DE102008034670B4 - AUTOMOTIVE POWER SYSTEM AND DOUBLE-SIDED INVERTER SYSTEM WITH ISOLATED NEUTRAL POINT TOPOLOGY - Google Patents

Abstract

Motor vehicle propulsion system comprising:a four-phase motor (20) having a first set of windings (36) and a second set of windings (37), the first set of windings (36) and the second set of windings (37) electrically insulating are;a first inverter (38) coupled to the first set of windings (36); anda second inverter (40) coupled to the second set of windings (37);the first set of windings (36) being connected to provide a first neutral point (39), and the second set of windings (37 ) is connected to create a second neutral point (41);wherein the first neutral point (39) is coupled to the first inverter (38) and the second neutral point (41) is coupled to the second inverter (40);wherein the first set of Windings (36) comprise a first two-phase winding structure (a, b) and the second set of windings (37) comprise a second two-phase winding structure (c, d).

Description

TECHNICAL FIELD

Embodiments of the subject matter described herein generally relate to vehicle propulsion systems, and more particularly, embodiments of the subject matter relate to motor vehicle propulsion systems having a double-sided inverter system.

BACKGROUND

In recent years, technological advances and evolving styles have led to significant changes in automotive design. One of the changes concerns the power usage and complexity of the various electrical systems in automobiles, especially in alternative fuel vehicles such as hybrid, electric and fuel cell vehicles.

Many of the electrical components comprising the electric motors used in such vehicles receive electrical power from alternating current (AC) power supplies. However, the power sources used in such applications (e.g. batteries) only provide direct current (DC) power. Consequently, to convert DC power to AC power, devices known as "inverters/rectifiers" are used, which often use multiple switches or transistors operated at different intervals to convert the DC power to AC power .

In addition, such vehicles, especially fuel cell vehicles, often use two separate voltage sources (e.g. a battery and a fuel cell) to supply power to the electric motors that drive the wheels. “Power converters,” such as direct current-to-direct current (DC/DC) converters, are typically used to transfer power from the two voltage sources. Modern DC/DC converters often include transistors that are electrically connected by an inductor. By controlling the states of the various transistors, a desired average current can be impressed through the inductance and thus control the power flow between the two voltage sources.

The use of both an inverter/rectifier, hereinafter referred to as an inverter, and a power converter significantly increases the complexity of the motor vehicle's electrical system. The additional components required for both types of devices also increase the overall cost and weight of the vehicle. Accordingly, systems and methods have been developed to operate a motor coupled to multiple power sources without a DC/DC converter, maximizing motor performance through use of dual electrical inverter systems.

Prior art systems are limited to three-phase motor concepts traditionally used in automobiles.

The design of many of these systems requires that the two energy sources have essentially the same voltage level. Additionally, in a situation where one of the sources fails for some reason (i.e., extremely cold temperatures), prior art designs may not permit operating an engine using only the other source.

Accordingly, it is desirable to provide a dual inverter system to enable the use of power sources with different operating characteristics to enable cold starting of a vehicle in the event of a failure of one of the power sources. Other desirable features and characteristics of the present invention will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.

The publication DE 10 2005 026 779 A1 discloses an electric drive device with a multi-phase motor controlled by a plurality of control means, the motor consisting of a common rotor with sub-machines in the form of sub-stators.

In print US 5,099,186 A discloses an integrated motor drive system and recharging system in which two three-phase motors or a motor with two sets of windings are powered from a DC source by two inverters, and the DC source is charged during charging by single-phase power from neutral points of the motor(s).

The object of the invention is to provide a dual inverter system to enable the use of energy sources with different operating characteristics to enable a cold start of a vehicle in the event of a failure of one of the energy sources.

This object is achieved by the motor vehicle drive system according to claim 1 and the inverter system according to claim 10. Advantageous developments of the invention are described in the subclaims.

BRIEF DESCRIPTION OF DRAWINGS

• 1 ist eine schematische Ansicht eines beispielhaften Kraftfahrzeugs gemäß einer Ausführungsform;
• 2 ist eine schematische Ansicht eines doppelseitigen Wechselrichtersystems gemäß einer Ausführungsform;
• 3 ist eine schematische Ansicht einer Statorwicklungsstruktur für einen Motor zur Verwendung in dem doppelseitigen Wechselrichtersystem von 2 gemäß einer Ausführungsform;
• 4 ist ein Graph von Motorphasenströmen gemäß einer Ausführungsform;
• 5 ist eine schematische Ansicht eines Steuerungssystems zum Betreiben des doppelseitigen Wechselrichtersystems von 2 gemäß einer Ausführungsform.

