Motor control device

Abstract

A motor control device is provided that reduces the computational burden of current command values ​​and improves processing speed. The combination of intersection points selected from the intersection points of two curves plotted on an orthogonal coordinate plane of the dq axes—the maximum efficiency curve, the minimum current curve, the minimum voltage curve, the current limit circle, the voltage limit ellipse, and the constant torque curve—is determined as valid intersection points for current commands. Then, the combinations of intersection points are arranged as the current state and the transition destination state, thereby creating a state transition table with set transition conditions. Based on the positional relationship on the curves of the intersection points corresponding to the transition destination state when a transition occurs from any intersection point corresponding to the current state according to the transition conditions, a current command value for the electric motor (15) is generated.

Description

Technical Field

[0001] This invention relates to a motor control device for driving and controlling an electric motor. Background Technology

[0002] Motors such as embedded magnet motors (IPMs) utilize reluctance torque to operate at high torque and high speeds, thus serving as traction motors and driving sources for electric vehicles, hybrid vehicles, and the like. On the one hand, this IPM-ification complicates the control of traction motors; on the other hand, to achieve maximum efficiency, the motor needs to be operated up to its voltage and current limits.

[0003] Various methods have been proposed for controlling the maximum efficiency of motors. For example, Non-Patent Document 1 discloses a control algorithm that uses the maximum torque / current control (MTPA) curve and the maximum torque / fluidity control (MTPF) curve.

[0004] Patent Document 1 discloses the following control: based on the current command obtained from the intersection of curves on the xy plane calculated by numerical analysis, the operating mode is set sequentially from the low speed region to the high speed region to maximum torque / current (MTPA) operation, field weakening (CLVL) operation, and maximum torque / voltage (MTPV) operation.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-226270

[0008] Non-patent literature

[0009] Non-patent literature 1: "Magnetic reluctance torque application motor" (IEEE / Ohm Corporation (2016 / 1)) Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] In motor control, for this control method to be applied to actual products, it needs to be able to operate stably under all voltage / current limiting conditions. However, both Patent Document 1 and Non-Patent Document 1 only show a portion of the situations that may cause voltage / current limiting.

[0012] For example, the motor current command must meet the voltage and current limits (condition i) to avoid control failure, the command torque must meet the command torque (condition ii) to satisfy the upper-level command, and finally the condition of maximizing motor efficiency (condition iii) must be met.

[0013] Non-Patent Document 1 illustrates maximum efficiency control, but it lacks any explanation based on mathematical formulas, thus failing to cover all situations where maximum efficiency control cannot be implemented. Furthermore, Non-Patent Document 1 proposes an optimal ammeter method, but the generation of the table for the current command value becomes costly.

[0014] Patent Document 1 lacks a description of maximizing efficiency. For example, it does not consider the case where there is no intersection between the voltage-limiting ellipse and the current-limiting circle, resulting in a failure to cover all voltage / current limiting conditions (it does not cover cases where both voltage and current limits are not met). Furthermore, since the selected intersection point is determined solely based on the reference rotor speed, it also considers the possibility that the solution of the numerical analysis method (two-dimensional Newton's method) may disappear due to variations in torque command or voltage and current limit values, leading to unstable current output.

[0015] The present invention was made in view of the above-mentioned problems, and its object is to generate an optimal motor current command for all voltage and current limiting conditions, including cases where voltage and current limiting conditions are not met.

[0016] Methods for solving problems

[0017] As a means to achieve the above objectives and solve the above problems, the invention has the following structure. Specifically, the exemplary first invention of this application is a motor control device that drives a motor in a dq-axis orthogonal coordinate system via current vector control. This motor control device includes the following units: a unit for determining a combination of intersection points from the intersection points of two curves selected from the maximum efficiency curve, minimum current curve, minimum voltage curve, current limiting circle, voltage limiting ellipse, and constant torque curve in the dq-axis orthogonal coordinate plane that are effective as current commands; a unit for arranging the combination of intersection points as a current state and a transition destination state in the row and column directions, respectively, to create a state transition table that sets transition conditions from the current state to the transition destination state; and a unit for generating current command values ​​for the motor based on the positional relationship on the curves of the intersection points corresponding to the transition destination state when a transition occurs from any intersection point corresponding to the current state according to the transition conditions.

[0018] The exemplary second invention of this application is a motor control method that drives a motor by current vector control in an orthogonal coordinate system of dq axes. This motor control method includes the following steps: determining a combination of intersection points selected from the maximum efficiency curve, minimum current curve, minimum voltage curve, current limiting circle, voltage limiting ellipse, and constant torque curve in the orthogonal coordinate plane of dq axes that are effective as current commands; arranging the combination of intersection points as a current state and a transition destination state in the row and column directions respectively to create a state transition table that sets transition conditions from the current state to the transition destination state; and generating a current command value for the motor based on the positional relationship on the curves of the intersection points corresponding to the transition destination state when a transition occurs from any intersection point corresponding to the current state according to the transition conditions.

[0019] Invention Effects

[0020] According to the motor control device of the present invention, by using a state transition table, a stable motor control current command can be output in all cases, including cases where there is no intersection point that is valid as a current command, based on two curves selected from a plurality of curves. Attached Figure Description

[0021] Figure 1 This is a block diagram illustrating the overall structure of a motor control device according to an embodiment of the present invention.

[0022] Figure 2 It is a diagram showing the positional relationship of multiple curves on a coordinate plane orthogonal to the dq axes.

[0023] Figure 3 This is a diagram illustrating the selection range of current command values ​​based on multiple curves.

[0024] Figure 4 This is a diagram illustrating various possible ranges of current commands based on voltage and current limits.

[0025] Figure 5 This is a diagram showing the combination that is effective as a current command.

[0026] Figure 6 It is a state transition table that sets the conditions for transitioning from the current state to the destination state.

[0027] Figure 7 This is a flowchart illustrating the calculation process of the command current in the motor control device of this embodiment.

