Induction Motor Drive

Abstract

To precisely identify an electric constant of an induction motor in a state in which a rotor is stopped.SOLUTION: An induction motor drive device includes a motor constant identification unit for identifying an electric constant of an induction motor based on a detection value or a voltage command value of interphase voltage and a current command value or a current detection value. The electric constant identified by the motor constant identification unit includes identification values of primary resistance, leakage inductance, no-load current and a secondary time constant. A current command value generation unit generates the current command value in magnitude which is previously set in a state in which a rotor of the induction motor is stopped, and the motor constant identification unit identifies the no-load current and the secondary constant based on the detection value of interphase voltage after previously-set time elapses and output of a power converter is interrupted.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to an induction motor drive. [Background technology]

[0002] Variable speed motor drives that use inverters to drive electric motors at variable speeds are used in various fields. Among electric motors, induction motors are often superior in terms of maintainability and robustness, and also have the advantage of being able to run on commercial power sources for backup purposes. For this reason, induction motors are still used in many applications today. In electric motor drives, high-performance operation can be achieved by detecting the rotation speed and implementing control that accurately grasps the slip, but sensorless vector control has been put into practical use as a method of high-performance driving without using a rotation sensor.

[0003] In sensorless vector control, the output voltage and current values ​​are used to obtain electrical information about the motor, such as slippage, during operation, but the calculations required to do so require accurate knowledge of the motor's electrical constants. General-purpose inverters, which do not specify the induction motor used, have an auto-tuning function that automatically measures the electrical constants of the induction motor, that is, an identification function, so that highly accurate sensorless vector control can be performed even when various induction motors are used.

[0004] The electrical constants required for sensorless vector control are expressed differently depending on the state variables. For example, in the model of the induction motor described in Non-Patent Document 1, when expressed on the synchronous DQ axes rotating at the primary angular frequency, they are expressed as in the following equation (1) with the primary voltage of the motor on the left side. However, each variable is expressed as follows. That is, the primary voltage D-axis component is v sd The primary voltage Q-axis component is v sq The D-axis component of the primary current is i sd The primary current Q-axis component is i sq The D-axis component of the secondary magnetic flux is φrd The secondary magnetic flux Q-axis component is φ rq The electrical constants are expressed as follows: The primary resistance is R s and the secondary resistance is R r The mutual inductance is M and the primary inductance is L s and the secondary inductance is L r Let the leakage coefficient be σ and the primary angular frequency be ω s and the rotor angular frequency is ω re The slip angular frequency is ω slip Let us assume that.

[0005]

number

[0006] However, if this equation is used as is, the primary current and secondary current are state variables, and the concept of magnetic flux contributing to torque is difficult to intuitively understand. Therefore, a differential equation with the primary current and secondary magnetic flux as state variables is shown below as equation (2). r =L s It should be noted that an approximation is made:

[0007]

number

[0008] When the differential term is placed on the left side of the equation, it becomes the following equation (3).

[0009]

number

[0010] In order to calculate the voltage command value required in the steady state, the differential term is set to 0, resulting in the following equation (4).

[0011]

number

[0012] If the left side is the primary voltage and each component is rewritten, we get the following equations (5) and (6).

[0013]

number

[0014] Here, if we define it as in the following equation (7), it can be expressed as the following equation (8).

[0015]

number

[0016] The state variables are the leakage flux and the secondary flux φ rd Then, the leakage flux D-axis component F sd and leakage flux Q-axis component F sq In the steady state, the D-axis component of the secondary magnetic flux φ rd and the secondary magnetic flux are steadily expressed by the following equations (11) and (12), respectively. Taking these into consideration, equations (5) and (6) become the following equations (13) and (14), respectively.

[0017]

number

[0018] From this, the electrical constant is "R s ", σL s ", "1 / T r (=R r / L r )" and "L s It can be seen that if the four electrical constants shown in the above are clarified, it is possible to express the induction motor mathematically. Therefore, in this specification, the primary resistance R s , leakage inductance L f (L f = σLs ), quadratic time constant T r and the primary inductance L s The induction motor model is expressed using the following four constants.

[0019] Specific means for acquiring the electrical constants of an induction motor are described in, for example, JIS C 4210 "General-purpose low-voltage three-phase squirrel-cage induction motor" and JEC-2110 "Induction motor" based on a steady-state equivalent circuit. Hereinafter, such specific means for acquiring the electrical constants of a conventional induction motor will be referred to as the conventional means. When the content of the conventional means is applied to the motor model shown in equation (3), it can be roughly interpreted as follows. In the motor model shown in equation (3), the iron loss resistance is omitted. Identification of the iron loss resistance will not be dealt with in this specification either.

[0020] In the conventional method, a method of applying DC is described for identifying the primary resistance. After DC is applied and a steady state is reached, no electromotive force is generated on the secondary side, i.e., the rotor, so it can be considered as a circuit consisting of only the resistance on the primary side. Since no approximation elements are included, no error due to approximation occurs in this equivalent circuit. Figure 13 shows an equivalent circuit for one phase of an induction motor, and Figure 14 shows an equivalent circuit for one phase of an induction motor when DC is applied.

[0021] From such an equivalent circuit, the following equation (15) is obtained. Note that all state variables are written as values ​​for one phase.

[0022]

number

[0023] Since the expression on the synchronous coordinate axes is when the motor is stopped, if the flowing current is expressed as the D-axis only, it becomes the following equation (16). For simplicity, in this explanation and similar explanations below, each state quantity is expressed as a state quantity when it is subjected to relative transformation. Therefore, the primary resistance value is expressed as the resistance value for one phase.

[0024]

number

[0025] Since voltage is applied to the motor by the power conversion device, unless appropriate corrections are made to voltage values ​​such as the dead time provided to prevent a short circuit between the upper arm and lower arm, the on-resistance which is the voltage drop in semiconductor devices such as IGBTs, and the collector-emitter saturation voltage, an error will occur between the voltage command value and the actual output voltage, making it impossible to accurately identify the primary resistance value of the motor.

[0026] Conventionally, there have been proposed techniques for correcting values ​​equivalent to these error voltages, such as a method of detecting the output voltage and feeding back the error voltage so that it coincides with the voltage command value, and a technique of obtaining the error voltage from the characteristics of the device measured in advance and compensating in a feedforward manner without providing a configuration for voltage detection. The former is considered to be able to perform accurate correction if there is no voltage detection error.

[0027] However, in the latter case, since there are individual differences in device characteristics, there may be individual differences between phases even when the same device is used, and considering that the on-resistance, collector-emitter saturation voltage, etc. also change with temperature, there is a possibility that the identified value of the primary resistance will have some identification error. In other words, in the case of a power conversion device that does not have a configuration for voltage detection such as a voltage detection circuit, it is considered unavoidable that the identified value of the primary resistance will have some identification error.

[0028] The conventional method includes a description of no-load test and a locked-rotation test. In a no-load test, the motor is rotated by applying a rated voltage at a rated frequency under no-load conditions, and the current flowing at that time is measured. When there is no load, the rotor speed is the synchronous speed, so if we consider the slip to be zero, the term obtained by dividing the secondary resistance by the slip "s" becomes "∞", which leads to the conclusion that current flows only in the excitation circuit. This expansion also does not include any approximation elements, so no errors due to approximation occur. Figure 15 shows the equivalent circuit for one phase of an induction motor during a no-load test.

[0029] The condition for this no-load operating point is that the motor has a rated angular frequency ω sn At rated voltage V sn The no-load current that flows when the rated magnetic flux current i sn If we define it as follows, it can be expressed as the following equations (17) and (18). However, the rated voltage v sn is the phase voltage effective value, and the rated magnetic flux current i sn is the effective value of the phase current. In addition, in the following equations (17) and (18), the input voltage is considered to be the rated voltage, and the torque current is considered to be equal to zero.

[0030]

number

[0031] In this case, since it is expressed in relative conversion, the rated magnetic flux current i on the DQ synchronous axis sdn value and rated magnetic flux current i sn There is a relationship between them expressed by the following equation (19).

[0032]

number

[0033] Taking these factors into consideration, the following equations (20) and (21) are obtained.

[0034]

number

[0035] The sum of the squares of each component of the primary voltage expressed by the above equations (20) and (21) is the rated voltage v sn Since the no-load current value is equal to the square of the magnitude of the primary inductance L s can be obtained by the following equation (22).

[0036]

number

[0037] However, in cases where only the drive unit is replaced while the motor remains connected in an existing device, it is often difficult to mechanically separate the motor from the device at the destination, making it difficult to rotate the motor and measure the no-load current. In such cases, it is desirable to obtain the no-load current or primary inductance without rotating the motor.

[0038] In a lock test, the rotor is mechanically locked, so it does not rotate. If it is difficult to actually lock the rotor, a test equivalent to a lock test can be performed by applying a single-phase voltage. In a lock test, the rotor does not rotate, so "slip = 1", but if 1 is substituted for slip s in the equivalent circuit, it becomes as follows. That is, Figures 16 and 17 show the equivalent circuit for one phase of an induction motor during a lock test.

