Electric vehicle propulsion and charging system

Abstract

A motor vehicle includes an AC (alternating current) electric motor having a stator with a plurality of stator windings; a rechargeable stored electrical energy source; and an inverter coupled to the rechargeable stored electrical energy source and the AC electric motor. The system also includes one or more controllers co-programmed to switch the inverter to provide AC propulsion energy to the plurality of stator windings from a rechargeable stored electrical energy source, and to charge the plurality of stator windings using at least one of the stator windings as a boost inductor. The inverter is switched to step up a voltage at a charging input coupled to the inverter to charge the rechargeable stored electrical energy source.

Description

[0001] introduction The present disclosure is in the field of electric vehicle propulsion and charging.

[0002] In an electric vehicle, an electrical energy source such as one or more traction batteries may provide energy for propulsion of the electric vehicle. The traction batteries of the electric vehicle may need to be recharged. The traction batteries of newer electric vehicles may have a higher nominal voltage than the output voltage of conventional battery chargers installed in the field. Therefore, a system may be advantageous that may facilitate charging the traction batteries of the electric vehicle using a battery charger having an output voltage lower than the nominal voltage of the traction batteries. Summary of the invention

[0003] A motor vehicle includes: an AC (alternating current) electric motor having a stator with a plurality of stator windings; a rechargeable stored electrical energy source; and an inverter coupled to the rechargeable stored electrical energy source and the AC electric motor. The motor vehicle also includes one or more controllers that are collectively programmed to: switch the inverter to provide AC propulsion energy from the rechargeable stored electrical energy source to the plurality of stator windings; and use at least one of the stator windings as a boost inductor to switch the inverter to step up the voltage at a charging input coupled to the inverter to charge the rechargeable stored electrical energy source. The rechargeable stored electrical energy source may include a battery. Further, the inverter may be an inverter having more than two output voltage levels. Still further, the inverter may be a two-level inverter. Additionally, the AC electric motor may be a six-phase AC electric motor.

[0004] The plurality of stator windings may include a first set of three-phase stator windings connected in star and a second set of three-phase stator windings connected in star, the first set of three-phase stator windings connected in star having a first neutral point, and the second set of three-phase stator windings connected in star having a second neutral point. The AC electric motor may include a switchable contact inserted between the first neutral point and the second neutral point. Additionally, the one or more controllers may be further collectively programmed to: cause the switchable contact to open when the inverter is switched to provide AC propulsion energy to the plurality of stator windings from a rechargeable stored electrical energy source; and cause the switchable contact to close when the inverter is switched to step up a voltage at a charging input coupled to the inverter to charge the rechargeable stored electrical energy source.

[0005] In the motor vehicle, the charger may be switchably coupled to the inverter via a switchable contact. Additionally, the one or more controllers may be further collectively programmed with instructions to cause the switchable contact to close when the inverter is switched to step up the voltage at the charging input to charge the rechargeable stored electrical energy source.

[0006] Additionally, the instructions to switch the inverter to step up the voltage from the charging input to charge the rechargeable electrical energy source may further include instructions to perform a two-phase interleaved step-up conversion.

[0007] A method for controlling an electric vehicle propulsion and charging system, comprising: switching an inverter to provide AC propulsion energy from a rechargeable storage electrical energy source to a plurality of stator windings of an AC electric motor; and using at least one of the stator windings as a boost inductor, switching the inverter to step up a voltage from a charging input coupled to the inverter to charge the rechargeable storage electrical energy source. The rechargeable storage electrical energy source may include a battery. Further, the inverter may be an inverter having more than two output voltage levels. Still further, the inverter may be a two-level inverter. Still additionally, the AC electric motor may be a six-phase AC electric motor. Furthermore, switching the inverter to upconvert the voltage from the charging input to charge the rechargeable storage electrical energy source may include performing a two-phase interleaved step-up conversion.

