Direct discrete time current controller of virtual conversion AC motor

Abstract

An electric drive system of a motor vehicle or another battery power system includes a power inverter module (PIM) connected to a DC power source, an alternating current (AC) motor connected to the PIM and a load, and a controller. The motor is a salient pole motor. The control logic of the controller includes a device model of the electric drive system. The equipment model includes asymmetric time constants of the motor. The controller selectively corrects the asymmetric time constants via selective and independent operating point-specific manipulation of direct-axis (d-axis) and quadrature-axis (q-axis) inductances and resistances. By manipulating or adding a virtual inductance term and a virtual resistance term independently and for each operating point, the asymmetric time constant is virtually converted in the control logic into a symmetric modified time constant. The controller controls the motor at the operating point using the symmetric correction time constants.

Description

[0001] introduction Background Art

[0002] When implemented as a single-phase or multi-phase alternating current (AC) motor having a rotor and a stator, the rotating electrical machine can be connected to a direct current (DC) power source via an intermediate inverter. Pulse width modulation or another high frequency switch control technique suitable for the application is used to individually command the individual on / off states of the resident semiconductor power switches of the inverter. This action ultimately converts the DC input voltage from the power source into an AC output voltage. The AC output voltage is then applied to the stator windings of the AC motor to cause rotation of the rotor and the output member connected thereto.

[0003] The motor can be constructed so that the inductance of the stator winding varies as a function of the rotor position. This is mainly due to the uneven stator-rotor air gap. Unlike higher speed symmetrical / non-salient pole motors where the stator-rotor air gap is uniform and the direct axis (d-axis) and quadrature axis (q-axis) inductance are the same, asymmetrical / salient pole motors are more commonly used in low speed applications. Interior permanent magnet (IPM) synchronous motors and synchronous reluctance motors are examples of salient pole motors. The presence of asymmetry or saliency makes the motor control task very complicated. This in turn requires the use of specialized control logic, sensing and digital signal processing techniques. Therefore, it is relatively difficult to analyze and control asymmetrical motors in real time using classical control techniques. Summary of the invention

[0004] Disclosed herein are control systems and associated methods for controlling a salient pole / asymmetric alternating current (AC) motor, such as an electric traction motor of an electrified powertrain or an AC motor of another battery power system. As is appreciated in the art, classical motor control methods, if applied to real-time control of an asymmetric motor, can result in command tracking errors, as well as relatively poor interference rejection and motor performance at low fundamental frequency sampling ratios. Accordingly, the present solution is intended to extend the myriad benefits of virtual conversion (more commonly used to control symmetric / non-salient pole motors) to the control of asymmetric / salient pole motors. The resulting control system enables high-speed salient pole motors to be used in a wider range of applications, producing higher bandwidth torque. The present solution also enables selective and independent suppression of high and low frequency interference at each operating point of the AC motor.

[0005] An electric drive system according to an exemplary embodiment of the present disclosure includes a DC power source (e.g., a multi-unit electrochemical battery pack) and an inverter connected to the power source. The electric drive system also includes the above-mentioned AC motor and an associated motor controller. The AC motor can be connected to a load and an inverter, which is hereinafter referred to as a power inverter module (PIM). In a non-limiting embodiment, the load itself can be embodied as a set of wheels, in which the aforementioned electric drive system is used as part of a motor vehicle.

[0006] The AC motor contemplated herein has an asymmetric time constant. The controller is programmed to selectively correct the asymmetric time constant at predetermined operating points (e.g., torque and speed operating points) of the AC motor. The control action occurs in the logic of the controller via independent manipulation of the direct axis (d-axis) and quadrature axis (q-axis) inductance and impedance values ​​of the AC motor, such that the asymmetric time constant is virtually corrected or converted to a symmetric time constant within the control logic. In particular, the time constant is virtually corrected to be symmetric by manipulating / adding virtual inductance and virtual resistance terms independently and for each operating point, as detailed herein.

[0007] The controller may be configured to determine a torque command and an angular velocity of the AC motor, in which case the operating point of the AC motor includes the torque command and the angular velocity of the AC motor. In one or more embodiments, the electric drive system may be part of a mobile system on which the AC motor may operate as a traction or propulsion motor.

[0008] The controller may include a computer-readable storage medium including a first lookup table and a second lookup table, each of which is indexed by a torque command and an angular velocity of the AC motor. In such an embodiment, a symmetrical correction time constant may be selected by the controller from the first lookup table and used to calculate a virtual d-axis resistance and a virtual q-axis resistance as a virtual resistance term. A d-axis constant multiplier and a q-axis constant multiplier may be selected by the controller from the second lookup table and used to calculate a virtual d-axis inductance and a virtual q-axis inductance as a virtual inductance term.

[0009] In a possible implementation, the controller is configured to calculate the virtual d-axis inductance and the virtual q-axis inductance by multiplying the d-axis dynamic inductance and the q-axis dynamic inductance by the d-axis constant multiplier and the q-axis constant multiplier, respectively.

[0010] In one or more embodiments, the controller selectively suppresses low-frequency interference of the electric drive system by replacing the d-axis inductance and / or q-axis inductance in the device model with virtual d-axis inductance and / or virtual q-axis inductance from the second lookup table, respectively. The same controller can selectively suppress high-frequency interference of the electric drive system by replacing the d-axis resistance and / or q-axis resistance of the device model with virtual d-axis resistance and / or virtual q-axis resistance from the first lookup table, respectively.

