Supply current management under motor current control with voltage saturation

Abstract

A system and method for improved anti-saturation is provided that minimizes supply current consumption under voltage saturated current control operation of a synchronous motor drive. The system and method use a voltage limit module and an anti-saturation module, the voltage limit module is configured to receive a pre-limit voltage command and generate a post-limit voltage command when the motor control system reaches a configured threshold, the anti-saturation module is configured to determine the voltage difference between the pre-limit voltage command and the post-limit voltage command, and calculate an anti-saturation feedback current using the voltage difference and a compensation gain selected to minimize the supply current. The compensation gain includes a gain matrix of values ​​selected to move the motor current trajectory toward a zero motor current vector, and the anti-saturation module multiplies the gain matrix value by the voltage difference. The anti-saturation feedback current and the input current command are then added and provided as input to a controller.

Description

Technical Field

[0001] The present application relates generally to motor control systems, more particularly to managing supply current in a motor control system under voltage saturation conditions, and more particularly to motor control systems used in electric machines such as electric power steering (EPS) systems. Background Art

[0002] EPS systems typically use an electric motor drive to provide steering assist torque to the driver. Typically, torque control of an electric motor drive system using a permanent magnet synchronous motor (PMSM) is performed indirectly by regulating the motor current. In general, current control of the motor current is performed using a feedback control architecture that uses a field oriented control (FOC) technique with measured current in a synchronous rotating reference frame. Feedback control typically exhibits good steady-state tracking performance, fast dynamic response, high bandwidth, and satisfactory disturbance rejection. Therefore, feedback current control is typically used to control multi-phase AC motors (e.g., PMSM). Summary of the invention

[0003] According to one or more illustrative embodiments, a motor control system is provided for preventing controller windup and managing supply current in a voltage saturation state. The motor control system includes: a voltage limit module configured to receive a pre-limit voltage command and generate a post-limit voltage command when the motor control system reaches a selected voltage limit corresponding to a configured threshold value, the configured threshold value being used to limit a voltage applied to a motor controlled by the motor control system; and an anti-windup module configured to determine a voltage difference by subtracting the post-limit voltage command from the pre-limit voltage command, and calculate an anti-windup feedback current using the voltage difference and a compensation gain selected to minimize the supply current.

[0004] According to one or more illustrative embodiments, a method for preventing controller saturation and managing supply current in a voltage saturation state in an electric motor is also provided. For example, the method includes: receiving a pre-limit voltage command by a voltage limit module in the motor control system and generating a post-limit voltage command when the motor control system reaches a selected voltage limit corresponding to a configured threshold value for limiting a voltage applied to a motor controlled by the motor control system; and determining a voltage difference by subtracting the post-limit voltage command from the pre-limit voltage command by an anti-saturation module in the motor control system, and calculating an anti-saturation feedback current using the voltage difference and a compensation gain selected to minimize the supply current.

[0005] According to other illustrative aspects of the systems and methods, the compensation gains include a gain matrix of values ​​selected to move a motor current trajectory of the motor toward a zero motor current vector, and the anti-windup module multiplies the gain matrix values ​​by the voltage difference.

[0006] According to another illustrative aspect of the systems and methods, the anti-windup module calculates the anti-windup feedback current using a calculation that includes scaling the difference using the following gain matrix:

[0007] Among them, K Add , K Adq , K Aqd and K Aqq is the anti-saturation parameter.

[0008] According to another illustrative aspect of the systems and methods, an anti-saturation feedback current is provided as feedback to an input current command of a motor control system to introduce feedback cross-coupling of a voltage difference into a current error.

[0009] According to another illustrative aspect of the system and method, the anti-windup feedback current and the input current command are summed and provided as inputs to an integral controller to generate a voltage command.

[0010] According to another illustrative aspect of the system and method, the input current command is further modified by adding a second feedback current based on a measured current of the electric motor.

[0011] According to illustrative aspects of the systems and methods, a pre-limiting voltage command is calculated based on back-EMF compensation and based on feedback of a measured current of the electric motor.

[0012] An exemplary steering system is provided, the steering system having an electric motor that generates an amount of torque corresponding to a limited voltage command and a controller that receives an input current command and generates a voltage command for the motor. The controller includes: a voltage limit module configured to receive a voltage command corresponding to a pre-limit voltage command and generate a post-limit voltage command when the motor control system reaches a selected voltage limit corresponding to a configured threshold, the configured threshold being used to limit the voltage applied to the motor; and an anti-saturation module configured to determine a voltage difference by subtracting the post-limit voltage command from the pre-limit voltage command, and calculate an anti-saturation feedback current using the voltage difference and a compensation gain selected to minimize supply current. The anti-saturation feedback current modifies the input current command of the controller to prevent controller saturation in the motor control system and minimize supply current consumption under current control with voltage saturation.

