Regenerative current limitation in synchronous motor drives

Abstract

The described technical solution is used to control the operation of an inverter to manage the voltage on a direct current (DC) bus and the regenerative power (current) provided to a battery. A control system and method are provided to control the operation of a motor using a controller. More specifically, the controller is configured to calculate a current-based torque limit that satisfies a regenerative current limit, and a voltage-based torque limit that satisfies a voltage limit constraint of the DC bus. The controller is configured to calculate a torque limit that satisfies the regenerative current limit and voltage limit of the DC bus, and to command multiple switches within the inverter to generate a direct-axis current from the motor that corresponds to a torque demand and is in accordance with the torque limit. The proposed system and method provide a motor current that exceeds the demagnetization current limit of the motor.

Description

Technical Field

[0001] The present application generally relates to methods and systems for controlling the operation of an electric machine. More specifically, the present application relates to methods and systems for managing regenerative current from an electric machine. Example embodiments are provided in an electric power steering (EPS) system. Background Art

[0002] Modern electric power steering (EPS) systems employ a permanent magnet synchronous motor (PMSM) based electric drive that provides torque assistance to the driver. The vehicle battery is typically used as the power source for the EPS system. Since multiple electronic systems in a vehicle consume power from the vehicle battery, it is critical that each system actively manages the power (or current) it draws from or supplies back to the battery. With the advent and popularity of electric vehicles, it is now even more critical to protect the battery through proper management of current and voltage. Summary of the invention

[0003] According to one or more embodiments, a control system for controlling the operation of an electric motor includes an inverter operable to rectify current from an AC phase bus of the electric motor to a DC bus using switches. The control system also includes a controller operable to: calculate a voltage-based torque limit corresponding to a voltage limit constraint of the DC bus; calculate a current-based torque limit corresponding to a regenerative current limit of the DC bus; and when the current-based torque limit is less than the voltage-based torque limit, calculate a torque limit defined by the current-based torque limit. The controller is also operable to operate switches of the inverter to produce an output torque corresponding to a torque demand and in accordance with the torque limit. The controller is also operable to operate switches to regulate the direct-axis current to not exceed a maximum d-axis current, wherein the maximum d-axis current is defined by one of a demagnetization current limit or a peak d-axis current of the electric motor, the peak d-axis current corresponding to a quadrature-axis current having a real solution.

[0004] According to one or more embodiments, a method for controlling the operation of an electric motor is provided. The method includes: calculating a voltage-based torque limit corresponding to a voltage limit constraint of a DC bus; calculating a current-based torque limit corresponding to a regenerative current limit of the DC bus; when the current-based torque limit is less than the voltage-based torque limit, calculating a torque limit defined by the current-based torque limit; commanding a plurality of switches within an inverter to cause the electric motor to produce an output torque corresponding to a torque demand and according to the torque limit; and commanding the plurality of switches to adjust the direct-axis current to not exceed a maximum d-axis current, the maximum d-axis current being defined by one of a demagnetization current limit of the electric motor or a peak d-axis current, the peak d-axis current corresponding to a quadrature-axis current having a real solution.

[0005] According to one or more embodiments, a method for controlling operation of an electric motor is provided. The method includes: calculating a voltage-limited direct-axis current of the electric motor corresponding to a voltage-limited constraint of a DC bus; calculating a current-limited direct-axis current of the electric motor corresponding to a regenerative current limit of the DC bus; calculating a final direct-axis current limit as the maximum of the voltage-limited direct-axis current and the current-limited direct-axis current; and commanding a plurality of switches within an inverter to generate a direct-axis current that satisfies the final direct-axis current limit.

[0006] These and other advantages and features will become more apparent from the following description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the present disclosure will be apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0008] Figure 1 depicts a block diagram of an exemplary embodiment of an electric power steering system according to aspects of the present disclosure;

[0009] Figure 2 depicts the power flow of a motor control system according to aspects of the present disclosure;

[0010] Figure 3 depicts a graph of applied torque versus speed for a motor control system according to aspects of the present disclosure;

[0011] Figure 4 depicts a block diagram of an example control system for an electric machine according to aspects of the present disclosure;

[0012] Figure 5 depicts a block diagram of an example algorithm for controlling regenerative current according to aspects of the present disclosure;

[0013] Figure 6 depicts a block diagram of an example algorithm for controlling regenerative current according to aspects of the present disclosure;

[0014] Figure 7 depicts a flow chart for calculating a maximum d-axis current to provide a battery current that satisfies a regeneration current limit;

[0015] Figure 8 a graph depicting the torque capabilities of an example motor control system according to aspects of the present disclosure;

[0016] Fig. 9 A graph depicting d-axis current of an example motor control system according to aspects of the present disclosure;

[0017] Fig.10 a graph depicting battery current of an example motor control system according to aspects of the present disclosure;

[0018] Fig.11 a graph depicting motor current of an example motor control system according to aspects of the present disclosure;

[0019] Fig.12 depicts a graph of q-axis current versus d-axis current for an example motor control system according to aspects of the present disclosure;

[0020] Fig.13 depicts a graph of q-axis current versus d-axis current for an example motor control system according to aspects of the present disclosure;

[0021] Fig.14 depicts a graph of battery current versus speed for an example motor control system according to aspects of the present disclosure;

[0022] Fig.15 A graph depicting maximum d-axis current for an example motor control system according to aspects of the present disclosure;

[0023] Fig.16 a graph depicting the torque capabilities of an example motor control system according to aspects of the present disclosure;

[0024] Fig.17 a graph depicting battery current of an example motor control system according to aspects of the present disclosure;

[0025] Fig.18 a graph depicting motor current of an example motor control system according to aspects of the present disclosure;

[0026] Fig.19 A graph depicting d-axis current of an example motor control system according to aspects of the present disclosure;

[0027] Fig. 20A A flow chart depicting a method for permanent magnet synchronous motor (PMSM) control in a steering system according to aspects of the present disclosure;

[0028] Fig. 20B Depicted Fig. 20A Continuation of the flowchart of;

[0029] Fig. 20C Depicted showing Fig. 20A A flowchart of the sub-steps of the method;

[0030] Fig.20D Depicted showing Figures 20A-20B A flowchart of the sub-steps of the method; and

[0031] Fig.20E Depicted showing Figures 20A-20B Flowchart of the sub-steps of the method. DETAILED DESCRIPTION

[0032] Reference is now made to the drawings, wherein the present disclosure will be described with reference to specific embodiments, but not limited thereto, it being understood that the disclosed embodiments are merely illustrative of the present disclosure that may be embodied in various ways and alternatives. The drawings are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching one skilled in the art to use the present disclosure in various ways.

[0033] As used herein, the terms module and submodule refer to one or more processing circuits, such as application specific integrated circuits (ASICs), electronic circuits, processors (shared, dedicated, or grouped) and memories that execute one or more software or firmware programs, combinational logic circuits, and / or other suitable components that provide the functionality. It will be appreciated that the submodules described below may be combined and / or further divided.

[0034] An active regenerative current management (limiting) algorithm is proposed in the present disclosure. The algorithm manages the regenerative power (current) supplied to the battery by actively controlling the motor current. In addition to directly limiting the allowable torque, a feature is proposed in which the efficiency of the electric drive is reduced in order to produce higher torque while still complying with the externally imposed regenerative current limit. The proposed supervisory control structure is very modular, which enables the feature to be turned off, thereby enabling maximum efficiency operation by reducing torque alone. In addition to the modularity, the proposed algorithm is optimal in terms of both torque and efficiency management, and additionally, the calculations are relatively simple.

