Rotating machine control device and electric power steering device

Abstract

This control device of a rotating machine is provided with an inverter which applies a voltage to the rotating machine, a current detector which is provided in the inverter and which detects the rotating machine current, i.e., the current in the rotating machine, and a controller which, on the basis of a rotating machine control command, outputs to the inverter a voltage command value, i.e., the command value of the voltage; the controller has a torque current command value generator (31) which calculates a torque current command value on the basis of the control command, field-weakening current command value generators (32-34) which calculate a field-weakening current command value, and a voltage command value calculator which calculates a voltage command value on the basis of the torque current command value and the field-weakening current command value; as the field-weakening current command value, the field-weakening current value generator outputs a first field-weakening current command value that limits the inverter modulation rate to a first threshold value at which the current detector is at least capable of detecting a two-phase rotating machine current.

Description

[Technical field]

[0001] The present disclosure relates to a control device for a rotating machine and an electric power steering device. [Background technology]

[0002] Field weakening control has been known as a technique for expanding the operating range (range of speed-torque characteristics) of a rotating machine. In simple terms, field weakening control reduces the amount of torque reduction that occurs with increasing speed by weakening the field force and ensuring the current flowing through the rotating machine.

[0003] The following Patent Document 1 discloses an example of a conventional field-weakening control. This field-weakening control is started when the modulation rate command value is smaller than the maximum modulation rate, and the timing at which the field-weakening control starts is made different from the timing of transition between asynchronous PWM control and five-pulse control using a sine wave PWM (Pulse Width Modulation) pattern. By performing such control, chattering between the asynchronous PWM control and the five-pulse control is prevented. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4715576 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the technology described in the above Patent Document 1 refers to the timing of starting field-weakening control for stably switching between asynchronous PWM control and synchronous PWM control such as 5-pulse control. However, the technology described in the above Patent Document 1 does not mention the timing of field-weakening control required for accurate current detection in the case of adopting a current detection method in an inverter equipped with a shunt resistor as a current detector.

[0006] For this reason, even if the technology described in the above Patent Document 1 is installed in a control device for a rotating machine using an inverter equipped with a shunt resistor, the current flowing through the rotating machine cannot be detected correctly. If the current flowing through the rotating machine cannot be detected correctly, the accuracy of the output torque of the rotating machine deteriorates due to a current detection error, resulting in a problem of increased vibration and noise.

[0007] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a rotating machine control device and an electric power steering device that can improve the accuracy of the output torque of the rotating machine and reduce vibration and noise by correctly detecting the current flowing through the rotating machine. [Means for solving the problem]

[0008] In order to solve the above problem, a control device for a rotating machine according to one aspect of the present disclosure includes an inverter that applies a voltage to a rotating machine, a current detector provided in the inverter and detecting a rotating machine current that is a current flowing through the rotating machine, and a controller that outputs a voltage command value that is a command value of the voltage to the inverter based on a control command of the rotating machine, the controller having a torque current command value generator that calculates a torque current command value based on the control command, a field weakening current command value generator that calculates a field weakening current command value, and a voltage command value calculator that calculates the voltage command value based on the torque current command value and the field weakening current command value, and the field weakening current command value generator outputs a first field weakening current command value that limits a modulation factor of the inverter to a first threshold value at which the current detector can detect at least two-phase of the rotating machine current, as the field weakening current command value.

[0009] In addition, an electric power steering device according to one embodiment of the present disclosure includes a torque detector that detects a steering torque of a steering wheel, a rotating machine that generates a steering assist torque for the steering wheel, and a control device for the rotating machine that controls driving of the rotating machine in response to the steering torque detected by the torque detector. Effect of the Invention

[0010] According to the present disclosure, it is possible to accurately detect two-phase rotating machine currents using a current detector provided in an inverter, thereby improving the accuracy of the output torque of the rotating machine and reducing vibration and noise. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a configuration of a main part of a control device for a rotating machine according to a first embodiment of the present disclosure. [Diagram 2] 3 is a block diagram showing an internal configuration of a current command value calculator in the first embodiment. FIG. [Diagram 3] 3 is a diagram for explaining a generation principle of a switching signal in the first embodiment. FIG. [Figure 4]FIG. 4 is a diagram showing an example of a change in voltage between both ends in the first embodiment. [Diagram 5] FIG. 4 is a diagram showing an example of a switching signal generated when a corrected voltage command changes in the first embodiment. [Figure 6] 5 is a flowchart showing a process performed by a corrected voltage generator in the first embodiment. [Figure 7] 3 is a diagram showing an example of waveforms of voltage command values ​​vu, vv, vw and corrected voltage command values ​​vu', vv', vw' in the first embodiment. FIG. [Figure 8] 4 is a diagram showing another example of the waveforms of the voltage command values ​​vu, vv, vw and the corrected voltage command values ​​vu', vv', vw' in the first embodiment. FIG. [Figure 9] FIG. 11 is a block diagram showing a configuration of a main part of a control device for a rotating machine according to a second embodiment of the present disclosure. [Figure 10] FIG. 11 is a block diagram showing a configuration of a main part of a control device for a rotating machine according to a third embodiment of the present disclosure. [Figure 11] FIG. 11 is a block diagram showing an internal configuration of a current command value calculator in the third embodiment. [Figure 12] FIG. 11 is a block diagram showing a configuration of a main part of a control device for a rotating machine according to a fourth embodiment of the present disclosure. [Figure 13] FIG. 13 is a block diagram showing an internal configuration of a current command value calculator in the fourth embodiment. [Figure 14] FIG. 13 is a diagram for explaining the physical meaning of the processing performed by the first field-weakening current command value upper and lower limit setter in the fourth embodiment. [Figure 15] FIG. 13 is a diagram for explaining the operation of a current command value calculator in the fourth embodiment. [Figure 16] FIG. 11 is a block diagram showing a configuration of a main part of a control device for a rotating machine according to a fifth embodiment of the present disclosure. [Figure 17] FIG. 13 is a diagram showing an example of a table used for determining a current in a current detector in the fifth embodiment. [Figure 18] 13 is a flowchart showing a process performed by a corrected voltage generator in the fifth embodiment. [Figure 19] FIG. 13 is a diagram showing an example of waveforms of voltage command values ​​vu, vv, vw and corrected voltage command values ​​vu', vv', vw' in the fifth embodiment. [Figure 20] FIG. 13 is a diagram showing an example of a switching signal output from a controller in the fifth embodiment. [Figure 21] FIG. 23 is a diagram showing another example of the waveforms of the voltage command values ​​vu, vv, vw and the corrected voltage command values ​​vu', vv', vw' in the fifth embodiment. [Figure 22] FIG. 13 is a block diagram showing a configuration of a main part of a rotary machine control device and an electric power steering device according to a sixth embodiment of the present disclosure. [Figure 23] FIG. 23 is a diagram showing an example of torque-rotation speed characteristics of a rotating machine in the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotating machine control device and an electric power steering device according to embodiments of the present disclosure will be described in detail below with reference to the drawings.

[0013] [First embodiment] Fig. 1 is a block diagram showing a configuration of a main part of a rotating machine control device according to a first embodiment of the present disclosure. As shown in Fig. 1, the rotating machine control device 1 according to the present embodiment includes a rotor position detector 11, an inverter 12, and a controller 13, and controls a rotating machine 10 based on a torque command T_ref as a control command input from the outside.

[0014] Here, a rotating machine 10 that is the control target of the rotating machine control device 1 is a three-phase AC rotating machine having three-phase windings U, V, and W. This rotating machine 10 may be, for example, any of a permanent magnet synchronous rotating machine, a wound field synchronous rotating machine, an induction rotating machine, and a synchronous reluctance motor.

[0015] The rotor position detector 11 includes a resolver, an encoder, an MR (magnetic resistance) sensor, etc., and detects the rotor position θ of the rotor of the rotating machine 10 using these. Note that, in this embodiment, an example in which the rotor position θ of the rotating machine 10 is detected using the rotor position detector 11 will be described, but the rotor position θ of the rotating machine 10 may be estimated without using the rotor position detector 11. In other words, in the present disclosure, information on the rotor position θ of the rotating machine 10 is necessary, but it is not essential to provide the rotor position detector 11.

[0016] Under the control of controller 13, inverter 12 converts DC power supplied from DC power supply BT into AC power and supplies the converted AC power to rotating machine 10. Note that DC power supply BT includes all devices necessary for supplying DC power, such as a battery, a DC-DC converter, a diode rectifier, a PWM rectifier, etc. The output voltage (DC bus voltage) of DC power supply BT is assumed to be Vdc.