A better understanding of the subject matter may be achieved by reference to the detailed description and claims in conjunction with the following figures, in which like reference numerals designate similar elements throughout the various figures.

• 1 is a schematic view of an exemplary motor vehicle according to an embodiment;
• 2 is a schematic view of a double-sided inverter system according to an embodiment;
• 3 is a schematic view of a stator winding structure for a motor for use in the double-sided inverter system of 2 according to one embodiment;
• 4 is a graph of motor phase currents according to an embodiment;
• 5 is a schematic view of a control system for operating the double-sided inverter system of 2 according to one embodiment.

PRECISE DESCRIPTION

The following detailed description is purely illustrative in nature and is not intended to limit the embodiments of the subject matter or the applications and uses of such embodiments. As used herein, the word “exemplary” means “serving as an example, instance or illustration.” Any implementation described herein as an example is not necessarily to be viewed as preferred or advantageous over other implementations. Furthermore, there is no intention to be bound by any theory, explicit or implicit, presented in the foregoing technical field, background, summary, or detailed description that follows.

The following description refers to elements or nodes or features that are “connected” or “coupled” to one another. As used herein, unless expressly stated otherwise, “connected” means that one element/node/feature is directly connected to (or in direct communication with) another element/node/feature, not necessarily mechanically. Likewise, unless expressly stated otherwise, “coupled” means that one element/node/feature is directly or indirectly connected to (or communicates directly or indirectly with) another element/node/feature, not necessarily mechanically. Thus, although the schematic illustrations shown herein illustrate exemplary arrangements of elements, additional intervening elements, devices, features, or components may be present in an embodiment of the illustrated subject matter. The terms “first,” “second,” or other such numerical terms denoting structures do not imply any sequence or order unless clearly indicated by the context.

1 illustrates a vehicle or motor vehicle 10 according to an embodiment of the present invention. The motor vehicle 10 includes a chassis 12, a body 14, four wheels 16, and an electronic control system 18. The body 14 is arranged on the chassis 12 and essentially envelops the other components of the motor vehicle 10. The body 14 and the chassis 12 can form a framework together. The wheels 16 are each rotatably coupled to the chassis 12 near a respective corner of the body 14.

The motor vehicle 10 may be any of a number of different types of motor vehicles, such as a sedan, station wagon, truck, or sport utility vehicle (SUV), and may be two-wheel drive (2WD) (i.e., rear-wheel drive or front-wheel drive). ), be a four-wheel drive (4WD) or an all-wheel drive (AWD). The motor vehicle 10 may also include any or a combination of a number of different types of engines, such as a gasoline or diesel-powered internal combustion engine, a Flex Fuel Vehicle (FFV) engine (i.e., the a mixture of gasoline and alcohol is used), a machine powered by a gaseous mixture (e.g. hydrogen and natural gas), a hybrid internal combustion engine/electric motor machine, and an electric motor.

At the in 1 In the exemplary embodiment illustrated, the motor vehicle 10 further includes a motor 20 (ie, an electric motor/generator, drive motor, etc.), a first power source 22, a second power source 24, an inverter assembly 26, and a radiator 28. The radiator 28 is attached to the frame connected to an outer portion thereof and, although not illustrated in detail, includes a plurality of cooling channels containing a cooling fluid (ie, coolant), such as water and/or ethylene glycol (ie, “antifreeze”), and is coupled to the inverter assembly 26 and the motor 20. In one embodiment, the inverter assembly 26 receives coolant and shares it with the electric motor 20. As in 1 As shown, the engine 20 may also include a transmission integrated therein such that the engine 20 and the transmission are mechanically coupled to at least some of the wheels 16 through one or more drive shafts 30.

