Six-phase motor-based electric driver integrated potential isolation AC vehicle-mounted charger

Abstract

The invention provides an AC on-board charger based on electric driver integrated potential isolation of a six-phase motor. The present document describes, among other things, a vehicle power system that includes a traction battery, a six-phase inverter divided into two sets of six switches, a six-phase motor, and a pair of switches. In a driving mode, the switch configures the inverter to connect the traction battery and the motor. In a plug-in mode, the system is reconfigured such that one set of switches connects an AC source to the motor and another set of switches connects the motor to the traction battery.

Description

Technical Field

[0001] This disclosure relates to automotive electrical systems. Background Technology

[0002] Electric vehicles and hybrid electric vehicles include components that work together to provide propulsion and energy management. These components include: a traction battery that stores electrical energy; an electric motor that converts electrical energy into mechanical energy to drive the vehicle; and an inverter that converts the DC power from the battery into AC power suitable for the motor. A power electronic system, including components such as converters and controllers, manages the energy flow between the battery, the motor, and other subsystems. Summary of the Invention

[0003] A vehicle includes an electrical system comprising a traction battery, a six-phase inverter with two sets of six switches, a six-phase motor, and a pair of switches. During driving mode, these switches are operated to connect the two sets of switches between the traction battery and the six-phase motor. During plug-in mode, one set of switches connects the AC power source to the six-phase motor, while the other set connects the six-phase motor to the traction battery.

[0004] One method involves operating switches during the vehicle's plug-in mode such that one set of six switches in a six-phase inverter is electrically connected between an AC source and a six-phase motor. Simultaneously, another set of six switches in the inverter is electrically connected between the six-phase motor and a traction battery. This configuration allows power to flow sequentially from the AC source through the first set of switches, the six-phase motor, and the second set of switches to the traction battery.

[0005] A vehicle electrical system includes a traction battery, a six-phase inverter with two sets of switches, a six-phase motor, a pair of switches, and one or more controllers. These controllers are programmed to disconnect the pair of switches during plug-in mode, thereby allowing power from an AC source to flow sequentially through one set of switches, the six-phase motor, and another set of switches to the traction battery. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of a typical AC car charger.

[0007] Figures 2A to 2C This is a schematic diagram of a vehicle including an electric drive based on a six-phase motor.

[0008] Figure 3 This is a block diagram of AC on-board charging power factor control.

[0009] Figures 4A to 4B This is a block diagram of inverter switch control.

[0010] Figure 5It is a graph of the grid voltage and current.

[0011] Figure 6 It is a graph showing the battery voltage and current.

[0012] Figure 7 It is a graph of DC bus voltage and inductor current.

[0013] Figure 8 It is a graph of the winding current of a six-phase motor. Detailed Implementation

[0014] This document describes embodiments. However, it should be understood that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The drawings are not necessarily drawn to scale. Some features may be enlarged or minimized to show details of specific components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art.

[0015] The various features shown and described with reference to any of the accompanying drawings may be combined with features shown in one or more other drawings to produce embodiments not explicitly shown or described. The combinations of features shown provide representative embodiments for typical applications. However, for a particular application or implementation, various combinations and modifications of features consistent with the teachings of this disclosure may be desired.

[0016] Figure 1 An existing AC on-board charger 10 for electric and hybrid electric vehicles is shown, designed to convert AC power from grid 12 into DC power suitable for charging traction battery 14. The system begins with an input from AC grid 12, which typically provides the necessary power at a frequency of 50Hz or 60Hz. Inductor 14 is connected in series with AC grid 12 to filter the input, thereby reducing high-frequency noise and harmonics. Diodes 16 and 18 are part of a full-bridge rectifier that, together with diodes 20 and 22, converts the AC input into a pulsating DC voltage. After the rectifier bridge, inductor 24 further filters the DC current, smoothing it to reduce ripple and provide a more stable output. Diode 26, connected in series with inductor 24, ensures unidirectional current flow to capacitor 28 and subsequent circuit stages.

[0017] Capacitor 28 is connected in parallel with the output of diode 26. Switch 30 is a control switch connected across inductor 24, used to manage power flow by disconnecting or connecting inductor 24 to the negative busbar. Switches 32, 34, 36, and 38 form a full-bridge inverter that converts a smooth DC voltage back to the high-frequency AC voltage necessary for energy transfer and operation of the high-frequency transformer 40. The transformer 40 provides potential isolation between the input and output circuits and steps up or down the voltage as needed.

