JP4470445B2 - Method and apparatus for detecting motor cable resistance - Google Patents

Description

  The present invention relates to a method and an apparatus for detecting resistance of a motor and a cable connecting the motor and the inverter in a system in which the motor is driven by an inverter.

  In order to drive the synchronous motor, it is necessary to detect the magnetic pole position of the rotor and to control the energization to the stator winding based on the detected magnetic pole position. As a method for detecting the magnetic pole position of the rotor, a method using a sensor such as a rotary encoder, a method of performing calculation based on a motor model using a motor applied voltage and a motor supply current as inputs are known.

  It is also known that if the motor model can be accurately constructed, the magnetic pole position of the rotor can be accurately detected.

  However, since the length of the cable connecting the motor and the inverter is often not uniform, the uniform resistance set for the motor and the cable connecting the motor and the inverter is set in the motor model. In many cases, the resistance value does not match the resistance of the actual motor and the cable connecting the motor and the inverter.

  In such a case, if the magnetic pole position of the rotor is calculated using a motor model, the estimation error of the magnetic pole position increases according to the difference in resistance value, and if the estimation error increases, a desired torque may be output. In the worst case, there is a problem that the motor cannot be started or the motor reverses.

According to a first aspect of the motor cable resistance detection method of the present invention, the output of the inverter is supplied to the motor, the motor current is detected, and the magnetic pole position of the rotor of the motor is determined using the motor current, voltage, and motor model. detecting or estimating, in a system for controlling the inverter to the magnetic pole position as a reference, and executes the current control for the dc current command value, a resistance value including the motor and the cable from the current value and the applied voltage value at that time The current control is performed on the αβ axis that has undergone the three-phase to two-phase conversion, and the current control is performed with only one current control coordinate, and the current control coordinate is changed to the α axis or β depending on the magnetic pole position of the rotor. This is a method executed by switching to an axis .

A second aspect of the motor cable resistance detection method of the present invention is the motor cable resistance detection method according to the first aspect, wherein the current control is performed by setting current command values to positive and negative values, Execute with the set value .

In the third aspect of the motor cable resistance detection method of the present invention, the output of the inverter is supplied to the motor, the motor current is detected, and the magnetic pole position of the rotor of the motor is determined using the motor current, voltage, and motor model. In a system that detects or estimates and controls the inverter based on this magnetic pole position, executes current control for the DC current command value, and calculates the resistance value including the motor and cable from the current value and applied voltage value at that time The current control is performed by setting the current command value to a positive value and a negative value, and using the respective set values .

According to a fourth aspect of the motor cable resistance detecting method of the present invention, the output of the inverter is supplied to the motor, the motor current is detected, and the magnetic pole position of the rotor of the motor is determined using the motor current, voltage, and motor model. In a system that detects or estimates and controls the inverter based on this magnetic pole position, executes current control for the DC current command value, and calculates the resistance value including the motor and cable from the current value and applied voltage value at that time Then, the calculated resistance value is corrected using a correction function derived from a previously measured resistance value .

A motor cable resistance detection method according to a fifth aspect of the present invention is the motor cable resistance detection method according to the third or fourth aspect, wherein the current control is performed on an αβ axis that has undergone three-phase to two-phase conversion. To do .