[0013] According to an illustrative aspect of the steering system, the anti-windup feedback current is calculated by scaling the difference between the post-limiting voltage command and the pre-limiting voltage command. For example, the difference is scaled using the following gain matrix: Among them, K Add , K Adq , K Aqd and K Aqq is the anti-saturation parameter.

[0014] According to another illustrative aspect of the steering system, the input current command is further modified by a second feedback current based on a measured current of the electric motor.

[0015] 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

[0016] The subject matter regarded as the invention 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 invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0017] Figure 1 depicts an example electric power steering system according to one or more illustrative embodiments;

[0018] Figure 2 is an example schematic diagram of a motor control system according to an illustrative embodiment;

[0019] Figure 3 is a phasor diagram of a motor according to an illustrative embodiment;

[0020] Figure 4 is an example block diagram of a motor control system including an anti-windup compensator module according to an illustrative embodiment;

[0021] Figure 5 is an example block diagram of an anti-windup module according to an illustrative embodiment; and

[0022] Figure 6 is an example block diagram of a motor control system having an improved anti-windup compensator module that minimizes supply current in a voltage saturation state in accordance with an illustrative embodiment. DETAILED DESCRIPTION

[0023] 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 groups) and memories that execute one or more software or firmware programs, combinational logic circuits, and / or other suitable components that provide the functionality. It is understood that the submodules described below may be combined and / or further subdivided.

[0024] Referring now to the accompanying drawings, the technical solution will be described with reference to specific embodiments, rather than limiting thereof. Figure 1 is an illustrative embodiment of an electric power steering system (EPS) 40 suitable for implementing the disclosed embodiments. The steering mechanism 36 is a rack and pinion system and includes a rack (not shown) located within a housing 50 and a pinion (also not shown) located below a gear housing 52. When the operator input, hereinafter represented as a steering wheel 26 (e.g., a handheld 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 a 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 wheels 44 (only one shown).

[0025] Electric power steering assistance 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), hereinafter indicated as motor 19. The controller 16 is powered by a vehicle power supply 10 via line 12. The controller 16 receives a vehicle speed signal 14 representing 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 supplies a position signal 20 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 signal ω may be measured or calculated. m The motor speed can be measured and calculated as ω m For example, the motor speed ω m can be calculated as the change in motor position θ measured by the 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 speed can be derived from the motor position as the rate of change of position with respect to time. It should be appreciated that there are many well-known methods for performing the derivative function.

[0026] When 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 that is related to the amount of twist on the torsion bar. Although this is one type of torque sensor, any other suitable torque sensing device used in conjunction with known signal processing techniques will suffice. In response to various inputs, the controller sends a command 22 to the electric 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.

[0027] It should be noted that while the disclosed embodiments are described with reference to motor control for electric steering applications, it should 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 valve control, fluid pumps, 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, reference will be made only to motors without limitation.

[0028] In the depicted control system 24, the controller 16 uses torque, position, speed, etc. to calculate the command 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 an output command signal in response thereto, in this example, for example, to the motor 19. The controller 16 is configured to generate a corresponding voltage from an inverter (not shown), which can be optionally combined with the controller 16 and referred to as the controller 16 in this article, so that when applied to the motor 19, the desired torque or position is generated. In one or more examples, the control system 24 operates in a feedback control mode, like a current regulator, to generate the command 22. Alternatively, in one or more examples, the control system 24 operates in a feedforward control mode to generate the command 22. Since 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 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, resolvers, synchronizers, encoders, and the like, as well as combinations comprising at least one of the foregoing. The position encoder outputs a position signal 20 indicating the angular position of the steering shaft 51 , thereby outputting the angular position of the motor 19 .

[0029] The desired torque may be determined by one or more torque sensors 28 transmitting a torque signal 18 indicative of the applied torque. One or more illustrative embodiments include such a torque sensor 28 and the torque signal 18 therefrom 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.

[0030] In one or more examples, the temperature sensor 23 is located at the motor 19. Preferably, the temperature sensor 23 is arranged to directly measure the temperature of the sensing portion of the motor 19. The temperature sensor 23 transmits a temperature signal 25 to the controller 16 for processing and compensation as provided herein. Typical temperature sensors include thermocouples, thermistors, thermostats, etc., and combinations including at least one of the foregoing sensors, which, when properly placed, provide a calibrated signal proportional to a specific temperature.

