Inverter controller and air blower

Abstract

To provide an inverter controller that can more reliably control output dispersions of a permanent magnet synchronous motor controlled by an inverter.SOLUTION: A constant estimation unit 32 estimates an individual constant that is a constant related to the characteristics of an individual permanent magnet synchronous motor 11, which varies due to at least one of the manufacturing error and use environment. A correction unit 33 corrects constant output information on the basis of a comparison result by comparing the individual constant estimated by the constant estimation unit 32 with a reference constant.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an inverter control device and a blower fan.

Background Art

[0002] In a conventional fan motor control device, the variation in the generated torque is suppressed by using the back electromotive force constant ke estimated during sensorless vector control and applying correction to the torque current Iq. The back electromotive force constant ke is proportional to the torque constant kT (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, for example, in the case of a ventilation blower using a sirocco fan, control may be required such that the output is a constant air volume. In contrast, in the conventional fan motor control device as described above, variations in the air volume cannot be sufficiently suppressed with respect to variations such as variations in magnet attachment during manufacturing and variations in the ambient environmental temperature.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to obtain an inverter control device and a blower fan that can more reliably suppress variations in the output of a permanent magnet synchronous motor controlled by an inverter.

Means for Solving the Problems

[0006] The inverter control device according to the present disclosure includes a control device main body that controls an inverter connected to a permanent magnet synchronous motor based on constant output information, which is information indicating the relationship between the rotational speed and the torque current when causing the permanent magnet synchronous motor to perform a constant output operation, the generated torque of the permanent magnet synchronous motor, and the rotational speed of the permanent magnet synchronous motor, a constant estimation unit that estimates an individual constant, which is a constant related to the characteristics of an individual permanent magnet synchronous motor that varies due to at least one of manufacturing errors and usage environments, and a correction unit that compares the individual constant estimated by the constant estimation unit with a reference constant and corrects the constant output information based on the comparison result.

Effect of the Invention

[0007] According to the present disclosure, variations in the output of a permanent magnet synchronous motor controlled by an inverter can be more reliably suppressed.

Brief Description of the Drawings

[0008]

Figure 1

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Figure 11

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described with reference to the drawings. Embodiment 1. FIG. 1 is a schematic configuration diagram showing a blower according to Embodiment 1. The blower of Embodiment 1 is, for example, a ventilation blower. In the figure, the blower has a blower main body 10, an inverter 20, and an inverter control device 30.

[0010] The blower main body 10 has a permanent magnet synchronous motor 11, a housing 12, and a fan 13. The permanent magnet synchronous motor 11 and the fan 13 are provided in the housing 12. The permanent magnet synchronous motor 11 rotates the fan 13. The fan 13 of Embodiment 1 is a sirocco fan.

[0011] The permanent magnet synchronous motor 11 has a rotor (not shown) and a stator (not shown). A plurality of permanent magnets are provided on the outer periphery of the rotor. That is, the permanent magnet synchronous motor of Embodiment 1 is a surface magnet type permanent magnet synchronous motor. The stator has an iron core and a plurality of coils. When a two-phase or three-phase AC voltage is applied to the stator, the rotor rotates and torque is generated.

[0012] The inverter 20 is connected to the permanent magnet synchronous motor 11. Further, the inverter 20 generates an AC voltage for driving the permanent magnet synchronous motor 11 from a DC voltage. The output of the inverter 20 is input to the permanent magnet synchronous motor 11.

[0013] In addition, the inverter 20 outputs, to the permanent magnet synchronous motor 11, a voltage whose effective value of the line voltage becomes the effective value of a target AC voltage by switching a plurality of power semiconductors. As each power semiconductor, for example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor) is used.

[0014] The energization method of the inverter 20 may be a 120-degree energization method or a 180-degree energization method. Further, the voltage output from the inverter 20 may be a two-phase voltage or a three-phase voltage according to the type of the connected motor.

[0015] The inverter control device 30 controls the inverter 20.

[0016] FIG. 2 is a block diagram showing the control system of the blower in FIG. 1. The inverter control device 30 includes, as functional blocks, a control device main body 31, a constant estimation unit 32, and a correction unit 33.

