Temperature estimation device and temperature estimation method for PM motor

Abstract

To enhance magnet temperature estimation accuracy of a PM motor 1 driven by an inverter 2 provided with a current control system.SOLUTION: A temperature estimation device of a PM motor comprises: a parameter pre-identification device 30 for deriving a reference magnetic flux Φn, a temperature coefficient β, a d-axis inductance Ld, and a resistance Ra being parameters of the motor on the basis of voltage commands Vd* and Vq*, an electric angular velocity ωe, d-axis and q-axis current commands id* and iq*, d-axis and q-axis currents id and iq, and a magnet temperature measured value Tpm obtained by measuring a magnet temperature of the PM motor; a voltage error table calculator for calculating a q-axis voltage error value ΔVq on the basis of the Vd*, Vq*, ωe, id, iq, and Tpm, and the parameters of the motor Φn, β, Ld, and Ra; and a magnet temperature estimation unit for obtaining a magnet temperature estimation value on the basis of the voltage commands Vd* and Vq*, the d-axis and q-axis currents id and iq, the electric angular velocity ωe, and the calculated q-axis voltage error value ΔVq.SELECTED DRAWING: Figure 1

Claims

1. In a PM motor driven by an inverter equipped with a current control system, A q-axis voltage error calculation unit calculates a q-axis voltage error value ΔVq, which is the difference between the command value and the detected value of the q-axis voltage, based on the d-axis current id and q-axis current iq obtained by coordinate transformation of the PM motor's detected current to the dq axis. The voltage command Vd is obtained by performing current control so that the motor detection current, which is the current flowing through the PM motor, becomes equal to the current command. ＊ , Vq ＊ A PM motor temperature estimation device characterized by comprising: a magnet temperature estimation unit that calculates a magnet temperature estimate value based on the d-axis current id, the q-axis current iq, the electrical angular velocity ωe obtained by detecting the rotational speed of the PM motor, and the q-axis voltage error value ΔVq calculated by the q-axis voltage error calculation unit.

2. The voltage command Vd ＊ , Vq ＊ Electrical angular velocity ωe, d-axis current command id ＊ , q-axis current command iq ＊ The system includes a parameter identification unit that derives motor parameters that minimize the error between the estimated and measured values ​​of the magnet temperature, namely the reference magnetic flux Φn, temperature coefficient β, d-axis inductance Ld, and resistance Ra, based on the d-axis current id, q-axis current iq, and the measured magnet temperature Tpm of the PM motor. The q-axis voltage error calculation unit calculates the Vd ＊ , Vq ＊ , ωe, id ＊ , iq ＊ , id, iq, Tpm, and based on the motor parameters Φn, β, Ld, Ra derived by the parameter identification unit, calculates the q-axis voltage error value ΔVq by calculating equations (1), (2), and (3), and includes a voltage error table calculator [Math 1] [Math 2] [Math 3] (T^ Ｗ．０．ΔＶｑ This is the estimated magnet temperature without considering voltage error, T ０ (where is the reference temperature, Tpm is the magnetic temperature measurement value) The magnet temperature estimation unit uses the test data Vd ＊ , Vq ＊ The PM motor temperature estimation device according to claim 1, characterized in that an estimated magnet temperature is obtained by calculating equation (4) based on id, iq, ωe, motor parameters Φn, β, Ld, Ra derived by the parameter identification unit, and the q-axis voltage error value ΔVq calculated by the voltage error table calculator. [Math 4] (T^ is the estimated magnet temperature, T ０ (This is the reference temperature)

3. The q-axis voltage error calculation unit is Vd ＊ , Vq ＊ ,ωe,id ＊ , IQ ＊ The system includes a voltage error table calculator that calculates the q-axis voltage error value ΔVq by performing equations (1), (2), and (3) based on id, iq, Tpm, and the design parameters of the PM motor, namely the reference magnetic flux Φn, temperature coefficient β, d-axis inductance Ld, and resistance Ra. [Math 1] [Math 2] [Math 3] (T^ Ｗ．０．ΔＶｑ This is the estimated magnet temperature without considering voltage error, T ０ (where is the reference temperature, Tpm is the magnetic temperature measurement value) The magnet temperature estimation unit uses the test data Vd ＊ , Vq ＊ The PM motor temperature estimation device according to claim 1, characterized in that an estimated magnet temperature is obtained by calculating equation (4) based on id, iq, ωe and the q-axis voltage error value ΔVq calculated by the voltage error table calculator. [Math 4] (T^ is the estimated magnet temperature, T ０ (This is the reference temperature)

