Isolated dual-bus hybrid vehicle powertrain

Abstract

A powertrain for a vehicle includes a Y-wound generator, a Y-wound motor, a generator inverter, a motor inverter, and a traction battery. The Y-wound generator and the Y-wound motor are coupled via respective neutral terminals. The generator inverter is coupled between the Y-wound generator and a generator bus, and the motor inverter is coupled between the Y-wound motor and a motor bus. The traction battery has a first terminal coupled to each neutral terminal and a second terminal coupled to bus terminals of the generator bus and the motor bus.

Description

Technical Field

[0001] The present application generally relates to a hybrid vehicle powertrain having dual electric machines, each with an isolated DC / AC converter and each operating at an independent voltage. Background Art

[0002] Electrified vehicles (EVs), including hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs), rely on traction batteries to provide power to the traction motors used for propulsion and to the power inverters between them to convert direct current (DC) power to alternating current (AC) power. Typical AC traction motors are three-phase motors that can be powered by three sinusoidal signals, each driven 120 degrees apart. Traction batteries are configured to operate and provide current within a specific voltage range. Traction batteries are alternatively referred to as high-voltage batteries. However, by operating within a different voltage range, typically at a voltage greater than the traction battery terminal voltage, improved performance of the motor can be achieved. Similarly, the current requirements for driving the vehicle's motors are often referred to as high current.

[0003] Furthermore, many electrified vehicles include a DC-DC converter (also known as a variable voltage converter (VVC)) to convert the voltage of the traction battery to the operating voltage level of the electric machines. The electric machines, which may include traction motors and generators, can require high voltages and currents. Due to these voltage and current requirements, the battery module and the power electronics module are typically in continuous communication. Summary of the Invention

[0004] A powertrain system for a vehicle includes a Y-wound generator, a Y-wound motor, a generator inverter, a motor inverter, and a traction battery. The Y-wound generator and the Y-wound motor are coupled via respective neutral terminals. The generator inverter is coupled between the Y-wound generator and a generator bus, and the motor inverter is coupled between the Y-wound motor and a motor bus. The traction battery has a first terminal coupled to each neutral terminal and a second terminal coupled to bus terminals of the generator bus and the motor bus.

[0005] A powertrain control method includes a propulsion mode in which current is directed from a battery to a first neutral terminal of a first electric machine and a second neutral terminal of a second electric machine; a first set of switches of a first inverter is modulated to output a first bus voltage; and a second set of switches of a second inverter is modulated to output a second bus voltage different from the first bus voltage.

[0006] A vehicle powertrain system includes a generator, a motor, and a traction battery. The generator has a first neutral terminal. The motor has a second neutral terminal coupled to the first neutral terminal. The traction battery has a first terminal coupled to the first neutral terminal and the second neutral terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a diagram of an electrified vehicle having a dual-motor powertrain powered by a traction battery via a neutral terminal of each motor.

[0008] Figure 2 is a diagram illustrating a hybrid vehicle including a typical power train and energy storage components including a variable voltage converter.

[0009] Figure 3 It is a schematic diagram of the power inverter of the power electronics module.

[0010] Figure 4 is a diagram of a hybrid vehicle powertrain including a traction battery, a variable voltage converter, dual inverters, and dual electric motors.

[0011] Figure 5 is a diagram of a dual-motor powertrain powered by a traction battery via the neutral terminal of each motor.

[0012] Figure 6 is a graphical representation of a modulation method for controlling a dual-motor powertrain powered by a traction battery via the neutral terminal of each motor.

[0013] Figure 7A and Figure 7B is a graphical representation of the system electrical characteristics of an isolated dual-bus hybrid vehicle powertrain versus time. DETAILED DESCRIPTION

[0014] Embodiments of the present disclosure are described herein. However, it will be understood that the disclosed embodiments are merely examples. And other embodiments may take various forms and alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural details and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to adopt the invention in different ways. As will be understood by those of ordinary skill in the art, the various features shown and described with reference to any one of the accompanying drawings may be combined with features shown in one or more other drawings to produce embodiments that are not explicitly shown or described. The combinations of features shown provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for specific applications or implementations.

[0015] A typical drive system for an EV / HEV may include a direct current (DC) power source (i.e., a high-voltage battery), a variable voltage converter (VVC), an inverter, and a motor. The VVC may be a bidirectional boost converter configured to boost the battery voltage to the operating voltage of the motor / generator and inverter. Practical aspects of a typical drive system include the need for multiple power devices connected in parallel to output higher current / higher power when increased power is required. Connecting multiple power devices in parallel may create current sharing issues between the parallel-connected power devices. As a result of this current sharing issue, system efficiency may be compromised. Furthermore, in a typical drive system, the output voltage range of the boost converter may be limited when efficiency decreases based on the step-up ratio (i.e., the ratio of the high-voltage DC voltage (Vdc) to the input battery (Vb) (e.g., Vdc / Vb>2)). To improve electric drivetrain (e-drive) performance, a VVC with a wide output voltage range is desirable.

[0016] Figure 1 A hybrid electric vehicle is depicted showing internal electric powertrain components configured to cause current to flow through the windings of the motor 4 by operating the motor inverter 8, the DC bus 12, and the high-voltage traction battery 2, and to cause current to flow through the windings of the generator 6 by operating the generator inverter 10, the DC bus 14, and the high-voltage traction battery 2.