[0018] On the secondary side of the high-frequency transformer 40, switches 42, 44, 46, and 48 form another full-bridge rectifier, which converts the high-frequency AC voltage back to a DC voltage suitable for charging the traction battery 14. A capacitor 50 connected across the output of this rectifier smooths the DC voltage to ensure a stable output from the traction battery 14. The traction battery 14, connected to the output of the charger, stores the converted DC power for use by the vehicle's electric drivetrain.

[0019] Such AC on-board chargers require space and have associated weight. Therefore, a six-phase motor-based electric drive system is proposed, integrating a potential-isolated AC on-board charger for electric and hybrid electric vehicles. A six-phase motor with two isolated neutral points is used. Unlike other systems that may use a three-phase open-end winding motor or a conventional motor with a single neutral point, the proposed design allows the motor to function as an isolation transformer during AC on-board charging. This capability eliminates the need for a 50Hz or 60Hz isolation transformer. Potential isolation is provided by the six-phase motor without the need for an additional high-frequency transformer or dual active bridge typically required in conventional chargers.

[0020] The system operates in two distinct modes: vehicle driving mode and AC on-board charging mode. In vehicle driving mode, the AC grid is disconnected from the on-board charger, the active switch is off, and the ignition switch is closed. During this mode, the six-phase inverter drives the six-phase motor to propel the vehicle. The traction battery powers the motor via the inverter during motor driving, and during regenerative braking, the generated electricity is sent back to the battery, allowing the system to be used as a conventional electric drive.

[0021] In AC on-board charging mode, the vehicle is stationary, and the motor operates as a three-phase isolation transformer to provide the necessary potential isolation. The AC grid is connected to the input of the on-board charger, and the switch is open. The control strategy in this mode involves managing the power factor correction (PFC) circuitry and controlling other switches to maintain a constant DC bus voltage and achieve unity power factor in the power grid. This involves generating sinusoidal control variables with specific amplitudes, frequencies, and phase angles. The amplitudes and phase angles of these variables are derived from the battery voltage, current, inverter base frequency, and motor inductance.

[0022] The circuitry in this system is configured to facilitate switching between two modes. In vehicle driving mode, the six-phase inverter and motor operate in a conventional manner, driving the vehicle and managing energy flow during motor drive and regenerative braking. In AC on-board charging mode, the motor windings act as a high-frequency transformer, providing potential isolation without additional components. A PFC control method maintains a constant DC bus voltage while ensuring unity power factor, and a switching control strategy enables efficient inverter operation.

[0023] Simulation results demonstrate the effectiveness of the system in charging a 600V traction battery at a charging current of 6.8A (4kW) and a grid current of 34.4A rms. A power factor of 0.9993 was achieved, and the total harmonic distortion (THD) of the grid current was 3.3%. The six-phase motor currents exhibit a sinusoidal waveform, indicating effective power transfer and potential isolation.

[0024] A six-phase inverter is a power electronic device designed to convert DC to AC, which has six distinct phases, each shifted by 60 degrees. A six-phase inverter architecture typically includes two sets of switches, each controlling three phases of the motor. These switches, usually implemented using insulated-gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs), operate in a coordinated manner to produce the desired AC waveform.

[0025] Compared to traditional three-phase inverters, the potential advantage of six-phase inverters lies in their ability to generate a smoother and more continuous torque output. This results in reduced torque ripple and lower harmonic distortion. Additionally, the increased number of phases provides redundancy; in the event of a phase loss or switching, the system can continue operating with the remaining phases.

[0026] Operating a six-phase inverter involves control strategies that ensure the timing and sequencing of switches. Pulse width modulation (PWM) technology can be used to modulate the switching signals, thereby controlling the amplitude and frequency of the output AC voltage. Other control algorithms, such as vector control or direct torque control, are used to optimize the performance of the motor drive, enabling a dynamic response to changing load conditions.

[0027] PWM can involve adjusting the duration of the inverter switch's on-time within each cycle to control the voltage and current supplied to the motor. By modulating these pulses, PWM creates an effective AC waveform from the DC input, thereby allowing control of the motor's speed and torque.