4. The q-axis voltage error calculation unit calculates the value of the voltage error table ΔVq_ ｖａｌｕｅ When f is a function of the surface and a is the parameter vector of the equation of the surface, ΔVq_ ｖａｌｕｅ The optimization problem is solved by deriving the parameter vector of the surface equation for which -f(Id, Iq, a) is minimized using equation (17). [Number 17] (a ＊ (where is the optimized parameter vector, and argmin is the set of values ​​that reach the minimum point.) The PM motor temperature estimation device according to claim 1, characterized in that the surface fitting equation is standardized using the parameter vector derived by equation (17), and the q-axis voltage error value ΔVq is calculated by inputting the d-axis current Id and q-axis current Iq during actual operation into equation (17).

5. The parameter identification unit calculates the magnetic flux Φ (=Vemf / ωe) using the induced voltage Vemf of the PM motor measured during no-load operation of the PM motor and the measured electrical angular velocity ωe obtained by detecting the rotational speed of the PM motor. The relationship between the measured magnet temperature Tpm of the PM motor and the calculated magnetic flux Φ is expressed by the least squares method straight line Φ = aTpm + b (where a is the slope of the line and b is the y-intercept of the line), and the temperature change of the magnetic flux is defined by Φ = Φn(1 + β(Tpm - T0)) (where Φn is the reference magnetic flux, β is the temperature coefficient, and T0 is the reference temperature). Thus, Φn and β are identified as motor parameters, and they correspond to each other. When the d-axis current command value Idcmd and the q-axis current command value Iqcmd are set to 0 and a constant-speed operation test of the PM motor is performed, the operating speed at which the estimated magnet temperature value estimated by the magnet temperature estimation unit is close to the measured magnet temperature value is determined to be a speed range in which a reasonable temperature estimation has been made. A constant-speed operation test is performed in the determined speed range with the d-axis current command value Idcmd < 0, the q-axis current command value Iqcmd = 0, or Idcmd > 0, Iqcmd = 0, and Vd at each Idcmd when Idcmd is changed in steps. ＊ , Vq ＊ Steady-state data of id, iq, ωe, and Tpm are acquired, and based on the acquired steady-state data, the optimization problem is solved using the evaluation formulas shown in equations (9) to (12) to find the combination of parameters d-axis inductance Ld and q-axis voltage error ΔVq that minimizes the squared error between the measured and estimated values ​​of the magnet temperature, thereby identifying the d-axis inductance Ld. [Number 9] submit to [Number 10] [Math 11] [Math 12] (T^ is the estimated magnet temperature, Ldn is the d-axis inductance, and ΔVq is the difference between the q-axis voltage command value and the q-axis voltage detection value.) In the speed range where a reasonable temperature estimation was determined, a constant-speed operation test was performed with the d-axis current command value Idcmd = 0, the q-axis current command value Iqcmd > 0, or Idcmd = 0, Iqcmd < 0, and Vd at each Iqcmd when Iqcmd was changed in steps. ＊ , Vq ＊ The PM motor temperature estimation device according to claim 2, characterized in that steady-state data of id, iq, ωe, and Tpm are acquired, and based on the acquired steady-state data, an optimization problem is solved by an evaluation formula that finds a combination of parameter resistance Ran and q-axis voltage error ΔVq that minimizes the squared error between the measured value and the estimated value of the magnet temperature, as shown in equations (13) to (16), and Ran is identified. [Number 13] submit to [Number 14] [Number 15] [Number 16] (T^ is the estimated magnet temperature, Ran is the winding resistance of the PM motor, and ΔVq is the difference between the q-axis voltage command value and the q-axis voltage detection value.)

6. A method for estimating the temperature of a PM motor driven by an inverter equipped with a current control system, The q-axis voltage error calculation unit calculates a q-axis voltage error value ΔVq, which is the difference between the command value and the detected value of the q-axis voltage, based on the d-axis current id and q-axis current iq obtained by coordinate transformation of the detected current of the PM motor to the dq axis. The magnet temperature estimation unit detects the current flowing through the PM motor, which is the test data. It then performs current control so that the detected motor current becomes equal to the current command, resulting in the voltage command Vd. ＊ , Vq ＊ A method for estimating the temperature of a PM motor, comprising: a magnet temperature estimation step of determining a magnet temperature estimate based on the d-axis current id, the q-axis current iq, the electrical angular velocity ωe obtained by detecting the rotational speed of the PM motor, and the q-axis voltage error value ΔVq calculated by the q-axis voltage error calculation unit.

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