[0017] Figure 2An electrified vehicle 112 is depicted, which may be referred to as a plug-in hybrid electric vehicle (PHEV). The plug-in hybrid electric vehicle 112 may include one or more electric motors 114 mechanically coupled to a hybrid transmission 116. The electric motors 114 may be capable of operating as either a motor or a generator. In addition, the hybrid transmission 116 is mechanically coupled to an engine 118. The hybrid transmission 116 is also mechanically coupled to a drive shaft 120, which is mechanically coupled to wheels 122. The electric motors 114 can provide propulsion and deceleration capabilities when the engine 118 is turned on or off. The electric motors 114 can also act as generators and can provide fuel economy benefits by recovering energy that would normally be lost as heat in the friction braking system. The electric motors 114 can also reduce vehicle emissions by allowing the engine 118 to operate at a more efficient speed and allowing the hybrid electric vehicle 112 to operate in electric mode when the engine 118 is turned off under certain conditions. The electrified vehicle 112 may also be a battery electric vehicle (BEV). In a BEV configuration, the engine 118 may not be present. In other configurations, the electrified vehicle 112 may be a full hybrid electric vehicle (FHEV) without plug-in capability.

[0018] The traction battery or battery pack 124 stores energy that can be used by the motor 114. The vehicle battery pack 124 can provide a high-voltage direct current (DC) output. The traction battery 124 can be electrically coupled to one or more power electronics modules 126. One or more contactors 142 can isolate the traction battery 124 from other components when open and connect the traction battery 124 to other components when closed. The power electronics module 126 is also electrically coupled to the motor 114 and provides the ability to transfer energy bidirectionally between the traction battery 124 and the motor 114. For example, the traction battery 124 can provide a DC voltage, while the motor 114 can function with three-phase alternating current (AC). The power electronics module 126 can convert the DC voltage into a three-phase AC current to operate the motor 114. In regenerative mode, the power electronics module 126 can convert the three-phase AC current from the motor 114, which acts as a generator, into a DC voltage compatible with the traction battery 124.

[0019] The vehicle 112 may include a variable voltage converter (VVC) 152 electrically coupled between the traction battery 124 and the power electronics module 126. The VVC 152 may be a DC / DC boost converter configured to increase or boost the voltage provided by the traction battery 124. By increasing the voltage, current requirements may be reduced, resulting in a reduced wiring size for the power electronics module 126 and the electric motor 114. Additionally, the electric motor 114 may operate with better efficiency and lower losses.

[0020] In addition to providing energy for propulsion, the traction battery 124 can also provide energy for other vehicle electrical systems. The vehicle 112 may include a DC / DC converter module 128 that converts the high-voltage DC output of the traction battery 124 into a low-voltage DC supply compatible with low-voltage vehicle loads. The output of the DC / DC converter module 128 can be electrically coupled to an auxiliary battery 130 (e.g., a 12V battery) to charge the auxiliary battery 130. Low-voltage systems can be electrically coupled to the auxiliary battery 130. One or more electrical loads 146 can be coupled to the high-voltage bus. The electrical loads 146 can have associated controllers that operate and control the electrical loads 146 as appropriate. Examples of electrical loads 146 may include fans, electric heating elements, and / or air conditioning compressors.

[0021] The electrified vehicle 112 can be configured to recharge the traction battery 124 from an external power source 136. The external power source 136 can be a connection to an electrical outlet. The external power source 136 can be electrically coupled to a charger or electric vehicle supply equipment (EVSE) 138. The external power source 136 can be a power distribution network or grid provided by an electric utility company. The EVSE 138 can provide circuitry and controls to regulate and manage the transfer of energy between the power source 136 and the vehicle 112. The external power source 136 can provide DC power or AC power to the EVSE 138. The EVSE 138 can have a charging connector 140 for plugging into a charging port 134 of the vehicle 112. The charging port 134 can be any type of port configured to transfer power from the EVSE 138 to the vehicle 112. The charging port 134 can be electrically coupled to a charger or an onboard power conversion module 132. The power conversion module 132 can condition the power supplied from the EVSE 138 to provide appropriate voltage and current levels to the traction battery 124. The power conversion module 132 can interface with the EVSE 138 to coordinate the delivery of power to the vehicle 112. The EVSE connector 140 can have pins that mate with corresponding recesses of the charging port 134. Alternatively, the various components described as being electrically coupled or connected can use wireless inductive coupling to transfer power.

[0022] One or more wheel brakes 144 may be provided to decelerate vehicle 112 and prevent vehicle 112 from moving. Wheel brakes 144 may be hydraulically actuated, electrically actuated, or some combination thereof. Wheel brakes 144 may be part of a braking system 150. Braking system 150 may include other components to operate wheel brakes 144. For simplicity, the diagram illustrates a single connection between braking system 150 and one of wheel brakes 144. This implies connections between braking system 150 and the other wheel brakes 144. Braking system 150 may include a controller to monitor and coordinate braking system 150. Braking system 150 may monitor braking components and control wheel brakes 144 to decelerate the vehicle. Braking system 150 may respond to driver commands and may also operate autonomously to implement features such as stability control. The controller of braking system 150 may implement a method for applying a requested braking force when requested by another controller or sub-function.

[0023] The electronic modules in the vehicle 112 can communicate via one or more vehicle networks. The vehicle network can include multiple channels for communication. One channel of the vehicle network can be a serial bus, such as a controller area network (CAN). One channel of the vehicle network can include an Ethernet network defined by the Institute of Electrical and Electronics Engineers (IEEE) 802 series of standards. Additional channels of the vehicle network can include discrete connections between modules and can include power signals from the auxiliary battery 130. Different signals can be passed on different channels of the vehicle network. For example, a video signal can be passed over a high-speed channel (e.g., Ethernet), while control signals can be passed over CAN or discrete signals. The vehicle network can include any hardware and software components that facilitate the transfer of signals and data between modules. The vehicle network is not described in detail in the original text. Figure 2 1 , but this may imply that the vehicle network may be connected to any electronic module present in the vehicle 112. A vehicle system controller (VSC) 148 may be present to coordinate the operation of the various components.