[0028] Figure 8 This is a diagram showing a variation of a combination that is effective as a current command.

[0029] Figure 9 Is with Figure 8 The state transition table corresponding to the combination.

[0030] Figure 10 This is a flowchart illustrating an example of selecting the current output intersection without using a state transition table.

[0031] Figure 11 This is a block diagram showing the structure of a modified motor control device. Detailed Implementation

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0033] <Structure of Motor Control Device>

[0034] Figure 1 This is a block diagram illustrating the overall structure of a motor control device according to an embodiment of the present invention. Figure 1 The motor control device 1 shown includes a motor control unit 10, a motor drive unit 5 that provides a specified drive current to an electric motor 15, which is the object of control, and so on. The motor control unit 10 is composed of, for example, a microprocessor responsible for the overall control of the motor control device 1. It is a central control unit (CPU) that performs feedback control (F / B control) and so on. In this feedback control, the current value is fed back in such a way that the current flowing in the electric motor 15 is consistent with the target current.

[0035] The current command unit 2 uses the state transition table described later to generate two-phase command current values ​​(target current values) with d-axis and q-axis components, namely the d-axis current command value Id* and the q-axis current command value Iq*, based on the indicated torque (torque command value) Tq, the rotational speed ω of the electric motor 15, etc.

[0036] In addition to storing the motor control program executed by the motor control unit 10, memory 3 also stores state transition tables, programs, etc., required for the implementation of state transitions, as described later. Memory 3 is, for example, a read-only memory (ROM). Memory 3 can be built into the motor control unit 10 or it can be external.

[0037] Subtractor 13a calculates the difference between the q-axis current command value Iq* and the q-axis current Iq output from coordinate transformation unit 28. Subtractor 13b calculates the difference between the d-axis current command value Id* and the d-axis current Id output from coordinate transformation unit 28.

[0038] The q-axis PI control unit 16a performs PI (proportional + integral) control by making the difference between Iq* and Iq converge to zero, and calculates the command value of the q-axis voltage, i.e., the q-axis voltage command value Vq*. Meanwhile, the d-axis PI control unit 16b performs PI (proportional + integral) control by making the difference between Id* and Id converge to zero, and calculates the command value of the d-axis voltage, i.e., the d-axis voltage command value Vd*.

[0039] The coordinate transformation unit 17 calculates the voltage applied to the motor based on the voltage command values ​​Vq* and Vd* of the q-axis and d-axis and the rotation angle θ of the electric motor 15. That is, the coordinate transformation unit 17, which has a two-phase / three-phase conversion function, converts the q-axis voltage command value Vq* and the d-axis voltage command value Vd* into voltage command values ​​Vu*, Vv*, and Vw*, which are the voltage command values ​​for each of the three phases, based on the rotation angle θ.

[0040] The voltage command values ​​Vu*, Vv*, and Vw* after the three-phase conversion are input to the PWM signal generation unit 21. The PWM signal generation unit 21 increases or decreases the duty cycle of the PWM (Pulse Width Modulation) control signal according to these voltage command values, thereby generating the drive signal for the electric motor 15.

[0041] That is, the PWM signal generation unit 21 generates "on" / "off" control signals (PWM signals) for multiple semiconductor switching elements (FETs) constituting the inverter circuit 23 according to the voltage command value. These semiconductor switching elements correspond to each phase (u phase, v phase, w phase) of the electric motor 15.

[0042] Switching elements (FETs) are also known as power elements, such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors).

[0043] Alternatively, the PWM signal generation unit 21 can also be configured as a motor control integrated circuit (pre-driver IC) that is built into the motor drive signal generation and functions as a FET drive circuit, etc.

[0044] The inverter circuit 23 of the motor drive unit 5 is an AC motor drive circuit that generates power to drive the electric motor 15 based on the power supplied from the battery BT via the power relay 24. The electric motor 15 is, for example, a surface magnet motor (SPM) or an embedded magnet motor (IPM) and other vehicle traction motors. The power relay 24 is configured to cut off the power from the battery BT and may also be a semiconductor relay.

[0045] The motor drive current supplied to the motor 15 by the inverter circuit 23 is detected by a current detection unit 25, which is composed of current sensors arranged accordingly. The current detection unit 25 uses, for example, an amplifier circuit composed of an operational amplifier to detect the DC current flowing in the shunt resistor for detecting the motor drive current.

[0046] The output signal (current detection signal) from the current detection unit 25 is input to the A / D conversion unit (ADC) 27. Here, the analog current value is converted into a digital value by the A / D conversion function of the ADC 27, and the three-phase currents Iu, Iv, and Iw obtained by this conversion are input to the coordinate transformation unit 28.

[0047] The coordinate transformation unit 28, which has a three-phase / two-phase conversion function, outputs the q-axis current Iq and the d-axis current Id based on the rotation angle θ detected by the rotation angle sensor 29 and the three-phase currents Iu, Iv, and Iw. That is, the coordinate transformation unit 28 calculates the d-axis current and the q-axis current based on the actual current of the motor (actual q-axis current and actual d-axis current).

[0048] <Optimal Efficiency Control>

[0049] The motor control device of this embodiment needs to meet the commanded torque and speed and maximize efficiency in motor control. Therefore, as a first condition, the voltage / current limit must be met, and as a second condition, the efficiency must be maximized within the voltage / current limit range.

[0050] Therefore, the x-axis is designated as the Iq component, and the y-axis as the Id component. Four curves are defined on the current dq-axis plane (an orthogonal coordinate plane to the dq-axis) where the positive direction of the y-axis is defined as the direction of the weak magnetic field: a minimum current curve, a minimum voltage curve, a current limiting circle, and a voltage limiting ellipse. The region enclosed by these four curves satisfies the first condition mentioned above. Furthermore, to satisfy the second condition, the point within the aforementioned region that overlaps with or is closest to the constant torque curve and the maximum efficiency curve is output as the current command value.

