KR100305738B1 - Off-line parameter extracting method for induction motor - Google Patents

Abstract

The present invention relates to an offline parameter extraction method of an induction motor, and in the prior art, there is a problem in that parameter extraction of an electric motor installed in the actual site is impossible as the parameter is measured while constraining and rotating the induction motor. In addition, since all losses are calculated as resistance losses when calculating secondary resistance, the effect of iron loss is generated. As the measurement frequency increases, the value of iron loss increases to increase the error of the secondary resistance and perform no-load experiments. By calculating the inductance to zero and calculating mutual inductance, the inductance fluctuates according to the measured frequency as the slip of the motor does not become zero at substantially no load, resulting in severe vibration and heat generation when the induction motor is driven. There was a problem that can not drive the desired driving force. Therefore, the present invention was devised to solve the above-mentioned conventional problems. By constraining the induction motor in the industrial field, and measuring the parameter in the inverter, the performance of the different induction motors is compensated for the actual industrial site. It is effective in preventing a decrease. In addition, by calculating and compensating iron loss and motor slip, vibration, heat generation and rotational force during driving of the induction motor are prevented from being lowered, thereby smoothly driving the induction motor.

Description

OFF-LINE PARAMETER EXTRACTING METHOD FOR INDUCTION MOTOR}

The present invention relates to a method for extracting offline parameters of an induction motor, and in particular, in driving the induction motor through an inverter, the induction motor is measured by measuring various parameters of the induction motor in the inverter without additional equipment. The present invention relates to an offline parameter extraction method of an induction motor that allows the motor to be vector controlled.

In general, the induction motor must know the parameters of the induction motor accurately in order to operate like a DC motor by controlling the flux and the torque independently through a vector controlled inverter. In addition, it is difficult to obtain the same performance according to the induction motor and the performance varies depending on the driving conditions.

Here, the parameter of the induction motor is changed by the following factors.

① The same capacity may vary depending on the motor manufacturer and motor type.

② It changes according to the temperature.

③ Existing no load and restraint test is difficult to measure accurately.

④ Motor constants are not marked on the nameplate.

Accordingly, the vector control inverter controlling the induction motor controls the induction motor by measuring constants such as resistance values, leakage inductance, mutual inductance, etc. of the stator and the rotor of the induction motor.

In addition, one embodiment structure of a vector controller of a general induction motor is configured as shown in FIG. 1, and the operation thereof is as follows.

The difference between the speed command value wr ^* and the detected speed estimate wr is used to generate a reference value iqse ^* of the component current of the torque, and the reference value of the excitation current idse ^* is determined by the motor rated magnetic flux. The exciting current idse ^* is calculated through Equation 1 below.

Here, Lm is the mutual inductance value of the stator and the rotor, and E is the voltage applied to Lm.

And, by measuring the current (ias, ibs, ics) input to the actual motor 20 and converting it from three phases to two phases, the magnetic flux component current (idse) and the rotational force component current (iqse) to obtain the above The magnetic flux component voltage vse and the torque force component vqse are calculated using the difference from the current reference value idse ^* iqse ^* .

And, the motor slip (wslip) for the vector control is calculated using the following equation (2).

Here, Rr is the resistance value of the rotor, and Lr is the sum of the mutual inductance and the leakage inductance.

The motor synchronous angular velocity (we) is calculated by adding the motor slip (wslip) and the motor speed (wr), and the calculated synchronous angular velocity (we), the magnetic flux component voltage (vdse) and the torque force component voltage (vqse) are calculated. ) Outputs the voltage control signals (va, vb, vc) to the inverter (10).

And, the parameters of the induction motor 20. The induction vector control is exactly in order to be done the motor slip (wslip) and excitation current (idse ^*) of the electric motor 20 is to satisfy the above expressions (1) and equation (2) The measurement is accurate.

And, the method for measuring the parameters of the induction motor as shown in Figures 2 to 4 while driving the induction motor 20 in a restrained state and no load state to the existing ammeter 40, the voltmeter 40 and the power meter 50 By measuring the various parameters using the results of the measurement, it will be described in detail with reference to the induction motor equivalent circuit of FIG.

First, as shown in FIG. 2, the two-phase DC voltage Vdc applied to the input terminal of the induction motor 20 is measured through the voltmeter 40. At this time, the flowing current Idc is measured through the ammeter 30. The resistance value Rs of the stator, which is the winding resistance of one phase, is calculated by the following Equation 3.

