KR20020083613A - Apparatus and method for parameter presumption of induction motor - Google Patents

Abstract

PURPOSE: A parameter estimation apparatus and method for induction motor is provided to achieve improved accuracy by estimating parameter of an induction motor from the result of measurement of multiple frequencies without restricting the induction motor. CONSTITUTION: A parameter estimation apparatus comprises a frequency storing unit(41) for storing frequency commands and outputting frequency in accordance with the on/off operation of a switch; a sine wave generating unit(42) for receiving the frequency and outputting sine waves of a predetermined phase; a voltage regulator unit(43) for receiving current detected by the induction motor, regulating voltage level and outputting voltage; a first multiplication unit(44) for receiving outputs from the sine wave generating unit and the voltage regulator unit and multiplying the received outputs; an inverter unit(45) for converting voltages output from the first multiplication unit into alternate current, and applying the current to the induction motor; a power calculating unit(46) for receiving outputs from the first multiplication unit and the sine wave generating unit, and calculating active and inactive power; a parameter calculation unit(47) for calculating sum of the rotor resistance and leakage inductance from the resistance value of stator and active and inactive power; a parameter estimation unit(48) for storing outputs of the parameter calculation unit, adding outputs and outputting rotor resistance and leakage inductance; and a storing unit for multiplying constant to the rotor resistance value and leakage inductance value and storing rotor and stator leakage inductance.

Description

Parameter estimation apparatus and method for induction motors {APPARATUS AND METHOD FOR PARAMETER PRESUMPTION OF INDUCTION MOTOR}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parameter estimating apparatus and method for an induction motor, and more particularly, to a parameter of an induction motor capable of measuring leakage impedance and rotor resistance of an induction motor without restraining an induction motor driven by an inverter for variable speed driving. An apparatus and method for estimating are provided.

In general, in order to sufficiently control performance in variable speed driving an induction motor to an inverter, it is necessary to properly know the parameters of the induction motor.

1 shows an equivalent circuit of an induction motor, and as shown therein, the resistance Rs and the leakage inductance Lls, which are the primary stator side of the induction motor, are represented by the secondary rotor resistance Rr / S and The equivalent circuit of the leakage inductance (Llr) is shown to convert the secondary side to the primary side or the primary side to the secondary side, where S (S) of the secondary rotor resistance (Rr / S) is Means slip. The slip is usually between 0 and 1 by the following equation.

Where above Is the applied voltage frequency of the induction motor Denotes the rotational frequency. Among these parameters, the rotor resistance (Rr / S) is a parameter that greatly influences the performance of indirect vector control. The rotor is applied with a voltage of three-phase rated frequency and adjusted so that the rated current flows according to the voltage. The mechanical resistance was constrained to measure the rotor resistance. Such a conventional technique will be described with reference to the accompanying drawings.

FIG. 2 is an exemplary view showing the configuration of a parameter estimating apparatus of a conventional induction motor, and as shown therein, a three-phase variable voltage transformer 22 for varying and stepping down the three-phase commercial power supply 21; An ammeter (23) for measuring a current output from the three-phase variable voltage transformer (22); A voltmeter 24 for measuring the voltage between the three phases of the three-phase variable voltage transformer 22; A power meter 25 which receives the measured values of the ammeter 23 and the voltmeter 24 and measures the active power and the reactive power of the induction motor 26; The three-phase commercial power supply 21 is composed of a constraining part 28 which restrains the shaft 27 of the induction motor operating as the output power of the three-phase variable voltage transformer part from moving. Instead, the resistance value between any two terminals is measured while the induction motor 26 is stopped.

Here, dividing the resistance value by two results in the stator resistance value Rs. In addition, the output voltage of the variable voltage transformer 22 in a state in which the three-phase commercial power supply 21 is connected to the three-phase variable voltage transformer 22 and the shaft 27 of the induction motor is constrained by the restrictor 28. Is gradually increased from 0 until the indication of the ammeter 23 becomes the rated current of the induction motor 26 to increase the voltage. At this time, the power meter 25 measures the active power and the reactive power currently being input to the induction motor 26.

