Driving device and driving method

Abstract

The drive device (100) rotates an electric motor (2) based on a rotation speed target value, and includes a converter (3) that converts a voltage from an AC power source (1) into DC, an inverter (5) that converts the DC converted by the converter into AC and supplies the AC to the electric motor (2), an instantaneous power calculation unit (8) that calculates instantaneous power for each calculation period from a voltage command to the inverter (5) and a current supplied from the inverter (5) to the electric motor (2), and a power consumption calculation unit (10) that calculates power consumption corresponding to the multiple instantaneous powers calculated by the instantaneous power calculation unit (8), and an inverter circuit control unit (200) that reduces the rotation speed of the drive device (100) below the rotation speed target value when the power consumption calculated by the power consumption calculation unit (10) exceeds a preset power consumption threshold value. This makes it possible to increase robustness against sudden load fluctuations.

Description

[Technical field]

[0001] The present disclosure relates to a driving device and a driving method. [Background technology]

[0002] The drive device is connected between a power source and an electric motor, and generates an AC voltage from the power source to drive the electric motor. The drive device has an inverter circuit and an inverter circuit control unit, and the inverter circuit control unit controls the inverter circuit to control the electric motor.

[0003] For example, Patent Document 1 discloses a drive device that has a converter, inverter circuit, inverter circuit control unit, etc., in order to suppress the amount of heat generated by the motor, calculates an actual power value based on the voltage of a capacitor connected in parallel with the converter and the measured value of the current supplied by the inverter to the motor, and reduces the rotation speed when the calculated actual power value exceeds a threshold value.

[0004] Here, in a drive device intended to control the rotation speed of an electric motor such as a fan or pump at a constant speed, it is important to be able to operate the device while suppressing changes in the rotation speed as much as possible, even when a sudden load fluctuation occurs due to a disturbance such as the inclusion of foreign matter in the fan or pump. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 188884 Summary of the Invention [Problem to be solved by the invention]

[0006] However, since the actual power fluctuates significantly when a sudden load change occurs, in Patent Document 1, the rotation speed is changed every time a sudden load change occurs, which may cause the operation of the device itself to become unstable.

[0007] The present disclosure has been made in consideration of the above problems, and aims to provide a drive device that is highly robust against sudden load fluctuations in a drive device designed to control the rotation speed of an electric motor at a constant speed. [Means for solving the problem]

[0008] The drive device according to this disclosure is a drive device that rotates an electric motor based on a rotational speed target value, and has a converter that converts voltage from an AC power source into DC, an inverter that converts the DC converted by the converter into AC and supplies it to the electric motor, an instantaneous power calculation unit that calculates instantaneous power for each calculation period from a voltage command to the inverter and a current supplied from the inverter to the electric motor, and a power consumption calculation unit that calculates power consumption corresponding to the multiple instantaneous powers calculated by the instantaneous power calculation unit, and an inverter circuit control unit that reduces the rotational speed of the drive device below the rotational speed target value if the power consumption calculated by the power consumption calculation unit exceeds a predetermined power consumption threshold. Effect of the Invention

[0009] According to the present disclosure, high robustness can be maintained even against sudden load changes. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic configuration diagram showing a drive device according to a first embodiment. [Diagram 2] 4 is a diagram showing the relationship between instantaneous power, a calculation period, unit period power consumption, a power consumption calculation value, and a power consumption upper limit value when the calculation period is a unit period in the driving device according to the first embodiment. FIG. [Diagram 3] FIG. 2 is a block diagram of a corrected rotational speed calculation unit according to the first embodiment. [Figure 4] 5 is a flowchart showing the operation of a corrected rotational speed calculation unit according to the first embodiment. [Diagram 5] FIG. 2 is a block diagram of a Δω calculation unit according to the first embodiment. [Figure 6]4 is a diagram showing a current flowing through the electric motor when the rotation speed of the drive device according to the first embodiment is decelerated from ω1 to ω2. [Figure 7] FIG. 11 is a schematic configuration diagram showing a drive device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same reference numerals denote the same or corresponding parts.

