JP5624284B2 - Motor drive system - Google Patents

Description

  The present invention relates to a motor drive system including an inverter that drives a variable magnetic flux motor capable of changing a magnetic flux.

  In recent years, a variable magnetic flux motor that can change a magnetic flux by magnetizing a low coercive force permanent magnet is known (see, for example, Patent Documents 1 and 2). Further, a motor drive system including a variable magnetic flux motor is disclosed (for example, see Patent Document 3).

JP 2006-280195 A JP 2008-048514 A JP 2008-125201 A

  However, in the motor drive system including the variable magnetic flux motor as described above, it is necessary to pass an excessive instantaneous current as a magnetizing current in order to magnetize the permanent magnet. A switching element such as an IGBT (insulated gate bipolar transistor) is used for an inverter that drives a variable magnetic flux motor. For this reason, when a magnetizing current is passed, the temperature of the switching element (junction temperature or channel temperature, etc.) rises rapidly. Therefore, when a magnetizing current is passed, the temperature of the switching element may exceed an allowable temperature (such as an allowable junction temperature or an allowable channel temperature).

  SUMMARY OF THE INVENTION An object of the present invention is to provide a motor drive system including a variable magnetic flux motor that can efficiently change the magnetic flux by flowing a magnetizing current without exceeding the allowable temperature of the switching element.

A motor drive system according to an aspect of the present invention includes a permanent magnet synchronous motor including a permanent magnet for changing a magnetic flux and a switching element, and converts DC power supplied from a DC power source into AC power. , An inverter for driving the permanent magnet synchronous motor, temperature detecting means for detecting the temperature of the switching element, and the magnetic flux of the permanent magnet synchronous motor by controlling the inverter within a temperature range allowed by the switching element. Magnetization current command determination means for determining a magnetization current command, which is a command for outputting a magnetization current for changing, based on the temperature of the switching element detected by the temperature detection means, and the magnetization current command determination means An inverter controller for controlling the inverter based on the magnetizing current command determined by With the door, the magnetizing current command determining means based on the detected temperature of the said switching elements by the temperature detecting means, and the magnetization current estimating means for estimating the magnetizing current to be outputted from the inverter, the magnetizing current estimation A table for determining the magnetization current command corresponding to the magnetization current estimated by the means, and the magnetization current command is selected from the table based on the magnetization current estimated by the magnetization current estimation means Selection means .

  ADVANTAGE OF THE INVENTION According to this invention, the motor drive system provided with the variable magnetic flux motor which can flow a magnetizing current efficiently and can change a magnetic flux, without exceeding the allowable temperature of a switching element can be provided.

1 is a block diagram showing a configuration of a motor drive system according to an embodiment of the present invention. The block diagram which shows the structure of the magnetization mode management part which concerns on this embodiment. The conceptual diagram which shows the selection table used for selection of the magnetization level by the magnetization level selection part which concerns on this embodiment. The conceptual diagram which shows the magnetization current table used in order to output the magnetization current command value by the magnetization current output part which concerns on this embodiment. The graph figure showing transition of the magnetization demand flag inputted into the magnetization level selection part concerning this embodiment. The graph showing transition of junction temperature input into the magnetization level selection part which concerns on this embodiment. The graph showing transition of the magnetization level output from the magnetization level selection part which concerns on this embodiment. The wave form diagram which shows the magnetization current sent through the variable magnetic flux motor which concerns on this embodiment. The graph which shows the motor output at the time of the motor start in the vehicle to which the motor drive system which concerns on this embodiment was applied.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment)
FIG. 1 is a block diagram showing a configuration of a motor drive system 1 according to an embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same part in subsequent figures, the detailed description is abbreviate | omitted, and a different part is mainly described. In the following embodiments, the same description is omitted.

  The motor drive system 1 includes an inverter 2, a DC power supply 3, a variable magnetic flux motor 4, a rotation angle sensor 5, AC current detectors 8 U and 8 W, and a control unit 10.