[0024] Typically, the VVC 152 is configured as a boost converter. The VVC 152 may include input terminals that may be coupled to terminals of the traction battery 124 via contactors 142. The VVC 152 may include output terminals coupled to terminals of the power electronics module 126. The VVC 152 may be operated to cause a voltage at the output terminals to be greater than a voltage at the input terminals. The vehicle 112 may include a VVC controller that monitors and controls electrical parameters (e.g., voltage and current) at various locations within the VVC 152. In some configurations, the VVC controller may be included as part of the VVC 152. The VVC controller may determine an output reference voltage. The VVC controller can be based on electrical parameters and reference voltage The control signal is determined to be sufficient to cause the VVC 152 to achieve the desired output voltage. In some configurations, the control signal may be implemented as a pulse width modulated (PWM) signal, wherein the duty cycle of the PWM signal varies. The control signal may operate at a predetermined switching frequency. The VVC controller may use the control signal to command the VVC 152 to provide the desired output voltage. The specific control signal used when operating the VVC 152 may be directly related to the amount of voltage boost provided by the VVC 152.

[0025] refer to Figure 2 The VVC 152 can increase or "boost" the voltage potential of the power provided by the traction battery 124. The traction battery 124 can provide high voltage (HV) DC power. In some configurations, the traction battery 124 can provide a voltage between 150 volts and 400 volts. The contactor 142 can be electrically coupled in series between the traction battery 124 and the VVC 152. When the contactor 142 is closed, HV DC power can be transferred from the traction battery 124 to the VVC 152. An input capacitor can be electrically coupled in parallel to the traction battery 124. The input capacitor can reduce any voltage and current ripple. The VVC 152 can receive the HV DC power and increase or "boost" the voltage potential of the input voltage according to the duty cycle. Typically, an output capacitor is electrically coupled between the output terminals of the VVC 152 and the input of the power electronics module 126 to stabilize the bus voltage and reduce voltage and current ripple at the output of the VVC 152.

[0026] refer to Figure 3 , a system 300 for controlling a power electronics module (PEM) 126 is provided. Figure 3 The PEM 126 is shown as including a plurality of switches 302 (e.g., IGBTs) configured to collectively operate as an inverter having a first phase bridge 316, a second phase bridge 318, and a third phase bridge 320. Although the inverter is shown as a three-phase converter, the inverter may include additional phase bridges. For example, the inverter may be a four-phase converter, a five-phase converter, a six-phase converter, etc. Additionally, the PEM 126 may include multiple converters, wherein each inverter in the PEM 126 includes three or more phase bridges. For example, the system 300 may control two or more inverters in the PEM 126. The PEM 126 may also include a DC-DC converter having high-power switches (e.g., IGBTs) to convert the power electronics module input voltage to the power electronics module output voltage via step-up, step-down, or a combination thereof.

[0027] like Figure 3As shown, the inverter can be a DC-AC converter. In operation, the DC-AC converter receives DC power from the DC power link 306 via the DC bus 304 and converts the DC power into AC power. The AC power is transmitted via phase currents ia, ib, and ic to drive an AC machine (also referred to as a motor 114), such as Figure 3 3. In this example, the DC power link 306 may include a DC battery to provide DC power to the DC bus 304. In another example, the inverter may operate as an AC-DC converter that converts AC power from the AC machine 114 (e.g., a generator) into DC power, and the DC bus 304 may provide the DC power to the DC power link 306. In addition, the system 300 may control the PEM 126 in other power electronics topologies.

[0028] Continue to refer Figure 3 Each of the phase bridges 316, 318, 320 in the inverter includes a power switch 302, which can be implemented by various types of controllable switches. In one embodiment, each power switch 302 can include a diode and a transistor (eg, an IGBT). Figure 3 The diode is marked as D a1 、D a2 、D b1 、D b2 、D c1 and D c2 ,and Figure 3 The IGBTs are marked as S a1 、S a2 、S b1 、S b2 、S c1 and S c2 . Power switch S a1 、S a2 、D a1 and D a2 It is the phase bridge A part of the three-phase converter. Figure 3 In FIG, it is marked as the first phase bridge A 316. Similarly, the power switch S b1 、S b2 、D b1 and D b2 is part of phase bridge B 318, and power switch S c1 、S c2 、D c1 and D c2 is part of the phase bridge C 320 of the three-phase converter. The inverter may include any number of power switches 302 or circuit elements, depending on the specific configuration of the inverter. xx ) and IGBT(Sxx ) are connected in parallel, however, since the polarity is the reverse of normal operation, this configuration is often referred to as an anti-parallel connection. The diodes in this anti-parallel configuration are also known as freewheeling diodes.

[0029] like Figure 3 As shown, the current sensor CS a , CS b and CS c is provided to sense the current in the respective phase bridge 316 , 318 , 320 . Figure 3 The current sensor CS is shown separated from the PEM 126. a , CS b and CS c However, the current sensor CS a , CS b and CS c May be integrated as part of the PEM 126, depending on its configuration. Figure 3 Current sensor CS a , CS b and CS c With phase bridges A, B and C (i.e., Figure 3 The phase bridges 316, 318, 320) are arranged in series and provide corresponding feedback signals i for the system 300. as 、i bs and i cs (also Figure 3 Feedback signal i as 、i bs and i cs The current signal may be a raw current signal processed by the logic device (LD) 310, or may be embedded or encoded with data or information about the current through the corresponding phase bridge 316, 318, 320. Furthermore, the power switch 302 (e.g., IGBT) may include current sensing capability. The current sensing capability may include being configured with a current mirror output that can provide a current mirror output representing the current of the current. as 、i bs and i cs The data / signal may indicate the direction of current, the magnitude of current, or both the direction and magnitude of current through the corresponding phase bridges A, B, and C.