On the other hand, when the shaft 28 of the induction motor 26 is restrained by the restraining portion 28 which is a mechanical device, the induction motor 26 does not rotate, so that the mechanical speed becomes zero.

Therefore, the slip S of the induction motor 26 becomes almost '1' by Equation (1), and the rotor resistance Rr / S has a very small value.

At this time, the frequency of the input power is applied to the rated frequency, so the rotor resistance (Rr / S) and the rotor leakage inductance (Llr) is connected to the mutual inductance (Lm) connected in parallel by the following equation It can be seen that the input frequency on the mutual inductance side is high, and the value of the mutual inductance Lm is much larger than the rotor leakage inductance Llr and the rotor resistance Rr / S.

here, Is the induction motor applied voltage frequency Silver mutual inductance, Is the rotor leakage inductance Represents the rotor resistance.

Therefore, when the voltage of the rated frequency is applied in the constrained state of the induction motor 26, it is possible to ignore the mutual inductance Lm, and the mutual inductance (such as the circuit diagram showing the equivalent circuit of the induction motor of FIG. 3). Lm) can be omitted and simplified.

Accordingly, in the indication value of the stator resistance value Rs and the ammeter 23 measured as a simple RL circuit and the active power and reactive power measured by the power meter 25, The sum of the electronic resistance Rr / S, the stator leakage inductance Lls, and the rotor leakage inductance Llr can be obtained.

here, Is the rotor resistance (where S is 1), Is the stator resistance, I is the reading of the ammeter and [W] is the effective power measured at the wattmeter. Silver stator leakage inductance, Silver rotor leakage inductance, Is the induction motor applied voltage frequency, and [Var] represents reactive power measured at the power meter.

However, in the conventional apparatus operating as described above, since the rated current flows by making a parameter measurement in a state in which the restraint is mechanically restrained so that the induction motor does not rotate, the larger the induction motor, the more difficult the restraint becomes.

In addition, the induction motor is obtained through the measurement of the parameter in the state stopped by the restraint part so that the frequency of the current flowing through the rotor during the rating condition and restraint test is changed so that each parameter is changed according to the applied frequency There was a problem that does not get accurate data.

Accordingly, the present invention has been made to solve the above problems, an induction motor that can increase the accuracy by estimating the parameters of the induction motor with measurement results at various frequencies without restraining the induction motor. It is an object of the present invention to provide a parameter estimating apparatus.

1 shows an equivalent circuit of an induction motor.

Figure 2 is an exemplary view showing the configuration of a parameter estimating apparatus of a conventional induction motor.

3 is a circuit diagram showing an equivalent circuit of an induction motor.

4 is a circuit diagram showing a parameter estimating apparatus of the induction motor of the present invention.

5 is a flowchart illustrating a parameter estimation method of the induction motor of the present invention.

** Explanation of symbols for main parts of drawings **

41: frequency storage unit 42: sine wave generator

43: voltage regulator 44: first multiplier

45: inverter unit 46: power calculation unit

47: parameter calculator 48: parameter estimator

SW1 to SW3: first to third selector switches

The present invention for achieving the above object, the frequency storage unit for storing a predetermined frequency command to be applied to the induction motor and outputs each frequency in accordance with the on / off of the switching switch; A sinusoidal wave generator which receives the frequency and always outputs a sinusoidal waveform of a magnitude and phase of a constant voltage; A voltage adjusting unit which receives a current detected by the induction motor and adjusts and outputs a voltage; A first multiplier configured to receive and multiply outputs of the sine wave generator and the voltage adjuster; An inverter unit converting the rectified output voltage of the first multiplier into an alternating current and applying the same to the induction motor; A power calculator configured to receive an output of the first multiplier, a detection current, and a sine wave generator to calculate an effective and reactive power; A parameter calculator which calculates and outputs a sum of the rotor resistance and the leakage inductance at the time of the stator side resistance and the effective and reactive power amount; A parameter estimator for storing an output of the parameter calculator according to a predetermined frequency and adding the outputs to output a rotor resistance and a leakage inductance; And a storage unit for storing the rotor and stator leakage inductance by multiplying the output rotor resistance value and the leakage inductance value by a constant constant.

