Motor drive device and electric vehicle system

Abstract

Provided is a motor drive device that drives a motor by controlling torque generated by the motor based on a d-axis current and a q-axis current, the motor drive device including: a d-axis current command generation section that calculates a first d-axis current command; a current command correction section that generates a positive correction amount that is added to the first d-axis current command when a terminal voltage of the motor is equal to or greater than a prescribed value; and a voltage feedback control section that generates a negative correction amount that is added to the first d-axis current command to prevent the terminal voltage of the motor from exceeding a prescribed maximum output voltage, and controls the torque based on a second d-axis current command obtained by adding the positive correction amount and the negative correction amount to the first d-axis current command, and a q-axis current command.

Description

Technical Field

[0001] This invention relates to an electric motor drive device and an electric vehicle system using it. Background Technology

[0002] In the driving of three-phase synchronous motors (hereinafter sometimes referred to as "motors"), inverters that convert DC power to AC voltage are typically used. In this case, control is required to ensure that the inter-terminal voltage of the motor, which increases along with the motor's speed, does not exceed the inverter's maximum output voltage. This control is called field weakening control, and it regulates the inter-terminal voltage of the motor by circulating a current (hereinafter referred to as "field weakening current") that cancels out the stator linkage flux of the three-phase synchronous motor.

[0003] As a field weakening control method, feedback control (hereinafter referred to as "voltage feedback control") based on the deviation (discrepancy) between the inverter's maximum output voltage and the voltage applied to the motor is known. For example, Patent Document 1 discloses a technique for field weakening control by correcting a current command set according to operating conditions such as torque command using a current command based on voltage feedback control. In this voltage feedback control, a limiter is provided because the current command is corrected only in the direction of increasing absolute value of the field weakening current. Therefore, voltage feedback control can operate only when the voltage between the motor terminals exceeds the inverter's maximum output voltage.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2006-141095 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] In existing field weakening control, when the current command set according to operating conditions such as torque command is insufficient, voltage feedback control works to supplement the deficiency. However, when the current command is too large or the voltage between the motor terminals is lower than the inverter's maximum output voltage, there is a technical problem where voltage feedback control fails to operate due to the aforementioned limiter, resulting in residual current flowing through.

[0009] The purpose of this invention is to solve the above-mentioned technical problems by avoiding the flow of residual current under weak magnetic field control, thereby preventing a decrease in motor drive efficiency.

[0010] Technical means for solving technical problems

[0011] The motor drive device of the present invention is a device for driving a motor by controlling the torque generated by the motor based on the d-axis current and the q-axis current. It includes: a d-axis current command generation unit that calculates a first d-axis current command; a current command correction unit that generates a positive correction amount added to the first d-axis current command when the inter-terminal voltage of the motor is above a predetermined value; and a voltage feedback control unit that generates a negative correction amount added to the first d-axis current command such that the inter-terminal voltage of the motor does not exceed a predetermined maximum output voltage. The torque is controlled based on a second d-axis current command and a q-axis current command obtained by adding the positive correction amount and the negative correction amount to the first d-axis current command.

[0012] The electric vehicle system of the present invention includes a motor drive unit, a motor driven by the motor drive unit, an axle connected to the motor, and wheels fixed to the axle.

[0013] The effects of the invention

[0014] According to the present invention, residual current can be avoided under weak magnetic field control, thereby preventing a decrease in motor drive efficiency. Attached Figure Description

[0015] Figure 1 This is a structural diagram of the motor drive device according to the first embodiment.

[0016] Figure 2 This is a functional block diagram of the control unit in the first embodiment.

[0017] Figure 3 This is a diagram illustrating an example of the operation (work) of the motor drive device according to the first embodiment.

[0018] Figure 4 This is a diagram illustrating an example of the operation of the motor drive device according to the first embodiment.

[0019] Figure 5 This is a diagram illustrating an example of the operation of the motor drive device according to the first embodiment.

[0020] Figure 6 This is a functional block diagram of the control unit in the second embodiment.

[0021] Figure 7 This is a functional block diagram of the control unit in the third embodiment.

[0022] Figure 8 This is a structural diagram of the electric vehicle system according to the fourth embodiment. Detailed Implementation

[0023] Hereinafter, the motor drive device of the present invention will be described with reference to the accompanying drawings. Furthermore, the same reference numerals will be used for the same elements in each drawing, and repeated descriptions will be omitted.

[0024] [First Implementation Method]

[0025] use Figures 1-5 A first embodiment of the motor drive device of the present invention will be described.

[0026] Figure 1 This is a structural diagram of the motor drive device 100 according to the first embodiment. The motor drive device 100 of this embodiment drives the motor 101 by controlling the torque generated by the three-phase synchronous motor 101 (hereinafter referred to as "motor 101") through vector control based on the d-axis current and the q-axis current. It includes: a power conversion circuit 102 that generates an AC voltage for driving the motor 101 from a DC power supply; a DC power supply 103 that supplies a DC voltage VDC to the power conversion circuit 102; a smoothing capacitor 104 that smooths the DC voltage VDC; and a control unit 105 that controls the power conversion circuit 102.

[0027] A rotor position sensor 106, which detects the rotor position, is connected to the motor 101. A current sensor 107, which detects the current flowing through each phase of the motor 101, is provided between the motor 101 and the power conversion circuit 102. Furthermore, a voltage sensor 108, which detects the DC voltage VDC of the DC power supply 103, is connected in parallel with the DC power supply 103. The motor 101 is a three-phase permanent magnet synchronous motor or the like, and the rotor position sensor 106 is a resolver or the like. Additionally, the DC power supply 103 is a lithium-ion secondary battery or the like.

