Control apparatus of field winding type motor

Abstract

To provide a technique for improving torque responsiveness of a field winding type motor.SOLUTION: A control apparatus of a field winding type motor generates d-shaft / q-shaft current command values to a stator coil on the basis of a torque target value, and a rotor current command value as a current command value to a field winding of a rotor. The control apparatus measures d-shaft / q-shaft actual current values flowing in the stator coil, and a rotor actual current value flowing in the field winding. The control apparatus controls a current flowing in the field winding so that the rotor actual current value tracks the rotor current command value. The control apparatus adds a correction value to each of the d-shaft current command value and the d-shaft current command value on the basis of a difference of the rotor actual current value and the rotor current command value. The control apparatus controls the current flowing in the stator coil so that the d-shaft actual current value tracks the d-shaft current command value after the correction value is added, and the q-shaft actual current value tracks the q-shaft current command value after the correction value is added.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The technology disclosed in this specification relates to a control device for a field winding type motor.

Background Art

[0002] A motor (field winding type motor) using an electromagnet instead of a permanent magnet for the rotor is known. The coil constituting the electromagnet of the rotor is called a field winding. Patent Document 1 discloses a technique for suppressing energy loss caused by the inductance of the field winding. The technique of Patent Document 1 suppresses energy loss by devising a circuit for flowing a current through the field winding.

[0003] In this specification, for convenience of explanation, a field winding type motor may be simply referred to as a motor. Also, what represents the current command value to the stator coil in the dq-axis space is referred to as the d-axis current command value and the q-axis current command value, and the current command value to the field winding of the rotor is referred to as the rotor current command value. Further, what represents the current flowing through the stator coil in the dq-axis space is referred to as the d-axis actual current value and the q-axis actual current value, and the current flowing through the field winding of the rotor is referred to as the rotor actual current value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Due to the inductance of the field winding, a delay occurs in the change of the rotor actual current value with respect to the change of the rotor current command value. Due to this delay, a delay occurs in the change of the output torque with respect to the change of the torque target value of the motor. That is, in a field winding type motor, the torque responsiveness becomes low due to the inductance of the field winding. This specification provides a technique for improving the torque responsiveness of a field winding type motor.

Means for Solving the Problem

[0006] This specification discloses a control device for a field winding type motor. The control device generates a d-axis current command value and a q-axis current command value, which are current command values for the stator coil, and a rotor current command value, which is a current command value for the field winding of the rotor, based on a torque target value. The control device measures a d-axis actual current value and a q-axis actual current value flowing through the stator coil, and a rotor actual current value flowing through the field winding. The control device controls the current flowing through the field winding so that the rotor actual current value follows the rotor current command value. If the rotor actual current value is smaller than the rotor current command value, the control device adds a positive correction value to each of the d-axis current command value and the q-axis current command value. If the rotor actual current value is larger than the rotor current command value, the control device adds a negative correction value to each of the d-axis current command value and the q-axis current command value. The control device controls the current flowing through the stator coil so that the d-axis actual current value follows the d-axis current command value after the correction value is added, and the q-axis actual current value follows the q-axis current command value after the correction value is added.

[0007] The control device disclosed in this specification corrects the d-axis / q-axis current command value according to the difference between the rotor current command value and the rotor actual current value. By correcting the d-axis / q-axis current command value, the shortage of the rotor actual current value with respect to the rotor current command value is compensated. By this control rule, the torque responsiveness of the field winding type motor is improved.

[0008] The details and further improvements of the technology disclosed in this specification will be described in the following "Mode for Carrying Out the Invention".

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0010] Referring to the drawings, the control device 2 of the embodiment will be described. FIG. 1 shows a block diagram of the control device 2 and the motor. The motor 200 is a field winding type. The motor 200 includes a three-phase coil (stator coil 201) wound around the stator and a rotor coil wound around the rotor. The rotor coil is referred to as the field winding 202. In FIG. 1, the dotted arrow line represents a signal line.

[0011] Current is supplied to the field winding 202 of the rotor via the slip ring and brush 203. A pair of conductive rings 203a, 203b are attached to the rotor, and a pair of conductive brushes 203c, 203d are fixed to the motor housing. Each of the pair of brushes 203c, 203d is in contact with each of the pair of rings 203a, 203b. The ring 203a (203b) and the brush 203c (203d) are electrically connected while sliding.