[0017] The control device main body 31 controls the inverter 20 based on the current generated torque generated by the permanent magnet synchronous motor 11, the current rotational speed of the permanent magnet synchronous motor, and a constant output map as constant output information. The constant output map is information indicating the relationship between the rotational speed and the torque current when causing the permanent magnet synchronous motor 11 to perform a constant output operation. The constant output operation of the permanent magnet synchronous motor 11 in the blower is an operation in which the output of the fan 13 becomes a constant air volume.

[0018] The control device main body 31 includes, as functional blocks, a storage unit 34, a torque calculation unit 35, a target rotational speed calculation unit 36, and an output calculation unit 37.

[0019] The storage unit 34 stores a constant output map and a reference constant. The reference constant is a constant serving as a reference for calculating the torque current in the constant output map.

[0020] The torque calculation unit 35 calculates the current generated torque of the permanent magnet synchronous motor 11. The generated torque can be obtained by multiplying the torque constant kT by the component that contributes to the generated torque in the current flowing from the inverter 20 to the permanent magnet synchronous motor 11.

[0021] The torque constant kT is obtained from the following equation.

[0022] kT = Pn × Φ × (iq - id) / iq

[0023] Here, Pn is the number of pole pairs, Φ is the magnetic flux density, iq is the q-axis current (torque current), and id is the d-axis current. The d-axis is the direction of the field magnetic flux generated by the permanent magnet of the rotor. The q-axis is the direction advanced by 90° in electrical angle from the d-axis. It is assumed that there is no magnetic flux difference between the d-axis and the q-axis.

[0024] The current of the permanent magnet synchronous motor 11 is detected by the current detection unit 21. The current detection unit 21 detects the current flowing from the inverter 20 to the permanent magnet synchronous motor 11. As the current detection unit 21, a current transformer can be used. Also, the current detection unit 21 may be configured to measure the voltage generated by the current flowing through a shunt resistor with low resistance.

[0025] The signal from the current detection unit 21 is input to the torque calculation unit 35. The torque calculation unit 35 obtains the current values in each phase of the permanent magnet synchronous motor 11 based on the signal from the current detection unit 21. At this time, the torque calculation unit 35 may detect the current values of two phases and calculate the current value of the remaining one phase by utilizing the fact that the sum of the current values of the three-phase alternating current is 0.

[0026] After calculating the current values of each phase, the torque calculation unit 35 calculates the component that contributes to the generated torque and the component that does not contribute to the generated torque. In the case of the permanent magnet synchronous motor 11, the component that contributes to the generated torque is the q-axis current iq, and the component that does not contribute to the generated torque is the d-axis current id.

[0027] Since a general method can be used to convert the three-phase alternating current in a three-phase motor or the two-phase alternating current in a two-phase motor into the d-axis current and the q-axis current, the description is omitted here.

[0028] In the axis conversion, the magnetic pole position information of the rotor of the permanent magnet synchronous motor 11 is required. For detecting the magnetic pole position, a Hall IC sensor may be used, or a method of estimating the magnetic pole position such as sensorless vector control may be used.

[0029] Based on the generated torque calculated by the torque calculation unit 35, the rotation speed information which is the information of the current rotation speed of the permanent magnet synchronous motor 11, and a constant output map, the target rotation speed calculation unit 36 calculates the target torque at the current rotation speed. Then, the target rotation speed calculation unit 36 compares the current generated torque with the target torque.

[0030] When the current generated torque is smaller than the target torque, the target rotation speed calculation unit 36 sends a command to the output calculation unit 37 to increase the output of the inverter 20 from the current value.

[0031] When the current generated torque is larger than the target torque, the target rotation speed calculation unit 36 sends a command to the output calculation unit 37 to decrease the output of the inverter 20 from the current value.

[0032] How much to increase or decrease the output of the inverter 20 may be determined in proportion to the difference between the current generated torque and the target torque, or may be determined from the difference and the integration of the difference such as proportional integral control.