In order to achieve the above object, the present invention measures a stator resistance before estimating a parameter value, applies a first test frequency of a predetermined frequency as a command frequency, and applies a voltage command to two phases of an induction motor, and zero phase to one phase. A first step of determining whether the detected current of the induction motor is a rated current by applying a voltage command; A second step of performing an active power and a reactive power calculation if the detected current is a rated current in the first step and determining whether one cycle has elapsed since the start of the calculation; A third step of performing rotor resistance and leakage inductance calculation if one cycle has elapsed in the second step, and continuing to perform active power and reactive power calculation if one cycle has not elapsed; If the rotor resistance and the leakage inductance calculation is performed for the predetermined frequency, the final parameter value is estimated. If the rotor resistance and the leakage inductance calculation are not performed for the predetermined frequency, the fourth step is repeated. Characterized in that made.

Hereinafter, with reference to the accompanying drawings an embodiment according to the present invention will be described in detail.

4 is a circuit diagram illustrating a parameter estimating apparatus of an induction motor according to the present invention. As shown in FIG. 4, a frequency storage unit stores predetermined frequency commands to be applied to an induction motor and outputs respective frequencies according to on / off of a changeover switch. (41); A sine wave generator 42 which receives the frequency and always outputs a sinusoidal waveform of a magnitude and phase of a constant voltage; A voltage controller 43 for receiving the current detected by the induction motor IM and adjusting the magnitude of the voltage; A first multiplier 44 for receiving and multiplying outputs of the sine wave generator 42 and the voltage adjuster 43; An inverter unit 45 converting the rectified output voltage of the first multiplier 44 into an alternating current and applying it to the induction motor IM; A power calculator 46 which receives the outputs of the first multiplier 44, the detection current and the sine wave generator 42, and calculates effective and reactive power; A parameter calculator 47 for calculating and outputting the sum of the rotor resistance and the leakage inductance at the time of the stator side resistance and the effective and reactive power amount; A parameter estimator (48) for storing the output of the parameter calculator (47) according to a predetermined frequency and adding the outputs to output the rotor resistance and the leakage inductance; The storage unit 49 stores the rotor and stator leakage inductance by multiplying the output rotor resistance value and the leakage inductance value of the parameter estimator 48 by a constant constant.

5 is a flowchart illustrating a parameter estimating method of an induction motor according to the present invention. As shown in FIG. 5, the stator resistance is measured and the first test frequency of a predetermined frequency is applied as a command frequency before estimating the parameter value (S51). Applying a voltage command to phase 2 and applying a voltage command to phase 1 (S52) to determine whether the detected current of the induction motor is a rated current (S53); A second step (S56) of calculating active power and reactive power when the detected current is the rated current in the first step (S54) and determining whether one cycle has elapsed since the start of the calculation; A third step (S57) of performing a rotor resistance and a leakage inductance calculation when one cycle has elapsed in the second step (S58), and continuing to perform an active power and reactive power calculation if one cycle has not elapsed; If the rotor resistance and the leakage inductance calculation is performed for the predetermined frequency (S59), the final parameter value is estimated (S61), and if the rotor resistance and the leakage inductance calculation are not performed for the predetermined frequency (S59). The fourth step (S60) of repeating the above process is described, and the operation of the present invention configured as described above is as follows.

First, four frequency commands to be applied to the induction motor IM are stored in the frequency storage unit 41, and the first changeover switch SW1 allows the measurement of one frequency to be performed. After the measurement, the sine wave generator 42 is output.

