Electric drive based on an externally excited synchronous machine, incorporating a galvanically isolated vehicle-internal AC charger.

Abstract

A power system for motor vehicles integrates a power factor correction circuit, an H-bridge power module, a separately excited synchronous machine, a traction inverter, and a traction battery. The system operates in two modes: driving and charging. In driving mode, power flows from the traction battery through the H-bridge power module and the traction inverter to the separately excited synchronous machine, which propels the vehicle. In charging mode, power from an AC source is sequentially routed through the power factor correction circuit, the H-bridge power module, the synchronous machine, and the traction inverter.

Description

AREA OF TECHNOLOGY

[0001] This disclosure concerns performance systems for motor vehicles. GENERAL STATE OF THE ART

[0002] Electric and hybrid vehicles rely on a combination of components that provide propulsion and manage energy. These components include the traction battery, which stores electrical energy; the electric motor, which converts electrical energy into mechanical energy to drive the vehicle; and the inverter, which converts the direct current (DC) power from the battery into alternating current (AC) power suitable for the motor. Additionally, a power electronics system, consisting of converters, controllers, and other subsystems, regulates the energy flow between the battery, motor, and other components. SUMMARY

[0003] A vehicle incorporates a power system with several components: a power factor correction circuit, an H-bridge power module, a separately excited synchronous machine, a traction inverter, and a traction battery. In driving mode, the H-bridge power module and the traction inverter connect the traction battery to the separately excited synchronous machine, thus powering the vehicle. In charging mode, these components are reconfigured so that the H-bridge power module and the synchronous machine connect the power factor correction circuit to the traction inverter, thereby charging the traction battery.

[0004] One method involves changing the connections within a system based on the vehicle's operating mode. In driving mode, power flows from a traction battery through an H-bridge power module and a traction inverter to a separately excited synchronous machine that propels the vehicle. In charging mode, power from an AC source passes through a power factor correction circuit, the H-bridge power module, the synchronous machine, and the traction inverter before reaching the traction battery, thus charging it.

[0005] A power system for motor vehicles consists of a power factor correction circuit, an H-bridge power module, a separately excited synchronous machine, a traction inverter, and a traction battery. During driving mode, power flows from the traction battery through the H-bridge power module and the traction inverter to the separately excited synchronous machine, which propels the vehicle. During charging mode, power from an AC source moves through the power factor correction circuit, the H-bridge power module, the synchronous machine, and the traction inverter before finally reaching the traction battery, thus recharging it. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic diagram of a typical in-vehicle AC charger. Fig. 2A-2C are schematic diagrams of an electric drive based on a separately excited synchronous machine, in which a galvanically isolated vehicle-internal AC charger is integrated. Fig. Figure 3 is a block diagram for power factor control during operation in AC charging mode. Fig. Figure 4 shows the output voltage curve of the H-bridge power module. Fig. 5A are waveforms of a mains voltage, a mains current, and a power factor control current. Fig. 5B are waveforms of the DC bus voltage of the H-bridge and the battery voltage and battery current. Fig. 5C are waveforms of stator winding currents and an output voltage of the H-bridge. DETAILED DESCRIPTION

[0006] This document describes embodiments. However, it is understood that the disclosed embodiments are merely examples and that other embodiments may take different and alternative forms. The figures are not necessarily to scale. Some features may be enlarged or reduced to show details of specific components. Therefore, specific design and functional details disclosed in this document are not to be interpreted as limiting, but merely as a representative basis for teaching the person skilled in the art.

[0007] Various features illustrated and described with respect to any one of the figures can be combined with features illustrated in one or more other figures to create embodiments not expressly illustrated or described. The illustrated combinations of features provide representative embodiments for typical applications. However, various combinations and modifications of the features, consistent with the teachings of this disclosure, may be desirable for specific applications or implementations.

[0008] Fig. Figure 1 illustrates an existing in-vehicle AC charger 10 for electric and hybrid electric vehicles, designed to convert AC power from a grid 12 into DC power suitable for charging a traction battery 14. The system begins with an input from the AC grid 12, which provides the required power, typically at a frequency of 50 Hz or 60 Hz. An inductor 14 is connected in series with the 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, which, together with diodes 20 and 22, converts the AC input into a pulsating DC voltage. Downstream of the rectifier bridge, inductor 24 further filters and smooths the DC to reduce ripple and provide a more stable output.The diode 26, which is connected in series with the inductor 24, ensures a unidirectional current flow towards a capacitor 28 and subsequent circuit stages.