[0017] The inverter 12 includes upper arm switching elements Sup, Svp, Swp, lower arm switching elements Sun, Svn, Swn, and shunt resistors Ru, Rv, Rw (current detectors). The upper arm switching elements Sup, Svp, Swp are connected to the positive electrode of a DC power supply BT. The lower arm switching elements Sun, Svn, Swn are connected to the upper arm switching elements Sup, Svp, Swp, respectively, and are connected to the negative electrode of the DC power supply BT via the shunt resistors Ru, Rv, Rw, respectively.

[0018] Here, a U-phase series circuit is formed by the upper arm switching element Sup, the lower arm switching element Sun, and the shunt resistor Ru. In this U-phase series circuit, the connection point between the upper arm switching element Sup and the lower arm switching element Sun is connected to the winding U of the rotating machine 10.

[0019] Furthermore, a V-phase series circuit is formed by the upper arm switching element Svp, the lower arm switching element Svn, and the shunt resistor Rv. In this V-phase series circuit, a connection point between the upper arm switching element Svp and the lower arm switching element Svn is connected to the winding V of the rotating machine 10.

[0020] Further, the upper arm switching element Swp, the lower arm switching element Swn, and the shunt resistor Rw form a W-phase series circuit. In this W-phase series circuit, a connection point between the upper arm switching element Swp and the lower arm switching element Swn is connected to the winding W of the rotating machine 10.

[0021] The upper arm switching elements Sup, Svp, Swp and the lower arm switching elements Sun, Svn, Swn may be semiconductor switches such as IGBTs (Insulated Gate Bipolar Transistors), bipolar transistors, and MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors).

[0022] The upper arm switching elements Sup, Svp, Swp are respectively input with switching signals Gup, Gvp, Gwp output from the controller 13. The lower arm switching elements Sun, Svn, Swn are respectively input with switching signals Gun, Gvn, Gwn output from the controller 13. The upper arm switching elements Sup, Svp, Swp and the lower arm switching elements Sun, Svn, Swn are turned on or off by the switching signals Gup, Gvp, Gwp, Gun, Gvn, Gwn output from the controller 13. Hereinafter, the switching signals Gup, Gvp, Gwp, Gun, Gvn, Gwn may be collectively referred to as "switching signals Gup-Gwn."

[0023] For example, when the switching signal Gup is an "on command (=1)", the upper arm switching element Sup is in the on state, and when the switching signal Gup is an "off command (=0)", the upper arm switching element Sup is in the off state. The same is true for the other switching elements (upper arm switching elements Svp, Swp and lower arm switching elements Sun, Svn, Swn). In this way, the inverter 12 generates AC power to be supplied to the rotating machine 10 from DC power supplied from the DC power source BT.

[0024] The shunt resistor Ru outputs a voltage VRu (=-Ru×iu) across the resistor Rv that is proportional to a current (rotating machine current) iu flowing through the winding U of the rotating machine 10 to the controller 13. The shunt resistor Rv outputs a voltage VRv (=-Rv×iv) across the resistor Rv that is proportional to a current (rotating machine current) iv flowing through the winding V of the rotating machine 10 to the controller 13. The shunt resistor Rw outputs a voltage VRw (=-Rw×iw) across the resistor Rw that is proportional to a current (rotating machine current) iw flowing through the winding W of the rotating machine 10 to the controller 13.

[0025] Here, the voltages VRu, VRu, VRw across the inverter 12 are values ​​obtained by multiplying the rotating machine currents iu, iv, iw by the resistance values ​​of the shunt resistors Ru, Rv, Rw, and are proportional to the currents iu, iv, iw. Therefore, the voltages VRu, VRu, VRw across the inverter 12 can be said to be values ​​of detected currents (detected values ​​of the rotating machine currents). The inverter 12 may be integrated with the rotating machine 10 (the integrated unit is called a power pack).

[0026] The controller 13 receives the torque command T_ref, the voltages VRu, VRu, VRw across the shunt resistors Ru, Rv, Rw, and the rotor position θ, and generates switching signals Gup to Gwn for driving the inverter 12 based on these. The controller 13 is a PWM controller realized by a discrete time calculator such as a microcomputer or a DSP (Digital Signal Processor). The controller 13 includes a current command value calculator 21, a current detector 22, a coordinate converter 23, a current controller 24 (voltage command value calculator), a coordinate converter 25 (voltage command value calculator), a corrected voltage generator 26 (voltage command value calculator), a PWM signal generator 27 (voltage command value calculator), and a speed calculator 28.

[0027] The current command value calculator 21 calculates current command values ​​id_ref, iq_ref, which are command values ​​(target values) of currents to be applied to the rotating machine 10, based on the torque command T_ref. For example, when the rotating machine 10 is a permanent magnet synchronous rotating machine, the current command value calculator 21 calculates the torque current command value iq_ref and the field-weakening current command value id_ref using the rotational angular velocity ω of the rotating machine 10 obtained by the speed calculator 28 in addition to the torque command T_ref, the DC bus voltage Vdc, and the rotor position θ.

[0028] Fig. 2 is a block diagram showing an internal configuration of the current command value calculator in the embodiment 1. As shown in Fig. 2, the current command value calculator 21 includes a torque command value generator 31 (torque current command value generator), a field weakening q-axis voltage calculator 32 (field weakening current command value generator), a field weakening target voltage calculator 33 (field weakening current command value generator), and a first field weakening current command value calculator 34 (field weakening current command value generator).

[0029] The torque command value generator 31 obtains the torque current command value iq_ref from the control command (here, the torque command T_ref). For example, when the rotating machine 10 is a rotating machine with no or small saliency, the torque command value generator 31 may obtain the torque current command value iq_ref by multiplying the torque command T_ref by the reciprocal (1 / Kt) of the torque coefficient Kt of the rotating machine 10. On the other hand, when the rotating machine 10 is a rotating machine with large saliency, the torque command value generator 31 may obtain the torque current command value iq_ref from the torque command T_ref in consideration of the reluctance torque.

[0030] The field-weakening q-axis voltage calculator 32 obtains the field-weakening q-axis voltage V1 based on the torque current command value iq_ref and the rotational angular velocity ω. Here, R and φ are the winding resistance and the flux linkage of the rotating machine 10, respectively. The equation shown in the block showing the field-weakening q-axis voltage calculator 32 in Fig. 2 is equal to "the q-axis voltage in the permanent magnet synchronous rotating machine, excluding the multiplication term of the inductance L of the rotating machine 10 and the q-axis current differential value diq / dt."

[0031] The field-weakening target voltage calculator 33 obtains the field-weakening target voltage V0 by using the torque current command value iq_ref, the rotational angular velocity ω, the DC bus voltage Vdc, and a first threshold value Kdc_1 in the modulation factor of the inverter 12. Here, the first threshold value Kdc_1 is given by the following equation (1). Kdc_1=Tmin / Tc …(1)

[0032] In the above formula (1), Tc is the period of the carrier triangular wave, and Tmin is the threshold (minimum value) of the on-time of the lower-arm switching elements Sun, Svn, and Swn at which the rotating machine current can be correctly detected by the shunt resistors Ru, Rv, and Rw. Details of these will be described later.

[0033] In the equation shown in the block representing the field weakening target voltage calculator 33 in FIG. 2, the first term on the right side is “effective line voltage Vdc1 (=Vdc×Kdc_1 / 2 0.5)" and the second term on the right-hand side is equal to "the square of the d-axis voltage in a permanent magnet synchronous rotating machine excluding the voltage drop term due to the d-axis current id." This formula includes a square root. If it is desired to reduce the processing load of the controller 13, this formula may be approximated using a Taylor expansion or a Maclaurin expansion.

[0034] The first field-weakening current command value calculator 34 outputs the first field-weakening current command value id_ref1 according to the equation shown in the block showing the first field-weakening current command value calculator 34 in Fig. 2. Specifically, the first field-weakening current command value calculator 34 compares the field-weakening q-axis voltage V1 obtained by the field-weakening q-axis voltage calculator 32 with the field-weakening target voltage V0 obtained by the field-weakening target voltage calculator 33. If the relationship is V1>V0, the first field-weakening current command value calculator 34 outputs a value calculated by the following equation (2) as the first field-weakening current command value id_ref1. id_ref1=(V0-V1) / (ω·L) …(2) On the other hand, when the relationship V1>V0 is not satisfied, the first field weakening current command value calculator 34 outputs "0" as the first field weakening current command value id_ref1.