[0028] Vector control (also known as field-oriented control) takes this a step further by decoupling the torque and flux control of a motor. By using known mathematical transformations to convert the three-phase current into a two-axis system (dq axis), vector control allows for independent control of the flux and torque-generating components of the current. This can lead to faster dynamic response and better control over motor performance.

[0029] On the other hand, direct torque control directly adjusts the motor's torque and flux by selecting an appropriate voltage vector from a predefined lookup table. Unlike vector control, direct torque control does not rely on transformations or coordinate systems, but instead uses real-time feedback of the motor's torque and flux to make control decisions.

[0030] In practical applications, six-phase inverters can offer benefits in terms of power density and thermal management. By distributing the current load across six phases instead of three, thermal stress on individual components is reduced.

[0031] A six-phase motor is an electric motor designed to operate with six distinct phases, each spaced 60 degrees apart. This motor configuration offers several advantages over traditional three-phase motors, making it ideal for applications requiring high power density, enhanced performance, and redundancy. A six-phase motor comprises six windings, typically arranged in two groups, each with three phases. These windings are evenly distributed around the motor's stator to generate a balanced magnetic field that drives the rotor.

[0032] Figure 2A This represents an electric drive system 52 based on a six-phase motor, which integrates a potential-isolated AC on-board charger for an electric vehicle or hybrid electric vehicle 54. Starting with an input from the AC grid 56 on the left, the AC voltage is first filtered by an inductor 58, which helps reduce high-frequency noise and harmonics. The filtered AC voltage is then rectified by a full-bridge rectifier consisting of diodes 60, 62, 64, and 66, converting the AC input into a pulsating DC voltage. After the rectifier bridge, an inductor 68 smooths this DC current, reducing ripple and providing a more stable output. Diode 70 ensures unidirectional current flow, directing the current to capacitor 72.

[0033] A capacitor 72, positioned in parallel with the outputs of diode 70 and inductor 68, further smooths the DC voltage. The system includes a switch 74, which acts as a control element, managing the connection between the rectified DC output and subsequent stages. This DC voltage is then used by a six-phase inverter 76, which consists of switches 78 to 100 divided into two groups. The first group includes switches 78, 80, 82, 84, 86, and 88, while the second group includes switches 90, 92, 94, 96, 98, and 100. These switches convert the smoothed DC voltage back to the high-frequency AC necessary to drive the six-phase motor 102.

[0034] The motor 102 depicted on the right side of the figure includes windings 104, 106, 108, 110, 112, and 114, which are connected to two isolated neutral points labeled 116 and 118. This motor configuration allows the system to function as an isolation transformer during AC on-board charging, thus providing potential isolation without the need for an additional transformer. Switches 120 and 122 function in the operating modes of the management system. When the vehicle 54 is in driving mode, switches 120 and 122 are closed, connecting the traction battery 124 to the inverter 76 and enabling the motor 102 to propel the vehicle 54. In this mode, the AC power grid 56 is disconnected, and switch 74 is off.

[0035] In AC on-board charging mode, switches 120 and 122 are open, thereby disconnecting motor 102 from the drivetrain and allowing windings 104, 106, 108, 110, 112, and 114 to function as isolation transformers. AC grid 56 is connected via a rectifier and a smoothing stage, and inverter 76 converts DC voltage to high-frequency AC. Windings 104, 106, 108, 110, 112, and 114 then utilize this high-frequency AC to achieve potential isolation while charging traction battery 124. Control strategies may include PFC to maintain a constant DC bus voltage and achieve unity power factor.

[0036] The controller 126 communicates with / controls components of the vehicle 54 and implements the techniques described herein. It can establish communication channels using automotive communication protocols such as CAN (Controller Area Network), LIN (Local Area Network), and / or FlexRay. These protocols enable the controller to send and receive data packets containing operating commands and status information. For example, the controller 126 can send a PWM signal to the inverter 76 to modulate the power supplied to the motor 102, thereby adjusting its speed and torque. It also monitors sensors distributed throughout the vehicle 54 to collect data on parameters such as battery voltage, current, temperature, and motor position. This data can be processed in real time using embedded algorithms to adjust the motor drive and battery management system. Additionally, the controller 126 can manage the operation of other auxiliary systems, such as the HVAC system, regenerative braking system, etc.

