Electrified powertrain with integrated charger

Abstract

A vehicle having: an electric machine including two sets of galvanically isolated windings; first and second inverters, each inverter coupled to only one of the sets; and a traction battery. The vehicle also has a switch arrangement that couples the first inverter to a port during charging so that current from a remote source flows through one of the sets and induces a voltage in the other of the sets while isolating the source from the battery.

Description

Technical Field

[0001] The present disclosure relates to an electric drive system for a motor vehicle, and a charging device associated with the electric drive system. Background Art

[0002] Hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs) may rely on a traction battery to power a traction motor for propulsion, and a power inverter between the traction battery and the traction motor to convert direct current (DC) power to alternating current (AC) power. A typical AC traction motor is a three-phase motor that may be powered by three sinusoidal signals, each driven with 120 degrees of phase separation. Furthermore, many electrified vehicles may include a DC-DC converter to convert the voltage of the traction battery to an operating voltage level for the traction motor. Summary of the invention

[0003] A vehicle has: an electric machine including two sets of galvanically isolated windings; first and second inverters, each inverter coupled to only one of the sets; a traction battery; and a switch arrangement coupling the first inverter to a port so that current from a remote source flows through one of the sets and induces a voltage in the other of the sets to charge the battery while isolating the source from the battery.

[0004] A method for a vehicle powertrain system includes coupling a first inverter to a charging port via a controller so that current from a remote source flows through the first inverter and a first set of windings of an electric machine and induces a voltage in a second set of windings of the electric machine, the second set of windings being isolated from the first set of current, to charge a traction battery while isolating the battery from the source.

[0005] A vehicle has: an electric machine including two sets of galvanically isolated windings; a traction battery; and a switch device. During charging, the switch device couples one of the sets to a charging port so that current from a remote source flows through the one set and induces a voltage in the other of the sets to charge the battery while isolating the source from the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a block diagram of a typical on-board motor vehicle charger.

[0007] Figure 2 is a schematic diagram of a multi-phase motor.

[0008] Figure 3 is the phasor diagram of a multiphase motor.

[0009] Figure 4A and Figure 4B is a schematic diagram of the effective inductance of the motor.

[0010] Figure 5 is a block diagram of a vehicle with an integrated charger.

[0011] Figure 6 is a schematic diagram of an electric drive for a six-phase electric motor. DETAILED DESCRIPTION

[0012] Various embodiments of the present disclosure are described herein. However, the disclosed embodiments are merely exemplary, and other embodiments may take various and alternative forms that are not explicitly shown or described. The drawings are not necessarily drawn to scale; some features may be enlarged or minimized to show the details of a particular component. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching a person of ordinary skill in the art to use the present invention in various ways. As will be understood by a person of ordinary skill in the art, the various features shown and described with reference to any one of the figures may be combined with the features shown in one or more other figures to produce embodiments that are not explicitly shown or described. The combination of features shown provides representative embodiments of typical applications. However, for specific applications or implementations, various combinations and modifications of features consistent with the teachings of the present disclosure may be required.

[0013] The disclosed processes, methods, logic or strategies can be delivered to and / or implemented by a processing device, a controller or a computer, which may include any existing programmable electronic control unit or a dedicated electronic control unit. Similarly, processes, methods, logic or strategies can be stored in many forms as data and instructions that can be executed by a controller or a computer, including but not limited to information permanently stored on various types of articles that may include a persistent non-writable storage medium (such as a ROM device), and information variably stored on a writable storage medium (such as a floppy disk, a tape, a CD, a RAM device and other magnetic and optical media). Processes, methods, logic or strategies can also be implemented in software executable objects. Alternatively, they can be implemented in whole or in part using suitable hardware components (such as application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), state machines, controllers or other hardware components or devices) or a combination of hardware, software and firmware components.

[0014] Despite the differences in their architecture, electric vehicles (EVs) have similarities in their structure. For example, batteries, inverters, and electric motors are typically the main building blocks of any EV. To energize the batteries and power the motors, two types of chargers are employed: on-board chargers and off-board (standalone) chargers. The on-board charger provides the flexibility to charge anywhere an electrical outlet is available. The on-board type has the potential disadvantage of increasing the weight, volume, and cost of the vehicle. Therefore, any possibility of avoiding the additional charger weight, space, and cost issues by charging the battery using available hardware (primarily the electric motor and inverter) is desirable. Considering the case of EVs: during the charging time, the vehicle is not driven, and it is not desirable to charge the battery pack during driving time, except for regeneration during braking, the integration of the on-board charger and the traction system seems to be a viable option.