  The variable magnetic flux motor 4 is a permanent magnet synchronous motor that can change the magnetic flux. The rotor of the variable magnetic flux motor 4 is configured by incorporating a variable magnet into the rotor core. The variable magnet is a permanent magnet that changes the magnetic flux density (magnetic flux amount). Therefore, a magnetic material having a low coercive force is used for the variable magnet. By passing a magnetizing current from the inverter 2 to the variable magnetic flux motor 4, the variable magnet is magnetized or demagnetized. Thereby, the magnetic flux of the variable magnetic flux motor 4 changes such as magnetizing or demagnetizing. Whether the magnetic flux of the variable magnetic flux motor 4 is increased or decreased is determined by the rotational speed ω of the variable magnetic flux motor 4.

  The inverter 2 converts the DC power supplied from the DC power source 3 into three-phase AC power. The inverter 2 supplies the converted AC power to the variable magnetic flux motor 4. The inverter 2 drives the variable magnetic flux motor 4 by outputting AC power to the variable magnetic flux motor 4. The inverter 2 includes a power conversion unit including a plurality of switching elements SW. The switching element SW is, for example, an IGBT. Each switching element SW is provided with a temperature detection sensor SR that detects the junction temperature Tj. The temperature detection sensor SR outputs the detected junction temperature Tj as a signal to the control unit 10.

  The rotation angle sensor 5 detects the rotation angle of the rotor of the variable magnetic flux motor 4. The rotation angle sensor 5 outputs the detected rotation angle θ to the control unit 10.

  AC current detector 8U detects U-phase current Iu output from inverter 2. The AC current detector 8U outputs the detected U-phase current Iu as a signal to the control unit 10. AC current detector 8 </ b> W detects W-phase current Iw output from inverter 2. The AC current detector 8W outputs the detected W-phase current Iw to the control unit 10.

  The control unit 10 detects the torque command Tm *, the operation command Run *, the junction temperature Tj detected by the temperature detection sensor SR, the rotation angle θ detected by the rotation angle sensor 5, and the AC current detectors 8U and 8W, respectively. The inverter 2 is controlled based on the AC currents Iu and Iw that have been generated. The control unit 10 controls driving of the variable magnetic flux motor 4 and magnetic flux through the inverter 2.

  Here, the torque command Tm * is a command signal serving as a reference for torque to be output from the variable magnetic flux motor 4. The operation command Run * is a command signal that is “1” when the motor drive system 1 is operated and “0” when the motor drive system 1 is stopped.

  Next, control of the inverter 2 by the control unit 10 will be described with reference to FIG.

  The control unit 10 includes a pseudo-differentiator 11, a magnetic flux command calculation unit 12, a current reference calculation unit 13, a coordinate conversion unit 14, a voltage command calculation unit 15, a coordinate conversion unit 16, and a PWM (Pulse Width Modulation). This circuit includes a circuit 17, a gate command generation unit 18, a magnetization request generation unit 19, a magnetization mode management unit 20, and an adder AD1.

  The pseudo differentiator 11 differentiates the rotation angle θ input from the rotation angle sensor 5 to calculate a motor angular velocity (rotor rotation frequency, inverter frequency) ω. The pseudo differentiator 11 outputs the calculated motor angular velocity ω to the magnetic flux command calculation unit 12 and the voltage command calculation unit 15.

  An operation command Run * is input to the magnetic flux command calculation unit 12. The magnetic flux command calculation unit 12 calculates the magnetic flux command φ * based on the operation command Run * and the motor angular velocity ω input from the pseudo-differentiator 11. The magnetic flux command φ * is a command for controlling the magnetic flux of the variable magnetic flux motor 4. The magnetic flux command calculation unit 12 outputs the calculated magnetic flux command φ * to the current reference calculation unit 13, the magnetization request generation unit 19, and the magnetization mode management unit 20.

  The current reference calculation unit 13 receives the torque command Tm * and the magnetic flux command φ * calculated by the magnetic flux command calculation unit 12. The current reference calculation unit 13 calculates a magnetic flux current command value Id * and a torque current command value Iq * based on the torque command Tm * and the magnetic flux command φ *. The current reference calculation unit 13 outputs the calculated magnetic flux current command value Id1 * to the adder AD1. The current reference calculation unit 13 outputs the torque current command value Iq * to the voltage command calculation unit 15.