[0030] Reference again Figure 3, the system 300 includes a logic device (LD) or controller 310. The controller or LD 310 may be implemented by various types or combinations of electronic devices and / or microprocessor-based computers or controllers. To implement the method of controlling the PEM 126, the controller 310 may execute a computer program or algorithm embedded or encoded with the method and stored in volatile and / or persistent memory 312. Alternatively, the logic may be encoded in discrete logic, a microprocessor, a microcontroller, or logic or gate arrays stored on one or more integrated circuit chips. Figure 3 As shown in the embodiment of FIG, the controller 310 receives and processes the feedback signal i as 、i bs and i cs To control the phase current i a 、i b and i c , so that the phase current i a 、i b and i c Flow through the phase bridges 316, 318, 320 and into the corresponding windings of the motor 114 according to various current or voltage patterns. For example, the current pattern may include the phase current i flowing into and out of the DC bus 304 or the DC bus capacitor 308. a 、i b and i c pattern. Figure 3 The DC bus capacitor 308 is shown separate from the PEM 126. However, the DC bus capacitor 308 may be integrated as part of the PEM 126.

[0031] like Figure 3 As shown, a storage medium 312 (hereinafter referred to as "memory"), such as a computer readable memory, can store a computer program or algorithm embedded or encoded with the method. In addition, the memory 312 can store data or information about various operating conditions or components in the PEM 126. For example, the memory 312 can store data or information about the current through the corresponding phase bridges 316, 318, and 320. The memory 312 can be part of the controller 310, such as Figure 3 However, memory 312 may be located in any suitable location accessible to controller 310 .

[0032] like Figure 3As shown, the controller 310 transmits at least one control signal 236 to the power converter system 126. The power converter system 126 receives the control signal 236 to control the switching configuration of the inverter and, therefore, control the current through the corresponding phase bridges 316, 318, and 320. The switching configuration is a set of switching states of the power switches 302 in the inverter. Generally, the switching configuration of the inverter determines how the inverter converts power between the DC power link 306 and the motor 114.

[0033] To control the switching configuration of the inverter, the inverter changes the switching state of each power switch 302 in the inverter to an on state or an off state based on the control signal 236. In the illustrated embodiment, to switch the power switches 302 to the on or off state, the controller / LD 310 provides a gate voltage (Vg) to each power switch 302 and thus drives the switching state of each power switch 302. The gate voltage Vg a1 、Vg a2 、Vg b1 、Vg b2 、Vg c1 and Vg c2 ( Figure 3 ) controls the switching state and characteristics of the corresponding power switch 302. Figure 3 3. The inverter is shown as a voltage-driven device, but the inverter can be a current-driven device or controlled by other strategies that switch the power switch 302 between the on state and the off state. The controller 310 can change the gate drive of each IGBT based on the rotational speed of the motor 114, the mirror current, or the temperature of the IGBT switch. The gate drive change can be selected from a plurality of gate drive currents, where the change in gate drive current is proportional to the change in IGBT switching speed.

[0034] Also like Figure 3 As shown, each phase bridge 316, 318 and 320 includes two switches 302. However, only one switch in each of the bridges 316, 318, 320 can be in the on state without short-circuiting the DC power link 306. Therefore, in each phase bridge, the switching state of the lower switch is typically opposite to the switching state of the corresponding upper switch. The upper switches are typically referred to as high-side switches (i.e., 302A, 302B, 302C), and the lower switches are typically referred to as low-side switches (i.e., 302D, 302E, 302F). Therefore, the high state of the phase bridge refers to the upper switch in the bridge being in the on state, while the lower switch is in the off state. Similarly, the low state of the phase bridge refers to the upper switch in the bridge being in the off state, while the lower switch is in the on state. IGBTs with current mirror capability can be used in all IGBTs, a subset of IGBTs (e.g., S a1 、S b1 、Sc1 ) or a single IGBT.

[0035] exist Figure 3 During the active state of the three-phase converter example shown in , two situations can occur: (1) two phase bridges are in a high state and the third phase bridge is in a low state, or (2) one phase bridge is in a high state and the other two phase bridges are in a low state. Thus, one phase bridge in the three-phase converter, which can be defined as a "reference" phase for a particular active state of the inverter, is in the opposite state to the other two phase bridges, or "non-reference" phases, which have the same state. Thus, during the active state of the inverter, the non-reference phases are either all in a high state or all in a low state.

[0036] Solid-state devices (SSDs), such as insulated-gate bipolar junction transistors (IGBTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), or bipolar junction transistors (BJTs), are widely used in various automotive and industrial applications, such as electric motor drives, power inverters, DC-DC converters, and power modules. The operation of IGBTs and MOSFETs is voltage-controlled, where the operation is based on the voltage applied to the gate of the IGBT or MOSFET, while the operation of BJTs is current-controlled, where the operation is based on the current applied to the base of the BJT. Here, the use of SSDs or high-power relays can be used to control, modify, or modulate the current between the vehicle's battery and motor.

[0037] Figure 4 4 is a diagram of a hybrid vehicle powertrain 400, which includes a traction battery 402, a DC bus capacitor 404, a variable voltage converter 406, dual inverters 408 and 410, and dual electric machines 412 and 414. A power split configuration of a hybrid electric vehicle (HEV) drive system is shown, including a traction motor 412 and traction motor inverter 408, a generator 414 and generator inverter 410, a DC bus capacitor 416, a variable voltage converter (VVC) 406, battery capacitors 404, and traction battery 402. Both the motor (M) 412 and the generator (G) 414 can operate in either a propulsion mode, converting power / energy into force, or a generation mode, converting kinetic energy into electricity / electrical energy. The motor / inverter, generator / inverter, and battery are coupled via a capacitor-based DC bus, with the battery's low voltage boosted to a high level by the VVC to enhance the performance of the traction motor drive.