[0035] Next, a description will be given of the PWM signal generator 27 shown in Fig. 1. The PWM signal generator 27 outputs PWM-modulated switching signals Gup to Gwn based on the modified voltage command values ​​vu', vv', and vw' output from the modified voltage generator 26.

[0036] 3 is a diagram for explaining the principle of generating switching signals in the embodiment 1. The PWM signal generator 27 generates switching signals Gup to Gwn by comparing the corrected voltage command values ​​vu′, vv′, vw′ with a carrier triangular wave (carrier wave) C having a period Tc (frequency fc).

[0037] Specifically, if the corrected voltage command value vu' is greater than the carrier triangular wave C, the PWM signal generator 27 turns on the switching signal Gup ("1") and turns off the switching signal Gun ("0"). Conversely, if the corrected voltage command value vu' is smaller than the carrier triangular wave C, the PWM signal generator 27 turns off the switching signal Gup ("0") and turns on the switching signal Gun ("1").

[0038] Furthermore, if the corrected voltage command value vv' is greater than the carrier triangular wave C, the PWM signal generator 27 turns the switching signal Gvp on ("1") and turns the switching signal Gvn off ("0"). Conversely, if the corrected voltage command value vv' is smaller than the carrier triangular wave C, the PWM signal generator 27 turns the switching signal Gvp off ("0") and turns the switching signal Gvn on ("1").

[0039] Furthermore, if the corrected voltage command value vw' is greater than the carrier triangular wave C, the PWM signal generator 27 turns on the switching signal Gwp ("1") and turns off the switching signal Gwn ("0"). Conversely, if the corrected voltage command value vw' is smaller than the carrier triangular wave C, the PWM signal generator 27 turns off the switching signal Gwp ("0") and turns on the switching signal Gwn ("1").

[0040] Incidentally, a short circuit prevention time (dead time) may be provided for the switching signals Gup to Gwn so that the upper arm switching elements Sup, Svp, Swp and the lower arm switching elements Sun, Svn, Swn of the inverter 12 are not turned on simultaneously.

[0041] The switching signals Gup to Gwn include a pattern in which all of the lower arm switching elements Sun, Svn, and Swn are turned on during one electrical angle period of the rotating machine 10. Specifically, a pattern in which all of the switching signals Gun, Gvn, and Gwn are turned on (1) is included, as in section D in FIG.

[0042] Here, the (PWM-shaped) voltage applied from the inverter 12 to the rotating machine 10 contains, in addition to the corrected voltage command component, a component that is an integer multiple of the period Tc of the carrier triangular wave C. Due to this, a current having a component that is an integer multiple of the period Tc is passed through the rotating machine 10, and depending on the value of the period Tc, the rotating machine 10 may make an abnormal noise.

[0043] In order to prevent such abnormal noise, for example, when the rotating machine 10 is used as a motor that assists steering of an electric power steering, the period Tc of the carrier triangular wave C may be set to 60 [μs] or less. By setting Tc=60 [μs], the frequency fc (=1 / Tc) of the abnormal noise becomes 16.6 kHz, which is unlikely to be a noise that is unpleasant to humans. More preferably, the period Tc of the carrier triangular wave C may be set to about 50 [μs]. By setting Tc=50 [μs], the frequency fc (=1 / Tc) of the abnormal noise becomes about 20 kHz, which is almost inaudible to humans. The frequency band that humans can hear is about 20 Hz to 20 kHz. In the following, the explanation will be given assuming Tc=50 [μs].

[0044] Next, the current detector 22 shown in Fig. 1 will be described. The current detector 22 outputs detection currents ius, ivs, iws using voltages VRu, VRu, VRw across the shunt resistors Ru, Rv, Rw and switching signals Gup-Gwn output from the PWM signal generator 27. Specifically, the current detector 22 acquires voltages VRu, VRu, VRw across the shunt resistors Ru, Rv, Rw at timing "V" shown in Fig. 3. This timing "V" is the timing when the carrier triangular wave C reaches a maximum value (DC bus voltage Vdc).

[0045] At timing "V", as shown in Fig. 3, all of the switching signals Gun, Gvn, and Gwn input to the lower-arm switching elements Sun, Svn, and Swn are on ("1"). Therefore, the current detector 22 can obtain the detection currents ius, ivs, and iws by dividing the voltages VRu, VRu, and VRw across the shunt resistors Ru, Rv, and Rw by -Ru, -Rv, and -Rw, respectively. Hereinafter, the detection method of obtaining the detection currents ius, ivs, and iws from the voltages VRu, VRu, and VRw across the shunt resistors Ru, Rv, and Rw is referred to as "three-phase detection".

[0046] 4 is a diagram showing an example of a change in the voltage across both ends in the first embodiment. As shown in FIG. 4, after the switching signal Gxn changes from "0" to "1", a fluctuation (e.g., a fluctuation over several [μs]) caused by the switching of the inverter 12, called ringing, occurs in the voltage across both ends VRx. The switching signal Gxn indicates one of the switching signals Gun, Gvn, and Gwn, and the voltage across both ends VRx indicates one of the voltage across both ends VRu, VRu, and VRw. When the voltage across both ends VRu, VRu, and VRw including such ringing are input to the current detector 22, the detected currents ius, ivs, and iws output from the current detector 22 have errors with respect to the currents iu, iv, and iw that actually flow through the rotating machine 10.

[0047] Here, to obtain accurate detection currents ius, ivs, iws, the on-time of the corresponding lower arm switching elements Sun, Svn, Swn must be longer than the threshold value Tmin set according to the ringing convergence time. In order to make the on-time of the lower arm switching elements Sun, Svn, Swn longer than the threshold value Tmin, the voltage input to the PWM signal generator 27 must be equal to or lower than the voltage (Vdc×Tmin / Tc) shown by the dashed line in Fig. 3. Therefore, to perform the above-mentioned "three-phase detection", the voltages of all three phases input to the PWM signal generator 27 must be equal to or lower than the voltage (Vdc×Tmin / Tc) shown by the dashed line in Fig. 3.

[0048] Fig. 5 is a diagram showing an example of a switching signal generated when the corrected voltage command changes in the first embodiment. As shown in Fig. 5, an increase in the voltage amplitude due to an increase in the rotation speed of the rotating machine 10 or the like may cause the corrected voltage command (in the example shown in Fig. 5, the corrected voltage command value vu') to take a large value close to the maximum value of the carrier triangular wave C (DC bus voltage Vdc). In such a case, the time difference between the time when the switching signal Gun switches from "0" to "1" and the timing "V" is small, and the both-end voltage VRu is affected by ringing.

[0049] In this way, when the ON time of any one of the switching signals Gun, Gvn, and Gwn is shorter than the threshold Tmin, the detection current for that phase may be generated from the other two phases. Hereinafter, this detection method is referred to as "two-phase detection." For example, as shown in FIG. 5, when the switching signal Gun is shorter than the threshold Tmin, the current detector 22 may obtain the detection current ius by the formula ius=-ivs-iws. When the switching signal Gvn is shorter than the threshold Tmin, the current detector 22 may obtain the detection current ivs by the formula ivs=-ius-iws. When the switching signal Gwn is shorter than the threshold Tmin, the current detector 22 may obtain the detection current iws by the formula iws=-ius-ivs.

[0050] The coordinate converter 23 performs coordinate conversion based on the detected currents ius, ivs, iws detected by the current detector 22 and the rotor position θ detected by the rotor position detector 11, and calculates the detected currents id, iq on the two rotation axes (d-axis, q-axis).

[0051] The current controller 24 calculates voltage command values ​​vd, vq on two rotation axes (d-axis, q-axis) based on the current command values ​​id_ref, iq_ref calculated by the current command value calculator 21 and the detected currents id, iq calculated by the coordinate converter 23. The current controller 24 includes a d-axis current controller 24d and a q-axis current controller 24q.

[0052] The d-axis current controller 24d applies a controller Gcd such as P control or PI control to the deviation (d-axis current deviation) between the current command value id_ref on the d-axis and the detected current id, and calculates a voltage command value vd on the d-axis to make the d-axis current deviation equal to "0". The q-axis current controller 24q applies a controller Gcq such as P control or PI control to the deviation (q-axis current deviation) between the current command value iq_ref on the q-axis and the detected current iq, and calculates a voltage command value vq on the q-axis to make the q-axis current deviation equal to "0".

