Driving device, driving method

Abstract

A drive device (100) rotates an electric motor (2) based on a rotational speed target value, and includes a converter (3) that converts a voltage from an alternating-current power supply (1) into direct current, an inverter (5) that converts the direct current converted by the converter into alternating current to supply to the electric motor (2), and an inverter circuit control section (200) that includes a momentary power calculation section (8) that calculates momentary power for each calculation period based on 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 section (10) that calculates power consumption corresponding to a plurality of momentary powers calculated by the momentary power calculation section (8), and lowers the rotational speed of the drive device (100) below the rotational speed target value in a case where the power consumption calculated by the power consumption calculation section (10) exceeds a preset power consumption threshold value. Thus, it is possible to improve robustness against a sharp load variation.

Description

Technical Field

[0001] This invention relates to a driving device and a driving method. Background Technology

[0002] The drive unit is connected between the power supply and the motor, and drives the motor by generating an AC voltage from the power supply. The drive unit has an inverter circuit and an inverter circuit control unit, which controls the motor by controlling the inverter circuit.

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

[0004] In drive systems designed to control the rotational speed of motors such as fans or pumps at a constant speed, it is important to be able to suppress changes in rotational speed as much as possible, even when external disturbances such as the introduction of foreign objects cause drastic load changes in the fan or pump.

[0005] Patent Document 1: International Publication No. 2020 / 188884 Summary of the Invention

[0006] However, the actual power will vary greatly when there is a sharp load change. Therefore, in Patent Document 1, the rotation speed will change with each sharp load change, which raises concerns that the operation of the device itself will become unstable.

[0007] The present invention was made in view of the above-mentioned problems, and its object is to obtain a drive device that is highly robust to rapid load changes in a drive device for controlling the rotation speed of an electric motor at a constant speed.

[0008] The drive device of the present invention rotates an electric motor based on a target speed value. The drive device includes: a converter that converts voltage from an AC power source into DC; an inverter that converts the DC converted by the converter back into AC and supplies it to the electric motor; and an inverter circuit control unit that includes an instantaneous power calculation unit and a power consumption calculation unit. The instantaneous power calculation unit calculates instantaneous power for each calculation cycle based on a voltage command to the inverter and the current supplied from the inverter to the electric motor. The power consumption calculation unit calculates the power consumption corresponding to the multiple instantaneous powers calculated by the instantaneous power calculation unit. If the power consumption calculated by the power consumption calculation unit exceeds a preset power consumption threshold, the inverter circuit control unit lowers the speed of the drive device below the target speed value.

[0009] The effects of the invention

[0010] According to the present invention, high robustness can also be ensured in the face of rapid load changes. Attached Figure Description

[0011] Figure 1 This is a schematic structural diagram of the drive device involved in Embodiment 1.

[0012] Figure 2 This is a graph showing the relationship between instantaneous power, calculation period, power consumption per unit period, calculated power consumption value, and upper limit value of power consumption in the drive device according to Embodiment 1 when the calculation period is a unit period.

[0013] Figure 3 This is a block diagram of the speed correction calculation unit according to Embodiment 1.

[0014] Figure 4 This is a flowchart illustrating the operation of the speed correction calculation unit according to Embodiment 1.

[0015] Figure 5 This is a block diagram of the Δω calculation unit according to Embodiment 1.

[0016] Figure 6 This is a diagram showing the current flowing through the motor when the rotational speed of the drive device according to Embodiment 1 is reduced from ω1 to ω2.

[0017] Figure 7 This is a schematic structural diagram of the drive device involved in Embodiment 2. Detailed Implementation

[0018] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. The same reference numerals in the drawings denote the same or equivalent parts.

[0019] Implementation Method 1

[0020] Figure 1 This is a schematic structural diagram showing the drive device 100 of the electric motor 2 according to Embodiment 1. The drive device 100 is disposed between the AC power supply 1 and the electric motor 2, and includes a converter circuit section 3, a smoothing capacitor 4, an inverter circuit section 5, a current detection section 6, and an inverter circuit control section 200. The converter circuit section 3, the smoothing capacitor 4, the inverter circuit section 5, and the current detection section 6 are disposed in parallel between the AC power supply 1 and the electric motor 2.