As shown, the first energy source 22 and the second energy source 24 are in operative communication with and/or electrically coupled to the electronic control system 18 and the inverter assembly 26. Although not illustrated, the first power source 22 and the second power source 24 may vary depending on the embodiment and may be of the same type or different types. In one or more embodiments, the first power source 22 and the second power source 24 may each include a battery, a fuel cell, an ultracapacitor, or another suitable voltage source. A battery may be any type of battery suitable for use in a desired application, such as a lead-acid battery, a lithium-ion battery, a nickel-metal battery, or another rechargeable battery. An ultracapacitor can be a supercapacitor, a
electrochemical double layer capacitor or any other high energy density electrochemical capacitor suitable for a desired application.

Now with reference to 1 and 2 A double-sided inverter system 32 may be designed to drive a motor 20 that has more than three phases, according to one embodiment. The double-sided inverter system 32 includes the motor 20, the first energy source 22, the second energy source 24, the inverter assembly 26 and a controller 34.

The motor 20 is a polyphase alternating current (AC) motor and includes a first set of windings 36 (or coils) and a second set of windings 37, each winding corresponding to a phase of the motor 20. Although not illustrated, the motor 20 includes a stator assembly (which includes the coils), a rotor assembly (which includes a ferromagnetic core), and a cooling fluid (i.e., coolant), as one skilled in the art will appreciate. Motor 20 may be an induction motor, a permanent magnet motor, or any type suitable for the desired application.

In an exemplary embodiment, the motor 20 is a four-phase motor, with the first set of windings 36 and the second set of windings 37 each corresponding to electrically isolated two-phase wiring structures. It is noted that the sets of windings 36 and 37 are electrically isolated, meaning that current in each set of windings 36 and 37 can be controlled independently and may vary from the current in the other set of windings 36 and 37. The sets of windings 36 and 37 can further electromagnetically transfer energy to the other set of windings 36 and 37 using a magnetomotive force generated by the motor 20. The controller 34 may independently control the manner in which power flows from each energy source 22, 24 to achieve a desired power flow.

The use of a motor 20 that includes two electrically isolated sets of windings 36 and 37 driven by two power sources 22, 24 is desirable, particularly in a motor vehicle 10 operating in a hybrid/electric mode, because it provides improved provides reliability. For example, if a first power source 22, such as a battery, in a motor vehicle 10 fails for any reason (i.e., cold or inclement weather), the engine 20 may still be started and powered independently by the second power source 24, as discussed in more detail below.

Now with reference to 2 and 3 In an exemplary embodiment, the first set of windings 36 includes a first phase (a) and a second phase (b). In an exemplary embodiment, the spatial offset between the first phase (a) and the second phase (b) is such that the electrical angle between the first phase and the second phase is 90° as shown. In an exemplary embodiment, the two phases are connected to create a first neutral point 39 in the motor 20. In an exemplary embodiment, the spatial offset between the first phase (a) and the second phase (b) is adjusted to maintain an electrical angle of 90° in the stator frame. It is known in the art that maintaining a 90° electrical angle results in the generation of uniform torque in the motor 20 in response to balanced two-phase current excitation.

Now up 4 By reference, providing currents to the first phase (i _a ) and the second phase (i _b ), which are 90° out of phase in the time domain, results in a uniformly rotating magnetic field. This is shown by the current flowing to the first neutral point 39 (i- _{ab_n} ), which is a sum of the two phase currents (i _a and i _b ).

Regarding 2 and 3 the second set of windings 37 includes a third phase (c) and a fourth phase (d). For the same reasons as disclosed above, in an exemplary embodiment, the spatial offset between the third phase (c) and the fourth phase (d) is such that the electrical angle between the third phase and the fourth phase is 90°. Additionally, the spatial offset between the two sets of windings 36 and 37 may vary depending on the design, as shown in 3 is shown by the symbol θ. In an exemplary embodiment, the spatial offset θ is also 90°, as in 2 is shown. Although 3 4 illustrates windings 36 and 37 with a concentrated winding structure, the concepts and principles discussed herein can be extended to a distributed winding structure.

Additionally, those skilled in the art will find that a multi-phase motor 20 can provide additional advantages over a conventional machine with fewer phases (i.e., three-phase) depending on the spatial offset of the two sets of windings 36 and 37 in the stator. For example, varying the spatial offset between the two sets of windings 36 and 37 can reduce or eliminate air gap flow harmonics and corresponding torque harmonics and rotor copper losses generated by these air flow harmonics. The spatial offset of the windings 36 and 37 and the phase connections can be varied to suit a desired application. In an exemplary embodiment, the fundamental frequencies of the two inverters 38 and 40 are the same, resulting in a more sinusoidal field distribution and current.