[0008] The plurality of stator windings may include a first set of three-phase stator windings connected in star and a second set of three-phase stator windings connected in star, the first set of three-phase stator windings connected in star having a first neutral point, and the second set of three-phase stator windings connected in star having a second neutral point. The electric vehicle propulsion and charging system may further include a switchable contact inserted between the first neutral point and the second neutral point. The method may additionally include: causing the switchable contact to open when the inverter is switched to provide AC propulsion energy to the plurality of stator windings from a rechargeable stored electrical energy source; and causing the switchable contact to close when the inverter is switched to up-convert a voltage from a charging input to charge the rechargeable stored electrical energy source. The battery charger may be switchably coupled to the inverter via the switchable contact. Further, the method may include: causing the switchable contact to close when the inverter is switched to up-convert a voltage from a charging input to charge the rechargeable stored electrical energy source.

[0009] A second motor vehicle includes an AC electric motor having a stator with a plurality of stator windings, the plurality of stator windings including a first set of three-phase stator windings connected in star connection with a first neutral point and a second set of three-phase stator windings connected in star connection with a second neutral point, the AC electric motor additionally including a switchable contact inserted between the first neutral point and the second neutral point. The second motor vehicle additionally includes a rechargeable stored electrical energy source and an inverter coupled to the rechargeable stored electrical energy source and the AC electric motor. Further, the second motor vehicle includes one or more controllers commonly programmed with the following instructions: causing the switchable contacts to open and switching the inverter to provide AC propulsion energy from the rechargeable stored electrical energy source to the plurality of stator windings; and causing the switchable contacts to close and using at least one of the stator windings as a boost inductor, switching the inverter to step up a voltage at a charging input coupled to the inverter to charge the rechargeable stored electrical energy source.

[0010] In the second motor vehicle, the charging input may be switchably coupled to the inverter via a second switchable contact. Additionally, the one or more controllers may be further collectively programmed with instructions to cause the second switchable contact to close when the inverter is switched to step up the voltage at the charging input to charge the rechargeable stored electrical energy source. Still further, the instructions to switch the inverter to step up the voltage at the charging input to charge the rechargeable electrical energy source may additionally include instructions to perform a two-phase interleaved step-up conversion. The inverter may be a two-level inverter.

[0011] The present disclosure provides the following embodiments.

[0012] 1. A motor vehicle comprising: AC (alternating current) electric motor having a stator with a plurality of stator windings; Rechargeable electrical energy storage; an inverter coupled to the rechargeable stored electrical energy source and the AC electric motor; One or more controllers that are collectively programmed using the following instructions: switching an inverter to provide AC propulsion energy from a rechargeable stored electrical energy source to the plurality of stator windings; and The inverter is switched to step up a voltage at a charging input coupled to the inverter to charge a rechargeable stored electrical energy source using at least one of the stator windings as a boost inductor.

[0013] 2. A motor vehicle according to embodiment 1, wherein the rechargeable source of stored electrical energy comprises a battery.

[0014] 3. The motor vehicle of embodiment 2, wherein the inverter is an inverter having more than two output voltage levels.

[0015] 4. The motor vehicle of embodiment 2 wherein the inverter is a two-level inverter.

[0016] 5. The motor vehicle of embodiment 2, wherein: The plurality of stator windings include a first set of three-phase star-connected stator windings and a second set of three-phase star-connected stator windings, the first set of three-phase star-connected stator windings having a first neutral point and the second set of three-phase star-connected stator windings having a second neutral point; The AC electric motor vehicle further includes a switchable contact interposed between the first neutral point and the second neutral point; and the one or more controllers are further collectively programmed with the following instructions: causing the switchable contacts to open when the inverter is switched to provide AC propulsion energy from the rechargeable stored electrical energy source to the plurality of stator windings; and The switchable contacts are caused to close when the inverter is switched to step up the voltage at the charging input to charge the rechargeable stored electrical energy source.

[0017] 6. The motor vehicle of embodiment 2, wherein: The charging input is switchably coupled to the inverter via a switchable contact; and The one or more controllers are further collectively programmed with the following instructions: The switchable contacts are caused to close when the inverter is switched to step up the voltage at the charging input to charge the rechargeable stored electrical energy source.

[0018] 7. The motor vehicle of embodiment 2, wherein the AC electric motor is a six-phase AC electric motor.

[0019] 8. The motor vehicle of embodiment 2, wherein: The instructions to switch the inverter to step up the voltage at the charging input to charge the rechargeable electrical energy source further include instructions to perform a two-phase interleaved step-up conversion.