[0012] Embodiment 1 1 is a schematic configuration diagram showing a drive device 100 for an electric motor 2 according to a first embodiment. The drive device 100 is provided between an AC power source 1 and an electric motor 2, and has a converter circuit unit 3, a smoothing capacitor 4, an inverter circuit unit 5, a current detection unit 6, and an inverter circuit control unit 200. The converter circuit unit 3, the smoothing capacitor 4, the inverter circuit unit 5, and the current detection unit 6 are provided in parallel between the AC power source 1 and the electric motor 2.

[0013] The driving device 100 rotates the electric motor 2 with the rotation speed target value ω1* as a target. The driving device 100 rotates the electric motor 2 based on the rotational speed target value ω1*.

[0014] The converter circuit unit 3 converts the voltage from the AC power source 1 into DC and smooths it with a smoothing capacitor 4. The inverter circuit unit 5 converts the smoothed DC voltage into a three-phase voltage in accordance with a gate signal from an inverter circuit control unit 200 and supplies the converted three-phase voltage to the electric motor 2. The inverter circuit unit 5 is an inverter. The converter circuit unit is a converter. The inverter converts the DC converted by the converter into AC and supplies it to the electric motor 2.

[0015] The current detection unit 6 detects three-phase currents (Iu, Iv, Iw) from the converted three-phase voltages, and outputs them to the inverter circuit control unit 200.

[0016] The inverter circuit control unit 200 has a current coordinate conversion unit 7, an instantaneous power calculation unit 8, a power consumption calculation unit 10, a memory 11, a corrected rotational speed calculation unit 12, an integral calculation unit 13, a voltage command calculation unit 14, a voltage coordinate conversion unit 15, and a PWM signal generation unit 16. The instantaneous power calculation unit 8, the power consumption calculation unit 10, the memory 11, and the corrected rotational speed calculation unit 12 configure a power consumption suppression calculation unit 300.

[0017] In the inverter circuit control unit 200, the current coordinate conversion unit 7 converts the three-phase currents (Iu, Iv, Iw) from the current detection unit 6 into two-phase currents (Id 、 Iq) is converted into the coordinate system. Here, the phase θ used in the coordinate conversion is the phase calculated by the integration calculation unit 13, which will be described later.

[0018] The instantaneous power calculation unit 8 converts the two-phase current (Id 、 From the two-phase voltage commands (Vd*, Vq*) calculated by the voltage command calculation unit 14 described later, the instantaneous power P[n] is calculated according to Equation 1. Here, P[n] is the power consumption in the nth calculation cycle. The instantaneous power is also the power consumption of the driving device 100 at the calculated timing. The instantaneous power calculation unit calculates the instantaneous power for each calculation cycle from the voltage command to the inverter and the current supplied from the inverter to the electric motor 2.

[0019]

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[0020] The power consumption calculation unit 10 calculates a power consumption calculation value West[n] for multiple calculation periods (assumed to be n0) from the instantaneous power P[n] calculated by the instantaneous power calculation unit 8 in accordance with Equation 2. The power consumption calculation value West[n] is the amount of power consumption. Here, T0 is the calculation period and is set in advance in the memory 11. Furthermore, W[n] is the unit period power consumption of the driving device 100 for one period for the nth time for which the instantaneous power was calculated.

[0021]

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[0022] The power consumption calculation unit 10 calculates the unit period power consumption W[n] by multiplying the instantaneous power P[n] by the calculation period T0 obtained from the memory 11. The power consumption calculation unit 10 stores the calculated unit period power consumption W[n] for the nth calculation period in the memory 11. The power consumption calculation unit 10 obtains the unit period power consumptions W[n] to W[n-(n0-1)] from the memory 11, and calculates the power consumption calculation value West[n] for the latest multiple times (n0 times). In other words, the power consumption calculation unit 10 calculates the power consumption corresponding to the multiple instantaneous powers calculated by the instantaneous power calculation unit 8.

[0023] Here, the method of calculating the power consumption calculation value West[n] by the power consumption calculation unit 10 is not limited to this. For example, the power consumption calculation value West[n] may be stored in the memory 11 in addition to the unit period power consumption W[n], and the power consumption calculation value West[n] may be calculated by subtracting the unit period power consumption W[n-(n0-1)] of the oldest period out of n0 times from the power consumption calculation value West[n-1] of the previous period, and adding the unit period power consumption W[n] of the current period.