[0038] like Figure 4The powertrain system (E-drive system) shown has advantages and disadvantages. First, a single DC bus is shared by the VVC 406, the motor inverter 408, and the generator inverter 410, resulting in a single DC bus voltage being applied to both the motor inverter 408 and the generator inverter 410. Using a single DC bus voltage can result in increased power losses in the motor inverter and the generator inverter.

[0039] Typically, the voltage across the stator windings in motors and generators is related to their respective rotor speeds. High rotor speeds typically correspond to high motor / generator voltages, while low rotor speeds typically correspond to low motor / generator voltages. In some embodiments, the motor and generator can operate at different rotor speeds. For example, one can operate in a high-speed mode requiring a high stator voltage, while the other can operate in a low-speed mode with a low stator voltage. Figure 4 In the E-drive system shown in FIG, if the generator operates in high-speed mode and the motor operates in low-speed mode, a high DC bus voltage and a low modulation index are required to achieve a low motor stator voltage. This may result in a high DC bus voltage, which leads to high power losses in the motor inverter. Similarly, if the motor operates in high-speed mode and the generator operates in low-speed mode, the generator inverter / VVC requires a high DC bus voltage and a low modulation index to achieve a low generator stator voltage. This may result in a high DC bus voltage, which leads to high power losses in the generator inverter.

[0040] Furthermore, the dual-motor system 400 typically requires a VVC 406 to ensure the desired DC bus voltage can be generated, regardless of the power usage of the motor drive or generator drive during propulsion or power generation. The VVC 406 has several disadvantages. For example, it is bulky and can be difficult to package in the vehicle. Furthermore, the VVC 406 includes inductors and power switches, which typically exhibit high power losses, contributing to the inefficiency of the E-drive system. During operation, the inductor can heat up, requiring cooling, which can be difficult. The combination of additional cooling in an already space-constrained system exacerbates these issues and adds additional cost and weight to the VVC 406. Furthermore, in some embodiments, the inductor's magnetic core can exhibit temperature-sensitive properties, saturating easily at high temperatures, making the VVC performance unstable under certain operating conditions.

[0041] Here, a dual-motor system is configured to operate using a Y-wound motor and a Y-wound generator with separate DC buses without a variable voltage converter and with power flowing to and from the Y-wound motor via a neutral terminal.

[0042] Figure 55 is a diagram of a dual-motor powertrain 500 that enables power to flow from a battery 502 (e.g., a traction battery) to a first electric machine 504 (motor) and a motor inverter 506, and a second electric machine 508 (generator) and a generator inverter 510. Battery 502 is coupled to the neutral terminal of each electric machine, allowing power to flow into and out of battery 502 from the neutral terminals of motor 504 and generator 508. Power passes through the inverter to the bus storage capacitors. For example, on the motor side, power moves from battery 502 to motor 504 and motor inverter 506 to motor DC bus capacitor 512, while on the generator side, power moves from battery 502 to generator 508 and generator inverter 510 to generator DC bus capacitor 514.

[0043] The separate DC bus based E-drive system 500 in the HEV allows the motor inverter and generator inverter, each with their own DC bus, to be controlled separately. The separate DC bus allows each DC bus voltage to be varied independently to meet the voltage requirements of the motors operating at different speeds and possibly in different operating modes. For example, one motor can be charging while the other can provide torque. This also allows for control losses, for example, a low DC bus voltage can be applied to provide a low motor / generator stator voltage at low speeds, thereby reducing inverter power losses. By overcoming Figure 4 Separate DC buses help reduce inverter power losses by addressing the problem of coupled DC buses as shown in FIG. For example, if motor 504 is operated at high speed and generator 508 is operated at low speed, the motor inverter and generator inverter (506 and 510) will have two DC bus voltages, with the motor DC bus at a high DC bus voltage and the generator DC bus at a low DC bus voltage to reduce power losses.

[0044] Because VVC is absent in E-drive system 500, the disadvantages associated with VVC listed above can be avoided. In E-drive system 500, the neutral points of the stator windings of generator 508 and motor 504 are coupled together to form a common neutral point. Battery 502 is coupled between the common neutral point and the DC bus negative rail. Motor inverter 506 controls the operation of motor 504 and also controls the DC bus voltage Vdc2 at motor bus capacitor 512. Similarly, generator inverter 510 controls the operation of generator 508 and also controls the DC bus voltage Vdc1 at generator bus capacitor 514. Both motor 504 and generator 508 can operate in propulsion and energy generation modes, and traction battery 502 can be in charging / discharging (or non-charging and non-discharging) modes. Here, two inverters manage three sources (motor 504, generator 508 and battery 502) (all sources have bidirectional power flow) and two DC bus voltages, namely, a DC bus voltage Vdc1 at the generator bus capacitor 514 and a DC bus voltage Vdc2 at the motor bus capacitor 512, which can be independently controlled to have different levels to meet the operating requirements of the motor 504 and the generator 508 operating at different speeds.