  The magnetic flux current command value Id1 * is a command value for controlling the magnetic flux current (d-axis current) Id that does not include the magnetizing current that flows to the variable magnetic flux motor 4. The torque current command value Iq * is a command value for controlling the torque current (q-axis current) Iq that flows through the variable magnetic flux motor 4. Here, the d axis on the dq axis is an axis in the magnet magnetic flux direction (an axis that does not act on the magnetic torque). The q axis on the dq axis is an axis (axis that acts on the magnetic torque) orthogonal to the axis in the magnetic flux direction (d axis).

  An operation command Run * is input to the magnetization request generator 19. The magnetization request generator 19 generates a magnetization request flag Frq based on the magnetic flux command φ * and the operation command Run * input from the magnetic flux command calculator 12. The magnetization request generation unit 19 outputs the generated magnetization request flag Frq to the magnetization mode management unit 20. The magnetization request flag Frq is a flag for requesting magnetization for changing the magnet magnetic flux of the variable magnetic flux motor 4. The magnetization request flag Frq is “0” when the magnet magnetic flux is not changed. The magnetization request flag Frq is “1” when the magnet magnetic flux is changed.

  In the magnetization mode management unit 20, the junction temperature Tj detected by the temperature detection sensor SR provided in the switching element SW of the inverter 2, the motor angular velocity ω calculated by the pseudo-differentiator 11, and the magnetization request generation unit 19 are generated. The magnetization request flag Frq is input.

  The magnetization mode management unit 20 determines the magnetization current command value Idm * based on the junction temperature Tj and the magnetization request flag Frq. The magnetization mode management unit 20 outputs the determined magnetization current command value Idm * to the adder AD1. The magnetizing current command value Idm * is a command value for controlling the magnetizing current passed through the variable magnetic flux motor 4.

  The adder AD1 receives the magnetic flux current command value Id * calculated by the current reference calculation unit 13 and the magnetization current command value Idm * corresponding to the magnetization level selected by the magnetization mode management unit 20.

  The adder AD1 adds the magnetic flux current command value Id1 * and the magnetization current command value Idm *, and calculates the magnetic flux current command value Id2 *. The magnetic flux current command value Id2 * is a command value for controlling the magnetic flux current (d-axis current) Id including the magnetizing current that flows to the variable magnetic flux motor 4. The adder AD1 outputs the calculated magnetic flux current command value Id2 * to the voltage command calculation unit 15.

  The coordinate conversion unit 14 receives the rotation angle θ detected by the rotation angle sensor 5 and the U-phase current Iu and the W-phase current Iw detected by the AC current detectors 8U and 8W. The coordinate conversion unit 14 converts the three-phase AC currents Iu and Iw output from the inverter 2 into dq-axis currents Id and Iq based on the rotation angle θ, the U-phase current Iu, and the W-phase current Iw. The coordinate conversion unit 14 outputs the calculated d-axis current (magnetic flux current) Id and q-axis current (torque current) Iq to the voltage command calculation unit 15.

  The voltage command calculation unit 15 includes the torque current command value Iq * calculated by the current reference calculation unit 13, the magnetic flux current command value Id2 * calculated by the adder AD1, and the motor angular velocity ω calculated by the pseudo-differentiator 11. Entered.

  The voltage command calculation unit 15 calculates the magnetic flux voltage command value Vd * and the torque voltage command value Vq * based on the magnetic flux current command value Id2 *, the torque current command value Iq *, the magnetic flux current Id, the torque current Iq, and the motor angular velocity ω. Is calculated. The voltage command calculation unit 15 outputs the calculated magnetic flux voltage command value Vd * and torque voltage command value Vq * to the coordinate conversion unit 16.

  The magnetic flux voltage command value Vd * is a command value for controlling the magnetic flux voltage (d-axis voltage). The torque voltage command value Vq * is a command value for controlling the torque voltage (q-axis voltage).