[0035] In various embodiments, the motor is configured to perform at least one of: applying assist torque to a steering system of the vehicle, and controlling the steering system. In some embodiments, the proposed systems and methods ensure that the motor current always remains below the demagnetization current limit of the motor. In other embodiments, the proposed systems and methods may not limit the motor current to the demagnetization current limit of the motor. For example, a motor in an EPS system may have a motor current that exceeds the demagnetization current limit of the motor during dynamic steering events (e.g., braking over curbs). Such applications may be relatively infrequent and / or short in duration, such that the risk of motor demagnetization may be relatively low.

[0036] Referring now to the accompanying drawings, in which the technical solution will be described with reference to specific embodiments, without limiting it, Figure 1is an exemplary embodiment of an electric power steering system (EPS) 40 suitable for implementation of the disclosed embodiments. The steering mechanism 36 is a rack-and-pinion type system and includes a rack (not shown) within a housing 50 and a pinion (also not shown) located below a gear housing 52. As the operator input (hereinafter represented as the steering wheel 26 (e.g., a hand-held steering wheel, etc.)) is rotated, the upper steering shaft 29 is rotated, and the lower steering shaft 51 connected to the upper steering shaft 29 by the universal joint 34 rotates the pinion. The rotation of the pinion moves the rack, which moves the tie rods 38 (only one shown), which in turn moves the steering knuckles 39 (only one shown), which rotate the steerable wheel(s) 44 (only one shown).

[0037] The electric power steering assist is provided by a control arrangement generally indicated by reference numeral 24 and includes a controller 16 and an electric machine 19, which may be a permanent magnet synchronous motor (PMSM) and is hereinafter referred to as motor 19. The controller 16 is powered by a vehicle power supply 10 via a DC bus 12. The controller 16 receives a vehicle speed signal 14 indicative of the vehicle speed from a vehicle speed sensor 17. The steering angle is measured by a position sensor 32 (which may be an optically encoded sensor, a variable resistor sensor, or any other suitable type of position sensor), and a position signal 20 is supplied to the controller 16. The motor speed may be measured using a tachometer or any other device and transmitted to the controller 16 as a motor speed signal 21. The position sensor 32 may be a position sensor 21, which ... m The motor speed is measured, calculated, or a combination of both. For example, the motor speed ω m can be calculated as the change in motor position θ as measured by position sensor 32 over a specified time interval. For example, it can be calculated according to the equation ω m =Δθ / ΔtThe motor speed ω m is determined as the derivative of the motor position θ, where Δt is the sampling time and Δθ is the change in position during the sampling interval. Alternatively, the motor rate can be derived from the motor position as the rate of change of position with respect to time. It will be appreciated that there are many well-known methods for performing the derivative function.

[0038] As the steering wheel 26 is turned, the torque sensor 28 senses the torque applied to the steering wheel 26 by the vehicle operator. The torque sensor 28 may include a torsion bar (not shown) and a variable resistor type sensor (also not shown) that outputs a variable torque signal 18 to the controller 16 relative to the amount of twist on the torsion bar. Although this is a torque sensor, any other suitable torque sensing device used with known signal processing techniques will suffice. In response to various inputs, the controller sends a command 22 to the motor 19, which provides torque assistance to the steering system through the worm 47 and worm gear 48, thereby providing torque assistance for vehicle steering.

[0039] It should be noted that although the disclosed embodiments are described by reference to motor control for electric steering applications, it will be understood that these references are illustrative only and the disclosed embodiments may be applied to any motor control application employing an electric motor, such as steering, valve control, etc. In addition, the references and descriptions herein may be applicable to many forms of parameter sensors, including but not limited to torque, position, speed, etc. It should also be noted that references herein to electric machines include but are not limited to motors, and for the sake of brevity and simplicity, only motors will be referenced in non-limiting cases.

[0040] In the control system 24 as depicted, the controller 16 uses torque, position, speed, etc. to calculate (multiple) commands to deliver the required output power. The controller 16 is configured to communicate with various systems and sensors of the motor control system. The controller 16 receives signals from each system sensor, quantifies the received information, and provides (multiple) output command signals in response thereto, in this example, for example, to the motor 19. The controller 16 is configured to generate (multiple) corresponding voltages from an inverter (not shown, which can be optionally merged with the controller 16 and will be referred to as the controller 16 in this article) so that when applied to the motor 19, the desired torque or position is produced. In one or more examples, the controller 16 operates in a feedback control mode as a current regulator to generate the command 22. Alternatively, in one or more examples, the controller 16 operates in a feedforward control mode to generate the command 22. Because these voltages are related to the position and speed of the motor 19 and the desired torque, the position and / or speed of the rotor and the torque applied by the operator are determined. The position encoder is connected to the lower steering shaft 51 to detect the angular position θ. The encoder can sense the rotational position based on optical detection, magnetic field changes or other methods. Typical position sensors include potentiometers, rotary transformers, synchronizers, encoders, etc., and combinations including at least one of the foregoing. The position encoder outputs a position signal 20, which indicates the angular position of the lower steering shaft 51, and thereby indicates the angular position of the motor 19.

[0041] The desired torque may be determined by one or more torque sensors 28 that transmit a torque signal 18 indicative of the applied torque. One or more exemplary embodiments include such a torque sensor 28 and the torque signal(s) 18 therefrom, such as may be responsive to a flexible torsion bar, T-bar, spring, or similar device (not shown) configured to provide a response indicative of the applied torque.

[0042] In one or more examples, temperature sensor(s) 23 are located at the motor 19. Preferably, the temperature sensor 23 is configured to directly measure the temperature of a sensing portion of the motor 19. The temperature sensor 23 transmits a temperature signal 25 to the controller 16 to facilitate processing and compensation as specified herein. Typical temperature sensors include thermocouples, thermistors, thermostats, etc., as well as combinations including at least one of the foregoing sensors, which provide a calibratable signal proportional to a specific temperature when properly placed.

[0043] Position signal 20, rate signal 21 and (multiple) torque signal 18 are applied to controller 16. Controller 16 processes all input signals to generate values ​​corresponding to each signal, thereby generating rotor position values, motor speed values ​​and torque values ​​that can be used for processing in the algorithm specified in this article. Measurement signals such as those mentioned above are also usually linearized, compensated and filtered as needed to enhance characteristics or eliminate undesirable characteristics of the acquired signals. For example, the signal can be linearized to improve processing speed or to solve the large dynamic range of the signal. In addition, frequency or time-based compensation and filtering can be used to eliminate noise or avoid undesirable spectral characteristics.

[0044] In order to perform the specified functions and desired processing, and the calculations therefor (e.g., identification of motor parameters, (multiple) control algorithms, etc.), the controller 16 may include, but is not limited to, (multiple) processors, (multiple) computers, (multiple) DSPs, memories, storage devices, (multiple) registers, timing, (multiple) interrupts, (multiple) communication interfaces, and input / output signal interfaces, etc., and combinations including at least one of the foregoing items. For example, the controller 16 may include input signal processing and filtering to enable accurate sampling and conversion or acquisition of such signals from the communication interface. Additional features of the controller 16 and certain processes herein are discussed in detail later herein.