A sixth aspect of the motor cable resistance detection method of the present invention is the motor cable resistance detection method according to any one of the first to fifth aspects, wherein the resistance value is calculated by performing current control. The voltage command values for the current value and the applied voltage value above are used.
A seventh aspect of the motor cable resistance detection method according to the present invention is the motor cable resistance detection method according to any one of the first to third, fifth and sixth aspects, wherein the calculated resistance value is calculated as follows. Correction is performed using a correction function derived from a resistance value measured in advance.
According to a first aspect of the motor cable resistance detecting apparatus of the present invention, the output of the inverter is supplied to the motor, the motor current is detected, and the magnetic pole position of the rotor of the motor is determined using the motor current, voltage, and motor model. In a system that detects or estimates and controls the inverter based on this magnetic pole position, executes current control for the DC current command value, and calculates the resistance value including the motor and cable from the current value and applied voltage value at that time Means for executing the current control on the αβ axis that has been subjected to the three-phase to two-phase conversion, and the current control is performed with only one current control coordinate and the current control by the magnetic pole position of the rotor. It is executed by switching the coordinates to the α axis or the β axis .
According to a second aspect of the motor cable resistance detection device of the present invention, there is provided the motor cable resistance detection device according to the first aspect, wherein the means sets the current control to a positive and negative current command value. However, each setting value is executed .
According to a third aspect of the motor cable resistance detection apparatus of the present invention, the output of the inverter is supplied to the motor, the motor current is detected, and the magnetic pole position of the rotor of the motor is determined using the motor current, voltage, and motor model. In a system that detects or estimates and controls the inverter based on this magnetic pole position, executes current control for the DC current command value, and calculates the resistance value including the motor and cable from the current value and applied voltage value at that time Means for setting the current command value to a positive value and a negative value, and executing the current control with respective set values .
According to a fourth aspect of the motor cable resistance detection device of the present invention, the output of the inverter is supplied to the motor, the motor current is detected, and the magnetic pole position of the rotor of the motor is determined using the motor current, voltage, and motor model. In a system that detects or estimates and controls the inverter based on this magnetic pole position, executes current control for the DC current command value, and calculates the resistance value including the motor and cable from the current value and applied voltage value at that time Means for correcting the calculated resistance value using a correction function derived from a resistance value measured in advance .
According to a fifth aspect of the motor cable resistance detection device of the present invention, there is provided the motor cable resistance detection device according to the third or fourth aspect, wherein the means is a ββ in which the current control is subjected to three-phase to two-phase conversion. To run on the axis .
A sixth aspect of the motor cable resistance detection device according to the present invention is the motor cable resistance detection device according to any one of the first to fifth aspects, wherein the means calculates the resistance value by performing current control. Is performed using a voltage command value for the current value and the applied voltage value on the axis on which is executed .
A seventh aspect of the motor cable resistance detection apparatus of the present invention is the motor cable resistance detection apparatus according to any one of the first to third, fifth and sixth aspects, wherein the means is calculated as described above. The resistance value is corrected using a correction function derived from a resistance value measured in advance .

According to the first to seventh aspects of the motor cable resistance detection method of the present invention and the first to seventh aspects of the apparatus , current control is executed for the DC current command value, and the current value and applied voltage at that time are executed. Since the resistance value including the motor and the cable is calculated from the value, the calculation accuracy of the resistance of the motor and the cable connecting the motor and the inverter can be increased. As a result, the motor model can be accurately constructed, and the magnetic pole position of the rotor can be accurately detected or estimated.

According to the first aspect of the motor cable resistance detection method and the first aspect of the motor cable resistance detection apparatus of the present invention, the current command value for current control at the time of resistance detection is set to the magnetic pole position of the rotor. By changing accordingly, current control can always be performed on an axis with a large current value, and the accuracy of resistance identification can be improved.

  In addition, since current always flows in the d-axis direction (the direction in which torque is not generated) according to the magnetic pole position of the rotor, the rotor can be held stationary. If the rotor moves after detecting the magnetic pole position, it is possible to prevent the occurrence of inconveniences such as a decrease in starting torque or reverse rotation in the worst case.

Further, according to the second and third aspects of the motor cable resistance detection method of the present invention and the second and third aspects of the motor cable resistance detection device, the current command value of the current control at the time of resistance detection is made positive or negative. By performing the current control with setting, the influence of the magnet magnetic flux can be reduced, and the accuracy of resistance identification can be improved.

Further, according to the fourth and seventh aspects of the motor cable resistance detection method of the present invention and the fourth and seventh aspects of the motor cable resistance detection device, the actual measurement measured in advance with respect to the resistance estimated value by the current control. By correcting with a correction function derived based on the value, a more accurate resistance estimation value can be obtained by simple calculation.