[0031] Position signal 20, speed signal 21 and torque signal 18 are applied to controller 16. Controller 16 processes all input signals to generate values ​​corresponding to each signal, and obtains rotor position value, motor speed value and torque value that can be used for processing in the algorithm specified in this article. Measurement signals such as the above are also linearized, compensated and filtered together as desired to enhance the characteristics or eliminate undesirable characteristics of the acquired signal. For example, the signal can be linearized to increase the 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.

[0032] In order to perform the specified functions and desired processing, and thus perform calculations (e.g., identification of motor parameters, control algorithms, etc.), the controller 16 may include, but is not limited to, processors, computers, DSPs, memories, storage devices, registers, timing, interrupts, communication interfaces, and input / output signal interfaces, etc., and combinations including at least one of the foregoing. For example, the controller 16 may include input signal processing and filtering to achieve accurate sampling and conversion or acquisition of such signals from the communication interface. Additional features of the controller 16 and certain processes therein are discussed in detail later herein.

[0033] Figure 2 1 depicts a block diagram of a motor control system according to one or more embodiments. The motor control system 100 may be part of a steering system 40, or may be any other machine that uses a motor to cause displacement, torque generation, etc. As depicted, the power supply 10 provides a supply voltage V to the motor 19. B. In some embodiments, power source 10 is a 12 volt battery. However, it should be understood that other types of power sources may also be used. In one or more examples, inverter 122 is connected to motor 19 via multiple connections 132 (e.g., three connectors). In some embodiments, motor 19 is a multi-phase permanent magnet synchronous motor (PMSM). In the examples described herein, motor 19 is considered to be a three-phase PMSM, but it should be noted that in other examples, motor 19 can be a multi-phase motor. Controller 16 is connected to motor 19 via an inverter.

[0034] The controller 16 receives a motor torque command 136 from a torque control system 134 (eg, a steering control system). The controller 16 includes control logic 134 and 38 for sending a motor voltage command based on the torque command to the motor 19 via the inverter 122 .

[0035] Figure 3 Continue to refer Figure 2 , represents a phasor diagram 200 of a motor control system, wherein the commanded voltage is limited by a direction-holding voltage limiter according to one or more embodiments. Figure 3 In the graph, the vertical axis represents the voltage magnitude of the direct axis (d axis), and the horizontal axis represents the voltage magnitude of the orthogonal axis (q axis). Figure 1 and Figure 2 The motor 19 shown in FIG. 1 can be operated so that the motor voltage command V R The size (in Figure 3 V org ) exceeds the capability of the inverter 122. Specifically, the inverter 122 may have an input source voltage limit V max (marked as V DC ),exist Figure 3 It is shown in as the size of the arc extending between the direct axis (d-axis) and the orthogonal axis (q-axis).

[0036] In order to set the motor voltage command V R Within the operating parameters of the inverter 122, V org .like Figure 3 As shown, the motor voltage command V R can be limited by less than or equal to V max By V new Therefore, V new Within the sourcing capabilities of the inverter 122. The voltage vector V org and V new The direction angle is Figure 3 Also expressed as angle δ org and δ new . Limiting voltage vector Vorg and V new , in order to preserve V org The direction angle (i.e., δ org =δ new ).

[0037] When the controller 16 calculates a voltage command (transient or steady state) that exceeds the voltage limits of the system, the voltage command is limited to the maximum available battery voltage, and the states (or elements of the controller having memory), such as the states of the integrators, become incorrect because they do not conform to the originally calculated non-limited or pre-limited voltage commands. If the saturation condition persists for a long period of time, the states of the controller may become significantly incorrect. When the system returns to the linear operating range, the states may return to the correct values ​​after a certain amount of time, depending on how long the saturation condition persisted and the post-saturation conditions. This condition (known as controller saturation) can produce poor overall control system performance and instability.

[0038] Therefore, it is desirable to include an anti-windup (AW) device / assembly to improve the performance of a motor control system, and thereby improve an EPS system utilizing the motor control system.