[0051] The constant torque curve (CT curve, or simply CT (Constant Torque)) is the trajectory of orthogonal coordinates (x, y) satisfying a constant torque T, and can be represented by equation (1). In equation (1), ξ m η is the permanent magnet coefficient, set to 1 in motors containing permanent magnets and 0 in motors without permanent magnets. Δη is the maximum value of the dimensionless motor constant η. max With minimum value η min difference.

[0052]

[0053] The constant torque curve is a hyperbola, but in any case where the torque command value T > 0 or T < 0, it is a meaningful current command within the range of y ≥ 0.

[0054] The locus of (x, y) where the current norm |i1| is constant is i1 2 =x 2 +y 2 Let the current limiting function be LA(x, y) = x 2 +y 2 If the upper limit of the current norm is set to |i max |Then the current limiting circle has a radius of |i centered at the origin. max | The circle. Therefore, the curve represented by equation (2) is called the current-limited circle or LA (Limited Ampere) curve.

[0055] x 2 +y 2 =i max 2 ...(2)

[0056] Let the locus of (x, y) that makes the voltage norm |v1| constant be set as the voltage constraint function, given by LV(x, y) = (x - η) min ωy+ξ m ) 2 +(y+η max ωy) 2 This indicates that if the upper limit of the voltage norm is set to |v... max |, then the voltage limiting ellipse (LV (Limited Voltage) curve) can be represented by equation (3).

[0057] (x-η min ωy+ξ m ω) 2 +(y+η max ωx) 2 =v max 2 …(3)

[0058] The minimum current norm curve (also known as the minimum current curve or MA (Minimum Ampere) curve) shown in Equation (4) is defined by deriving the current norm minimization condition relative to constant torque.

[0059] (ξ m +Δηy)y-Δηx 2 =0…(4)

[0060] Similarly, the voltage norm minimum curve (also known as the voltage minimum curve, MV (Minimum Voltage) curve) shown in Equation (5) is defined by deriving the voltage norm minimum condition relative to constant torque.

[0061] -{Δηx+(ξ m +Δηy)η min ω}(x-η min ωy+ξ m ω)

[0062] +{(ξ m +Δηy)-Δηη max ωx}(y+η max ωx)=0

[0063] …(5)

[0064] The maximum efficiency curve (also known as the ME (Maximum Efficiency) curve) is derived, for example, from analytical or measured data, using mathematical formulas that include them, as follows.

[0065] (ξ m +Δηy)y-Δηx 2 +K 2 (ω){-η max 2 Δηx 2 +η min (ξ m +Δηy)(η min y-ξ m )}=0

[0066] …(6)

[0067] In equation (6), K(ω) is the current-independent coefficient, and the hysteresis loss coefficient is set as k. h Set the eddy current loss coefficient to k. e In this case, it can be defined as follows.

[0068]

[0069] The aforementioned minimum current curve, minimum voltage curve, and maximum efficiency curve are upward-pointing hyperbolas with the y-axis as the principal axis. The maximum efficiency curve is a quadratic curve described using the motor's iron losses.

[0070] Figure 2 The positional relationship of the five curves (MV curve, ME curve, MA curve, LA curve, LV curve) in the orthogonal coordinate plane of the dq axis is shown. Figure 2The horizontal axis is the iq axis (x-axis), and the vertical axis is the id axis (y-axis). Regarding the magnitude relationship of each curve (the value of the y-coordinate relative to the same x-coordinate), the relationship MV curve > ME curve > MA curve holds true.

[0071] Within the range y > 0, the MA, MV, and ME curves do not intersect. On the other hand, the MA curve and the LA curve must intersect, and the MV curve and the LV curve must also intersect.

[0072] Next, the method for selecting the current command value in the motor control device of this embodiment will be explained. Figure 2 In the diagram, the areas inside MA, MV, LA, and LV (denoted by A) satisfy the voltage and current limits, and the CT curve satisfies the commanded torque. There are multiple points that satisfy these conditions, but by balancing the commanded torque and maximum efficiency at the intersection of the ME and CT curves and selecting this point as the current command value, motor efficiency can be maximized. Therefore, satisfying the voltage and current limits is a necessary condition in selecting the current command value.

[0073] Furthermore, referring to Figure 3 The range of current command values ​​is explained. Figure 3 (a) represents the case where the torque command value T > 0. Figure 3 (b) corresponds to the case where the torque command value T < 0, and the above-mentioned quadratic curves become the limiting conditions for the current command value.

[0074] like Figure 3 As shown, the range enclosed by the MV and MA curves, which are two parabolas, represents the effective operating point for current output. The opening of this range is limited by the LA and LV curves. Therefore, the range enclosed by these curves... Figure 3 The area marked with a slash is the range within which the current command can be output, which is the range where all four conditions must be met: within the LV curve, within the LA curve, above the MA curve, and below the MV curve.

[0075] The condition for outputting the commanded torque is when the CT curve based on the commanded torque is included within the aforementioned range. If the torque command is large but does not include a CT curve, the point that maximizes the torque within the voltage and current limits is selected as the current command value. If a CT curve is included, the point where the optimal efficiency intersects with the ME curve or the point closest to the ME curve is selected as the current command value.

[0076] The current command based on voltage and current limits may range as follows: Figure 4As shown, there are 3 types in the voltage saturation stage (voltage always saturated, voltage partially saturated, and no voltage saturation), and 3 types in the current saturation stage (current always saturated, current partially saturated, and no current saturation), for a total of 9 types.

[0077] However, since there are no motors without limitations on either voltage or current, there will be no cases of voltage saturation or current saturation. Figure 4 Except for (g). Additionally, cases where there is no output range will be considered ( Figure 4 (j) is defined as NOVA (No cross voltage and Ampere). Figure 4 In each case, arrows indicate the direction of torque increase, and double circles (◎) indicate the point of maximum torque.