[0015] As with any integrated system, specific requirements for the on-board charger (including galvanic isolation) need to be met. Other aspects to consider with regard to the integrated charger are voltage level adaptability, unwanted torque development in the motor during charging, efficiency, low harmonic content in the current from the grid, and possible forced unity power factor operation.

[0016] Different types of integrated chargers have been previously reported due to the many advantages that integrated chargers can introduce to a system. However, most of these integrated chargers lack galvanic isolation in their structure. Here, some proposed integrated chargers provide galvanic isolation for the charging process.

[0017] Currently, some manufacturers do not use an integrated charger, but instead focus on on-board chargers that do not use electric drive components. Figure 1 A vehicle 10 is shown having an on-board charger device 12 operably arranged with a power source 14. The on-board charger device 12 includes a charging port 16, an electromagnetic interference (EMI) filter 18, a diode bridge 20, a DC / AC converter 22, a transformer 24, an AC / DC filter 26, a boost converter 28, and a traction battery 30. The EMI filter 18 reduces high frequency electronic noise before providing input to the diode bridge 20. The transformer 24 provides isolation between the DC / AC converter 22 and the AC / DC converter 26. The boost converter 28 performs power factor correction (and possibly voltage regulation) to output from the AC / DC converter 26 before providing input to the traction battery 30.

[0018] For high power applications (e.g., electric vehicles), large AC motors sometimes include multiple windings powered by multiple inverters ( Figure 2). Here, a1 is the a-phase inductance of winding 1, a2 is the a-phase inductance of winding 2, b1 is the b-phase inductance of winding 1, b2 is the b-phase inductance of winding 2, c1 is the c-phase inductance of winding 1, c2 is the c-phase inductance of winding 2, d1 is the inductance of winding 1 along the d-axis, d2 is the inductance of winding 2 along the d-axis, q1 is the inductance of winding 1 along the q-axis, q2 is the inductance of winding 2 along the q-axis, and ω is the electrical speed. The rotor d-axis makes an angle θ1 with respect to the a1-phase axis and θ2 with respect to the a2-phase axis, and α = θ2- θ1.

[0019] Due to the structure of these multi-phase machines, in addition to the individual phases, mutual inductance (magnetic coupling) between phase groups is inevitable. This is useful not only for determining performance and designing control systems, but also for analyzing fault tolerance. This cross-coupling between windings (phases) can form a transformer when energy is injected into only one set of windings.

[0020] Under AC steady-state conditions, the d-axis and q-axis flux linkages Ψ d and q The RMS values ​​can be combined into phase quantities:

[0021]

[0022] Where i = 1, 2 and V di = R i I di -X qi I qi -X q1q2 I q2 and V qi = E qi + R i I qi + X di I di +X d1d2 I d2 These equations are Figure 3 is described graphically in , where Ψ di is the flux linkage of winding i along the d-axis, Ψ qi is the flux linkage of winding i along the q axis, Ψ i is the total flux linkage of winding i, I di is the current of winding i along the d axis, I qi is the current in winding i along the q axis, I i is the total current of winding i, V di is the voltage applied to winding i along the d-axis, V qi is the voltage applied to winding i along the q axis, V i is the total voltage applied to winding i, Ri is the resistance of winding i, ω is the electrical velocity, E q1is the back electromotive force (EMF) along the q-axis seen by winding 1, X d1 is the reactance of winding 1 along the d-axis, X q1 is the reactance of winding 1 along the q axis, X d1d2 is the mutual reactance of windings 1 and 2 along the d-axis, X q1q2 is the mutual reactance of windings 1 and 2 along the q-axis, is the angle between I1 and V1, and γ is the angle between I1 and E q1 The angle between them, and δ is V q1 and E q1 The angle between.

[0023] The cross-coupling terms appear in the phasor diagram as additional voltage drops which tend to limit the current. If α = 0 (the angle between the phase groups), there is a tightly coupled inductance between the two groups, as has already been observed; if the groups are supplied by a common voltage source, the current in each group will be approximately half of the current that would flow in one group if the other group was open-circuited. This is a practical point, for it means that in a two-winding, if one group is open-circuited, the current in the other group may increase by a factor approaching 200% if it is not regulated. Similarly, if one group is short-circuited, the impedance of the second group will decrease, and its current may also increase to high values ​​if it is not regulated.