  Embodiments of a motor cable resistance detection method and apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing an embodiment of the motor cable resistance detecting apparatus of the present invention.

  This motor cable resistance measuring apparatus includes a current command setting unit 1, a current command sign setting unit 2 that sets a positive / negative value as a set current command, and an actual axis corresponding to the current command in which a positive / negative value is set. A difference calculation unit 3 that calculates a difference from the current, a PI calculation unit 4, a voltage synthesis unit 5, an inverter 6, a motor 7, a motor current detection unit 8, a three-phase to two-phase conversion unit 9, It has a voltage command setting unit 10, a motor cable resistance calculation unit 11, a motor cable resistance correction unit 12, and a rotor position angle detection unit 13.

  The current command setting unit 1 receives the current commands Iα_ref and Iβ_ref on the α-axis and β-axis by inputting the current command Iαβ_ref on the αβ coordinate system that has been converted from the three-phase to the two-phase, A detection method using a sensor, a detection method not using a position sensor), and using the rotor magnetic pole position (rotor position angle) θ detected in advance in the rotor position angle detection unit 13, any current command is set as a control target current command. Set as. Specifically, for example, when the rotor position angle θ is 0 <θ <45 degrees (electrical angle) or 135 degrees (electrical angle) <θ <180 degrees (electrical angle) with respect to the α-axis, α An axis current command is set, and when the rotor position angle θ is 45 degrees (electrical angle) <θ <135 degrees (electrical angle) with respect to the α axis, the β axis current command is set. When the rotor position angle θ is 180 degrees (electrical angle) or more, the above condition is applied to the value obtained by subtracting 180 degrees (electrical angle) from θ. Thereby, it becomes possible to control with the coordinate axis having the larger current value regardless of the position of the rotor, and the current control accuracy can be improved.

  However, when θ = 45 degrees (electrical angle) and θ = 135 degrees (electrical angle), any shaft current command may be set.

  The current command code setting unit 2 receives the set shaft current command as an input and outputs positive and negative current commands + I_ref and -I_ref alternately. By alternately outputting positive and negative current commands in this way, it is possible to cancel a non-linear characteristic difference (effect of magnet magnetic flux when a rotor has a magnet).

  The difference calculation unit 3 calculates the difference between the current command for which a positive / negative value is set and the actual current of the corresponding axis.

  The PI calculation unit 4 performs a PI control calculation as a current control calculation using the difference output from the difference calculation unit 3 as an input, and outputs the shaft voltage commands Vα and Vβ.

  The voltage synthesizer 5 synthesizes a voltage command Vαβ on the αβ coordinate system using the shaft voltages Vα and Vβ and the rotor position angle θ and supplies the voltage command Vαβ to the inverter 6 as a voltage duty command.

  The inverter 6 performs a switching operation of the switching element with a voltage duty command as an input, outputs AC power, and supplies the AC power to the motor 7.

  The motor current detector 8 detects the phase current of the motor current for three phases, for example, the motor currents Iu and Iv for two phases.

  The three-phase to two-phase conversion unit 9 performs a conventionally known three-phase to two-phase conversion operation using the detected motor currents Iu and Iv for two phases as inputs, and performs an actual current Iα on the α axis and β axis, Iβ is calculated and supplied to the difference calculation unit 3.

  Similar to the current command setting unit 1, the voltage command setting unit 10 sets one of the shaft voltage commands Vα and Vβ as a target voltage command in accordance with the rotor position angle θ.

  The motor cable resistance calculation unit 11 calculates {V (+) − V (−)} / {I (+) − I (−)} by using the set voltage command value and motor current. And the resistance R0 of the cable connecting the motor and the inverter is calculated.