[0078] Furthermore, the intersections of the curves here are referred to by abbreviations connecting the intersecting curves. Specifically, the intersection of the maximum efficiency curve and the constant torque curve is called MECT, the intersection of the current limiting circle and the constant torque curve is called LACT, the intersection of the minimum current curve and the current limiting circle is called MALA, the intersection of the voltage limiting ellipse and the constant torque curve is called LVCT, the intersection of the minimum voltage curve and the voltage limiting ellipse is called MVLV, and the intersection of the voltage limiting ellipse and the current limiting circle is called LVLA.

[0079] like Figure 4 As shown, with only voltage limiting applied, the MVLV becomes the point of maximum torque. Figure 4 (a) and (d)), if it is only a current limitation, then MALA becomes the point of maximum torque. Figure 4 Under the constraints of both voltage and current, LVLA becomes the point of maximum torque. Figure 4 (b), (c), (e), (f)).

[0080] Regarding the CT curve, if it does not overlap with the current output range, the point of maximum torque is taken as the current command value. If the CT curve overlaps with the current output range, the point on the CT curve that is closest to the ME curve within the current output range is taken as the current command value.

[0081] Next, the method for selecting current command values ​​in the motor control device of this embodiment will be explained. The current command value is the intersection point of two curves selected from the six curves represented by equations (1) to (6) above. There are 15 combinations obtained by selecting two curves from these six curves, but the effective combination as a current command is as follows: Figure 5 As shown, it is limited to only 6 types: MECT, LVCT, LACT, MVLV, MALA, and LVLA.

[0082] The reason is that, as mentioned above, there is no intersection between MA, MV, and ME, and MALV, MVLA, MELV, MELA, MCT, and MVCT will not become effective current outputs. Additionally, sometimes LACT, LVCT, and LVLA do not have an intersection.

[0083] Therefore, it is possible to encompass all seven possible scenarios, including those where there is no intersection point effective as a current command. Thus, the motor control device of this embodiment treats these seven scenarios as states and uses... Figure 6 The state transition table shown is used to select the current command value.

[0084] exist Figure 6 In the state transition table, the combinations of intersections valid as current commands are arranged in the row and column directions as the current state and the destination state, respectively, and the transition conditions (C1 to C18) for moving from the current state to the destination state are set. The transition conditions are the judgment conditions used to move from any intersection to other intersections. These judgment conditions depend on the current intersection and are therefore called state transition machines. The × mark indicates no transition.

[0085] exist Figure 6 In the state transition table, MALA, MVLV, LVLA, and NOVA represent torque saturation states. Here, the torques of MVLV, MALA, and LVLA are defined as voltage saturation torque Tv, current saturation torque Ta, and voltage / current saturation torque Tva, respectively.

[0086] Although they do not depend on the current state, they will vary based on parameters such as speed and current limits. The three states that can follow torque commands are MECT, LVCT, and LACT, with MECT being the most efficient. |v|, |i|, and ME represent the voltage norm, current norm, and ME function output of the current state, respectively.

[0087] The transitions between torque saturation states (MALA, MVLV, LVLA, NOVA) are determined by the relationship between current limiting, voltage limiting, and speed. The transformation that has occurred (LVCT, In MVLV and LVLA, there is one possible destination for the change when the torque of Tv or Ta becomes unsaturated.

[0088] On the other hand, when Tva becomes unsaturated, it is assumed that there are two possible destinations for the transition: LVCT and LACT. The velocity ω at the shared point of the ME curve, LV curve, and LA curve is considered. MELVA To determine which direction to take.

[0089] Additionally, it may also include a protection unit that, in the absence of an effective intersection point for current command, applies at least one or both of overcurrent and overvoltage protection to the motor. Thus, in the absence of an output range, it can protect the motor from overheating and prevent damage or malfunction of control components.

[0090] Next, the output operation of the current command in the motor control device of this embodiment will be explained. Figure 7 This is a flowchart illustrating the calculation process of the current command value in the motor control device of this embodiment.

[0091] exist Figure 7 In step S11, the motor control unit 10 defines the aforementioned six quadratic curves on an orthogonal coordinate plane of the dq axis. Specifically, the MV curve, ME curve, MA curve, LA curve, LV curve, and CT curve are plotted on the xy plane. In the next step S13, the intersection point of two curves selected from the six curves plotted in step S11 is defined. The combinations of these intersection points, as described above, include a total of seven combinations: six that are effective as current commands and seven combinations that are not effective as current commands.

[0092] In step S15, the combinations of intersections that are effective as the current commands obtained in step S13 above are arranged in the row direction and column direction as the current state and the transition destination state, respectively, to form a system to which transition conditions are attached. Figure 6 The state transition table shown.

[0093] In step S17, the motor control unit 10 sets an initial state (e.g., starting from MECT). In step S19, it determines whether the transition conditions described later are met. If the transition conditions are met, in step S21, according to the state transition table created in step S15 above, a state transition is implemented to move from a predetermined intersection point to another intersection point, using command torque, motor speed, etc., as transition conditions. Thus, the transfer destination (transition destination) is screened, and the point that maximizes torque within the voltage / current limit range is selected as the current command. If multiple current commands can be output, the command torque is satisfied, and the output is performed with maximum efficiency.

[0094] Thus, as long as the initial values ​​(x, y) satisfy the transition conditions, the process of implementing other state transitions is repeated (steps S19 and S21). If the transition conditions are not met ("No" in step S19), in step S23, the motor control unit 10 calculates the current command value at the intersection of the current states. Here, for example, the two-variable Newton's method, algebraic solution method, etc., are used to calculate the current command value (current command value Iq* on the q-axis and current command value Id* on the d-axis) that satisfies the condition of maximizing efficiency. The current command value at each intersection can be derived by selecting two curves and solving a quadratic equation in two variables.