[0045] Figure 2 The power flow of the motor control system is depicted. The depicted motor control system is from a steering system 40 including a control module 16 and an electric machine 19, which define a voltage loop including the voltage across a battery (not shown) and the voltage at the input of an inverter (not shown), which is then connected to the electric machine 19.

[0046] For a given battery voltage (V BATT ) and the supply voltage to the controller 16 (V ecu ), the power equation can be solved to obtain the motor current limit. Considering the battery voltage the circuit model can be mathematically represented as follows.

[0047] V ecu =V BATT -R BH I s

[0048] In the above equation, R BH represents the battery harness resistance, and I s Represents the battery current from the battery to the control module 16. Battery current I s A positive value of indicates a supply current drawn from the battery 10 to the control module 16. The battery current I s A negative value of indicates a regenerative current from the control module 16 to the battery 10 .

[0049] Figure 3 Depicts a graph of applied torque versus speed for a motor control system according to aspects of the present disclosure. Specifically, Figure 3 A graph including four quadrants is depicted, wherein quadrants II and IV are each associated with a motor control system in a regeneration mode.

[0050] Figure 4 1 depicts a block diagram of an example control system 100 for an electric machine 19 according to aspects of the present disclosure. In some embodiments, and as Figure 4 As shown, the motor 19 is a permanent magnet synchronous machine (PMSM) type electric motor. However, the motor 19 can be another type of motor or motor / generator, such as a wound field machine. In the regenerative mode, power is generated by the motor 19 as an alternating current on the AC phase bus 120 and converted by the inverter 124 to DC power on the DC bus 12. The inverter 124 includes a plurality of switches 126 (e.g., field effect transistors (FETs)) to rectify the current from the AC phase bus 120 to the DC bus 12. In some embodiments, the DC bus 12 is coupled to a DC power source (e.g., a battery 10).

[0051] The controller 130 communicates with the inverter 124 via the communication path 132 for monitoring a plurality of different parameters of the inverter 124 and for controlling the operation of the inverter 124 to rectify the AC power from the AC phase bus 120, thereby transferring power from the motor 19 and causing the motor 19 to generate braking torque. Such operation corresponds to Figure 3 The graph of applied torque versus speed is shown for the regeneration mode in Quadrants II and IV.

[0052] Figure 5 1 is a block diagram of a first algorithm 200 for controlling a regenerative current according to aspects of the present disclosure. The first algorithm 200 may be implemented using hardware, software, or a combination of hardware and software. The first algorithm 200 is implemented by the controller 130 to control the inverter 124 to control the regenerative current I r Specifically, the first algorithm 200 receives the torque request T c , voltage limit constraint V b and regenerative current limit I rl As input. Voltage limit constraints V b is the maximum voltage value for the DC bus 12, and the regenerative current limit I rl The maximum current that the inverter 124 is allowed to provide to the DC bus 12. The regenerative current limit I rl and voltage limit constraints V b Each of these may depend on characteristics of the battery 10 and / or other aspects of the vehicle power system. rl and / or voltage limit constraints V b One or both of may be fixed during operation of the system. Alternatively, the regenerative current limit I rl and / or voltage limit constraints V b One or both of the above may be variable. For example, the regenerative current limit I rl It can change with time or with the speed of the motor 19. The controller 16 can make dynamic adjustments to simultaneously meet the regenerative current limit I rl and voltage limit constraints V b The first algorithm 200 generates a current command I for controlling the operation of the inverter 124 * dq More specifically, the current command I * dq is converted into a voltage command V * dq , the voltage command V * dq is applied to the inverter 124. The current command I * dq The d-axis component and the q-axis component of the current of the motor 19 are included.

[0053] The first algorithm 200 is divided into two main parts, a torque capability determination block 210 and a current command calculation block 212. The first algorithm 200 also includes a voltage command calculation block 214 and an inverter 124. The torque capability determination block 210 generates a torque command T command and voltage-limited d-axis current I dmaxvand supplies it to the current command calculation block 212. The torque capability determination block 210 includes a regenerative current peak torque (RCPT) block 220, which is configured to calculate the regenerative current limit I corresponding to the DC bus 12. rl The torque T based on the regenerative current limit r The RCPT block 220 calculates the torque T based on the regenerative current limit. r , which is the motor 19 can limit I for a given regenerative current rl The maximum possible torque generated is derived as follows. Based on the supply voltage V ecu 、Battery current I s and the input circuit resistance R c The total electrical power P e as follows.

[0054]

[0055] According to the q-axis and d-axis motor current I dq The electrical power is expressed as follows.

[0056]

[0057] Among them, I d is the d-axis current, I q is the q-axis current, ω e is the electrical speed, K e is the motor voltage constant, ω m is the mechanical speed, L q and L d They are the q-axis inductance and d-axis inductance of the motor 19 respectively.

[0058] By examining the power equation as a function of motor current, it can be observed that, under given operating conditions, the peak torque for a given regenerative current limit will occur at the maximum allowable d-axis motor current. Then, for a given regenerative current limit, the peak torque is obtained as I obtained from the above power equation q The root(s) of the following quadratic equation.

[0059]

[0060] Since the peak torque occurs at the maximum d-axis motor current value I d Therefore, by substituting I d Equal to I dmax To solve the above equation, I dmax Considering the voltage limit constraint V b The d-axis current value at which the peak torque occurs. Note that in some embodiments, I dmax represents the demagnetization current limit I of the motor 19 under voltage-limited operationd_demag In other words, if the demagnetization current exceeds the limit I d_demag A current of may cause permanent demagnetization of the permanent magnets within the motor 19. Therefore, this value serves as the maximum allowable d-axis current that can be generated under any given operating condition. The solution to the quadratic equation is given below.

[0061]

[0062] Among them, I q1 and I q2 All positive or all negative depending on speed. Usually the lower positive (or negative) value is used.

[0063] Finally, the peak torque can be calculated as follows.

[0064]

[0065] Among them, N p is the number of poles of the motor 19. The positive and negative peak torque values ​​occurring at corresponding (same) speed signs are equal to the root T r1 and T r2 .

[0066] Note that the existence of roots depends on the following conditions.

[0067]

[0068] This condition is actively checked to ensure that a solution exists. In the absence of a solution, the (positive and negative) peak torque T based on the regenerative current limit rp and T rn Can be set to the peak torque T based on the voltage vp and T vn The same value (alternatively, the value can be set to an arbitrarily large number so that subsequent blocks essentially ignore it).

[0069] The final peak torque value T ap and T an It can be calculated as follows.

[0070] T apn =sign(T rpn )Xmax(|T rp |,|T vp |), where R v =True

[0071] T apn =T rvpn , where R v = False

[0072] Note that in some cases, it is also possible to implementrp and T rn The value of has additional logic for the correct sign.

[0073] The above algorithm calculates the maximum possible d-axis current to cause the motor 19 to produce a torque T based on the regenerative current limit. r , which is related to the DC bus regenerative current limit I rl The corresponding regenerative (braking) torque is therefore inherently inefficient. However, for some safety-critical applications (e.g., EPS), a compromise in efficiency is acceptable and even desirable, since low braking torque could potentially lead to driver injury and even vehicle loss of control in some driving conditions. This is especially true when the allowed regenerative current limit is low. However, in some applications, the limit may be large enough, or efficiency may be a priority. In these cases, different schemes may be implemented in which efficiency is improved at the expense of peak allowable torque. For example, this can be achieved by increasing the maximum allowable torque to 100 Hz. q I in the quadratic equation d The value is done using zero to calculate the torque based on the peak regen current limit (as described above).