[0020] 9. A method for controlling an electric vehicle propulsion and charging system, the method comprising: switching the inverter to provide AC propulsion energy from a rechargeable stored electrical energy source to a plurality of stator windings of an AC (alternating current) electric motor; and The inverter is switched to step up a voltage at a charging input coupled to the inverter to charge a rechargeable stored electrical energy source using at least one of the stator windings as a boost inductor.

[0021] 10. The method of embodiment 9, wherein the rechargeable source of stored electrical energy comprises a battery.

[0022] 11. The method of embodiment 10, wherein the inverter is an inverter having more than two output voltage levels.

[0023] 12. The method of embodiment 10, wherein the inverter is a two-level inverter.

[0024] 13. The method of embodiment 10, wherein: The plurality of stator windings include a first set of three-phase star-connected stator windings and a second set of three-phase star-connected stator windings, the first set of three-phase star-connected stator windings having a first neutral point and the second set of three-phase star-connected stator windings having a second neutral point; The electric vehicle propulsion and charging system further includes a switchable contact interposed between the first neutral point and the second neutral point; The method further includes causing the switchable contacts to open when the inverter is switched to provide AC propulsion energy to the plurality of stator windings from a rechargeable source of stored electrical energy; and The method further includes causing the switchable contacts to close when the inverter is switched to step up the voltage at the charging input to charge the rechargeable stored electrical energy source.

[0025] 14. The method of embodiment 10, wherein: The charging input is switchably coupled to the inverter via a switchable contact; and Wherein the method further comprises causing the switchable contacts to close when the inverter is switched to step up the voltage at the charging input to charge the rechargeable stored electrical energy source.

[0026] 15. The method of embodiment 10, wherein the AC electric motor is a six-phase AC electric motor.

[0027] 16. The method of embodiment 10, wherein: Switching the inverter to step up the voltage at the charging input to charge the rechargeable stored electrical energy source includes performing a two-phase interleaved step-up conversion.

[0028] 17. A motor vehicle comprising: An AC (alternating current) electric motor having a stator with a plurality of stator windings, the plurality of stator windings including a first set of three-phase star-connected stator windings having a first neutral point and a second set of three-phase star-connected stator windings having a second neutral point, the AC electric motor further including a switchable contact inserted between the first neutral point and the second neutral point; Rechargeable electrical energy storage; an inverter coupled to the rechargeable stored electrical energy source and the AC electric motor; and One or more controllers that are collectively programmed using the following instructions: causing the switchable contacts to open and switching the inverter to provide AC propulsion energy from a rechargeable stored electrical energy source to the plurality of stator windings; and The switchable contacts are caused to close and the inverter is switched to step up a voltage at a charging input coupled to the inverter using at least one of the stator windings as a boost inductor to charge a rechargeable stored electrical energy source.

[0029] 18. The motor vehicle of embodiment 17, wherein: The charging input is switchably coupled to the inverter via a second switchable contact; and The one or more controllers are further collectively programmed with the following instructions: The second switchable contact is caused to close when the inverter is switched to step up the voltage at the charging input to charge the rechargeable stored electrical energy source.

[0030] 19. The motor vehicle of embodiment 18, wherein the instructions to switch the inverter to step up the voltage at the charging input to charge the rechargeable electrical energy source further include instructions to perform a two-phase interleaved step-up conversion.

[0031] 20. The motor vehicle of embodiment 19, wherein the inverter is a two-level inverter.

[0032] The above summary of the invention does not represent every embodiment or every aspect of the present disclosure. The above features and advantages of the present disclosure and other possible features and advantages will become apparent from the following detailed description of the embodiments and best modes for implementing the present disclosure when considered in conjunction with the accompanying drawings and the appended claims. In addition, the present disclosure expressly includes combinations and sub-combinations of the elements and features presented above and above. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 An electric vehicle including an electric vehicle propulsion system is illustrated.

[0034] Figure 2 Shows Figure 1 An electric vehicle propulsion system, together with a charger for charging a traction battery in the electric vehicle.