  The coordinate conversion unit 16 receives the rotation angle θ detected by the rotation angle sensor 5 and the dq axis voltage command values Vd * and Vq calculated by the voltage command calculation unit 15. The coordinate conversion unit 16 converts the dq-axis voltage command values Vd * and Vq * input from the voltage command calculation unit 15 based on the rotation angle θ into a three-phase AC U-phase voltage command Vu * and V-phase voltage command Vv. * And W phase voltage command Vw *. The coordinate conversion unit 16 outputs the calculated three-phase AC voltage commands Vu *, Vv *, Vw * to the PWM circuit 17.

  An operation command Run * is input to the gate command generator 18. The operation command Run * indicates the start of driving of the variable magnetic flux motor 4 or the stop of the variable magnetic flux motor 4. The gate command generator 18 generates a gate command Gst based on the operation command Run *. The gate command generation unit 18 outputs the generated gate command Gst to the PWM circuit 17.

  When starting to drive the variable magnetic flux motor 4, the gate command generator 18 changes the gate command Gst from “0” to “1”. Thereby, the inverter 2 starts a gate. When the variable magnetic flux motor 4 is stopped, the gate command generator 18 receives the operation command Run * indicating the stop of the variable magnetic flux motor 4, and after a predetermined time has elapsed, the gate command Gst is changed from “1” to “0”. Change to As a result, the inverter 2 is gated off after the variable magnetic flux motor 4 is free-running for a predetermined time. This free run is to reduce the induced voltage of the variable magnetic flux motor 4 and demagnetize the variable magnet.

  The PWM circuit 17 receives the three-phase AC voltage commands Vu *, Vv *, Vw * calculated by the coordinate conversion unit 16 and the gate command Gst generated by the gate command generation unit 18. When the gate command Gst is “1”, the PWM circuit 17 controls the inverter 2 by pulse width modulation (PWM) based on the voltage commands Vu *, Vv *, and Vw * input from the coordinate conversion unit 16. A gate signal GS is generated and output to the inverter 2. The PWM circuit 17 controls the drive of the switching element of the inverter 2 by outputting the gate signal GS to the inverter 2. Thereby, the output of the inverter 2 is controlled. When the gate command Gst is “0”, the PWM circuit 17 gates off the inverter 2.

  FIG. 2 is a block diagram illustrating a configuration of the magnetization mode management unit 20 according to the present embodiment.

  The magnetization mode management unit 20 includes a magnetization level selection unit 201 and a magnetization current output unit 202.

  The magnetization level selection unit 201 receives the junction temperature Tj detected by the temperature detection sensor SR provided in the switching element SW and the magnetization request flag Frq generated by the magnetization request generation unit 19.

  When the magnetization request flag Frq is “1” (when the magnetization request flag Frq is set), the magnetization level selection unit 201 selects one of the three levels of magnetization LV based on the junction temperature Tj. The magnetization level selection unit 201 outputs the selected magnetization level LV to the magnetization current output unit 202.

  When the magnetization request flag Frq is “0” (when the magnetization request flag Frq is not set), the magnetization level selection unit 201 ends the calculation process. Therefore, the magnetization mode management unit 20 does not output the magnetization current command value Idm *.

  The magnetization current output unit 202 receives the magnetization level LV selected by the magnetization level selection unit 201 and the motor angular velocity ω calculated by the pseudo-differentiator 11. The magnetization current output unit 202 outputs a preset magnetization current command value Idm * corresponding to the magnetization level LV selected by the magnetization level selection unit 201. The magnetizing current command value Idm * is determined in either direction of magnetizing or demagnetizing the variable magnetic flux motor 4 based on the motor angular velocity ω. When the magnetization level LV is not selected (or when the magnetization level LV is not input), the magnetization current output unit 202 does not output the magnetization current command value Idm *. That is, when the magnetization request flag Frq is “0”, the magnetization current output unit 202 does not output the magnetization current command value Idm *.

  FIG. 3 is a conceptual diagram showing a selection table TL1 used for selection of the magnetization level LV by the magnetization level selection unit 201 according to the present embodiment.