[0039] In addition, particularly in the case of the EPS system 40 being one of the primary electrical loads in the vehicle energy network, it is desirable that the EPS system 40 be equipped with the ability to actively monitor and control supply current consumption. Such monitoring and control of supply current consumption is driven, among other reasons, by the need to protect the vehicle electrical network, particularly when the vehicle electrical network is in poor health. For example, during sudden voltage changes (which may be caused by internal errors in the vehicle electrical network) sharp transients in the supply current drawn by the EPS system 40 can cause further deterioration of the health of the electrical network. When the supply voltage suddenly drops, the motor current control system in the EPS control loop exhibits voltage command saturation, which will activate an anti-saturation control device, which can be implemented to manage the dynamics of the entire control system.

[0040] Existing anti-windup devices / techniques attempt to maximize motor torque or current production under saturation conditions. In other words, the goal of existing anti-windup techniques is to minimize motor current tracking error when the controller 16 enters a voltage saturation state, in addition to managing controller saturation. The goal of maximizing torque or current is directly in conflict with the goal of minimizing supply current overshoot, because minimizing supply current overshoot requires minimizing motor torque and current.

[0041] The technical solution described herein solves such technical challenges by minimizing the supply current consumption in the voltage saturation state while providing anti-saturation function. The technical solution described herein causes the motor current control system to follow a current trajectory that ends at a zero motor current vector or more generally in two (e.g., all) directions towards a state of lower current vector magnitude. This results in minimizing the supply current in voltage saturation because the supply current decreases as the motor current decreases.

[0042] Figure 4 is a block diagram of an electric motor drive system according to one or more embodiments. The depicted electric motor drive system (which may also be referred to as a motor control system) includes a motor control module 30, which is implemented by the controller 16, for example, and includes a voltage limiting module 316, an anti-saturation module 301, among other submodules, to control the operation of the motor 19. It should be noted that although the modules are depicted separately, in one or more examples, one or more of the depicted modules may be combined or separated differently than shown.

[0043] like Figure 4 As shown, the motor control module 30 implemented by the controller 16 includes several other sub-modules, such as a back electromotive force (BEMF) voltage compensation module 302, a proportional integral (PI) controller 365 (including compensation modules 306 and 310, and an integration module 308), a modification module 320, a subtraction module 304 and addition modules 312, 314 and 610.

[0044] Figure 4 The depicted motor 19 shows an example plant controlled by the controller 16. That is, the motor 19 receives an actual motor voltage command V M The actual motor voltage command V M Based on the motor voltage command V R The actual motor voltage command V M can be limited by the limit module 316, depending on the motor voltage command V R Whether the inverter 122 or other power source of the motor 19 exceeds its capability. The motor 19 generates torque and current (i.e., draws or outputs current I A , this current is the reference above Figures 1 to 3 The instantaneous power consumption equation of the electric motor drive system can be expressed as follows:

[0045] Here, V DC is the input voltage from battery 10, R DC is the resistance of the electric motor drive system, I Sis the current input to the electric motor drive system, and where V d 、V q is the d / q motor voltage, I d ,I q is the d / q motor current. In one or more embodiments, the voltage value is measured in volts and the current value is measured in amperes.

[0046] The following equation defined in the d / q axis coordinate system describes the plant transfer function of the plant of the motor 20 (using the line to neutral definition):

[0047]

[0048]

[0049]

[0050] Among them, V d 、V q is the d / q motor voltage (in volts), I d ,I q is the d / q motor current in amperes, L d , L q is the d / q axis motor inductance (in Henrys), R is the motor circuit (motor plus controller) resistance (in ohms), K e is the motor BEMF constant (in volts / rad / s), ω m is the mechanical motor speed (in rad / s), T e is the electromagnetic motor torque (in Nm).

[0051] In some embodiments, the limiter module 316 is a direction-maintaining voltage limiter that maintains the original phase angle while reducing the amplitude to the maximum available voltage. However, other voltage limiters can be used for the limiter module 316 that modify both the magnitude and angle of the voltage command. The output of the limiter module 316 is represented by V M Indicates the limited voltage command.

[0052] Considering multiple objectives and constraints (e.g., minimum losses and supply voltage limits), the current command generator ( Figure 4 (not shown) converts the torque command into a current command. In one or more examples, a current command (I R). The electromagnetic torque specified in equation (4) is nonlinear, indicating that the torque generated by utilizing the magnetic field from the permanent magnets is related to the rotor saliency (L d With L q The difference between q and I d A suitable choice of generates the sum of the reluctance torques.