[0095] In step S25, it is determined whether the state transition process has ended. If it has not ended, the process returns to step S19 and performs state transition processing based on other transition conditions.

[0096] Next, the verification results of implementing optimal efficiency control based on state transition table in the motor control device of this embodiment will be explained.

[0097] In the implementation of state transitions using a state transition table, there are three termination points: MALA, MVLV, and LVLA. Here, we verify the control scenarios in the torque increase and decrease directions. Furthermore, we also examine the termination points in... Verify the changes between them.

[0098] In addition, the following explanation will use "positive" for all command torque values, but the same applies if the command torque is "negative".

[0099] <Example 1 of State Transition>

[0100] Here, as Example 1 of the state transition, the case where the termination point is MALA is verified. For example, in the direction where the torque increases from 0, it advances on the ME curve (MECT) while satisfying the commanded torque and optimal efficiency. Intersecting with the LA curve, current saturation occurs (|i|≥|i...). max |: Figure 6 The transition condition is C2). Then, while satisfying the commanded torque, it advances on the LA curve (LACT).

[0101] Torque saturation (T*≥Ta: transition condition C7) terminates at the point MALA, which intersects with the MA curve. Although the maximum torque is at MALA, the command torque is not satisfied at MALA. Transition condition C7 is the condition where the orthogonal coordinates (x, y) of LACT are substituted into MA to become less than 0 (i.e., MA < 0).

[0102] Therefore, if torque saturation is eliminated in the direction of decreasing torque MALA (T* < Ta: transition condition C9), then the torque advances on the LA curve (LACT) while satisfying the commanded torque. Intersecting the ME curve (ME > 0: transition condition C6), the torque advances on the ME curve to implement optimal efficiency control (MECT). Furthermore, transition condition C9 is a condition where the orthogonal coordinates (x, y) of LACT are substituted into MA to become 0 or higher (i.e., MA > 0).

[0103] <Example 2 of State Transition>

[0104] When the termination point is MVLV, the scenarios differ between partial voltage saturation and constant voltage saturation. In the case of constant voltage saturation, the relationship between the ME curve and the LV curve can be considered in several ways.

[0105] Scenario A: Y intercept is ME > LV

[0106] Scenario B: The Y-intercept is LV≥ME, and the LV curve intersects the ME curve at two points.

[0107] Scenario C: The Y-intercept is LV≥ME, and the intersection points of the LV curve and the ME curve are 0 to 1.

[0108] In the case of partial current saturation, only scenario A described above applies.

[0109]

Scene A

[0110] In the direction of torque increase from 0, it advances along the ME curve (MECT) while satisfying the commanded torque and optimal efficiency. It intersects the LV curve, indicating voltage saturation (|v|≥|v). max |:Transition condition C1). Then, while satisfying the commanded torque, it advances on the LV curve (LVCT). When the torque saturates (T*≥T... v The transition condition (C4) terminates at the point MVLV, which intersects with the MV curve. The maximum torque is at MVLV, where the command torque is not satisfied. Specifically, transition condition C4 is the condition where the orthogonal coordinates (x, y) of the LVCT are substituted into MV to become 0 or greater (i.e., MV > 0).

[0111] In the direction from which the torque MVLV decreases, if torque saturation (T* < T) is eliminated v If the transition condition is C11, then the vehicle advances along the LV curve (LVCT) while satisfying the commanded torque. If the vehicle intersects the ME curve (ME < 0: transition condition C3), it advances along the ME curve to implement optimal efficiency control (MECT). Transition condition C11 is the condition where the orthogonal coordinates (x, y) of LVCT are substituted into MV to become less than 0 (i.e., MV < 0).

[0112] [Scene B]

[0113] Starting from the point where torque increases from 0, the path advances along the LV curve, beginning at the intersection of the y-axis and the LV curve (LVCT). This continues until the ME curve becomes inside the LV curve (|v|≤|v). max The output changes to MECT. Afterwards, because the ME curve becomes the outer edge of the LV curve again (|v|≥|v), max |:Transition condition C1), the output becomes LVCT, when torque saturation (T*≥T) v The transition condition is C4), and the process terminates at the point MVLV where it intersects the MV curve.

[0114] In the direction from which the torque MVLV decreases, if torque saturation (T* < T) is eliminated v If the transition condition is C11, then the system advances along the LV curve (LVCT) while satisfying the commanded torque. If the system intersects the ME curve (ME < 0: transition condition C3), it advances along the ME curve to implement optimal efficiency control (MECT), and the voltage of MECT saturates again (|v| ≥ |v). max |: Change condition C1), return to LVCT.

[0115] [Scene C]

[0116] In the direction of torque increase from 0, it advances along the LV curve (LVCT) while satisfying the commanded torque. When torque saturation occurs (T*≥T),... v The transition condition is C4), and the process terminates at the point MVLV where it intersects the MV curve.

[0117] In the direction from which the torque MVLV decreases, if torque saturation (T* < T) is eliminated v If the transition condition is C11, then the vehicle will advance on the LV curve (LVCT) while satisfying the command torque.

[0118] <Example 3 of State Transition>

[0119] With the termination point being LVLA, depending on whether the current or voltage of the MECT saturates first, there are the following two scenarios.

[0120] [Scenarios where current saturates first]

[0121] In the direction of torque increase from 0, it advances along the ME curve (MECT) while satisfying the commanded torque and optimal efficiency. It intersects the LA curve, where current saturation occurs (|i|≥|i). max|: Transition condition C2). Next, while satisfying the commanded torque, it advances along the LA curve (LACT). Intersecting the LV curve, voltage and torque saturate (T*≥Tva: Transition condition C8), terminating at LVLA. The maximum torque point is LVLA, where the commanded torque is not satisfied. Transition condition C8 is obtained by substituting the orthogonal coordinates (x, y) of LACT into LV to obtain v. max 2 The above conditions (i.e., voltage saturation) apply.