[0011] Another aspect of the present disclosure includes a method for controlling an electric drive system having an AC motor connected to a PIM and a load. The AC motor is a salient pole motor. In one possible embodiment, the method includes determining an operating point of the AC motor and selectively correcting an asymmetric time constant of the AC motor at the operating point of the AC motor in a control logic of a controller. The control logic includes a device model of the electric drive system. The method includes selectively and independently manipulating d-axis and q-axis inductances and resistances via a controller so that the asymmetric time constants are virtually converted into symmetrical corrected time constants in the control logic by independently and for each operating point of the AC motor manipulating / adding virtual inductance and virtual resistance terms. The method also includes controlling the AC motor at the operating point using the symmetrical corrected time constants.

[0012] Also disclosed herein is a motor vehicle comprising one or more wheels and an electric drive system connected to the vehicle body. The electric drive system comprises a traction battery pack, a PIM connected to the traction battery pack, an AC traction motor connected to one or more of the PIM and the wheels, and a controller configured to perform the above method or a variation thereof. The AC traction motor is a salient pole motor. The controller is programmed with control logic including a plant model of the electric drive system, the plant model including an asymmetric time constant of the AC motor.

[0013] The present disclosure proposes the following technical solutions:

[0014] 1. An electric drive system, comprising:

[0015] Direct current (DC) power supply;

[0016] a power inverter module (PIM) connected to the DC power source;

[0017] an alternating current (AC) motor connected to the PIM and a load, wherein the AC motor is a salient pole machine having an asymmetric time constant; and

[0018] A controller programmed with control logic, the control logic including a device model of an electric drive system, wherein the device model includes an asymmetric time constant, and wherein the controller is configured to selectively correct the asymmetric time constant on an operating point specific basis via selective and independent manipulation of direct axis (d-axis) and quadrature axis (q-axis) inductance and resistance, such that the asymmetric time constant is virtually converted into a symmetric corrected time constant in the control logic by manipulating / adding virtual inductance terms and virtual resistance terms independently and for each operating point of the AC motor, and the AC motor is controlled at the operating point using the symmetric corrected time constant.

[0019] 2. An electric drive system according to technical solution 1, wherein the controller is configured to determine a torque command and an angular velocity of the AC motor, and wherein the operating point of the AC motor includes the torque command and the angular velocity of the AC motor.

[0020] 3. An electric drive system according to Technical Solution 2, wherein the electric drive system is part of a mobile system, on which the AC motor can be operated as a traction or propulsion motor.

[0021] 4. The electric drive system according to technical solution 2, wherein the controller includes a computer-readable storage medium, the computer-readable storage medium includes a first lookup table and a second lookup table, the first lookup table and the second lookup table are each indexed by the torque command and angular velocity of the AC motor, and wherein:

[0022] The symmetrical correction time constant is selected by the controller from a first lookup table and used to calculate a virtual d-axis resistance and a virtual q-axis resistance as virtual resistance terms; and

[0023] A d-axis constant multiplier and a q-axis constant multiplier are selected by the controller from the second lookup table and used to calculate a virtual d-axis inductance and a virtual q-axis inductance as virtual inductance terms.

[0024] 5. An electric drive system according to Technical Solution 4, wherein the controller is configured to calculate a virtual d-axis inductance and a virtual q-axis inductance by multiplying the d-axis dynamic inductance and the q-axis dynamic inductance by a d-axis constant multiplier and a q-axis constant multiplier, respectively.

[0025] 6. An electric drive system according to Technical Solution 4, wherein the controller is configured to selectively suppress low-frequency interference of the electric drive system by replacing the d-axis inductance and / or q-axis inductance in the device model with virtual d-axis inductance and / or virtual q-axis inductance from the second lookup table, respectively.

[0026] 7. An electric drive system according to Technical Solution 4, wherein the controller is configured to selectively suppress high-frequency interference of the electric drive system by replacing the d-axis resistance and / or q-axis resistance of the device model with virtual d-axis resistance and / or virtual q-axis resistance from the first lookup table, respectively.

[0027] 8. A method for controlling an electric drive system having an alternating current (AC) motor connected to a power inverter module (PIM) and a load, wherein the AC motor is a salient pole machine, the method comprising:

[0028] determining an operating point of the AC motor;

[0029] selectively correcting an asymmetric time constant of an AC motor at an operating point of the AC motor in control logic of a controller, the control logic including a plant model of an electric drive system, including selectively and independently manipulating direct axis (d-axis) and quadrature axis (q-axis) inductance and resistance via the controller such that the asymmetric time constant is virtually converted to a symmetric corrected time constant in the control logic by manipulating / adding virtual inductance and virtual resistance terms independently and for each operating point of the AC motor; and

[0030] The AC motor is controlled at the operating point using the symmetrical modified time constant.

[0031] 9. The method according to technical solution 8 further comprises:

[0032] determining, via the controller, a torque command and an angular velocity of the AC motor; and

[0033] The torque command and angular velocity are used as operating points of the AC motor.

[0034] 10. The method according to claim 9, wherein the electric drive system is part of a motor vehicle, on which the AC motor can be operated as a traction or propulsion motor, and the method further comprises:

[0035] mapping, via the controller, a pedal position of the motor vehicle to the torque command;

[0036] converting the torque command into a desired axle torque command for the motor vehicle; and

[0037] The motor vehicle is propelled via a traction or propulsion motor in response to the desired axle torque command.

[0038] 11. The method according to technical solution 9, wherein the controller includes a computer-readable storage medium, the computer-readable storage medium includes a first lookup table and a second lookup table indexed by the torque command and angular velocity of the AC motor, and the method further includes:

[0039] selecting the symmetrical correction time constant from the first lookup table;

[0040] calculating a virtual d-axis resistance and a virtual q-axis resistance as virtual resistance terms using the symmetrical modified time constant;

[0041] selecting a d-axis constant multiplier and a q-axis constant multiplier from the second lookup table; and

[0042] A virtual d-axis inductance and a virtual q-axis inductance are calculated as virtual inductance terms using the d-axis constant multiplier and the q-axis constant multiplier.