[0012] The control device 2 includes a controller main body 100, an inverter 180, and a field winding circuit 190. The inverter 180 converts the DC power of the DC power supply 300 into AC power suitable for driving the motor 200. The inverter 180 includes three sets of series-connected bodies of two switching elements. The three sets of series-connected bodies are connected in parallel to the DC power supply 300. When the six switching elements are appropriately turned on and off, AC is output from the midpoint of each of the three sets of series-connected bodies. A capacitor 301 is connected in parallel to the DC power supply 300. The capacitor 301 smoothes the output voltage (output current) of the DC power supply 300.

[0013] The field winding circuit 190 includes a switching element 191 and two diodes 192 and 193. The switching element 191 is connected between the positive electrode of the DC power supply 300 and the brush 203c. The diode 192 is connected between the brush 203c and the brush 203d. The cathode of the diode 192 is connected to the brush 203c, and the anode is connected to the brush 203d. The brush 203d is connected to the negative electrode of the DC power supply 300. The diode 193 prevents current from flowing backward from the brush 203c to the positive electrode of the DC power supply 300.

[0014] The inverter 180 and the field winding circuit 190 are controlled by the controller main body 100. More specifically, the switching elements of the inverter 180 and the switching element 191 of the field winding circuit 190 are controlled by the controller main body 100. The controller main body 100 sends an appropriate PWM signal (Pulse Width Moduration signal) to the switching elements of the inverter 180 so that the current flowing through the stator coil 201 follows the current command value. Also, the controller main body 100 sends an appropriate PWM signal to the switching element 191 so that the current (rotor actual current value) flowing through the field winding 202 follows the current command value (rotor current command value). The current flowing through the stator coil 201 is measured by the current sensor 206 and sent to the controller main body 100. The current flowing through the field winding 202 is measured by the current sensor 207 and sent to the controller main body 100. The motor 200 is equipped with a sensor 204 that measures the rotational speed and electrical angle of the rotor, and the measured values of the sensor 204 are also sent to the controller main body 100.

[0015] Fig. 2 shows a block diagram of the control system. In Fig. 2, the stator coil 201 and the field winding 202 of the motor 200 are shown, but the illustration of the slip ring and brush 203 (see Fig. 1) is omitted. In Fig. 2, the specific circuit configurations of the inverter 180 and the field winding circuit 190 are also not shown.

[0016] While referring to FIG. 2, the structure of the control system will be described. A torque target value (the target value of the output torque of the motor 200) is given from the upper controller to the controller main body 100. The control device 2 controls the currents flowing through the stator coil 201 and the field winding 202 so that the output torque of the motor 200 follows the torque target value.

[0017] The torque target value is converted into a d-axis current command value Idr, a q-axis current command value Iqr, and a rotor current command value Ifr by the torque / current converter 101. The rotor rotational speed W and the rotor electrical angle Th are used for the conversion from the torque target value to the d-axis current command value Idr and the q-axis current command value Iqr. Since the conversion formula from torque to d-axis / q-axis current is well known, a detailed description is omitted.

[0018] A predetermined known arithmetic expression is used for the conversion from the torque target value to the rotor current command value Ifr. In a simple example, the rotor current command value Ifr is generated by multiplying the torque target value by a predetermined coefficient.

[0019] The rotor current command value Ifr is input to the FF control module 112. Also, the difference dIf (the value obtained by subtracting the rotor actual current value Ifs from the rotor current command value Itr) between the rotor current command value Itr and the rotor actual current value Ifs is calculated by the differentiator 132b. The difference dIf is input to the FB control module 113. In the FF control module 112, known control rules such as the PID control rule and the PID control rule are applied to the rotor current command value Ifr, and an FF control value (feedforward control value) is generated. In the FB control module 113, known control rules such as the PID control rule and the PID control rule are applied to the difference dIf, and an FB control value (feedback control value) is generated. The FF control value is a control value for quickly bringing the rotor actual current value Ifs close to the rotor current command value Ifr. The FB control value is a control value for converging the difference dIf to zero. The FF control value and the FB control value are added by the adder 131c.

[0020] The sum of the FF control value and the FB control value of the rotor current command value Ifr becomes the voltage command value for the field winding 202 (rotor voltage command value Vfr). The rotor voltage command value Vfr is input to the driver 115. The driver 115 generates a PWM signal (Pulse Width Moduration signal) corresponding to the rotor voltage command value Vfr. The PWM signal output by the driver 115 is supplied to the switching element 191 of the field winding circuit 190. When the switching element 191 is turned on and off based on the PWM signal, current flows from the field winding circuit 190 to the field winding 202 so as to follow the rotor current command value Ifr. However, even if the rotor current command value Ifr changes stepwise, due to the inductance of the field winding 202, the rotor actual current value Ifs changes slowly with a predetermined time constant.