[0053] The coordinate converter 25 converts the voltage command values ​​vd, vq on the two rotation axes (d-axis, q-axis) into coordinates based on the rotor position θ detected by the rotor position detector 11, and calculates voltage command values ​​vu, vv, vw on the three-phase coordinates.

[0054] The modified voltage generator 26 outputs modified voltage command values ​​vu', vv', vw' by adding an offset voltage voffset to the voltage command values ​​vu, vv, vw outputted from the coordinate converter 25. Fig. 6 is a flowchart showing the processing performed by the modified voltage generator in the first embodiment.

[0055] 6 is started, first, the corrected voltage generator 26 selects the smallest one of the voltage command values ​​vu, vv, and vw and sets it as Vmin (step S11). Next, the corrected voltage generator 26 sets Vmin as an offset voltage voffset using the DC bus voltage Vdc and Vmin calculated in step S11 (step S12). Then, the corrected voltage generator 26 subtracts the offset voltage voffset from the voltage command values ​​vu, vv, and vw to calculate corrected voltage command values ​​vu', vv', and vw' (step S13).

[0056] FIG. 7 is a diagram showing an example of waveforms of voltage command values ​​vu, vv, vw and corrected voltage command values ​​vu′, vv′, vw′ in the first embodiment. The graph shown in the upper part of FIG. 7 is a graph showing waveforms of voltage command values ​​vu, vv, vw, and the graph shown in the lower part is a graph showing waveforms of corrected voltage command values ​​vu′, vv′, vw′. However, in the graph shown in FIG. 7, the DC bus voltage Vdc=10V. Here, the voltage range that the inverter 12 can output is 0 (minimum value of the carrier triangular wave C) to Vdc (maximum value of the carrier triangular wave C). Therefore, when the DC bus voltage Vdc=10V, the voltage range that the inverter 12 can output is 0V to 10V as shown in FIG. 7.

[0057] In step S12 shown in Fig. 6, a process is performed in which Vmin is set as the offset voltage voffset, so that the minimum of the corrected voltage command values ​​vu', vv', vw' always coincides with the inverter output lower limit value, as shown in the lower graph of Fig. 7. This means that the corrected voltage command values ​​vu', vv', vw' are offset downward as equally as possible for all three phases without causing voltage saturation, and the on-times of the lower-arm switching elements Sun, Svn, Swn are made as long as possible. This is advantageous from the viewpoint of current detection in an inverter having shunt resistors Ru, Rv, Rw in series with the lower-arm switching elements Sun, Svn, Swn as in this embodiment.

[0058] The calculation method of the offset voltage voffset is not limited to the above-mentioned method. For example, in step S11 of FIG. 6, in addition to the process of selecting the smallest one of the voltage command values ​​vu, vv, and vw to set it as Vmin, the process of selecting the largest one of the voltage command values ​​vu, vv, and vw to set it as Vmax may be performed. Then, in step S12, the process of setting voffset to "(Vmax+Vmin) / 2" may be performed. In this way, the method of setting voffset=(Vmax+Vmin) / 2 is a conventional technique called third harmonic addition or HIP modulation. Also, two-phase modulation may be performed in which the upper arm switching element of the maximum phase is always in the on state.

[0059] The graph shown in Fig. 7 is for the case where the amplitude of the output line voltage of the inverter 12 is set to Kdc_1·Vdc. In this case, if the threshold value Tmin is 5 [μs], and Tc is 50 [μs], the first threshold value Kdc_1 is Kdc_1=Tmin / Tc=5 [μs] / 50 [μs]=0.9 from the above-mentioned formula (1). Referring to the graph shown in the lower part of Fig. 7, it can be seen that the voltage range of the corrected voltage command values ​​vu', vv', and vw' is 0 to 0.9 Vdc, and "three-phase detection" is always possible.

[0060] FIG. 8 is a diagram showing another example of the waveforms of the voltage command values ​​vu, vv, vw and the corrected voltage command values ​​vu′, vv′, vw′ in the first embodiment. The graph shown in the upper part of FIG. 8 is a graph showing the waveforms of the voltage command values ​​vu, vv, vw, and the graph shown in the lower part is a graph showing the waveforms of the corrected voltage command values ​​vu′, vv′, vw′. The graph shown in FIG. 8 is for the case where the amplitude of the output line voltage of inverter 12 is set to be larger than Kdc_1·Vdc. Referring to the graph shown in the lower part of FIG. 8, it can be seen that there are parts where the corrected voltage command values ​​vu′, vv′, vw′ exceed 0.9 Vdc, and that "two-phase detection" is always required.

[0061] As described above, in this embodiment, the first threshold value Kdc_1 in the modulation factor of the inverter 12 is defined (see the above-mentioned formula (1)). Then, a field weakening current equal to the first field weakening current command value id_ref1 (see the above-mentioned formula (2)) calculated by the first field weakening current command value calculator 34 is applied, so that the amplitude of the line voltage output from the inverter 12 is limited to Kdc_1 times the DC bus voltage Vdc.

[0062] Here, if the modulation factor of the inverter 12 is defined as "a value obtained by dividing the amplitude of the line voltage output from the inverter 12 by the DC bus voltage Vdc," then the modulation factor of the inverter 12 is limited by the first threshold value Kdc_1. This means that the field weakening current is limited so that the voltage range of the corrected voltage command values ​​vu', vv', vw' coincides with the three-phase detectable range shown in Fig. 7, and three-phase detection is always possible.

[0063] As described above, there are three-phase detection and two-phase detection as current detection methods for an inverter having shunt resistors Ru, Rv, and Rw in series with the lower-arm switching elements Sun, Svn, and Swn, such as the inverter 12 of this embodiment. Comparing these current detection methods, three-phase detection is better than two-phase detection. This is because three-phase detection is less affected by an offset error in one phase or an error in detection gain caused by an error in the resistance value of the shunt resistor than two-phase detection.

[0064] Furthermore, as shown in Fig. 8, in the two-phase detection section, the instantaneous value takes a value close to Vdc, as in the corrected voltage command value vu' shown in Fig. 5. Then, when that phase (U phase) switches near the current detection timing "V", the current detection of the other two phases (V phase, W phase) is affected, resulting in a current detection error. For this reason, in this embodiment, the first field weakening current command value id_ref1 is set so that three-phase detection is always performed, thereby sufficiently reducing the current detection error. This makes it possible to reduce torque ripple, vibration, and noise caused by current detection errors.

[0065] [Embodiment 2] Fig. 9 is a block diagram showing a configuration of a main part of a rotating machine control device according to embodiment 2 of the present disclosure. In Fig. 9, the same components as those shown in Fig. 1 are denoted by the same reference numerals. A rotating machine control device 2 according to this embodiment has a configuration in which the inverter 12 and the controller 13 included in the rotating machine control device 1 shown in Fig. 1 are replaced with an inverter 12a and a controller 13a, respectively.

[0066] The inverter 12a is configured such that the shunt resistor Rw of the inverter 12 shown in Fig. 1 is omitted. That is, the inverter 12a is configured such that the shunt resistors Ru, Rv are provided in series with the lower arm switching elements Sun, Svn, but no shunt resistor is provided with the lower arm switching element Suw. For this reason, in this embodiment, the voltages VRu, VRv across the shunt resistors Ru, Rv are input to the controller 13a.

[0067] The controller 13a has a configuration in which the current detector 22 included in the controller 13 shown in Fig. 1 is replaced with a current detector 22a. The current detector 22a outputs detection currents ius, ivs, iws using voltages VRu, VRu across shunt resistors Ru, Rv connected in series to the lower-arm switching elements Sun, Svn of the inverter 12a, respectively, and switching signals Gup-Gwn output from a PWM signal generator 27.

[0068] The current detector 22a acquires the voltages VRu, VRu across the shunt resistors Ru, Rv at the timing "V" shown in Fig. 3. At this timing, the switching signals Gun, Gvn, Gwn are all on ("1"). Therefore, the detected currents ius, ivs can be acquired by dividing the voltages VRu, VRu across the shunt resistors Ru, Rv by -Ru and -Rv, respectively. The detected current iws is calculated from the formula iws = -ius -ivs, taking into consideration that the sum of the currents (three-phase currents) flowing through the rotating machine 10 is 0.

