridge arm is turned off, and the motor winding current freewheels through the body diode of the upper bridge arm power switch. The duty cycle in this phase is denoted as the second duty cycle D1. At this time, the voltage across the inductor is Vin minus the battery voltage Vo. In the third phase, the current is zero, and the inductor voltage is also zero. Therefore, the established volt-second balance equation is: Vin D+(Vin-Vo) D1=0. This equation reflects the voltage-time relationship during the inductor's energy storage and release process, and is one of the fundamental conditions for solving unknown quantities.

[0083] Next, a power balance equation is established. Ideally, ignoring switching and line losses, all power output from the charging pile should be transferred to the battery side. The output power at the charging pile side equals its output voltage Vin multiplied by the average input current I_in_avg. In DCM mode, the average input current I_in_avg equals the area of ​​the peak inductor current triangle (representing the total charge) divided by the switching cycle. The peak inductor current I_peak can be expressed by the formula I_peak = (Vin / L). (D The calculation is as follows: L is the equivalent inductance of the motor during boost charging, and T is the control cycle. The duty cycle of the inductor current waveform is (D+D1), therefore the average input current is I_in_avg=(1 / 2). I_peak (D+D1). The input power on the battery side is the product of the square of the battery voltage Vo and the battery current Io. The battery current Io is determined by the ratio of the battery voltage Vo to the battery internal resistance R. According to the law of conservation of power, the power balance equation is: Vin [1 / 2 (Vin D T / L) [(D+D1)]=Vo^2 / R. This equation, from the perspective of energy transfer, relates the external electrical parameters of the circuit with the internal switching states and device parameters.

[0084] Finally, solve the two equations simultaneously to obtain the first duty cycle. Substitute the relationship derived from the volt-second balance equation in step f1 into the power balance equation in step f2. After algebraic simplification and elimination of the intermediate variable D1, the analytical solution for the first duty cycle parameter D can be directly obtained. The final formula for calculating the first duty cycle D is: D=(Vo / Vin) sqrt(((2 L Io) (Vo / Vin-1)) / (Vo T).

[0085] Therefore, in DCM mode, the first duty cycle D of the lower bridge arm switch is not a fixed value, but is proportional to the input-output voltage ratio, battery current, equivalent inductance, and the square root of the control cycle. The controller only needs to collect parameters such as Vin, Vo, and Io in real time, and use the pre-stored L and T values ​​to calculate the accurate first duty cycle D under the current operating condition online.

[0086] After obtaining the first duty cycle D, multiplying it by the control period T yields the preset time Ta within one control period during which the lower arm power switch needs to be precisely turned on in order for the system to reach the predetermined boost target, thus achieving precise control of the power switch.

[0087] Related technologies often calculate the duty cycle in CCM mode by only considering the ratio of the charging pile output voltage to the battery voltage, which can easily lead to slow regulation, large output voltage ripple, or even instability. This embodiment obtains accurate solutions by solving the volt-second balance equation and the power balance equation, enabling the system to quickly and accurately maintain the target voltage at any load point, resulting in excellent dynamic response performance. It avoids the risks of increased stress on the switching transistor, inductor saturation, or overcurrent caused by duty cycle calculation errors, ensuring that power devices operate in optimal condition and reducing losses and thermal stress.

[0088] Figure 14 This is a schematic diagram of a trolley boost charging circuit provided in an embodiment of the present invention.

[0089] The electric vehicle boost charging circuit of this invention includes: a motor controller, a motor, an inverter, a bus capacitor, a three-phase magnetic ring, a main positive relay, and a main negative relay.

[0090] The DC charging pile's positive terminal is connected to the motor's neutral point, and the DC charging pile's negative terminal is connected to the common source terminal of the inverter's lower arm power switch. The common drain terminal of the inverter's upper arm power switch is connected to the battery's positive terminal via a main positive relay, and the battery's negative terminal is connected to the common source terminal of the lower arm power switch via a main negative relay. The inverter's three-phase output terminals are connected to the motor's three-phase input terminals. A bus capacitor is connected between the common drain terminal of the upper arm power switch and the common source terminal of the lower arm power switch. The motor controller is connected to the control terminals of both the upper and lower arm power switches. A three-phase magnetic ring is located at the inverter's three-phase output terminals, and the upper arm power switch integrates a body diode.

[0091] In addition, the upper arm power switch includes a first power switch S1, a third power switch S3, and a fifth power switch S5, and the lower arm power switch includes a second power switch S2, a fourth power switch S4, and a sixth power switch S6. The output terminals of the first power switch S1 and the second power switch S2 are connected to the same phase input terminal of the motor, the output terminals of the third power switch S3 and the fourth power switch S4 are connected to the same phase input terminal of the motor, and the output terminals of the fifth power switch S5 and the sixth power switch S6 are connected to the same phase input terminal of the motor.