[0045] Figure 6 6 is a graphical representation of a modulation method 600 for controlling a dual-motor powertrain system powered by a traction battery via the neutral terminal of each motor. This modulation method shows a signal 602 with respect to time 604, where a carrier signal 606 is superimposed with each phase sinusoidal component (608, 610, and 612) having a DC offset. Figure 5 , the motor and generator inverters (eg, 506 and 510) can use the same modulation method 600. The modulation signal is Figure 6 The carrier wave in the control motor inverter / generator inverter (eg, 506 and 510) is compared to control the switching of the motor inverter / generator inverter, including the sinusoidal component m a 、m b 、m c and the DC offset component D bat Here, waveform 608 is m a +D bat , 610 is m b +D bat , and 612 is m c +D bat . m a 、m b and m c The phase component is used to control the line voltage of the motor / generator, the duty cycle D bat Controls the DC bus voltage. For the motor inverter (eg, 506), D bat =DM , m a =m U1 , m b =m V1 , m c =m W1 ; For the generator inverter (eg, 510), D bat =D G , m a =m U2 , m b =m V2 , m c =m W2 . Figure 5 The two DC bus voltages can be expressed as

[0046]

[0047]

[0048] Where V dc1 is the DC bus voltage of the generator capacitor 514, V dc2 is the DC bus voltage of the motor capacitor 512, -1 <D G <1, -1 <D M <1, and V b is the voltage of battery 502. Based on this representation, it is shown that each DC bus voltage can be controlled individually over a wide operating range. For example, during low speed operation of the motor / generator, a low DC bus voltage of the motor inverter / generator inverter can be used to reduce inverter power losses. Moreover, during high speed operation of the motor / generator, a high DC bus voltage can be implemented to provide the required motor voltage / generator voltage. Here, when the motor (e.g., 504) is operating at high speed, by adjusting the DC bus voltage, the motor inverter / generator inverter can be used to reduce inverter power losses. M To control the motor inverter (eg, 506) to have a high DC bus voltage, while the generator (eg, 508) operates at a low speed by adjusting the D G The DC bus voltage of the generator inverter (eg, 510) is controlled to have a low level. This allows the power loss of the motor inverter and the generator inverter to be reduced to a greater extent.

[0049] Here, the two carrier waveforms for the motor inverter and the generator inverter have a phase shift of substantially 180° to achieve interleaved control to significantly reduce the battery current ripple.

[0050] Here, the sum of the motor and generator power is balanced by the battery power, such that pM+pG+pB=0. Generally, there are three operating modes. The first is when the traction battery is not charging or discharging due to the balance of motor and generator power (i.e., pM+pG=0, pB=0). The next is when the traction battery is charging and the sum of the motor and generator power is less than 0 (i.e., the total generated power is greater than the total propulsion power, pM+pG<0, pB>0). The third is when the traction battery is discharging and the sum of the motor and generator power is greater than 0 (i.e., the total generated power is less than the total propulsion power, pM+pG>0, pB<0).

[0051] Figure 5 The system provides two current components for each phase stator winding of the motor / generator. The first current component is a sinusoidal current that produces motor / generator torque, and the second current component is a DC current component that is one-third of the total DC current flowing through the neutral point of the motor / generator winding. This DC current component does not produce torque on the motor / generator rotor and therefore does not affect the operation of the motor / generator.

[0052] Three example modes of operation are discussed to describe Figure 5 . In a first operating mode, generator 508 generates power in high-speed mode, while motor 504 consumes power in low-speed mode, and battery 502 is charged. In a second operating mode, generator 508 generates power in low-speed mode, while motor 504 consumes power in high-speed mode, and battery 502 is discharged. Furthermore, in a third operating mode, generator 508 generates power in high-speed mode, while motor 504 generates power in low-speed mode, and battery 502 is charged.

[0053] Figure 7A and Figure 7B Is a graphical representation of the electrical characteristics of a system with respect to time. Figure 7A Generator phase current 702, generator phase voltage 704, motor phase current 706, and motor phase voltage 708 are shown relative to time 716. Likewise, Figure 7B The DC bus voltage 710, battery current 712, and power 714 are shown relative to time 716. Return to Reference Figure 7AThe generator phase current 702 includes a generator w current 718, a generator u current 720, and a generator v current 722 relative to time 716. There is also a generator phase voltage 704, which includes a generator w voltage 724, a generator u voltage 726, and a generator v voltage 728 relative to time 716. Furthermore, the motor phase current 706 includes a motor v current 734, a motor u current 732, and a motor w current 730 relative to time 716, and the motor phase voltage 708 includes a motor v voltage 740, a motor u voltage 738, and a motor w voltage 736 relative to time 716.

[0054] Here, the system (eg, 500 ) operates in a first operating mode, ie, when the generator generates electricity in a high speed mode, the motor consumes power in a low speed mode, and the battery is charged. Figure 7A and Figure 7B The electrical characteristics during this first operating mode are shown. The high DC bus voltage V dc1 744 is implemented to support the generator to operate in high speed mode, low DC bus voltage V dc2 742 powers the motor inverter to support the motor operating in low speed mode, while voltage 746 is applied to the battery (e.g., 502). Figure 7A and Figure 7B As shown, the generator voltage (v G _ U 726、v G _ V 728 and v G_W 724 is the three-phase voltage) is about 130V rms, and the DC bus voltage V dc1 744 is 384V. Motor voltage (where the three-phase voltage is v M_U 738、v M_V 740 and v M_W 736) is 54V rms, and the DC bus voltage V dc2 742 is 275V. 79A rms AC phase current enables the generator to produce 30kW power in high speed mode (p G )752, the motor has 141A rms AC phase current and consumes 1.5kW(p in low speed mode M )754. This causes the battery to be at a battery voltage V b =200V 746 below p B= 27.6 kW 750 is charged. The generator stator winding carries a 49.7 ampere DC current component to deliver generated power (to neutral), and the motor stator winding carries a 3.4 ampere DC current component to consume power (from neutral). The power difference 750 is charged to the battery. In this illustration, the generator phase frequency indicated by elements 718, 720, 722, 724, 726, and 728 is twice the frequency of the motor phase frequency indicated by elements 730, 732, 734, 736, 738, and 740.

[0055] The second situation is when the generator generates electricity in the low-speed mode, the motor consumes power in the high-speed mode, and the battery is discharged.