Up again 2 By reference, the inverter assembly 26 includes a first inverter 38 and a second inverter 40, each including six switches (eg, semiconductor devices such as transistors and/or switches) with anti-parallel diodes (ie, anti-parallel to each switch). As shown, the switches in inverters 38 and 40 are arranged in three pairs (or legs), with pairs 42, 44 and 46 located in the first inverter 38 and pairs 48, 50 and 52 located in the second inverter 40 .

In an exemplary embodiment, the first phase (a) of the first set of windings 36 of the motor 20 is electrically connected at opposite ends thereof between the switches of the switch pair 42 in the first inverter 38 and the second phase (b) to the first neutral point 39. The second phase (b) of the first set of windings 36 is connected between the switches of the pair 44 in the first inverter 38 and the first neutral point 39 as shown. The first neutral point 39 is connected between the switches of the pair 46. Similarly, the two phases (c, d) of the second set of windings 37 may be connected between the switches of pairs 48, 50 and 52 and a second neutral point 41 as shown. Additionally, in an alternative embodiment, the negative bus of the two energy sources 22, 24 may also be connected to create a common negative point (not shown).

In this configuration, since the power sources 22, 24 are electrically isolated, power sources 22, 24 with different voltage levels, power ratings, operating characteristics, etc. can be used simultaneously. This is particularly advantageous in comparison with other inverter systems where, for practical reasons, it is necessary that the energy sources 22, 24 are almost identical. For example, in this case, a high voltage source (≥100V), such as a fuel cell, may be used simultaneously with a 12V battery to drive the motor 20.

Still with reference to 2 The double-sided inverter system 32 may also include first and second capacitors 54 and 56 each connected in parallel with the first and second power sources 22, 24 to smooth out residual current ripple during operation. The controller 34 is in operative communication with and/or electrically connected to the first and second inverters 38 and 40. The controller 34 is responsive to commands received from the driver of the motor vehicle 10 (ie, via an accelerator pedal) and provides commands to the first inverter 38 and the second inverter 40 to control the output of the inverters 38 and 40, as described to control.

Again with reference to 1 The electronic control system 18 is in operative communication with the engine 20, the first power source 22, the second power source 24 and the inverter assembly 26. Although not shown in detail, the electronic control system 18 may include various sensors and automotive control modules or electronic control units (ECUs). , such as an inverter control module (i.e. the in 2 controller 34 shown) and a vehicle controller, and at least one processor and/or a memory comprising instructions stored therein (or in another computer-readable medium) to perform the pro processes and procedures as described below.

In operation, the motor vehicle 10 is operated by providing power to the wheels 16 with the electric motor 20, which receives power from the first energy source 22 and the second energy source 24 alternately and/or from the first energy source 22 and the second energy source 24 simultaneously. To power the motor 20, DC power is supplied from the first power source 22 and the second power source 24 to the first and second inverters 38 and 40, respectively, which convert the DC power to AC power, as in the art is generally understood. The first and second inverters 38 and 40 generate AC voltages on the windings 36 and 37 (or phases). As is generally understood, the voltages required across windings 36 and 37 of motor 20 depend on speed, commanded torque (i.e., commanded synchronous frame currents), and other motor parameters.

5 illustrates a control system 60 for operating a motor 20 in a double-sided inverter system 32 using the principles described above according to one embodiment. Radio frequency pulse width modulation (PWM) may be applied by the controller 34 to modulate and control the inverters 38 and 40 and to manage the voltage generated by the inverters 38 and 40. The control system 60 includes first and second PWM blocks 68 and 70 and the double-sided inverter system 32.

The controller 34 provides a control algorithm that achieves a desired power flow between the first and second energy sources 22, 24 while generating the commanded torque in the motor 20. Although not shown, the control system 60 receives a torque command for the motor 20, from which the controller 34 receives power commands for the first power source 22 (and/or the first inverter 38) and the second power source 24 (and/or the second inverter 40 ) and synchronous frame currents for the windings 36 and 37 in the motor 20 can be determined.