[0092] The motor controller includes a control module, which is used to identify whether the target charging scenario is met based on the DC charging current. When the target charging scenario is met, the control module uses an intermittent conduction mode to control the power switching transistors of the inverter. The intermittent conduction mode is used to keep the upper bridge arm power switching transistors off in each control cycle of DC charging and to control the lower bridge arm power switching transistors to conduct for a preset time. The charging current of the target charging scenario is less than a preset current threshold.

[0093] This invention also provides a vehicle in which the electric vehicle boost charging circuit described above is deployed.

[0094] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded via a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.

[0095] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0096] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for boosting the voltage of electric vehicles for charging, characterized in that, A motor controller used in a DC boost charging circuit, wherein the upper bridge power switch of the inverter in the DC boost charging circuit integrates a body diode, the method comprising: Obtain the DC charging current and identify whether the target charging scenario is met based on the DC charging current, wherein the charging current of the target charging scenario is less than a preset current threshold. When the target charging scenario is met, the power switching transistors of the inverter are controlled in an intermittent conduction mode. The intermittent conduction mode is used to keep the upper bridge arm power switching transistors off in each control cycle of DC charging and to control the lower bridge arm power switching transistors of the inverter to conduct for a preset time.

2. The method according to claim 1, characterized in that, The step of identifying whether the target charging scenario is met based on the DC charging current includes: Get the current control mode; If the current control mode is a continuous conduction mode or an initialization mode, when the DC charging current is less than the first preset current threshold, it is determined that the target charging scenario is met. The continuous conduction mode is used to control the upper bridge arm power switch and the lower bridge arm power switch to conduct alternately in each control cycle of DC charging. The initialization mode is used to characterize the state of the DC charging pile at the initial moment of charging the battery. If the current control mode is the intermittent conduction mode, when the DC charging current is less than the second preset current threshold, it is determined that the target charging scenario is met, and the second preset current threshold is greater than the first preset current threshold.

3. The method according to claim 1, characterized in that, The upper bridge arm power switch includes a first power switch (S1), a third power switch (S3), and a fifth power switch (S5), and the lower bridge arm power switch of the inverter includes a second power switch (S2), a fourth power switch (S4), and a sixth power switch (S6); the step of controlling the inverter's power switches using an intermittent conduction mode when the target charging scenario is met includes: The second power switch (S2), the fourth power switch (S4), and the sixth power switch (S6) are controlled to be turned on simultaneously within their respective control cycles, and the second power switch (S2), the fourth power switch (S4), and the sixth power switch (S6) are controlled to be turned off simultaneously after the preset time. The first power switch (S1), the third power switch (S3), and the fifth power switch (S5) are kept off.

4. The method according to claim 1, characterized in that, The upper bridge arm power switch includes a first power switch (S1), a third power switch (S3), and a fifth power switch (S5), and the lower bridge arm power switch of the inverter includes a second power switch (S2), a fourth power switch (S4), and a sixth power switch (S6); the step of controlling the inverter's power switches using an intermittent conduction mode when the target charging scenario is met includes: The second power switch (S2), the fourth power switch (S4), and the sixth power switch (S6) are controlled to conduct at a preset angle with phase shift within their respective control cycles, and the second power switch (S2), the fourth power switch (S4), and the sixth power switch (S6) are controlled to turn off after the preset conduction time. The first power switch (S1), the third power switch (S3), and the fifth power switch (S5) are kept off.

5. The method according to claim 2, characterized in that, The method further includes: When the target charging scenario is not met, the power switching transistors of the inverter are controlled using the continuous conduction mode.

6. The method according to claim 5, characterized in that, The upper bridge arm power switch includes a first power switch (S1), a third power switch (S3), and a fifth power switch (S5), and the lower bridge arm power switch of the inverter includes a second power switch (S2), a fourth power switch (S4), and a sixth power switch (S6); the step of controlling the inverter's power switches using the continuous conduction mode when the target charging scenario is not met includes: The second power switch (S2), the fourth power switch (S4), and the sixth power switch (S6) are controlled to be turned on simultaneously within their respective control cycles, and the second power switch (S2), the fourth power switch (S4), and the sixth power switch (S6) are controlled to be turned off simultaneously after the preset time. During the control cycle of the second power switch (S2), when the second power switch (S2) is off, the first power switch (S1) is turned on; when the second power switch (S2) is on, the first power switch (S1) is turned off. During the control cycle of the fourth power switch (S4), when the fourth power switch (S4) is off, the third power switch (S3) is turned on; when the fourth power switch (S4) is turned on, the third power switch (S3) is turned off. During the control cycle of the sixth power switch (S6), when the sixth power switch (S6) is off, the fifth power switch (S5) is turned on, and when the sixth power switch (S6) is turned on, the fifth power switch (S5) is turned off.