  The motor cable resistance correction unit 12 is calculated in advance based on a relationship between a calculated value {R0 = m1 · L_cable + m0} and a measured value {R = K1 · L_cable + K0} with respect to the cable length (see FIG. 2). The resistance R0 is corrected using the correction formula {R = K1 (R0−m0) / m1 + K0}. K1 and m1 are slopes of R and R0, K0 and m0 are intercepts of R and R0, and L_cable is a cable length.

  In this way, by correcting the calculated value of the resistance value, it is possible to accurately calculate the resistance value without the influence of inductance, current detection error and the like.

  The operation of the motor cable resistance detection device having the above-described configuration is as follows.

The current command value is set on the α axis or β axis on the αβ axis that has been subjected to the three-phase to two-phase conversion based on the rotor position detected in advance. The setting is such that when the rotor position angle θ is 0 <θ <45 degrees (electrical angle) or 135 degrees (electrical angle) <θ <180 degrees (electrical angle) with respect to the α axis, the α axis is 45 degrees (electrical angle). ) If the angle <θ <135 degrees (electrical angle), set as β axis. In the case of 180 degrees (electrical angle) or more, the above condition is applied to the value obtained by subtracting 180 degrees (electrical angle) from the rotor position angle θ. As a result, control is possible with the coordinate axis having the larger current value regardless of the position of the rotor, and the current control accuracy is improved.

  As the current command value, positive and negative values are alternately set, and current control is executed in each of them. Thereby, when a rotor has a magnet, the influence by a magnet magnetic flux can be made constant irrespective of the polarity of a magnet.

  The current value is obtained by coordinate-converting the motor phase current (iu, iv, iw or any two) on the αβ axis and executing the current control using the current value on the axis where the current command value is set. The voltage command value obtained by the control calculation is converted from the rotor position angle θ into a vector on the d-axis, and the switching waveform of the inverter is generated using this value, for example, using the space vector method. As a result, current flows on the d-axis, and torque is not generated, so that it is possible to prevent the rotor position from changing. The switching waveform may be generated by performing two-phase to three-phase conversion and using PWM for each phase voltage command.

  The current command value is set to a positive and negative value, and the resistance value is calculated from the current value and the voltage command value when the current control is executed. As the voltage command value at this time, a more accurate result can be obtained by adopting a value obtained by detecting and correcting the voltage of the DC portion of the inverter 6.

  Actually, since the influence of inductance, current detection error, and the like are included, the actual resistance value becomes different as the motor cable length changes (see FIG. 2). Therefore, the resistance change with respect to the motor cable length is measured in advance, and a correction formula with the actual measurement value is held as a linear function, and the calculated value is corrected by using the correction function to estimate the resistance value with high accuracy. Is possible.

  FIG. 3 is a flowchart showing an embodiment of the motor cable resistance detection method of the present invention.

  In step SP1, the rotor magnetic pole position (rotor position angle) θ (for example, αβ subjected to three-phase to two-phase conversion) by a conventionally known method (for example, a detection method using a position sensor or a detection method not using a position sensor). The angle with respect to the α axis on the coordinate system is detected.

  In step SP2, the current control axis is set based on the detected rotor position angle θ. Specifically, for example, when the rotor position angle θ is 0 <θ <45 degrees (electrical angle) or 135 degrees (electrical angle) <θ <180 degrees (electrical angle) with respect to the α-axis, α An axis current command is set, and when the rotor position angle θ is 45 degrees (electrical angle) <θ <135 degrees (electrical angle) with respect to the α axis, the β axis current command is set. However, when θ = 45 degrees (electrical angle) and θ = 135 degrees (electrical angle), any shaft current command may be set.

  In step SP3, the sign of the set current command value is set to +.

  In step SP4, current control based on the current command value with the sign set to + is executed.

  In step SP5, the voltage command obtained by the current control is converted in the d-axis direction.

  In step SP6, the motor current value I (+) and the voltage command value V (+) are stored.

  In step SP7, it is determined whether or not the time (elapsed time after performing the processing in step SP3) exceeds a predetermined time T0.

  Then, the processing of step SP4, step SP5, and step SP6 is repeated until the time exceeds a predetermined time T0.