[0021] Drive unit 100 causes motor 2 to reach the target speed ω1 Rotate for the goal.

[0022] That is, the drive unit 100 is based on the target rotational speed value ω1 Make motor 2 rotate.

[0023] The converter circuit section 3 converts the voltage from the AC power supply 1 into DC, smoothing it using the smoothing capacitor 4. The inverter circuit section 5 converts the smoothed DC voltage into a three-phase voltage according to the gate signal from the inverter circuit control section 200, and supplies the converted three-phase voltage to the motor 2. The inverter circuit section 5 is an inverter. The converter circuit section is a converter. The inverter converts the DC voltage converted by the converter into AC voltage and supplies it to the motor 2.

[0024] The current detection unit 6 detects the three-phase currents (Iu, Iv, Iw) based on the converted three-phase voltage and outputs the results to the inverter circuit control unit 200.

[0025] The inverter circuit control unit 200 includes a current coordinate transformation unit 7, an instantaneous power calculation unit 8, a power consumption calculation unit 10, a memory 11, a speed correction calculation unit 12, an integral calculation unit 13, a voltage command calculation unit 14, a voltage coordinate transformation 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 speed correction calculation unit 12 constitute the power consumption suppression calculation unit 300.

[0026] In the inverter circuit control unit 200, the current coordinate transformation unit 7 transforms the coordinates of the three-phase currents (Iu, Iv, Iw) from the current detection unit 6 into two-phase currents (Id, Iq) in a rotating coordinate system. Here, the phase θ used for the coordinate transformation is the phase calculated by the integration calculation unit 13, which will be described later.

[0027] The instantaneous power calculation unit 8 calculates the two-phase currents (Id, Iq) obtained by the current coordinate transformation unit 7 and the two-phase voltage command (Vd) calculated by the voltage command calculation unit 14 (described later). Vq The instantaneous power P[n] is calculated according to mathematical formula 1. Here, P[n] is the power consumed in the nth calculation cycle. In addition, the instantaneous power is the power consumed by the timing drive device 100. The instantaneous power calculation unit calculates the instantaneous power for each calculation cycle based on the voltage command to the inverter and the current supplied from the inverter to the motor 2.

[0028]

Mathematical Formula 1

[0029] The power consumption calculation unit 10 calculates the power consumption calculation value West[n] in multiple (let's say n0) calculation cycles according to mathematical formula 2, based on the instantaneous power P[n] calculated by the instantaneous power calculation unit 8. The power consumption calculation value West[n] is the power consumption. Here, T0 is the calculation cycle, which is preset in the memory 11. In addition, W[n] is the power consumption per unit cycle of the drive device 100 in one cycle of the nth calculation of the instantaneous power.

[0030]

Mathematical Formula 2

[0031] The power consumption calculation unit 10 calculates the unit cycle power consumption W[n] by multiplying the calculation cycle T0 obtained from the memory 11 with the instantaneous power P[n]. The power consumption calculation unit 10 stores the calculated unit cycle power consumption W[n] for the nth calculation cycle in the memory 11. The power consumption calculation unit 10 obtains the unit cycle power consumption from W[n] to W[n-(n0-1)] from the memory 11 and calculates the latest multiple (n0) power consumption calculation values ​​West[n]. That is, the power consumption calculation unit 10 calculates the power consumption corresponding to the multiple instantaneous powers calculated by the instantaneous power calculation unit 8.

[0032] Here, the method by which the power consumption calculation unit 10 calculates the power consumption calculation value West[n] is not limited to this. For example, the memory 11 may not only store the power consumption W[n] per unit cycle, but also the power consumption calculation value West[n]. The power consumption calculation value West[n] is calculated by subtracting the power consumption W[n-(n0-1)] of the earliest of the n0 cycles from the power consumption calculation value West[n-1] of the previous cycle, and then adding it to the power consumption W[n] of the current cycle.