The sine wave generator 42 receives the frequency and generates a sine wave having a frequency of two phases of three phases having a magnitude of 1 and a phase difference of 180 degrees, and generating a waveform having a magnitude of zero.

That is, the sine wave generator 42 applies a single phase voltage, not three phases, to the induction motor IM using the following equation.

Since the sine wave is generated as in Equation (4), no rotating magnetic flux is generated and the induction motor IM does not rotate.

At this time, the voltage adjusting unit 43 receives the current applied to the induction motor IM detected from the current detecting unit 51 and adjusts the magnitude of the voltage command to adjust the magnitude of the output voltage of the inverter unit 45. Accordingly, the first multiplier 44 outputs the three-phase sine wave output from the sine wave generator 42 and the output voltage of the voltage adjuster 43 to the inverter unit 45 after the multiplication operation.

The inverter unit 45 applies a voltage to the induction motor IM in accordance with the magnitude of the output voltage command of the first multiplier 44.

Here, the power calculator 46 detects a current detected by the current applied to the induction motor IM, a voltage command output from the first multiplier 44, and a three-phase sine wave of the sine wave generator 42. In addition, it is input to the power calculation unit 46 and performs the four frequency commands only until the end of each one cycle.

That is, the active power [W] and the reactive power [Var] are calculated using Equation (5) below.

here, Active power T: cycle

: Reactive power Frequency reference

V: magnitude of voltage in the voltage regulator

The effective and reactive power [W] ([Var]) calculated by the above equation (5) is input to the parameter calculator 47.

The parameter calculating unit 47 receives the effective, reactive power [W] ([Var]) and the stator resistance value Rs stored in advance, and the rotor resistance value at that time is expressed by Equation (6) below. The sum of the leakage inductance values is calculated and output to the parameter estimating unit 48.

here, : Rotor resistance Stator Resistance

I: Current detected by the current detector Stator Leakage Inductance

: Rotor Leakage Inductance Active power

: Reactive power Command frequency

Here, the parameter estimator 48 stores the rotor resistance value among the outputs of the weight storage unit 48a in which four weights for each command frequency are stored in advance, and the parameter calculator 47 that varies according to a predetermined frequency. The result of multiplying the output of the second storage unit 48c storing the leakage inductance and the output of the first storage unit 48b and the average weight for each frequency is multiplied by the output of the first storage unit 48b and its parameter calculator. And a second adder 48g which receives and adds the result of multiplying the output of the first adder 48f and the second storage 48c and the average weight for each frequency. .

That is, the sum of the rotor resistance value and the leakage inductance value of the parameter calculator 47 that varies according to the four frequencies is sequentially performed by the second and third changeover switches SW2 and SW3. 2 are stored in the storage units 48b and 48c.

Second and third multipliers 48d, which receive the outputs of the weight storage unit 48a in which four weights for each command frequency are pre-stored, and the outputs of the first and second storage units 48b and 48c. 48e) outputs the inputs to the first and second adders 48f and 48g after the multiplication operation.

Accordingly, the first adder 48f sequentially multiplies the output rotor resistance of the first storage 48b and four weights of the weight storage 48a by the second multiplier 48d. The result is added and the rotor resistance is stored in the resistance estimation value storage section 49a.

That is, the following equation is output to the resistance estimate storage unit 49a.

here : Rotor resistance, where S is 1

: Rotor resistance value stored in the first storage

: Weight value stored in weight storage

The result of the equation (7) is stored in the resistance estimation value storage unit.

Meanwhile, the second adder 48g sequentially multiplies the output leakage inductance value of the second storage unit 48c and the four weights of the weight storage unit 48a by the third multiplier 48e. Add the result and output the leakage inductance value.

At this time, the third multiplier 48e multiplies the constant constant value 0.5 by the leakage inductance and stores the output value in the leakage inductance storage unit 49b as the rotor or stator leakage inductance value.