[0069] In the control device 2 for a rotating machine of this embodiment, the first field weakening current command value id_ref1 described in the first embodiment is applied, so that the voltage range of the corrected voltage command values ​​vu', vv', vw' becomes 0 to Vdc×Tmin / Tc, as in the graph shown in the lower part of Fig. 7. Here, in the first embodiment, three-phase detection was always possible, but in this embodiment, since there are only two shunt resistors Ru and Rv, two-phase detection is always possible.

[0070] However, when the conventional field-weakening control technology is applied to the configuration of inverter 12a and current detector 22a, there is a problem that a section in which only one phase can be detected occurs when the voltage shown in Fig. 8 is output. This is because the present embodiment has a smaller shunt resistance than the configuration of embodiment 1 in which a two-phase detection section occurs.

[0071] Therefore, in this embodiment, the first field weakening current command value id_ref1 described in the first embodiment is applied to always perform two-phase detection. By always performing two-phase detection, the current of the remaining phase can also be calculated. This allows the controller 13a to perform current control based on the current information of the three phases.

[0072] Third Embodiment Fig. 10 is a block diagram showing a configuration of a main part of a rotating machine control device according to a third embodiment of the present disclosure. In Fig. 10, the same components as those shown in Fig. 1 are denoted by the same reference numerals. The rotating machine control device 3 according to this embodiment has a configuration in which the controller 13 included in the rotating machine control device 1 shown in Fig. 1 is replaced with a controller 13b. The controller 13b has a configuration in which the current command value calculator 21 included in the controller 13 shown in Fig. 1 is replaced with a current command value calculator 21b.

[0073] Fig. 11 is a block diagram showing an internal configuration of a current command value calculator in the embodiment 3. In Fig. 11, the same components as those shown in Fig. 2 are denoted by the same reference numerals. As shown in Fig. 11, the current command value calculator 21b includes, in addition to a torque command value generator 31, a modulation factor calculator 41 (field-weakening current command value generator), a subtractor 42 (field-weakening current command value generator), and a PI calculator 43 (field-weakening current command value generator).

[0074] The modulation factor calculation unit 41 calculates a modulation factor m expressed by the following formula (3) based on voltage command values ​​vd, vq on the two rotation axes (d-axis, q-axis) and the DC bus voltage Vdc. m = (vd 2 +vq 2 ) 0.5 / (Vdc / 2 0.5) …(3) A subtractor 42 calculates the difference (m-Kdc_1) between the modulation factor m and a first threshold value Kdc_1. A PI calculator 43 executes proportional-integral control to make the difference calculated by the subtractor 42 zero, and sets the output as a first field-weakening current command value id_ref1.

[0075] Here, when the sign of the execution result of the proportional-integral control is positive, the sign of the first field weakening current command value id_ref1 becomes positive. However, since the operation range of the rotating machine 10 cannot be expanded even if the field weakening current is made positive, a clip may be provided to correct the output of the PI calculator 43 to 0 when it is positive. Also, the proportional-integral gain of the PI calculator 43 may be set to vary inversely proportional to the rotational angular speed ω of the rotating machine 10.

[0076] As described above, in this embodiment, the current command value calculator 21b shown in Fig. 11 is provided instead of the current command value calculator 21 shown in Fig. 1, and the difference between the modulation factor m and the first threshold value Kdc_1 is set to 0. This makes it possible to correctly adjust the modulation factor m to the first threshold value Kdc_1 even if an error occurs between the values ​​of parameters (winding resistance R, inductance L, and flux linkage φ of the rotating machine 10) used in the field weakening target voltage calculator 33 shown in Fig. 2 and the true values.

[0077] Fourth embodiment Fig. 12 is a block diagram showing a configuration of a main part of a rotating machine control device according to a fourth embodiment of the present disclosure. In Fig. 12, the same components as those shown in Fig. 1 are denoted by the same reference numerals. A rotating machine control device 4 according to this embodiment has a configuration in which the controller 13 included in the rotating machine control device 1 shown in Fig. 1 is replaced with a controller 13c. The controller 13c has a configuration in which the current command value calculator 21 included in the controller 13 shown in Fig. 1 is replaced with a current command value calculator 21c.

[0078] Fig. 13 is a block diagram showing an internal configuration of a current command value calculator in the fourth embodiment. In Fig. 13, the same components as those shown in Fig. 2 are denoted by the same reference numerals. As shown in Fig. 13, the current command value calculator 21c is configured by adding a field-weakening target voltage calculator 53 (field-weakening current command value generator), a second field-weakening current command value calculator 54 (field-weakening current command value generator), a first field-weakening current command value upper and lower limit setter 55 (field-weakening current command value generator), a second field-weakening current command value upper and lower limit setter 56 (field-weakening current command value generator), and a selector 57 (field-weakening current command value generator) to the current command value calculator 21 shown in Fig. 2.

[0079] The field-weakening target voltage calculator 53 obtains the field-weakening target voltage V0′ by using the torque current command value iq_ref, the rotational angular velocity ω, the DC bus voltage Vdc, and a second threshold value Kdc_2 in the modulation factor of the inverter 12. Here, the second threshold value Kdc_2 is given by the following equation (4). Kdc_2 = Kmax … (4)

[0080] Kmax in the above formula (4) is the modulation range of the sine wave PWM and is generally set to "1", but may be set slightly lower than "1" in consideration of the dead time of the inverter 12. However, Kmax is a value larger than the first threshold value Kdc_1.

[0081] In the equation shown in the block representing the field-weakening target voltage calculator 53 in FIG. 13, the first term on the right side is “effective line voltage Vdc1 (=Vdc×Kdc_2 / 2 0.5 )" and the second term on the right-hand side is equal to "the square of the d-axis voltage in the permanent magnet synchronous rotating machine excluding the voltage drop term due to the d-axis current id." This formula includes a square root. If it is desired to reduce the processing load of the controller 13d, this formula may be approximated using a Taylor expansion or a Maclaurin expansion.

[0082] The second field weakening current command value calculator 54 outputs the second field weakening current command value id_ref2 according to the equation shown in the block showing the second field weakening current command value calculator 54 in Fig. 13. Specifically, the second field weakening current command value calculator 54 compares the field weakening q-axis voltage V1 obtained by the field weakening q-axis voltage calculator 32 with the field weakening target voltage V0' obtained by the field weakening target voltage calculator 53. If the relationship is V1>V0', the second field weakening current command value calculator 54 outputs a value calculated by the following equation (5) as the second field weakening current command value id_ref2. id_ref2=(V0′-V1) / (ω·L) …(5) On the other hand, when the relationship V1>V0' is not satisfied, the second field weakening current command value calculator 54 outputs "0" as the second field weakening current command value id_ref2.

[0083] Here, the first field-weakening current command value id_ref1 is a value that limits the modulation factor of the inverter 12 to a first threshold value Kdc_1 (see equation (1) above). On the other hand, the second field-weakening current command value id_ref2 is a value that limits the modulation factor of the inverter 12 to a second threshold value Kdc_2 (see equation (4) above).

[0084] The first field-weakening current command upper and lower limit setter 55 limits the upper limit of the first field-weakening current command value id_ref1 to 0 and the lower limit to idmax and -(Imax 2 -iq_ref 2 ) 0.5 The above Imax is the rated current of the rotating machine 10 or the inverter 12. The above idmax is the maximum value of the field weakening current, and is generally set to a value that prevents permanent demagnetization of the rotating machine 10.

[0085] Fig. 14 is a diagram for explaining the physical meaning of the process performed by the first field-weakening current command value upper and lower limit setter in the fourth embodiment. In Fig. 14, the vertical axis is the q-axis current Iq, and the horizontal axis is the d-axis current Id. The circle indicated by the dashed dotted line in Fig. 14 indicates the rated current Imax of the rotating machine 10 or the inverter 12. In other words, the inside of the circle indicated by the dashed dotted line indicates the range in which current can be passed within the rated current Imax of the rotating machine 10 or the inverter 12.

[0086] When the torque current command value iq_ref=iq_ref1, the conduction range of the first field weakening current command value id_ref1 is 0 to -(Imax 2 -iq_ref1 2 ) 0.5 Therefore, the first field weakening current command value id_ref1 is set (limited) to a range in which the resultant vector of the torque current command value iq_ref1 and id_ref1 does not exceed the rated current Imax of the rotating machine 10 or the inverter 12. However, -(Imax 2 -iq_ref1 2 ) 0.5 is the range of id_ref1 that can be energized from Imax and iq_ref1, and does not take into account the permanent demagnetization mentioned above. Therefore, the lower limit is -(Imax 2 -iq_ref1 2 ) 0.5 Select the larger of and idmax (the smaller in absolute value).