[0028] In the motor drive unit 100, the torque command Tm*, the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current sensor 107, the DC voltage VDC detected by the voltage sensor 108, and the rotor position θdc detected by the rotor position sensor 106 are input to the control unit 105. Based on these sensor signals, the control unit 105 outputs switching signals S1 to S6 to activate the switching elements SW1 to SW6 of the power conversion circuit 102, respectively.

[0029] Figure 2 This is a functional block diagram of the control unit 105 according to the first embodiment. The control unit 105 is based on vector control and includes functional blocks (modules) of a current command generation unit 200, a current control unit 203, a dq / three-phase conversion unit 204, a three-phase / dq conversion unit 201, a speed calculation unit 202, and a PWM pulse generation unit 205. The control unit 105 can be configured, for example, by a microcomputer, and these functional blocks can be implemented by executing a predetermined program in the microcomputer. Alternatively, some or all of these functional blocks can be implemented using hardware circuits such as logic ICs or FPGAs.

[0030] The current command generation unit 200 generates a d-axis current command Id* (hereinafter sometimes referred to as "corrected d-axis current command") and a q-axis current command Iq* based on the torque command Tm* input from an upper-level control device (not shown) in order to achieve maximum torque / current control and field weakening control of the motor 101. Here, maximum torque / current control refers to control that maximizes the motor torque corresponding to the same current by adjusting the current command.

[0031] The three-phase / dq conversion unit 201 converts the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current sensor 107 into d-axis detection current Id and q-axis detection current Iq based on the rotor position θdc detected by the rotor position sensor 106.

[0032] The rotational speed calculation unit 202 derives the rotational angular velocity ω based on the rotor position θdc detected by the rotor position sensor 106.

[0033] The current control unit 203 controls the current in the following manner: based on the d-axis current command Id* and q-axis current command Iq* from the current command generation unit 200, the d-axis detected current Id and q-axis detected current Iq from the three-phase / dq conversion unit 201, and the rotational angular velocity ω from the speed calculation unit 202, it generates the d-axis voltage command Vd* and the q-axis voltage command Vq*, so that the d-axis current and q-axis current follow each command value.

[0034] The dq / three-phase conversion unit 204 converts the d-axis voltage command Vd* and q-axis voltage command Vq* from the current control unit 203 into U-phase voltage command Vu*, V-phase voltage command Vv*, and W-phase voltage command Vw*, based on the rotor position θdc detected by the rotor position sensor 106.

[0035] The PWM pulse generation unit 205 outputs switching signals S1 to S6 based on the DC voltage VDC detected by the voltage sensor 108 and the U-phase voltage command Vu*, V-phase voltage command Vv*, and W-phase voltage command Vw* from the dq / three-phase conversion unit 204.

[0036] The above is an overview of the structure of the control unit 105. Next, details of the current command generation unit 200 will be described.

[0037] The current command generation unit 200 includes: a d-axis current command generation unit 206, a q-axis current command calculation unit 210, a maximum output voltage calculation unit 211, a voltage amplitude calculation unit 212, a voltage feedback control unit 208, a current command correction unit 209, and an adder 207.

[0038] The d-axis current command generation unit 206 calculates and generates a pre-correction d-axis current command Idp* based on the torque command Tm*. The d-axis current command generation unit 206 can, for example, be configured using a lookup table that corresponds the torque command Tm* to the pre-correction d-axis current command Idp*. Alternatively, it can be configured to generate the pre-correction d-axis current command Idp* based not only on the torque command Tm*, but also on the rotational angular velocity ω.

[0039] For the uncorrected d-axis current command Idp* from the d-axis current command generation unit 206, the negative correction amount Idfb* from the voltage feedback control unit 208 and the positive correction amount Idc* from the current command correction unit 209 are added to the adder 207 to generate the corrected d-axis current command Id*. The operation of the voltage feedback control unit 208 and the current command correction unit 209 will be described later.

[0040] The q-axis current command calculation unit 210 generates the q-axis current command Iq* based on the torque command Tm* and the d-axis current command Id* from the adder 207. The q-axis current command calculation unit 210 can be configured, for example, by a lookup table that maps the torque command Tm* to the d-axis current command Id* and the q-axis current command Iq*.

[0041] The maximum output voltage calculation unit 211 calculates the maximum output voltage Vam that the power conversion circuit 102 can generate based on the DC voltage VDC detected by the voltage sensor 108. Here, when a sinusoidal modulation method is applied (the ratio of the output voltage amplitude of the power conversion circuit 102 to the DC voltage VDC is at most 0.866 (≈√3 / 2) of the line voltage), the maximum output voltage Vam is derived in the maximum output voltage calculation unit 211 by the following formula.

[0042] Vam=VDC / 2……(1)

[0043] The voltage amplitude calculation unit 212 derives the voltage amplitude Va* based on the d-axis voltage command Vd* and the q-axis voltage command Vq* from the current control unit 203, according to the following formula.

[0044] Va*=√(Vd*^2+Vq*^2)……(2)

[0045] In addition, Figure 2In the example, in the voltage amplitude calculation unit 212, the voltage amplitude Va* based on the d-axis voltage command Vd* and the q-axis voltage command Vq* is calculated. However, it is also possible to measure the AC voltage output from the power conversion circuit 102 to the motor 101, obtain the d-axis voltage Vd and the q-axis voltage Vq based on the measurement result, and calculate the voltage amplitude Va based on the voltage detection value. That is, the voltage amplitude calculation unit 212 can calculate the voltage amplitude Va (Va*) output from the motor drive device 100 based on the d-axis voltage Vd (d-axis voltage command Vd*) adjusted so that the d-axis current Id follows the d-axis current command Id*, and the q-axis voltage Vq (q-axis voltage command Vq*) adjusted so that the q-axis current Iq follows the q-axis current command Iq*. The motor drive device 100 applies the voltage amplitude Va (Va*) to the motor 101 as the inter-terminal voltage of the motor 101.