[0021] On the other hand, in the amplifier 116, the gain G is multiplied by the difference dIf (the value obtained by subtracting the rotor actual current value Ifs from the rotor current command value Ifr). The multiplication result GdIf of the difference dIf and the gain G becomes the correction value for the d-axis current command value Idr / q-axis current command value Iqr. In the adder 131a, the correction value GdIf is added to each of the d-axis current command value Idr / q-axis current command value Iqr.

[0022] The d-axis current command value Idr / q-axis current command value Iqr after the correction value addition is input to the FF module 102. Also, in the differentiator 132a, the difference between the d-axis current command value Idr after the correction value addition and the d-axis actual current value Ids, and the difference between the q-axis current command value Iqr after the correction value addition and the q-axis actual current value Iqs are calculated. Each difference (the output of the differentiator 132a) is input to the FB module 103.

[0023] In the FF module 102, existing control rules such as PI, PD, and PID are applied, and an FF control value (feedforward control value) for the d-axis current command value Idr / q-axis current command value Iqr after the correction value addition is generated. In the FB module 103, existing control rules such as PI, PD, and PID are applied to the output of the differentiator 132a, and an FB control value (feedback control value) for the difference between the current command value and the actual current value after the correction value addition is generated.

[0024] The FF control value and the FB control value are added by the adder 131b. The output of the adder 131b becomes the voltage command value for the stator coil 201. The output of the adder 131b is the voltage command value represented in the dq-axis space, that is, the d-axis voltage command value Vdr / q-axis voltage command value Vqr.

[0025] The d-axis voltage command value Vdr and the q-axis voltage command value Vqr are converted by the coordinate converter 104 into the voltage command values Vu / Vv / Vw for each of the three phases. The voltage command values Vu / Vv / Vw are input to the driver 105 and converted into PWM signals to be applied to the respective switching elements of the inverter 180.

[0026] The PWM signals output by the driver 105 are supplied to the respective switching elements of the inverter 180. When each switching element turns on and off based on the PWM signals, current flows through each coil of the stator coil 201 so as to follow the corrected d-axis current command value (Idr + GdIf) and the corrected q-axis current command value (Iqr + GdIf).

[0027] Note that the current sensor 206 measures the currents Iu, Iv, and Iw for each of the three phases. The currents Iu, Iv, and Iw for each of the three phases are converted by the coordinate converter 106 into the d-axis actual current value Ids / q-axis actual current value Iqs.

[0028] In the control block of FIG. 2, except for the path from the differentiator 132b to the adder 131a, since it is well known, detailed description is omitted.

[0029] The path from the differentiator 132b to the adder 131a means the following. That is, a value GdIf obtained by multiplying a value obtained by subtracting the rotor actual current value Ifs from the rotor current command value Ifr by a gain G is added to each of the d-axis current command value Idr and the q-axis current command value Iqr as a correction value. Put another way, this process is as follows. If the rotor current command value Ifr is greater than the rotor actual current value Ifs, the controller main body 100 adds a positive correction value GdIf to each of the d-axis current command value Idr and the q-axis current command value Iqr. If the rotor current command value Ifr is less than the rotor actual current value Ifs, the controller main body 100 adds a negative correction value GdIf to each of the d-axis current command value Idr and the q-axis current command value Iqr.

[0030] The advantages of the path from the differentiator 132b to the adder 131a will be described. Due to the inductance of the field winding 202, a change in the rotor actual current value Ifs appears with a delay with respect to a change in the rotor current command value Ifr. This delay reduces the torque responsiveness of the motor 200. In other words, the torque responsiveness decreases according to the difference dIf between the rotor current command value Ifr and the rotor actual current value Ifs. The path from the differentiator 132b to the adder 131a means correcting the d-axis current command value Idr / q-axis current command value Iqr according to the difference dIf. The control device 2 improves the torque responsiveness by correcting the d-axis current command value Idr / q-axis current command value Iqr according to the difference dIf.

[0031] Fig. 3 shows an example of the improvement in torque responsiveness. Fig. 3 shows graphs of torque, field current (rotor current), d-axis current, and q-axis current from top to bottom. The dotted graph G11 represents the torque target value. The torque target value changes stepwise at times T1 and T3. The dotted graph G21 shows the rotor current command value Ifr. The rotor current command value Ifr changes in the same form as the graph G11 of the torque target value. The solid graph G22 shows the rotor actual current value Ifs. Even if the rotor current command value Ifr changes stepwise, the rotor actual current value Ifs changes gently with a predetermined time constant due to the influence of the inductance of the field winding 202.

