Electric motor with integrated charger

Abstract

A vehicle comprising: an electric machine having two sets of galvanically isolated windings, a first inverter and a second inverter, a switch device, and a controller. During charging, the controller operates the switch device to isolate the first inverter from the electric machine to allow charging current to flow through one of the sets and induce a voltage in the other of the sets. During propulsion, the controller operates the switch device to couple the first inverter to the one of the sets so that the first inverter and the second inverter are configured to power only one of the sets.

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] The vehicle has an electric machine including two sets of galvanically isolated windings, a first inverter and a second inverter, a traction battery, and a switch device. During charging, the switch device isolates the first inverter from the electric machine so that current from a charging port coupled to a 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 vehicle has an electric machine including two sets of galvanically isolated windings, a first inverter and a second inverter associated with only one of the sets, and a controller that isolates the first inverter from the electric machine during charging to allow charging current to flow through one of the sets and induce a voltage in the other of the sets, and couples the first inverter to the one of the sets during propulsion.

[0005] A method for operating a vehicle powertrain system includes isolating, by a controller, a first inverter from a first set of windings of an electric machine in response to a charging mode, and coupling a second inverter to a second set of windings of the electric machine, the second set of windings being galvanically isolated from the first set such that current from a charging port coupled to a source flows through the first set and induces a voltage in the second set to charge a traction battery while isolating the source from the traction 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 may 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 may 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 persistent non-writable storage media (such as ROM devices), and information variably stored on writable storage media (such as floppy disks, tapes, CDs, RAM devices and other magnetic and optical media). Processes, methods, logic or strategies may also be implemented in software executable objects. Alternatively, they may 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 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. On-board chargers provide the flexibility to charge anywhere an electrical outlet is available. On-board chargers have the potential disadvantage of adding weight, volume, and cost to the vehicle. Therefore, any possibility to avoid 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 is relative to a 1 The angle between the phase axis and 1 , and relative to a 2 Phase axis is θ 2 , and α = θ 2 -θ 1 .

[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] (1)

[0022] (2)

[0023] (3)

[0024] 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, Iqi 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 q1 is 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, isI 1 and V 1 The angle between 1 and E q1 The angle between them, and δ is V q1 and E q1 The angle between.

[0025] 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.

[0026] 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:

[0027] (4)

[0028] In this case, if 1 = 2 = , then the effective inductance becomes:

[0029] (5)

[0030] Among them Ψ 1 is the magnetic flux of coil 1, Ψ 2 is the magnetic flux of coil 2, M is the mutual inductance of the coil, L1 is the inductance of coil 1, L 2 is the inductance of coil 2, and i is the total current. Furthermore, when α = 0, M becomes close to L and the effective equivalent inductance becomes L. At the same time, the coupling coefficient between 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.

[0031] 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 also contemplated. For example, such configurations need not include a transmission 33 or a clutch 40, etc.

[0032] 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 .

[0033] Figure 6 Shown for Figure 5 38. 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, an inductor set 60 and switches S1 to S7. The vehicle 32 also includes an EMI filter 62 and a charging port 64. The charging port 64 is shown as being coupled to a remote power source 66. In traction mode, the controller 49 ( Figure 5) connects switches S1, S2, and S3 between winding 52 and inverter 56, opens switches S5, S6, and S7 to disconnect inverter 56 from inductor bank 60, and connects switch S4 between traction battery 46 and inverter 58 to disconnect inverter 58 from inductor bank 60. (In traction mode, charging port 64 is of course not coupled to remote power source 66.) In charging mode, controller 49 connects switches S1, S2, and S3 between winding 52 and EMI filter 62, closes switches S5, S6, and S7, and connects switch S4 between inverter 58 and inductor bank 60 to couple traction battery 46 to remote power source 66. Thus, charging port 64 is completely isolated from traction battery 46 in both traction mode and charging mode.

[0034] The electric motor 42 acts as a transformer, which is connected to a power source 66 via an EMI filter 62. These components provide an isolation stage. The inverter 58 acts as a rectifier that feeds a DC-DC boost converter formed by the inverter 56 and an inductor bank 60. The DC-DC boost converter provides voltage regulation for charging and also acts as a power factor correction stage.

[0035] Some embodiments may provide certain advantages. The power supply may be single-phase, two-phase, or three-phase. The main rectifier phase of the on-board charger may be removed. The DC / AC converter is removed. The electric motor may be used as a transformer. The AC / DC stage is implemented using an existing inverter. The DC-DC converter is implemented via an inverter and an inductor bank. The presence of three inductors and a three-phase inverter may allow an interleaved control strategy, which may further reduce the size and cost of the inductor bank. The interleaved control strategy may reduce the stress on the DC link capacitor of the inverter 56. The elimination of the rectifier stage and the DC / AC converter may improve the efficiency of the system.

[0036] 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 motor including two sets of current-isolated windings; a first inverter associated with one of the two sets of galvanically isolated windings; A second inverter connected to the other of the two groups of current isolation windings; Traction batteries; as well as a switching device disposed between the first inverter and the set of windings and configured to disconnect the first inverter from the set of windings during charging so that current from a charging port coupled to a source flows through the set of windings and induces a voltage in the other set of windings to charge the traction battery while isolating the source from the traction battery, The vehicle further includes an inductor bank and an additional switch device, wherein the additional switch device is further configured to couple the inductor bank with the first inverter to boost the voltage rectified by the second inverter.

2. The vehicle according to claim 1, wherein: The switch arrangement is further configured to couple the first inverter to the set of windings while isolating the port from the traction battery during vehicle propulsion.

3. The vehicle according to claim 1, wherein: The second inverter is configured to rectify the voltage.

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

5. A vehicle comprising: A motor including two sets of current-isolated windings; a first inverter associated with one of the two sets of galvanically isolated windings; A second inverter connected to the other of the two groups of current isolation windings; as well as a switching device disposed between the first inverter and the set of windings and configured to disconnect the first inverter from the set of windings during charging to allow charging current to flow through the set of windings and induce a voltage in the other set of windings, and to couple the first inverter to the set of windings during vehicle propulsion, The vehicle further includes an inductor bank and an additional switch device, wherein the additional switch device is further configured to couple the inductor bank with the first inverter to boost the voltage rectified by the second inverter.

6. The vehicle according to claim 5, wherein: The second inverter is configured to rectify the voltage.

7. The vehicle according to claim 5, wherein: Isolating the first inverter from the electric machine isolates the traction battery from a charging port coupled to a charging current source.

8. The vehicle according to claim 5, wherein: Coupling the first inverter with the set of windings isolates the traction battery from the coupled charging port.

9. The vehicle according to claim 5, wherein: The motor is a six-phase motor.

10. A method for operating a vehicle powertrain system, comprising: In response to the charging mode, a first inverter is disconnected from a first set of windings of the electric machine by a controller, and a second inverter is coupled to a second set of windings of the electric machine, and the second set of windings is galvanically isolated from the first set of windings, so that current from a charging port coupled to a source flows through the first set of windings and induces a voltage in the second set of windings to charge a traction battery, while isolating the charging port from the traction battery, The method further includes boosting the voltage rectified by the second inverter through an inductor group and the first inverter.

11. The method according to claim 10, further comprising: The voltage is rectified by the second inverter.

12. The method according to claim 10, further comprising: In response to a vehicle propulsion mode, the first inverter is coupled to the first set of windings and the second inverter is coupled to the second set of windings by the controller, so that the first inverter is configured to power only the first set of windings and the second inverter is configured to power only the second set of windings, while isolating the charging port from the traction battery.

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