[0009] Capacitor 28 is connected in parallel to the output of diode 26. Switch 30 is a control switch connected across inductor 24 and is 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 the smoothed DC voltage back into high-frequency AC voltage, which is necessary for power transmission and the operation of a high-frequency transformer 40. This transformer 40 provides galvanic isolation between the input and output circuits and increases or decreases the voltage as required.

[0010] 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 into 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 for 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.

[0011] Such in-vehicle AC chargers require space and therefore have added weight. One proposed in-vehicle AC charger is based on an externally excited synchronous machine (EESM) and achieves galvanic isolation by integrating the AC charger into the electric drive system.

[0012] An EESM is a type of electric machine in which the magnetic field required for operation is generated by an external DC power supply rather than by permanent magnets or the rotor itself. This machine typically consists of two main parts: the stator and the rotor. The stator houses a set of three-phase windings through which an alternating current flows, generating a rotating magnetic field. The rotor, located inside the stator, contains a field winding that is excited by an external DC power source. This external excitation can be provided by slip rings and brushes that supply the DC current to the rotor winding.

[0013] The rotor often features laminated iron cores to minimize eddy current losses. The rotor winding can be made of copper or aluminum and is wound in such a way that it produces a magnetic field when direct current is applied. The magnetic field generated by the rotor interacts with the rotating magnetic field produced by the stator, causing the rotor to lock onto the stator field and rotate synchronously with it. This synchronous operation means that the rotor speed is directly proportional to the frequency of the alternating current supply and does not vary with load changes.

[0014] In operation, the EESM can function either as a motor or as a generator. As a motor, it converts electrical energy into mechanical energy by maintaining a constant speed under varying loads. When operated as a generator, it converts mechanical energy into electrical energy by maintaining a constant output frequency.

[0015] One aspect of EESMs is their ability to control the power factor by adjusting the field excitation. By varying the amount of direct current supplied to the rotor, the machine can be operated with a leading power factor, a lagging power factor, or a power factor of one, depending on the load requirements.

[0016] With reference to Fig. At 2A, the vehicle circuit 52 forms an interface with an AC power supply 54. The AC input 54 is filtered by a combination of inductors 56 and 58. These inductors 56 and 58 help to smooth the AC waveform and reduce high-frequency noise. The AC signal is then rectified using a bridge rectifier formed by diodes 60, 62, 64, and 66. This rectification process converts the AC input into a pulsating DC signal.

[0017] After rectification, the pulsating direct current is further smoothed by inductor 58 and diode 68, forming a boost converter stage that regulates the voltage level. Switch 70, controlled by an external circuit, modulates the current through inductor 58, thereby increasing the output voltage to the desired level.

[0018] The smoothed and regulated DC voltage is then fed to relay 72. Relay 72 controls the connection between the DC power source and the next stage of the circuit. When relay 72 is in position 1, the DC voltage is connected to capacitor 74, which acts as a filter capacitor and smooths out any remaining ripple in the DC signal.

[0019] The circuit is then connected to an arrangement of switches 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, which form an inverter stage. This inverter stage is responsible for converting the DC voltage back into AC current, which can be used in the EESM 96.

[0020] Capacitors 98 and 100 are connected across the traction battery 102 and serve as energy storage elements to stabilize the voltage and provide a stable power supply to the inverter stage. The traction battery 102 acts as the main power source for this circuit, supplying energy to the inverter and subsequently to the EESM 96.

[0021] In position 1, relay 104 connects the traction battery 102 to the inverter stage, enabling the system to function. The star point 106 is connected between a common node of the series-connected capacitors 98 and 100 and relay 108, providing a means of isolating the EESM 96 from the rest of the circuit.

[0022] The inverter stage outputs three-phase AC power to the EESM 96, which includes stator windings 110, 112, 114 and rotor winding 116. Stator windings 110, 112, and 114 are each connected to a star point 118. Rotor winding 116 is connected to the H-bridge power module.