[0056] The analysis of this situation is that the low DC bus voltage V dc1 is implemented to support the generator to operate in low speed mode while the high DC bus voltage V dc2 In the motor inverter, it is converted to support the motor operating in high-speed mode. Here, the generator voltage is 64V rms and the DC bus voltage V dc1 is 290 V. The motor voltage is 138 V rms, and the DC bus voltage V dc2 The generator generates 15kW power at 395V with a 141A rms AC phase current. G The motor has 141A rms AC phase current and consumes 53.7kW of power in high speed mode. M This results in the battery voltage V b =200V with p B = 40kW discharge. The generator stator winding carries 23.8A DC current to deliver the generated power to the neutral point of the Y-wound motor, and the motor stator winding carries 91A DC current to consume the power from the neutral point. The power difference is the amount of battery discharge. In this example, the generator phase frequency may be similar to elements 730, 732, 734, 736, 738, and 740, which will be equal to or less than half the motor phase frequency, which may be similar to elements 718, 720, 722, 724, 726, and 728.

[0057] In the third case, the generator generates electricity in a high speed mode and the motor generates electricity in a low speed mode while the battery is charged.

[0058] Here, the high DC bus voltage V dc1 is implemented to support the generator to operate in high speed mode while the low DC bus voltage V dc2 Supports the motor inverter to drive the motor in low speed mode. When the generator voltage is 395V DC bus voltage V dc1When the motor voltage is 137V rms, the bus voltage V dc2 The 142A rms AC phase current enables the generator to produce 54kW power. G , while the motor has 141A rms AC phase current and produces 9kW power in low speed mode M This results in the battery voltage V b =200V with p B = 61.6 kW for charging. The generator stator windings carry 89A DC current to deliver generated power to the battery, and the motor stator windings carry 14A DC current to the battery. In this example, the generator phase frequency may be similar to elements 718, 720, 722, 724, 726, and 728, which will be equal to or greater than twice the motor phase frequency. The motor phase frequency may be similar to elements 730, 732, 734, 736, 738, and 740.

[0059] The control logic or functions performed by the controller can be represented by a flowchart or similar diagram in one or more of the accompanying figures. These figures provide representative control strategies and / or logic that can be implemented using one or more processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). Therefore, the various steps and functions shown can be performed in the order shown, in parallel, or in some cases omitted. Although not always explicitly shown, those skilled in the art will recognize that one or more of the steps or functions shown can be performed repeatedly depending on the specific processing strategy used. Similarly, the processing order is not necessarily required to achieve the features and advantages described herein, but is provided for ease of illustration and description. The control logic can be primarily implemented by software executed by a microprocessor-based vehicle, engine, and / or powertrain controller (such as a controller). Of course, depending on the specific application, the control logic can be implemented in software, hardware, or a combination of software and hardware in one or more controllers. When implemented in software, the control logic can be provided in one or more computer-readable storage devices or media having stored data representing code or instructions executed by a computer to control the vehicle or its subsystems. Computer-readable storage devices or media may include one or more of a number of known physical devices that utilize electrical, magnetic, and / or optical storage devices to retain executable instructions and associated calibration information, operating variables, and the like.

[0060] The process, method or algorithm disclosed herein can be delivered to / implemented by a processing device, a controller or a computer, which can include any existing programmable electronic control unit or a dedicated electronic control unit. Similarly, the process, method or algorithm can be stored as data and instructions that can be executed by a controller or a computer in many forms, including but not limited to information permanently stored on a non-writable storage medium (such as a read-only memory (ROM) device) and information variably stored on a writable storage medium (such as a floppy disk, a magnetic tape, a compact disc (CD), a random access memory (RAM) device, and other magnetic and optical media). The process, method or algorithm can also be implemented in a software executable object. Alternatively, the process, method or algorithm can be implemented in whole or in part using suitable hardware components, such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a state machine, a controller or other hardware component or device, or a combination of hardware, software and firmware components.

[0061] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms covered by the claims. The words used in this specification are descriptive rather than restrictive, and it will be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As previously mentioned, the features of the various embodiments can be combined to form additional embodiments of the present invention that may not be explicitly described or illustrated. Although various embodiments may have been described as providing advantages or being preferred 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 can be compromised to implement the desired system properties, depending on the specific application and implementation. These properties may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Therefore, embodiments described as being less than desired in terms of one or more characteristics compared to other embodiments or prior art implementations are not outside the scope of this disclosure and may be desired for a specific application.

[0062] According to the present invention, a powertrain for a vehicle is provided, the powertrain having: a Y-wound generator and a Y-wound motor, the Y-wound generator and the Y-wound motor coupled via each respective neutral terminal; a generator inverter coupled between the Y-wound generator and a generator bus; a motor inverter coupled between the Y-wound motor and a motor bus; and a traction battery having a first terminal coupled to each neutral terminal and a second terminal coupled to bus terminals of the generator bus and the motor bus.

[0063] According to one embodiment, the bus terminal is a negative bus terminal of the generator bus and the motor bus.

[0064] According to one embodiment, the above invention further features a controller configured to modulate switches of the generator inverter and the motor inverter such that the voltage level of the generator bus varies independently of the motor bus.

[0065] According to one embodiment, the above invention further features a generator bus capacitor and a motor bus capacitor, wherein the generator bus voltage level is filtered by the generator bus capacitor and the motor bus voltage level is filtered by the motor bus capacitor.

[0066] According to one embodiment, the switch is an insulated gate bipolar junction transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET).

[0067] According to one embodiment, the above invention is further characterized by: a generator controller, which is configured to modulate the switches of the generator inverter; and a motor controller, which is configured to modulate the switches of the motor inverter so that the generator phase frequency is independent of the motor phase frequency.

[0068] According to one embodiment, the generator phase frequency is at least twice the motor phase frequency.

[0069] According to one embodiment, the motor phase frequency is at least twice the generator phase frequency, and current flows from the first terminal of the traction battery to the motor.