[0033] As the rotation speed information, in the case of the permanent magnet synchronous motor 11, the driving frequency may be directly used by utilizing the fact that the driving frequency of the inverter 20 matches the mechanical frequency determined by the number of poles of the permanent magnet synchronous motor 11. Also, the rotation speed information may be a value calculated based on the signal from the current detection unit 21. Further, the rotation speed information may be a value separately obtained from a device external to the inverter control device 30, for example, a rotation sensor.

[0034] Based on the command determined by the target rotation speed calculation unit 36, the output calculation unit 37 determines the AC voltage and frequency in the driving of the inverter 20 and outputs them to the inverter 20.

[0035] When performing vector control on the permanent magnet synchronous motor 11, the AC voltage and frequency may be changed simultaneously so that the d-axis current id becomes minimum. Also, for simplicity, only the AC voltage may be changed first, and then the frequency may be changed later so that the d-axis current id becomes minimum based on the calculated d-axis current id and q-axis current iq, and the generated torque may be converged to the target torque.

[0036] When the voltage and frequency are changed separately, the control period of the output calculation unit 37, that is, the update period, may be set to a shorter period than the update period of the target value in the target rotation speed calculation unit 36. This is because when the voltage and frequency are changed separately, the generated torque changes when the voltage is changed, and if output correction is performed by the target rotation speed calculation unit 36, there is a risk that the generated torque will not converge to the target torque.

[0037] The constant estimation unit 32 estimates individual constants. The individual constants are constants related to the characteristics of each permanent magnet synchronous motor 11. Also, the individual constants are constants that vary due to at least one of manufacturing errors and the use environment.

[0038] The correction unit 33 compares the individual constants estimated by the constant estimation unit with the reference constants and corrects the constant output map based on the comparison result.

[0039] FIG. 3 is an explanatory diagram showing a constant output map when variations of individual permanent magnet synchronous motors 11 are not considered. FIG. 4 is an explanatory diagram showing the constant output map in the inverter control device 30 of Embodiment 1. In FIGS. 3 and 4, the left graph shows the relationship between the rotation speed N and the torque current iq, respectively. In FIGS. 3 and 4, the right graph shows the relationship between the rotation speed N and the generated torque T, respectively.

[0040] Also, in FIGS. 3 and 4, the constant air volume curve is a curve representing the relationship between the torque current Iq and the rotational speed N when the air volume output by the blower is constant. Instead of the constant air volume curve, a broken line approximating the curve may be used.

[0041] The inverter control device 30 controls the inverter 20 so as to follow the constant air volume curve. Thereby, at any pressure loss, the constant output operation of the permanent magnet synchronous motor 11 is performed, and a constant air volume is provided by the blower.

[0042] In FIGS. 3 and 4, the plurality of curves indicated by the dashed lines each represent a pressure loss curve. Also, the pressure loss curve marked with "fully closed side" is the pressure loss curve when the blower outlet is blocked. The pressure loss curve marked with "open side" is the pressure loss curve when the blower outlet is not blocked.

[0043] The permanent magnet synchronous motor 11 is operated at the torque current Iq and the rotational speed N on the pressure loss curve according to the output voltage of the inverter control device 30. The pressure loss curve is not estimated in control.

[0044] The blower is driven at the intersection of the constant air volume curve and the pressure loss curve. In this case, as shown in FIG. 3, if there is a variation in the electromotive force constant ke, even if the control is performed along the constant air volume curve, there will be a variation in the generated torque and a variation in the rotational speed of each permanent magnet synchronous motor 11. As a result, there will also be a variation in the air volume of each blower. Since the torque constant kT is in a proportional relationship with the electromotive force constant ke, the same applies to the torque constant kT.

[0045] On the other hand, in the inverter control device 30 of Embodiment 1, as shown in FIG. 4, when the electromotive force constant ke is larger than the reference constant ke typ., the torque current Iq is decreased. Also, when the electromotive force constant ke is smaller than the reference constant ke typ., the torque current Iq is increased. Thereby, the variation in the rotational speed of each permanent magnet synchronous motor 11 is suppressed, and the variation in the air volume of each blower is also suppressed.