[0046] The voltage feedback control unit 208 includes a subtractor 208a, an integral control gain 208b, and an integrator 208c with a limiter. The voltage feedback control unit 208 multiplies the difference (ΔVa=Vam-Va*) between the maximum output voltage Vam from the maximum output voltage calculation unit 211 and the voltage amplitude Va* from the voltage amplitude calculation unit 212 by the integral control gain KI, integrates the result by the integrator 208c with the limiter, and outputs a correction amount Idfb*, which is added to the original d-axis current command Idp*.

[0047] The integrator 208c with a limiter performs a limiting process to make the integral of the value obtained by multiplying the difference ΔVa by the integral control gain KI into a value greater than zero. Through this limiting process, the correction amount Idfb* output from the voltage feedback control unit 208 will inevitably become negative.

[0048] The limiting process of the integrator 208c with a limiter is necessary to stop the operation of the voltage feedback control unit 208 when field weakening control is not required. Without the limiting process, even when the voltage amplitude Va* is less than the maximum output voltage Vam and field weakening control-based voltage regulation is not required, the voltage feedback control unit 208 will output a correction amount Idfb* based on the difference ΔVa (in this case, the correction amount Idfb* becomes positive). As a result, if maximum torque / current control is used, the operating point (operation point) deviates from the optimal condition that maximizes the torque / current ratio due to the addition of the correction amount Idfb*, leading to reduced operating efficiency.

[0049] In the present embodiment, by performing a limiting process in the integrator 208c with a limiter, when the integration result of the value obtained by multiplying the difference ΔVa by the integral control gain KI becomes positive, the voltage feedback control unit 208 outputs 0 as the correction amount Idfb*. Thereby, when voltage regulation is not required by field weakening control, the operating point is prevented from deviating from the optimal conditions.

[0050] Figure 3 , Figure 4 Examples of the operation of the motor drive device 100 of the present embodiment when transferring to field weakening control as the rotational speed increases are shown respectively. Figure 3 and Figure 4 In, (a) shows the time change of the rotational angular velocity ω, (b) shows the time change of the d-axis current command Id*, and (c) shows the time change of the voltage amplitude Va*. Here, the positive correction amount Idc* from the current command correction unit 209 is always set to zero.

[0051] In Figure 3 and Figure 4 In the operation example, the rotational angular velocity ω accelerates to time t12 at a certain slope, and thereafter the rotational angular velocity ω is constant (fixed), maintaining the same motor speed.

[0052] Figure 3 In, an operation example is shown in a case where the value of the pre-correction d-axis current command Idp* is set in such a way that the pre-correction d-axis current command Idp* output from the d-axis current command generation unit 206 at t = 0 and the optimal current Idopt satisfy the relationship |Idp*| < |Idopt|. In this case, the field weakening current is insufficient when using the pre-correction d-axis current command Idp*. The optimal current Idopt is the current value at which the relationship Va* = Vam holds between the voltage amplitude Va* and the maximum output voltage Vam after time t11. However, for the sake of convenience, the value of Idopt is made constant during the period from 0 to t11. In addition, Idp* is made a constant value.

[0053] In Figure 3 In this case, as described above, since the field weakening current is insufficient when using the pre-correction d-axis current command Idp*, after time t11 when Vam < Va*, the voltage feedback control unit 208 generates a negative correction amount Idfb* based on the difference ΔVa between the maximum output voltage Vam and the voltage amplitude Va*.

[0054] The negative correction amount Idfb* generated by the voltage feedback control unit 208 is added to the d-axis current command Idp* before correction in the adder 207. As a result, the value of the corrected d-axis current command Id* (Id* = Idp* + Idfb*) gradually approaches the optimal current Idopt. At time t11', when the value of the d-axis current command Id* reaches the optimal current Idopt and Va* = Vam, the voltage feedback control unit 208 adjusts the negative correction amount Idfb* to maintain this relationship. As a result, the motor drive device 100 operates in such a way as to maintain the relationship of Id* = Idopt and Va* = Vam.

[0055] As described above, in the motor drive device 100 of the present embodiment, in the case of insufficient field-weakening current, by operating in a manner that the voltage feedback control unit 208 supplements the insufficient part, the d-axis current command Id* can be maintained at the optimal current Idopt, and the voltage amplitude Va* can be made not to exceed the maximum output voltage Vam.

[0056] On the other hand, in Figure 4 shows an operation example in the case where the value of the d-axis current command Idp* before correction output from the d-axis current command generation unit 206 at t = 0 and the optimal current Idopt satisfy the relationship of |Idopt| < |Idp*|. In this case, the field-weakening current is excessive when using the d-axis current command Idp* before correction. In addition, other conditions are the same as Figure 3 the same.

[0057] In Figure 4 the case, since the field-weakening current is excessive as described above when using the d-axis current command Idp* before correction, Va* < Vam at time t11. At this time, in the voltage feedback control unit 208, the integrator 208c with a limiter can obtain a positive integral value based on the difference ΔVa, but through the limiting process of the integrator 208c with a limiter, the correction amount Idfb* finally output by the voltage feedback control unit 208 becomes zero. As a result, the d-axis current command Idp* before correction is not corrected and remains in the state of flowing excessive current.

[0058] In this way, the voltage feedback control unit 208 has a structure that operates only during field-weakening control through the limiting process of the integrator 208c with a limiter, but does not operate even in the case of excessive field-weakening current, so there is a technical problem of reduced operating efficiency.