[0024] The behavior of the double group is similar to that of a parallel inductor, see Figure 4A and Figure 4B , where the equivalent inductance is:

[0025]

[0026] In this case, if 1 = 2 = , then the effective inductance becomes:

[0027]

[0028] Where Ψ1 is the magnetic flux of coil 1, Ψ2 is the magnetic flux of coil 2, M is the mutual inductance of the coils, L1 is the inductance of coil 1, L2 is the inductance of coil 2, and i is the total current. Moreover, when α = 0, M becomes close to L and the effective equivalent inductance becomes L. At the same time, the coupling coefficient between the phases will be k = 1 (theoretically). The total current is the current limited by L and is half of the current flowing in each group. But if one group is open, the same total current will tend to flow in one group. This means that regulation of the current may help.

[0029] Since the traction system and the on-board charger cannot function simultaneously, and given the acceptable amount of coupling between phases, as described above, using a multiphase motor as a transformer to create isolation for the on-board charger seems to be a logical approach. Figure 5 A high-level proposed architecture for integrating an onboard charger and traction system is shown. In this example, a vehicle 32 includes a transmission 33 and a differential 34, which are arranged to directly drive a wheel / tire assembly 36. (The wheel / tire assembly 37 follows the driving wheel / tire assembly 36.) The vehicle 32 also includes an electric drive system 38, which is configured to selectively couple with the transmission 33 via a clutch 40. The electric drive system 38 includes an electric motor 42, an inverter and a winding switch device 44, and a traction battery 46. The inverter and the winding switch device 44 are arranged to receive power from an external charging line 48. The power received from the external charging line 48 can be provided to the traction battery 46 via the inverter and the winding switch device 44 for charging purposes. Similarly, the power received from the traction battery 46 can be provided to the electric motor 42 via the inverter and the winding switch device 44 to operate the electric motor 42. The controller 49 (or controller, used interchangeably herein) communicates with and controls the electric drive system 38. Of course, other and / or different vehicle configurations are contemplated. For example, such configurations need not include a transmission 33 or a clutch 40, etc.

[0030] As explained in further detail below, the inverter and winding switching arrangement 44 and the electric motor 42 function as a traction system during vehicle propulsion and participate in the charging process during charging of the traction battery 46 .

[0031] Figure 6 Shown for Figure 5 A proposed topology of an electric drive system 38 of FIG. 4 is shown. In this example, the electric motor 42 includes two sets of windings 52, 54, and the inverter and winding switching device 44 includes a pair of inverters 56, 58 and switches S1, S2. The vehicle 32 also includes a power factor correction stage 61 and a diode bridge rectifier stage 62, an EMI filter 63, and a charging port 64. The charging port 64 is shown as being coupled to a remote power source 66.

[0032] In the traction mode, the controller 49 ( Figure 5 ) Switches S1, S2 are connected to position 1 between the traction battery 46 and the inverter 56, thereby isolating the inverter 56 from the charging port 64. The traction battery 46 is thus connected to both inverters 56, 58. Each of the inverters 56, 58 can provide half of the required power to the windings 52, 54, respectively, and the controller 49 can synchronize control and power flow. (In traction mode, the charging port 64 will of course not be connected to the remote power source 66.)

[0033] In charging mode, the controller 49 ( Figure 5 ) connects switches S1, S2 to position 2 between the inverter 56 and the power factor correction stage 61. The DC link capacitor of the inverter 56 is charged by the power factor correction stage 61, and the inverter 56 converts this DC power to AC power (with the required frequency). The AC power flows through the winding 52, which induces a voltage at the winding 54 and a corresponding current flows through the winding 54. The inverter 58 then rectifies the current before injecting it into the traction battery 46. Therefore, in both the traction mode and the charging mode, the charging port 64 is completely isolated from the traction battery 46.

[0034] Given the power levels transmitted through the windings 52, 54 and the core (e.g., ~8 kW), core saturation is unlikely. Also to achieve a zero voltage source, a three-phase inductor can be added in series with the windings 52 if the leakage inductance of the motor 42 is not high enough to achieve this. Additionally, if the coupling coefficient is not high enough, a set of inductors and capacitors (resonant tank) can be added in series with the windings 52.