[0033] The speed correction calculation unit 12 calculates the speed correction amount Δω based on the power consumption excess ΔW[n] expressed by mathematical formula 3. Here, Wmax is the upper limit of power consumption, which is preset in memory 11. The upper limit of power consumption is a power consumption threshold.

[0034]

Mathematical Expression 3

[0035] Figure 2 This is a graph showing the relationship between instantaneous power P[n], unit-cycle power consumption W[n], power consumption calculation value West[n], and power consumption upper limit Wmax when the calculation period is a unit cycle. The value obtained by adding the unit-cycle power consumption W[n] multiple times is called the power consumption calculation value West[n].

[0036] return Figure 1The specific calculation method for the speed correction amount Δω in the speed correction calculation unit 12 will be described later. The speed correction calculation unit 12 calculates the corrected speed command ω2 according to mathematical formula 4. .

[0037]

Mathematical Expression 4

[0038] The integral calculation unit 13 processes the corrected speed command ω2 Integration is performed to calculate the phase θ. The voltage command arithmetic unit 14 calculates the phase θ according to the corrected speed command ω2. Calculate the two-phase voltage command (Vd) on the rotating coordinate system. Vq ).

[0039] The voltage coordinate transformation unit 15 converts the two-phase voltage command (Vd) calculated by the voltage command calculation unit 14 into a voltage coordinate transformation unit. Vq Coordinate transformation into three-phase voltage command (Vu) Vv Vw Here, the phase used for coordinate transformation is the phase θ calculated by the integration unit 13.

[0040] The PWM signal generation unit 16 is based on the three-phase voltage command (Vu) calculated by the voltage coordinate transformation unit 15. Vv Vw The gate signal is output to the inverter circuit section 5. Here, the gate signal is a signal after pulse width modulation.

[0041] 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 lowers the rotational speed of the drive unit 100 below the target rotational speed value ω1. .

[0042] Figure 3 This is a block diagram of the speed correction calculation unit 12. The speed correction calculation unit 12 includes a comparison unit 1201, a speed correction flag setting unit 1202, a Δω calculation unit 1203, and a previous value storage unit 1204.

[0043] The comparison unit 1201 compares the power consumption excess ΔW[n] with 0. The speed correction flag setting unit 1202 sets the speed correction flag for the current calculation cycle based on the power consumption excess ΔW[n], the speed correction flag of the previous calculation cycle, and the speed correction amount Δω of the previous calculation cycle. The Δω calculation unit 1203 calculates the speed correction amount Δω based on the power consumption excess ΔW[n] and the speed correction amount Δω of the previous cycle. The previous value storage unit 1204 stores the speed correction amount Δω of the previous cycle and the speed correction flag of the previous cycle.

[0044] Figure 4 This is a flowchart illustrating the operation of the speed correction calculation unit 12. The speed correction calculation unit 12 calculates the speed correction amount Δω based on the power consumption excess ΔW[n], the speed correction amount Δω from the previous cycle, and the speed correction flag from the previous cycle. In step ST1, the comparison unit 1201 determines whether the power consumption excess ΔW[n] is greater than 0. If it is greater than 0 (step ST1: Yes), the process proceeds to step ST2, where the speed correction flag setting unit 1202 sets the speed correction flag to 1 (ON). Next, the process proceeds to step ST3, where, as described later, the Δω calculation unit 1203 calculates the speed correction amount Δω.

[0045] On the other hand, if the power consumption exceeds ΔW[n] and is less than or equal to 0 (step ST1: No), proceed to step ST4, where the speed correction flag setting unit 1202 determines whether the speed correction flag of the previous cycle is ON. If the speed correction flag of the previous cycle is ON (step ST4: Yes), proceed to step ST5. In step ST5, the speed correction flag setting unit 1202 determines whether the speed correction amount Δω of the previous cycle is not 0. If the speed correction amount Δω of the previous cycle is not 0 (step ST5: Yes), proceed to step ST6.