[0074] Still reference Figure 5 The torque capacity determination block 210 further includes a voltage-based peak torque (VPT) block 222 configured to calculate the supply voltage V of the DC bus 12. ecu The corresponding voltage-based torque limit T v The torque capacity determination block 210 also includes a peak torque arbitration (PTA) block 224 that is configured to determine the voltage-based torque limit T v and torque T based on regenerative current limitation r The value is judged to determine the torque limit T pk More specifically, the PTA block 224 is configured to calculate the torque limit T pk As the torque T based on the regenerative current limit r and voltage-based torque limit T v For example, the PTA block 224 is configured to limit the torque T based on the regenerative current limit. r Less than the voltage-based torque limit T v When the torque limit T pk Set equal to the torque T based on the regenerative current limit r , and the torque limit based on voltage T v Less than the torque limit T based on the regenerative current r When the torque limit T pk Set equal to the voltage-based torque limit T v .

[0075] The torque capacity determination block 210 also includes a torque command limit (TCL) block 226 configured to determine the torque demand T c Clamp to not exceed the torque limit T pk To generate the torque command T command In other words, the TCL block 226 is configured to convert the torque command T command Calculated as the torque demand T c and torque limit T pk The smaller of .

[0076] Figure 5 The current command calculation block 212 of the first algorithm 200 shown above includes a maximum torque per ampere (MTPA) block 240, a d-axis motor current search (RCDC) block 242 based on regenerative current, and a maximum torque per voltage (MTPV) block 244. The MTPA block 240 receives the torque command T from the torque capability determination block 210. command , and calculate the torque command T command Those minimum motor currents are then sent to the RCDC block 242, which searches for the d-axis current I d The optimal value is to meet the regenerative current limit I rl In some embodiments, the RCDC block 242 increases the d-axis current variable in steps until the corresponding calculated battery current I s Equal to or at the regenerative current limit I rl The d-axis current search may include starting from a starting value I dmin In some embodiments, the starting value I dmin Can be zero.

[0077] Note that the search may be accomplished by using any known numerical technique involving an iterative solver, such as, for example, the bisection method. The search may continue until the calculated battery current I′ s and regenerative current limit I rl The difference between is within an acceptable predetermined tolerance. In some embodiments, a predetermined limit may also be imposed on the number of iterations. Where efficiency is a priority, the RCDC block 242 may be disabled and essentially act as a pass-through.

[0078] The output of the RCDC block 242 is then sent to the MTPV block 244 to ensure that the voltage limit constraint V b , and then use it as the final current command I * dq The voltage command calculation block 214 generates a corresponding voltage command V *dq . Set those voltage commands V * dq The voltage is supplied to the inverter 124 which functions as the inverter 124. Therefore, the inverter 124 generates an output phase voltage V on the AC phase bus 120. abc , so that the motor 19 generates a braking torque T e .

[0079] Reference now Figure 6 , a second algorithm 300 for controlling the regenerative current according to aspects of the present disclosure. The second algorithm 300 may be implemented using hardware, software, or a combination of hardware and software. The second algorithm 300 is implemented by the controller 130 to control the inverter 124 to control the regenerative current I r Specifically, the second algorithm 300 accepts the torque request T c , the voltage limit constraint V of the DC bus 12 b and the regenerative current limit I of the DC bus 12 rl As input, the second algorithm 300 generates a current command I for controlling the operation of the inverter 124. * dq As output, it may be performed similarly or identically as in the first algorithm 200, and as Figure 5 The current command I * dq The regenerative current limit I of the DC bus 12 includes the d-axis component and the q-axis component. rl and voltage limit constraints V b Each of these may depend on characteristics of the battery 10 and / or other aspects of the vehicle power system. rl and / or voltage limit constraints V b Either or both of may be hard-coded in the hardware or software of the controller 16 or in another device or memory. Additionally or alternatively, based on given operating conditions, the regenerative current limit I rl and / or voltage limit constraints V b Either or both of these may be changed during operation of the system. In some embodiments, the regenerative current limit I rl and / or voltage limit constraints V b Either or both of may be determined by the controller 16 based on calculation or another means (eg, a lookup table). The second algorithm 300 may include aspects or portions similar or identical to those described above in the first algorithm 200 .

[0080] The second algorithm 300 is divided into two main parts, a torque capability determination block 310 and a current command calculation block 312. The torque capability determination block 310 generates a torque command T commandand the final d-axis current limit and supplies it to the current command calculation block 312. The second algorithm 300 includes several blocks that may function similarly or identically to the corresponding blocks of the first algorithm 200 described above. For example, the torque capacity determination block 310 of the second algorithm 300 includes a regenerative current peak torque (RCPT) block 320, which may be similar or identical to the regenerative current peak torque (RCPT) block 220 of the first algorithm 200. The torque capacity determination block 310 of the second algorithm 300 also includes a voltage-based peak torque (VPT) block 322, which may be similar or identical to the voltage-based peak torque (VPT) block 222 of the first algorithm 200. The torque capacity determination block 310 of the second algorithm 300 also includes a peak torque arbitration (PTA) block 324, which may be similar or identical to the peak torque arbitration (PTA) block 224 of the first algorithm 200. The torque capacity determination block 310 of the second algorithm 300 also includes a torque command limit (TCL) block 326 , which may be similar or identical to the torque command limit (TCL) block 226 of the first algorithm 200 .

[0081] Figure 6 The current command calculation block 312 of the second algorithm 300 shown above includes a maximum torque per ampere (MTPA) block 340, and a d-axis motor current search (RCDC) block 342 based on regenerative current and a maximum torque per voltage (MTPV) block 344. Each of those blocks may be configured similarly or identically to the corresponding blocks 240, 242, 244 of the first algorithm 200, respectively.

[0082] As described above, the second algorithm 300 also includes several blocks that are not present in the first algorithm 200. For example, the torque capability determination block 310 of the second algorithm 300 includes a maximum d-axis current for a voltage constraint (MDV) block 330. The torque capability determination block 310 of the second algorithm 300 also includes a maximum d-axis current for a regenerative current constraint (MDR) block 332 and a maximum d-axis current arbitration (MDA) block 334.

[0083] The RCPT block 320 is configured to calculate the regenerative current limit I rl The corresponding torque T based on the regenerative current limit r The RCPT block 320 calculates the torque limit T based on the regenerative current. r , which is the motor 19 can be for a given regenerative current limit I rl The maximum possible torque generated is derived as follows. Based on the supply voltage V ecu 、Battery current I s and the input circuit resistance R c The total electrical power P e as follows.

[0084]

[0085] According to the q-axis and d-axis motor current I dq The electrical power is expressed as follows.

[0086]

[0087] In the above equation, “a” represents Conversion factors when using line parameters. By examining the power equation based on the motor current, we can see that at the regenerative current limit I rl The peak torque at occurs at the maximum possible d-axis motor current value. Using the above two equations, we can derive the following equation:

[0088]

[0089] To calculate the current limit for regeneration I rl The peak q-axis current I q , the above equation can be written as follows.