[0059] Therefore, in the motor drive device 100 of the present embodiment, in order to solve the above technical problem of the voltage feedback control unit 208, a Figure 2 current command correction unit 209 shown is provided.

[0060] The current command correction unit 209 includes a reference voltage calculation unit 209a and a correction command generation unit 209b. The voltage feedback control unit 208 outputs a negative correction amount Idfb*, and the current command correction unit 209 generates and outputs a positive correction amount Idc*. 49>

[0061] The reference voltage calculation unit 209a calculates and sets a first reference voltage Va1 and a second reference voltage Va2 based on the DC voltage VDC of the DC power supply 103 detected by the voltage sensor 108. Here, for the maximum output voltage Vam calculated by the above formula (1), for example, in such a way that the relationship Va1 < Va2 ≤ Vam is satisfied, the values of Va1 and Va2 are determined.

[0062] The correction command generation unit 209b generates a positive correction amount Idc* based on the voltage amplitude Va* from the voltage amplitude operation unit 212 and the magnitude relationship between the first reference voltage Va1 and the second reference voltage Va2 from the reference voltage calculation unit 209a. Here, according to the magnitude relationship between Va* and Va1, Va2, one of the following formulas (3) to (5) is used to generate and output the positive correction amount Idc*.

[0063] (a) When 0 ≤ Va* < Va1

[0064] Idc* = 0......(3)

[0065] (b) When Va1 ≤ Va* < Va2

[0066] Idc* = (Idc2 / (Va2 - Va1)) · (Va* - Va1)......(4)

[0067] (c) When Va2 ≤ Va*

[0068] Idc* = Idc2......(5)

[0069] Among them, the value of Idc2 in formulas (4) and (5) is preset in the correction command generation unit 209b based on the d-axis current command Idp* before correction and the above optimal current Idopt. Specifically, when the absolute value of the current value obtained by adding the positive correction amount Idc* calculated by formula (5) to the d-axis current command Idp* before correction is less than the absolute value of the optimal current Idopt, thus as Figure 3 explained, in such a way that the field-weakening current is deliberately insufficient, the value of Idc2 is set in the correction command generation unit 209b. In addition, the value of Idc2 can also be changed according to the d-axis current command Idc* before correction and the value of the DC voltage VDC.

[0070] The positive correction amount Idc* generated by the correction command generation unit 209b is added in adder 207 together with the negative correction amount Idfb* output from voltage feedback control unit 208 and the d-axis current command Idp* before correction. Here, in the correction command generation unit 209b, the positive correction amount Idc* is generated by using Idc2 set as described above, such that the value of Idp* + Idc* is intentionally insufficient as the field weakening current. The voltage feedback control unit 208 operates in a way that compensates for the insufficient field weakening current, generating the negative correction amount Idfb*. Therefore, it is possible to avoid Figure 4 The diagram shows the condition of residual current flowing through the flow.

[0071] However, when the positive correction amount Idc* is added to the original d-axis current command Idp* before field weakening control, the motor operating point deviates from the optimal condition, resulting in reduced operating efficiency. Therefore, in the correction command generation unit 209b, as shown in equation (3) above, the positive correction amount Idc* is set to zero when the voltage amplitude Va* is less than the first reference voltage Va1. Thus, the current command correction unit 209 can generate the positive correction amount Idc* just before switching to field weakening control.

[0072] Regarding the operating timing of the current command correction unit 209, for example, a method could be considered to generate a positive correction amount Idc* at the moment when the voltage amplitude Va* reaches the maximum output voltage Vam. However, when using this method, there is a possibility of torque shock occurring due to the abrupt change in the d-axis current command Id*.

[0073] Therefore, in the motor drive device 100 of this embodiment, control is performed by gradually generating a positive correction amount Idc* from shortly before the voltage amplitude Va* reaches the maximum output voltage Vam. Specifically, the first reference voltage Va1 is set to a value less than the maximum output voltage Vam, and the second reference voltage Va2 is set to be equal to the maximum output voltage Vam.

[0074] Figure 5 and Figure 3 , Figure 4 Similarly, the operation of the motor drive device 100 in this embodiment when it switches to field weakening control as the rotational speed increases is illustrated by an example. Figure 5 The example shown is an operation example in which the positive correction amount Idc* is set in the current command correction unit 209 according to formulas (3) to (5).

[0075] exist Figure 5 In the example, the rotational angular velocity ω accelerates at a certain angle until time t23, after which the rotational angular velocity ω remains constant, maintaining the same motor speed.

[0076] exist Figure 5 In, with Figure 4 Similarly, an example of operation is shown where the value of the pre-correction d-axis current command Idp* is set such that the pre-correction d-axis current command Idp* output from the d-axis current command generation unit 206 at t=0 and the optimal current Idopt satisfy the relationship |Idopt|<|Idp*|. However, for convenience, the value of Idopt is kept constant during the period from 0 to t22. Additionally, Idp* is kept constant. In this case, as described above, when using the pre-correction d-axis current command Idp*, the field weakening current is excessive.

[0077] exist Figure 5 In the example operation, when the voltage amplitude Va* reaches the first reference voltage Va1 at time t21, the current command correction unit 209 starts to generate a positive correction amount Idc* according to equation (4). By adding this positive correction amount Idc* to the d-axis current command Idp* before correction, the d-axis current command Id* is corrected towards the optimal current Idopt. When the voltage amplitude Va* becomes greater than the maximum output voltage Vam (the second reference voltage Va2) at time t22, satisfying the relationship |Idp*+Idc*|<|Idopt|, and... Figure 3 Similarly, the voltage feedback control unit 208 generates a negative correction amount Idfb* based on the difference ΔVa between the maximum output voltage Vam and the voltage amplitude Va*. At this time, the current command correction unit 209 sets the positive correction amount Idc* to a constant according to equation (5). In addition, the absolute value of the positive correction amount Idc* at this time is greater than the absolute value of the negative correction amount Idfb* generated by the voltage feedback control unit 208.