[0039] The equivalent circuit shown in Figure 16 has the same number of components as the equivalent circuit shown in Figure 13, and has not changed. Since the current flowing through the excitation inductance is not zero, even if the primary resistance is considered to be known, the secondary side constant, that is, the secondary inductance L r and secondary resistance R rIt is difficult to separate the terms including . Therefore, by approximately considering the constrained state as "slip s = 1," in other words, when the slip is at its maximum, and current mainly flows in the secondary circuit, the equivalent circuit shown in Figure 17 can be obtained. The relationship between the various constants from this equivalent circuit is given by the following equation (23).

[0040]

number

[0041] By observing the applied primary voltage and the current flowing, the sum of the primary and secondary resistances and the leakage inductance can be obtained. Note that the secondary resistance and leakage inductance are both primary-side converted values. In this case, the sum of the primary and secondary resistances, "R s +R req " to the primary resistance R s Subtract the secondary resistance R req To find the primary resistance R s The accuracy of the secondary resistance identification value R req As mentioned above, when considering individual differences in the characteristics of semiconductor devices and temperature changes, it is necessary to keep the primary resistance identification value R s The accuracy of the secondary resistance R req or the secondary time constant L r / R r A method that can identify the above with high accuracy is desirable.

[0042] Patent Document 1 discloses a technique for driving an induction motor in an unloaded state, observing the time change of the induced voltage by utilizing the induced voltage actually generated by the secondary magnetic flux, and identifying the secondary time constant. However, as mentioned above, it may be difficult to mechanically separate the motor from the equipment at the destination, and therefore it may be difficult to drive the motor in an unloaded or light-loaded state. Therefore, the method described in Patent Document 1 may be difficult to apply.

[0043] Furthermore, Patent Document 2 discloses a conventional technique that does not rotate the motor. The method described in Patent Document 2 is equivalent to carrying out a test similar to a lock test by applying a single-phase AC current to a drive device. Therefore, in the method described in Patent Document 2, the sum of the primary resistance and secondary resistance "R s +R req " to the primary resistance R s Subtract the secondary resistance R req However, as mentioned above, when considering individual differences in the characteristics of semiconductor devices and temperature changes, the primary resistance R s Since there is a limit to the accuracy of identifying the secondary resistance R req It is unavoidable that this will affect the identification accuracy of the secondary constants. For this reason, there is a limit to how much the identification accuracy of the secondary constants can be improved in a test equivalent to a restraint test. [Prior art documents] [Non-patent literature]

[0044] [Non-Patent Document 1] "Theory and Design Practice of AC Servo Systems - From Fundamentals to Software Servo" 1990 Hidehiko Sugimoto (ed.), Masato Koyama / Shinzo Tamai (authors) [Patent Document 1] Patent No. 6591794 [Patent Document 2] Patent No. 6194718 Summary of the Invention [Problem to be solved by the invention]

[0045] Therefore, the present invention provides an induction motor driving device that can accurately identify the electrical constants of an induction motor with the rotor stopped. [Means for solving the problem]

[0046] An induction motor driving device of an embodiment includes a power converter that converts a DC voltage into a three-phase AC voltage with variable voltage and variable frequency and supplies the voltage to an induction motor, a phase-to-phase voltage detection unit that detects phase-to-phase voltages of the induction motor between two or more phases, a current detection unit that detects a current of the induction motor, a current adjustment unit that calculates a voltage adjustment value so that a current detection value, which is a value obtained by converting the detected current value onto the same control axis as a current command value, matches the current command value, a current command value generation unit that generates the current command value and provides it to the current adjustment unit, a voltage command generation unit that generates a voltage command value using the voltage adjustment value obtained from the current adjustment unit, and a motor constant identification unit that identifies an electrical constant of the induction motor based on the detected phase-to-phase voltage value or the voltage command value, and the current command value or the current detection value.

[0047] In the above configuration, the electrical constants identified by the motor constant identification unit include identified values ​​of a primary resistance, a leakage inductance, a no-load current and a secondary time constant, and the current command value generation unit generates the current command value of a preset magnitude when the rotor of the induction motor is stopped, and after a preset time has elapsed and the output of the power converter is cut off, the motor constant identification unit identifies the no-load current and the secondary time constant based on the detection value of the phase-to-phase voltage.

[0048] Moreover, an induction motor driving device of an embodiment includes a power converter that converts a DC voltage into a variable-voltage, variable-frequency three-phase AC voltage and supplies the voltage to an induction motor, a current detection unit that detects a current of the induction motor, a current adjustment unit that calculates a voltage adjustment value so that the current detection value, which is a value obtained by converting the detection value of the current onto the same control axis as the current command value, matches the current command value, a current command value generation unit that generates the current command value and provides it to the current adjustment unit, a voltage command generation unit that generates a voltage command value using the voltage adjustment value obtained from the current adjustment unit, and a motor constant identification unit that identifies an electrical constant of the induction motor based on the voltage command value, the current command value, or the current detection value.

[0049] In the above configuration, the electrical constants identified by the motor constant identification unit include identified values ​​of a primary resistance, a leakage inductance, a no-load current and a secondary time constant, the current command value generation unit generates the current command values ​​of two different preset magnitudes in a state in which the rotor of the induction motor is stopped, and the motor constant identification unit identifies the no-load current and the secondary time constant based on the voltage command value after the current command value generation unit changes the current command value from a high level to a low level. [Brief description of the drawings]

[0050] [Figure 1] FIG. 1 is a schematic diagram illustrating an induction motor driving device according to a first configuration example of an embodiment; [Diagram 2] FIG. 1 is a timing chart for explaining magnetic flux calculation in a first configuration example according to an embodiment; [Diagram 3] 1 is a timing chart showing waveforms of each part when identifying a no-load current and a secondary time constant in a first configuration example according to one embodiment; [Figure 4] FIG. 1 is a schematic diagram illustrating an induction motor driving device according to a second configuration example of an embodiment; [Diagram 5] FIG. 11 is a timing chart for explaining magnetic flux calculation in a second configuration example according to an embodiment; [Figure 6] FIG. 11 is a timing chart for explaining a magnetic flux compensation method when identifying a no-load current and a secondary time constant according to a second configuration example of one embodiment; [Figure 7] FIG. 1 is a functional block diagram showing a current control system according to an embodiment. [Figure 8] FIG. 10 is a timing chart for explaining optimization of identification of a primary resistance and leakage inductance and identification of a no-load current and a secondary time constant according to a second configuration example of an embodiment; [Figure 9] FIG. 13 is a diagram showing the relationship between the target magnetic flux and the no-load current identification value when the target magnetic flux is set to a magnetic flux amount that is 0.75 to 1.5 times the rated magnetic flux according to an embodiment. [Figure 10]FIG. 1 is a timing chart for explaining an example of identification of a no-load current taking into account magnetic saturation according to an embodiment, showing a period of a target magnetic flux 1; [Figure 11] FIG. 1 is a timing chart for explaining an example of identification of a no-load current taking into account magnetic saturation according to an embodiment, showing a period of a magnetic flux command 2; [Figure 12] FIG. 1 is a timing chart for explaining an example of identification of a no-load current taking into account magnetic saturation according to an embodiment, showing a period of a flux command 3; [Figure 13] FIG. 1 is a diagram showing an equivalent circuit for one phase of an induction motor according to the prior art. [Figure 14] FIG. 1 is a diagram showing an equivalent circuit of one phase of an induction motor when DC is applied according to the prior art. [Figure 15] FIG. 1 is a diagram showing an equivalent circuit for one phase of an induction motor during a no-load test according to the prior art. [Figure 16] FIG. 1 shows an equivalent circuit for one phase of an induction motor during a lock test according to the prior art. [Figure 17] FIG. 2 shows an equivalent circuit for one phase of an induction motor during a lock test according to the prior art [Figure 18] FIG. 13 is a diagram showing a voltage command value and a current value when identifying a primary resistance and a leakage inductance according to the prior art; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Hereinafter, an embodiment of an induction motor drive device will be described with reference to the drawings. In this specification, i sdref is the D-axis current command, i sqref is the Q-axis current command, i sdmeas is the D-axis current detection value, i sqmeas is the Q-axis current detection value, v sdref is the D-axis voltage command value, v sqref is the Q-axis voltage command value, v sdadj is the D-axis voltage adjustment value, v sqadj is the Q-axis voltage adjustment value, v sdmeas is the D-axis voltage detection value, v sqmeas is the Q-axis voltage detection value, θ re_cis the output voltage phase, K d is the voltage command coefficient for leakage inductance identification, R s_calc is the primary resistance identification value, L f_calc is the leakage inductance identification value, i sdn_calc is the no-load current identification value, T r_calc represents the secondary time constant identification value.

[0052] <Regarding the induction motor drive device of the first configuration example> The induction motor driving device 1 of the first configuration example shown in Fig. 1 has a configuration including a phase-to-phase voltage detection unit which is a voltage detector. The induction motor driving device 1 is a variable speed motor driving device which drives an induction motor 2 at a variable speed. Each phase terminal of a three-phase AC power source 3 is connected to an AC input terminal of a full-wave rectifier circuit 4 which is made up of a diode bridge. A smoothing capacitor 5 and a power converter 6 are connected between the DC output terminals of the full-wave rectifier circuit 4. The power converter 6 which is an inverter converts a DC voltage into a three-phase AC voltage of variable voltage and variable frequency and supplies it to the induction motor 2, and each phase output terminal of the power converter 6 is connected to each phase winding terminal of the induction motor 2.