[0024] The corrected rotation speed calculation unit 12 calculates a rotation speed correction amount Δω from the power consumption excess amount ΔW[n] expressed by Equation 3. Here, Wmax is a power consumption upper limit value, and is set in advance in the memory 11. The power consumption upper limit value is a power consumption threshold value.

[0025]

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[0026] 2 shows the relationship between instantaneous power P[n], unit period power consumption W[n], power consumption calculation value West[n], and power consumption upper limit Wmax when the calculation period is the unit period. The power consumption calculation value West[n] is the sum of the unit period power consumption W[n] multiple times.

[0027] 1, a specific method for calculating the rotation speed correction amount Δω in the corrected rotation speed calculation unit 12 will be described later. The corrected rotation speed calculation unit 12 calculates a corrected rotation speed command ω2* according to Equation 4.

[0028]

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[0029] The integral calculation unit 13 calculates the phase θ by integrating the corrected rotation speed command ω2*. The voltage command calculation unit 14 obtains two-phase voltage commands (Vd*, Vq*) on the rotating coordinate system according to the corrected rotation speed command ω2*.

[0030] The voltage coordinate conversion unit 15 converts the two-phase voltage commands (Vd*, Vq*) calculated by the voltage command calculation unit 14 into three-phase voltage commands (Vu*, Vv*, Vw*). Here, the phase used in the coordinate conversion is the phase θ calculated by the integral calculation unit 13.

[0031] The PWM signal generating unit 16 outputs a gate signal to the inverter circuit unit 5 based on the three-phase voltage commands (Vu*, Vv*, Vw*) calculated by the voltage coordinate conversion unit 15. Here, the gate signal is a signal that has been subjected to pulse width modulation.

[0032] That is, when the power consumption calculated by the power consumption calculation unit 10 exceeds a preset power consumption threshold, the inverter circuit control unit 200 reduces the rotation speed of the drive device 100 below the rotation speed target value ω1*.

[0033] 3 is a block diagram of the corrected rotational speed calculation unit 12. The corrected rotational speed calculation unit 12 includes a comparison unit 1201, a rotational speed correction flag setting unit 1202, a Δω calculation unit 1203, and a previous value storage unit 1204.

[0034] A comparison unit 1201 compares the power consumption excess amount ΔW[n] with 0. A rotation speed correction flag setting unit 1202 sets a rotation speed correction flag for a current calculation cycle according to the power consumption excess amount ΔW[n], the rotation speed correction flag for the previous calculation cycle, and the rotation speed correction amount Δω for the previous calculation cycle. A Δω calculation unit 1203 calculates a rotation speed correction amount Δω according to the power consumption excess amount ΔW[n] and the rotation speed correction amount Δω for the previous cycle. A previous value storage unit 1204 stores the rotation speed correction amount Δω for the previous cycle and the rotation speed correction flag for the previous cycle.

[0035] 4 is a flow chart showing the operation of the corrected rotation speed calculation unit 12. The corrected rotation speed calculation unit 12 calculates the rotation speed correction amount Δω from the power consumption excess amount ΔW[n], the rotation speed correction amount Δω of the previous cycle, and the rotation speed correction flag of the previous cycle. In step ST1, the comparison unit 1201 judges whether the power consumption excess amount ΔW[n] is greater than 0. If it is greater than 0 (Yes in step ST1), the process proceeds to step ST2, where the rotation speed correction flag setting unit 1202 sets the rotation speed correction flag to 1 (ON). Next, the process proceeds to step ST3, where the Δω calculation unit 1203 calculates the rotation speed correction amount Δω as described below.

[0036] On the other hand, if the power consumption excess amount ΔW[n] is equal to or less than 0 (step ST1: No), the process proceeds to step ST4, where the rotation speed correction flag setting unit 1202 determines whether the rotation speed correction flag for the previous cycle is ON. If the rotation speed correction flag for the previous cycle is ON (step ST4: Yes), the process proceeds to step ST5. In step ST5, the rotation speed correction flag setting unit 1202 determines whether the rotation speed correction amount Δω for the previous cycle is not 0. If the rotation speed correction amount Δω for the previous cycle is not 0 (step ST5: Yes), the process proceeds to step ST6.