[0090]

[0091] The above equation is based on I q The quadratic equation can be solved to obtain two roots. Since the regenerative current limit I rl The peak torque occurs at the maximum d-axis motor current value, so the D-axis current calculated from the maximum D-axis current arbitration (MDA) block 334 is substituted into the above equation.

[0092] The MDA block 334 generates a voltage-based maximum d-axis current I from the MDV block 330. dmaxv The maximum d-axis current I based on the regenerative current limit from the MDR block 332 dmaxr The final maximum d-axis current I dmaxf The maximum d-axis current I based on voltage dmaxv is the voltage-dependent peak d-axis current I d value, where, at a given supply voltage V ecu In some embodiments, the peak torque occurs at dmaxv Represents the demagnetization current limit I d_demag For PMSM motor 19, the demagnetization current limit I d_demag Equal to 4K e / (√3L d N p ), where K e is the anti-electromagnetic force constant, L d is the d-axis inductance of the motor 19, and N pis the number of poles of the motor 19. In some embodiments, the maximum d-axis current I based on the regenerative current limit dmaxr Greater than the demagnetization current limit I d_demag . Carry out I dmaxr and I dmaxv The second algorithm 300 also maximizes torque to ensure stability during dynamic braking events where the motor speed may become very high due to external impact events (e.g., the vehicle's wheels hitting a curb).

[0093] The MDR block 332 is configured to calculate the maximum d-axis current I based on the regenerative current limit as follows dmaxr . Depends on the scanning d-axis current I d The torque T based on the regenerative current limit r Is it less than the torque limit T based on voltage? v , based on the maximum d-axis current I of the regenerative current limit dmaxr It is calculated in one of two different ways. Fig.12 and Fig.13 Graphed in Figure 2.

[0094] According to the power equation, for a given regenerative current limit I rl , we can write it as:

[0095]

[0096] The discriminant of the above equation can be written as follows:

[0097]

[0098] By setting the discriminant equal to zero and for I d Solving it, we can determine the orthogonal axis current I with a real solution q The corresponding peak d-axis current I dp Hereinafter, the peak d-axis current I dp This is called the d-axis current value based on the absolute maximum regenerative current limit.

[0099]

[0100] Write the discriminant in quadratic form for I d Solve

[0101]

[0102] Solving the above quadratic equation yields two roots, and for our control purposes we always take I dPositive value of (according to the dq convention used here, I d Positive values ​​are considered to be field weakening).

[0103]

[0104] B Idp =2a 3 ω e ω m (L q -L d )K e

[0105]

[0106] The peak d-axis current I dp Substitute into the power equation and solve for the peak q-axis current I qp and the corresponding torque T rlp :

[0107]

[0108] A Iqp =a 2 R

[0109] B Iqp =a 2 ω e (L q -L d )I dp +aK e ω m

[0110]

[0111] (Use “–” for positive torque command and vice versa)

[0112] Therefore, the RCPT block 320 is based on the obtained I dp and I qp The torque T is limited based on the regenerative current. r Calculated as peak torque,

[0113] Now, I dp Substitute into the voltage equation and calculate I qv and the corresponding torque T r :

[0114]

[0115] B Iqv =aRK e ω m+2a 2 Rω e (L q -L d )I dp

[0116]

[0117] (Use "+" for positive torque command and vice versa)

[0118] Therefore, the VPT block 322 obtains the I dp and I qv The voltage-based torque limit T v Calculated as peak torque,

[0119] The MDR block 332 calculates the current-limited d-axis current I according to the following equation: dmaxr To meet the regenerative current limit I of the DC bus 12 rl

[0120]

[0121] In short, except when the system is operating in regenerative mode ( Figure 3 Quadrant II, IV) and output torque T e Limit to torque limit T based on regenerative current r In all cases, the current-limited d-axis current I dmaxr Allocation I dp When the system is operating in regeneration mode, and the output torque T e Limit to torque limit T based on regenerative current r When , the iterative solver is used to calculate the current-limited d-axis current I dmaxr Using an iterative solver, by sweeping I d And solve the problem of satisfying the regenerative current limit I rl The voltage equation and the power equation of I q , the iterative solver output d-axis current I ditr .

[0122] I used in scanning d The maximum and minimum values ​​of I are determined by setting the voltage equation q =0 to obtain.

[0123] This is shown below.

[0124]

[0125] B Idmm =-(2aKe ω m ω e L d )

[0126]

[0127] Solving the above quadratic equation,

[0128] (Use “+” for maximum I d And use "-" for minimum I d )

[0129] The MDA block 334 calculates the final maximum d-axis current I as follows dmaxf :

[0130]

[0131] In other words, when the system is operating in one of the first quadrant or the third quadrant (ie, when the system is drawing power from the DC bus), the MDA block 334 sets the final maximum d-axis current I dmaxf Set to the maximum d-axis current I based on the voltage dmaxr In other cases (ie, when the system is operating in one of the second quadrant or the fourth quadrant), the MDA block 334 sets the final maximum d-axis current I dmaxf Set to the maximum d-axis current I based on the voltage dmaxv and the maximum d-axis current I based on the regenerative current limit dmaxr The highest among.

[0132] The RCPT block 320 and the VPT block 322 use the final maximum d-axis current I dmaxf Calculate the torque T based on the regenerative current limit respectively r and voltage-based torque limit T v . Torque T based on regenerative current limitation r and voltage-based torque limit T v It is further arbitrated by the PTA block 324 to deliver the final peak torque T that satisfies all constraints. pk The final peak torque T pk The motor torque demand T is used by the TCL block 326 c The TCL block 326 generates a limited torque command T command , the limiting torque command T command is transmitted to a current command calculation block 312 , which may function similarly or identically to the current command calculation block 212 of the first algorithm 200 .

[0133] Figure 7Depicts the maximum d-axis current I used to calculate the regenerative current limit dmaxr Flow chart of method 400, the maximum d-axis current I dmaxr is the battery current I s Meet the regenerative current limit I rl The maximum value of the d-axis current that can be generated at the same time. Figure 7 The method 400 shown in the flowchart of FIG. 4 is performed by the MDR block 332 .

[0134] The method 400 includes, at step 402, solving the discriminant of the power equation to find the peak d-axis current I dp , the peak d-axis current I dp The inverter 124 provides the DC bus 12 with a regenerative current limit I that satisfies the DC bus 12. rl The battery current I s In other words, the peak d-axis current I dp The inverter 124 provides the DC bus 12 with a current less than or equal to the regenerative current limit I rl The battery current I s The d-axis current.

[0135] The method 400 further includes, at step 404, converting the peak d-axis current I dp Substitute into the power equation to find the corresponding torque T based on regenerative current limitation rp This step 404 may use the RCPT block 320 or a similar algorithm or calculator to calculate the peak d-axis current I obtained at step 402. dp to execute.

[0136] The method 400 further includes, at step 406, setting the peak d-axis current I dp Substitute into the voltage equation to find the voltage limit constraint V of the DC bus 12 b The corresponding torque limit based on the peak voltage is T rv Step 406 may use the VPT block 322 or a similar algorithm or calculator to calculate the peak d-axis current I obtained at step 402. dp to execute.