That is, the leakage inductance storage unit 49b is stored using the following equation.

here, Is the stator leakage inductance value : Leakage inductance value of rotor

: Weight value stored in weight storage

: Leakage inductance value stored in the second storage unit

As described in detail above, the present invention does not mechanically constrain the induction motor, so that two phases have a sine wave having a phase difference of 180 degrees from each other, and the remaining one phase has a rotating magnetic flux in the induction motor by applying a voltage of zero magnitude. It does not occur and the motor does not rotate. Accordingly, it is possible to estimate the parameters more accurately by applying voltages of various frequencies, not just the rated frequency, to estimate them under the rated conditions with measurement results.

Claims (8)

A frequency storage unit for storing predetermined frequency commands to be applied to the induction motor and outputting respective frequencies according to on / off of the changeover switch; A sinusoidal wave generator which receives the frequency and always outputs a sinusoidal waveform of a magnitude and phase of a constant voltage; A voltage adjusting unit which receives a current detected by the induction motor and adjusts and outputs a voltage; A first multiplier configured to receive and multiply outputs of the sine wave generator and the voltage adjuster; An inverter unit converting the rectified output voltage of the first multiplier into an alternating current and applying the same to the induction motor; A power calculator configured to receive an output of the first multiplier, a detection current, and a sine wave generator to calculate an effective and reactive power; A parameter calculator which calculates and outputs a sum of the rotor resistance and the leakage inductance at the time of the stator side resistance and the effective and reactive power amount; A parameter estimator for storing an output of the parameter calculator according to a predetermined frequency and adding the outputs to output a rotor resistance and a leakage inductance; And a storage unit for storing the rotor and stator leakage inductance by multiplying the output rotor resistance value and the leakage inductance value by a constant constant of the parameter estimator. 2. The apparatus of claim 1, wherein the parameter estimator comprises: a weight storage unit in which four weights for each command frequency are stored in advance; A first storage unit which stores a rotor resistance value of an output of the parameter calculator that changes according to a predetermined frequency; A second storage unit for storing leakage inductance of the output of the parameter calculator; A first adder configured to receive the multiplication result of the output of the first storage and the average weight of each frequency; And a second adder configured to receive and add the output of the second storage unit and the result of multiplying the average weights of the respective frequencies. 2. The apparatus of claim 1, wherein the storage unit comprises a resistance estimation value storage unit and a leakage inductance value storage unit. Before estimating the parameter value, measure the stator resistance, apply the first test frequency of the predetermined frequency as the command frequency, apply the voltage command to the two phases of the induction motor, and apply the zero voltage command to the first phase, so that the detection current of the induction motor is rated. Determining whether the current is current; A second step of performing an active power and a reactive power calculation if the detected current is a rated current in the first step and determining whether one cycle has elapsed since the start of the calculation; A third step of performing rotor resistance and leakage inductance calculation if one cycle has elapsed in the second step, and continuing to perform active power and reactive power calculation if one cycle has not elapsed; If the rotor resistance and the leakage inductance calculation is performed for the predetermined frequency, the final parameter value is estimated. If the rotor resistance and the leakage inductance calculation are not performed for the predetermined frequency, the fourth step is repeated. Parameter estimation method of the induction motor, characterized in that made. 5. The method of claim 4, wherein the second step calculates active power and reactive power by the following equation. (Equation 5) here, Active power T: cycle : Reactive power Frequency reference V: magnitude of voltage in the voltage regulator 5. The method of claim 4, wherein the predetermined frequency is estimated at four test frequencies at rated conditions. 5. The method of claim 4, wherein the third step obtains a rotor resistance value and a leakage inductance value according to four test frequencies by using the following equations for the active power and the reactive power: . (Equation 6) here, : Rotor resistance Stator Resistance I: Current detected by the current detector Stator Leakage Inductance : Rotor Leakage Inductance Active power : Reactive power Command frequency The method of estimating a parameter of an induction motor according to claim 4, wherein the voltage commanded to the two phases is a sine wave having a phase difference of 180 degrees.