[0078] The negative correction Idfb* generated by the voltage feedback control unit 208 is added together with the positive correction Idc* in the adder 207 to the original d-axis current command Idp*. As a result, the value of the corrected d-axis current command Id* (Id* = Idp* + Idc* + Idfb*) gradually approaches the optimal current Idopt. When the value of the d-axis current command Id* reaches the optimal current Idopt at time t22', and Va* = Vam, the voltage feedback control unit 208 adjusts the negative correction Idfb* to maintain this relationship. As a result, with... Figure 3 Similarly, the motor drive unit 100 operates in a manner that maintains the relationship Id* = Idopt and Va* = Vam.

[0079] Thus, even in the case of excessive magnetic field current, the motor drive device 100 of this embodiment can prevent the voltage feedback control unit 208 from flowing through the current command correction unit 209 to make the voltage feedback control unit 208 work.

[0080] According to the first embodiment of the present invention described above, the following effects are achieved.

[0081] (1) The motor drive device 100 is a device that controls the torque generated by the motor 101 based on the d-axis current and the q-axis current to drive the motor 101. The motor drive device 100 includes: a d-axis current command generation unit 206 that calculates the d-axis current command Idp* before correction; a current command correction unit 209 that generates a positive correction amount Idc*, which is added to the d-axis current command Idp* before correction when the voltage amplitude Va, Va*, which is the voltage between the terminals of the motor 101, is above a predetermined reference voltage Va1; and a voltage feedback control unit 208 that generates a negative correction amount Idfb*, which is added to the d-axis current command Idp* before correction so that the voltage amplitude Va, Va* does not exceed a predetermined maximum output voltage Vam. The torque of motor 101 is controlled based on the corrected d-axis current command Id* and q-axis current command Iq*, obtained by adding positive correction amount Idc* and negative correction amount Idfb* to the original d-axis current command Idp*. By employing such a structure, such as using... Figure 5 As explained, this can prevent residual current from flowing under weak magnetic field control, thus preventing a decrease in motor drive efficiency.

[0082] (2) The voltage feedback control unit 208 continues to generate a negative correction amount Idfb* after the voltage amplitude Va and Va* reach the maximum output voltage Vam. By adopting such a structure, the d-axis current command Id* can be maintained at the optimal current Idopt, so that the voltage amplitude Va* does not exceed the maximum output voltage Vam.

[0083] (3) The motor drive device 100 also includes a voltage amplitude calculation unit 212. The voltage amplitude calculation unit 212 calculates the voltage amplitude Va (Va*) output by the motor drive device 100 based on the d-axis voltage Vd (d-axis voltage command Vd*) adjusted such that the d-axis current follows the corrected d-axis current command Id*, and the q-axis voltage Vq (q-axis voltage command Vq*) adjusted such that the q-axis current follows the q-axis current command Iq*. The current command correction unit 209 sets reference voltages Va1 and Va2 based on the voltage VDC of the DC power supply supplied to the motor drive device 100, and generates a positive correction amount Idc* based on the relationship between the voltage amplitude Va (Va*) and the reference voltages Va1 and Va2. By employing this structure, a positive correction amount Idc*, which is added to the original d-axis current command Idp*, can be generated at an appropriate value.

[0084] (4) When the voltage amplitude Va (Va*) is above the reference voltage Va2, the current command correction unit 209 keeps the positive correction amount Idc* constant. At this time, the positive correction amount Idc* is greater than the negative correction amount Idfb*. By adopting such a structure, the d-axis current command Id* can be stably maintained at the optimal current Idopt.

[0085] (5) The reference voltages Va1 and Va2 are below the maximum output voltage Vam. By adopting such a structure, a positive correction Idc* can be generated with an appropriate value so that the corrected d-axis current command Id* is intentionally insufficient as a field weakening current.

[0086] [Second Implementation]

[0087] use Figure 6 The second embodiment of the motor drive device of the present invention will be described.

[0088] Figure 6 This is a functional block diagram of the control unit 105 included in the motor drive device 100 of the second embodiment. In this embodiment, the control unit 105 is located in the current command generation unit 200, replacing the one described in the first embodiment. Figure 2 The current command correction unit 209 is replaced by a current command correction unit 600. This current command correction unit 600 generates a positive correction amount Idc* based on the modulation rate Ma*, which differs from the current command correction unit 209 of the first embodiment. The structure of the motor drive device 100, except for the control unit 105, and the structure of the control unit 105, except for the current command correction unit 600, are the same as in the first embodiment. Therefore, descriptions of structures identical to those in the first embodiment are omitted.

[0089] The current command correction unit 600 includes a modulation rate calculation unit 600a, a reference modulation rate calculation unit 600b, and a correction command generation unit 600c.

[0090] The modulation rate calculation unit 600a derives the modulation rate Ma* based on the DC voltage VDC of the DC power supply 103 detected by the voltage sensor 108 and the voltage amplitude Va* from the voltage amplitude calculation unit 212.