[0053] In addition, the flux linkage of the controlled object can be expressed as:

[0054]

[0055] λ q =L q I q (Equation 6)

[0056] Note that the d-axis flux linkage includes the flux λ due to the permanent magnets m and the opposing flux component due to the d-axis motor current. The voltage equation can be restated in terms of flux linkage as:

[0057]

[0058]

[0059] In steady state, the voltage equation becomes

[0060] V d =ω e λ q +I d R (Equation 9)

[0061] V q =-ω e λ d +I q R (Equation 10)

[0062] The motor 19 and the controller 16 together form a closed-loop system with a certain frequency response characteristic. As can be understood, the frequency response of the closed-loop system is controlled by a set of model equations that define a transfer function that converts the input current command I R Converted to output current I M In other words, the controller 16 sends a command based on the input current I R The actual motor voltage command V generated M To adjust the output current I M I M is the current that is measured and fed back to the controller 16 .

[0063] Figure 4 The modification module 320 shown in FIG. 1 converts the measured feedback current I from the motor 19 into M Based on the measured feedback current I M , the modification module 320 changes the output current I A The d-axis component I d and the q-axis current component I q Decoupling of changes.

[0064] Figure 4 The compensation modules 306 and 310 depicted in FIG. 1 constitute a matrix-valued (or multi-dimensional) PI controller 365 that compensates the command current I R and the measured current I M The difference between E , to control the motor 19. The compensation module 306 uses the differential current I E (determined by the subtraction module 304) to generate a proportional voltage command V P The compensation module 306 and the integration module 308 together generate an integrated voltage command V I The adding module 312 combines the voltage command V P and V I To generate a voltage command V C . Proportional voltage command V P And the integrated voltage command V I is determined in such a way that the combined voltage command V C When applied to the motor 19, the total current to the current transfer function has a specific desired order. Note that I R ,I M ,I E 、V P 、V I and V C Each of has a d-axis component and a q-axis component. R ,I M ,I E 、V P 、V I and V C Represents vectors, rather than scalar values, each consisting of d-axis and q-axis signals (quantities).

[0065] Compensation module 306 is a proportional controller and compensation module 310 is an integral controller, both of which together serve as part of PI controller 365. Proportional compensation module C PIn addition to providing a beneficial trade-off between the motor input disturbance transfer function behavior and the current measurement noise transfer function behavior, it also helps configure the frequency response of the closed-loop system when a first-order type response is required. When a higher-order transfer function (e.g., third order) is required, a different configuration from the PI controller 365 is used. For example, only the integrator module 308 and the compensation module (C I )308, without using a proportional compensator (C P ) 306. In this case, the output of the PI controller 365 is simply V I , which can be further compensated by the BEMF compensator 302 to generate the PI controller output V R .

[0066] As used herein, the term "module" or "sub-module" refers to an application-specific integrated circuit (ASIC) that executes one or more software or firmware programs, a combination of logic circuits, an electronic circuit, a processor (shared, dedicated or grouped) and a memory and / or other suitable components that provide the described functionality. When implemented in software, the module or sub-module may be implemented in a memory as a non-transitory machine-readable storage medium that can be read by a processing circuit and stores instructions that are executed by the processing circuit to perform the method. In addition, Figure 4 The modules and sub-modules shown in any other figure or in this document may be combined and / or further divided. The software may be written in any form of programming language (including compiled or interpreted languages) and may be deployed in any form, including as a stand-alone program or as a module, component, subroutine or other unit suitable for a computing environment.

[0067] In some embodiments, controller 16 is a feedback controller with closed-loop control logic. That is, the output current of motor 19 is fed back to controller 16, which uses the feedback to adjust the output of motor 19. M When fed back to the controller 16, controller saturation may occur, where the motor voltage command V R May exceed the actual motor voltage command V M Due to the saturation condition that results in this situation, this may lead to instability in the motor control system, which is a technical challenge that the technical solution described in this article solves.

[0068] Control systems are typically designed to meet a set of linear performance indicators, but control systems typically use actuators (e.g., inverters) with operating limitations. Controller saturation may occur when the controller 16 generates a control signal that exceeds the capabilities of the actuator, causing saturation. Under saturation conditions, the control signal (or state) applied to the controlled object is limited, and each component of the controller with memory is updated incorrectly. This situation may cause the controller with memory to accumulate large errors, and the controller can only restore the correct value after the system has been out of saturation and maintained in this state for a period of time. Therefore, when controller saturation occurs, the system may remain in a saturated state for a longer period of time than required, ultimately reducing overall performance. The technical solution described in this article solves such technical challenges by facilitating the prevention of controller saturation from occurring.