[0087] The second field weakening current command value upper and lower limit setter 56 limits the upper limit of the second field weakening current command value id_ref2 to 0 and the lower limit to idmax. A selector 57 outputs the first field weakening current command value id_ref1 output from the first field weakening current command value upper and lower limit setter 55 or the second field weakening current command value id_ref2 output from the second field weakening current command value upper and lower limit setter 56 as the field weakening current command value id_ref in accordance with the operation mode of the current command value calculator 21c. The operation modes of the current command value calculator 21c include the first to fourth modes shown below.

[0088] First mode: An operation mode in which the field weakening current command value id_ref is applied so as to satisfy the modulation factor m=Kdc_1. In this operation mode, the first field weakening current command value id_ref1 output from the first field weakening current command value calculator 34 in Fig. 13 is output as the field weakening current command value id_ref without being limited by the first field weakening current command value upper and lower limit setter 55.

[0089] Second mode: First field weakening current command value id_ref1 is -(Imax 2 -iq_ref1 2 ) 0.5 In this operation mode, the first field-weakening current command value id_ref1 output from the first field-weakening current command value calculator 34 in FIG. 13 is limited by the first field-weakening current command value upper and lower limit setter 55, and is set to id_ref=-(Imax 2 -iq_ref1 2 ) 0.5 will be output as:

[0090] Third mode: An operation mode in which the field weakening current command value id_ref is applied so as to satisfy the modulation factor m=Kdc_2. In this operation mode, the second field weakening current command value id_ref2 output from the second field weakening current command value calculator 54 in FIG. 13 is output as the field weakening current command value id_ref without being limited by the second field weakening current command value upper and lower limit setter 56. Note that the second field weakening current command value id_ref2 output from the second field weakening current command value calculator 54 is equal to the output (-(Imax 2 -iq_ref1 2 ) 0.5 ) (greater in absolute value).

[0091] Fourth mode: An operation mode in which the maximum value idmax of the field-weakening current is output as the first field-weakening current command value id_ref1. In this operation mode, the field-weakening current is limited due to issues such as permanent demagnetization of the rotating machine 10.

[0092] Fig. 15 is a diagram for explaining the operation of the current command value calculator in the fourth embodiment. The graph shown in the first row (top row) of Fig. 15 is a graph showing the change over time in the rotational angular velocity ω of the rotating machine 10. The graph shown in the second row is a graph showing the change over time in the field weakening current command value id_ref. The graph shown in the third row is a graph showing the change over time in the torque current command value iq_ref. The graph shown in the fourth row is a graph showing the change over time in the modulation factor m (= line voltage amplitude of the inverter 12 / DC bus voltage Vdc). The graph shown in the fifth row (bottom row) is a graph showing the change over time in the torque of the rotating machine 10.

[0093] 15 is divided into a graph group GR1 consisting of five graphs located on the left side and a graph group GR2 consisting of five graphs located on the right side according to the magnitude of the torque current command value iq_ref. Note that the graph group GR1 is for when the torque current command value iq_ref is relatively small, and the graph group GR2 is for when the torque current command value iq_ref is relatively large.

[0094] First, the graph group GR1 will be described. When the modulation factor m shown in the fourth graph reaches the first threshold value Kdc_1, the field weakening current command value id_ref (=first field weakening current command value id_ref1) is applied so as to satisfy m=Kdc_1 (first mode: (1) shown in the second graph). Then, when the field weakening current command value id_ref reaches the maximum value idmax of the field weakening current, the field weakening current command value id_ref is maintained at the maximum value idmax of the field weakening current (fourth mode: (4) shown in the second graph).

[0095] Next, the graph group GR2 will be described. When the modulation factor m shown in the fourth graph reaches the first threshold value Kdc_1, the field weakening current command value id_ref (=first field weakening current command value id_ref1) is applied so as to satisfy m=Kdc_1 (first mode: (1) shown in the second graph). After that, Imax 2 <id_ref 2 +iq_ref 2When the relationship is established, the operation mode of the current command value calculator 21c becomes the second mode (shown in the second graph as (2)). As a result, the field weakening current command value id_ref is set to -(Imax 2 -iq_ref1 2 ) 0.5 At this time, due to an increase in the rotational angular velocity ω of the rotating machine 10, the modulation factor m increases from the first threshold value Kdc_1 to the second threshold value Kdc_2.

[0096] When the modulation factor m=Kdc_2 is reached, the second field weakening current command value id_ref2 is applied as the field weakening current command value id_ref so as to satisfy this (third mode: (3) shown in the second graph). Then, when the field weakening current command value id_ref reaches the maximum value idmax of the field weakening current, the field weakening current command value id_ref is maintained at the maximum value idmax of the field weakening current (fourth mode: (4) shown in the second graph).

[0097] As described above, in this embodiment, first, the first field weakening current command value id_ref1 is applied as the field weakening current command value id_ref, and the modulation factor m is held at the first threshold value Kdc_1, thereby reducing noise of the rotating machine 10. Next, the first field weakening current command value id_ref1 is limited in accordance with the rated current Imax and the torque current command value iq_ref of the rotating machine 10 or the inverter 12, thereby applying the torque current command value iq_ref while suppressing the current applied to the rotating machine 10 to within the rated current Imax.

[0098] Next, the first field weakening current command value id_ref1 is compared with a second field weakening current command value id_ref2 with the modulation factor m set to a second threshold value Kdc_2 (maximum value that can be PWM modulated). When the second field weakening current command value id_ref2 becomes smaller (becomes larger in absolute value), the second field weakening current command value id_ref2 is supplied as the field weakening current command value id_ref.

[0099] In this manner, in this embodiment, the range in which the first field-weakening current command value id_ref1 is energized is maximized as much as possible (first mode), the torque current command value iq_ref is maintained while maintaining the rated current Imax (second mode), and the PWM modulation range of the rotating machine 10 by energization of the second field-weakening current command value id_ref2 is maintained (third mode). This makes it possible to achieve both quiet operation and maximum output.

[0100] The lower limit value idmax defined by the first field-weakening current command value upper and lower limit setter 55 and the second field-weakening current command value upper and lower limit setter 56 may be set to be larger (smaller in absolute value) than the value based on the permanent demagnetization of the rotating machine 10 described above in a predetermined case. The above-mentioned predetermined case includes a case where the controller 13c of the rotating machine 10 wants to limit the current supply due to heat generation of the inverter 12 or the rotating machine 10, a case where at least one part of the control device of the rotating machine 10 has failed, a case where the rotation speed of the rotating machine 10 is lower than a threshold value, etc. Here, when the rotation speed of the rotating machine 10 is lower than the threshold value, the lower limit value idmax may be set to 0.

[0101] Furthermore, when limiting the field weakening current to 0, the current command value calculator 21c may output the field weakening current command value id_ref as 0. In this case, it is sufficient to prevent calculations by the field weakening q-axis voltage calculator 32, the field weakening target voltage calculator 33, the first field weakening current command value calculator 34, the field weakening target voltage calculator 53, the second field weakening current command value calculator 54, the first field weakening current command value upper and lower limit setter 55, the second field weakening current command value upper and lower limit setter 56, and the selector 57 shown in FIG.

[0102] Fifth embodiment Fig. 16 is a block diagram showing a configuration of a main part of a rotating machine control device according to embodiment 5 of the present disclosure. In Fig. 16, the same components as those shown in Fig. 12 are denoted by the same reference numerals. The rotating machine control device 5 according to this embodiment has a configuration in which the inverter 12 and the controller 13c included in the rotating machine control device 4 shown in Fig. 12 are replaced with an inverter 12d and a controller 13d, respectively.

[0103] The inverter 12d is configured such that the shunt resistors Ru, Rv, and Rw of the inverter 12 shown in Fig. 12 are omitted, and one shunt resistor Rdc (current detector) is provided between the junction (connection point) of the lower arm switching elements Sun, Svn, and Swn and the ground. If the current flowing through the shunt resistor Rdc is Idc, the voltage VRdc across the shunt resistor Rdc is VRdc = Rdc x Idc. Therefore, in this embodiment, the voltage VRdc across the shunt resistor Rdc is input to the controller 13d.