When the induction motor 20 is operated at no load as shown in FIG. 3, since the slip of the induction motor 20 is 0, the secondary impedance Xlr (Rr / s) is ignored in the equivalent circuit of FIG. 5. In this case, the applied voltage is applied to the impedance (Xls) (Xm) and the resistance value (Rs) of the stator by the leakage inductance (Lls) and mutual inductance (Lm), respectively, wherein the applied voltage and current The measurement is performed using the voltmeter 40 and the ammeter 30, and the leakage and mutual inductance Lls (Lm) are calculated through Equation 4 below.

When the power supply Vb is applied while the induction motor 20 is restrained as shown in FIG. 4, the slip becomes 1 and the impedance of the secondary circuit connected in parallel with the impedance Xm due to mutual inductance Lm is obtained. Since the impedance (Xm) is ignored because (Xlr) (Rr / s) is relatively less than the impedance (Xm), at this time, it is applied to the induction motor 20 using the ammeter 30 and the power meter 50 When the input current Ib and the active power Pb at that time are measured, the secondary resistance Rr of the motor is calculated through Equation 5 below.

Therefore, the total impedance Zb and the leakage inductance Llr Lls are calculated through Equation 6 below.

As described above, there is a problem in that parameter extraction of the electric motor installed in the actual site is impossible as the parameters are measured while constraining and rotating the induction motor.

In addition, since all losses are calculated as resistance losses when calculating secondary resistance, the effect of iron loss is generated. As the measurement frequency increases, the value of iron loss increases to increase the error of the secondary resistance and perform no-load experiments. By calculating the inductance to zero and calculating mutual inductance, the inductance fluctuates according to the measurement frequency as the slip of the motor does not become zero at substantially no load, resulting in severe vibration and heat generation when the induction motor is driven. There was a problem that can not drive the desired driving force.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and induction of the vector control of the induction motor by measuring various parameters of the induction motor in the inverter without additional equipment while the induction motor is installed. The purpose is to provide an offline parameter extraction method of the motor.

1 is a block diagram showing an embodiment configuration of a vector controller of a general induction motor.

Figure 2 is a block diagram showing a current measuring method when applying a DC voltage to a conventional induction motor.

Figure 3 is a block diagram showing a current measuring method when applying an alternating voltage in a state in which a conventional induction motor is constrained.

Figure 4 is a block diagram showing a method for measuring current and power when applying an alternating current voltage to an induction motor in a conventional no-load state.

5 is an equivalent circuit diagram of an induction motor in FIGS. 2 to 4.

Figure 6 is a flow chart showing an offline parameter extraction operation of the induction motor of the present invention.

7 is a block diagram showing the structure when the induction motor restraint by applying FIG.

8 is a view showing a change in secondary resistance value with frequency in FIG.

9 is a view showing a change in induction motor load according to the frequency in FIG.

FIG. 10 is a view illustrating a change in mutual inductance value according to frequency by simulation when the leakage inductance value is correct in FIG. 6.

11 is a view showing a change in mutual inductance value according to the frequency according to the experiment when the leakage inductance value is correct in FIG.

FIG. 12 is a view illustrating a change in mutual inductance value according to frequency by simulation when the leakage inductance value is largely set in FIG. 6.

FIG. 13 is a view illustrating a change in mutual inductance value according to frequency according to an experiment when the leakage inductance value is largely set in FIG. 6.

FIG. 14 is a view illustrating a change in mutual inductance value according to frequency by simulation when the leakage inductance value is set to small in FIG. 6.

15 is a view showing a change in mutual inductance value according to frequency according to the experiment when the leakage inductance value is set to small in FIG.

16 is a view showing a change in mutual inductance value according to the leakage inductance and the frequency change by the experiment in FIG.

*** Description of the symbols for the main parts of the drawings ***

100: inverter 110: induction motor

The present invention for achieving the above object is a first step of calculating the stator resistance value of the induction motor after restraining the induction motor; A second step of removing iron losses by calculating first and second iron losses at different frequencies when the calculation of the first step is completed; A third step of calculating a rotor resistance using the iron loss after the iron loss is removed in the second step, and calculating first and second leakage inductances at different frequencies; A fourth step of calculating each of the first and second mutual inductances using the first and second leakage inductances calculated in the third step; A fifth step of determining whether the first and second mutual inductances calculated in the fourth step match and changing the first and second leakage inductance values and repeating the operation of the fourth step if they do not match; If the first and second mutual inductance is the same in the fourth step, characterized in that the sixth step of terminating the mutual inductance and leakage inductance at that time after determining the final value.