  The magnetization level selection unit 201 stores a selection table TL1. Three threshold temperatures TH1, TH2, and TH3 are set in the selection table TL1. Here, it is assumed that the relationship of threshold temperature TH1 <threshold temperature TH2 <threshold temperature TH3 holds. For example, if the allowable junction temperature THM of the switching element SW is 150 degrees, the threshold temperatures TH1, TH2, and TH3 are set to 100 degrees, 120 degrees, and 140 degrees, respectively.

  First, the magnetization level selection unit 201 determines whether or not the input junction temperature Tj is equal to or lower than the threshold temperature TH1. When it is determined that the junction temperature Tj is equal to or lower than the threshold temperature TH1, the magnetization level selection unit 201 outputs the magnetization level LV as the “magnetization level 1” to the magnetization current output unit 202.

  When the junction temperature Tj is higher than the threshold temperature TH1, the magnetization level selection unit 201 determines whether or not the junction temperature Tj is equal to or lower than the threshold temperature TH2. When it is determined that the junction temperature Tj is equal to or lower than the threshold temperature TH2, the magnetization level selection unit 201 outputs the magnetization level LV as the “magnetization level 2” to the magnetization current output unit 202.

  When the junction temperature Tj is higher than the threshold temperature TH2, the magnetization level selection unit 201 determines whether or not the junction temperature Tj is equal to or lower than the threshold temperature TH3. When it is determined that the junction temperature Tj is equal to or lower than the threshold temperature TH3, the magnetization level selection unit 201 outputs the magnetization level LV as the “magnetization level 3” to the magnetization current output unit 202. When the junction temperature Tj is higher than the threshold temperature TH3, the calculation process is terminated. Therefore, the magnetization mode management unit 20 does not output the magnetization current command value Idm *.

  FIG. 4 is a conceptual diagram showing a magnetizing current table TL2 used for outputting the magnetizing current command value Idm * by the magnetizing current output unit 202 according to the present embodiment.

  The magnetizing current output unit 202 stores a magnetizing current table TL2.

  The magnetization current output unit 202 selects a magnetization current command value Idm * corresponding to the magnetization level LV using the magnetization current table TL2.

  When the magnetization level LV is “magnetization level 1”, the magnetization current output unit 202 selects 800 [A] as the magnetization current command value Idm *. When the magnetization level LV is “magnetization level 2”, the magnetization current output unit 202 selects 400 [A] as the magnetization current command value Idm *. When the magnetization level LV is “magnetization level 3”, the magnetization current output unit 202 selects 200 [A] as the magnetization current command value Idm *.

  The magnetizing current output unit 202 outputs the magnetizing current command value Idm * so that a triangular wave having a time width of 10 milliseconds with the selected current value as the maximum value flows as the magnetizing current.

  Next, equations used to create the selection table TL1 and the magnetizing current table TL2 will be described.

  When the switching loss due to the IGBT is “P”, the turn-on loss is “Pton”, the turn-off loss is “Ptoff”, and the steady-on loss is “Pon”, the following equation is established.

P = Pton + Ptoff + Pon Equation (1)
The turn-on loss is expressed by the following equation where the turn-on switching energy is “Eton” and the carrier frequency is “fc”.

Pton = Eton × fc (2)
The turn-off loss is expressed by the following equation where the turn-off switching energy is “Etoff” and the carrier frequency is “fc”.

Ptoff = Etoff × fc (3)
The steady on-loss is represented by the following equation, where the magnetizing current (collector current) is “Ic” and the saturation voltage between the collector and the emitter is “Vce”.

Pon = Ic × Vce (4)
For the IGBT temperature rise “ΔT” when a magnetizing current is applied, the thermal resistance is “Rth”, the thermal time constant is “τ” using the switching loss “P” obtained by the equation (1), the magnetization If the time during which the current flows is “t”,

ΔT = P × Rth (1−exp (−t / τ)) (5)
Assuming that the junction temperature immediately before magnetization is “Tj1”, the junction temperature “Tj2” after magnetization is expressed as follows using Equations (1) to (5).