[0043] 12. The method according to technical solution 11 further comprises:

[0044] The virtual d-axis inductance and the virtual q-axis inductance are calculated by multiplying the d-axis dynamic inductance and the q-axis dynamic inductance by the d-axis constant multiplier and the q-axis constant multiplier, respectively.

[0045] 13. The method according to technical solution 12 further comprises:

[0046] Selectively suppressing low frequency interference of the electric drive system via the controller includes replacing the d-axis inductance and / or the q-axis inductance in the plant model with the virtual d-axis inductance and / or the virtual q-axis inductance from the second lookup table, respectively.

[0047] 14. The method according to technical solution 12 further comprises:

[0048] High frequency disturbances of the electric drive system are selectively suppressed via the controller by replacing the d-axis resistance and / or q-axis resistance of the plant model with virtual d-axis resistance and / or virtual q-axis resistance from the first lookup table, respectively.

[0049] 15. A motor vehicle comprising:

[0050] Car body;

[0051] one or more wheels connected to the body; and

[0052] An electric drive system connected to the vehicle body, the electric drive system comprising:

[0053] Traction battery pack;

[0054] a power inverter module (PIM) connected to the traction battery pack;

[0055] an alternating current (AC) traction motor connected to the PIM and one or more wheels, wherein the AC traction motor is a salient pole machine; and

[0056] A controller programmed with control logic, the control logic comprising a plant model of an electric drive system, wherein the plant model includes an asymmetric time constant of an AC motor, and wherein the controller is configured to:

[0057] determining a torque command and an angular velocity of the AC traction motor as an operating point thereof;

[0058] selectively correcting the asymmetric time constant at the operating point by selectively and independently manipulating the direct (d-axis) and quadrature (q-axis) inductance and resistance of the AC traction motor such that the asymmetric time constant is virtually converted to a symmetric corrected time constant in the control logic by manipulating / adding virtual inductance and virtual resistance terms independently and for each operating point of the AC motor; and

[0059] The AC traction motor is controlled at an operating point using the symmetrical modified time constant.

[0060] 16. The motor vehicle according to technical solution 15, wherein the controller is configured to:

[0061] Mapping pedal position to torque command; and

[0062] The torque command is converted into a desired axle torque command for powering one or more wheels via the AC traction motor.

[0063] 17. A motor vehicle according to technical solution 15, wherein the controller includes a computer-readable storage medium, the computer-readable storage medium includes a first lookup table and a second lookup table indexed by the torque command and angular velocity of the AC motor, and wherein the controller is configured to:

[0064] selecting the symmetrical correction time constant from the first lookup table, and using the symmetrical correction time constant to calculate a virtual d-axis resistance and a virtual q-axis resistance as virtual resistance terms; and

[0065] A d-axis constant multiplier and a q-axis constant multiplier are selected from the second lookup table, and virtual d-axis inductance and virtual q-axis inductance are calculated as virtual indication items using the d-axis constant multiplier and the q-axis constant multiplier.

[0066] 18. A motor vehicle according to technical solution 17, wherein the controller is configured to calculate the virtual d-axis inductance and the virtual q-axis inductance by multiplying the d-axis dynamic inductance and the q-axis dynamic inductance by the d-axis constant multiplier and the q-axis constant multiplier, respectively.

[0067] 19. A motor vehicle according to technical solution 17, wherein the controller is configured to selectively suppress low-frequency interference of the electric drive system by replacing the d-axis inductance and / or q-axis inductance in the device model with virtual d-axis inductance and / or virtual q-axis inductance determined using a second lookup table.

[0068] 20. A motor vehicle according to technical solution 17, wherein the controller is configured to selectively suppress high-frequency interference of the electric drive system by replacing the d-axis resistance and / or q-axis resistance of the device model with virtual d-axis resistance and / or virtual q-axis resistance determined using the first lookup table, respectively.

[0069] The above features and advantages, and other features and advantages of the present invention are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the present teachings as defined in the appended claims when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 A representative motor vehicle equipped with an electric drive system according to one aspect of the present disclosure is illustrated.

[0071] Figure 2 yes Figure 1 A block diagram of a portion of an electric drive system and a controller, wherein the controller is configured to selectively switch asymmetric time constants as part of the present motor control strategy.

[0072] Figure 3A and 3B Together the diagram shows Figure 1 and 2 Depicted are the direct-axis (d-axis) and quadrature-axis (q-axis) flux saturation characteristics of a representative asymmetric AC motor.

[0073] Figure 3C The linear and saturation operating regions of an AC motor are depicted in terms of dynamic and static inductance.

[0074] Figure 4 Is a description Figure 1 A schematic block diagram of the control of the electric drive system is shown.

[0075] Figure 5A and 5B The diagram shows the Figure 2 and 4 A possible embodiment of a current observer as part of a controller is shown.

[0076] Figure 6 is a method for controlling the Figure 1 Flow chart of an embodiment of a method of an electric drive system.

[0077] Figure 7 is described by Figure 2 and Figure 4 Block diagram of a controller using lookup table based determination of virtual q-axis and d-axis resistance and inductance values.