[0046] In step ST6, the speed correction flag setting unit 1202 sets the speed correction flag to 1 (ON). Next, in step ST7, the Δω calculation unit 1203 calculates the speed correction amount Δω as described later.

[0047] If, in step ST4, it is determined that the speed correction flag for the previous cycle is not 1 (ON) (Step ST4: No), proceed to step ST8. Also, if, in step ST5, it is determined that the speed correction amount Δω for the previous cycle is 0 (Step ST5: No), proceed to step ST8 as well, and the speed correction flag setting unit 1202 sets the speed correction flag to 0 (OFF). Next, proceed to step ST9, where the Δω calculation unit 1203 sets the speed correction amount Δω to 0, and the process ends.

[0048] The speed correction amount Δω is used to ensure that the speed driven by the inverter circuit control unit 200 is lower than the target speed value ω1. The correction amount. That is, even if the power consumption calculated by the power consumption calculation unit 10 does not exceed the preset power consumption threshold, the inverter circuit control unit 200 will adjust the speed of the drive unit 100 if it was lower than the target speed value ω1 in the previous calculation cycle. Therefore, in this calculation cycle, the rotational speed of the drive unit 100 is also made lower than the target rotational speed value ω1. .

[0049] Figure 5 Is with Figure 4 The block diagram of the Δω calculation unit 1203 corresponding to step ST3 or step ST7. PI control is performed based on the difference between the calculated power consumption value West[n], the power consumption excess ΔW[n], and the power consumption upper limit value Wmax, i.e., the power consumption excess ΔW[n], to calculate the speed correction amount Δω.

[0050] Figure 6 This is a graph showing the current flowing through the motor 2 when the rotational speed is reduced from ω1 to ω2. In the case of the motor 2 with decreasing torque load characteristics, the output current of the drive unit 100 is proportional to the square of the rotational speed. Therefore, especially in the high-speed region, even if the speed correction amount Δω is small, the output current of the drive unit 100 can be significantly reduced, and the drive unit 100 can achieve high energy-saving effect.

[0051] Thus, according to this embodiment, in the instantaneous power calculation unit 8, the power consumption calculation value West[n] within a constant range is calculated using the current output from the inverter circuit unit 5 and the voltage command input to the inverter circuit unit 5. If the power consumption calculation value West[n] exceeds the upper limit of power consumption Wmax, the rotational speed is reduced. In the event of a sharp load change due to external interference such as foreign matter intrusion, the actual voltage output of the inverter circuit unit 5 fluctuates significantly. In this embodiment, a voltage command is used instead of the actual voltage output by the inverter circuit unit 5. Therefore, compared to calculating the power consumption calculation value using the actual voltage, a drive device 100 with high robustness unaffected by sharp load changes can be achieved.

[0052] Furthermore, in this embodiment, when the calculated power consumption value West[n] exceeds the upper limit of power consumption Wmax, the rotational speed is corrected. Even when the calculated power consumption value West[n] does not exceed the upper limit of power consumption Wmax, if the rotational speed correction amount Δω of the previous cycle is not 0, the rotational speed correction amount Δω is also corrected. Therefore, compared to the case where the rotational speed is corrected without relying on the rotational speed correction amount Δω of the previous cycle, when the calculated power consumption value West[n] does not exceed the upper limit of power consumption Wmax, the robustness of the drive device 100's output can be further improved.

[0053] Implementation Method 2

[0054] Figure 7 This is a schematic structural diagram showing the drive device 100 according to Embodiment 2. Descriptions of parts identical to those in Embodiment 1 are omitted. Based on Figure 7 The driving device 100 according to Embodiment 2 will be described. The difference from Embodiment 1 is that an average power calculation unit 9 is added. Otherwise, it is the same as Embodiment 1.