[0137] Method 400 continues at step 408 by comparing the torque T based on the regenerative current limit obtained at step 404 . rp The peak voltage-based torque limit T obtained at step 406 rv , to determine the torque T based on the regenerative current limit rp Is it less than the torque limit T based on the peak voltage? rv A “yes” result of this comparison indicates that the regenerative torque that can be generated by the motor 19 is not constrained by the voltage limit V of the DC bus 12.b In this case, at step 410, the maximum d-axis current I dmaxr Set to the peak d-axis current I dp A “no” result of the comparison at step 408 indicates that the regenerative torque that can be generated by the motor 19 is constrained by the voltage limit V of the DC bus 12. b and the regenerative current limit I of the DC bus 12 rl In this case, at step 412, the maximum d-axis current I dmaxr At the same time, the voltage limit constraint V b and regenerative current limit I rl In some example embodiments, step 412 uses an iterative solver to determine the maximum d-axis current I dmaxr to determine the voltage limit constraint V b and regenerative current limit I rl The output d-axis current I ditr .

[0138] Figure 8 Graph depicting torque capabilities of an example motor control system according to aspects of the present disclosure. Fig. 9 A graph depicting d-axis current of an example motor control system according to aspects of the present disclosure.

[0139] Figure 10-19 Graphs showing various characteristics of an example motor control system according to aspects of the present disclosure and compared to a conventional design. Fig.10 The battery current I drawn from the DC bus 12 or supplied to the DC bus 12 by the inverter 124 is depicted. s A graph 1000 is shown in which one line shows a regenerative current limit I of -15A. rl system, while the other line shows the absence of regenerative current limiting I rl system. Fig.11 Graph 1100 depicts motor current of an example motor control system according to aspects of the present disclosure.

[0140] Fig.12 A graph 1200 of q-axis current versus d-axis current for an example motor control system according to aspects of the present disclosure is depicted. Specifically, the graph 1200 includes the q-axis current calculated by the power equation (ie, satisfying the regeneration current limit I rl The q-axis current of the voltage equation is kept smaller than the q-axis current calculated by the voltage equation (i.e., the voltage limit constraint V is satisfied). b q-axis current) curve. Fig.13A graph 1300 depicts q-axis current versus d-axis current for an example motor control system according to aspects of the present disclosure. The curves of graph 1300 are similar to those in graph 1200, except that at some points, the q-axis current calculated by the power equation (i.e., satisfying the regeneration current limit I rl The curve of the q-axis current) exceeds the q-axis current calculated by the voltage equation (i.e., satisfying the voltage limit constraint V b The value of the curve of q-axis current). Fig.12 and Fig.13 The MDR block 332 is used to calculate the maximum d-axis current I based on the regenerative current limit. dmaxr Two different situations.

[0141] Fig.14 The battery current I of an example motor control system according to aspects of the present disclosure is depicted. s 1400 versus speed (RPM). Specifically, the graph 1400 includes lines showing the regenerative current limits I of the system at -50A, -15A, and -5A. rl When the system has no regenerative current limit I rl Different battery current I s (It can also be achieved by limiting the regenerative current I s set very high to achieve this).

[0142] Fig.15 The maximum d-axis current I of an example motor control system according to aspects of the present disclosure is depicted. dmax Specifically, the graph 1500 shows the maximum d-axis current I dmax The maximum d-axis current I dmax Satisfy the demagnetization current limit I of motor 19 d_demag And operates the motor 19 at various supply voltages and torques (given in Newton meters (Nm)) including: 12V and 5Nm, 12V and 1Nm, and 5V and 1Nm.

[0143] Fig.16 Graph 1600 depicts the torque capability of an example motor control system according to aspects of the present disclosure. Fig.16 Included are curves of torque produced by a motor 19 at different speeds with an inverter 124 using a first algorithm 200 of the present disclosure (“1st algorithm”) and using a second algorithm 300 of the present disclosure (“2nd algorithm”). Fig.17 The battery current I of an example motor control system using the second algorithm 300 (“2nd algorithm”) of the present disclosure is depicted. sSpecifically, the graph 1700 includes the battery current I between the controller 16 and the DC bus 12 operated using the second algorithm 300. s In some embodiments, Fig.17 The battery current I shown in s The may be the same as those generated and / or consumed using the first algorithm 200 and / or those generated and / or consumed using conventional control methods.

[0144] Fig.18 A graph 1800 depicts motor current of an example motor control system according to aspects of the present disclosure. Specifically, Fig.18 Included are graphs of motor current in an electric machine 19 with an inverter 124 at different speeds using a first algorithm 200 (“1st algorithm”) of the present disclosure and a second algorithm 300 (“2nd algorithm”) of the present disclosure. Fig.19 d-axis current I of an example motor control system according to aspects of the present disclosure d Graph 1900. Specifically, Fig.19 The d-axis current I in the motor 19 at different speeds with the inverter 124 using the first algorithm 200 (“1st algorithm”) of the present disclosure and the second algorithm 300 (“2nd algorithm”) of the present disclosure are included. d curve.

[0145] exist Figures 20A-20B The method 2000 for controlling the operation of the motor 19 is shown in the flowchart of FIG. The method 2000 includes, at step 2002, calculating a voltage limit constraint V b The corresponding voltage-based torque limit Tv. Voltage limit constraint V b As the maximum voltage value for the DC bus 12. The voltage limit constraint V b It may depend on the characteristics of battery 10 and / or other aspects of the vehicle power system.

[0146] The method 2000 further includes, at step 2004, calculating the regenerative current limit I rl The corresponding torque T based on the regenerative current limit r . Regenerative current limit I rl The maximum current value allowed to be provided by the inverter 124 to the DC bus 12. rl The calculation of the regenerative current limit I rl The corresponding torque T based on the regenerative current limit r The step (step 2004) includes using the final direct-axis current limit Idmaxf Because the regenerative current limit I rl The peak torque occurs at the maximum d-axis motor current value, so the final direct-axis current limit I dmaxf can be substituted into the calculation for the corresponding q-axis current and then the torque T limited based on the regenerative current r in the equation.

[0147] The method 2000 also includes, at step 2006, when the torque T based on the regenerative current limit r Less than the voltage-based torque limit T v When the torque T is calculated based on the regenerative current limit r Defined torque limit T pk In some embodiments, when the torque T based on the regenerative current limit r Less than or equal to the voltage-based torque limit T v When the torque limit T pk The torque limit T is based on the current r definition.

[0148] The method 2000 also includes, at step 2008, commanding a plurality of switches within the inverter 124 to cause the motor 19 to generate a torque corresponding to the torque demand T c Corresponding and based on the torque limit T v Output torque T e This step 2008 may be performed by the inverter 124 under the command or guidance of the controller 130 .

[0149] The method 2000 further includes, at step 2009, commanding the plurality of switches within the inverter 124 to direct the direct axis current I d Adjust to not exceed the maximum d-axis current I dmax . Maximum d-axis current I dmax The demagnetization current of the motor 19 is limited to I d_demag or with the orthogonal axis current I q The corresponding peak d-axis current I dp This step 2009 may be performed by the inverter 124 under the command or guidance of the controller 130 .

[0150] In some embodiments, the direct axis current I d is limited to not exceed the demagnetization current limit I of the motor 19 d_demag For example, when the motor 19 is a permanent magnet synchronous motor (PMSM), the demagnetization current limit I d_demag The direct axis current I d The current may cause the permanent magnets in the motor 19 to become permanently demagnetized. In some embodiments, by limiting the direct axis current I dDoes not exceed the demagnetization current limit I of motor 19 d_demag Alternatively, in some embodiments, the direct-axis current I d Exceeding the demagnetization current limit I of the motor 19 d_demag For example, in an electric power steering (EPS) system, during a dynamic steering event (e.g., curb braking), the direct axis current I d The demagnetization current limit I may be exceeded d_demag Such applications may be relatively infrequent and / or of short duration, so that the risk of demagnetizing the motor 19 may be relatively low.