[0078] The present disclosure may be modified or implemented in alternative forms, and representative embodiments are shown in the drawings and described in detail below. The inventive aspects of the present disclosure are not limited to the disclosed embodiments. On the contrary, the present disclosure is intended to cover alternatives that fall within the scope of the disclosure defined by the appended claims. DETAILED DESCRIPTION

[0079] Referring to the drawings, wherein like reference numerals correspond to the same or similar parts throughout the several views, Figure 1 The vehicle body 100 of the motor vehicle 11 is shown. The electric drive system 10 is connected to the vehicle body 100. In other mobile or stationary battery power systems, including aircraft, rail vehicles, ships and other vessels, farm equipment, power generation equipment, cranes, conveyor systems, etc., the electric drive system 10 can be connected to structures other than the vehicle body 100. Thus, Figure 1 The motor vehicle 11 is merely one possible implementation of the electric drive system 10 and for the sake of illustrative consistency, the motor vehicle 11 is hereinafter used as the primary battery power system that will benefit from the present control strategy.

[0080] Figure 1 The electric drive system 10 in the embodiment includes a high voltage power supply 12 and an alternating current (AC) motor (M E )13. The AC motor 13 considered herein is an asymmetric / salient pole motor of the type described above. For example, the AC motor 13 may be implemented as an interior permanent magnet (IPM) synchronous motor. The electric drive system 10 and its AC motor 13 may be modeled as a physical device having an asymmetric time constant. Using control logic, the asymmetric time constant is corrected or virtually transformed in real time within the control logic 50L of the resident electronic motor control unit (hereinafter referred to as the controller (C) 50 for simplicity). This action makes the time constant symmetrical and occurs by changing the direct axis (d-axis) and quadrature axis (q-axis) inductance and resistance (impedance) of the AC motor 13 based on a specific operating point. This article refers to Figure 2-7 An exemplary implementation of the control logic 50L is set forth in detail.

[0081] Figure 1 The power source 12 in the non-limiting embodiment is configured as a multi-cell electrochemical propulsion or traction battery pack (B HV ) 12B, such as lithium ion, nickel metal hydride, etc. In such an embodiment, the term "high voltage" can encompass battery voltages of approximately 300 volts or higher, i.e., voltage levels suitable for vehicle propulsion. The electric drive system 10 also includes at least one power inverter module (PIM) 14, which is configured to convert a DC voltage (VDC) from the traction battery pack 12B into an AC voltage (VAC) suitable for energizing the AC motor 13, Figure 1 In the exemplary embodiment of the present invention, AC motor 13 is configured as an electric traction motor.

[0082] Figure 1 Representative hardware components of the electric drive system 10 include a battery pack 12B, an AC motor 13, and a PIM 14. The AC motor 13 includes a rotatable output member 130, which, in the illustrated embodiment, is coupled to one or more wheels 16. The AC traction motor 13 generates an output torque (T O ), which torque is then directed to one or more wheels 16 of the motor vehicle 11. Although omitted for simplicity of illustration, those skilled in the art will appreciate that alternative configurations of the electric drive system 10 may include more than one AC motor 13, and possibly more than one PIM 14.

[0083] During the driving mode of the motor vehicle 11, the controller 50 controls the PIM 14 via pulse width modulation (PWM) or another high frequency switching control technique suitable for the application. The controller 50 may apply the PWM switching control signal (CC 14 ) is transmitted to the PIM 14 to energize the AC motor 13. As is understood in the art, the solid-state power switches within the PIM 14 are constructed as semiconductor switching devices, such as insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), thyristors, or transistors having a PWM switching control signal (CC 14 ) commands and settings for controllable conduction (ON) mode and cutoff (OFF) mode of other electronic power switches.

[0084] Although for simplicity of explanation Figure 1 Although omitted from the description, it will be appreciated by those skilled in the art that the electric drive system 10 may include additional electrical components for powering various systems or functions onboard the motor vehicle 11. For example, the traction battery pack 12B may be connected to a DC-DC converter that is suitable for reducing the voltage level of the traction battery pack 12B (e.g., 300V or higher as described elsewhere above) to a typical auxiliary voltage level of 12-15V. An auxiliary battery, such as a lead-acid auxiliary battery, may be electrically connected to such a DC-DC converter, and the internal switching operation of the DC-DC converter ensures that the auxiliary battery remains charged or that one or more low-voltage systems onboard the motor vehicle 11 (e.g., radio, lighting, display screens, etc.) are provided with sufficient power to actuate their respective functions.

[0085] Within the scope of this disclosure, Figure 1 The controller 50 shown is programmed to act as a direct discrete time current controller for the virtually switched AC motor 13. To this end, one or more processors (P) 52 of the controller 50 are configured to receive input signals (CC I), and in response thereto, performing the method 50M as one or more algorithms (see Figure 6 ). Computer readable code or instructions for implementing this method 50M may be stored in a memory (M) 54, including a tangible, non-transitory computer-readable storage medium, such as a magnetic or optical medium, a CD-ROM, and / or a solid-state / semiconductor memory (e.g., various types of RAM or ROM).

[0086] The term "controller" and related terms such as control module, module, control, control unit, processor, and similar terms refer to one or more combinations of an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), an electronic circuit, a central processing unit (e.g., a microprocessor), and associated non-transitory memory components in the form of memory and storage devices (read-only, programmable read-only, random access, hard drive, etc.). The non-transitory components of the memory 54 are those components capable of storing machine-readable instructions in the form of one or more software or firmware programs or routines, combinational logic circuits, input / output circuits and devices, signal conditioning and buffering circuits, and other components accessible by the processor 52 to provide the described functionality.

[0087] Input / output circuits and devices include analog / digital converters and related devices that monitor inputs from sensors, monitoring such inputs at a preset sampling frequency or in response to a triggering event. Software, firmware, programs, instructions, control routines, codes, algorithms and similar terms mean a set of instructions executable by a controller, including calibration and lookup tables. Each controller executes a control routine to provide the desired functionality. Routines can be executed at regular intervals, such as at intervals of approximately 50-100 microseconds (ms) during ongoing operation. Alternatively, routines can be executed in response to the occurrence of a triggering event.