[0104] The controller 13d has a configuration in which the current detector 22 and the corrected voltage generator 26 of the controller 13c shown in Fig. 12 are replaced with a current detector 22d and a corrected voltage generator 26d, respectively. The current detector 22d obtains a current Idc flowing through the shunt resistor Rdc by dividing the voltage VRdc across the shunt resistor Rdc output from the inverter 12d by the resistance value of the shunt resistor Rdc. The current detector 22d then uses, for example, a table shown in Fig. 17 to determine whether the obtained current Idc is 0 or is a current iu flowing through the winding U of the rotating machine 10, a current iv flowing through the winding V, or a current iw flowing through the winding W.

[0105] Fig. 17 is a diagram showing an example of a table used for determining a current in the current detector in the fifth embodiment. The table shown in Fig. 5 specifies whether the current Idc is 0 or any of the currents iu, iv, and iw for each combination of switching signals Gup to Gwn output from the PWM signal generator 27. Note that, although an example using a table has been described here, it is not essential to use a table.

[0106] The modified voltage generator 26d outputs modified voltage command values ​​vu', vv', vw' by adding an offset voltage voffset to the voltage command values ​​vu, vv, vw outputted from the coordinate converter 25. Fig. 18 is a flowchart showing the processing performed by the modified voltage generator in the fifth embodiment.

[0107] When the process of the flowchart shown in Fig. 18 is started, the modified voltage generator 26d first selects the smallest one of the voltage command values ​​vu, vv, and vw as Vmin, and selects the largest one of the voltage command values ​​vu, vv, and vw as Vmax (step S21). Next, the modified voltage generator 26d performs a process of setting the average value of Vmin and Vmax calculated in step S21 as an offset voltage voffset (step S22). That is, the modified voltage generator 26d performs a process of voffset = (Vmin + Vmax) x 0.5. Then, the modified voltage generator 26 performs a process of subtracting the offset voltage voffset from the voltage command values ​​vu, vv, and vw to calculate the modified voltage command values ​​vu', vv', and vw' (step S23).

[0108] FIG. 19 is a diagram showing an example of waveforms of the voltage command values ​​vu, vv, vw and the corrected voltage command values ​​vu′, vv′, vw′ in the fifth embodiment. The graph shown in the upper part of FIG. 19 is a graph showing waveforms of the voltage command values ​​vu, vv, vw, and the graph shown in the lower part is a graph showing waveforms of the corrected voltage command values ​​vu′, vv′, vw′. However, in the graph shown in FIG. 19, the DC bus voltage Vdc=10V as in the graph shown in FIG. 7. Therefore, the voltage range that the inverter 12d can output is 0 (minimum value of the carrier triangular wave C) to Vdc (maximum value of the carrier triangular wave C). Therefore, when the DC bus voltage Vdc=10V, the voltage range that the inverter 12d can output is 0V to 10V as shown in FIG. 19.

[0109] 19, at timing A, referring to the lower graph, the instantaneous value of the corrected voltage command values ​​vu', vw' is 9.15 [V], and the instantaneous value of the corrected voltage command value vv' is 0.85 [V]. Here, since the DC bus voltage Vdc=10V, the duties of the U-phase and W-phase are 91.5%, and the duty of the V-phase is 8.5%. Note that the duty here is the ratio of the time that the upper arm switching elements Sup, Svp, Swp are in the on state relative to the period Tc of the carrier triangular wave C.

[0110] FIG. 20 is a diagram showing an example of a switching signal output from a controller in the fifth embodiment. In the example shown in FIG. 20, voltage patterns V5(iw), V6(iv), V7(0), V6(iv), and V1(iu) are output in this order. On the other hand, the condition for detecting each phase current from Idc, which is the current flowing through the shunt resistor Rdc, is that the duration of each voltage pattern is longer than the threshold Tmin (5 [μs]). From FIG. 20, the duration of the voltage patterns V5(iw) and V1(iu) is 4.25 [μs], which is shorter than the threshold Tmin and therefore cannot be detected. Therefore, it is impossible to reproduce the three-phase current with the voltage amplitude shown in FIG. 19.

[0111] FIG. 21 is a diagram showing another example of the waveforms of the voltage command values ​​vu, vv, vw and the corrected voltage command values ​​vu′, vv′, vw′ in the fifth embodiment. The graph shown in the upper part of FIG. 21 is a graph showing the waveforms of the voltage command values ​​vu, vv, vw, and the graph shown in the lower part is a graph showing the waveforms of the corrected voltage command values ​​vu′, vv′, vw′. However, in the graph shown in FIG. 21, the DC bus voltage Vdc=10V as in the graph shown in FIG. 7. Therefore, the voltage range that the inverter 12d can output is 0 (minimum value of the carrier triangular wave C) to Vdc (maximum value of the carrier triangular wave C). Therefore, when the DC bus voltage Vdc=10V, the voltage range that the inverter 12d can output is 0V to 10V as shown in FIG. 19.

[0112] At timing A shown in FIG. 21, referring to the graph at the bottom, the instantaneous values ​​of the corrected voltage command values ​​vu′, vw′ are 8.46 [V], and the instantaneous value of the corrected voltage command value vv′ is 1.53 [V]. Here, since the DC bus voltage Vdc=10V, the duties of the U phase and W phase are 86.4%, and the duty of the V phase is 15.3%. Therefore, when this is expressed as a switching signal as shown in FIG. 20, the voltage patterns V5(iw) and V1(iu) have a duration of 7.65 [μm], which is longer than the threshold value Tmin and can be detected. Therefore, it is possible to reproduce the three-phase current with the voltage amplitude shown in FIG. 21.

[0113] Therefore, in this embodiment, the first threshold Kdc_1 is set to a value that can output a voltage pattern that can obtain at least two types of current from the currents iu, iv, and iw at a value equal to or greater than the threshold Tmin. This makes it possible to realize stable current control in an inverter 12d provided with only one shunt resistor as shown in Fig. 16 even when the rotating machine 10 rotates at high speed.

[0114] Sixth embodiment Fig. 22 is a block diagram showing the configuration of the main parts of a rotating machine control device and an electric power steering device according to a sixth embodiment of the present disclosure. In Fig. 22, the same components as those shown in Fig. 1 are given the same reference numerals. As shown in Fig. 22, an electric power steering device 100 of this embodiment includes a torque detector 103, a rotating machine 10, and a rotating machine control device 6, and applies a steering assist force to the steering mechanism of a vehicle such as an automobile.

[0115] 22 illustrates, as a steering mechanism of the vehicle, a steering wheel (handle) 101 operated by a driver and front wheels 102 driven by the operation of the steering wheel 101. As shown in FIG. 22, the rotating machine 10 is connected to the steering mechanism of the vehicle via a gear 104. Therefore, the driving force (steering assist force) of the rotating machine 10 is transmitted to the steering mechanism of the vehicle via the gear 104.

[0116] Torque detector 103 is disposed near steering wheel 101 and detects steering torque Ts applied by the driver. Rotating machine 10 is mounted on a steering column or rack shaft of the vehicle and generates a steering assist torque for steering wheel 101 under the control of rotating machine control device 6. Rotating machine control device 6 controls the current supplied to rotating machine 10 according to steering torque Ts detected by torque detector 103, thereby controlling the steering assist force applied to the steering mechanism of the vehicle.

[0117] The rotating machine control device 6 has a configuration in which the controller 13 included in the rotating machine control device 1 shown in Fig. 1 is replaced with a controller 13e. The controller 13e has a configuration in which the current command value calculator 21 included in the controller 13 shown in Fig. 1 is replaced with a current command value calculator 21e. The current command value calculator 21e differs from the current command value calculator 21 shown in Fig. 1 in the method of calculating the torque current command value iq_ref.

[0118] The current command value calculator 21e calculates a torque current command value iq_ref based on the steering torque Ts detected by the torque detector 103. For example, the current command value calculator 21e calculates the torque current command value iq_ref from the steering torque Ts by using the following equation (6). iq_ref = ka · Ts … (6)

[0119] In the above formula (6), ka is a constant, but it may be set to vary depending on the steering torque Ts or the vehicle running speed. Here, an example in which the "torque current command value iq_ref" is determined by the above formula (6) will be described, but known compensation controls according to the steering situation may be used in appropriate combination.

[0120] Fig. 23 is a diagram showing an example of the torque-rotation speed characteristics of the rotating machine in embodiment 6. In Fig. 23, for comparison, a graph showing the torque-rotation speed characteristics of a rotating machine in a conventional technology is shown in the upper part, and a graph showing the torque-rotation speed characteristics of the rotating machine in this embodiment is shown in the lower part.