[0091] Ma*=Va* / (VDC / 2)……(6)

[0092] Further, when calculating the voltage amplitude Va based on the voltage detection value in the voltage amplitude calculation unit 212 as described above, in the modulation rate calculation unit 600a, the modulation rate Ma based on the voltage detection value can be derived by replacing Va* in the above formula (6) with Va. That is, the modulation rate calculation unit 600a can calculate the modulation rate Ma (Ma*) of the motor drive device 100 based on the DC voltage VDC of the DC power supply 103 supplied to the motor drive device 100 and the voltage amplitude Va (Va*) calculated by the voltage amplitude calculation unit 212.

[0093] The reference modulation rate calculation unit 600b calculates and sets the first reference modulation rate Ma1 and the second reference modulation rate Ma2. Here, for example, the values of Ma1 and Ma2 are determined in such a way that the relationship Ma1 < Ma2 ≤ 1 is satisfied.

[0094] The correction instruction generation unit 600c generates a positive correction amount Idc* based on the magnitude relationship between the modulation rate Ma* from the modulation rate calculation unit 600a and the first reference modulation rate Ma1 and the second reference modulation rate Ma2 from the reference modulation rate calculation unit 600b. Here, according to the magnitude relationship between Ma* and Ma1, Ma2, one of the following formulas (7) to (9) is used to generate and output the positive correction amount Idc*.

[0095] (a) When 0 ≤ Ma* < Ma1

[0096] Idc* = 0......(7)

[0097] (b) When Ma1 ≤ Ma* < Ma2

[0098] Idc* = (Idc2 / (Ma2 - Ma1)) · (Ma* - Ma1)......(8)

[0099] (c) When Ma2 ≤ Ma*

[0100] Idc* = Idc2......(9)

[0101] Among them, the value of Idc2 in formulas (8) and (9) is preset in the correction instruction generation unit 600c based on the d-axis current command Idp* before correction and the above optimal current Idopt. Specifically, similar to the first embodiment, the value of Idc2 is set in the correction instruction generation unit 600c so that the absolute value of the current value when adding the positive correction amount Idc* calculated by formula (9) to the d-axis current command Idp* before correction is less than the absolute value of the optimal current Idopt, resulting in an intentional shortage of field-weakening current. Additionally, the value of Idc2 can also be varied corresponding to the value of the d-axis current command Idc* before correction and the DC voltage VDC.

[0102] The positive correction amount Idc* generated by the correction command generation unit 600c is added together with the negative correction amount Idfb* output from the voltage feedback control unit 208 and the original d-axis current command Idp* in the adder 207. Thus, similar to the first embodiment, the voltage feedback control unit 208 generates the negative correction amount Idfb* by compensating for the insufficient amount (the deficient portion) of the magnetic weakening current. Therefore, the situation of residual current flowing through it can be avoided.

[0103] Furthermore, in the motor drive device 100 of this embodiment, similar to the first embodiment, control is performed by gradually generating a positive correction amount Idc* slightly before the voltage amplitude Va* reaches the maximum output voltage Vam. Specifically, when sinusoidal modulation is applied, the first reference modulation rate Ma1 is set to a value less than 1, and the second reference modulation rate Ma2 is set to 1.

[0104] Even in the event of excessive field weakening current, the motor drive device 100 of this embodiment can prevent excessive current from flowing by activating the voltage feedback control unit 208 through the action of the current command correction unit 600. The operating principle is the same as that of the first embodiment, except that the current command correction unit 600 operates based on the modulation rate Ma*.

[0105] According to the second embodiment of the present invention described above, in addition to the effects of (1) and (2) described in the first embodiment, the following effects (6) to (8) are also achieved.

[0106] (6) The motor drive device 100 also includes a voltage amplitude calculation unit 212. The voltage amplitude calculation unit 212 calculates the voltage amplitude Va (Va*) output by the motor drive device 100 based on the d-axis voltage Vd (d-axis voltage command Vd*) adjusted so that the d-axis current follows the corrected d-axis current command Id*, and the q-axis voltage Vq (q-axis voltage command Vq*) adjusted so that the q-axis current follows the q-axis current command Iq*. The current command correction unit 600 calculates the modulation rate Ma (Ma*) and the reference modulation rates Ma1 and Ma2 based on the voltage VDC of the DC power supply supplied to the motor drive device 100 and the voltage amplitude Va (Va*), and generates a positive correction amount Idc* based on the relationship between the modulation rate Ma (Ma*) and the reference modulation rates Ma1 and Ma2. By adopting such a structure, a positive correction amount Idc*, which is added to the original d-axis current command Idp*, can be generated at an appropriate value.

[0107] (7) When the modulation rate Ma (Ma*) is greater than or equal to the reference modulation rate Ma2, the positive correction amount Idc* is made constant by the current command correction unit 209. At this time, the absolute value of the positive correction amount Idc* is greater than the absolute value of the negative correction amount Idfb*. By adopting such a structure, the d-axis current command Id* can be stably maintained at the optimal current Idopt.

[0108] (8) The reference modulation rates Ma1 and Ma2 are less than or equal to 1. By adopting such a structure, the positive correction amount Idc* can be generated with an appropriate value so that the corrected d-axis current command Id* is intentionally insufficient as the field-weakening current.

[0109] [Third Embodiment]

[0110] Use Figure 7 to describe the third embodiment of the motor drive device of the present invention.

[0111] Figure 7 is a functional block diagram of the control unit 105 included in the motor drive device 100 of the third embodiment. In the current command generation unit 200 of the control unit 105 in this embodiment, instead of the Figure 2 current command correction unit 209 described in the first embodiment, there is a current command correction unit 700. This current command correction unit 700 generates the positive correction amount Idc* based on a single reference value, and further includes a low-pass filter (hereinafter referred to as LPF) process before the adder 207, which is different from the current command correction unit 209 of the first embodiment. In addition, the structure other than the control unit 105 in the motor drive device 100 and the structure other than the current command correction unit 700 in the control unit 105 are the same as those in the first and second embodiments. Therefore, the description of the same structure as in the first and second embodiments is omitted.