[0088] refer to Figure 2 , asymmetric AC motors, such as the AC motor 13 shown, are often difficult to properly analyze and control using classical motor control techniques common to symmetric / non-salient motors. Figure 1 Controller 50, Figure 2 The control logic 50L and Figure 6 In the method 50M, the controller 50 is able to virtually modify the time constant (τ) of the electric drive system 10 (physical device) in a manner specific to the operating point, where τ is the inductance (L) divided by the resistance (R). Doing so "virtually converts" this asymmetric time constant into a symmetric time constant. The method also allows Figure 1 The controller 50 uses a classic pole configuration type design to enable higher speed use of the AC motor 13 and provide other attendant benefits.

[0089] Aspects of the control logic 50L are Figure 2 As shown in block diagram form, the control logic 50L makes Figure 1 The controller 50 can be used as a discrete control system. The control logic 50L includes a command generation module (CGM) 20, which receives the Figure 1 The input signal (CC I ) as part of: (i) command torque T*, where the superscript “*” here and Figure 2 The rest of the numerals in the table indicate the values ​​commanded by the controller 50, and (ii) Figure 1 The measured or reported cell voltage (V dc ) and its associated DC voltage bus. As will be appreciated by those skilled in the art, the torque command (T*) may be calculated by the controller 50 in response to user inputs, such as accelerator and brake pedal inputs in different embodiments of the motor vehicle 11 and / or autonomously generated inputs, such as by mapping accelerator and brake pedal positions to the torque command (T*), and then converting the torque command (T*) into a desired axle torque command for powering one or more wheels 16 via the AC motor 13, in which case the AC motor 13 is used as a propulsion or traction motor. The CGM 20 ultimately generates d-axis and q-axis current commands, in Figure 2 In the literature, it is denoted as zI* dq (z), as a vector. As is understood in the art, zI* dq Implicit is the k+1th quantity.

[0090] The components of the control logic 50L include a current regulator (I-Reg) 22 and a current observer (I-Obs) 23. As is appreciated in the art, the current regulator 22 is ultimately responsible for controlling the current to the stator windings of the AC motor 13 via the operation of the PIM 14. As part of this task, the current regulator 22 takes into account the angular velocity (ω) of the AC motor 13. e ), for example, as the measured angular position (θ e ) derivative (d / dt), measuring the angular position (θ e ) is determined using a suitable position sensor 60 (eg, an encoder or resolver). The current regulator 22 ultimately receives the error signal (I dq，err (z)), the angular velocity of the AC motor 13 (ω e ) and the calculated d-axis and q-axis currents (zI dq (z)), the current observer 23 for its part receives the d-axis and q-axis current vectors (I dq (z)) as input and generates the above value zI dq (z) For use by the current regulator 22.

[0091] Figure 2 The current regulator 22 outputs or requests via the delay box Processed d-axis and q-axis voltage commands (zV* αβ (z)), where 1 / Z is the unit delay, to generate the command voltage V* αβ (z) as input to the PWM generation block (PWM Gen) 25. In the nominal "abc" reference frame of a representative three-phase embodiment of the AC motor 13, similar to Figure 1 The switch control signal (CC 14 ) of the switch control signal (S abc ) is used by the PIM 14 to excite the AC motor 13 of the physical system.

[0092] The measured or reported a, b, and c phase currents (i.e., I abc ) is then combined with the measured angular position (θ e ) are fed to the transform box (e jθe )26 as input I abc As described above, the transformation block 26 finally outputs the d-axis and q-axis current vectors (I dq (z)) as input to the current observer 23. Therefore, Figure 2 The current control feature of the control logic 50L shown in simplified block diagram form in determines the current command for the AC motor 13 while performing the abc to dq conversion in the closed loop shown.

[0093] Brief reference Figure 3A and 3B , unlike symmetrical / non-salient motors where the flux saturation properties will vary linearly with changes in d-axis and q-axis currents, Figure 1 and 2 The present AC motor 13 is asymmetric / salient. Therefore, the AC motor 13 as contemplated herein will experience nonlinear flux saturation, i.e., Figure 2 The physical device has a time constant The controller 50 of the present disclosure virtually transforms the τ in the control logic 50L to make the time constant symmetrical. Thus, as contemplated herein, the controller 50 controls the AC motor 13 so that the AC motor 13 behaves like a symmetrical motor despite its asymmetrical structure.

[0094] Discrete-time modeling of AC motors: Figure 1 and 2 The AC motor 13 is modeled in this paper using real space vectors. For example, for an exemplary interior permanent magnet (IPM) motor, the stator current vector in the rotor reference frame is defined as Idq =[I d I q ] T , where I d and I q are the individual components of the vector, and the matrix is ​​transposed by the superscript T. The conventions for indicating quantities of vectors in bold text are as follows. The symbol for a stationary reference frame is depicted as αβ. For example, the stator current vector in a stationary reference frame is defined as: I αβ =[I α I β ] T . Thus, the identity matrix, orthogonal rotation matrix and zero matrix are defined as follows:

[0095]

[0096] The voltage equation in the rotor rotating reference frame is given by:

[0097]

[0098] Among them, V dq =[V d V q ] T is the voltage vector, I dq =[I d I q ] T is the current vector, R is the stator resistance, λ dq =[λ d λ q ] T is the flux linkage vector, and ω e is the electrical angular velocity of the rotor. Figure 3A and 3B The magnetic flux λ represented by d and λ q is a function of time, and in other words, the rotor electrical angular position θ due to space harmonics in the stator-rotor air gap e and the function of temperature Tr dq ,Right now:

[0099] λ dq =[λ d (I d ,I q ,θ e ,Tr)λ q (I d ,I q ,θ e ,Tr)] T (3)

[0100] The effect of temperature is externally compensated by adjusting the current or flux command to achieve the desired torque and can be ignored when designing the proposed controller 50. In addition, changes in temperature appear as parameter uncertainty or disturbances to the current regulator 22. As the position (θ e ) is neglected because the current regulator 22 is designed to control the average stator current. Thus, taking into account the saturation and cross-saturation effects, the nonlinear relationship between flux and current is given by the following equation (4) and is Figure 3A and 3B These flux maps can be obtained from the motor characteristics or using finite element analysis (FEA) and used in the controller 50 in the form of a lookup table.