[0035] Figure 3 Illustration of switching elements in a power inverter module of an electric vehicle propulsion system.

[0036] Figure 4 The diagram illustrates stator windings of an electric motor that may be used in an electric vehicle propulsion system.

[0037] Figure 5 The diagram shows the mutual winding directions of two stator windings in the stator winding.

[0038] Figure 6 Diagram showing the connections between the battery charger and power inverter modules of an electric vehicle propulsion system.

[0039] Figure 7 An equivalent circuit for charging a traction battery of an electric vehicle propulsion system using a battery charger is shown.

[0040] Figure 8 A six-phase electric motor is shown.

[0041] Fig. 9 An equivalent circuit for charging a traction battery of an electric vehicle propulsion system is shown if a six-phase motor is used in the electric vehicle propulsion system.

[0042] Fig.10 Two three-phase electric motors are shown.

[0043] Fig.11 An electric vehicle propulsion system having a two-level power inverter module with a traction battery and a battery charger connected thereto is illustrated. DETAILED DESCRIPTION

[0044] The present disclosure allows for embodiments in many different forms. Representative examples of the present disclosure are shown in the accompanying drawings and are described in detail herein as non-limiting examples of the disclosed principles. For this reason, elements and limitations described in the abstract, introduction, summary, and detailed description, but not explicitly set forth in the claims, should not be incorporated into the claims individually or collectively by implication, inference, or otherwise.

[0045] For the purposes of this description, unless specifically disavowed, the use of the singular includes the plural, and vice versa, the terms "and" and "or" shall be both conjunctive and disjunctive, "any" and "all" shall mean both "any and all", and the words "include", "comprising", "including", "having", etc. shall mean "including but not limited to". In addition, approximate words (such as "approximately", "almost", "substantially", "substantially", "approximately", etc.) may be used herein in the sense of "at, close to, or nearly at", or "within 0-5% of...", or "within acceptable manufacturing tolerance", or their logical combinations.

[0046] First reference Figure 1 , an electric vehicle 10 is illustrated. The electric vehicle 10 may be a vehicle that uses an electric motor for at least a portion of vehicle propulsion, and may be an all-electric or hybrid electric vehicle. In addition, the electric vehicle 10 may be any type of vehicle, such as a car, truck, sport utility vehicle (SUV), motorcycle, bicycle, all-terrain vehicle, etc. The electric vehicle 10 includes an electric propulsion system 12.

[0047] Additional references Figure 2 , the electric propulsion system 12 may include a rechargeable energy storage system (RESS) 15, which may include a rechargeable electrical energy source such as a traction battery 16, and a battery management system (BMS) 17 for managing the traction battery 16 (including its charging). The traction battery 16 may include one or more batteries or battery cells. The electric propulsion system 12 may also include a power inverter module (PIM) 18, an electronic control unit (ECU) 20, and an electric motor 22, and the power inverter module 18 (PIM) may be a voltage inverter. The electric motor 22 may be a motor that provides traction power for the propulsion of the electric vehicle 10. The electric motor 22 may be a three-phase AC motor. The electric motor 22 may be, for example, a permanent magnet motor (and further, a permanent magnet synchronous motor) or an induction motor.

[0048] The charging of the traction battery 16 may be via coupling the RESS 15 to a battery charger 24, such as a direct current (DC) charger, which may be a DC fast charger. If the battery charger 24 has a nominal voltage output that is the same as the nominal voltage of the traction battery 16, the battery charger 24 may be directly coupled to the RESS 15 through the closure of the switchable contacts 25 and 26. As an example of this scenario, the traction battery 16 may have a nominal voltage of 800V, and the battery charger 24 may have a nominal output voltage of 800Vdc.

[0049] Additional references Figure 3 , the power inverter module 18 may include 18 switching elements, namely switching element 28A, switching element 28B, switching element 28C, switching element 28D, switching element 28E, switching element 28F, switching element 28G, switching element 28H, switching element 28I, switching element 28J, switching element 28K, switching element 28L, switching element 28M, switching element 28N, switching element 28O, switching element 28P, switching element 28Q and switching element 28R, which may also be collectively referred to as switching elements 28A-28R below. The switching elements 28A-28R may have various technologies for the purposes of the present disclosure, including insulated gate bipolar transistors (IGBTs) and field effect transistors (FETs). The power inverter module 18 may also include a DC link capacitor 29.