[0053] The control device 7 controls the power converter 6 to convert the DC voltage into a three-phase AC voltage with variable voltage and variable frequency. Current detectors 8U and 8W for detecting the current of the induction motor 2 are disposed at the U-phase and W-phase output terminals of the power converter 6. The U-phase and W-phase currents i u , i w are input to a UVW / dq converter 9. The UVW / dq converter 9 converts the three-phase currents into dq-axis currents in vector control and inputs them to a current adjusting unit 10.

[0054] The UVW / dq converter 9 converts the detected current value onto the same control axis as the current command value. That is, the UVW / dq converter 9 converts the detected current value into an output voltage phase θ re_c is converted to a preset arbitrary fixed value on the synchronous coordinate axis. The D-axis current detection value i sdmeas and the Q-axis current detection value i sqmeasis input to the current adjustment unit 10. The D-axis current detection value i sdmeas is also input to the motor constant identification unit 11.

[0055] Each phase output terminal of the power converter 6 is connected to an input terminal of the phase-to-phase voltage detector 12. The phase-to-phase voltage detector 12 detects two or more phase-to-phase voltages of the induction motor 2. In this case, the phase-to-phase voltage detector 12 detects the UV phase-to-phase voltage v uv and WV phase-to-phase voltage v wv The inter-phase voltages detected by the inter-phase voltage detection unit 12 are input to a UV,WV / UVW converter 13.

[0056] The UV,WV / UVW converter 13 converts the UV interphase voltage v uv and WV phase-to-phase voltage v wv is the three-phase voltage, that is, the U-phase voltage v u , V phase voltage v v and W phase voltage v w The UVW / dq converter 14 converts the three-phase voltages corresponding to the detected values ​​of the inter-phase voltages onto the same control axis as the current command value. That is, the UVW / dq converter 14 converts the three-phase voltages corresponding to the detected values ​​of the inter-phase voltages onto an output voltage phase θ re_c is converted onto the synchronous coordinate system as a preset arbitrary fixed value.

[0057] The D-axis voltage detection value v, which is a value converted by the UVW / dq converter 14 sdmeas and Q-axis voltage detection value v sqmeas Among them, the D-axis voltage detection value v sdmeas is input to the motor constant identification unit 11. The current command value generation unit 15 generates a D-axis current command i sdref and Q-axis current command i sqref The D-axis current command i generated by the current command value generating unit 15 is provided to the current adjusting unit 10. sdref and Q-axis current command i sqref Among them, the D-axis current command i sdref is also input to the motor constant identification unit 11.

[0058] The current adjustment unit 10 includes a proportional-integral compensator that performs PI control. The current adjustment unit 10 converts the detected current value onto the same control axis as the current command value, that is, the D-axis current detection value i sdmeas and the Q-axis current detection value i sqmeas is the current command value, D-axis current command i sdref and Q-axis current command i sqref The voltage adjustment value calculated by the current adjustment unit 10 is calculated so as to match the D-axis voltage adjustment value v sdadj and Q-axis voltage adjustment value v sqadj is input to the voltage command generating unit 16.

[0059] The voltage command generating unit 16 generates a D-axis voltage adjustment value v sdadj and Q-axis voltage adjustment value v sqadj and the leakage inductance identification voltage command coefficient K d The voltage command value v generated by the voltage command generating unit 16 is sdref and the Q-axis voltage command value v sqref is input to the dq / UVW converter 17. The D-axis voltage command value v sdref is also input to the motor constant identification unit 11. The dq / UVW converter 17 converts the input D-axis voltage command value v sdref and the Q-axis voltage command value v sqref into a three-phase voltage command, and generates a PWM signal to output to the power converter 6. Note that PWM is an abbreviation for Pulse Width Modulation.

[0060] The motor constant identification unit 11 detects the D-axis voltage v corresponding to the detected value of the phase-to-phase voltage. sdmeas or D-axis voltage command value v sdref and the D-axis current command i sdref or D-axis current detection value i sdmeas The electric constants of the induction motor 2 are identified based on the above. The electric constants identified by the motor constant identification unit 11 include the identified values ​​of the primary resistance, the leakage inductance, the no-load current, and the secondary time constant, that is, the primary resistance identified value R s_calc , leakage inductance identification value L f_calc, no-load current identification value i sdn_calc , second-order time constant identified value T r_calc Includes:

[0061] Although details will be described later, in the above configuration, the electrical constants are identified as follows. That is, the current command value generating unit 15 generates a current command value of a preset magnitude when the rotor of the induction motor 2 is stopped. Then, after a preset time has elapsed and the output of the power converter 6 is cut off, the motor constant identifying unit 11 identifies the no-load current and the secondary time constant based on the detected values ​​of the phase-to-phase voltages.

[0062] Next, the principle of identification of each electrical constant implemented in the induction motor driving device 1 of the first configuration example will be described based on equation (3) which is the motor model used in this embodiment. <Identification of primary resistance> Identification of the primary resistance is basically the same as the method of applying direct current described in standards, and is performed in induction motor driving device 1 having power converter 6. When the third line of equation (3) is written, it becomes equation (24) below.

[0063]

number

[0064] According to equation (24), the secondary magnetic flux D-axis component φ rd The behavior of "Mi sd ", the dynamics change with a quadratic time constant. The left side of the first line of equation (3) is the primary voltage v sd If we set it so that:

[0065]

number

[0066] Here, assuming that there are two conditions: "the rotor is stopped and no frequency component is applied as the output voltage" and "current is applied only to the D-axis side", then "ω s =0", "i sq =0" and "φ rq = 0". Therefore, the above formula (25) becomes the following formula (26). Note that in this explanation and similar explanations below, the direction of the D axis is a position θ where none of the current values ​​of the U phase, V phase, and W phase are close to 0. re_c Let us assume that.

[0067]

number

[0068] In the above formula (26), "i sd " is the current value of the induction motor 2. Here, it is assumed that the current is applied for a sufficient time T0 so that it can be treated as a steady state. Then, when the steady state is reached, "φ rd =Mi sd Taking this into consideration, the above equation (26) becomes the following equation (27).

[0069]

number

[0070] In this case, the applied voltage is the voltage command v sdref The current can be understood as the current detection value i sdmeas or current command value i sdref Therefore, the primary resistance identification value R s_calc can be calculated as shown in the following equation (28).

[0071]

number

[0072] If there are errors in the dead time correction, the on-resistance correction of the semiconductor element, the collector-emitter saturation voltage correction, etc. in the power converter 6 composed of semiconductor elements such as IGBTs, the above-mentioned one operating point "v sdref ,i sdref In the calculation of only ", the influence of all the above errors is not reflected in the primary resistance identification value R s_calc Therefore, in order to reduce the influence of the error in the dead time compensation and the error in the collector-emitter saturation voltage compensation, which do not change much depending on the magnitude of the current, the difference between the voltage command value and the current command value of the two operating points, "v sdref1 -v sdref2 ,i sdref1 -i sdref2 " Primary resistance identification value R s_calc may be calculated.

[0073]

number

[0074] In addition, the primary resistance identification value R s_calc Even if the above calculation is performed, an error in the voltage drop correction due to the on-resistance of the semiconductor element, which is a component proportional to the current value, remains as a primary resistance identification error. The voltage command value and the current value during identification of the primary resistance performed as described above are as shown in the primary resistance identification phase in FIG.

[0075] <Identification of leakage inductance> The leakage inductance value is identified by applying a single-phase AC current after the above-mentioned identification of the primary resistance value is completed. The leakage inductance is identified in the same manner as the restraint test described in the standards. In this case, the primary voltage D-axis component v sd and the primary current D-axis component i sd are expressed by the following equations (30) and (31), respectively. However, they are treated as equivalent circuits that do not take into account iron loss resistance. The current isd When the current is in a steady state, sd0 Then, the voltage command value is v sdref0 (=R s i sd0 ) and from the initial state, the voltage command is changed to a frequency component, Δv sd The change in current when sd Let us assume that.

[0076]

number

[0077] In identifying the primary resistance, the secondary magnetic flux φ rd is sufficiently stable at the steady value Mi sd The secondary time constant is sufficiently slow compared to the change in current due to the applied AC voltage. Therefore, during the identification of the leakage inductance, the secondary magnetic flux is almost constant Mi sd0 If we consider that the voltage change Δv sd and the current change Δi sd The relational expression can be expressed as the following equation (32).

[0078]

number

[0079] If the above formula (32) is written as a relational expression for only the change portion, it becomes the following formula (33).

[0080]

number

[0081] Here, the leakage inductance L f is expressed as the following equation (34), and the secondary resistance R req is expressed as the following equation (35), and the sum of the primary and secondary resistances R totalIf this is expressed as equation (36) below, the relational expression for only the change amount becomes equation (37) below. Note that the secondary resistance in this case is a primary converted value.

[0082]

number

[0083] The above formula (37) coincides with the equivalent circuit during the restraint test shown in Fig. 16. In other words, it can be said that the equivalent circuit used in the restraint test is equivalent to a state in which the above approximation is taken into account in the differential equation in formula (3).

[0084] Voltage change Δv to generate AC current sd The voltage value v at the time of identifying the primary resistance sdref0 (=R s i sd0 ) with a coefficient K less than 1 d A sine wave with amplitude equal to the voltage multiplied by the coefficient K is applied. d can be set to, for example, 0.25. In this case, the voltage change Δv sd is expressed by the following equation (38): where ω is the frequency of each of the sine waves.