[0070] According to the present invention, a powertrain control method is provided, the powertrain control method having the following features: in a propulsion mode, directing current from a battery to a first neutral terminal of a first motor and a second neutral terminal of a second motor; modulating a first set of switches of a first inverter to output a first bus voltage; and modulating a second set of switches of a second inverter to output a second bus voltage different from the first bus voltage.

[0071] According to one embodiment, the above method is further characterized by directing current from the first neutral terminal and the second neutral terminal to the battery in charging mode.

[0072] According to one embodiment, the above method, the modulation of the first set of switches of the first inverter causes current to flow from the battery to the first electric machine to provide propulsion.

[0073] According to one embodiment, in the above method, the modulation of the first set of switches is at a first frequency, and the modulation of the second set of switches is at a second frequency that is greater than twice the first frequency.

[0074] According to one embodiment, the above invention is further characterized by directing current from the first terminal to the battery and the second neutral terminal in a hybrid operating mode.

[0075] According to one embodiment, the modulation of the first set of switches of the first inverter causes current to flow from the battery to the first electric machine to provide propulsion.

[0076] According to one embodiment, the modulation of the first set of switches is at a first frequency, and the modulation of the second set of switches is at a second frequency that is less than half of the first frequency.

[0077] According to the present invention, a vehicle powertrain is provided, having a generator having a first neutral terminal, a motor having a second neutral terminal coupled to the first neutral terminal, and a traction battery having a first terminal coupled to the first neutral terminal and the second neutral terminal.

[0078] According to one embodiment, the above invention is further characterized by: a generator inverter coupled between the generator and a generator bus; a motor inverter coupled between the motor and a motor bus, wherein the traction battery further includes a second terminal coupled to return terminals of the generator bus and the motor bus.

[0079] According to one embodiment, the above invention further features a controller configured to modulate switches of the generator inverter and the motor inverter such that the voltage level of the generator bus varies independently of the motor bus.

[0080] According to one embodiment, the above invention is further characterized by: a generator controller, which is configured to modulate the switches of the generator inverter; and a motor controller, which is configured to modulate the switches of the motor inverter so that the generator phase frequency is independent of the motor phase frequency.

[0081] According to one embodiment, the generator phase frequency is at least twice the motor phase frequency, and current flows from the first terminal of the traction battery to the motor.

Claims

1. A power transmission system for a vehicle, comprising: a Y wound rotor generator and a Y wound rotor motor, the Y wound rotor generator and the Y wound rotor motor being coupled via each respective neutral terminal; a generator inverter coupled between phase terminals of the Y-wound generator and a generator bus; a motor inverter coupled between phase terminals of the Y wound-rotor motor and a motor bus; as well as a traction battery having a first terminal coupled to each neutral terminal and a second terminal coupled to bus terminals of the generator bus and the motor bus such that current to and from the traction battery passes through the neutral terminal, The powertrain system further includes a generator controller and a motor controller, wherein the generator controller is configured to modulate switches of the generator inverter, and the motor controller is configured to modulate switches of the motor inverter so that the generator phase frequency is independent of the motor phase frequency.

2. The power transmission system according to claim 1, wherein: The bus terminal is a negative bus terminal of the generator bus and the motor bus.

3. The power transmission system according to claim 1, wherein: The generator controller is configured to modulate switches of the generator inverter, and the motor controller is configured to modulate switches of the motor inverter so that a voltage level of the generator bus varies independently of the motor bus. 4 . The powertrain system of claim 3 , further comprising a generator bus capacitor and a motor bus capacitor, wherein the generator bus voltage level is filtered by the generator bus capacitor and the motor bus voltage level is filtered by the motor bus capacitor.

5. The power transmission system according to claim 3, wherein: The switch is an insulated gate bipolar junction transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET).

6. The power transmission system according to claim 1, wherein: The generator phase frequency is at least twice the motor phase frequency.

7. The power transmission system according to claim 1, wherein: The motor phase frequency is at least twice the generator phase frequency, and current flows from the first terminal of the traction battery to the motor.

8. A method for controlling a power transmission system, wherein: The power transmission system includes: a first electric machine and a second electric machine, the first electric machine and the second electric machine being coupled via each corresponding neutral terminal; a first inverter coupled between phase terminals of the first motor and a first motor bus; a second inverter coupled between the phase terminals of the second electric machine and a second motor bus; and a battery having a first terminal coupled to each neutral terminal and a second terminal coupled to bus terminals of the first motor bus and the second motor bus such that current into and out of the battery passes through the neutral terminal, The control method includes: In push mode, directing current from the battery to a first neutral terminal of the first electric machine and a second neutral terminal of the second electric machine; modulating a first set of switches of the first inverter to output a first bus voltage; and A second set of switches of a second inverter is modulated to output a second bus voltage different from the first bus voltage.

9. The power transmission system control method according to claim 8, further comprising: In a charging mode, current is directed from the first neutral terminal and the second neutral terminal to a battery.

10. The control method of the power transmission system according to claim 9, wherein: The modulation of the first set of switches of the first inverter causes current to flow from the battery to the first electric machine to provide propulsion.

11. The control method of a power transmission system according to claim 9, wherein: The modulation of the first set of switches is at a first frequency, and the modulation of the second set of switches is at a second frequency greater than twice the first frequency.

12. The power transmission system control method according to claim 8, further comprising: In a hybrid operating mode, current is directed from the first terminal to the battery and the second neutral terminal.

13. The control method of the power transmission system according to claim 12, wherein: The modulation of the first set of switches of the first inverter causes current to flow from the battery to the first electric machine to provide propulsion.

14. The control method of the power transmission system according to claim 12, wherein: The modulation of the first set of switches is at a first frequency, and the modulation of the second set of switches is at a second frequency that is less than half the first frequency.

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