When the engine 20 does not require the maximum power output of an energy source 22 or 24, the additional power from the energy source 22 or 24 can be used to charge the other energy source 22 or 24. For purposes of illustration and brevity, it will be discussed that the first energy source 22 generates excess power to charge the second energy source 24, but those skilled in the art will recognize that numerous alternative target power flows are possible and this distinction is not limiting but is made for indicative purposes only.

Now with reference to 5 The controller 34 may supply the first and second PWM blocks 68 and 70 with modulation voltage signals v ₁ * and v ₂ *. The PWM blocks 68 and 70 can generate PWM signals to operate the switches in the first and second inverters 38 and 40 to cause the desired output voltages to be applied to the windings 36 and 37 to power the motor 20 with the required Torque to operate. According to one embodiment, the controller 34 may be configured to determine the operating mode. In one operating mode, the first energy source 22 can independently provide the power required by the motor 20. In another operating mode, the maximum power output of the first energy source 22 may be less than the power required by the motor 20. If the engine 20 requires power from the first energy source 22 as well as power from the second energy source 24, the controller 34 may be configured to control a power flow from the second energy source 24 to the engine 20 in combination with the first energy source 22 by double-sided inverter system 32 is modulated.

In another mode of operation, the first energy source 22 may have the ability to provide an excess amount of power (ie, reserve power) in addition to the power required by the engine 20 to produce a commanded torque. The excess power may be supplied to and stored by the second voltage source 24, and may be due to the in 2 indicated current flow directions shown can be viewed as a negative DC current in the voltage bus of the second voltage source 24. The reserve power can be understood to be the difference between the power required by the engine 20 and the maximum power output of the first energy source 22. The controller 34 may modulate the double-sided inverter system 32 to enable electromagnetic charging of the second energy source 24 using the magnetomotive force of the motor 20. In a further embodiment, the controller 34 can be designed so that it enables electromagnetic charging of both energy sources 22, 24 in a further operating mode.

In a third mode of operation, the first power source 22 may fail for any reason (ie, cold temperatures or harsh weather). In an exemplary embodiment, the second energy source 24 may be designed to operate in harsh weather or cold temperatures. For example, a lithium-ion battery operating at cold temperatures may be selected as the second power source 24, while the first power source 22 may be a conventional lead-acid battery. The controller 34 may detect the inability of the first energy source 22 to provide power and control power flow from the second energy source 24 to the motor 20 by modulating the double-sided inverter system 32 to produce an effective neutral point of the motor 20.

Many combinations of voltages on the windings 36 and 37 can produce the required torque in the motor 20 and achieve a desired power flow to (or from) the energy sources 22, 24 and the motor 20. An optimal operating point determines the modulation voltage at the terminals of the inverters 38 and 40. Those skilled in the art will note that conditions for determining an optimal operating point are left to the designer and depending on the application for which the motor 20 is used, along with the types chosen the energy sources 22, 24 will vary. Those skilled in the art will appreciate that the control system 60 may be further modified to include appropriate feedback signals and other methods known in the art to control the inverters 38 and 40, which are not within the scope of this disclosure.

An advantage of the system and/or method described above is that the electrical system used to power the motor 20 through two separate power sources 22, 24 is significantly simplified as a conventional DC /DC power converter is not required. Using the configuration described above opens up the possibility of using two energy sources 22, 24 with different voltage levels and operating characteristics. Additionally, in a situation where one of the sources 22, 24 is unavailable for some reason (i.e., extremely cold temperatures), the double-sided inverter system 32 allows an engine 20 to be operated or a motor vehicle 10 to be cold-started using only one power source 22, 24 However, as described above, the performance of the motor 20 is not compromised because the commanded torque can still be produced in the motor 20, allowing excess power to flow between the power sources 22, 24.

Other embodiments may use the system and method described above on different types of automobiles, different vehicles (e.g., watercraft and aircraft), or on different electrical systems overall, as it can be implemented in any situation where the voltages of the two sources dynamically change over a wide range. The motor 20 and inverters 38 and 40 may have other phase numbers and the systems described herein should not be construed as being limited to a four-phase design. Other forms of energy sources 22, 24, such as power sources, and loads may be used, including diode rectifiers, thyristor converters, fuel cells, inductors, capacitors, and/or any combination thereof.