[0085]

number

[0086] In this way, the relational expression for only the change amount can be expressed as the following equation (39).

[0087]

number

[0088] When both sides of the above formula (39) are Laplace transformed, we obtain the following formula (40). Then, when formula (40) is rearranged, we obtain the following formula (41).

[0089]

number

[0090] Assuming that the right-hand side of the above equation (41) is decomposed as in the following equation (42), and combining the two terms in the parentheses on the right-hand side, we obtain the following equation (43).

[0091]

number

[0092] When the numerator of the above formula (43) is rearranged with respect to the Laplace operator s, the following formula (44) is obtained.

[0093]

number

[0094] Assuming that equations (41) and (44) are identities with respect to the Laplace operator s, and comparing the coefficients on the right-hand sides, we obtain the following three equations, (45), (46), and (47).

[0095]

number

[0096] A to C are found based on the above three equations. First, the following equation (48) is obtained from equations (45) and (46). Then, substituting equation (48) into equation (47) gives the following equation (49). By rearranging equation (49), A can be found as in the following equation (50).

[0097]

number

[0098] Since A is obtained in this manner, B and C can be derived as shown in the following equations (51) and (52).

[0099]

number

[0100] As described above, A to C are found, but for simplicity, we will keep them written as A to C. If we rewrite equation (41), which is the Laplace transform of equation (39), which is the relation between voltage and current, using A to C, we get the following equations (53) and (54).

[0101]

number

[0102] When the above formula (54) is subjected to an inverse Laplace transform, the following formula (55) is obtained. Then, when A to C are substituted into the formula (55), the following formula (56) is obtained.

[0103]

number

[0104] The first term in the brackets in equation (56) above is a term that decays over time, so the time constant (L f / R total ) can be ignored. Taking this into consideration, the above formula (56) can be simplified as the following formula (57).

[0105]

number

[0106] Here, the above current value equation is changed to the following equation (58): s and the coefficient H c In this case, the coefficient H s and the coefficient H c According to these definitions, the amplitude K d vsd0 , if the angular frequency ω is constant, the coefficient H s and the coefficient H c is also found to be a constant value.

[0107]

number

[0108] Leakage inductance L f (=σL s ) and the sum of the primary and secondary resistances R total From the above definitions, and can be expressed as the following equations (62) and (63), respectively.

[0109]

number

[0110] Coefficient H s and the coefficient H c are the coefficients applied to the sine function and the cosine function of the current value equation shown in equation (58), respectively. s and the coefficient H c is calculated by integrating the value obtained by multiplying the current value flowing during N cycles of the applied AC voltage by a Cos function or a Sin function as shown in the following equations (64) and (65). Tst is the time when the integration starts. The integration time is determined by the time constant (L f / R total ) is set to a time that is sufficiently longer than the time T. Here, T = (2π / ω) [s].

[0111]

number

[0112]

number

[0113] From this, the coefficient H sand the coefficient H c can be calculated using the following equations (66) and (67).

[0114]

number

[0115] The coefficient H obtained in this way s and the coefficient H c By substituting into equations (62) and (63), the leakage inductance identification value L is obtained as shown in the following equations (68) and (69). f_calc and the sum of the primary and secondary resistances R total_calc Here, the leakage inductance identification value L f_calc Only the above will be adopted.

[0116]

number

[0117] The voltage command value and the current value when the leakage inductance is identified as described above are as shown in the leakage inductance identification phase in FIG.

[0118] <Identification of secondary time constant and no-load current> In the induction motor driving device 1 of the first configuration example, the output is shut off, that is, gated and blocked, after current is applied, and the magnetic flux is calculated using the voltage detection value. That is, as shown in Fig. 2, when DC is applied to the induction motor 2, and the voltage command value becomes a constant value, the gate is blocked so that the output voltage becomes 0, and then, due to the change in the attenuating secondary magnetic flux, a voltage is generated at the motor terminals.

[0119] The voltage value appearing at the motor terminals is found, and the amount of magnetic flux that results from its integral value is calculated. This modeling is performed as follows. First, the following equation (70) is obtained from the first line of equation (3).

[0120]

number

[0121] After the gate is blocked, the current value converges to 0 in a time that is sufficiently shorter than the secondary time constant. Therefore, if the primary frequency is set to 0, the rotor is not moving, and the Q-axis magnetic flux is set to 0, the following equation (71) is obtained.

[0122]

number

[0123] On the other hand, when the third line of equation (3) is written, it becomes equation (72) below.

[0124]

number

[0125] Similarly, after the gate is blocked, the current value converges to 0 in a time sufficiently shorter than the second-order time constant, so equation (72) can be expressed as equation (73) below.

[0126]

number

[0127] This differential equation is expressed as follows: The initial value of the secondary magnetic flux is φ rd0 (=Mi sd0 ) and performing a Laplace transform, we obtain the following equations (74) and (75).

[0128]

number

[0129] The secondary magnetic flux can be expressed as a function of time as shown in equation (76) below.

[0130]

number

[0131] From the above equations (71) to (76), the voltage at the motor end to be observed can be found as shown in the following equations (77) and (78).

[0132]

number

[0133] Here, since the following equation (79) is obtained, the magnetic flux that was generated before the attenuation can be obtained by integrating the observed voltage value until it approaches 0. In other words, the magnetic flux can be obtained as shown in the following equation (80).

[0134]

number

[0135] Furthermore, since the following equation (81) is obtained, it can be expressed as the following equations (82) and (83). This results in the following equation (84).

[0136]

number

[0137] From this magnetic flux equation, the current i sd0 is the no-load current of induction motor 2 i sdn If so, the rated primary magnetic flux L s i sdn Leakage flux σL s i sdn It can be seen that the magnetic flux component obtained by subtracting

[0138] The induction motor 2 is a motor that can change the magnetic flux by applying a voltage. Therefore, there are various methods for determining the magnetic flux reference. Here, the rated angular frequency ω sn At rated voltage v snThe no-load current value that flows when the motor is operated at no load is the rated magnetic flux current i sn The value converted onto the DQ synchronous axis is the rated magnetic flux current i sdn The control conditions are as follows: sn is the phase voltage effective value, and the rated magnetic flux current i sn is the phase current effective value.

[0139] In this case, the operating point is the same as in the no-load test described above, so equations (20) and (21) are obtained in the same way. The sum of the squares of each component of the primary voltage expressed by equations (20) and (21) is the rated voltage V sn Since it is equal to the square of the amplitude, the rated primary magnetic flux L s i sdn is obtained by the following equations (85) and (86).

[0140]

number

[0141] The rated primary magnetic flux L thus obtained s i sdn The magnetic flux quantity obtained by multiplying by "1-σ", that is, the magnetic flux quantity expressed by the following equation (87), is the no-load current i sdn This is the amount of magnetic flux obtained when the no-load current i sdn is an unknown, that is, it is being identified, so the current value i sd0 Using the above, the target magnetic flux is determined as shown in the following equation (88).

[0142]

number

[0143] The applied current value i is set so that the target magnetic flux matches the magnetic flux value in equation (84). sd0 When is adjusted, the applied current value i sd0 is the no-load current i sdn In this way, the no-load current isdn Identify the no-load current i sdn Once identified, the primary inductance L can be calculated using equations (85) and (86). s Also, at this time, the value of the magnetic flux in equation (84) is the "1-e -1 Since the time it takes for the capacitance to reach a value equivalent to "1" is approximately the second-order time constant, the second-order time constant can also be measured at the same time.

[0144] The adjustment of the applied current value is performed, for example, according to the following rules. That is, n is the number of times the current value is applied. However, "n = 1, 2, 3 ...", that is, n is a natural number. When n = 1, for example, "Current (1) = √2 × In / 5" is given as the initial value. However, In is equivalent to the rated current effective value. When n ≥ 2, the current value, that is, the current command value, is calculated using the following equation (89). However, magnetic flux (0) = 0 and current (0) = 0.

[0145]

number

[0146] The current (n) is adjusted by equation (89) so that the target magnetic flux and the magnetic flux in equation (84), which is the integral of the voltage value, match. As a result, the no-load current identification value i sdn_calc can be made to match the current (n).

[0147]

number

[0148] The above formula (89) is obtained by the following idea: That is, as shown in the following formula (91), the ratio of the amount of change in current to the amount of change in magnetic flux is calculated from the past two values ​​of current and magnetic flux.

[0149]

number

[0150] As shown in the following equation (92), the amount of magnetic flux that is the result of the previous integration is calculated to what extent it is short of the target magnetic flux.

[0151]

number

[0152] As shown in the following equation (93), the current value for obtaining the magnetic flux deficiency is calculated by multiplying the magnetic flux deficiency by the ratio obtained above.

[0153]

number

[0154] As shown in the following equation (94), the amount of the current shortage is added to the previous current command to obtain the next current command value.

[0155]

number

[0156] From the relationships of the above equations (91) to (94), the next current command equation as shown in the following equation (95), that is, equation (89), is derived.

[0157]

number

[0158] The waveforms of each part when identifying the no-load current and the secondary time constant as described above are as shown in Fig. 3. In Fig. 3, the gate block is abbreviated as GB. In the induction motor driving device 1 of the first configuration example, the operation for acquiring the identified value of the no-load current and the identified value of the secondary time constant is carried out in the following manner.