[0046] Next, the specific operation of the constant estimation unit 32 will be described. Here, the case where the torque constant kT is used as the individual constant will be described.

[0047] The constant estimation unit 32 estimates the torque constant kT by any one of the following first estimation method, second estimation method, and third estimation method.

[0048] <First Estimation Method> The first estimation method is a method of measuring the induced voltage of the permanent magnet synchronous motor 11 and estimating the torque constant kT from the measured induced voltage.

[0049] In the permanent magnet synchronous motor 11, an induced voltage proportional to the electromotive force constant ke × the rotational speed N of the permanent magnet synchronous motor 11 is generated. Therefore, if the induced voltage can be measured, the electromotive force constant ke can be calculated from the induced voltage ÷ rotational speed N. If the electromotive force constant ke can be calculated, since the electromotive force constant ke and the torque constant kT are in a proportional relationship, the torque constant kT can be calculated.

[0050] However, in a state where an AC voltage is being output from the inverter 20, since the output voltage of the inverter 20 exceeds the induced voltage, the induced voltage cannot be measured. On the other hand, if the output of the inverter 20 is in the off state and the permanent magnet synchronous motor 11 is coasting, the induced voltage can be measured.

[0051] Specific measurement timings of the induced voltage include (1) during the trial operation of the product and (2) after the operation of the product has stopped.

[0052] (1) During the trial operation of the product In this case, as part of the confirmation work during the trial operation, the output from the inverter 20 to the permanent magnet synchronous motor 11 is temporarily stopped, and the induced voltage due to coasting rotation is measured.

[0053] In this case, a configuration may be adopted in which a measurement circuit is connected only when the output of the inverter 20 is in the off state, using a sequence component such as a relay.

[0054] Also, by repeating stop → operation → stop so that the rotational speed of coasting rotation falls within the set value, the rotational speed fluctuation during coasting rotation can be suppressed, and the measurement accuracy can be improved.

[0055] According to the measurement of the induced voltage during the trial operation, by performing an operation pattern that cannot occur during normal product operation, the induced voltage can be measured with high accuracy. Thereby, the torque constant kT for each product can be estimated with high accuracy.

[0056] (2) After the product stops operating In this case, the induced voltage is measured after the output of the inverter 20 becomes off until the coasting rotation ends.

[0057] The torque constant kT calculated based on the measured induced voltage may be recorded in a storage medium, for example, an EEPROM, and read out during the next operation of the product.

[0058] Thereby, even after the product is installed, the torque constant kT can be continuously updated. That is, the torque constant kT can be updated at timings other than the trial operation. Therefore, even when the ambient temperature of the product changes, the torque constant kT under the changed ambient temperature can be estimated.

[0059] <Second Estimation Method> The second estimation method is a method of directly measuring the torque of the permanent magnet synchronous motor 11 by a torque measurement element and calculating the torque constant kT. As the torque measurement element, a strain gauge, a magnetostrictive element, or the like can be used.

[0060] For example, in a low rotation speed region where the induced voltage is small, the torque constant kT may be calculated by the second estimation method, and in a high rotation speed region where it is difficult to measure the torque by the torque measurement element, the torque constant kT may be estimated by the first estimation method. Thereby, even in a low rotation speed region where the measurement accuracy of the induced voltage is low, the torque constant kT can be estimated with high accuracy.

[0061] <The Third Estimation Method> The third estimation method is a method of measuring the induced voltage of the permanent magnet synchronous motor 11 using a sub-coil and estimating the torque constant kT from the measured induced voltage.

[0062] As described above, in the first estimation method, the induced voltage cannot be measured when the AC voltage is output from the inverter 20. On the other hand, since the sub-coil generates an induced voltage due to the magnetic flux linkage to which the output voltage of the inverter 20 is not applied, the induced voltage can always be measured.

[0063] Thus, according to the third estimation method, the induced voltage can be measured and the torque constant kT can be estimated even when the output from the inverter 20 is applied to the permanent magnet synchronous motor 11 or when the output of the inverter 20 is turned off and the permanent magnet synchronous motor 11 is coasting.

