JP2850091B2 - Sensorless inverter device with resistance fluctuation compensation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed sensorless type device in which an induction motor is driven by an inverter, and more particularly to a sensorless inverter device with resistance compensation which suppresses a characteristic change due to a temperature change.

[0002]

2. Description of the Related Art A conventional sensorless inverter device for controlling the torque and speed of an electric motor with high accuracy and high speed without attaching a speed detector to an induction motor is shown in FIG. FIG.
, 1 is an inverter, 2 is a current detector, 3 is a voltage detector, 4 is an induction motor (hereinafter simply referred to as a motor),
5 is a voltage system magnetic flux calculator, 61 is a current system magnetic flux calculator, 71
Is a speed calculator, 8 is a torque calculator, 9 is a speed controller, 1
0 is a torque magnetic flux controller.

[0005] The inverter 1 receives a switching signal output from the torque flux controller 10 and operates the inverter 1 in accordance with the switching signal. The output of the inverter 1 is connected to the motor 4 via the current detector 2 and the voltage detector 3, and the inverter 1 can apply a voltage to the motor 4. The voltage system magnetic flux calculator 5 is a current detector 2
The output current i and the voltage v output from the voltage detector 3 are input, and the magnetic flux ψi output from the current flux calculator 61 is input.
v is calculated by equation (1).

[0004]

(Equation 1)

Here, L1 is a primary self inductance,
L2 is a secondary self-inductance, M is a mutual inductance, R1 is a primary resistance, and K is a drift compensation gain.
The speed calculator 7 calculates the rotational speed ωm from the magnetic flux ψv and the current i according to equation (2).

[0006]

(Equation 2)

Here, ω is the rotational angular velocity of the magnetic flux ψv, and R 2 is the secondary resistance. The current system magnetic flux calculator 61 calculates the magnetic flux ψi by the equation (3).

[0008]

(Equation 3)

The torque calculator 8 calculates the torque T from the magnetic flux ψi and the current i and outputs the calculated torque T to the torque magnetic flux controller 10. In addition, the torque flux controller 10 receives a torque command T *, a flux command と *, and a flux 、 i, and outputs a switching signal such that the torque and the flux follow those commands.
Output to The speed controller 9 inputs the speed command ωm * and the calculated rotational speed ωm, and outputs a torque command T * such that the speed follows the command.

[0010]

As described above, in the prior art, the secondary resistance R2 is used in the calculation of the rotational speed ωm, but this value fluctuates depending on the temperature of the electric motor, and the value of ωm changes due to the temperature fluctuation.
An operation error occurs in m. Therefore, the speed control accuracy deteriorates.

[0011]

SUMMARY OF THE INVENTION The present invention has the following structure to solve the above-mentioned problems. Thus, the sensorless inverter device is provided with resistance fluctuation estimating means for estimating the secondary resistance fluctuation of the motor from the current of the output of the current detecting means and the operation time and outputting it to the speed calculating means.

In order to estimate a motor temperature rise immediately after the control power supply of the sensorless inverter is turned on, a charge / discharge circuit using a resistor and a capacitor, and a charge / discharge circuit after the control power supply of the sensorless inverter is turned on. Estimate the time the control power supply was off by measuring the capacitor voltage, and increase the motor temperature when the control power supply was turned on based on the time and the motor temperature rise value output from the resistance fluctuation estimating means when the control power supply was off. And an initial value measuring means for estimating a value and setting an initial value of the resistance fluctuation estimating means.

[0013]

[0014]

[0015]

The heat generated by the motor is almost entirely generated by the current flowing through the winding resistance of the motor, and the generated heat is considered to be proportional to the square of the current I. In addition, in consideration of the thermal resistance and the heat capacity with the outside air, the temperature rise θ of the electric motor can be approximated by a first-order lag as shown in Expression (4).

[0016]

(Equation 4)

Here, K is a conversion gain, and T is a time constant. The resistance of the winding is substantially proportional to the temperature, and therefore, the secondary resistance R2 can be estimated by equation (5).

[0018]

(Equation 5)

Here, K1 is a conversion coefficient between temperature and resistance, and R2n is a secondary resistance when the temperature of the motor is equal to the ambient temperature, and is set by the resistance measuring means.
In this way, the resistance fluctuation estimating means described in the above-described solving means estimates the fluctuation of the secondary resistance due to the temperature change by the above calculation.

Here, when the control power supply of the sensorless inverter is turned off, the calculation of the equation (4) cannot be performed. Therefore,
The initial value measuring means measures a value Vc1 of the capacitor voltage Vc of the charge / discharge circuit by the resistor and the capacitor immediately before the control power supply is turned off, and a value Vc2 immediately after the control power supply is turned on. Is estimated, and the time and the equation (4) immediately before the control power supply is turned off are estimated.
From the temperature rise value θ1, the motor temperature rise value immediately after the control power is turned on and the initial value θ0 of the formula (4) can be obtained according to the equation (4).