[0023] The controller 120 communicates with and controls the components of the vehicle 52 and implements the techniques described in this document. It can use automotive communication protocols such as CAN (Controller Area Network), LIN (Local Interconnect Network), and / or FlexRay to establish communication channels. These protocols allow the controller 120 to send and receive data packets containing operating commands and status information. For example, the controller 120 can send PWM signals to the inverter to modulate the power supplied to the EESM 96, thereby adjusting its speed and torque. It also monitors sensors distributed throughout the vehicle 52 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 engine drive and battery management systems. Additionally, the Controller 120 can manage the operation of other auxiliary systems, such as the heating, ventilation and air conditioning system, the regenerative braking system, etc.

[0024] This system thus employs a three-phase EESM, a power factor correction (PFC) circuit, a traction inverter, an H-bridge power module, and three contactors to implement both in-vehicle electric drive and AC charging functionalities. The three-phase inverter, which includes switches 76-86 and capacitors 98 and 100, transfers power between the EESM stator windings 110, 112, and 114 and the traction battery 102 during both the vehicle's driving mode and the in-vehicle AC charging mode. The series capacitors 98 and 100 have the neutral point 106 between them. The neutral point 118 of the stator windings 110, 112, and 114 is connected to the neutral point 106 via contactor 108. The rotor winding 116 is connected to the H-bridge power module, which includes the switches 88-94 and the capacitor 74.The three-way contactors 72 and 104 establish connections between the PFC circuit, which includes the inductors 56 and 58, the diodes 60-68, and the switch 70, the H-bridge power module, and the three-phase inverter. The EESM 96 performs two functions: it acts as a normal motor while the vehicle is in motion and as an isolation transformer during in-vehicle AC charging.

[0025] With reference to Fig. 2B and while vehicle 52 is in motion, contactors 72 and 104 are in position 2 to connect the H-bridge power module and the traction battery 102, and the PFC circuit is disconnected from the H-bridge power module. Contactor 108 is open. The traction battery 102 provides power to drive the EESM 96 and vehicle 52 via the traction inverter. The rotor magnetic field is controlled by the H-bridge power module.

[0026] With reference to Fig. During operation 2C and the vehicle's internal AC charging mode, contactors 72 and 104 are in position 1 to connect the H-bridge power module and the PFC circuit, and the H-bridge power module is disconnected from the traction battery 102. Contactor 188 is closed. Power from the AC mains 54 flows through the PFC circuit, the H-bridge power module, the rotor winding 114, the air gap of the EESM 96, the windings 110, 112, and 114, and the three-phase inverter to charge the traction battery 102. In this operating mode, the EESM 96 acts as a transformer to achieve galvanic isolation.

[0027] With reference to Fig. Section 3 includes the control strategy for the vehicle's internal AC charging mode, the PFC control, the H-bridge power module control, and the three-phase inverter control. The control block diagram represents a feedback control system designed to regulate the voltage V.74 The system uses proportional-integral (PI) control and pulse-width modulation (PWM) to regulate the voltage to a defined reference level. The system maintains the voltage V. 74 at a desired reference value, V 74-ref , which in this example is set to 400 volts. The actual voltage V 74 The voltage is measured and compared to this reference value to generate an error signal. This error, representing the difference between the desired and the actual voltage, is processed by the first PI controller. The PI controller adjusts its output based on both the magnitude of the current error and the accumulation of past errors, producing a control signal that regulates the correction required to achieve the desired voltage. 74 to bring it closer to the reference value.

[0028] The output from this first PI controller is then multiplied by an input voltage Vi. This multiplication step can represent modulation or a gain adjustment based on Vi, and the resulting signal is fed into the next stage of the control system. Simultaneously, the current Li, representing the inductor current, is measured and compared to the signal produced by the previous stage. The difference between these signals is calculated to generate a current error, which is then processed by a second PI controller. The role of this second PI controller is to ensure that the current Li follows the desired path, as specified by the output from the first PI controller.

[0029] The final stage of the control process involves comparing the output of the second PI controller with a high-frequency carrier signal fsw. This comparison takes place within a comparator, producing a PWM signal 70. This PWM signal is used to control switch 70. The switching frequency is typically set to match the operating frequency of the converter. The output signal 70 is the final control signal that drives the power electronics switches.

[0030] With reference to Fig. 4. The H-bridge power module generates a high-frequency voltage in a square waveform with a duty cycle of x% by controlling switches 88-94. The figure shows an example of a voltage waveform with a duty cycle of 50% and 30 kHz.