[0064] Also, the constant estimation unit 32 converts the induced voltage into a magnetic flux density and inputs the converted magnetic flux density to the torque calculation unit 35.

[0065] FIG. 5 is a flowchart showing the correction process of the constant output map by the inverter control device 30 of FIG. 2. When the correction process is started, the inverter control device 30 estimates the torque constant kT in step S100.

[0066] Subsequently, in step S200, the inverter control device 30 compares the torque constant kT with a reference constant. After that, in step S300, the inverter control device 30 corrects a constant output map based on the comparison result.

[0067] FIG. 6 is a flowchart showing a first estimation method of the torque constant kT by the inverter control device 30 of FIG. 2.

[0068] In step S111, the inverter control device 30 drives the permanent magnet synchronous motor 11 to a set rotational speed. Subsequently, in step S112, the inverter control device 30 stops the output of the inverter 20. As a result, the permanent magnet synchronous motor 11 enters a coasting state.

[0069] After that, in step S113, the inverter control device 30 measures the induced voltage. Then, in step S114, the inverter control device 30 estimates the torque constant kT. Also, in step S115, the inverter control device 30 converts the induced voltage into a magnetic flux density.

[0070] FIG. 7 is a flowchart showing a second estimation method of the torque constant kT by the inverter control device 30 of FIG. 2. In step S121, the inverter control device 30 measures the torque of the permanent magnet synchronous motor 11 using a torque measurement element. Subsequently, in step S122, the inverter control device 30 estimates the torque constant kT. Also, in step S123, the inverter control device 30 calculates the magnetic flux density from the torque constant kT.

[0071] FIG. 8 is a flowchart showing a third estimation method of the torque constant kT by the inverter control device 30 of FIG. 2. In step S131, the inverter control device 30 measures the induced voltage in the sub-coil. Subsequently, in step S132, the inverter control device 30 estimates the torque constant kT. Also, in step S133, the inverter control device 30 converts the induced voltage into a magnetic flux density.

[0072] FIG. 9 is a flowchart showing a method for adjusting the output of the inverter 20 by the inverter control device 30 of FIG. 2. In step S401, the inverter control device 30 compares the current generated torque with the target torque. Specifically, the inverter control device 30 determines whether the value obtained by subtracting the current generated torque value from the target torque value is greater than 0.

[0073] When the value obtained by subtracting the current generated torque value from the target torque value is greater than 0, that is, when the current generated torque is smaller than the target torque, the inverter control device 30 increases the output of the inverter 20 in step S402.

[0074] Also, when the value obtained by subtracting the current generated torque value from the target torque value is 0 or less, the inverter control device 30 decreases the output of the inverter 20 in step S403. When the value obtained by subtracting the current generated torque value from the target torque value is 0, the amount of decrease in the output of the inverter 20 is 0.

[0075] In such an inverter control device 30 and a blower using the same, the individual constant, which is a constant related to the characteristics of each permanent magnet synchronous motor 11, is estimated by the constant estimation unit 32. Then, the individual constant is compared with the reference constant by the correction unit 33, and the constant output map is corrected based on the comparison result.

[0076] Therefore, the variation in the output of the permanent magnet synchronous motor 11 controlled by the inverter 20 can be more reliably suppressed. As a result, the variation in the air volume during the constant air volume operation of the blower can be sufficiently suppressed.

[0077] Also, the constant estimation unit 32 measures the induced voltage of the permanent magnet synchronous motor 11, and estimates the torque constant kT as an individual constant from the measured induced voltage. Therefore, the torque constant kT can be estimated more accurately.

[0078] Further, the constant estimation unit 32 measures the induced voltage of the permanent magnet synchronous motor 11 in a state where the output of the inverter 20 is in the off state and the permanent magnet synchronous motor 11 is coasting. Therefore, the induced voltage of the permanent magnet synchronous motor 11 can be measured with a simple configuration.

[0079] Further, the constant estimation unit 32 measures the induced voltage due to the magnetic flux linkage of the sub-coil. Therefore, the induced voltage of the permanent magnet synchronous motor 11 can always be measured.