Tj2 = Tj1 + ΔT
= Tj1 + (Pton + Ptoff + Pon) × Rth (1-exp (−t / τ))
= Tj1 + (Eton × fc + Etoff × fc + Ic × Vce) × Rth (1-exp (−t / τ)) (6)
From the equation (7), the magnetizing current “Ic” is expressed as the following equation.

Ic = 1 / Vce ((Tj2−Tj1) / Rth (1−exp (−t / τ)) − fc (Eton + Etoff) (7)
Therefore, the junction temperature Tj detected by the temperature detection sensor SR is used as the junction temperature “Tj1” immediately before the magnetization, and the junction allowable temperature that can be allowed by the switching element SW is used as “Tj2” in the equation (7). Thus, it is possible to estimate the magnetization current that can flow through the switching element SW within a range that does not exceed the junction allowable temperature. Here, the range that does not exceed the allowable junction temperature is a range that is equal to or lower than a temperature that allows for a delay with respect to the allowable junction temperature.

  The selection table TL1 and the magnetizing current table TL2 are created by actually measuring and adjusting the values estimated in this way.

  With reference to FIGS. 5 to 8, the process of outputting the magnetization current command value Idm * in the magnetization mode management unit 20 according to the present embodiment will be described. FIG. 5 is a graph showing the transition of the magnetization request flag Frq input to the magnetization level selection unit 201. FIG. 6 is a graph showing the transition of the junction temperature Tj input to the magnetization level selection unit 201. FIG. 7 is a graph showing the transition of the magnetization level LV output from the magnetization level selection unit 201. FIG. 8 is a waveform diagram showing the magnetizing current Idm flowing through the variable magnetic flux motor 4. It is assumed that the junction temperature Tj shown in FIG. 6 is the junction temperature Tj detected by the temperature detection sensor SR provided in the switching element SW having the highest temperature.

  Here, as shown in FIG. 5, the case where the magnetization request flag Frq becomes “1” at the times t11, t21, and t31 will be described.

  First, at time t11, the magnetization request flag Frq is input to the magnetization level selection unit 201 as “1”.

  At time t11, as shown in FIG. 6, the junction temperature Tj input to the magnetization level selection unit 201 is equal to or lower than the threshold temperature TH1. Therefore, the magnetization level selection unit 201 selects the magnetization level 1 as the magnetization level LV. As shown in FIG. 7, the magnetization level selection unit 201 sets the magnetization level LV to the magnetization level 1 and outputs the magnetization level LV to the magnetization current output unit 202 from the time t11 to the time t12 when the magnetization current Idm flows.

  When the magnetization current output unit 202 receives the magnetization level LV as the magnetization level 1 from the magnetization level selection unit 201, the magnetization current Idm having a maximum value of 800 [A] flows to the variable magnetic flux motor 4 as shown in FIG. Thus, the magnetizing current command value Idm * is output.

  When the magnetizing current Idm flows between time t11 and time t12, the junction temperature Tj rises as shown in FIG. However, as described above, even when the magnetizing current Idm is supplied, the junction temperature Tj does not exceed the junction allowable temperature THM.

  Between time t12 and time t21, since the magnetizing current Idm is not passed, the switching element SW is cooled.

  Next, at time t <b> 21, the magnetization request flag Frq is set to “1” and input to the magnetization level selection unit 201.

  At time t21, as shown in FIG. 6, the junction temperature Tj input to the magnetization level selection unit 201 is higher than the threshold temperature TH1 and lower than the threshold temperature TH2. Therefore, the magnetization level selection unit 201 selects the magnetization level 2 as the magnetization level LV.

  Similarly to the period from time t11 to time t12, the variable magnetic flux motor 4 flows with a magnetization current Idm having a maximum value of 400 [A] corresponding to the magnetization level 2.

  Similarly, at time t31, the magnetization level 3 is selected, and from time t31 to time t32, the variable magnetic flux motor 4 receives a magnetization current Idm having a maximum value of 200 [A] corresponding to the magnetization level 3. .

  FIG. 9 is a graph showing the motor output when the motor is started in the vehicle to which the motor drive system 1 according to the present embodiment is applied.