[0021]

[0022]

[0023]

[0024]

That is, in the initial value measurement, the temperature rise of the motor when the control power supply is turned on is obtained, and the resistance fluctuation estimating means estimates the temperature rise of the motor during operation, thereby reducing the fluctuation of the secondary resistance due to the temperature rise. The speed fluctuation due to the temperature fluctuation can be controlled by estimating and correcting the secondary resistance used for the speed calculating means.

[0026]

FIG. 1 shows a main part of an embodiment of the present invention. Reference numeral 62 denotes a current flux calculator, 72 denotes a speed calculator, and 1 denotes a speed calculator.
11 is a resistance fluctuation estimator, and 12 is a resistance measurement setting device.
In the figure, components having the same reference numerals as those in FIG. 3 indicate components having the same functions.

In such a circuit configuration, the resistance fluctuation estimator
111 inputs the current I, estimates the temperature rise of the motor 4 by equation (4), and estimates the secondary resistance fluctuation by equation (5).
The corrected secondary resistance R2 is output to the current flux calculator 62 and the speed calculator 72. R2n in equation (5) at that time is set by the resistance measurement setting device 12. As a result, the current-based magnetic flux calculator 62 and the speed calculator 72 can calculate using the corrected secondary resistance.

In FIG. 1, the temperature rise value of the motor immediately after the control power supply is turned on is undetermined, and the resistance fluctuation estimator 111
The initial value of the temperature rise value in Expression (4) cannot be set. Therefore, a configuration as shown in FIG. 2 is adopted. FIG. 2 shows an example of a circuit in which an example initial value measuring means according to the present invention is used.
12 is a resistance fluctuation estimator, 131 is an initial value measuring device, and 14 is a charge / discharge circuit. That is, the resistance fluctuation estimator 112
In addition, an initial value measuring device 131 as an initial value measuring means and the charging / discharging circuit 14 are added.

Here, in the charging / discharging circuit 14, 141 is a control power supply, 142 is a charging resistor, 143 is a charging diode, 14
4 is a discharge resistor and 145 is a capacitor. Initial value measuring instrument
131 is for obtaining the output of the capacitor 145 of the charge / discharge circuit 14, and measures the capacitor voltage immediately before the control power supply 141 is turned off and immediately after it is turned on. And the initial value measuring device 13
1 estimates the time during which the control power supply is off from the voltage ratio, estimates the temperature rise θ0 of the motor when the control power supply is turned on according to equation (4), and outputs it to the resistance fluctuation estimator 112. The resistance fluctuation estimator 112 sets this θ0 as an initial value of the equation (4).

[0030]

[0031]

As described above, according to the present invention, it is possible to provide a special device which suppresses deterioration of speed control accuracy due to secondary resistance fluctuation due to temperature rise of the induction motor.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a circuit in which an example initial value measuring unit according to the present invention is used.

FIG. 3 is a block diagram showing a conventional sensorless inverter device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter 2 Current detector 3 Voltage detector 4 Induction motor (motor) 5 Voltage system magnetic flux calculator 61 Ammeter flux calculator 62 Ammeter flux calculator 71 Speed calculator 72 Speed calculator 8 Torque calculator 9 Speed controller Reference Signs List 10 Torque flux controller 111 Resistance fluctuation estimator 112 Resistance fluctuation estimator 12 Resistance measurement setting device 131 Initial value measurement device 14 Charge / discharge circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02P 21/00 H02P 5/408-5/412 H02P 7/628-7/632

Claims (2)

(57) [Claims] A current detecting means for detecting an input current of the induction motor; a torque control means for controlling a torque of the induction motor; a speed calculation means for calculating a rotation speed of the induction motor; In a sensorless inverter device comprising: speed control means for causing the speed to follow the command value; and resistance measurement setting means for measuring the secondary resistance of the induction motor at a cold temperature and setting it in an inverter. A sensorless inverter device with resistance fluctuation compensation, comprising: resistance fluctuation estimation means for estimating a secondary resistance fluctuation from current and operation time and outputting the fluctuation to the speed calculating means. 2. A method of measuring a capacitor voltage of a charge / discharge circuit including a resistor and a capacitor immediately after a control power supply of a sensorless inverter device is turned on, thereby estimating a time when the control power supply is off, and controlling the control power supply time. An initial value measuring means is provided for estimating a motor temperature rise value when the control power supply is turned on from an estimated motor temperature rise value output from the resistance fluctuation estimating means when the power supply is turned off, and as an initial value of the resistance fluctuation estimating means. The sensorless inverter device with resistance fluctuation compensation according to claim 1.