[0159] The current command value generating unit 15 generates a first current command value i that is about 20% of the rated current of the induction motor 2.sdref_[1] is provided to the current regulator 10 for a first waiting time determined in advance. After the output of the power converter 6 is cut off and a second waiting time has elapsed, the motor constant identifier 11 converts the detected value of the phase-to-phase voltage onto the same control axis as the current command value to obtain a value v sdmeas While is below 0, calculate the magnetic flux [1] as shown in the following equation. Magnetic flux[1]=∫(-v sdmeas )dt

[0160] Here, the target magnetic flux is determined to be the magnetic flux amount obtained by subtracting the leakage magnetic flux calculated using the identified value of the leakage inductance from the rated primary magnetic flux of the induction motor 2. The current command value generating unit 15 calculates the second current command value i sdref_[2] is provided to the current adjusting unit 10. i sdref_[2] =i sdref_[1] + (target flux - flux [1]) × (i sdref_[1] ÷magnetic flux[1])

[0161] The motor constant identification unit 11 calculates the magnetic flux [2] in the same manner as when calculating the magnetic flux [1]. Here, when N is a natural number of 3 or more, the current command value generation unit 15 calculates the Nth current command value i sdref_[N] is provided to the current adjusting unit 10. i sdref_[N] =i sdref_[N-1] + (target flux - flux [N-1]) × (i sdref_[N-1] -i sdref_[N-2] )÷(magnetic flux[N-1]-magnetic flux[N-2])

[0162] The motor constant identification unit 11 calculates the magnetic flux [N] in the same manner as when calculating the magnetic flux [1]. By repeating these operations, i sdref_[N] By performing the convergence calculation, the no-load current identification value i sdn_calc get. i sdn_calc =i sdref_[N]

[0163] The current command value generating unit 15 generates the (N+1)th current command value i sdref_[N+1] Then, the Nth current command value i sdref_[N]is again applied to the current adjusting unit 10, and when calculating the magnetic flux [N+1] in the same manner as when calculating the magnetic flux [1], the magnetic flux [N+1] is calculated to be approximately equal to the target magnetic flux "1-e -1 " Time to double T r_est Such a measurement operation is performed one or more times, and the measured time T r_est The value of or multiple measured times T r_est The average value of r_calc Let us assume that.

[0164] <Regarding the induction motor drive device of the second configuration example> In the identification method using the induction motor driving device 1 of the first configuration example, it is necessary to detect the voltage value observed before the magnetic flux generated by current application attenuates after the gate is blocked, so the phase-to-phase voltage detection unit 12, which is a voltage detector, and the UV,WV / UVW converter 13 and UVW / dq converter 14, which are peripheral circuits, are required. From the viewpoint of keeping the number of parts as small as possible, it is desirable to be able to identify the no-load current and the secondary time constant in an induction motor driving device configured without a voltage detector, as in the first configuration example having a voltage detector. Below, an induction motor driving device of a second configuration example not having such a voltage detector will be described.

[0165] An induction motor driving device 21 of a second configuration example shown in Fig. 4 does not have a phase-to-phase voltage detection unit which is a voltage detector. The induction motor driving device 21 of the second configuration example differs from the induction motor driving device 1 of the first configuration example in that it has a control device 22 instead of the control device 7. The control device 22 differs from the control device 7 in that it omits the phase-to-phase voltage detection unit 12, the UV,WV / UVW converter 13 and the UVW / dq converter 14, and that it has a motor constant identification unit 23 instead of the motor constant identification unit 11.

[0166] The motor constant identification unit 23 determines the D-axis voltage command value v sdref and the D-axis current command i sdref or D-axis current detection value i sdmeasand the electric constants of induction motor 2 are identified based on the above. Details will be described later, but in the above configuration, the electric constants are identified as follows. That is, current command value generating unit 15 generates two different preset current command values ​​in a state in which the rotor of induction motor 2 is stopped. Then, motor constant identifying unit 23 identifies the no-load current and the secondary time constant based on the voltage command value after current command value generating unit 15 changes the current command value from a high level to a low level.

[0167] In the induction motor driving device 21 of the second configuration example, the operation for acquiring the identified value of the no-load current and the identified value of the secondary time constant is performed in the following flow. The current command value generating unit 15 generates the base current command value i sdref_base After the voltage command value v is applied to the current adjusting unit 10 for a predetermined first waiting time Twait_A, the motor constant identifying unit 23 identifies the voltage command value v sdref_base Memorize the following.

[0168] Then, the current command value generating unit 15 generates the base current command value i sdref_base The first current command value i sdref_[1] is given to the current adjusting unit 10 for the first waiting time Twait_A, and then the base current command value i sdref_base After a predetermined second waiting time Twait_B has elapsed since the switching to the motor constant identification unit 23, the voltage command value v sdref is the base current command value i sdref_base The voltage command value v sdref_base The magnetic flux [1] is calculated as follows while the magnetic flux is below Magnetic flux[1]=∫(v sdref_base -v sdref )dt

[0169] Here, the target magnetic flux is determined to be the magnetic flux amount obtained by subtracting the leakage magnetic flux amount calculated using the identified value of the leakage inductance from the rated primary magnetic flux of the induction motor 2. The current command value generating unit 15 calculates the second current command value i sdref_[2] is provided to the current adjusting unit 10. i sdref_[2] =i sdref_[1] + (target flux - flux [1]) × (i sdref_[1] ÷magnetic flux[1])

[0170] The motor constant identification unit 23 calculates the magnetic flux [2] in the same manner as when the magnetic flux [1] was calculated. Here, when N is a natural number of 3 or more, the current command value generation unit 15 calculates the Nth current command value i sdref_[N] is provided to the current adjusting unit 10. i sdref_[N] =i sdref_[N-1] + (target flux - flux [N-1]) × (i sdref_[N-1] -i sdref_[N-2] )÷(magnetic flux[N-1]-magnetic flux[N-2])

[0171] The motor constant identification unit 23 calculates the magnetic flux [N] in the same manner as when calculating the magnetic flux [1]. By repeating these operations, sdref_[N] By performing the convergence calculation, the no-load current identification value i sdn_calc get. i sdn_calc =i sdref_[N] -i sdref_base

[0172] The current command value generating unit 15 generates the (N+1)th current command value i sdref_[N+1] Then, the Nth current command value i sdref_[N] is again applied to the current adjusting unit 10, and when calculating the magnetic flux [N+1] in the same manner as when calculating the magnetic flux [1], the magnetic flux [N+1] is calculated to be approximately equal to the target magnetic flux "1-e -1 " Time to double T r_est Such a measurement operation is performed one or more times, and the measured time T r_est The value of or multiple measured times T r_est The average value of r_calc Let us assume that.

[0173] Next, a specific method for identifying each electrical constant implemented in the induction motor driving device 21 of the second configuration example will be described. As shown in FIG. 5, in the identification method of the second configuration example, instead of the gate block in the identification method of the first configuration example, a base current command value i sdref_base The method adopted is to continue applying a voltage.

[0174] In this case, "no-load current identification value + base current command value i sdref_base From the current value of ", the base current command value i sdref_base The voltage command after quickly decreasing the current to the current value of 1 is used as the voltage detection value. However, in order to do this, the following two points must be taken into consideration. [1] Removal of voltage value to maintain small current instead of gate block [2] Avoiding transients when switching to low current instead of gate blocking

[0175] <Removal of voltage value to maintain minute current> Base current command value i sdref_base The base voltage command value v sdref_base is measured in advance, and the base voltage command value v sdref_base The voltage value from which the difference is subtracted must be substituted for the previous voltage detection value and integrated. The magnetic flux obtained by such integration is expressed by the following equation (96).

[0176]

number

[0177] The current (n) is adjusted by equation (89) so that the target magnetic flux and the magnetic flux of equation (96), which is the integral of the voltage value, match. As a result, the no-load current identification value + base current command value i sdref_base The current value equivalent to " is adjusted as current (n). Therefore, the no-load current identification value i sdn_calc is expressed by the following equation (97).

[0178]

number

[0179] <Avoiding transient phenomena in current control> The current command value is "no-load current identification value + base current command value i sdref_base " to the base current command value i sdref_base When the load current is switched to the load current, the voltage command value, which is the output of the current controller while the actual current value is transitioning, also includes the compensation amount of the current controller. Therefore, in order to accurately identify the no-load current, it is necessary to remove the compensation amount corresponding to the output of the current controller during this transient phenomenon from the integral calculation of the voltage command that calculates the magnetic flux. For this purpose, it is effective not to perform the integral operation of the voltage command value for a preset time Twait_B after the start of the transition.

[0180] When the induction motor 2 is a relatively large capacity model, the secondary time constant is sufficiently long compared to the current response time constant of the current controller, so even if the integral action is not performed during the time Twait_B, the effect on the identification result of the no-load current value is small. However, when the induction motor 2 is a small capacity model with a short secondary time constant, the secondary time constant T r and the current response time constant T curr When the difference becomes small, the impact on identification accuracy cannot be ignored.

[0181] Therefore, the quadratic time constant T r and the current response time constant T curr When the difference between the current and the base current command value i sdref_base From the change in the voltage command value after reaching Twait_B, the voltage value due to the change in magnetic flux during the waiting time Twait_B, that is, the voltage value corresponding to equation (77), is estimated, and the magnetic flux amount is compensated for, thereby improving the accuracy of the no-load current identification value. Note that the magnetic flux amount in this case is an integral value. Specifically, a linear approximation as shown in Fig. 6 is performed.