[0151] The method 2000 also includes, at step 2010, setting the torque command T command Calculated as the torque demand T c and torque limit T pk This step 2010 may be performed, for example, by the torque command limit (TCL) block 226 , 326 .

[0152] The method 2000 also includes, at step 2012, calculating and generating a torque command T command The initial d-axis current I′ corresponding to the motor d and the initial q-axis current I′ q , collectively referred to as I′ dq This step 2012 may be performed, for example, using a maximum torque per ampere (MTPA) calculation, such as by the MTPA block 240 of the first algorithm 200 or by the MTPA block 340 of the second algorithm 300 .

[0153] The method 2000 also includes, at step 2014, calculating and satisfying the regenerative current limit I of the DC bus 12. rl The inverter 124 corresponding to the modified d-axis current I″ d This step 2014 may be performed, for example, using a d-axis motor current search (RCDC) calculation based on the regenerated current, such as by the RCDC block 242 of the first algorithm 200 or by the RCDC block 342 of the second algorithm 300 .

[0154] like Fig. 20C As shown in the flowchart, the regenerative current limit I of the DC bus 12 is calculated and satisfied. rl The inverter 124 corresponding to the modified d-axis current I″ d Step 2014 may include several sub-steps. In some embodiments, the RCDC block 242 is configured to perform the following sub-steps.

[0155] Step 2014 includes calculating, at sub-step 2014A, a voltage limit constraint V bThe corresponding motor voltage limits the direct-axis current I dmaxv This sub-step 2014A may be performed, for example, by the maximum d-axis current for voltage constraint (MDV) block 330 .

[0156] Step 2014 also includes, at sub-step 2014B, based on the voltage-limited direct-axis current I dmaxv To set the expected d-axis current I d_prosp In some embodiments, the expected d-axis current I d_prosp is set equal to the voltage-limited direct-axis current I dmaxv In other words, the voltage limits the direct-axis current I dmaxv Can be used as an initial value in searches.

[0157] Step 2014 also includes, at sub-step 2014C, using the expected d-axis current I d_prosp Calculate the estimated battery current I generated by the inverter 124 s_est This sub-step 2014C corresponds to testing each expected d-axis current I d_prosp to determine if the search was successful.

[0158] Step 2014 also includes, at sub-step 2014D, increasing the expected d-axis current I d_prosp , until the expected d-axis current I d_prosp Corresponding to satisfying the regenerative current limit I rl The estimated battery current I s_est The expected d-axis current I d_prosp The increase can be in steps, and the steps can be fixed or variable.

[0159] The method 2000 further includes, at step 2016, calculating the regenerative current limit I rl The corresponding motor current limit is the direct axis current I dmaxr This step 2016 may be performed, for example, by the regenerative current constraint (MDR) block 332 of the second algorithm 300. Fig.20D As shown in the flowchart, the regenerative current limit I of the DC bus 12 is calculated. rl The corresponding motor current limit is the direct axis current I dmaxr The step (step 2016) may include several sub-steps. In some embodiments, the MDR block 332 is configured to perform the following sub-steps. Step 2016 and its corresponding sub-steps are also Figure 7 The method 400 shown in the flowchart is described.

[0160] Step 2016 includes, at sub-step 2016A, calculating the peak direct-axis current I dp, which corresponds to providing the DC bus 12 with a regenerative current limit I that is less than the DC bus 12 rl The battery current I s In some embodiments, the peak direct-axis current I dp Corresponding to providing the DC bus 12 with a regenerative current limit I that is less than or equal to the DC bus 12 rl The battery current I s The sub-step 2016A corresponds to the inverter 124. Figure 7 Step 402 of method 400 is shown in the flowchart of FIG.

[0161] Step 2016 also includes, at sub-step 2016B, using the peak direct-axis current I dp Calculate the regenerative current limit I of the DC bus 12 rl The corresponding torque T based on the regenerative current limit rp This sub-step 2016B corresponds to Figure 7 Step 404 of method 400 is shown in the flowchart of FIG.

[0162] Step 2016 also includes, at sub-step 2016C, using the peak direct-axis current I dp Calculate the voltage limit constraint V of the DC bus 12 b The corresponding torque limit based on the peak voltage is T rv This sub-step 2016C corresponds to Figure 7 Step 406 of method 400 is shown in the flowchart of FIG.

[0163] Step 2016 also includes, at sub-step 2016D, adjusting the torque T based on the regenerative current limit. rp Less than the torque limit T based on the peak voltage rv When the peak direct-axis current I dp The direct-axis current I used for current limitation dmaxr This sub-step 2016D corresponds to Figure 7 Step 410 of method 400 is shown in the flowchart of FIG.

[0164] Step 2016 also includes, at sub-step 2016E, adjusting the torque T based on the regenerative current limit. rp Not less than the torque limit T based on the peak voltage rv When the calculated value is less than the peak direct-axis current I dp The current limit of the direct axis current I dmaxr In some embodiments, sub-step 2016E includes calculating a value that is less than or equal to the peak direct-axis current I dp The current limit of the direct axis current I dmaxr This sub-step 2016E corresponds to Figure 7412 of the method 400 shown in the flowchart of . In some embodiments, this sub-step 2016E includes using an interval bisection method. However, other known numerical techniques involving interval solvers can be used to perform this sub-step 2016E.

[0165] The method 2000 also includes, at step 2018, using the current-limited direct-axis current I dmaxr Calculate the final direct-axis current limit I dmaxf This step 2014 may be performed, for example, by the maximum d-axis current arbitration (MDA) block 334 of the second algorithm 300 .

[0166] In some embodiments, and as Fig.20E As shown in the flow chart, the direct axis current I dmaxr Calculate the final direct-axis current limit I dmaxf The step (step 2018) also includes, at sub-step 2018A, limiting the final direct-axis current I dmaxf Set equal to the voltage-limited direct-axis current I dmaxv and the current-limited direct-axis current I dmaxr In other words, sub-step 2018 includes setting the voltage-limited direct-axis current I dmaxv and the current-limited direct-axis current I dmaxr The maximum of the two is used as the final direct-axis current limit I dmaxf This sub-step 2018A may be performed, for example, by the maximum d-axis current arbitration (MDA) block 334 of the second algorithm 300 .

[0167] The method 2000 further includes, at step 2020, calculating a voltage limit constraint V b The corresponding motor voltage limits the direct-axis current I dmaxv For example, this step 2020 may be performed by the maximum d-axis current for voltage constraint (MDV) block 330 of the second algorithm 300 .

[0168] Although the present disclosure has been described in detail only in conjunction with a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure may be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements that have not been described so far but correspond to the present disclosure in scope. In addition, although various embodiments of the present disclosure have been described, it should be understood that various aspects of the present disclosure may include only some of the described embodiments or a combination of various embodiments. Therefore, the present disclosure should not be considered to be limited by the foregoing description.