[0035] During the charging process, maximum coupling and therefore maximum mutual inductance is desired. The controller 49 can place the rotor of the motor 42 (in the case of a permanent magnet motor) in a position that provides the maximum coupling coefficient between the phases. Using a resolver can simplify this task. For example, known testing or simulation techniques can be used to identify the rotor position that maximizes the coupling coefficient. This position can then be stored in a memory accessible to the controller 49 (or obtained online during operation), so that before charging, the controller 49 can identify the current rotor position via the resolver and then move the rotor to the desired position to maximize coupling. Other techniques can also be used.

[0036] Some embodiments may provide certain advantages. The DC-DC stage of the on-board charger may be eliminated. The power level may be higher than an equivalent level 1 or level 2 charger. The maximum power capability depends on the motor architecture and the core saturation limit. The proposed integrated charger may be bidirectional to transfer power between the grid and the battery. By changing the design of the power factor correction stage, the diode bridge rectifier stage and the EMI filter, the proposed converter may be used for single-phase, two-phase or three-phase input from the utility grid.

[0037] The words used in the specification are descriptive rather than restrictive, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure and claims. As previously mentioned, the features of the various embodiments can be combined to form other embodiments that may not be explicitly described or shown. Although various embodiments may have been described as providing advantages or being preferred with respect to one or more desired characteristics compared to other embodiments or prior art implementations, it is recognized by those of ordinary skill in the art that one or more features or characteristics may be compromised to achieve the desired overall system properties, depending on the specific application and implementation. These properties include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, applicability, weight, manufacturability, ease of assembly, etc. Therefore, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the present disclosure and may be desirable for specific applications.

Claims

1. A vehicle comprising: A traction motor including two sets of current-isolated windings; a first inverter and a second inverter, each inverter being coupled to only one of the two sets of galvanically isolated windings; Traction batteries; as well as A switch device is configured to: couple the first inverter with the port during charging so that current from a remote source flows through one of the two sets of galvanic isolation windings after DC to AC conversion by the first inverter and induces a voltage in the other of the two sets of galvanic isolation windings to charge the traction battery while isolating the remote source from the traction battery; and couple the first inverter with the traction battery during vehicle propulsion while isolating the port from the first inverter.

2. The vehicle according to claim 1, wherein: The second inverter is configured to rectify the voltage. 3 . The vehicle of claim 1 , further comprising a controller configured to move a rotor of the traction motor to a target position prior to charging the traction battery.

4. The vehicle according to claim 1, wherein: The traction motor is a six-phase motor.

5. A method for a vehicle power system, the vehicle power system comprising a traction motor, a first inverter and a second inverter, the traction motor comprising two sets of current-isolated windings, each inverter being coupled to only one of the two sets of current-isolated windings, wherein: The method comprises: coupling a first inverter to a charging port via a switching device during charging so that current from a remote source flows through a first set of windings of a traction motor after direct current to alternating current conversion by the first inverter and induces a voltage in a second set of windings of the traction motor galvanically isolated from the first set of windings to charge a traction battery while isolating the traction battery from the remote source; and In response to a vehicle propulsion mode, the first inverter is coupled to the traction battery through the switching device while isolating the charging port from the first inverter.

6. The method according to claim 5, further comprising: The voltage is rectified by a second inverter.

7. The method according to claim 5, further comprising: Prior to charging the traction battery, a rotor of the traction motor is moved to a target position.

8. A vehicle power system, comprising: A traction motor including two sets of current-isolated windings; a first inverter coupled to one of the two sets of galvanically isolated windings; a second inverter coupled to the other of the two groups of galvanically isolated windings; Traction batteries; as well as A switch device is configured to: couple one of the two sets of galvanic isolation windings with a charging port during charging so that current from a remote source flows through the one set after DC to AC conversion by the first inverter and induces a voltage in the other set of the two sets of galvanic isolation windings to charge the traction battery while isolating the remote source from the traction battery; and couple the first inverter with the traction battery during vehicle propulsion while isolating the port from the first inverter.

9. The vehicle power system according to claim 8, wherein: The second inverter is configured to rectify the voltage. 10 . The vehicle powertrain system of claim 8 , the vehicle further comprising a controller configured to move a rotor of the traction motor to a target position prior to charging the traction battery.

11. The vehicle power system according to claim 8, wherein: The traction motor is a six-phase motor.

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