[0101] λ dq =[λ d (I d ,I q ) q (I d ,I q )] T (4)

[0102] The operating point model of equation (2) above, derived using a first order Taylor series expansion evaluated at the operating point, is given by equation (5) under the constant speed assumption:

[0103]

[0104] The dynamics of the current can be expressed by the flux difference table Δλ dq Shown as current difference ΔI dq Therefore, as described in equation (6), according to I dq The dynamic inductance L used in this paper is calculated by the flux gradient between two consecutive operating points. d (described below as the d-axis dynamic inductance L dd and q-axis dynamic inductance L dq ).like Figure 3C As shown, the dynamic inductance L d is defined as the incremental slope of the flux linkage curve, and the static inductance L s is defined as the chord slope, where the chord slopes 64-1, 64-2 and 64-3 are as follows Figure 3C When the AC motor 13 is operated at the low excitation point A in the linear region (I), the corresponding static and dynamic inductances L s and L d Basically the same or similar, that is, L s ~L d . With I dq When the AC motor 13 increases to point B, it becomes severely saturated, that is, the AC motor 13 is Figure 3C Here, the dynamic inductance (Ld) exhibits a similar behavior to the static inductance (L s ), namely, L s >>L d .

[0105] In this method, the dynamic inductance (L d ) is used to capture the saturation characteristics of the AC motor 13. The diagonal elements L in equation (6) d is responsible for the current dynamics, and the off-diagonal cross-coupling elements describe the cross-saturation effect. Since the cross-saturation elements are usually smaller than the diagonal elements, they are omitted and considered as interference to the current controller 22. Thus, the above equation (6) is simplified to equation (7):

[0106] Δλ dq =L d ΔI dq ,in

[0107] Δλ dq =L d ΔI dq ,in

[0108] Using the relationship from equation (7), the operating point linearized voltage equation from equation (5) can be written as equation (8):

[0109]

[0110] Laplace transforming equation (8) with the initial conditions and modeling the voltage with a rotating latch (because it is latched in the stationary reference frame) yields equation (9):

[0111]

[0112] In the following equations (10) and (11), t is defined as dq and t w The time constant allows the above equation (9) to be written as equation (12), and further written in partial fraction form as equation (13):

[0113]

[0114]

[0115]

[0116]

[0117] To return to the time domain, an inverse Laplace transform of equation (13) is performed, which yields equation (14) and is further discretized into a single time step, yielding equation (15):

[0118]

[0119]

[0120] Using the flux λ from equation (7) dq and current I dq The relationship between , equation (15) is simplified to equation (16). As equation (17) obtains the discrete-time AC motor device model:

[0121]

[0122]

[0123] Now refer to Figure 4-7 The above method is described.

[0124] Brief reference Figure 4 , Figure 2 The representative control logic 50L associated with the above-described current control acts on a mathematical model of the physical device whose operation is controlled, which in this case is the AC motor 13. Therefore, the control logic 50L uses the device model block 30 of the AC motor 13, which includes a delay model 31 and a device model 32. The device modeled via the device model block 30 does not change. However, the present method modifies the remainder of the control logic 50L. This occurs via the normalized gain block 33, the input coupling block 34, the device pole elimination block 35, the accumulator 36, and the state feedback block 37 that provides immediate virtual impedance state feedback.

[0125] As part of this approach, Figure 1 and Figure 2 The controller 50 can develop a linearized operating point discrete model of the AC motor 13 with accurate latch, discrete delay and saturation characteristics. This method will now be described as a series of discrete actions or steps.

[0126] Step 1 - Equipment Modeling: The controller 50 may establish the following relationship based on equation (17) as described above:

[0127]

[0128] Among them, T S is the sampling time. It will be converted into Figure 4Equation (18) of block 32 of is therefore used as a model of the physical device. Within the scope of the present disclosure, the time constant τ will be virtually modified in the control logic 50L.

[0129] Step 2 - Virtual Correction: Use the virtual resistance (R v ) and virtual inductance (L v ) vector, we get the virtual converted AC motor in equation (20):

[0130] and

[0131] and

[0132] in and

[0133] in

[0134] therefore:

[0135]

[0136] It corresponds to Figure 4 Model 32 in.

[0137] Step 3 - Time constant correction for each operating point: Then the desired time constant (t mod ) value is set to Figure 1 and 2 The method modifies the numerator or denominator of L / R so that L d / R and L q / R is the same. For example, when the AC motor 13 is at low speed, the controller 50 may require a higher stiffness (lower t mod ) or higher damping or disturbance suppression capability, for example, to suppress driveline resonances that appear as voltage or back EMF disturbances. At higher speeds, inertia filters out driveline disturbances, and stiffness can be set lower (higher τ mod ) to avoid causing noise, vibration and harshness (NVH) effects.

