JP2005328635A - Controller of switched reluctance motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of a switched reluctance motor robust in the change of a wire wound resistor without using a position sensor. <P>SOLUTION: The controller of the switched reluctance motor includes a current differentiation detector 7 which assumes adjacent periods T1 and T2, and which outputs an average rate of change DI1 to the time of the T1 duration of the current of the wire winding of one phase of the switched reluctance motor 1, and an average rate of change DI2 to the time of the T2 duration; an average voltage detector 6 which outputs the average value V1 of the T1 period and the average value V2 of the T2 period of the voltage applied to the winding, an inductance arithmetic unit 8 which obtains the inductance of the winding by dividing the difference of the V1 and the V2 by the difference of the DI1 and the DI2; and a position estimator 9 which inputs the output of the inductance arithmetic unit and the current value of the winding and which estimates the rotor position of the switched reluctance motor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for a switched reluctance motor, and relates to a technique for estimating a rotor position without using a position sensor.

When controlling a switched reluctance motor, the torque direction changes depending on the positional relationship between the salient pole part of the stator and the salient pole part of the stator, and therefore a position sensor for detecting the position of the rotor is required. However, the position sensor increases the size of the system and decreases the reliability, and cannot be applied to a bad installation environment. Therefore, Patent Documents 1 and 2 propose a technique for controlling a switched reluctance motor without using a position sensor. In both of these documents, the number of phase flux linkages is obtained by time integration of the phase voltage minus the voltage drop due to the winding resistance, and the position is estimated from the phase flux linkage number and the phase current. .
JP-A-5-199794 Japanese Patent Laid-Open No. 2001-57771

  In the methods presented in Patent Document 1, Patent Document 2, and the like, it is indispensable to accurately obtain the number of interphase flux linkages. For this purpose, the winding resistance needs to be accurately grasped. That is, as described above, the number of phase flux linkages is obtained by time integration of the phase voltage minus the voltage drop due to the winding resistance, so it is used for phase flux linkage number calculations due to motor temperature fluctuations, etc. If an error appears in the winding resistance value, the error is integrated over time with the calculated value of the number of interphase flux linkages. The error in the number of phase flux linkages may cause an error in position estimation, and normal operation may not be possible.

  Therefore, the present invention assumes a period of time T1 and T2 adjacent to each other in a switched reluctance motor control apparatus, and an average rate of change DI1 of the current of one phase winding of the switched reluctance motor with respect to the time of the T1 period. A current differential detector that outputs an average rate of change DI2 with respect to time in the T2 period, and an average voltage detection that outputs an average value V1 in the T1 period and an average value V2 in the T2 period of the voltage applied to the winding. , An inductance calculator for determining the inductance of the winding by dividing the difference between V1 and V2 by the difference between DI1 and DI2, the output of the inductance calculator and the current value of the winding And a position estimator for estimating the rotor position of the switched reluctance motor.

  In the present invention, there is no need to obtain the number of interphase magnetic flux linkages, the inductance is obtained from the detected current and voltage, and the position is estimated from the current and the inductance, so the winding resistance value is not used. Even if the temperature fluctuates, the position estimation is not affected at all, and the above-mentioned problems can be solved.

  A switched reluctance motor can be operated without a position sensor and without using the resistance value of the winding.

FIG. 1 is a block diagram of one embodiment of the present invention. The drive circuit 4 applies a DC power source 5 to the three-phase windings Lu, Lv, Lw of the switched reluctance motor 1 in accordance with the switching signal output from the torque controller 10. The current detector 3 detects the current of each phase at a predetermined sample time. For example, as shown in FIG. 2, the current is detected at time points t1, t2, and t3, and the current values at the respective time points are I1, I2, and I3. The current differential detector 7 inputs the output of the current detector 3, and calculates the average rate of change DI1 with respect to the time of current from time t1 to time t2 and the average rate of change DI2 with respect to time of current from time t2 to time t3, for example, DI1 = (I2-I1) / T1 (1)
DI1 = (I3-I2) / T2 (2)
To obtain and output. Here, T1 = t2-t1 and T2 = t3-t2.

The voltage detector 2 detects and outputs a voltage applied to the winding. Alternatively, the switching signal input to the driving circuit 4 and the voltage of the DC power supply 5 may be estimated and output. The average voltage detector 6 calculates the average value of the voltage between the time t1 and the time t2 and the average value of the voltage between the time t2 and the time t3, and outputs them as V1 and V2. The inductance calculator 8 calculates L = (V2-V1) / (DI2-DI1) from the output of the current differential detector 7 and the output of the average voltage detector 6 (3)
By calculating the above, the winding inductance is obtained and output.

  The position estimator 9 uses an inductance L output from the inductance calculator 8 and an average value of current values output from the current detector 3 (for example, I = (I2 + I3) / 2) using a table or an approximate expression. Estimate and output rotor position. For example, the relationship between inductance, current, and position is shown in the graph shown in FIG. If this graph is stored as a table, the position can be obtained by referring to the table from the inductance and the current value. Further, by approximating the graph of FIG. 3 with a linear or quadratic function and approximating the coefficient with a function using a current value, the position can be obtained by an approximate expression.

  The torque controller 10 determines a phase to be excited based on the position information output from the position estimator 9 and outputs a switching signal so that a current corresponding to the torque command Tref flows in that phase.

The reason why the inductance is obtained by the equation (3) will be described below.
The voltage equation of the excitation phase is v = R · i + ω · i · dL / dθ + L · di / dt (4)
It is represented by In the period from t1 to t3, since the period is a very short time of 1 millisecond or less, it can be assumed that the first term, the second term, and L in the equation (4) do not change. Therefore, when the equation (4) is rewritten for the T1 period and T2 period, V1 = R · i + ω · i · dL / dθ + L · DI1 (5)
V2 = R · i + ω · i · dL / dθ + L · DI2 (6)
Thus, equation (3) is derived from the difference between both sides of equations (5) and (6).

  Without a position sensor, it is possible to operate a switched reluctance motor by estimating the position without using a winding resistance value that fluctuates depending on temperature, so it is possible to place the motor in a poor environment, and the possibility of industrial use is There is much.

It is explanatory drawing which showed the Example of this invention. It is an example of a phase voltage waveform, a current waveform, and a sample point. It is a relationship graph of an inductance, an electric current, and a position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Switched reluctance motor 2 Voltage detector 3 Current detector 4 Drive circuit 5 DC power supply 6 Average voltage detector 7 Current differential detector 8 Inductance calculator 9 Position estimator 10 Torque controller

Claims (1)

In the control device for the switched reluctance motor, assuming the adjacent periods T1 and T2, the average rate of change DI1 of the current of the one-phase winding of the switched reluctance motor with respect to the time of the T1 period and the time of the T2 period A current differential detector that outputs an average rate of change DI2 with respect to the winding, an average voltage detector that outputs an average value V1 of the voltage applied to the winding during the T1 period and an average value V2 of the T2 period, and the V1 And the difference between V2 and the difference between DI1 and DI2, an inductance calculator that obtains the inductance of the winding, and the output of the inductance calculator and the current value of the winding are input. Control of a switched reluctance motor comprising a position estimator for estimating a rotor position of the switched reluctance motor Location.

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