[0182] The current command value is the base current command value i sdref_base The time when the current is switched to the base current command value isdref_base The time when the current has fully decayed is defined as "t=T0", and the current value is sufficiently below the base current command value i sdref_base The time when the current approaches the threshold is defined as "t=T1", and the doubled time is defined as T2. For example, T0 is "2 × current response time constant T curr " and T1 is "N × T curr In this case, for example, "N=5" can be used.

[0183] The timer setting values ​​T0, T1, and T2 are known, and V1 and V2 are the voltage command values ​​at time T1 and time T2, respectively. The slope of the change in the voltage command from time T1 to time T2 is obtained, and the voltage value V0 due to the magnetic flux change among the voltage command values ​​at time T0 is approximately calculated. Such an approximation can be performed based on the following equation (98).

[0184]

number

[0185] Here, the timer is set according to the following equations (99) to (101), where N is an integer.

[0186]

number

[0187] Then, the voltage value V0 is expressed by the following formula (102).

[0188]

number

[0189] When the magnetic flux change amount, which is the integral value from T0 to T1, is calculated by trapezoidal approximation, it becomes the following equation (103).

[0190]

number

[0191] Substituting V0 in the above formula (102) into the above formula (103), the integral value S of the voltage value of the magnetic flux change excluding the current control compensation amount from T0 to T1 is obtained. The integral of the voltage command value, which is the calculation of the magnetic flux, is calculated when the current value is sufficiently close to the base current command value i sdref_base This is because the compensation voltage command value, which is the output of the current controller, is not integrated. After that, the integral value S obtained as described above is added to the magnetic flux calculation value at the time point of "t=T2", so that the magnetic flux amount equivalent to the integral value of the voltage value generated by the secondary magnetic flux change before T1 is corrected, and it becomes possible to identify the no-load current with high accuracy.

[0192] As described above, in the second configuration example, when calculating the magnetic flux [1], the magnetic flux [2], the magnetic flux [N], and the magnetic flux [N+1], the current command value is set to the base current command value i sdref_base and from the amount of change over time of the voltage command value observed after the second waiting time Twait_B has elapsed, the amount of change in magnetic flux in the induction motor 2 during the second waiting time Twait_B is calculated as the amount of magnetic flux correction, and the amount of magnetic flux correction is added to the amounts of magnetic flux [1], magnetic flux [2], magnetic flux [N] and magnetic flux [N+1].

[0193] More specifically, in the second configuration example, when calculating the magnetic flux [1], the magnetic flux [2], the magnetic flux [N], and the magnetic flux [N+1], the current command value is set to the base current command value i sdref_base and linearly approximating the induced voltage caused by the magnetic flux change in the induction motor 2 during the second waiting time Twait_B from the amount of time change in the voltage command value observed after the second waiting time Twait_B has elapsed. The magnetic flux correction amount is calculated as the amount obtained by integrating the linearly approximated induced voltage over time during the second waiting time Twait_B, and the magnetic flux correction amount is added to the magnetic flux amounts of magnetic flux[1], magnetic flux[2], magnetic flux[N] and magnetic flux[N+1].

[0194] <Optimization of current control gain> In this case, it is desirable to set the gain of the current control to a gain that does not cause overshoot. This is because realizing a current response that does not cause overshoot has the effect of preventing a large compensation voltage value from being generated in the voltage command value. When the current controller is realized by a PI compensator, the proportional gain K p and integral gain K i can be obtained from the leakage inductance and primary resistance values ​​obtained in the previous section as shown in the following equations (104) and (105). Here, the current response angular frequency is ω curr Let us assume that.

[0195]

number

[0196] The derivation of such a current control gain will be explained below. First, the first line of equation (3) is written as equation (106) below.

[0197]

number

[0198] Here, the applied voltage is a DC amount, and since current is applied only to the D-axis when the induction motor 2 is stopped and the rotor is not rotating, the Q-axis current can be considered to be 0, and the Q-axis component of the secondary magnetic flux can also be considered to be 0. Taking this into consideration, equation (106) can be rearranged to obtain the following equation (107).

[0199]

number

[0200] Although there are differential terms between the primary current and the secondary magnetic flux, the change in the secondary time constant is sufficiently slow compared to the dynamics of the primary current, so the secondary magnetic flux can be considered to be a constant value with almost no change during the time until the current value achieves a step-like response of 50 to 100 Hz using a relatively high-speed current controller. Therefore, if the secondary magnetic flux is considered to be constant in the above formula (107) during the time when the current value responds immediately after the start of current control, that is, immediately after the current command is changed, the following formula (108) is established.

[0201]

number

[0202]

number

[0203] When the above equations (108) and (109) are expressed as a block diagram, it becomes as shown in FIG. 7. The transfer function G from the current command to the current value is c When (s) is calculated, it becomes the following equation (110).

[0204]

number

[0205] The current control response is ω curr In other words, when we want to change the current response shown in the above equation (110) to "response time constant T curr is 1 / ω curr If you want to achieve a "first-order lag response" then you should set the proportional gain K so that the following equation (111) holds. p and integral gain K i All that is required is to determine the following.

[0206]

number

[0207] By rearranging the above formula (111), the relationship shown in the following formula (112) is obtained. Then, by comparing the coefficients, the following formulas (113) and (114) are obtained.

[0208]

number

[0209] Therefore, the proportional gain K p and integral gain K i can be set as in the above-mentioned equations (104) and (105). Furthermore, when these equations are expressed using the identification equation, they become the following equations (115) and (116).

[0210]

number

[0211] <Optimization of identification sequence (waiting time)> Figure 8 is a chart showing the optimization of a series of operations related to the identification of four electrical constants, the primary resistance, leakage inductance, no-load current, and secondary time constant. In identifying the no-load current, it is desirable to have a current response without overshoot, so it is advisable to identify the primary resistance and leakage inductance first and then optimize the control gain of the current controller.

[0212] In the induction motor driving device 21 of the second configuration example that does not have a voltage detector, when identifying the no-load current, the base voltage command value v sdref_base is required, but the base current command value i sdref_base The voltage command required to apply the voltage is unknown. Therefore, the base voltage command value v sdref_base_ini is determined in advance using a value smaller than the previously identified primary resistance value, for example, as shown in the following equation (117).

[0213]

number

[0214] After identifying the primary resistance and leakage inductance, the current command value is set to the base current command value i sdref_base The secondary time constant is roughly adjusted by using the induced voltage equivalent that occurs in the voltage command value after switching to the base voltage command initial value v sdref_base_ini By measuring the time it takes to exceed this value, the approximate secondary time constant T r_temp Request.

[0215] In the case of the induction motor driving device 1 of the first configuration example having a voltage detector, the observed induced voltage will eventually be close to 0, so as an example of a negative and minute value, the above-mentioned base voltage command initial value v sdref_base_ini The negative value is defined as the threshold value, and the time until the detection voltage becomes higher than the threshold value is measured. r_temp Request.

[0216] The secondary time constant rough adjustment value T r_temp The waiting time Twait_A is determined based on, for example, the secondary time constant coarse adjustment value T r_temp It is advisable to set this to about five times the waiting time Twait_A. The identification sequence can be optimized by using the waiting time Twait_A as the current application time and the integration time for magnetic flux calculation in the subsequent identification of the no-load current value.

[0217] As described above, in the induction motor driving device 21 of the second configuration example, the identification sequence is optimized as follows. s_calc and the leakage inductance identification value L f_calc The base current command value i, which is the initial current command value when identifying the no-load current, is obtained from the current command value used during operation to obtain sdref_baseWhen the voltage command value is observed, the coarse adjustment value T r_temp Measure.

[0218] In the induction motor driving device 1 of the first configuration example, the identified value R of the primary resistance s_calc and the leakage inductance identification value L f_calc After obtaining the above, the output of the power converter 6 is temporarily cut off, and then the voltage detection value is observed to obtain the rough adjustment value T r_temp In this case, the current response angular frequency is measured as ω curr When the first waiting time Twait_A is set to the coarse adjustment T r_temp and set the second waiting time Twait_B to about 5 to 10 times the current response angular frequency ω curr The reciprocal of this should be between 2 and 5 times the value.

[0219] <Acquisition of saturation characteristics in no-load current identification> It has been shown that the target magnetic flux level in the identification of the no-load current is determined as shown in equations (85) and (86). This is because the rated angular frequency ω sn At rated voltage v sn The no-load current value that flows when the device is operated at no load is the rated magnetic flux current i sn The value converted onto the DQ synchronous axis is the rated magnetic flux current i sdn is the amount of magnetic flux generated when this current value flows on the D axis, and this is defined as the rated magnetic flux.

[0220] As shown in Fig. 9, by setting the magnetic flux amount of, for example, 0.75 times, 1.0 times, 1.25 times, and 1.5 times the rated magnetic flux as the target magnetic flux and performing the same operation as in identifying the no-load current, the D-axis current level for generating each magnetic flux amount can be identified. Specific operation examples for such identification include, for example, a first operation example shown in Fig. 10, a second operation example shown in Fig. 11, and a third operation example shown in Fig. 12. If the electrical constant does not change depending on the magnetic flux amount, the magnetic flux and the current value are proportional, but magnetic flux becomes difficult to generate due to the influence of magnetic saturation characteristics, and the deviation from the proportional relationship becomes greater as the magnetic flux amount increases.