[0069] Furthermore, particularly in PMSM drive systems of EPS systems, the DC bus voltage is supplied by the vehicle battery 10. Typically, to fully exploit the capabilities of the PMSM, the drive system operates in a maximum torque per voltage (MTPV) mode, in which the PMSM can generate maximum torque at a given battery voltage. During operation close to the voltage limit, the actuator is more likely to saturate, particularly in the presence of parameter errors or if the motor control system is subject to external disturbances or faults. Figure 4 As shown, the technical solution described herein solves such technical challenges by using an anti-windup module 301 to facilitate preventing controller saturation from occurring.

[0070] As described in more detail below, the anti-saturation (AW) module 301 selectively detects a voltage saturation condition and converts the actual motor voltage command V M An accurate representation of the input to the motor control system is provided, thereby improving system performance. When the vector sum of the outputs of the current regulators of the d-axis current loop and the q-axis current loop is greater in magnitude than the available DC link voltage V DC When the voltage is saturated, the voltage may be saturated. The voltage saturation state can be expressed by the following equation:

[0071]

[0072] Continue to refer Figure 4, when the calculated command exceeds the operating range of the inverter 122, the AW module 301 implements anti-saturation in addition to the decoupled current control to ensure that the control state with memory characteristics is bounded. Typical anti-saturation algorithms feed the difference of the limited control signal and the original control signal to the input of the controller 16 via a linear decoupling compensator (usually static, i.e., does not contain dynamic terms). Alternatively, the typical AW algorithm limits the output of the compensation modules 306 and 310 based on the difference between the feedforward signal and the feedback signal. According to an illustrative embodiment, the improved AW module 301 described herein solves the technical challenges described herein by minimizing the supply current consumption in the voltage saturation state while providing the anti-saturation function.

[0073] From the above equation, we can see that the motor current I dq and (or) motor voltage V dq Both contribute to power consumption or supply current consumption.Thus, one or more embodiments facilitate controlling the total supply current by changing the trajectory of the voltage vector in a manner that reduces motor current.

[0074] Figure 5 Detail of the anti-saturation module 301 is depicted according to one or more embodiments. The anti-saturation module 301 includes an anti-saturation module or "M" module for supply current minimization (M), as shown at 530. At the subtraction module 525, the commanded voltage V R Subtract the limited voltage command V M , as shown below.

[0075] V C =V′ R -V′ M Equation (12)

[0076] The M module 530 is configured with a compensation gain that minimizes the supply current consumption. To minimize current consumption, when the commanded motor voltage (V R ) is not equal to the final (limited) voltage (V M ), the matrix implemented via the M module 530 causes the motor current trajectory to move towards a zero motor current vector direction, or more generally towards a state of lower current vector magnitude in all directions.

[0077] The M module 530 receives the voltage difference V C And calculate the anti-saturation feedback current I AW . Anti-saturation feedback current and current command I E The sum is input to the integral controller (308, 310) within the PI controller 365. The M module 530 uses one or more configurable parameters based on the voltage difference V CCalculate the anti-saturation feedback current. In one or more examples, the parameters are configured to be related to the voltage difference V C The values ​​in the matrix to be multiplied.

[0078] To further explain the operation, a simplified embodiment of the AW module 301 is described next. Figure 6 A block diagram of an electric motor drive according to one or more embodiments is depicted. It should be noted that Figure 6 Depicted from Figure 4 In the depicted embodiment, the voltage limiter 316 is a direction-maintaining voltage limiter. Anti-windup action is performed by feeding back the scaled error (difference) to the input of the integral compensator or integral controller (366) through the static gain matrix (530). The scaled error is the voltage command (V R ) and the voltage command after limiting (V M ) is the vector difference between .

[0079] For simplicity, a 1-DOF current controller is depicted, but it should be understood that in other embodiments, the controller may have 2, 3, ... n degrees of freedom. In this case, the M module 530 includes four gain parameters for limiting the front (V R ) and after limiting (V M ) between the voltage difference V c The feedback cross coupling introduces current error (I E ). The current vector of the proposed anti-saturation scheme is expressed as follows:

[0080] I T =(C P +H+K I +P -1 ) -1 K I I R +(C P +H+K I +P -1 ) -1 (J+K I C A )(V R -V M ) Equation (13)

[0081] In the above equation (12), I T Indicates the actual motor current output.

[0082] By scaling the vector difference between the pre-limiting voltage command and the post-limiting voltage command, the AW module 301 limits the input and output of the integral controller 366 when the voltage limiter 316 is activated (or when the motor control system reaches a voltage limit). It should be noted that the voltage limiter 316 is activated only when the voltage command from the adder 314 exceeds the configured threshold value, which is used to limit the voltage applied to the motor 19. When the motor control system 100 settles to a steady state, the modified input of the integrator 308 is zero, while the output remains constant. Because the integral controller 366 is always in operation, the motor control system 100 transitions from unsaturated to saturated in a seamless and smooth manner.