[0122] In the direction of decreasing torque LVLA, since T*<Tva and ω≤ω are satisfied when torque saturation is eliminated. MELVA (Transition condition C14) Therefore, while satisfying the commanded torque, it advances on the LA curve (LACT). When it intersects with the ME curve (ME>0: transition condition C6), it advances on the ME curve to implement optimal efficiency control (MECT).

[0123] [Scenarios where voltage saturates first]

[0124] When increasing torque from 0, the system advances along the ME curve (MECT) while satisfying the commanded torque and optimal efficiency. It intersects the LV curve, indicating voltage saturation (|v|≥|v). max |: Transition condition C1). Next, while satisfying the commanded torque, it advances along the LV curve (LVCT). Intersecting the LA curve, voltage and torque saturate (T*≥Tva: Transition condition C5), terminating at LVLA. The maximum torque point is LVLA, where the commanded torque is not satisfied. Transition condition C5 is obtained by substituting the orthogonal coordinates (x, y) of LVCT into LA to obtain i. max 2 The above conditions (i.e., current saturation).

[0125] In the direction of decreasing torque LVLA, since T* < Tva and ω > ω are satisfied when torque saturation is eliminated. MELVA (Transition condition C13) Therefore, while satisfying the commanded torque, it advances on the LV curve (LVCT). When it intersects with the ME curve (ME < 0: transition condition C3), it advances on the ME curve to implement optimal efficiency control (MECT).

[0126] Additionally, transformation conditions C13 and C14 can also replace ω. MELVA The sign used when substituting the orthogonal coordinates (x, y) of LVLA into ME is changed to LVCT if ME > 0, and to LACT if ME ≤ 0.

[0127] <Example 4 of State Transition>

[0128]

[0129] In the state terminating at the MVLV point, when the MVLV is saturated with current (|i|≥|i max |:Transition condition C12), the current output transitions to LVLA. Similarly, in the state terminating at the LVLA point, when the phase of LVLA leads the MV curve (ω>ω MVLVA Transition condition C16) changes the current output to MVLV. Alternatively, transition condition C16 is obtained by substituting the orthogonal coordinates (x, y) of LVLA into MV, resulting in a value greater than or equal to 0 (i.e., MV > 0). Transition condition C12 can also be set as ω ≤ ω obtained by reversing transition condition C16. MVLVA .

[0130] <Example 5 of State Transition>

[0131]

[0132] At the point terminating at MALA, when MALA is at voltage saturation (|v|≥|v) max When the transition condition C10 is met, the current output transitions to LVLA. Similarly, when the LVLA phase lags behind the MA curve (ω < ω), the current output transitions to LVLA. MALVA Transition condition C15 changes the current output to MALA. Alternatively, transition condition C15 is obtained by substituting the orthogonal coordinates (x, y) of LVLA into MA, resulting in a value below 0 (i.e., MA < 0). Transition condition C10 can also be set as ω ≥ ω obtained by reversing transition condition C15. MALVA .

[0133] <Example 6 of State Transition>

[0134] [NOVA Transformation]

[0135] The state where the voltage-limiting ellipse (LV) and the current-limiting circle (LA) do not intersect is represented by NOVA at velocity ω. NOVA The transition conditions are between LVLA and LVLA (transition conditions C17, C18). Since the current output does not satisfy both current and voltage requirements, the following two approaches can be considered.

[0136] (i) Prioritize overcurrent protection, making it the point on the y-axis that minimizes the absolute value of the voltage (y = i max )

[0137] (ii) Prioritize overvoltage protection and become the point on the y-axis that minimizes the absolute value of the current (as the solution of equation (8) obtained by substituting x = 0 into the LV curve, equation (9)).

[0138] (1+η min2 ω 2 )y 2 -2ξ m η min ω 2 y+ξ m ω 2 -v max 2 =0…(8)

[0139]

[0140] As explained above, when the motor control device of this embodiment determines the command current of the motor under voltage / current constraints, it uses a state transition table that sets the transition conditions from the current state to the destination state. The destination is determined based on the positional relationship of the current vector plane of each curve. At this time, the command value of the current vector is calculated with regard to the intersection of the two curves that are effective for the current command (current output) of the motor. This reduces the amount of calculation required for the current command value of the motor, thereby improving the processing speed and reducing the cost.

[0141] That is, in the method of selecting the current command value as described above and performing the calculation, the initial avoidance of... Figure 6 The state transition table shown includes processes without transition conditions marked with an ×, thus, for example, with... Figure 10 Compared to the process shown in the flowchart that judges the appropriateness of all intersections (i.e., also checks the conditions of the × mark in the state transition table each time), the processing speed is greatly improved. Furthermore, the method for calculating current command values ​​is applicable to all synchronous motors, regardless of whether there are magnets, whether it is a surface magnet motor (SPM), or an embedded magnet motor (IPM).

[0142] In addition, Figure 10 In this context, |Tcom| is the absolute value of the commanded torque, |W| is the absolute value of the current speed, Vlmt is the voltage limit value, Ilmt is the current limit value, V(MECT) is the MECT intersection voltage, I(MECT) is the MECT intersection current, T(MVLV) is the MVLV intersection torque, T(MALA) is the MALA intersection torque, T(LVLA) is the LVLA intersection torque, w_MALVA is the triple intersection speed of MA, LV, and LA, w_MVLVA is the triple intersection speed of MV, LV, and LA, and w_NOVA is the speed above |w_MALVA| that does not satisfy either the voltage limit ellipse or the current limit circle.

[0143] Furthermore, according to this embodiment, by also including the states that do not meet both the current condition and the voltage condition in the state transition table, useless calculations under conditions where no solution exists can be avoided, and the failure of the calculation of the intersection coordinates used for the current command can be prevented, thereby achieving control stabilization.

[0144] In other words, by considering the state where there is no output range in the selection of current command value, the state where there is no intersection between curves can be reliably excluded, thus avoiding the failure of current control.