[0050] The power inverter module 18 may be a multi-level inverter connected across two voltage rails (positive rail 33 and negative rail 35). Figure 3 In the example of the power inverter module 18, the voltage between the positive rail 33 and the negative rail 35, that is, the voltage of the traction battery 16, can be 800 volts DC. The power inverter module 18 can have 6 outputs - output A1, output A2, output B1, output B2, output C1 and output C2, each of which is coupled to the electric motor 22. Because the power inverter module 18 can be a three-level inverter, each of the outputs A1, output A2, output B1, output B2, output C1 and output C2 can assume one of the following three voltage states: the voltage of the positive rail 33, the voltage of the negative rail 35, and the voltage midway between the voltages of the positive rail 33 and the negative rail 35.

[0051] Additional references Figure 4 , the electric motor 22 may be a three-phase motor whose stator 14 has three pairs of stator windings, one pair of stator windings for each phase. Thus, stator winding 30 and stator winding 32 may be used for one phase (e.g., referred to as phase A of the electric motor 22). Stator winding 34 and stator winding 36 may be used for phase B of the electric motor 22, and stator winding 38 and stator winding 40 may be used for phase C of the electric motor 22. As illustrated, stator winding 30 may be coupled to output A1 of the power inverter module 18, stator winding 32 may be coupled to output A2, stator winding 34 may be coupled to output B1, stator winding 36 may be coupled to output B2, stator winding 38 may be coupled to output C1, and stator winding 40 may be coupled to output C2. Each pair of stator windings of a phase (such as stator winding 30 and stator winding 32 of phase A) can be wound in anti-parallel with respect to each other within the stator 23 of the electric motor 22, such as Figure 5As shown. Stator winding 30, stator winding 34 and stator winding 38 may include a set of star-connected stator windings having a neutral point 58. Stator winding 32, stator winding 36 and stator winding 40 may include a set of star-connected stator windings having a neutral point 60. During operation of electric motor 22, neutral point 58 and neutral point 60 may be electrically isolated from each other. When traction battery 16 is to be charged by battery charger 24, neutral point 58 and neutral point 60 may be connected by a switchable contact 57 of a contactor, the output of which is significantly lower than 800 Vdc, such as 400 Vdc. Switchable contact 57 may be disconnected in other circumstances.

[0052] An electronic control unit (ECU) 20 may control the switching of the switching elements 28A-28R for the purpose of controlling and providing voltage to the electric motor 22. In other words, the electronic control unit 20 may switch the power inverter module 18 (and / or supervise the switching of the power inverter module 18) to provide alternating current (AC) propulsion energy from the traction battery 16 to the stator windings of the electric motor 22. The electronic control unit 20 is understood to have suitable electronic resources (microprocessors, software, memory, inputs, outputs, etc.) to perform the functions attributed to the electronic control unit 20 herein. The electronic control unit 20 may be a stand-alone controller, may be integrated with the power inverter module 18, or may be integrated with other controllers in the electrical system of the electric vehicle 10 including the propulsion system 12. The electronic control unit 20 may also be networked with other controllers in the electrical system of the electric vehicle 10 and share the responsibility for performing the functions laid out herein. The controllers described in the present disclosure may operate in response to "instructions", each of which should be understood to include one or more software operations; each instruction may further include or include other or additional instructions.

[0053] Recall that the stator winding pairs for each phase (e.g., stator winding 30 and stator winding 32 of phase A) are wound in anti-parallel with respect to each other. However, given the three-level nature of the power inverter module 18, the stator winding 30 and stator winding 32 can be excited by nodes A1 and A2 having voltage pulses of opposite polarity. As such, due to the anti-parallel winding of the stator winding 30 and the stator winding 32, the magnetic fields generated by each of the stator winding 30 and the stator winding 32 will enhance each other, rather than cancel each other (this is also true for stator winding 34 and stator winding 36 (phase B) and stator winding 38 and stator winding 40 (phase C)). Using a multi-level inverter such as the power inverter module 18 allows opposite voltage polarities to be provided to the stator winding pairs in each phase as a method of eliminating or partially eliminating the dv / dt associated with switching the stator windings and reducing electrical noise.