[0083] Assuming accurate decoupling via the state feedback compensator (320) and precise back-EMF compensation (302) using a disturbance feed-forward term, the motor current can be expressed in the s-domain as follows.

[0084]

[0085] In steady state, the final modified current can be written as:

[0086]

[0087] Therefore, according to the equation, by choosing the anti-saturation compensator gain K Add , K Adq , K Aqd and K Aqq , the steady-state value of the motor current can be changed when the voltage error is non-zero (i.e., under voltage saturation operation). For example, under all conditions, K Adq and K Aqq A positive value of I Aq The other gains can be similarly selected and adjusted to make the motor current I Tq and I Td Both tend to lower values, which in turn reduces the supply current during voltage saturation operation. Therefore, the anti-saturation compensator gain K of the M module 530 is Add , K Adq , K Aqd and K Aqq is configured to reduce the supply current during voltage saturation operation. In addition, the linear gain may be replaced by any arbitrary mathematical function (which may be linear or non-linear in nature) that helps to reduce both motor currents simultaneously under voltage saturation operation.

[0088] The technical solution described herein helps to minimize the supply current consumption under the voltage-saturated current control operation of the synchronous motor drive. The technical solution described herein solves the technical challenges related to the saturation of the motor control system. The technical solution described herein improves the existing anti-saturation technology because the existing solutions are developed using steady-state models and therefore inherently assume that voltage saturation (transient or steady-state) will not occur. In the event of voltage saturation, the existing technology will not be able to control the supply current behavior because the anti-saturation compensator dominates the motor current tracking behavior that ultimately determines the supply current change. Therefore, the technical solution described herein provides improved anti-saturation by minimizing the supply current consumption under the voltage-saturated current control operation of the synchronous motor drive.

[0089] Continue to refer Figure 6 According to one or more embodiments, improved anti-saturation operations may be performed by the controller 16. As can be appreciated from the present disclosure, the order of operations within the method is not limited to Figure 6 Rather, the invention is not performed in the order shown, but may be performed in one or more alternative orders as applicable according to the present disclosure.

[0090] The method includes using the limiting module 316 to obtain the pre-limit voltage command (V R ) Calculate the voltage command after limiting (V M The limiting module 316 determines whether the pre-limiting voltage command exceeds a predetermined threshold of the maximum voltage command to be applied to the motor 19. If the threshold is exceeded, the anti-windup module 301 is activated and the pre-limiting and post-limiting voltage commands (V R and V M ) is input to the anti-saturation module 301.

[0091] The value obtained from the anti-saturation module 301 is used as the feedback current I AW is fed back to modify the current command I input to the PI controller 365 E , the PI controller 365 generates a voltage command that is input to the voltage limit module 316. The process including at least the above operations is continuous.

[0092] The resulting voltage command from the voltage limiting module 316 is applied to the motor 19. The voltage command is generated based on the modified current command. It should be noted that the output current from the motor 19 is also used in at least two separate feedback loops - one loop is used to generate the pre-limiting voltage command (V R ), and the other loop is used to generate the input current command (I E ).

[0093] Although the present invention has been described in detail with reference to only a limited number of embodiments, it should be readily understood that the present invention is not limited to the disclosed embodiments. Rather, the present invention can be modified to include any number of variations, modifications, substitutions, or equivalent arrangements not described herein but commensurate with the spirit and scope of the present invention as described. In addition, although a plurality of embodiments of the present invention have been described, it should be understood that a plurality of schemes of the present invention may include only some of the described embodiments. Therefore, the present invention should not be considered to be limited by the foregoing description.

Claims

1. A motor control system for preventing controller saturation and managing supply current in a voltage saturation state, the motor control system include: a voltage limit module configured to receive a pre-limit voltage command and generate a post-limit voltage command when the motor control system reaches a selected voltage limit corresponding to a configured threshold value for limiting a voltage applied to a motor controlled by the motor control system; and An anti-saturation module is configured to determine a voltage difference by subtracting the post-limiting voltage command from the pre-limiting voltage command and calculate an anti-saturation feedback current using the voltage difference and a compensation gain selected to minimize supply current, thereby preventing the controller from saturating and minimizing the supply current in the voltage saturation state.