[0037] refer to Figure 2B During vehicle operation, several operations occur: 1) disconnecting the AC power grid 56 from the AC on-board charger; 2) turning off switch 74; and 3) closing switches 120 and 122. Therefore, the system has the equivalent circuit shown, and the AC on-board charger function is inactive. Inverter 76 operates to drive motor 102 to propel vehicle 54. During motor drive mode, traction battery 124 delivers power to motor 102 and vehicle 54 via inverter 76. During power generation mode, the generated power is sent back to traction battery 124 via motor 102 and inverter 76. During this operating mode, inverter 76 and motor 102 operate in a conventional manner.

[0038] refer to Figure 2C Vehicle 54 is not driven, and motor 102 acts as a three-phase isolation transformer during AC on-board charging mode. AC grid 56 is connected to the input of the AC on-board charger, and switches 120 and 122 are open. The system has the equivalent circuit shown.

[0039] The control strategies used for this operating mode include PFC control, control of switches 78 to 88, and control of switches 90 to 100.

[0040] Figure 3 This illustrates the use of a constant DC bus voltage V for maintaining the inverter, which consists of switches 78 to 88. dc Simultaneously, it achieves unity power factor PFC control of the AC power grid at voltage V. The control loop uses a reference voltage V. dc_ref Initially, in this example, the reference voltage is set to 400V. This reference voltage represents the desired output voltage level. Actual output voltage V dc It is fed back into the system and at the summation point is compared with V. dc_refThe difference between the desired and actual voltages is then compared. The resulting error signal, representing the difference between the desired and actual voltages, is then passed through a proportional-integral (PI) controller. The PI controller adjusts its output to minimize the voltage error over time, thereby effectively tuning the system to achieve the desired voltage level.

[0041] The multiplier block is used to multiply the output of the first PI controller by the input voltage V. i This step is performed to adjust the control signal based on the available input voltage. Then, this adjusted control signal is summed with the inductor current i at another summing point. L The inductor current is compared to the current flowing through the inductor in the system. The difference between the adjusted control signal and the inductor current is then processed again by a second PI controller.

[0042] The output of the second PI controller is fed into a comparator. The comparator also receives a high-frequency carrier signal fsw, which is associated with a PWM signal used in power electronics to control the switching of the power transistors. The carrier signal and the output of the second PI controller are compared to generate a switching signal at output 74, which controls the state of switch 74 in the power converter. When operating at the correct frequency and duty cycle, switch 74 ensures that the converter maintains the desired output voltage and current by adjusting the energy transfer to the output load.

[0043] Figure 4A and Figure 4B Basic control of switches 78 to 88 and switches 90 to 100 is shown respectively, where V1 to V6 are sinusoidal control variables with amplitude, frequency, and phase angle. Furthermore, V1 to V3 are symmetrical in the three phases, and V4 to V6 are also symmetrical in the three phases.

[0044] For implementation Figure 4A and Figure 4B The purpose of the control factors shown is to obtain the amplitude and phase angle of variables V1 to V6. Define X = M²V dc Y = M1V batt Then the magnitude M1 of variables V1 to V3 is

[0045] M1 = Y / V batt (1)

[0046] Y = (X 2 +32(ωLV batt I batt ) 2 / 9X 2 ) 1 / 2 (2)

[0047] The phase angle difference between V1 and V4 (or V2 and V5, or V3 and V6) is

[0048]

[0049] For the design of M2 and V dc We can base our decision on the battery voltage V. batt Current I batt The inverter base frequency ω and the motor inductance L are used to obtain M1 and the phase angle from equations (1) to (3). Finally, in (4), there exist V1 to V6 to pass. Figure 4A and Figure 4B Control switches 78 to 100 to charge traction battery 124. Of course, a closed-loop control system can be constructed to achieve the purpose of generating V1 to V6, etc.

[0050]

[0051] V4=M2sin(ωt); V5=M2sin(ωt-120°); V6=M2sin(ωt+120°) (4)

[0052] Figures 5 to 8 Simulation results are shown when a 600V traction battery is charged using the proposed AC on-board charger. During the simulation, the AC power grid had a voltage of 120V rms and a frequency of 60Hz, with M1 = 0.677, M2 = 1, and V... dc =400V. For example... Figure 6 As shown, the traction battery charging current is 6.8A (4kW), and the grid current is 34.4A rms. Figure 5 As shown in the diagram. Furthermore, the power factor is 0.9993, and the grid current THD is 3.3%. The six-phase current is shown... Figure 8 The sine wave in the circuit transmits power from the power grid to the traction battery, while the six-phase motor achieves potential isolation between the traction battery and the power grid.