[0112] The current command correction unit 700 includes a reference voltage calculation unit 700a, a correction command generation unit 700b, and an LPF 700c.

[0113] The reference voltage calculation unit 700a calculates and sets the first reference voltage Va1 based on the DC voltage VDC of the DC power supply 103 detected by the voltage sensor 108.

[0114] The correction command generation unit 700b generates the positive correction amount Idc* based on the magnitude relationship between the voltage amplitude Va* from the voltage amplitude calculation unit 212 and the first reference voltage Va1 from the reference voltage calculation unit 700a. Here, according to the magnitude relationship between Va* and Va1, the positive correction amount Idc* is generated and output using any one of the following equations (10) and (11).

[0115] (a) When 0 ≤ Va* < Va1

[0116] Idc*=0……(10)

[0117] (b) When Va1 ≤ Va*

[0118] Idc*=Idc2……(11)

[0119] The positive correction amount Idc* generated by the correction command generation unit 700b is input to the adder 207 via the LPF 700c after a predetermined delay time. In the adder 207, it is added together with the negative correction amount Idfb* output from the voltage feedback control unit 208 and the original d-axis current command Idp*. Therefore, since the positive correction amount Idc* is gradually added to the original d-axis current command Idp* with a delay time based on the LPF 700c, the generation of torque shocks accompanying abrupt changes in the d-axis current command Id* can be avoided. Furthermore, the voltage feedback control unit 208 is activated to generate the negative correction amount Idfb* in a manner that compensates for the insufficient magnetic weakening current, thus preventing the flow of residual current.

[0120] Furthermore, the motor drive device 100 using this embodiment, like the first and second embodiments, is controlled in a manner that gradually generates a positive correction amount Idc* from slightly before the voltage amplitude Va* reaches the maximum output voltage Vam. Specifically, the first reference voltage Va1 is set to a value less than the maximum output voltage Vam, and the time constant (delay time) of LPF700c is set to the same level as the response time constant of the current control unit 203.

[0121] The motor drive device 100 of this embodiment can prevent excess current from flowing even in the case of excessive field weakening current, by means of the current command correction unit 700, which enables the voltage feedback control unit 208 to operate. The working principle is the same as that of the first embodiment, except that the positive correction amount Idc* is gradually added to the d-axis current command Idp* before correction by means of LPF700c with a predetermined delay time.

[0122] According to the third embodiment of the present invention described above, in addition to the effects of (1) and (2) described in the first embodiment, the following effect (9) is also achieved.

[0123] (9) The motor drive device 100 also includes a low-pass filter 700c, which adds the original d-axis current command Idp* to the positive correction amount Idc* with a predetermined delay time via the low-pass filter 700c to generate the corrected d-axis current command Id*. By adopting such a structure, the generation of torque shocks accompanying abrupt changes in the d-axis current command Id* can be avoided, and the flow of residual current can be avoided.

[0124] In the third embodiment described above, an example was given in which the positive correction amount Idc* generated by the correction command generation unit 700b based on its relationship with the first reference voltage Va1 was input to the adder 207 via the LPF 700c in the current command correction unit 700. However, it can also be applied to the case where the positive correction amount Idc* is generated based on the modulation rate, as described in the second embodiment. That is, in the current command correction unit 600 described in the second embodiment, the first reference modulation rate Ma1 is set by the reference modulation rate calculation unit 600b, and the correction command generation unit 700b generates the positive correction amount Idc* based on the relationship between the first reference modulation rate Ma1 and the modulation rate Ma* calculated by the modulation rate calculation unit 600a. Inputting the positive correction amount Idc* generated in this way to the adder 207 via the LPF 700c with a predetermined delay time can also achieve the same effect.

[0125] [Fourth Implementation Method]

[0126] Reference Figure 8 The electric vehicle system of the fourth embodiment will be described. Figure 8 This is a structural diagram of the electric vehicle system according to the fourth embodiment. Furthermore, an example of an electric vehicle system equipped with a motor drive device according to any of the first, second, or third embodiments will be described here.

[0127] like Figure 8 As shown, the electric vehicle system 800 supports a pair of axles 801a and 801b on the central axle of the vehicle body. Wheels 802a and 802b are fixed to both ends of one axle 801a, and wheels 802c and 802d are fixed to both ends of the other axle 801b. A three-phase synchronous motor 101 is connected to one axle 801a, and the rotational power of the three-phase synchronous motor 101 is transmitted to the wheels 802a and 802b via the axle 801a. The motor drive unit 100 receives a torque command Tm* generated by the upper-level system and drives the three-phase synchronous motor 101.

[0128] In the motor drive unit 100 of the electric vehicle system 800, during field weakening control at high speed, the current command correction unit 209 (or current command correction unit 600, current command correction unit 700) generates a positive correction amount Idc* to correct the previous d-axis current command Idp*. This results in the current value when the positive correction amount Idc* is added to the previous d-axis current command Idp* being intentionally insufficient as the field weakening current, and the negative correction amount Idfb* generated by the voltage feedback control unit 208 compensates for this deficiency. As a result, the voltage feedback control unit 208 can operate independently of the set value of the previous d-axis current command Idp*, driving the three-phase synchronous motor 101 with an appropriate (neither excessive nor insufficient) optimal field weakening current. That is, it is possible to avoid... Figure 4 The situation is shown. This avoids the flow of residual current during field weakening control, preventing a decrease in the operating efficiency of the three-phase synchronous motor and increasing the driving range of the electric vehicle system by 800.