Hereinafter, with reference to the accompanying drawings, the operation and effect of an embodiment of the present invention will be described in detail.

6 is a flowchart illustrating an offline parameter extraction operation of the induction motor according to the present invention, which will be described in detail with reference to FIGS. 7 to 16 attached to the operation process according to the present invention.

First, the resistance value Rs of the stator is measured to extract the parameters of the floating motor 110 by using the inverter 100 in the state in which the induction motor 110 is constrained as shown in FIG. 7.

That is, the voltage equation of the induction motor 110 in the synchronous coordinate system is calculated as shown in Equation 7 below.

Here, in order to measure the resistance value (Rs) of the stator, when w = 0, that is, the DC component iqs = 0 and ids is applied to the equation (7), the equation (7) is as follows.

Where Vds = Rs * ids.

In order to eliminate the influence of dead time, currents Id1 and Id2 having two different current values are applied to the induction motor 110 to measure the magnetic flux axis voltages Vd1 and Vd2 at that time. By using this, the resistance value (Rs) of the stator is calculated as shown in Equation 9 below.

In addition, the rotor resistor Rr satisfies Equation 10 when AC current Id and Iq are applied to 0 while the induction motor 110 is restrained.

Here, since the iron loss (Wt) is changed according to the frequency, when the frequency is 20 Hz, the current (Id1) (Id2) is applied to the magnetic flux axis of the induction motor 110 to measure the voltage (Vd1) (Vd2) at that time By using this, the iron loss (Wt) at 20 kHz is calculated, and when the frequency is 40 kHz, the current (Id1) (Id2) is applied to the magnetic flux axis of the induction motor 110 and the voltage Vd1 at that time. (Vd2) is measured and the iron loss (Wt) at 40 kW is calculated using this.

Then, after calculating the iron loss (Wt) of 1 kW by using the following equation (11), the iron loss (Wt) of the equation (10) is removed.

Therefore, when the iron loss (Wt) is removed, the resistance (Rr) of the rotor satisfies the following equation (12).

Here, when the 7.5Kw, 220V induction motor is used, the secondary resistance value Rr of the induction motor 110 rises according to the measurement frequency unless the iron loss Wt is taken into consideration as shown in FIG. However, considering the iron loss (Wt) as shown in Figure 8 (b) has a constant value regardless of the measurement frequency.

In addition, W is large enough in Equation 7 to measure the leakage inductance Lls (Llr) of the stator and the rotor. In this case, the magnetic flux side voltage Vds and the rotational force side voltage Vqs are calculated as in Equation 13 below.

Then, the sum Lls + Llr of the leakage inductance Lls (Llr) from Equation 8 is calculated as in Equation 14 below.

At this time, the leakage inductance Lls (Llr), like the stator resistance (Rs), in order to eliminate the effect of dead time, the current Iq1 (Iq2) having two different current values having a frequency of 40 kHz It is applied to the induction motor 110 to measure the rotational force shaft voltage (Vq1) (Vq2) at that time, by using it to calculate the leakage inductance (Lls) (Llr) as shown in equation (15).

Here, when the leakage inductance (Lls) (Llr) is measured using Equation 14, since the load measurement of the induction motor 110 changes by about 40% as shown in FIG. Calibration is needed.

First, the effect of the leakage inductance (Lls) (Llr) on the mutual inductance (Lm) measurement, the measured value is accurate, the mutual inductance (Lm) measured by the simulation or the actual experiment as shown in Figs. Constant regardless of measurement frequency.

However, when the leakage inductance Lls (Llr) is set large, the mutual inductance Lm varies randomly according to the measurement frequency as shown in FIG. Inductance Lm increases as the measurement frequency increases, as shown in FIG.

However, when the leakage inductance Lls (Llr) is set small, in the case of simulation, the mutual inductance Lm increases below a certain level according to the measurement frequency as shown in FIG. In this case, the mutual inductance Lm decreases as the measurement frequency increases as shown in FIG. 15.

Accordingly, when the leakage inductance Lls is 2.272, 2.499, and 2.726, the mutual inductance Lm according to the frequency change is shown as shown in FIG. 16, and thus the leakage inductance Lls Llr is represented. By correcting, the mutual inductance Lm is calculated.

That is, currents Iq1 and Iq2 having two different current values having two different frequencies 4 kHz and 8 kHz are applied to the induction motor 110, and the respective rotational force shaft voltages Vq1 and Vq2 at that time. ) And the magnetic flux axis voltage (Vd1) (Vd2), and calculates the leakage inductance (Lls) (Llr) by using the equation (14), and then using each of the mutual inductance (Lm) Calculate

First, in order to calculate the mutual inductance Lm, the total impedance Z of the induction motor 110 is calculated as shown in Equation 16 below.