[0032] Graph G12 shows the output torque of the motor when the d-axis current command value Idr and the q-axis current command value Iqr are not corrected. When the current command values are not corrected, the output torque also changes gently in accordance with the gentle change (graph G22) of the rotor actual current value Ifs. Note that the dotted graphs G31 and G41 show the d-axis current command value Idr and the q-axis current command value Iqr before correction, respectively.

[0033] The solid-line graph G32 shows the d-axis current command value (Idr + GdIf) after adding the correction value. The solid-line graph G42 shows the q-axis current command value (Iqr + GdIf) after adding the correction value. From time T1 to T2, the rotor actual current value Ifs (graph G22) is smaller than the rotor current command value Ifr (graph G21). As the rotor actual current value Ifs becomes smaller, the d-axis current command value Idr / q-axis current command value Iqr increases due to correction. From time T1 to T2, as the magnetic force of the rotor field winding 202 weakens, the magnetic force of the stator coil 201 strengthens. As a result, the influence of the inductance of the field winding 202 is offset. The solid-line graph G13 shows the torque output when there is correction. By strengthening the magnetic force of the stator coil 201, an improvement in torque responsiveness can be seen.

[0034] From time T3 to T4, the rotor actual current value Ifs (graph G22) is larger than the rotor current command value Ifr (graph G21). As the decrease in the rotor actual current value Ifs is gentle, the d-axis current command value Idr / q-axis current command value Iqr decreases due to correction. From time T3 to T4, as the magnetic force of the rotor field winding 202 gradually weakens, the magnetic force of the stator coil 201 rapidly decreases. As a result, the influence of the inductance of the field winding 202 is offset. Also from time T3 to T4 in FIG. 3, an improvement in torque responsiveness can be seen.

[0035] In the control device 2 of the embodiment, the d-axis current command value Idr / q-axis current command value Iqr is corrected so as to compensate for the delay in the response of the rotor actual current value Ifs. The control device 2 improves the torque responsiveness by devising the control rule. Therefore, the field winding circuit 190 may have a simple configuration.

[0036] The field winding circuit 190 may have the following configuration. That is, a DC power supply 300 that supplies current to the field winding 202 and the field winding 202 are electrically connected by a pair of slip rings and brushes 203. The field winding circuit 190 includes a switching element 191 and two diodes 192 and 193. The switching element 191 is connected between the positive electrode of the DC power supply 300 and one brush 203c. The cathode of the diode 192 is connected to one brush 203c and the anode is connected to the other brush 203d. The diode 193 is connected in parallel with the switching element 191 so as to prevent the reverse flow of current from the brush 203c to the DC power supply 300. By appropriately turning on and off the switching element 191, the magnitude of the current flowing through the field winding 202 is controlled.

[0037] Points to note regarding the technology described in the embodiment are described. Except for the process of adding the correction value GdIf to the d-axis / q-axis current command value, one of various conventionally known control rules may be applied to the control rule for causing the d-axis (q-axis) actual current value to follow the d-axis (q-axis) current command value. The logic for generating the rotor current command value from the torque target value may be different from the logic of the embodiment.

[0038] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in this specification or the drawings can achieve a plurality of purposes simultaneously, and achieving one of those purposes itself has technical utility.

Description of Reference Numerals

[0039] 2: Control device 100: Controller body 101: Current converter 102, 112: FF module 103, 113: FB module 104, 106: Coordinate converter 105, 115: Driver 116: Amplifier 131a, 131b, 131c: Adder 132a, 132b: Differentiator 180: Inverter 190: Field winding circuit 191: Switching element 192, 192, 193: Diode 200: Motor 201: Stator coil 202: Field winding 203: Slip ring and brush 203a, 203b: Ring 203c, 203d: Brush 204: Sensor 206, 207: Current sensor 300: DC power supply 301: Capacitor

Claims

[Claim 1] A control device for a field winding type motor, generating a d-axis current command value and a q-axis current command value which are current command values ​​to the stator coil based on the torque target value, and a rotor current command value which is a current command value to the field winding of the rotor; measuring an actual d-axis current value and an actual q-axis current value flowing through the stator coil, and an actual rotor current value flowing through the field winding; controlling a current flowing through the field winding so that the actual rotor current value follows the rotor current command value; if the actual rotor current value is smaller than the rotor current command value, a positive correction value is added to each of the d-axis current command value and the q-axis current command value; if the actual rotor current value is greater than the rotor current command value, a negative correction value is added to each of the d-axis current command value and the q-axis current command value; a current flowing through the stator coil is controlled so that a d-axis actual current value follows the d-axis current command value after the addition of a correction value, and a q-axis actual current value follows the q-axis current command value after the addition of a correction value; Control device.

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