[0037] In step ST6, the rotation speed correction flag setting unit 1202 sets the rotation speed correction flag to 1 (ON). Next, the process proceeds to step ST7, where the Δω calculation unit 1203 calculates a rotation speed correction amount Δω as described later.

[0038] If it is determined in step ST4 that the rotation speed correction flag for the previous cycle is not 1 (ON) (No in step ST4), the process proceeds to step ST8. Also, if it is determined in step ST5 that the rotation speed correction amount Δω for the previous cycle is 0 (No in step ST5), the process proceeds to step ST8, where the rotation speed correction flag setting unit 1202 sets the rotation speed correction flag to 0 (OFF). Next, the process proceeds to step ST9, where the Δω calculation unit 1203 sets the rotation speed correction amount Δω to 0 and ends the process.

[0039] The rotation speed correction amount Δω is a correction amount for reducing the rotation speed at which the inverter circuit control unit 200 drives the inverter circuit 200 below the rotation speed target value ω1*. That is, even if the power consumption calculated by the power consumption calculation unit 10 does not exceed a preset power consumption threshold, if the inverter circuit control unit 200 reduced the rotation speed of the drive device 100 below the rotation speed target value ω1* in the previous calculation cycle, the inverter circuit control unit 200 reduces the rotation speed of the drive device 100 below the rotation speed target value ω1* in the current calculation cycle.

[0040] Fig. 5 is a block diagram of the Δω calculation unit 1203 corresponding to step ST3 or step ST7 in Fig. 4. The rotation speed correction amount Δω is calculated by performing PI control from the power consumption excess amount ΔW[n], which is the difference between the power consumption calculation value West[n], the power consumption excess amount ΔW[n], and the power consumption upper limit value Wmax.

[0041] 6 is a diagram showing the current flowing through the electric motor 2 when the rotation speed is decelerated from ω1 to ω2. In the case of the electric motor 2 having a reduced torque load characteristic, the output current of the driving device 100 is proportional to the square of the rotation speed. Therefore, especially in the high speed range, even if the rotation speed correction amount Δω is small, the output current of the driving device 100 can be significantly reduced, and the driving device 100 can achieve a high energy saving effect.

[0042] As described above, according to this embodiment, the instantaneous power calculation unit 8 calculates the power consumption calculation value West[n] for a certain section using the current output from the inverter circuit unit 5 and the voltage command input to the inverter circuit unit 5, and reduces the rotation speed when the power consumption calculation value West[n] exceeds the power consumption upper limit value Wmax. The actual voltage of the output of the inverter circuit unit 5 fluctuates significantly when a sudden load change occurs due to a disturbance such as the inclusion of a foreign object. In this embodiment, since the voltage command is used instead of the actual voltage of the output of the inverter circuit unit 5, it is possible to realize a drive device 100 that is not affected by sudden load changes, as compared to a case in which the power consumption calculation value is calculated using the actual voltage.

[0043] Furthermore, in this embodiment, the rotation speed is corrected when the power consumption calculation value West[n] exceeds the power consumption upper limit Wmax, and even if the power consumption calculation value West[n] does not exceed the power consumption upper limit Wmax, the rotation speed correction amount Δω is corrected if the rotation speed correction amount Δω for the previous cycle is not 0. This makes it possible to further improve the robustness of the output of the drive device 100 compared to the case where the rotation speed is corrected regardless of the rotation speed correction amount Δω for the previous cycle when the power consumption calculation value West[n] does not exceed the power consumption upper limit Wmax.

[0044] Embodiment 2 FIG. 7 is a schematic configuration diagram showing a driving device 100 according to a second embodiment. Explanation of the same parts as those in the first embodiment will be omitted. The driving device 100 according to the second embodiment will be explained with reference to FIG. 7. The second embodiment differs from the first embodiment in that an average power calculation unit 9 is added. Other aspects are the same as those in the first embodiment.