  If it is determined in step SP7 that the time has exceeded the predetermined time T0, the sign of the set current command value is set to-in step 8.

  In step SP9, current control based on a current command value with a sign set to-is executed.

  In step SP10, conversion processing of the voltage command obtained by current control in the d-axis direction is performed.

  In step SP11, the motor current value I (−) and the voltage command value V (−) are stored.

  In step SP12, it is determined whether or not the time (elapsed time after performing the processing in step SP8) exceeds a predetermined time T0.

  Then, the processing of step SP9, step SP10, and step SP11 is repeated until the time exceeds a predetermined time T0.

  If it is determined in step SP12 that the time has exceeded the predetermined time T0, in step SP13, the voltage command value is corrected using the voltage of the DC portion of the inverter.

  In step SP13, using the motor current value and the corrected voltage command value, the resistance value of the cable connecting the motor and the inverter to the motor is calculated.

  In step SP14, the resistance value is corrected using a correction formula calculated in advance based on the relationship between the calculated value of the resistance value with respect to the cable length and the actually measured value.

  Therefore, also in this embodiment, the resistance value can be estimated with high accuracy.

  As shown in FIG. 4, the time T0 is a time until the current is settled. The time T0 is measured in advance by a test or the like, and is set based on the measurement result. Then, until the time T0, the voltage command value and the current value are measured for each current control cycle, and finally the averaging process is performed. However, it is preferable not to measure current until T1, which is a transient state. Note that the time T1 may also be measured in advance by performing a test and set based on the measurement result.

  FIG. 5 is a flowchart for explaining an example of processing in which current measurement is not performed until T1.

  This flowchart is different from the flowchart of FIG. 3 in that it is determined whether or not the time has exceeded T1 between step SP5 and step SP6. If it is determined that the time has exceeded, the process of step SP6 is performed. If it is determined that the time has not been exceeded, it is determined whether or not the time has exceeded T1 between step SP10 and step SP11, at which point SP5a is inserted so that the processing of step SP4 is performed again. Between step SP7 and step SP8, the step SP10a that causes the processing of step SP11 to be performed when it is determined and the processing of step SP9 is performed again when it is determined that it has not been exceeded is inserted. In place of the point SP7a for averaging the current value and the voltage command value, and the process of step SP13, Current values, it is only in adopting a step SP13a performing averaging of the voltage command value.

  Therefore, in this case, the voltage command value and the current value can be measured for each current control period in the period from time T1 to T0, and finally the averaging process can be performed, and the resistance value is calculated based on the averaging process result. can do.

It is a block diagram which shows one Example of the motor cable resistance detection apparatus of this invention. It is a figure which shows an example of the relationship between the calculated value of resistance value with respect to cable length, and an actual value. It is a flowchart which shows one Example of the motor cable resistance detection method of this invention. It is a wave form diagram explaining the measurement period of an electric current value. It is a flowchart which shows the other Example of the motor cable resistance detection method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Current command setting part 2 Current command code | symbol setting part 3 Difference calculation part 4 PI calculating part 5 Voltage synthetic | combination part 6 Inverter 7 Motor 8 Motor current detection part 9 3-phase-2 phase conversion part 10 Voltage command setting part 11 Motor cable resistance calculation Unit 12 motor cable resistance correction unit 13 rotor position angle detection unit

Claims (14)