And, using the equation (16), the actual voltage (Ir) and the image (Ij) of the voltage (V) applied to the induction motor 100 and the current (I) flowing at this time is calculated as shown in Equation 17 .

When the voltage V1 applied across the mutual inductance Lm is calculated using Equation 17, the following Equation 18 is used.

Therefore, when Equation 18 is substituted for the voltage V1 applied across the mutual inductance Lm, Equation 19 is established.

In addition, when Equation 19 is arranged into an actual value Ir and an image portion Ij, Equation 19 is obtained.

Then, when the above equation (20) is developed, the following equation (21) holds.

When the quadratic equation of Equation 21 is calculated based on the resistance value Rr of the rotor, the resistance value Rr of the rotor is calculated by Equation 22 below, and the mutual inductance Lm is expressed by Equation 22. Equation 23

Therefore, by using Equation 23, the mutual inductance Lm is calculated at the 4 ㎐ and 8 ,, and the two parameters calculated by changing the last parameter, the leakage inductance L lr (L ls), coincide with each other. The leakage inductance Llr (Lls) and mutual inductance (Lm) of are determined as final parameters.

As described in detail above, the present invention has the effect of preventing performance deterioration by compensating parameters of different induction motors in actual industrial sites by restraining an induction motor in an industrial site and measuring parameters in an inverter.

In addition, by calculating and compensating iron loss and motor slip, vibration, heat generation and rotational force during driving of the induction motor are prevented from being lowered, thereby smoothly driving the induction motor.

Claims (6)

After restraining the induction motor, calculating a stator resistance value of the induction motor; A second step of removing iron losses by calculating first and second iron losses at different frequencies when the calculation of the first step is completed; A third step of calculating a rotor resistance using the iron loss after the iron loss is removed in the second step, and calculating first and second leakage inductances at different frequencies; A fourth step of calculating each of the first and second mutual inductances using the first and second leakage inductances calculated in the third step; A fifth step of determining whether the first and second mutual inductances calculated in the fourth step match and changing the first and second leakage inductance values and repeating the operation of the fourth step if they do not match; And a sixth step of terminating the mutual inductance and the leakage inductance at the time when the first and second mutual inductances coincide with each other in the fourth step. The method of claim 1, wherein the calculating of the stator resistance comprises: a first step of applying respective currents having different current values to the induction motor to measure respective first and second flux shaft voltages; When the first and second magnetic flux axis voltage is measured in the first step, the offline parameter extraction method of the induction motor, characterized in that the second step of calculating the stator resistance value using the following equation (1). (Equation 1) The method of claim 1, wherein the calculating and removing of the iron loss are performed by applying different levels of current to the induction motor at a first frequency to measure respective first and second magnetic flux axis voltages to calculate the first iron loss. Wow; When the operation of the first step is completed, calculating a second iron loss by applying a different level of current to the induction motor at a second frequency to measure third and fourth magnetic flux axis voltages; When the operation of the second step is completed, after calculating the iron loss at 1 ㎐ using Equation 2 below, and the third step of removing the iron loss, characterized in that the offline parameter extraction method of the induction motor. (Equation 2) The method of claim 1, wherein the calculation of the resistance of the rotor is performed by using Equation 3 after removing the iron loss. (Equation 3) The method of claim 1, wherein the first and second leakage inductances are calculated by applying different levels of current to the induction motor at a first frequency, respectively, so that each of the first and second magnetic flux axis voltages and the first and second rotational force shafts is applied. Measuring a voltage; A second step of calculating a first leakage inductance by substituting the first and second magnetic flux and rotational force voltages measured in the first step into Equation 4 below; Applying a current having a different level to the induction motor at a second frequency to measure each of the third and fourth magnetic flux axis voltages and the third and fourth torque force voltages; A fourth step of calculating the second leakage inductance by substituting the third and fourth magnetic flux axis and the rotational force voltage measured in the third step into Equation 4 below, the offline parameter extraction method of the induction motor . (Equation 4) The method of claim 1, wherein the first and second mutual inductances are calculated by substituting a first leakage inductance into Equation 5 below to calculate a first mutual inductance; And a second step of calculating a second mutual inductance by substituting a second leakage inductance into Equation 5 when the calculation of the first step is completed. (Equation 5)