  At the motor output operating point A0 before starting the motor, both the torque and the rotational speed are zero. At this time, it is assumed that the junction temperature Tj of the switching element SW is larger than the threshold temperature TH2 and lower than or equal to the threshold temperature TH3.

  Accordingly, the magnetizing current Idm corresponding to the magnetization level 3 flows through the variable magnetic flux motor 4. Thus, the variable magnetic flux motor 4 has a motor output characteristic P3 corresponding to the magnetization level 3. As a result, the variable magnetic flux motor 4 shifts from the motor output operating point A0 to the motor output operating point A1.

  When the vehicle travels, the switching element SW of the inverter 2 is cooled by the traveling wind. For this reason, the junction temperature Tj of the switching element SW is lowered.

  Next, when the magnetization request flag Frq is set when the junction temperature Tj becomes lower than the threshold temperature TH2, a magnetization current Idm corresponding to the magnetization level 2 flows through the variable magnetic flux motor 4. As a result, the variable magnetic flux motor 4 has a motor output characteristic P2 corresponding to the magnetization level 2. As a result, the variable magnetic flux motor 4 shifts from the motor output operating point A1 to the motor output operating point A2.

  Furthermore, when the magnetization request flag Frq is set when the inverter 2 is cooled by the traveling wind and becomes lower than the threshold temperature TH1, the variable magnetic flux motor 4 shifts from the motor output operating point A2 to the motor output operating point A3. To do.

  In this way, the motor drive system 1 changes the magnetic flux of the variable magnetic flux motor 4 by causing the magnetizing current Idm to flow as much as possible within a range where the switching element SW does not exceed the junction allowable temperature THM.

  According to this embodiment, the magnetizing current Idm output from the inverter 2 can be controlled based on the junction temperature Tj detected by the temperature detection sensor SR provided in the switching element SW. That is, the inverter 2 passes a preset magnetization current Idm based on the junction temperature Tj before magnetization. The preset magnetizing current Idm is a current value estimated as large as possible in a range where the junction temperature Tj after magnetization does not exceed the junction allowable temperature THM.

  Therefore, the motor drive system 1 determines the magnetizing current command value Idm * based on the junction temperature Tj of the switching element SW, thereby allowing the magnetizing current Idm to flow efficiently without exceeding the junction allowable temperature THM. The magnetic flux of the magnetic flux motor can be changed.

(Modification of the embodiment)
The embodiment can be carried out by being modified as follows.

  In the embodiment, the magnetization level LV is determined in accordance with the detected junction temperature Tj and the magnetization current Idm output from the inverter 2 is determined. However, the present invention is not limited to this. An arithmetic process may be performed on the detected junction temperature Tj, and the magnetizing current command value Idm * may be determined based on the result of the arithmetic process. For example, the magnetization mode management unit 20 uses the detected junction temperature Tj to calculate the maximum magnetization current that can flow within a range that does not exceed the junction allowable temperature THM using the above formulas (1) to (8). The magnetizing current command value Idm * may be determined based on the estimated magnetizing current. At this time, as in the embodiment, the magnetization current command value Idm * may be determined by determining the magnetization level LV based on the estimated magnetization current.

  In the embodiment, the rotation angle sensor 5 is provided to detect the rotation angle (phase) θ of the variable magnetic flux motor 4, but the present invention is not limited to this. The rotation angle θ of the variable magnetic flux motor 4 may be estimated based on the detected current value by detecting the output current of the inverter 4. Even if the rotation angle θ estimated in this way is used as a detection value, it is possible to obtain the same effect as that of each embodiment.

  In the embodiment, the variable magnetic flux motor 4 may be provided with a magnetized winding for changing the magnetic flux of the variable magnet provided in the rotor. Further, the motor drive system may be provided with a magnetizing circuit provided with a dedicated inverter or the like for causing a magnetizing current to flow through the magnetizing winding.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 1 ... Motor drive system, 2 ... Inverter, 3 ... DC power supply, 4 ... Variable magnetic flux motor, 5 ... Rotation angle sensor, 8U, 8W ... AC current detector, 10 ... Control part, 11 ... Pseudo differentiator, 12 ... Magnetic flux Command calculation unit, 13 ... Current reference calculation unit, 14 ... Coordinate conversion unit, 15 ... Voltage command calculation unit, 16 ... Coordinate conversion unit, 17 ... PWM circuit, 18 ... Gate command generation unit, 19 ... Magnetization request generation unit, 20 ... Magnetization mode management part, AD1 ... Adder, SR ... Temperature detection sensor, SW ... Switching element.