[0129] The above embodiment describes an example of driving a three-phase synchronous motor 101 by a motor drive device 100 for electric vehicles such as electric cars and hybrid vehicles. However, the same effect can be obtained by applying the motor drive device 100 to other vehicles that are driven by a three-phase synchronous motor, such as railways.

[0130] Furthermore, the present invention is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above are detailed for ease of understanding and explanation of the technology of the present invention, and are not limited to having all the structures described. Additionally, a portion of the structure of one embodiment can be replaced with the structure of another embodiment, and structures of other embodiments can be added to the structure of one embodiment. For example, the structure of the LPF700c, which adds a third embodiment to the first and second embodiments, can be used. Furthermore, for a portion of the structure of each embodiment, other structures can be added, deleted, or replaced.

[0131] Additionally, the control lines and information lines shown in the diagram are those deemed necessary for explanation, and not all control lines and information lines are necessarily shown. In fact, it can be assumed that almost all structures are interconnected.

[0132] Explanation of reference numerals in the attached figures

[0133] 100: Motor drive unit

[0134] 101: Three-phase synchronous motor (electric motor)

[0135] 102: Power conversion circuit

[0136] 103: DC power supply

[0137] 104: Smoothing Capacitor

[0138] 105: Control Department

[0139] 106: Rotor position sensor

[0140] 107: Current sensor

[0141] 108: Voltage sensor

[0142] 200: Current command generation unit

[0143] 201: Three-phase / dq converter

[0144] 202: Speed ​​Calculation Unit

[0145] 203: Current Control Unit

[0146] 204: dq / Three-phase conversion unit

[0147] 205: PWM pulse generation unit

[0148] 206: d-axis current command generation unit

[0149] 207: Adder

[0150] 208: Voltage Feedback Control Unit

[0151] 208a: Subtractor

[0152] 208b: Integral Control Gain

[0153] 208c: Integrator with limiter

[0154] 209, 600, 700: Current command correction unit

[0155] 209a, 700a: Reference Voltage Calculation Unit

[0156] 209b, 600c, 700b: Modification Instruction Generation Unit

[0157] 600a: Modulation Rate Calculation Unit

[0158] 600b: Reference Modulation Rate Calculation Unit

[0159] 700c: LPF

[0160] 210: q-axis current command processing unit

[0161] 211: Maximum Output Voltage Calculation Unit

[0162] 212: Voltage Amplitude Calculation Unit

[0163] 800: Electric Vehicle System

[0164] 801a, 801b: Axles

[0165] 802a, 802b, 802c, 802d: wheels.

Claims

1. A motor drive device that drives a motor by controlling the torque generated by the motor based on d-axis current and q-axis current, the motor drive device being characterized by comprising: The d-axis current command generation unit that calculates the first d-axis current command; The current command correction unit generates a positive correction amount that is added to the first d-axis current command when the voltage between the terminals of the motor is above a predetermined value; and The voltage feedback control unit generates a negative correction amount that is added to the first d-axis current command to ensure that the voltage between the motor terminals does not exceed a predetermined maximum output voltage. The torque is controlled based on the second d-axis current command and the q-axis current command obtained by adding the positive correction amount and the negative correction amount to the first d-axis current command.

2. The motor drive device as described in claim 1, characterized in that: The voltage feedback control unit continues to generate the negative correction amount after the voltage between the motor terminals reaches the maximum output voltage.

3. The motor drive device as described in claim 1 or 2, characterized in that: The motor drive device also includes a voltage amplitude calculation unit. The voltage amplitude calculation unit calculates the voltage amplitude output by the motor drive device based on the d-axis voltage adjusted to make the d-axis current follow the second d-axis current command and the q-axis voltage adjusted to make the q-axis current follow the q-axis current command. The current command correction unit sets one or more reference voltages based on the voltage of the DC power supply supplied to the motor drive device, and generates the positive correction amount based on the relationship between the voltage amplitude and the reference voltage.

4. The motor drive device as described in claim 3, characterized in that: The current command correction unit sets the positive correction amount to a constant when the voltage amplitude is above the reference voltage.

5. The motor drive device as described in claim 4, characterized in that: When the positive correction amount is already fixed, the positive correction amount is greater than the negative correction amount.

6. The motor drive device as described in claim 3, characterized in that: The reference voltage is below the maximum output voltage.

7. The motor drive device as described in claim 1 or 2, characterized in that: The motor drive device also includes a voltage amplitude calculation unit. The voltage amplitude calculation unit calculates the voltage amplitude output by the motor drive device based on the d-axis voltage adjusted to make the d-axis current follow the second d-axis current command and the q-axis voltage adjusted to make the q-axis current follow the q-axis current command. The current command correction unit calculates the modulation rate based on the voltage of the DC power supply supplied to the motor drive device and the voltage amplitude, and sets one or more reference modulation rates, and generates the positive correction amount based on the relationship between the modulation rate and the reference modulation rate.

8. The motor drive device as described in claim 7, characterized in that: The current command correction unit sets the positive correction amount to a constant when the modulation rate is above the reference modulation rate.

9. The motor drive device as described in claim 8, characterized in that: When the positive correction amount is already fixed, the positive correction amount is greater than the negative correction amount.

10. The motor drive device as described in claim 7, characterized in that: The reference modulation rate is less than 1.

11. The motor drive device as described in claim 1 or 2, characterized in that: The motor drive device also includes a low-pass filter. The positive correction is added to the first d-axis current command via the low-pass filter with a specified delay time to generate the second d-axis current command.

12. An electric vehicle system, characterized in that, include: The motor drive device according to claim 1 or 2; The motor driven by the motor drive device; The axle connected to the motor; and The wheel fixed to the axle.

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