2. The motor control system according to claim 1, in, The compensation gains include a gain matrix of values ​​selected to move a motor current trajectory of the motor toward a zero motor current vector, and the anti-windup module multiplies the gain matrix values ​​by the voltage difference.

3. The motor control system according to claim 1, in, The anti-saturation module calculates the anti-saturation feedback current using a calculation that includes scaling the voltage difference using a gain matrix defined as follows: Among them, K Add , K Adq , K Aqd and K Aqq is the anti-saturation parameter.

4. The motor control system according to claim 1, in, The anti-saturation feedback current is provided as feedback to an input current command of the motor control system to introduce feedback cross-coupling of the voltage difference into a current error.

5. The motor control system according to claim 4, in, The anti-windup feedback current and the input current command are summed and provided as input to an integral controller to generate a voltage command.

6. The motor control system according to claim 5, in, The input current command is further modified by adding a second feedback current based on a measured current of the electric motor.

7. The motor control system according to claim 1, in, The pre-limiting voltage command is calculated based on back electromotive force (BEMF) compensation and based on feedback of a measured current of the electric motor.

8. A method for preventing controller saturation in an electric motor and managing supply current in a voltage saturation state, the method include: receiving a pre-limit voltage command and generating a post-limit voltage command by a voltage limit module in the motor control system when the motor control system reaches a selected voltage limit corresponding to a configured threshold for limiting a voltage applied to a motor controlled by the motor control system; and An anti-saturation module in the motor control system determines a voltage difference by subtracting the post-limiting voltage command from the pre-limiting voltage command, and calculates an anti-saturation feedback current using the voltage difference and a compensation gain selected to minimize the supply current, thereby preventing the controller from saturating and minimizing the supply current in the voltage saturation state.

9. The method according to claim 8, in, The compensation gains include a gain matrix of values ​​selected to move a motor current trajectory of the motor toward a zero motor current vector and further include multiplying the gain matrix values ​​by the voltage difference by the anti-windup module.

10. The method according to claim 8, in, Calculating the anti-saturation feedback current includes using a calculation including scaling the voltage difference using a gain matrix defined as follows: Among them, K Add , K Adq , K Aqd and K Aqq is the anti-saturation parameter.

11. The method according to claim 8, further comprising: include: The anti-saturation feedback current is provided as feedback to an input current command of the motor control system to introduce feedback cross-coupling of the voltage difference into a current error.

12. The method according to claim 11, further comprising: include: The anti-windup feedback current and the input current command are added and the resulting total current is provided as input to an integral controller to generate a motor voltage command.

13. The method according to claim 12, further comprising: include: The input current command is modified by adding a second feedback current based on a measured current of the electric motor.

14. The method according to claim 8, in, The pre-limiting voltage command is calculated based on back electromotive force (BEMF) compensation and based on feedback of a measured current of the electric motor.

15. A steering system, include: an electric motor that generates an amount of torque corresponding to the limited voltage command; A controller receives an input current command and generates a voltage command for the motor, the controller comprising: a voltage limit module configured to receive a voltage command corresponding to a pre-limit voltage command and generate a post-limit voltage command when the motor control system reaches a selected voltage limit corresponding to a configured threshold for limiting a voltage applied to the motor; and An anti-saturation module is configured to determine a voltage difference by subtracting the post-limiting voltage command from the pre-limiting voltage command and calculate an anti-saturation feedback current using the voltage difference and a compensation gain selected to minimize supply current, thereby preventing the controller from saturating and minimizing the supply current in a voltage saturation state.

16. The steering system according to claim 15, in, The compensation gains include a gain matrix of values ​​selected to move a motor current trajectory of the motor toward a zero motor current vector, and the anti-windup module multiplies the gain matrix values ​​by the voltage difference.

17. The steering system according to claim 15, in, The anti-saturation module calculates the anti-saturation feedback current using a calculation that includes scaling the voltage difference using a gain matrix defined as follows: Among them, K Add , K Adq , K Aqd and K Aqq is the anti-saturation parameter.

18. The steering system according to claim 15, in, The anti-saturation feedback current is provided as feedback to an input current command of the motor control system to introduce feedback cross-coupling of the voltage difference into a current error.

19. The steering system according to claim 18, in, The anti-windup feedback current, the input current command, and a second feedback current based on a measured current of the motor are summed and provided as inputs to an integral controller to generate a voltage command.

20. The steering system according to claim 15, in, The pre-limiting voltage command is calculated based on back electromotive force (BEMF) compensation and based on feedback of a measured current of the electric motor.

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