[0053] The algorithms, methods, or processes disclosed herein may be delivered to or implemented by a computer, controller, or processing device, which may include any dedicated electronic control unit or programmable electronic control unit. Similarly, the algorithms, methods, or processes may be stored in many forms as data and instructions executable by a computer or controller, including but not limited to information permanently stored on non-writable storage media such as read-only memory devices and information reproducibly stored on writable storage media such as optical discs, random access memory devices, or other magnetic and optical media. The algorithms, methods, or processes may also be implemented as software executable objects. Alternatively, suitable hardware components, such as application-specific integrated circuits, field-programmable gate arrays, state machines, or other hardware components or devices, or firmware, a combination of hardware and software components, may be used to embody the algorithms, methods, or processes, wholly or partially.

[0054] While exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms covered by the claims. Furthermore, the terms used in this specification are descriptive rather than restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of this disclosure. For example, "controller" and "multiple controllers" may be used interchangeably herein, as the functionality of one controller may be distributed across several controllers, all of which may communicate via standard technologies.

[0055] As previously described, features of various embodiments can be combined to form other embodiments of the invention that may not be explicitly described or shown. While various embodiments may have been described as offering advantages or preferences over other embodiments or prior art implementations in terms of one or more desired characteristics, those skilled in the art will recognize that one or more features or characteristics may be compromised to achieve desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. Thus, embodiments described as less desirable than other embodiments or prior art implementations in terms of one or more characteristics are not outside the scope of this disclosure and may be desirable for a particular application.

Claims

1. A vehicle comprising: The power system includes: a traction battery; A six-phase inverter, wherein the six-phase inverter comprises two groups of six switches; Six-phase motor; And a pair of switches configured to operate during driving mode such that the two sets of electrical connections are between the traction battery and the six-phase motor, and during plug-in mode such that one of the sets is electrically connected between the AC power source and the six-phase motor, and the other of the sets is electrically connected between the six-phase motor and the traction battery.

2. The vehicle of claim 1, wherein the six-phase motor includes windings configured to potential-isolate the two sets during the plug-in mode.

3. The vehicle of claim 2, wherein the winding is further configured such that during the plug-in mode, the six-phase motor operates as a three-phase isolation transformer.

4. The vehicle of claim 2, wherein the winding is connected to two isolated neutral points.

5. The vehicle of claim 1, wherein the pair of switches are closed during the driving mode.

6. The vehicle of claim 1, wherein during the plug-in mode, the pair of switches are disconnected.

7. A method comprising: During the vehicle's plug-in mode, the switches are operated such that one set of six switches of the six-phase inverter is electrically connected between the AC source and the six-phase motor, and another set of six switches of the six-phase inverter is electrically connected between the six-phase motor and the traction battery, to allow power from the AC source to flow sequentially through the set of switches, the six-phase motor, and the other set of switches to the traction battery.

8. The method of claim 7, wherein the operational connection includes disconnecting the switch.

9. The method of claim 7, further comprising, during the driving mode of the vehicle, operating the switch such that the group of electrical connections is between the six-phase motor and the traction battery to allow power from the traction battery to flow through the six-phase inverter to the six-phase motor.

10. The method of claim 9, wherein the operation of electrically connecting the group between the six-phase motor and the traction battery includes closing the switch.

11. A vehicle electrical system, comprising: Traction battery; A six-phase inverter, wherein the six-phase inverter includes two sets of switches; Six-phase motor; A pair of switches; as well as One or more controllers are programmed to disconnect the pair of switches, such that power from an AC source flows sequentially through one of the groups, the six-phase motor, and the other of the group to the traction battery.

12. The vehicle electrical system of claim 11, wherein the one or more controllers are further programmed to close the pair of switches such that power from the traction battery flows through the group to the six-phase motor.

13. The vehicle electrical system of claim 11, wherein the six-phase motor includes windings configured to potential-isolate the group while the power flows sequentially through one of the groups, the six-phase motor, and the other of the group to the traction battery.

14. The vehicle electrical system of claim 13, wherein the winding is further configured such that the six-phase motor selectively operates as a three-phase isolation transformer.

15. The vehicle electrical system of claim 11, wherein each of the groups comprises six switches.

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