[0138] By using a configurable virtual inductor (L v) provides another control degree of freedom for the controller 50, which enables the suppression of disturbances at higher frequencies in equation (22) below. In the contemplated embodiment, this occurs as a function of torque and speed. Once the virtual inductance vector is set, the target time constant (τ) based on the desired virtual correction from equations (21) and (22) is calculated. mod ) to recalculate the virtual resistance vector of equation (23):

[0139] t mod =N(T * ,ω e )*T s (twenty one)

[0140] Virtual resistance (R v ) and virtual inductance (L v ) vectors allow selective interference suppression based on the operating point for low and high frequencies respectively. These are set based on equations (21) and (22):

[0141] L v =K(T * ,ω e )*L d (twenty two)

[0142] in, Here, K is a scalar value that can range from (0-1), meaning the percentage of the actual inductance used to determine the corrected virtual inductance:

[0143]

[0144] Therefore, using the disclosed virtual conversion allows the controller 50 to make τ symmetric. With two degrees of freedom, the virtual inductance L v Can be modified to suppress higher frequency interference. Virtual resistor R v It can also be modified to suppress low frequency interference. v and L v It thus serves herein as an adjustable "handle" that the controller 50 can use in real time to control the operation of the AC motor 13 and tune its performance.

[0145] Step 4 - Pole Placement: The pole placement type control scheme can then be designed as follows:

[0146]

[0147]

[0148]

[0149]

[0150] The above closed-loop response has a one sample delay. Here, f b is the bandwidth of the controller 50. Figure 4 The closed-loop response (first order without delay) of the current observer 23 can be expressed as:

[0151]

[0152] An important characteristic of discrete-time implementations is that a computational delay of one sampling period (actuator delay) is usually present in the control loop. c(z) Calculation based on measured current value G c(z) However, the voltage output of the regulator corresponds to the next sample instance (zV dq (z)) value, rather than the current sample (V dq (z)). Virtual resistance (R v ) and virtual inductance (L v ) The damping voltage can be calculated based on the current sample instance value and then applied to the next sample instance voltage command, resulting in a delayed state feedback response. This leads to degradation and oscillatory behavior at low fundamental frequency sampling ratios. Therefore, it is desirable to Figure 2 The current regulator 22 obtains and uses the next sample instance current value zI dq (z) and used for virtual resistor damping. Figure 2 The current observer 23 can be respectively used as follows Figure 5A and 5B The complex vector mode (block 23A) and the state feedback mode (block 23B) shown in FIG. p0 and K i0 are the proportionality constant and the integration constant respectively.

[0153] Reference now Figure 6 For clarity, method 50M is illustrated as a series of discrete logic blocks, each of which can be implemented by Figure 1 The processor 52 executes computer readable code or instructions to allow the controller 50 to perform the indicated functions.

[0154] After the controller 50 is initialized (*), for example, at a key-on event (where Figure 1 After the representative motor vehicle 11 is started directly or remotely by the operator), the controller 50 receives an input signal (CCI) at box B52. In a possible embodiment, box B52 requires receiving, calculating or otherwise determining Figure 2 The torque command (T*) and measured motor speed (ω e). The controller 50 therefore knows the operating point of the AC motor 13. The method 50M then proceeds to box B54.

[0155] At block B54, the controller 50 next determines the dq axis current commands, i.e., the current commands from Figure 2 CGM Box 20 zI* dq (z). After the value has been ascertained, method 50M proceeds to box B56.

[0156] exist Figure 6 At block B56 of FIG. 5 , the controller 50 receives the measured phase current, i.e. Figure 2 I abc When method 50M proceeds to block B58 , these values ​​are fed into current observer 23 .

[0157] Block B58 of method 50M is then replaced by Figure 1 The controller 50 is executed to predict the dq current, i.e., zI dq (z). This action uses Figure 2 The current observer 23 occurs. The method 50M continues to block B60.

[0158] Block B60 includes configuring virtual d-axis and q-axis inductors, namely L vd and L vq . Brief reference Figure 7 , block B60 may include accessing the torque command (T*) and the angular velocity (ω e ) indexed by the first lookup table 40 to determine the constant multiplier K dq The constant multiplier K that makes up the d-axis and q-axis d and K q It is then processed through calculation blocks 41 and 42 to derive the virtual d-axis inductance (L vd ) and virtual q-axis inductance (L vq ). For example, block 41 may be implemented as:

[0159] L vd =K d *L dd

[0160] Among them, L dd Again, it is the dynamic inductance of the d-axis. Similarly, block 42 may be implemented as:

[0161] L vq =K q *L qq

[0162] Method 50M then proceeds to box B62.

[0163] Block B62 includes a modified time constant for configuration symmetry, namely τ mod. Refer again Figure 7 , block B62 may include accessing the torque command (T*) and the angular velocity (ω e ) indexed second lookup table 400 to determine τ mod When the controller 50 proceeds to block B64, the correction time constant (τ mod ) is then temporarily stored in Figure 1 in the memory 54.

[0164] exist Figure 6 At block B64, the controller 50 calculates the d-axis and q-axis virtual resistances R vd and R vq .like Figure 7 As shown in boxes 43 and 44:

[0165]

[0166]

[0167] Figure 6 The method 50 then proceeds to box B66.

[0168] Box B66 requires assumptions Figure 4 The modified time constant τ determined above in block 32 is mod , virtual resistance R vd and R vq And the virtual inductance L vd and L vq To run Figure 2 of the current regulator 22. The method 50M then proceeds to block B68.