[0054] In charging the traction battery 16 of the electric vehicle 10, using a DC fast charger can advantageously provide a fast charging process. However, although the traction battery 16 can be an 800V battery, there may be conventional DC chargers designed to charge at significantly less than 800Vdc, such as at 400Vdc. In order to allow a 400Vdc charger to charge an 800V battery, the power inverter module 18 and the stator windings of the electric motor 22 can be advantageously used.

[0055] The process of charging an 800V traction battery using a 400Vdc charger may begin with parking the electric motor, with phase A of the electric motor 22 aligned with the d-axis of the electric motor 22. In field oriented control of an AC motor, the "d-axis" is the non-torque producing axis of the AC electric motor, as opposed to the "q-axis." Parking the electric motor 22 in this manner reduces the likelihood that passing charging current through phase A (as described herein before) will tend to generate torque in the electric motor 22 unnecessarily. In field oriented control, the rotational position of the rotor of the electric motor under control is sensed or inferred, and is therefore known.

[0056] Now additionally refer to Figure 6 If charging is performed using a battery charger 24 having an output significantly less than 800 Vdc (e.g., 400 Vdc), the 400 Vdc output of the battery charger 24 may be connected across a charging port 80 and a charging port 82 provided in the propulsion system 12, thereby coupling the charging port 80 (which may be referred to as a charging input) to the power inverter module 18. In addition, the switchable contact portion 25 ( Figure 2 ) can be opened. Additionally, the switchable contact 84 can be turned on (i.e., closed) to couple the positive output of the battery charger 24 to the stator winding 32 of the electric motor 22 (one of the stator windings of phase A of the electric motor 22). Still further, the switchable contact 57 ( Figure 4 ) can be closed to couple the neutral point 58 and the neutral point 60 of the stator winding of the electric motor 22 together. It is further assumed that all switching elements (switching element 28A, switching element 28B, switching element 28C, switching element 28D, switching element 28E and switching element 28F) of phase A of the power inverter module 18 remain turned off (i.e., disconnected). Additionally, it is assumed that switching element 28I, switching element 28J, switching element 28K and switching element 28L of phase B of the power inverter module 18 remain turned off (i.e., disconnected). Finally, it is assumed that all switching elements (switching element 28M, switching element 28N, switching element 28O, switching element 28P, switching element 28Q and switching element 28R) of phase C remain turned off (i.e., disconnected). Reference Figure 7An equivalent circuit is shown which illustrates the topology of the boost converter thus created. Switching elements 28G and 28H (at Figure 7 10 ) can then operate with stator windings 32 and 34 as an inductive boost converter to convert the 400 Vdc output from battery charger 24 to 800 Vdc for charging traction battery 16. Switching elements 28G and 28H can be pulse width modulation (PWM) controlled to perform the boost conversion in any manner performed in the art of DC-DC power conversion. Control of the boost conversion can be performed by electronic control unit 20 or by another electronic controller in the electrical system of electric vehicle 10. Appropriate feedback will be provided to the controller managing the boost conversion. In addition, control of switchable contacts 57 and switchable contacts 84 can be performed by electronic control unit 20 or by another electronic controller in the electrical system of electric vehicle 10, which is informed by an appropriate signal of the upcoming 400 Vdc charge.

[0057] As described herein, the power inverter module 18 is switched to step up (or up-convert or boost) the voltage from the battery charger 24 coupled to the power inverter module 18 to charge the traction battery 16 .

[0058] As an alternative, two-phase interleaved control of the voltage boost process can be implemented. Figure 7 The topology of FIG. 1 is similar to that of FIG. 2 , but additionally, instead of switching element 28M and switching element 28N remaining off (i.e., disconnected), they can work together with stator winding 38 to additionally perform a boost conversion. Control of the boost conversion including switching element 28G, switching element 28H, and stator winding 34 can be interleaved (i.e., phase-shifted relative to) with the boost conversion including switching element 28M, switching element 28N, and stator winding 38. In this way, the boost conversion process can be two-phase, with the two phases interleaved, resulting in less voltage ripple at the output of the boost conversion process and higher efficiency.