It supplies the output of the inverter to the motor, by detecting the motor current, motor current, inverter voltage, and using a motor model by detecting the magnetic pole position of the rotor of the motor, or estimates, based on the magnetic pole position In the system that controls
Execute current control for the DC current command value, calculate the resistance value including the motor and cable from the current value flowing through the motor and the applied voltage value applied to the motor at that time ,
The current control is executed on the αβ axis that has undergone three-phase to two-phase conversion, the current control is performed with only one current control coordinate, and the current control coordinate is switched to the α-axis or β-axis depending on the magnetic pole position of the rotor. The motor cable resistance detection method characterized by performing by this. The pre-SL current control, set the current command value to the positive and negative values, the motor cable resistance detecting method according to claim 1 to perform the respective set value. The output of the inverter is supplied to the motor, the motor current is detected, the motor current, voltage, and motor model are used to detect or estimate the magnetic pole position of the rotor of the motor, and the inverter is operated based on this magnetic pole position. In the controlling system,
Execute current control for the DC current command value, calculate the resistance value including the motor and cable from the current value flowing through the motor and the applied voltage value applied to the motor at that time,
A motor cable resistance detection method , wherein the current control is executed with current command values set to positive and negative values and respective set values . The output of the inverter is supplied to the motor, the motor current is detected, the motor current, voltage, and motor model are used to detect or estimate the magnetic pole position of the rotor of the motor, and the inverter is operated based on this magnetic pole position. In the controlling system,
Execute current control for the DC current command value, calculate the resistance value including the motor and cable from the current value flowing through the motor and the applied voltage value applied to the motor at that time,
A motor cable resistance detection method, wherein the calculated resistance value is corrected using a correction function derived from a previously measured resistance value . Motor cable resistance detecting method according to claim 3 or claim 4 running on αβ-axis in which the 3-phase to two-phase conversion of the current control. 6. The motor cable resistance detection method according to claim 1, wherein the resistance value is calculated using a voltage command value for the current value and the applied voltage value on an axis on which current control is executed. . Pre SL calculated resistance value, claims 1 to 3, is corrected using the correction function derived from previously measured resistance value, the motor cable resistance detection according to any one of claims 5 and 6 Method. It supplies the output of the inverter to the motor, by detecting the motor current, motor current, inverter voltage, and using a motor model by detecting the magnetic pole position of the rotor of the motor, or estimates, based on the magnetic pole position In the system that controls
Run the current control for the DC current command value, look including a means for calculating a resistance value including the motor and the cable from the current value and the applied voltage value applied to the motor through the motor at that time,
The means executes the current control on an αβ axis that has been subjected to three-phase to two-phase conversion, and the current control is performed with only one current control coordinate, and the current control coordinate is changed to the α axis or the axis depending on the magnetic pole position of the rotor. A motor cable resistance detection device, which is executed by switching to the β axis . Before SL means, said current control, set the current command value to the positive and negative values, the motor cable resistance detection apparatus according to claim 8 is intended to run on each setting value. The output of the inverter is supplied to the motor, the motor current is detected, the motor current, voltage, and motor model are used to detect or estimate the magnetic pole position of the rotor of the motor, and the inverter is operated based on this magnetic pole position. In the controlling system,
Including means for performing current control on the DC current command value and calculating a resistance value including the motor and the cable from a current value flowing through the motor and an applied voltage value applied to the motor at that time,
The motor cable resistance detection device according to claim 1, wherein the means executes the current control by setting a current command value to a positive value and a negative value, and executing the current control value at each set value . The output of the inverter is supplied to the motor, the motor current is detected, the motor current, voltage, and motor model are used to detect or estimate the magnetic pole position of the rotor of the motor, and the inverter is operated based on this magnetic pole position. In the controlling system,
Including means for performing current control on the DC current command value and calculating a resistance value including the motor and the cable from a current value flowing through the motor and an applied voltage value applied to the motor at that time,
The means corrects the calculated resistance value by using a correction function derived from a resistance value measured in advance . Before SL means, the motor cable resistance detection apparatus according to claim 10 or claim 11 is intended to run on αβ-axis in which the 3-phase to two-phase conversion of the current control. Before SL means, the calculation of the resistance value, any one of claims 8 to claim 12 is performed by using a voltage command value for the current value and the applied voltage value on the axis of executing the current control motor cable resistance detecting apparatus according to. Before SL means, the calculated resistance value, claim 10 claim 8 is corrected by using the correction function derived from previously measured resistance value, claim 12 and claim 13 The motor cable resistance detection device according to 1.

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