Claims

1. A control system for controlling the operation of a motor, comprising: an inverter operable to rectify current from an AC phase bus of the motor to a DC bus using switches; as well as A controller operable to: calculating a voltage-based torque limit corresponding to a voltage limit constraint of the DC bus; calculating a current-based torque limit corresponding to a regenerative current limit of the DC bus using an equation that relates total electrical power to a measured supply voltage of the DC bus and the regenerative current limit of the DC bus; calculating a final torque limit defined by the lesser of a current-based torque limit and a voltage-based torque limit; operating the switch to cause the motor to produce an output torque corresponding to the torque demand and in accordance with the final torque limit; and The switches are operated to regulate the direct-axis current to not exceed a maximum d-axis current defined by one of a demagnetization current limit of the motor or a peak d-axis current corresponding to a solution of an equation relating the total electrical power to a supply voltage of the DC bus and a regenerative current limit of the DC bus.

2. The control system according to claim 1, wherein: The maximum d-axis current is defined by the peak d-axis current corresponding to the solution of an equation relating the total electrical power to the supply voltage of the DC bus and the regenerative current limit of the DC bus.

3. The control system according to claim 1, wherein: The maximum d-axis current is defined by the demagnetization current limit of the motor.

4. The control system according to claim 3, wherein: The demagnetization current limit is equal to 4K e / (√3L d N p ), where K e is the anti-electromagnetic force constant, L d is the direct-axis inductance of the motor, and N p is the number of poles of the motor.

5. The control system according to claim 1, wherein: The controller is further operable to: calculating the torque command as the lesser of the torque demand and the torque limit; and An initial d-axis current and an initial q-axis current corresponding to the motor generating the torque command are calculated.

6. The control system according to claim 5, wherein: The controller is further operable to: A modified d-axis current corresponding to the inverter that satisfies the regenerative current limit of the DC bus is calculated.

7. The control system according to claim 6, wherein: The controller is further operable to: calculating a voltage-limited direct-axis current of the motor corresponding to a voltage-limit constraint of the direct-current bus; Set the expected d-axis current equal to the voltage-limited d-axis current; calculating an estimated battery current generated by the inverter using the expected d-axis current; as well as The expected d-axis current is increased until the expected d-axis current corresponds to an estimated battery current that satisfies the regeneration current limit.

8. The control system according to claim 1, wherein: The controller is further operable to: calculating a current-limited direct-axis current of the motor corresponding to a regenerative current limit of the DC bus; calculating a final direct-axis current limit using the current limited direct-axis current; and The resulting direct-axis current limit is used to calculate the current-based torque limit that corresponds to the regenerative current limit of the DC bus.

9. The control system according to claim 8, wherein: The controller is further operable to: calculating a voltage-limited direct-axis current of the motor corresponding to a voltage-limit constraint of the DC bus; and Wherein, calculating the final direct-axis current limit using the current-limited direct-axis current further comprises using the maximum of the voltage-limited direct-axis current and the current-limited direct-axis current as the final direct-axis current limit.

10. The control system according to claim 1, wherein: The electric machine is configured to perform at least one of: apply assist torque to a steering system of the vehicle, and control the steering system.

11. A method of controlling the operation of a motor, comprising: calculating a voltage-based torque limit corresponding to a voltage limit constraint of the DC bus; calculating a current-based torque limit corresponding to a regenerative current limit of the DC bus using an equation that relates total electrical power to a measured supply voltage of the DC bus and the regenerative current limit of the DC bus; calculating a final torque limit defined by the lesser of a current-based torque limit and a voltage-based torque limit; commanding a plurality of switches within the inverter to cause the electric machine to produce an output torque corresponding to the torque demand and in accordance with a final torque limit; as well as The plurality of switches are commanded to regulate the direct-axis current to not exceed a maximum d-axis current defined by one of a demagnetization current limit of the motor or a peak d-axis current corresponding to a solution of an equation relating total electrical power to a supply voltage of the DC bus and a regenerative current limit of the DC bus.

12. The method according to claim 11, wherein: The direct axis current is defined by the demagnetization current limit of the motor.

13. The method according to claim 11, further comprising: calculating a torque command as the lesser of a torque demand and a torque limit; as well as An initial d-axis current and an initial q-axis current corresponding to the motor generating the torque command are calculated.

14. The method according to claim 13, further comprising: A modified d-axis current corresponding to the inverter that satisfies the regenerative current limit of the DC bus is calculated.

15. The method according to claim 14, wherein: Calculating a modified d-axis current corresponding to the inverter that satisfies the regenerative current limit of the DC bus also includes: calculating a voltage-limited direct-axis current of the motor corresponding to a voltage-limit constraint of the direct-current bus; Setting the expected d-axis current based on the voltage-limited d-axis current; calculating an estimated battery current generated by the inverter using the expected d-axis current; and The expected d-axis current is increased until the expected d-axis current corresponds to an estimated battery current that satisfies the regeneration current limit.

16. The method according to claim 11, further comprising: calculating a current-limited direct-axis current of the motor corresponding to a regenerative current limit of the DC bus; calculating a final direct-axis current limit using the current limited direct-axis current; and Wherein calculating the current-based torque limit corresponding to the regenerative current limit of the DC bus includes using the resulting direct-axis current limit.

17. The method according to claim 16, further comprising: calculating a voltage-limited direct-axis current of the motor corresponding to a voltage-limit constraint of the direct-current bus; and Wherein, calculating the final direct-axis current limit using the current-limited direct-axis current further comprises using the maximum of the voltage-limited direct-axis current and the current-limited direct-axis current as the final direct-axis current limit.

18. The method according to claim 16, wherein: Calculating the current limit of the motor corresponding to the regenerative current limit of the DC bus also includes: calculating a peak direct-axis current corresponding to the inverter providing a battery current to the DC bus that is less than a regenerative current limit of the DC bus; Calculate the torque based on the regenerative current limit corresponding to the regenerative current limit of the DC bus using the peak direct axis current; Using the peak direct-axis current, calculate a peak voltage-based torque limit corresponding to a voltage limit constraint of the DC bus; When the torque based on the regenerative current limit is less than the torque limit based on the peak voltage, using the peak direct-axis current as the direct-axis current for current limiting; and When the torque based on the regenerative current limit is not less than the torque limit based on the peak voltage, a value of the direct-axis current that is less than the current limit of the peak direct-axis current is calculated.

19. A method of controlling the operation of an electric motor, comprising: calculating a voltage-limited direct-axis current of the motor corresponding to a voltage-limit constraint of the direct-current bus; calculating a current-limited direct-axis current of the motor corresponding to a regenerative current limit of the DC bus; calculating a final direct-axis current limit as the maximum of a voltage-limited direct-axis current and a current-limited direct-axis current; as well as Switches within the inverter are commanded to cause the motor to produce output torque using a direct-axis current that satisfies a final direct-axis current limit.

20. The method according to claim 19, further comprising: calculating a peak direct-axis current corresponding to the inverter providing a battery current to the DC bus that is less than a regenerative current limit of the DC bus; Calculate the torque based on the regenerative current limit corresponding to the regenerative current limit of the DC bus using the peak direct axis current; Using the peak direct-axis current, calculate a peak voltage-based torque limit corresponding to a voltage limit constraint of the DC bus; When the torque based on the regenerative current limit is less than the torque limit based on the peak voltage, the peak direct-axis current is used as the direct-axis current for current limiting; as well as When the torque based on the regenerative current limit is not less than the torque limit based on the peak voltage, a value of the direct-axis current that is less than the current limit of the peak direct-axis current is calculated.

Images