[0221] As described above, in this embodiment, the motor constant identification units 11, 23 are configured to select the target flux from at least three amounts: a rated flux amount obtained by subtracting the leakage flux amount calculated using the identified value of the leakage inductance from the rated primary flux of the induction motor 2, a flux amount greater than the rated flux amount, and a flux amount smaller than the rated flux amount.When each of the three target fluxes is selected, the no-load current is identified to obtain the magnetic saturation characteristics of the induction motor 2.

[0222] <Optimization of the method for identifying primary resistance and leakage inductance> In this embodiment, the operation for obtaining the identified value of the primary resistance and the identified value of the leakage inductance is performed in the following manner before the operation for obtaining the identified value of the no-load current and the identified value of the secondary time constant is performed. First, the current command value generating unit 15 outputs a current command value i sdref0 is given for a predetermined time T0. After the predetermined time T0 has elapsed, the motor constant identification units 11 and 23 identify the voltage command value v sdref0 and the current command value i sdref0 Or the steady-state current detection value i sd0 Using this, the primary resistance R is identified. s_calc Calculate.

[0223] Next, the voltage command generating unit 16 calculates the identified value R s_calc After calculating the voltage command value, the voltage command value v sdref0 and the voltage command value v sdref0 A coefficient K smaller than 1 for d The amplitude of the sine wave is multiplied by and the coefficient K d is adjusted so that the amplitude of the AC component of the observed current is equal to a predetermined value. Then, the motor constant identification units 11 and 23 calculate the AC amount of the current value observed by the current detection units 8U and 8W, the adjusted coefficient K d , voltage command value v sdref0 Identification value of leakage inductance L f_calc Calculate.

[0224] Identification value of primary resistance R s_calc , the identified leakage inductance value L f_calc is the proportional gain K of the proportional-integral compensator provided in the current adjustment unit 10 p and integral gain K i Specifically, the current response angular frequency is calculated as ω curr Then, the identified value of the primary resistance R s_calc and the leakage inductance identification value L f_calc The proportional gain K in the proportional-integral compensator is set using p and integral gain K i The values ​​of are set as follows: K p =ω curr K i =ω curr ×R s_calc ÷L f_calc

[0225] As described above, the identification method performed by the induction motor driving device 1, 21 of this embodiment makes it possible to accurately identify the electrical constants of the induction motor 2 with the rotor of the induction motor 2 stopped. In particular, the identification method of this embodiment makes it possible to make the identification of the no-load current and the secondary time constant performed with the rotor of the induction motor 2 stopped less susceptible to the influence of identification errors in the primary resistance. Furthermore, since the accuracy of the leakage inductance affects the identification accuracy of the no-load current, the identification method of this embodiment employs a method that can maintain good accuracy in identifying the leakage inductance.

[0226] In addition, in this embodiment, an optimization method is adopted in which the accuracy is improved by optimizing the calculation process so as not to be affected by voltage compensation by current control when performing integral calculation of the voltage command value immediately after switching of the current level in no-load current identification. Furthermore, in this embodiment, the current control response is set to a gain setting without overshoot, and the voltage compensation value by current control is prevented from becoming a value higher than necessary, thereby improving the identification accuracy of the no-load current.

[0227] The no-load current is also the rated magnetic flux current at the applied voltage, and it changes due to the influence of the magnetic saturation characteristics depending on the applied voltage value. Therefore, in the method for identifying the no-load current of this embodiment, by identifying the no-load current according to the applied voltage, i.e., the set magnetic flux level, it is also possible to identify the magnetic saturation characteristics of the no-load current.

[0228] According to this embodiment, even if the induction motor 2 to be driven is a motor whose electrical constants are unknown, by using the above-mentioned identification method or the like, accurate electrical information of the induction motor 2, such as slip, can be obtained using sensorless vector control technology while the induction motor 2 is in operation, resulting in the excellent effect of enabling highly accurate sensorless vector control.

[0229] (Other embodiments) The present invention is not limited to the embodiments described above and shown in the drawings, and can be modified, combined, or expanded as desired without departing from the spirit and scope of the present invention. The numerical values ​​and the like shown in the above embodiment are merely examples and are not intended to be limiting.

[0230] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0231] In the drawing, 1 and 21 indicate an induction motor driving device, 2 indicates an induction motor, 6 indicates a power converter, 8U and 8W indicate current detection units, 10 indicates a current adjustment unit, 11 and 23 indicate a motor constant identification unit, 12 indicates a phase-to-phase voltage detection unit, 15 indicates a current command value generation unit, and 16 indicates a voltage command generation unit.

Claims

1. a power converter that converts a DC voltage into a three-phase AC voltage with variable voltage and frequency and supplies the AC voltage to an induction motor; A phase-to-phase voltage detection unit that detects phase-to-phase voltages between two or more phases of the induction motor; A current detection unit that detects a current of the induction motor; a current adjustment unit that calculates a voltage adjustment value so that a current detection value, which is a value obtained by converting the detection value of the current onto the same control axis as the current command value, coincides with the current command value; a current command value generating unit that generates the current command value and provides the current command value to the current adjusting unit; a voltage command generating unit that generates a voltage command value by using the voltage adjustment value obtained from the current adjusting unit; a motor constant identification unit that identifies an electrical constant of the induction motor based on the detected value of the interphase voltage or the voltage command value and the current command value or the current detected value; Equipped with The electric constants identified by the motor constant identification unit include identified values ​​of a primary resistance, a leakage inductance, a no-load current, and a secondary time constant, the current command value generating unit generates the current command value having a preset magnitude in a state in which a rotor of the induction motor is stopped; After a preset time has elapsed and the output of the power converter is cut off, The induction motor drive device, wherein the motor constant identification unit identifies the no-load current and the secondary time constant based on the detected value of the phase-to-phase voltage.

2. a power converter that converts a DC voltage into a three-phase AC voltage with variable voltage and frequency and supplies the AC voltage to an induction motor; A current detection unit that detects a current of the induction motor; a current adjustment unit that calculates a voltage adjustment value so that a current detection value, which is a value obtained by converting the detection value of the current onto the same control axis as the current command value, coincides with the current command value; a current command value generating unit that generates the current command value and provides the current command value to the current adjusting unit; a voltage command generating unit that generates a voltage command value by using the voltage adjustment value obtained from the current adjusting unit; a motor constant identification unit that identifies an electrical constant of the induction motor based on the voltage command value, and the current command value or the current detection value; Equipped with The electric constants identified by the motor constant identification unit include identified values ​​of a primary resistance, a leakage inductance, a no-load current, and a secondary time constant, the current command value generating unit generates the current command values ​​having two different magnitudes that are set in advance in a state in which a rotor of the induction motor is stopped; an induction motor drive device in which the motor constant identification unit identifies the no-load current and the secondary time constant based on the voltage command value after the current command value generation unit changes the current command value from a high level to a low level.

3. The current command value generating unit generates a first current command value i ｓｄｒｅｆ＿［１］ to the current adjusting unit for a predetermined first waiting time, After a predetermined second waiting time has elapsed since the output of the power converter is cut off, The motor constant identification unit converts the detected value of the phase-to-phase voltage onto the same control axis as the current command value, ｓｄｍｅａｓ While is below 0, calculate the magnetic flux [1] shown in the following formula, Magnetic flux [1] = ∫(-v ｓｄｍｅａｓ ) dt A target magnetic flux is set to a magnetic flux amount obtained by subtracting a leakage magnetic flux amount calculated using the identified value of the leakage inductance from a rated primary magnetic flux of the induction motor, Using the magnetic flux [1], the second current command value i is calculated by the following formula: ｓｄｒｅｆ＿［２］ is applied to the current adjusting unit, i ｓｄｒｅｆ＿［２］ = i ｓｄｒｅｆ＿［１］ + (target flux - flux [1]) x (i ｓｄｒｅｆ＿［１］ ÷magnetic flux [1]) Calculate the magnetic flux [2] in the same manner as when calculating the magnetic flux [1], When N is a natural number greater than or equal to 3, The Nth current command value i is calculated by the following formula: ｓｄｒｅｆ＿［Ｎ］ is applied to the current adjusting unit, i ｓｄｒｅｆ＿［Ｎ］ = i ｓｄｒｅｆ＿［Ｎ－１］ + (target magnetic flux - magnetic flux [N-1]) x (i ｓｄｒｅｆ＿［Ｎ－１］ -i ｓｄｒｅｆ＿［Ｎ－２］ ) ÷ (magnetic flux [N-1] - magnetic flux [N-2]) Calculate the magnetic flux [N] in the same manner as when calculating the magnetic flux [1]. By repeating these operations, ｓｄｒｅｆ＿［Ｎ］ By performing the convergence calculation, the no-load current identification value i ｓｄｎ＿ｃａｌｃ And i ｓｄｎ＿ｃａｌｃ =i ｓｄｒｅｆ＿［Ｎ］ N+1th current command value i ｓｄｒｅｆ＿［Ｎ＋１］ As the Nth current command value i ｓｄｒｅｆ＿［Ｎ］ is again provided to the current adjusting unit, and the magnetic flux [N+1] is calculated in the same manner as when the magnetic flux [1] was calculated. When the magnetic flux [N+1] is calculated, the magnetic flux [N+1] is approximately (1-e －１ ) Time required for the ｒ＿ｅｓｔ A measurement operation is performed to measure the time T ｒ＿ｅｓｔ or a number of measured times T ｒ＿ｅｓｔ The average value of the second-order time constant T ｒ＿ｃａｌｃ 2. The induction motor drive device according to claim 1 .