For brevity, conventional techniques relating to signal processing, data transmission, signaling, network control, and other functional aspects of the systems (and the individual operating components of the systems) may not be described in detail herein. In addition, the connecting lines shown in the various figures included herein are intended to illustrate exemplary functional relationships and/or physical couplings between the various elements. It is noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the subject matter.

Claims (14)

Motor vehicle propulsion system comprising: a four-phase motor (20) having a first set of windings (36) and a second set of windings (37), the first set of windings (36) and the second set of windings (37) electrically insulating are; a first inverter (38) coupled to the first set of windings (36); and a second inverter (40) coupled to the second set of windings (37); wherein the first set of windings (36) are connected to create a first neutral point (39) and the second set of windings (37) are connected to create a second neutral point (41); wherein the first neutral point (39) is coupled to the first inverter (38) and the second neutral point (41) to the second inverter (40); wherein the first set of windings (36) comprises a first two-phase winding structure (a, b) and the second set of windings (37) comprises a second two-phase winding structure (c, d). Motor vehicle drive system Claim 1 , wherein the first set of windings (36) comprises a first phase (a) and a second phase (b), the first phase (a) and the second phase (b) having a first spatial offset, each with a different Leg (42, 44) of the first inverter (38) is coupled. Motor vehicle drive system Claim 2 , wherein the first spatial offset between the first phase (a) and the second phase (b) generates an electrical angle of 90 ° between a third phase (c) and a fourth phase (d). Motor vehicle drive system Claim 3 , wherein the second set of windings (37) comprises the third phase (c) and the fourth phase (d), the third phase (c) and the fourth phase (d) having a second spatial offset, each with a different Leg (48, 50) of the second inverter (40) is coupled. Motor vehicle drive system Claim 4 , wherein the second spatial offset between the third phase (c) and the fourth phase (d) produces an electrical angle of 90° between the third phase (c) and the fourth phase (d). Motor vehicle drive system Claim 5 , wherein the first phase (a) and the fourth phase (d) have a third spatial offset. Motor vehicle drive system Claim 6 , where the third spatial offset between the first phase (a) and the fourth phase (d) is 90°. Motor vehicle drive system Claim 1 , further comprising a first energy source (22) coupled to the first inverter (38), the first energy source (22) being selected from a group consisting of a battery, a fuel cell and an ultracapacitor. Motor vehicle drive system Claim 8 , further comprising a second energy source (24) coupled to the second inverter (40), the second energy source (24) being selected from a group consisting of a battery, a fuel cell and an ultracapacitor. Inverter system (32) for use in a vehicle (10) with a first energy source (22) and a second energy source (24), the inverter system (32) comprising: a four-phase motor (20) having a first set of windings (36) and a second set of windings (37), the first set of windings (36) being electrically insulated from the second set of windings (37), and wherein the first Set of windings (36) comprises a first two-phase winding structure (a, b) and the second set of windings (37) comprises a second two-phase winding structure (c, d); a first inverter (38) coupled to the first power source (22) and configured to drive the motor (20), the first set of windings (36) being coupled to the first inverter (38); a second inverter (40) coupled to the second power source (24) and configured to drive the motor (20), the second set of windings (37) being coupled to the second inverter (40); wherein the first set of windings (36) are connected to create a first neutral point (39) and the second set of windings (37) are connected to create a second neutral point (41); wherein the first neutral point (39) is coupled to the first inverter (38) and the second neutral point (41) to the second inverter (40); and a controller (34) coupled to the first inverter (38) and the second inverter (40), the controller (34) being configured to control the first inverter (38) and the second inverter (40) to achieve a target power flow between the first energy source (22), the second energy source (24) and the motor (20). Inverter system (32). Claim 10 , wherein the controller (34) is designed to control a power flow from the first energy source (22) for driving the motor (20). Inverter system (32). Claim 11 , wherein the controller (34) is designed to control electromagnetic charging of the second energy source (24) by the motor (20). Inverter system (32). Claim 10 , wherein the controller (34) is configured to generate an effective neutral point of the motor (20) and to control a power flow from the second energy source (24) for driving the motor (20). Inverter system (32). Claim 13 , wherein the second energy source (24) is a lithium-ion battery.

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