[0055] In order to calculate the power consumption over a constant interval, in Implementation 1, the power consumption per unit period (instantaneous power P[n] × calculation period T0) is accumulated over the constant interval. In Implementation 2, the power consumption value West[n] over the constant interval is calculated by multiplying the average value of the instantaneous power P[n] over the constant interval by the duration of the constant interval.

[0056] The average power calculation unit 9 acquires the instantaneous power P[n] calculated by the instantaneous power calculation unit 8 and the instantaneous power (P[n-1] to P[n-(n0-1)]) from the memory up to the previous cycle. The average power calculation unit 9 calculates the average power Pave[n], which is the average of the instantaneous power over the most recent n0 calculation cycles. The average power calculation unit 9 calculates the average of the instantaneous power over multiple cycles.

[0057] The power consumption calculation unit 10 retrieves the duration Tdef of n0 calculation cycles from the memory 11 and the average power Pave[n] output by the average power calculation unit 9. The power consumption calculation unit 10 calculates the power consumption value West by multiplying the average power Pave[n] by the duration 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 Embodiment 1.

[0058] Thus, according to this embodiment, similarly to Embodiment 1, the instantaneous power calculation unit 8 uses the current output from the inverter circuit unit 5 and the voltage command input to the inverter circuit unit 5 to calculate the power consumption within a constant range. In this case, the same effect as Embodiment 1 can also be achieved.

[0059] The structure shown in the above embodiments is an example of the content of the present invention. It can also be combined with other known technologies. The above embodiments can also be combined, and a part of the structure can be omitted or changed without departing from the spirit of the present invention.

[0060] Explanation of the label

[0061] 1 AC power supply, 2 Motor, 3 Converter circuit section, 5 Inverter circuit section, 6 Current detection section, 7 Current coordinate transformation section, 8 Instantaneous power calculation section, 9 Average power calculation section, 10 Power consumption calculation section, 11 Memory, 12 Speed ​​correction calculation section, 13 Integral calculation section, 14 Voltage command calculation section, 15 Voltage coordinate transformation 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 target rotational speed value. The drive unit has: A converter that transforms voltage from an AC power source into DC; An inverter that converts the direct current (DC) output by the converter into alternating current (AC) to supply power to the motor; and The inverter circuit control unit includes an instantaneous power calculation unit and a power consumption calculation unit. The instantaneous power calculation unit calculates the instantaneous power for each calculation cycle based on the voltage command to the inverter and the current supplied from the inverter to the motor. The power consumption calculation unit calculates the power consumption corresponding to the multiple instantaneous power values ​​calculated by the instantaneous power calculation unit. If the power consumption calculated by the power consumption calculation unit exceeds a preset power consumption threshold, the inverter circuit control unit causes the rotational speed of the drive device to be lower than the target rotational speed value.

2. The driving device according to claim 1, characterized in that, The inverter circuit control unit also includes an average power calculation unit. The average power calculation unit calculates the average value of the instantaneous power over multiple iterations. The power consumption calculation unit uses the average value of the instantaneous power to calculate the power consumption.

3. The driving device according to claim 1 or 2, characterized in that, Even if the power consumption calculated by the power consumption calculation unit does not exceed the preset power consumption threshold, if the speed of the drive device was lower than the target speed value in the previous calculation cycle, the inverter circuit control unit will also make the speed of the drive device lower than the target speed value in the current calculation cycle.

4. A driving method, which is a driving method for a drive device that rotates an electric motor based on a target rotational speed value. The driving method has the following steps: Converts the voltage from an AC power source to a DC power source; The converted DC is then converted into AC and supplied to the motor. Instantaneous power is calculated for each calculation cycle based on the voltage command to the inverter and the current supplied from the inverter to the motor. Calculate the power consumption corresponding to the multiple instantaneous powers; and If the power consumption exceeds a preset power consumption threshold, the rotational speed of the drive device will be lower than the target rotational speed value.

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