[0031] The three-phase inverter can operate in a diode rectifier mode by switching off switches 76-86. If switches 76-86 are silicon carbide metal oxide semiconductor field-effect transistors, they can be controlled to use their reverse conduction to perform the rectifying function. The in Fig. The waveform shown in Figure 4 can be used to generate control signals for switches 76-86. The AC charging power can be controlled by V 74 and the duty cycle voltage waveform is controlled.

[0032] The Fig. Figures 7A-7C show the simulation results for charging a traction battery using the proposed in-vehicle AC charger. In the simulation, the AC network has a voltage of 120 V rms and a frequency of 60 Hz. 74=600V. The charging current of the traction battery is 12 A (6.9 kW), and the mains current is 60 A rms. Furthermore, the power factor is 1.0, and the total harmonic distortion of the mains current is 3.3%. The EESM transfers power from the mains to the traction battery and simultaneously provides galvanic isolation between the traction battery and the mains.

[0033] The algorithms, methods, or processes disclosed in this document may be supplied to or implemented by a computer, controller, or processing device, which may include any dedicated electronic control unit or programmable electronic control unit. Furthermore, 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 storage devices, and information modifiably stored on writable storage media such as compact discs, random-access storage devices, or other magnetic and optical media. The algorithms, methods, or processes may also be implemented in software-executable objects.Alternatively, the algorithms, methods or processes can be implemented wholly or partially using suitable hardware components, such as application-specific integrated circuits, field-programmable gate arrays, state machines or other hardware components or devices, or a combination of firmware, hardware and software components.

[0034] Although exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms encompassed by the claims. Furthermore, the terms used in the description are descriptive rather than limiting, and it is understood that various modifications may be made without altering the spirit and scope of these disclosed subject matter. For example, "control" and "controls" may be used interchangeably herein, since the functionality of one may be distributed across several, all of which can communicate using standard techniques.

[0035] As previously described, the features of different embodiments can be combined to form further embodiments of the invention, which may not be expressly described or illustrated. Although various embodiments may have been described in such a way that they offer advantages or are preferred over other embodiments or implementations according to the prior art with respect to one or more desired properties, the person skilled in the art understands that compromises may be made with respect to one or more features or properties in order to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, among others, strength, durability, marketability, appearance, installation, size, maintainability, weight, manufacturability, ease of assembly, etc.Therefore, embodiments that are described as less desirable than other embodiments or implementations according to the prior art with respect to one or more properties are not outside the scope of protection of the disclosure and may be desirable for specific applications.

[0036] According to the present invention, a vehicle is provided which has the following: a power system comprising a power factor correction circuit, an H-bridge power module, a separately excited synchronous machine, a traction inverter and a traction battery, which are configured such that during a driving mode the H-bridge power module and the traction inverter are each connected between the traction battery and the separately excited synchronous machine, and during a charging mode the H-bridge power module and the separately excited synchronous machine are connected between the power factor correction circuit and the traction inverter.

[0037] According to one embodiment, the power system is further configured such that during driving mode, power flows from the traction battery through each of the H-bridge power modules and the traction inverter to the separately excited synchronous machine.

[0038] According to one embodiment, the power system is further configured such that during the charging mode, power flows successively from an AC power source through the power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter and to the traction battery.

[0039] According to one embodiment, the traction inverter includes phase branches and the separately excited synchronous machine includes stator windings connected to the phase branches.

[0040] According to one embodiment, the stator windings are connected to a star point.

[0041] According to one embodiment, the traction inverter includes a pair of capacitors connected in series, and the power system is further configured such that the star point is connected between the capacitors during the charging mode.

[0042] According to one embodiment, the separately excited synchronous machine includes a rotor winding connected to the H-bridge power module and having an air gap from the stator windings.

[0043] According to one embodiment, the power system further includes a pair of three-way switches that have different connection states during driving mode and charging mode.

[0044] According to the present invention, a method comprises: changing the connection states of contactors such that during a driving mode, power flows from a traction battery through each of an H-bridge power module and a traction inverter to a separately excited synchronous machine that drives a vehicle, and during a charging mode, power flows from an AC source successively through a power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter and to the traction battery.

[0045] In one aspect of the invention, the method involves changing the connection states of the contactors so that during the charging mode a star point of the separately excited synchronous machine is connected between a pair of capacitors of the traction inverter.