Claims (5)

A permanent magnet synchronous motor with a permanent magnet for changing the magnetic flux;
An inverter that is constituted by a switching element, converts DC power supplied from a DC power source to AC power, and drives the permanent magnet synchronous motor;
Temperature detecting means for detecting the temperature of the switching element;
A magnetizing current command that is a command for outputting a magnetizing current for changing the magnetic flux of the permanent magnet synchronous motor by the control of the inverter within the temperature range allowed by the switching element is detected by the temperature detecting means. Magnetizing current command determining means for determining based on the temperature of the switching element,
An inverter control means for controlling the inverter based on the magnetization current command determined by the magnetization current command determination means;
The magnetizing current command determining means includes
Magnetization current estimation means for estimating the magnetization current to be output from the inverter based on the temperature of the switching element detected by the temperature detection means;
A table for determining the magnetizing current command corresponding to the magnetizing current estimated by the magnetizing current estimating means;
A motor drive system comprising: selection means for selecting the magnetization current command from the table based on the magnetization current estimated by the magnetization current estimation means. The magnetizing current command determining means includes
A table for determining the magnetizing current command corresponding to the temperature of the switching element detected by the temperature detecting means;
The motor drive system according to claim 1, further comprising selection means for selecting the magnetization current command from the table based on the temperature of the switching element detected by the temperature detection means. A permanent magnet synchronous motor with a permanent magnet for changing the magnetic flux;
An inverter that is constituted by a switching element, converts DC power supplied from a DC power source to AC power, and drives the permanent magnet synchronous motor;
Temperature detecting means for detecting the temperature of the switching element;
A magnetization current for changing the magnetic flux of the permanent magnet synchronous motor by controlling the inverter within a temperature range allowed by the switching element is estimated based on the temperature of the switching element detected by the temperature detecting means. Magnetizing current estimating means for
A motor drive system comprising: inverter control means for controlling the inverter based on the magnetization current estimated by the magnetization current estimation means. An inverter control device configured to control a inverter configured of a switching element and configured to convert a DC power supplied from a DC power source to an AC power to drive a permanent magnet synchronous motor including a permanent magnet for changing a magnetic flux. ,
Temperature detecting means for detecting the temperature of the switching element;
A magnetizing current command that is a command for outputting a magnetizing current for changing the magnetic flux of the permanent magnet synchronous motor by the control of the inverter within the temperature range allowed by the switching element is detected by the temperature detecting means. Magnetizing current command determining means for determining based on the temperature of the switching element,
Control means for controlling the inverter based on the magnetization current command determined by the magnetization current command determination means;
With
The magnetizing current command determining means includes
Magnetization current estimation means for estimating the magnetization current to be output from the inverter based on the temperature of the switching element detected by the temperature detection means;
A table for determining the magnetizing current command corresponding to the magnetizing current estimated by the magnetizing current estimating means;
An inverter control device comprising: selection means for selecting the magnetization current command from the table based on the magnetization current estimated by the magnetization current estimation means. An inverter control device configured to control a inverter configured of a switching element and configured to convert a DC power supplied from a DC power source to an AC power to drive a permanent magnet synchronous motor including a permanent magnet for changing a magnetic flux. ,
Temperature detecting means for detecting the temperature of the switching element;
A magnetization current for changing the magnetic flux of the permanent magnet synchronous motor by controlling the inverter within a temperature range allowed by the switching element is estimated based on the temperature of the switching element detected by the temperature detecting means. Magnetizing current estimating means for
An inverter control device comprising: control means for controlling the inverter based on the magnetization current estimated by the magnetization current estimation means.

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