7. The method according to claim 5, characterized in that, The upper bridge arm power switch includes a first power switch (S1), a third power switch (S3), and a fifth power switch (S5), and the lower bridge arm power switch of the inverter includes a second power switch (S2), a fourth power switch (S4), and a sixth power switch (S6); the step of controlling the inverter's power switches using the continuous conduction mode when the target charging scenario is not met includes: The second power switch (S2), the fourth power switch (S4), and the sixth power switch (S6) are controlled to conduct at a preset angle with phase shift within their respective control cycles, and the second power switch (S2), the fourth power switch (S4), and the sixth power switch (S6) are controlled to turn off after the preset conduction time. During the control cycle of the second power switch (S2), when the second power switch (S2) is off, the first power switch (S1) is turned on; when the second power switch (S2) is on, the first power switch (S1) is turned off. During the control cycle of the fourth power switch (S4), when the fourth power switch (S4) is off, the third power switch (S3) is turned on; when the fourth power switch (S4) is turned on, the third power switch (S3) is turned off. During the control cycle of the sixth power switch (S6), when the sixth power switch (S6) is off, the fifth power switch (S5) is turned on, and when the sixth power switch (S6) is turned on, the fifth power switch (S5) is turned off.

8. The method according to claim 1, characterized in that, In the intermittent conduction mode, the preset time for controlling the conduction of the lower bridge arm power switch is determined by the following steps: A volt-second balance equation is established based on the first duty cycle parameter, the second duty cycle, the charging pile output voltage, and the battery voltage. The volt-second balance equation is used to indicate that the average voltage across the inductor in the motor winding is zero within one control cycle. The first duty cycle parameter is an unknown parameter of the duty cycle for controlling the conduction of the lower bridge arm power switch. The second duty cycle is the duty cycle of the freewheeling current of the body diode in the upper bridge arm power switch. A power balance equation is established based on the output voltage of the charging pile, the battery voltage, the battery current, the equivalent inductance of the motor during boost charging, and the control cycle. The power balance equation is used to represent the balance between the motor output power and the battery input power within one switching cycle. By combining the volt-second balance equation and the power balance equation, the first duty cycle parameter is solved to obtain the first duty cycle; The preset time is determined based on the product of the first duty cycle and the control cycle.

9. A boost charging circuit for electric vehicles, characterized in that, include: Motor controller, motor, inverter, bus capacitor, three-phase magnetic ring, main positive relay and main negative relay; The positive terminal of the DC charging pile is connected to the neutral point of the motor, the negative terminal of the DC charging pile is connected to the common source terminal of the lower arm power switch of the inverter, the common drain terminal of the upper arm power switch of the inverter is connected to the positive terminal of the battery through the main positive relay, the negative terminal of the battery is connected to the common source terminal of the lower arm power switch through the main negative relay, the three-phase output terminal of the inverter is connected to the three-phase input terminal of the motor, the bus capacitor is connected between the common drain terminal of the upper arm power switch and the common source terminal of the lower arm power switch, the motor controller is connected to the control terminal of the upper arm power switch and the control terminal of the lower arm power switch respectively, the three-phase magnetic ring is set at the three-phase output terminal of the inverter, and the upper arm power switch integrates a body diode. The motor controller is used to perform the method according to any one of claims 1-8.

10. The electric vehicle boost charging circuit according to claim 9, characterized in that, The upper arm power switch includes a first power switch (S1), a third power switch (S3), and a fifth power switch (S5). The lower arm power switch includes a second power switch (S2), a fourth power switch (S4), and a sixth power switch (S6). The output terminals of the first power switch (S1) and the second power switch (S2) are connected to the same phase input terminal of the motor. The output terminals of the third power switch (S3) and the fourth power switch (S4) are connected to the same phase input terminal of the motor. The output terminals of the fifth power switch (S5) and the sixth power switch (S6) are connected to the same phase input terminal of the motor.

11. A vehicle, characterized in that, The vehicle is equipped with a trolley boost charging circuit as described in claim 9 or 10.

12. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing a computer to perform the method of any one of claims 1 to 8.

13. A computer program product, characterized in that, Includes computer instructions for causing a computer to perform the method of any one of claims 1 to 8.

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