[0046] According to the present invention, a power system for motor vehicles is provided comprising: a power factor correction circuit, an H-bridge power module, a separately excited synchronous machine, a traction inverter, and a traction battery, which are jointly configured such that during a driving mode, power flows from the traction battery through the H-bridge power module and the traction inverter to the separately excited synchronous machine, and during a charging mode, power flows sequentially from an AC source through the power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter, and to the traction battery.

[0047] According to one embodiment, the power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter and the traction battery are further configured together such that during driving mode the H-bridge power module and the traction inverter are each connected between the traction battery and the separately excited synchronous machine.

[0048] According to one embodiment, the power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter and the traction battery are further configured together such that during the charging mode the H-bridge power module and the separately excited synchronous machine are connected between the power factor correction circuit and the traction inverter.

[0049] According to one embodiment, the traction inverter includes phase branches and the separately excited synchronous machine includes stator windings connected to the phase branches.

[0050] According to one embodiment, the stator windings are connected to a star point.

[0051] According to one embodiment, the traction inverter includes a pair of capacitors connected in series, and wherein the power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter, and the traction battery are further configured together such that during the charging mode, the star point is connected between the capacitors.

[0052] According to one embodiment, the separately excited synchronous machine includes a rotor winding connected to the H-bridge power module and having an air gap from the stator windings.

Claims

[1] vehicle, comprising the following: a power system comprising a power factor correction circuit, an H-bridge power module, a separately excited synchronous machine, a traction inverter and a traction battery, configured such that during a driving mode the H-bridge power module and the traction inverter are each connected between the traction battery and the separately excited synchronous machine, and during a charging mode the H-bridge power module and the separately excited synchronous machine are connected between the power factor correction circuit and the traction inverter. [2] Vehicle according to claim 1, wherein the power system is further configured such that during driving mode power flows from the traction battery through each of the H-bridge power module and the traction inverter to the separately excited synchronous machine. [3] Vehicle according to claim 1, wherein the power system is further configured such that during the charging mode, power flows successively from an AC source through the power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter and to the traction battery. [4] Vehicle according to claim 1, wherein the traction inverter includes phase branches and wherein the separately excited synchronous machine includes stator windings connected to the phase branches. [5] Vehicle according to claim 4, wherein the stator windings are connected to a star point. [6] Vehicle according to claim 5, wherein the traction inverter includes a pair of capacitors connected in series and wherein the power system is further configured such that during the charging mode the star point is connected between the capacitors. [7] Vehicle according to claim 4, wherein the separately excited synchronous machine includes a rotor winding connected to the H-bridge power module and having an air gap from the stator windings. [8] Vehicle according to claim 1, wherein the power system further includes a pair of three-way switches which have different connection states during the driving mode and the charging mode. [9] Procedures, comprising the following: Changing the connection states of contactors so that during a driving mode, power from a traction battery flows through each of an H-bridge power module and a traction inverter to a separately excited synchronous machine that propels a vehicle, and during a charging mode, power from an AC source flows sequentially through a power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter and to the traction battery. [10] Method according to claim 9, further comprising changing connection states of the contactors such that during the charging mode a star point of the separately excited synchronous machine is connected between a pair of capacitors of the traction inverter. [11] Power system for motor vehicles, comprising the following: a power factor correction circuit, an H-bridge power module, a separately excited synchronous machine, a traction inverter and a traction battery, which are jointly configured such that during a driving mode, power flows from the traction battery through the H-bridge power module and the traction inverter to the separately excited synchronous machine, and during a charging mode, power flows from an AC source sequentially through the power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter and to the traction battery. [12] Power system for motor vehicles according to claim 11, wherein the power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter and the traction battery are further configured together such that during driving mode the H-bridge power module and the traction inverter are each connected between the traction battery and the separately excited synchronous machine. [13] Power system for motor vehicles according to claim 11, wherein the power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter and the traction battery are further configured together such that during the charging mode the H-bridge power module and the separately excited synchronous machine are connected between the power factor correction circuit and the traction inverter. [14] Power system for motor vehicles according to claim 11, wherein the traction inverter includes phase branches and wherein the separately excited synchronous machine includes stator windings which are connected to the phase branches. [15] Power system for motor vehicles according to claim 14, wherein the stator windings are connected to a star point, wherein the traction inverter includes a pair of capacitors connected in series, and wherein the power factor correction circuit, the H-bridge power module, the separately excited synchronous machine, the traction inverter and the traction battery are further configured together such that during the charging mode the star point is connected between the capacitors.

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