[0045] In order to calculate the power consumption for a certain interval, in the first embodiment, the unit period power consumption (instantaneous power P[n]×calculation period T0) is added up for the certain interval. In the second embodiment, the average value of the instantaneous power P[n] for the certain interval is calculated, and the average value is multiplied by the duration of the certain interval to calculate the power consumption calculation value West[n] for the certain interval.

[0046] The average power calculation unit 9 acquires the instantaneous power P[n] calculated by the instantaneous power calculation unit 8, and the instantaneous powers before the previous cycle (P[n-1] to P[n-(n0-1)]) acquired from the memory. The average power calculation unit 9 calculates the average power Pave[n] which is the average value of the instantaneous powers for the most recent n0 calculation cycles. The average power calculation unit 9 calculates the average value of the instantaneous powers for multiple calculation cycles.

[0047] The power consumption calculation unit 10 acquires the time length Tdef for n0 calculation cycles and the average power Pave[n] output by the average power calculation unit 9 from the memory 11. The power consumption calculation unit 10 calculates the power consumption calculation value West by multiplying the average power Pave[n] by the time length Tdef. The power consumption calculation unit calculates the power consumption using the average value of the instantaneous power. The subsequent processing is the same as in the first embodiment.

[0048] Thus, according to this embodiment, similarly to the first embodiment, the instantaneous power calculation unit 8 calculates the power consumption for a certain section using the current that is the output of the inverter circuit unit 5 and the voltage command that is the input to the inverter circuit unit 5. Even in this case, the same effect as in the first embodiment can be achieved.

[0049] The configurations shown in the above embodiments are examples of the contents of the present disclosure, and may be combined with other known technologies. It is also possible to combine the above embodiments, or to omit or modify parts of the configurations without departing from the gist of the present disclosure. [Explanation of symbols]

[0050] Reference Signs List 1 AC power supply, 2 electric motor, 3 converter circuit section, 5 inverter circuit section, 6 current detection section, 7 current coordinate conversion section, 8 instantaneous power calculation section, 9 average power calculation section, 10 power consumption calculation section, 11 memory, 12 corrected rotation speed calculation section, 13 integral calculation section, 14 voltage command calculation section, 15 voltage coordinate conversion section, 16 PWM signal generation section, 100 drive device, 200 inverter circuit control section.

Claims

1. A drive device that rotates an electric motor based on a rotational speed target value, a converter that converts voltage from an AC power source into DC; an inverter that converts the DC converted by the converter into AC and supplies the AC to the electric motor; an inverter circuit control unit including an instantaneous power calculation unit that calculates instantaneous power for each calculation period from a voltage command to the inverter and a current supplied from the inverter to the electric motor, and a power consumption calculation unit that calculates power consumption corresponding to the plurality of instantaneous powers calculated by the instantaneous power calculation unit, and that reduces the rotation speed of the drive device below the rotation speed target value when the power consumption calculated by the power consumption calculation unit exceeds a preset power consumption threshold; and Even if the power consumption calculated by the power consumption calculation unit does not exceed a preset power consumption threshold, if the rotation speed of the drive device was reduced below the rotation speed target value in the previous calculation cycle, the inverter circuit control unit reduces the rotation speed of the drive device below the rotation speed target value in the current calculation cycle. A drive device characterized by:

2. the inverter circuit control unit further includes an average power calculation unit, the average power calculation unit calculates an average value of the instantaneous power for a plurality of times; The power consumption calculation unit calculates the power consumption using the average value of the instantaneous power.

2. The drive device according to claim 1.

3. A method for driving a drive device that rotates an electric motor based on a rotational speed target value, comprising: converting voltage from an AC power source into DC; converting the converted DC into AC and supplying it to the electric motor; calculating instantaneous power for each calculation period from a voltage command to an inverter and a current supplied from the inverter to the electric motor; calculating power consumption amounts corresponding to the plurality of instantaneous powers; If the power consumption exceeds a predetermined power consumption threshold, reducing the rotation speed of the drive device below the rotation speed target value; and Even if the calculated power consumption does not exceed the power consumption threshold, if the rotation speed of the drive device was reduced below the rotation speed target value in the previous calculation cycle, the rotation speed of the drive device is reduced below the rotation speed target value in the current calculation cycle. A driving method characterized by the above.

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