[0121] In Fig. 23, the upper and lower graphs show (1) the locus of modulation factor m = Kdc_1, id = 0, (2) the locus of modulation factor m = Kdc_1, id = idmax, and (3) the locus of modulation factor m = Kdc_2, id = idmax. Here, noise increases when modulation factor m > Kdc_1.

[0122] In the conventional technology, the range where the noise becomes large is the region surrounded by the locus (1) and the locus (3). Thus, in the conventional technology, the range where the relationship of the modulation factor m>Kdc_1 holds is wide, and the period where the noise becomes large in the operation locus of the rotating machine 10 is long, which may cause audible discomfort. In contrast, in the present embodiment, the range where the noise becomes large is the region surrounded by the locus (2) and the locus (3) due to the improvement of the field weakening control. Thus, in the present embodiment, the range where the relationship of the modulation factor m>Kdc_1 holds can be significantly reduced compared to the conventional technology. Therefore, the period where the noise becomes large in the operation locus of the rotating machine 10 is significantly reduced, and audible discomfort is also significantly improved.

[0123] As described above, in this embodiment, the technology in the above-described first embodiment is applied to the control of the assist rotating machine of the electric power steering, and the range in which the first field weakening current command value id_ref1 is applied is maximized as much as possible. This provides unprecedented and remarkable operational effects, such as improved quietness of the electric power steering and maintenance of steering feel by maintaining the torque current command value iq_ref while maintaining the rated current Imax.

[0124] Although the first to sixth embodiments have been described above, the present disclosure is not limited to the above-mentioned embodiments, and can be freely modified without departing from the spirit of the present disclosure. For example, the rotating machine control device 6 in the sixth embodiment described above has the same configuration as the rotating machine control device 1 in the first embodiment. However, the rotating machine control device 6 in the sixth embodiment described above may also have the same configuration as the rotating machine control devices 2 to 5 in the second to fifth embodiments. Moreover, the first to sixth embodiments described above can also be combined as appropriate.

[0125] Each of the components of the rotating machine control devices 1-6 and the electric power steering device 100 described above has an internal computer system. A program for implementing the functions of each of the components of the rotating machine control devices 1-6 and the electric power steering device 100 described above may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read into a computer system and executed to perform processing in each of the components of the rotating machine control devices 1-6 and the electric power steering device 100 described above. Here, "reading a program recorded in a recording medium into a computer system and executing it" includes installing the program into the computer system. The "computer system" referred to here includes hardware such as an OS and peripheral devices.

[0126] Furthermore, a "computer system" may include multiple computer devices connected via a network including the Internet or communication lines such as a WAN, LAN, or leased line. Furthermore, a "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. In this way, the recording medium storing the program may be a non-transitory recording medium such as a CD-ROM.

[0127] The recording medium also includes a recording medium installed inside or outside the storage medium and accessible from a distribution server to distribute the program. The program may be divided into a plurality of parts, downloaded at different times, and then integrated by the respective components of the rotary machine control devices 1-6 and the electric power steering device 100, and each of the divided programs may be distributed by a different distribution server. Furthermore, the "computer-readable recording medium" includes a storage medium that holds a program for a certain period of time, such as a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network. The program may be a storage medium for implementing part of the above-mentioned functions. Furthermore, the program may be a so-called difference file (difference program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system. [Explanation of symbols]

[0128] 1 to 6... Rotating machine control device, 10... Rotating machine, 12, 12a, 12d... Inverter, 13, 13a to 13e... Controller, 24... Current controller, 25... Coordinate converter, 26, 26d... Corrected voltage generator, 27... PWM signal generator, 31... Torque command value generator, 32... Field weakening q-axis voltage calculator, 33... Field weakening target voltage calculator, 34... First field weakening current command value calculator, 41... Modulation factor calculator, 42... Subtractor, 43... PI calculator, 53... Field weakening target voltage calculator, 54... Second field weakening current command value calculator, 55... First field weakening current command value upper and lower limit setter, 56... Second field weakening current Upper and lower limit command value setter, 57...selector, 100...electric power steering device, 101...steering wheel, 102...front wheels, 103...torque detector, id_ref...field weakening current command value, id_ref1...first field weakening current command value, id_ref2...second field weakening current command value, iq_ref...torque current command value, Kdc_1...first threshold, Kdc_2...second threshold, m...modulation rate, Ru, Rv, Rw...shunt resistor, Rdc...shunt resistor, Sup, Svp, Swp...upper arm switching element, Sun, Svn, Swn...lower arm switching element, Vdc...DC bus voltage

Claims

1. an inverter that applies a voltage to a rotating machine; a current detector provided in the inverter for detecting a rotating machine current that is a current flowing through the rotating machine; a controller that outputs a voltage command value, which is a command value of the voltage, to the inverter based on a control command of the rotating machine; Equipped with The controller includes: a torque current command value generator that calculates a torque current command value based on the control command; A field weakening current command value generator that calculates a field weakening current command value; a voltage command value calculator that calculates the voltage command value based on the torque current command value and the field-weakening current command value; having the field-weakening current command value generator outputs, as the field-weakening current command value, a first field-weakening current command value that limits a modulation factor of the inverter to a first threshold value at which the current detector can detect at least two phases of the rotating machine current; A control device for rotating machines.

2. the inverter includes a switching element located in an upper arm and a switching element located in a lower arm, The current detector is provided in series with a switching element located in the upper arm or a switching element located in the lower arm, or in series with a DC bus. The control device for a rotating machine according to claim 1.

3. the current detector is provided in series with a switching element located in the lower arm of each phase of the inverter to detect three-phase currents of the rotating machine, the first threshold value is set to a modulation factor of the inverter at which the current detector can detect three-phase currents of the rotating machine; The control device for a rotating machine according to claim 2.

4. 4. The control device for a rotating machine according to claim 1, wherein the field-weakening current command value generator calculates the first field-weakening current command value based on a rotation speed of the rotating machine and a DC bus voltage of the inverter.

5. 5. The control device for a rotating machine according to claim 1, wherein the field-weakening current command value generator calculates the first field-weakening current command value based on a modulation factor obtained from the voltage command value corresponding to the rotating machine current.

6. 6. The rotating machine control device according to claim 1, wherein the field weakening current command value generator limits the first field weakening current command value when an overheat protection limit is applied to at least one location in the rotating machine control device.

7. 7. The rotating machine control device according to claim 1, wherein the field-weakening current command value generator limits the first field-weakening current command value when a failure is detected in at least one location of the rotating machine control device.

8. The control device for a rotating machine according to claim 1 , wherein the field-weakening current command value generator limits the first field-weakening current command value when a rotation speed of the rotating machine is lower than a threshold value.

9. 9. The control device for a rotating machine according to claim 1, wherein, when the first field-weakening current command value reaches a limit value, the controller outputs a second field-weakening current command value that limits a modulation rate of the inverter to a second threshold value that can limit the modulation rate of the inverter to a sinusoidal PWM modulation range.

10. 10. The control device for a rotating machine according to claim 9, wherein the field-weakening current command value generator limits the first field-weakening current command value based on the torque current command value and a rated current of the rotating machine or the inverter, and outputs a smaller one of the limited first field-weakening current command value and the limited second field-weakening current command value as the field-weakening current command value.

11. 11. The control device for a rotating machine according to claim 9, wherein the field-weakening current command value generator calculates the second field-weakening current command value based on a rotation speed of the rotating machine and a DC bus voltage of the inverter.

12. 11. The control device for a rotating machine according to claim 9, wherein the field-weakening current command value generator calculates the second field-weakening current command value based on a modulation factor obtained from the voltage command value corresponding to the rotating machine current.

13. 13. The rotating machine control device according to claim 9, wherein the field weakening current command value generator limits the second field weakening current command value when an overheat protection limit is applied to at least one location in the rotating machine control device.

14. 14. The rotating machine control device according to claim 9, wherein the field-weakening current command value generator limits the second field-weakening current command value when a failure is detected in at least one location of the rotating machine control device.

15. The rotating machine control device according to claim 9 , wherein the field-weakening current command value generator limits the second field-weakening current command value when a rotation speed of the rotating machine is lower than a threshold value.

16. a torque detector for detecting a steering torque of a steering wheel; a rotating machine that generates a steering assist torque for the steering; The control device for a rotating machine according to any one of claims 1 to 15, which controls driving of the rotating machine in response to the steering torque detected by the torque detector; An electric power steering device comprising:

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