[0080] Further, the constant estimation unit 32 directly measures the torque of the permanent magnet synchronous motor 11 by the torque measurement element, and calculates the torque constant kT as an individual constant. Therefore, the torque constant kT can be estimated with higher accuracy.

[0081] Note that the permanent magnet synchronous motor 11 may be an embedded permanent magnet synchronous motor. In the case of an embedded permanent magnet synchronous motor, correction is required in the calculation formula of the torque constant kT in the torque calculation unit 35. However, if the torque constant kT is obtained as the proportionality constant between the torque T and the torque current iq, the correction method is not limited.

[0082] Further, the individual constant may be an electromotive force constant.

[0083] Further, the fan 13 is not limited to a sirocco fan.

[0084] Further, the device provided with the permanent magnet synchronous motor 11 is not limited to a blower.

[0085] Further, each function of the inverter control device 30 of Embodiment 1 is realized by a processing circuit. FIG. 10 is a configuration diagram showing a first example of a processing circuit that realizes each function of the inverter control device 30 of Embodiment 1. The processing circuit 100 of the first example is dedicated hardware.

[0086] Further, the processing circuit 100 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. Also, each function of the inverter control device 30 may be realized by an individual processing circuit 100, or each function may be realized collectively by the processing circuit 100.

[0087] Also, FIG. 11 is a configuration diagram showing a second example of a processing circuit that realizes each function of the inverter control device 30 according to Embodiment 1. The processing circuit 200 of the second example includes a processor 201 and a memory 202.

[0088] As the processor 201, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a microprocessor, a microcontroller, or a DSP (Digital Signal Processor) is used.

[0089] In the processing circuit 200, each function of the inverter control device 30 is realized by software, firmware, or a combination of software and firmware. The software and firmware are described as a program and stored in the memory 202. The processor 201 reads and executes the program stored in the memory 202 to realize each function.

[0090] The program stored in the memory 202 can also be said to cause the computer to execute the procedures or methods of each part described above. Here, the memory 202 is, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable and Programmable Read Only Memory), etc. Also, a magnetic disk, flexible disk, optical disk, compact disk, mini disk, DVD, etc. also correspond to the memory 202.

[0091] Regarding the functions of each part described above, some may be realized by dedicated hardware, and some may be realized by software or firmware.

[0092] In this way, the processing circuit can realize the functions of each part described above by hardware, software, firmware, or a combination thereof.

Explanation of Signs

[0093] 11 Permanent magnet synchronous motor, 20 Inverter, 30 Inverter control device, 31 Control device main body, 32 Constant estimation unit, 33 Correction unit.

Claims

1. A control device main body that controls an inverter connected to the permanent magnet synchronous motor based on constant output information, which is information indicating the relationship between the rotational speed and the torque current when the permanent magnet synchronous motor is operated at a constant output, the generated torque of the permanent magnet synchronous motor, and the rotational speed of the permanent magnet synchronous motor. A constant estimation unit that estimates an individual constant, which is a constant related to the characteristics of each of the permanent magnet synchronous motors that varies due to at least one of manufacturing errors and usage environments, and A correction unit that compares the individual constant estimated by the constant estimation unit with a reference constant and corrects the constant output information based on the comparison result. An inverter control device comprising the above.

2. The inverter control device according to claim 1, wherein the constant estimation unit measures the induced voltage of the permanent magnet synchronous motor and estimates the individual constant from the measured induced voltage.

3. The inverter control device according to claim 2, wherein the constant estimation unit measures the induced voltage of the permanent magnet synchronous motor in a state where the output of the inverter is off and the permanent magnet synchronous motor is coasting.

4. The inverter control device according to claim 2, wherein the constant estimation unit measures the induced voltage due to the magnetic flux linkage of the sub-coil to which the output voltage of the inverter is not applied.

5. The inverter control device according to claim 1, wherein the constant estimation unit directly measures the torque of the permanent magnet synchronous motor by a torque measurement element and calculates a torque constant as the individual constant.

6. A blower comprising the inverter control device according to any one of claims 1 to 5. ​

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