[0169] Figure 6 Box B68 includes the generation of Figure 2 The dq axis voltage command V*αβ is used to control the PIM 14. The PIM 14 responds to the switch control signal CC 14 (Right now, Figure 2 S abc ) switching operation, thereby controlling the operation of the AC motor 13. The method 50M is completed (**), or loops back to block B52 when the drive cycle remains active. Thus, the above method allows the controller 50 to determine the virtual d-axis inductance (L) by using the second lookup table 400 to determine the virtual d-axis inductance (L) and the virtual d-axis inductance (L) respectively. vd ) and / or virtual q-axis inductance (L vq )replace Figure 4 The d-axis inductance (L d ) and / or q-axis inductance (L q ) to selectively suppress low-frequency interference of the electric drive system 10, and by using the virtual d-axis resistance (Rvd ) and / or virtual q-axis resistance (R vd ) instead of the d-axis resistance (R d ) and / or q-axis resistance (R q ), selectively suppressing high-frequency interference of the electric drive system 10.

[0170] When combined Figure 1 The controller 50 and the above reference Figure 2 -5 and 7 describe the control logic 50L when used, Figure 6 The method 50M facilitates the expanded use of the AC motor 13, i.e., a representative asymmetric AC motor. As described above, the nonlinearity of such a motor, due to saliency and flux saturation characteristics, makes the asymmetric motor relatively difficult to analyze and control using classical motor control techniques. By virtually modifying the time constant of the device to make the time constant symmetric, as described herein, the AC motor 13 can be constructed and used in higher speed applications. Selective torque disturbance suppression at higher or lower frequencies is also achieved by manipulating the virtual inductance or resistance, which occurs independently on the d-axis and q-axis in a manner specific to the operating point. In view of the foregoing disclosure, those skilled in the art will appreciate these and other attendant benefits.

[0171] The detailed description and the accompanying drawings or figures are support and description of the present teaching, but the scope of the present teaching is limited only by the claims. Although some best modes and other embodiments for implementing the present teaching have been described in detail, there are various alternative designs and embodiments to practice the present teaching defined in the appended claims.

Claims

1. An electric drive system, comprising: Direct current (DC) power supply; a power inverter module (PIM) connected to the DC power source; an alternating current (AC) motor connected to the PIM and a load, wherein the AC motor is a salient pole machine having an asymmetric time constant; and A controller programmed with control logic, the control logic including a device model of an electric drive system, wherein the device model includes an asymmetric time constant, and wherein the controller is configured to selectively correct the asymmetric time constant on an operating point specific basis via selective and independent manipulation of direct axis (d-axis) and quadrature axis (q-axis) inductance and resistance, such that the asymmetric time constant is virtually converted into a symmetric corrected time constant in the control logic by manipulating / adding virtual inductance terms and virtual resistance terms independently and for each operating point of the AC motor, and the AC motor is controlled at the operating point using the symmetric corrected time constant.

2. The electric drive system according to claim 1, wherein: The controller is configured to determine a torque command and an angular velocity of the AC motor, and wherein an operating point of the AC motor includes the torque command and the angular velocity of the AC motor.

3. The electric drive system according to claim 2, wherein: The electric drive system is part of a mobile system on which the AC motor can operate as a traction or propulsion motor.

4. The electric drive system according to claim 2, wherein: The controller includes a computer readable storage medium including a first lookup table and a second lookup table, each indexed by a torque command and an angular velocity of the AC motor, and wherein: The symmetrical correction time constant is selected by the controller from a first lookup table and used to calculate a virtual d-axis resistance and a virtual q-axis resistance as virtual resistance terms; and A d-axis constant multiplier and a q-axis constant multiplier are selected by the controller from the second lookup table and used to calculate a virtual d-axis inductance and a virtual q-axis inductance as virtual inductance terms.

5. The electric drive system according to claim 4, wherein: The controller is configured to calculate a virtual d-axis inductance and a virtual q-axis inductance by multiplying the d-axis dynamic inductance and the q-axis dynamic inductance by a d-axis constant multiplier and a q-axis constant multiplier, respectively.

6. The electric drive system according to claim 4, wherein: The controller is configured to selectively suppress low frequency disturbances of the electric drive system by replacing the d-axis inductance and / or the q-axis inductance in the plant model with the virtual d-axis inductance and / or the virtual q-axis inductance from the second lookup table, respectively.

7. The electric drive system according to claim 4, wherein: The controller is configured to selectively suppress high frequency disturbances of the electric drive system by replacing the d-axis resistance and / or the q-axis resistance of the plant model with virtual d-axis resistance and / or virtual q-axis resistance from the first lookup table, respectively.

8. A method for controlling an electric drive system having an alternating current (AC) motor connected to a power inverter module (PIM) and a load, wherein: The AC motor is a salient pole motor, and the method comprises: determining an operating point of the AC motor; selectively correcting an asymmetric time constant of an AC motor at an operating point of the AC motor in control logic of a controller, the control logic including a plant model of an electric drive system, including selectively and independently manipulating direct axis (d-axis) and quadrature axis (q-axis) inductance and resistance via the controller such that the asymmetric time constant is virtually converted to a symmetric corrected time constant in the control logic by manipulating / adding virtual inductance and virtual resistance terms independently and for each operating point of the AC motor; and The AC motor is controlled at the operating point using the symmetrical modified time constant.

9. The method according to claim 8, further comprising: determining, via the controller, a torque command and an angular velocity of the AC motor; as well as The torque command and angular velocity are used as operating points of the AC motor.

10. The method according to claim 9, wherein: The electric drive system is part of a motor vehicle on which the AC motor is operable as a traction or propulsion motor, the method further comprising: mapping, via the controller, a pedal position of the motor vehicle to the torque command; converting the torque command into a desired axle torque command for the motor vehicle; and The motor vehicle is propelled via a traction or propulsion motor in response to the desired axle torque command.

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