4. The current command value generating unit generates a base current command value i which is a relatively small current value determined in advance when the induction motor is stopped. ｓｄｒｅｆ＿ｂａｓｅ to the current adjusting unit for a predetermined first waiting time, The motor constant identification unit detects the voltage command value v ｓｄｒｅｆ＿ｂａｓｅ The Then, the current command value generating unit calculates the base current command value i ｓｄｒｅｆ＿ｂａｓｅ The larger first current command value i ｓｄｒｅｆ＿［１］ is provided to the current adjusting unit for the first waiting time, and then the base current command value i ｓｄｒｅｆ＿ｂａｓｅ After a second predetermined waiting time has elapsed after switching to The motor constant identification unit determines the voltage command value v ｓｄｒｅｆ is the base current command value i ｓｄｒｅｆ＿ｂａｓｅ The voltage command value v ｓｄｒｅｆ＿ｂａｓｅ Calculate the magnetic flux [1] shown in the following formula while the magnetic flux is below Magnetic flux [1] = ∫(v ｓｄｒｅｆ＿ｂａｓｅ -v ｓｄｒｅｆ ) dt A target magnetic flux is set to a magnetic flux amount obtained by subtracting a leakage magnetic flux amount calculated using the identified value of the leakage inductance from a rated primary magnetic flux of the induction motor, The second current command value i is calculated by the following formula: ｓｄｒｅｆ＿［２］ is applied to the current adjusting unit, i ｓｄｒｅｆ＿［２］ = i ｓｄｒｅｆ＿［１］ + (target flux - flux [1]) x (i ｓｄｒｅｆ＿［１］ ÷magnetic flux [1]) Calculate the magnetic flux [2] in the same manner as when calculating the magnetic flux [1], When N is a natural number greater than or equal to 3, The Nth current command value i is calculated by the following formula: ｓｄｒｅｆ＿［Ｎ］ is applied to the current adjusting unit, i ｓｄｒｅｆ＿［Ｎ］ = i ｓｄｒｅｆ＿［Ｎ－１］ + (target magnetic flux - magnetic flux [N-1]) x (i ｓｄｒｅｆ＿［Ｎ－１］ -i ｓｄｒｅｆ＿［Ｎ－２］ ) ÷ (magnetic flux [N-1] - magnetic flux [N-2]) Calculate the magnetic flux [N] in the same manner as when calculating the magnetic flux [1]. By repeating these operations, ｓｄｒｅｆ＿［Ｎ］ By performing the convergence calculation, the no-load current identification value i ｓｄｎ＿ｃａｌｃ And i ｓｄｎ＿ｃａｌｃ =i ｓｄｒｅｆ＿［Ｎ］ -i ｓｄｒｅｆ＿ｂａｓｅ N+1th current command value i ｓｄｒｅｆ＿［Ｎ＋１］ As the Nth current command value i ｓｄｒｅｆ＿［Ｎ］ is again provided to the current adjusting unit, and the magnetic flux [N+1] is calculated in the same manner as when the magnetic flux [1] was calculated. When the magnetic flux [N+1] is calculated, the magnetic flux [N+1] is approximately (1-e －１ ) Time required for the ｒ＿ｅｓｔ A measurement operation is performed to measure the time T ｒ＿ｅｓｔ or a number of measured times T ｒ＿ｅｓｔ The average value of the second-order time constant T ｒ＿ｃａｌｃ 3. The induction motor drive device according to claim 2 .

5. The motor constant identification unit is When calculating the magnetic flux [1], the magnetic flux [2], the magnetic flux [N], and the magnetic flux [N+1], The current command value is set to the base current command value i ｓｄｒｅｆ＿ｂａｓｅ and calculating, from a time change amount of the voltage command value observed after the second waiting time has elapsed, a magnetic flux change amount in the induction motor during the second waiting time as a magnetic flux correction amount; 5. The induction motor drive device according to claim 4, wherein the magnetic flux correction amount is added to the magnetic flux amounts of the magnetic flux [1], the magnetic flux [2], the magnetic flux [N] and the magnetic flux [N+1].

6. The motor constant identification unit is the target magnetic flux can be selected from at least three values: a rated magnetic flux amount obtained by subtracting a leakage magnetic flux amount calculated using an identified value of the leakage inductance from a rated primary magnetic flux of the induction motor; a magnetic flux amount larger than the rated magnetic flux amount; and a magnetic flux amount smaller than the rated magnetic flux amount; 6. The induction motor drive device according to claim 3, wherein the magnetic saturation characteristics of the induction motor are obtained by identifying the no-load current when each of the three target magnetic fluxes is selected.

7. before performing the operation for obtaining the identified value of the no-load current and the identified value of the secondary time constant, The current command value generating unit outputs a current command value i ｓｄｒｅｆ０ is given for a predetermined time T0, After the predetermined time T0 has elapsed, the motor constant identification unit determines the voltage command value v ｓｄｒｅｆ０ and the current command value i ｓｄｒｅｆ０ Or the current detection value i ｓｄ０ and the primary resistance is identified by R ｓ＿ｃａｌｃ Calculate The voltage command generating unit determines an identified value R ｓ＿ｃａｌｃ As the voltage command value after the calculation, the voltage command value v ｓｄｒｅｆ０ and the voltage command value v ｓｄｒｅｆ０ A coefficient K smaller than 1 for ｄ A sine wave with an amplitude multiplied by and a value added to The coefficient K ｄ Adjusting the amplitude of the AC component of the observed current to a value equivalent to a predetermined magnitude; The motor constant identification unit determines the AC amount of the current value observed by the current detection unit, the adjusted coefficient K ｄ , the voltage command value v ｓｄｒｅｆ０ to the identified leakage inductance value L ｆ＿ｃａｌｃ Calculate The current adjusting unit includes a proportional integral compensator that performs PI control, The identified value R of the primary resistance ｓ＿ｃａｌｃ , the identified leakage inductance value L ｆ＿ｃａｌｃ The induction motor drive device according to claim 3 , wherein the proportional gain and integral gain of the proportional-integral compensator are calculated using the above formula:

8. before performing the operation for obtaining the identified value of the no-load current and the identified value of the secondary time constant, The identified value R of the primary resistance ｓ＿ｃａｌｃ and the identified leakage inductance value L ｆ＿ｃａｌｃ and performing an operation to obtain the Current response angular frequency is ω ｃｕｒｒ Then, the identified value R of the primary resistance ｓ＿ｃａｌｃ and the identified leakage inductance value L ｆ＿ｃａｌｃ The proportional gain K in the proportional-integral compensator is set using ｐ and integral gain K ｉ Set the values ​​of as follows: K ｐ =ω ｃｕｒｒ K ｉ =ω ｃｕｒｒ ×R ｓ＿ｃａｌｃ ÷L ｆ＿ｃａｌｃ 8. An induction motor drive system according to claim 7.

9. In the case where the phase-to-phase voltage detection unit is not provided, the identified value R of the primary resistance ｓ＿ｃａｌｃ and the identified leakage inductance value L ｆ＿ｃａｌｃ The base current command value i i , which is an initial current command value when identifying the no-load current, is obtained from the current command value used in the operation to obtain ｓｄｒｅｆ＿ｂａｓｅ When the voltage command value is observed, the coarse adjustment value T ｒ＿ｔｅｍｐ Measure In the case where the phase-to-phase voltage detection unit is provided, the identified value R of the primary resistance ｓ＿ｃａｌｃ and the identified leakage inductance value L ｆ＿ｃａｌｃ After obtaining the above, the output of the power converter is temporarily cut off, and then the voltage detection value is observed to obtain the coarse adjustment value T ｒ＿ｔｅｍｐ Measure Current response angular frequency is ω ｃｕｒｒ When the first waiting time is set to T ｒ＿ｔｅｍｐ and the second waiting time is set to about 5 to 10 times the current response angular frequency ω ｃｕｒｒ 8. The induction motor drive device according to claim 7, wherein the input current is set to about 2 to 5 times the reciprocal of

10. In the case where the phase-to-phase voltage detection unit is not provided, the identified value R of the primary resistance ｓ＿ｃａｌｃ and the identified leakage inductance value L ｆ＿ｃａｌｃ The base current command value i i , which is an initial current command value when identifying the no-load current, is obtained from the current command value used in the operation to obtain ｓｄｒｅｆ＿ｂａｓｅ When the voltage command value is observed, the coarse adjustment value T ｒ＿ｔｅｍｐ Measure In the case where the phase-to-phase voltage detection unit is provided, the identified value R of the primary resistance ｓ＿ｃａｌｃ and the identified leakage inductance value L ｆ＿ｃａｌｃ After obtaining the above, the output of the power converter is temporarily cut off, and then the voltage detection value is observed to obtain the coarse adjustment value T ｒ＿ｔｅｍｐ Measure The first waiting time is a rough adjustment T ｒ＿ｔｅｍｐ and the second waiting time is set to about 5 to 10 times the current response angular frequency ω ｃｕｒｒ 9. The induction motor drive device according to claim 8, wherein the input current is set to about 2 to 5 times the reciprocal of

Images