[0145] Furthermore, even if parameters such as voltage limit, current limit, resistance, inductance, and linkage flux change, the system can be transformed to the appropriate state each time because state transition calculations are performed. Therefore, there are no omissions, leaks, or calculation failures. For example, even motors with magnetic saturation and drastic voltage fluctuations, such as those used in electric vehicle drive motors, can be controlled with maximum efficiency.

[0146] Furthermore, it can perform maximum efficiency control not only for copper losses but also for iron losses, which are the sum of hysteresis and eddy current losses, corresponding to optimal performance. Therefore, compared to existing control systems that rely on efficiency mapping, it can reduce operating time and alleviate the processing load on the machine.

[0147] The present invention is not limited to the above-described embodiments and can be modified in various ways.

[0148] <Variation Example 1>

[0149] In the motor control device of the above-described embodiment, the effective combination as a current command is as follows: Figure 5 The six combinations shown are not limited to these, but the combinations are not limited to these if the iron loss of the motor is not taken into account.

[0150] For example, to minimize copper loss, the MA curve can be used instead of the ME curve. In this case, there are 10 combinations of selecting two curves from the five curves after removing ME. Furthermore, under the above conditions, three combinations are eliminated, and LACT is not used to maintain minimum current. As a result, the effective combinations for current output are limited to... Figure 8 The five types shown are MCT, LVCT, MVLV, MALA, and LVLA.

[0151] Figure 9 It is a state transition table that interprets the above 5 cases as states, and adds 6 states as the current state and the destination state of the NOVA case where there is no output range in the combination. Figure 9 State transition tables, for example, are suitable for selecting the current command value required for the control of low-speed, high-current motors.

[0152] <Variation Example 2>

[0153] The motor control device in the embodiments of the present invention is not limited to Figure 1 The structure shown. In Figure 1 In the motor control device shown, feedback control is performed to make the target value consistent with the current detection value, but for example, it can also be performed as follows: Figure 11 As shown in the motor control device 1a, it employs a structure that performs feedforward control (F / F control) without comparing the current detection value with the target value.

[0154] The motor control unit 1a performs feedforward control based on the motor voltage equation. Therefore, the voltage command unit 4 of the motor control unit 10a calculates the d-axis voltage command value Vd and the q-axis voltage command value Vq according to the d-axis current command value Id and the q-axis current command value Iq generated by the current command unit 2, using the following voltage equation (10).

[0155]

[0156] In equation (10), Ld is the d-axis inductance of the motor, Lq is the q-axis inductance of the motor, R is the resistance of the stator coil (winding resistance), Φa is the linkage flux of the motor, and ω is the electric angular velocity, which are prepared by prior measurement or detection / inference during driving. Here, p is the differential operator.

[0157] Label Explanation

[0158] 1, 1a: Motor control unit; 2: Central control unit (CPU); 3: Memory; 4: Voltage command unit; 5: Motor drive unit; 10, 10a: Motor control unit; 15: Electric motor; 16a: q-axis PI control unit; 16b: d-axis PI control unit; 17, 28: Coordinate transformation unit; 21: PWM signal generation unit; 23: Inverter circuit; 24: Power relay; 25: Current detection unit; 27: A / D conversion unit (ADC); 29: Rotation angle sensor; BT: External battery.

Claims

1. A motor control device that drives a motor via current vector control in an orthogonal coordinate system of dq axes, wherein, The motor control device has the following components: Find the unit that is effective for current command among the intersection points of two selected curves in the orthogonal coordinate plane of the dq axis: the maximum efficiency curve, the minimum current curve, the minimum voltage curve, the current limiting circle, the voltage limiting ellipse, and the constant torque curve. The minimum current curve is a set of dq axis current action points that minimize the current norm relative to constant torque, divided by torque. The minimum voltage curve is a set of dq axis current action points that minimize the voltage norm relative to constant torque, divided by torque. The combinations of the intersection points are arranged in the row and column directions as the current state and the destination state, respectively, to form a unit of a state transition table that sets the transition conditions from the current state to the destination state; and A unit generates a current command value for the motor based on the positional relationship on the curve of the intersection point corresponding to the destination state of the transition when the transition occurs from any intersection point corresponding to the current state according to the transition conditions.

2. The motor control device according to claim 1, wherein, The state transition table includes states that do not have a valid intersection with the curve as the current state and the transition destination state.

3. The motor control device according to claim 2, wherein, The motor control device also has a protection unit that, in the absence of the effective intersection point, applies at least one or both of overcurrent protection and overvoltage protection to the motor.

4. The motor control device according to claim 1, wherein, The state transition table contains the following transitions: The first transition involves taking the coordinates of the intersection of the maximum efficiency curve and the constant torque curve as the current state, taking the specified current saturation as the transition condition, and taking the coordinates of the intersection of the current limiting circle and the constant torque curve as the transition destination state. The second transition involves taking the coordinates of the intersection of the current limiting circle and the constant torque curve as the current state, taking the specified torque saturation as the transition condition, and taking the coordinates of the intersection of the minimum current curve and the current limiting circle as the transition destination state. The third transition involves taking the coordinates of the intersection of the minimum current curve and the current limiting circle as the current state, taking the elimination of the specified torque saturation as the transition condition, and taking the coordinates of the intersection of the current limiting circle and the constant torque curve as the transition destination state. as well as The fourth transition involves taking the coordinates of the intersection of the current limiting circle and the constant torque curve as the current state, the intersection state with the maximum efficiency curve as the transition condition, and the coordinates of the intersection of the maximum efficiency curve and the constant torque curve as the transition destination state.