[0059] Alternatively, multiple switchable contacts - switchable contact 84, switchable contact 86 and switchable contact 88 ( Figure 2 ). The switchable contact 84, switchable contact 86, or switchable contact 88 in the phase most closely aligned with the d-axis of the electric motor 22 can be closed (i.e., turned on), wherein the other switchable contacts of the switchable contact 84, switchable contact 86, and switchable contact 88 remain open (i.e., turned off). The voltage step-up conversion can then be performed as described before.

[0060] For additional clarity, it is noted that during normal operation of the electric motor 22, that is, when the electric motor 22 is used to propel the electric vehicle 10 using switched AC propulsion energy provided by the power inverter module 18 from the traction battery 16, the switchable contacts 25, 26, 57, 84, 86, and 88 may all be off (i.e., open). The switchable contacts 25, 26, 57, 84, 86, and 88 may be controlled by the ECU 20, by other controller(s) in the electrical system of the electric vehicle 10, or by a combination of controllers in the networked electrical system of the electric vehicle 10. The switchable contacts may also be switches that are opened and closed manually, or by physical actions (such as the physical action of plugging / unplugging the propulsion system 12 into / from a battery charger).

[0061] Consider alternative scenarios. Figure 8 , in which a six-phase AC electric motor 100 is shown. Here, all six stator windings—stator winding 102, stator winding 104, stator winding 106, stator winding 108, stator winding 110, and stator winding 112—are coupled to a common neutral point 114 within the electric motor 100 (i.e., connected in a star configuration). If the terminals of the electric motor 100 are coupled to the corresponding outputs of the power inverter module 18, the switching elements 28G and 28H of the power inverter module 18 can be used to perform voltage step-up conversion. Switching element 28A, switching element 28B, switching element 28C, switching element 28D, switching element 28E, switching element 28F, switching element 28K, switching element 28L, switching element 28M, switching element 28N, switching element 28O, switching element 28P, switching element 28Q, and switching element 28R can remain off (i.e., disconnected). Furthermore, switching element 28I and switching element 28J may remain on (i.e., closed), effectively connecting stator winding 106 and stator winding 108 in parallel. Under the above conditions and with the 400 Vdc output from battery charger 24 coupled across charging port 80 and charging port 82, the equivalent circuit would be as follows: Fig. 9 The voltage step-up conversion may be performed via PWM control of the switching element 28G and the switching element 28H.

[0062] As a pair Fig. 9As an enhancement to the illustrated scenario, switching element 280 and switching element 28P may remain on (i.e., closed), effectively connecting stator winding 110 and stator winding 112 in parallel. Switching element 28M and switching element 28N may be pulse width modulated controlled in an interleaved manner under the control of switching element 28E and switching element 28F to generate a two-phase interleaved step-up output to charge traction battery 16.

[0063] As an alternative, consider Fig.10 Here, if the power inverter module 18 is used to control the propulsion of two three-phase electric motors 200 and 250, where the terminals of the electric motor 200 and the terminals of the electric motor 250 are coupled to their corresponding outputs of the power inverter module 18, the electric motor 200 and the electric motor 250 can be used together in the voltage step-up conversion process using the principles disclosed herein.

[0064] As a further alternative, consider Fig.11 Here, a two-level inverter 300 can provide a switched voltage from a traction battery 302 to an electric motor 306. "Two-level" means that the output of the inverter 300 can take on one of two voltage values, namely the voltage of a positive rail 350 (in this example, say at 800 Vdc) or the voltage of a negative rail 352 at zero volts (i.e., -800 Vdc relative to the positive rail 350).