5. The motor control device according to claim 1, wherein, The state transition table contains the following transitions: The fifth transition involves taking the coordinates of the intersection of the maximum efficiency curve and the constant torque curve as the current state, taking the specified voltage saturation as the transition condition, and taking the coordinates of the intersection of the voltage limiting ellipse and the constant torque curve as the transition destination state. The sixth transition involves taking the coordinates of the intersection of the voltage limiting ellipse and the constant torque curve as the current state, taking the specified torque saturation as the transition condition, and taking the coordinates of the intersection of the minimum voltage curve and the voltage limiting ellipse as the transition destination state. The 7th transition takes the coordinates of the intersection of the minimum voltage curve and the voltage limiting ellipse as the current state, the elimination of the specified torque saturation as the transition condition, and the coordinates of the intersection of the voltage limiting ellipse and the constant torque curve as the transition destination state. as well as The eighth transition involves taking the coordinates of the intersection of the voltage limiting ellipse and the constant torque curve as the current state, the intersection state with the maximum efficiency curve as the transition condition, and the coordinates of the intersection of the maximum efficiency curve and the constant torque curve as the transition destination state.

6. The motor control device according to claim 1, wherein, The state transition table contains the following transitions: The ninth transition involves taking the coordinates of the intersection of the maximum efficiency curve and the constant torque curve as the current state, taking the specified current saturation as the transition condition, and taking the coordinates of the intersection of the current limiting circle and the constant torque curve as the transition destination state. The 10th transition takes the coordinates of the intersection of the current limiting circle and the constant torque curve as the current state, the specified torque saturation as the transition condition, and the coordinates of the intersection of the voltage limiting ellipse and the current limiting circle as the transition destination state. The 11th transition takes the coordinates of the intersection of the voltage limiting ellipse and the current limiting circle as the current state, takes the elimination of the specified torque saturation and the speed as the transition conditions, and takes the coordinates of the intersection of the current limiting circle and the constant torque curve as the transition destination state. as well as The 12th transition takes the intersection coordinates of the current limiting circle and the constant torque curve as the current state, the intersection state with the maximum efficiency curve as the transition condition, and the intersection coordinates of the maximum efficiency curve and the constant torque curve as the transition destination state.

7. The motor control device according to claim 1, wherein, The state transition table contains the following transitions: The 13th transition uses the coordinates of the intersection of the maximum efficiency curve and the constant torque curve as the current state, the specified voltage saturation as the transition condition, and the coordinates of the intersection of the voltage limiting ellipse and the constant torque curve as the transition destination state. The 14th transition takes the coordinates of the intersection of the voltage limiting ellipse and the constant torque curve as the current state, the specified torque saturation as the transition condition, and the coordinates of the intersection of the voltage limiting ellipse and the current limiting circle as the transition destination state. The 15th transition takes the coordinates of the intersection of the voltage limiting ellipse and the current limiting circle as the current state, takes the elimination of the specified torque saturation and the speed as the transition conditions, and takes the coordinates of the intersection of the voltage limiting ellipse and the constant torque curve as the transition destination state. as well as The 16th transition uses the coordinates of the intersection of the voltage limiting ellipse and the constant torque curve as the current state, the intersection with the maximum efficiency curve as the transition condition, and the coordinates of the intersection of the maximum efficiency curve and the constant torque curve as the transition destination state.

8. The motor control device according to claim 1, wherein, The state transition table contains the following transitions: The 17th transition takes the coordinates of the intersection of the minimum voltage curve and the voltage limiting ellipse as the current state, the specified current saturation as the transition condition, and the coordinates of the intersection of the voltage limiting ellipse and the current limiting circle as the transition destination state. as well as The 18th transition uses the coordinates of the intersection of the voltage limiting ellipse and the current limiting circle as the current state, the phase leading the minimum voltage curve as the transition condition, and the coordinates of the intersection of the minimum voltage curve and the voltage limiting ellipse as the transition destination state.

9. The motor control device according to claim 1, wherein, The state transition table contains the following transitions: The 19th transition takes the coordinates of the intersection of the minimum current curve and the current limiting circle as the current state, the specified voltage saturation as the transition condition, and the coordinates of the intersection of the voltage limiting ellipse and the current limiting circle as the transition destination state. as well as In the 20th transition, the coordinates of the intersection point of the voltage limiting ellipse and the current limiting circle are taken as the current state, the phase lags behind the current minimum curve as the transition condition, and the coordinates of the intersection point of the current minimum curve and the current limiting circle are taken as the transition destination state.

10. The motor control device according to claim 2, wherein, The state transition table contains the following transitions: The 21st transition is to take the state where the voltage limiting ellipse and the current limiting circle do not intersect as the current state, take the specified rotational speed as the transition condition, and take the coordinates of the intersection point of the voltage limiting ellipse and the current limiting circle as the transition destination state. as well as The 22nd transition involves taking the coordinates of the intersection of the voltage limiting ellipse and the current limiting circle as the current state, taking the specified rotational speed as the transition condition, and taking the state where the voltage limiting ellipse and the current limiting circle do not intersect as the transition destination state.

11. The motor control device according to any one of claims 1 to 10, wherein, The maximum efficiency curve is a quadratic curve described using the iron loss of the motor.

12. A motor control method, wherein a motor is driven by current vector control in an orthogonal coordinate system of dq axes, wherein, The motor control method has the following steps: Find the combination of intersection points that are effective for current commands from the intersection points of two selected curves in the orthogonal coordinate plane of the dq axis: the maximum efficiency curve, the minimum current curve, the minimum voltage curve, the current limiting circle, the voltage limiting ellipse, and the constant torque curve. The minimum current curve is a set of dq axis current action points that minimize the current norm relative to the constant torque, divided by torque. The minimum voltage curve is a set of dq axis current action points that minimize the voltage norm relative to the constant torque, divided by torque. The combinations of these intersection points are arranged in the row and column directions as the current state and the destination state, respectively, to create a state transition table that sets the transition conditions from the current state to the destination state; and Based on the positional relationship on the curve of the intersection point corresponding to the destination state of the transition when the transition occurs from any intersection point corresponding to the current state according to the transition conditions, a current command value for the motor is generated.

Images