[0065] The nominal voltage of traction battery 302 may be 800 volts. Traction battery 302 may be included in a battery management system that oversees the charging of traction battery 302. Inverter 300 may include switching element 320, switching element 322, switching element 324, switching element 326, switching element 328, and switching element 330. Inverter 300 may also include a DC link capacitor 331. Electric motor 306 may be a three-phase AC motor having stator winding 308, stator winding 309, and stator winding 310. The three stator windings may be connected at a neutral point 312 within electric motor 306. Switchable contact 340 may be disconnected under conditions in which electric motor 306 operates to provide traction power. However, if the traction battery 302 is to be charged from an energy source at a voltage significantly lower than the nominal voltage of the traction battery 302, such as the battery charger 304 (which may be a 400 Vdc fast charger in this example), the switchable contact 340 may be closed. The positive output of the battery charger 304 is then coupled to the stator winding 308. The switching elements 324 and 326 may then be PWM controlled to work in conjunction with the stator windings 308 and 310 to provide a voltage step-up conversion for charging the battery 302 at 800 Vdc. Alternatively, the switching elements 328 and 330 may work in conjunction with the stator winding 309. Still alternatively, the control of the stator windings 308 and 309 and the stator winding 310 may be performed in an interleaved manner to provide a two-phase voltage step-up (or step-up conversion, or up-conversion) for charging the battery 302.

[0066] As an alternative, the software in the ECU 20 may be capable of being updated via an over-the-air (OTA) update. In this manner, the ECU 20 may be programmed to perform the voltage up-conversion described herein from a variable DC charger voltage (other than the 400 Vdc example described herein).

[0067] An advantage of the battery charging system and method described herein is that access to the neutral point(s) of the motor is not required. This can reduce the likelihood of introducing electrical noise into the system. However, on the other hand, access to the neutral point can provide additional possible topologies for up-conversion for charging the traction battery 16 of the propulsion system 12 of the electric vehicle 10.

[0068] Embodiments of the present disclosure are described herein. However, it is to 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 present disclosure in various ways.

[0069] Furthermore, the embodiments shown in the drawings or the features of the various embodiments mentioned in this description are not necessarily to be understood as mutually independent embodiments. On the contrary, each of the features described in one of the examples of embodiment can be combined with one or more other desired features from other embodiments, thereby obtaining other embodiments that are not described in words or with reference to the drawings. Therefore, such other embodiments fall within the framework of the scope of the attached claims.

Claims

1. A motor vehicle comprising: AC (alternating current) electric motor having a stator with a plurality of stator windings; Rechargeable electrical energy storage; an inverter coupled to the rechargeable stored electrical energy source and the AC electric motor; One or more controllers that are collectively programmed using the following instructions: switching an inverter to provide AC propulsion energy from a rechargeable stored electrical energy source to the plurality of stator windings; and The inverter is switched to step up a voltage at a charging input coupled to the inverter to charge a rechargeable stored electrical energy source using at least one of the stator windings as a boost inductor.

2. The motor vehicle of claim 1 wherein the rechargeable source of stored electrical energy comprises a battery.

3. A motor vehicle as claimed in claim 2, wherein the inverter is an inverter having more than two output voltage levels.

4. The motor vehicle of claim 2, wherein the inverter is a two-level inverter.

5. The motor vehicle of claim 2, wherein: The plurality of stator windings include a first set of three-phase star-connected stator windings and a second set of three-phase star-connected stator windings, the first set of three-phase star-connected stator windings having a first neutral point and the second set of three-phase star-connected stator windings having a second neutral point; The AC electric motor vehicle further includes a switchable contact interposed between the first neutral point and the second neutral point; and The one or more controllers are further collectively programmed with the following instructions: causing the switchable contacts to open when the inverter is switched to provide AC propulsion energy from the rechargeable stored electrical energy source to the plurality of stator windings; as well as The switchable contacts are caused to close when the inverter is switched to step up the voltage at the charging input to charge the rechargeable stored electrical energy source.

6. The motor vehicle of claim 2, wherein: The charging input is switchably coupled to the inverter via a switchable contact; as well as The one or more controllers are further collectively programmed with the following instructions: The switchable contacts are caused to close when the inverter is switched to step up the voltage at the charging input to charge the rechargeable stored electrical energy source.

7. The motor vehicle of claim 2, wherein the AC electric motor is a six-phase AC electric motor.

8. The motor vehicle of claim 2, wherein: The instructions to switch the inverter to step up the voltage at the charging input to charge the rechargeable electrical energy source further include instructions to perform a two-phase interleaved step-up conversion.

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