Motor drive unit

Abstract

Provided is a motor drive device that eliminates the need for wiring to detect the voltage of an AC power supply, reducing wiring costs, and that can appropriately control a converter circuit without being affected by voltage drops in an AC reactor due to power current or regenerative current. [Solution] A motor drive device includes a converter circuit that converts AC power from a three-phase AC power supply into DC power, a converter control unit that controls switching of the converter circuit, an AC reactor disposed between the three-phase AC power supply and the converter circuit, and a voltage detection unit that detects the three-phase AC voltage between the AC reactor and the converter circuit. The converter control unit estimates the voltage of the three-phase AC power supply based on the three-phase AC voltage detected by the voltage detection unit and the impedance of the AC reactor.

Description

[Technical Field]

[0001] The present invention relates to a motor drive device. [Background technology]

[0002] A motor drive unit with a power regeneration function consists of an AC reactor, a converter circuit, a smoothing capacitor, and an inverter circuit. When the motor is in power running mode, the converter circuit converts AC power to DC power, and the inverter circuit converts the DC power back into AC power to drive the motor. When the motor is in regenerative mode, the inverter circuit converts the AC power generated by the motor back into DC power, and the converter circuit converts the DC power back into AC power, which is then regenerated into the power supply. Furthermore, the 120° energization method is often used as a power regeneration method due to cost considerations.

[0003] As an example of controlling the start and stop of such a power regeneration function, a power regeneration control device is disclosed in Patent Document 1. The power regeneration control device includes an AC reactor provided in a connection path connecting the AC side of a rectification and regeneration circuit to a polyphase AC power supply, a first capacitor connected in parallel to the DC side of the rectification and regeneration circuit, a bridge rectifier circuit that converts the AC output of the polyphase AC power supply into a DC output, a second capacitor connected in parallel to the bridge rectifier circuit, a detection circuit that detects the start and end of regeneration based on the differential voltage between the charging voltages of the first and second capacitors, and an electric valve drive circuit that receives a regeneration start detection signal from the detection circuit and sequentially supplies drive signals to the electric valves of the rectification and regeneration circuit. In this way, the power regeneration control device controls the start and stop of power regeneration based on the differential voltage between the peak value of the AC power supply voltage and the output voltage of the power regeneration control device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 60-187268 Summary of the Invention [Problem to be solved by the invention]

[0005] The power regeneration control device disclosed in Patent Document 1 detects the peak value of the AC power supply voltage by connecting a bridge rectifier circuit and a second capacitor to the AC power supply. This is not a major problem if the capacity of the power regeneration control device is small and the AC reactor can be installed inside the power regeneration control device. However, if the capacity of the power regeneration control device is large and the AC reactor must be installed outside the power regeneration control device, wiring must be connected from the AC power supply to the bridge rectifier circuit inside the power regeneration control device to detect the peak value of the AC power supply voltage. However, this type of wiring increases the manufacturing costs of the device using the power regeneration control device and may lead to incorrect wiring.

[0006] On the other hand, in order to eliminate the wiring between the AC power supply and the bridge rectifier circuit in the power regeneration control device, it is conceivable to connect the bridge rectifier circuit to the output side of the AC reactor and detect the AC voltage in the bridge rectifier circuit. However, when current flows through the AC reactor during motor power running, the AC voltage input to the bridge rectifier circuit becomes lower than the AC power supply voltage due to the voltage drop in the AC reactor. Also, when current flows through the AC reactor during motor regeneration, the AC voltage input to the bridge rectifier circuit becomes higher than the AC power supply voltage due to the voltage drop in the AC reactor. This has led to problems such as power regeneration not operating when it should, or operating when it should not.

[0007] Therefore, an object of the present invention is to provide a motor drive device that detects the output voltage of an AC reactor, estimates the voltage of the AC power supply, and controls a converter circuit thereby eliminating the need for wiring to detect the voltage of the AC power supply, thereby reducing wiring costs, and that can appropriately control the converter circuit without being affected by the voltage drop in the AC reactor due to powering current or regenerative current. [Means for solving the problem]

[0008] A motor drive device according to one aspect of the present invention comprises: a converter circuit for converting AC power from a three-phase AC power source into DC power; a converter control unit that controls switching of the converter circuit; an AC reactor disposed between the three-phase AC power supply and the converter circuit; a voltage detection unit that detects a three-phase AC voltage between the AC reactor and the converter circuit; Equipped with The converter control unit estimates the voltage of the three-phase AC power supply based on the three-phase AC voltage detected by the voltage detection unit and the impedance of the AC reactor. [Effects of the Invention]

[0009] This makes it possible to provide a motor drive device that eliminates the need for wiring to detect the voltage of the AC power supply, reducing wiring costs, and that can appropriately control the converter circuit without being affected by voltage drops in the AC reactor due to power current or regenerative current. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram of a motor drive device according to a first embodiment of the present invention. [Figure 2] 10A and 10B are diagrams illustrating a power supply voltage, a phase signal, a current selection signal, a power supply current selected based on the current selection signal, and a DC current. [Figure 3] 10A and 10B are diagrams showing waveforms of voltage boosting operation and regenerative operation when the motor is accelerated and decelerated. [Figure 4] FIG. 4 is a block diagram of a motor drive device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For the sake of convenience, the description of components having the same reference numerals as components already described in the description of the embodiments will be omitted.

[0012] [First embodiment] FIG. 1 is a block diagram of a motor driving device 100 according to a first embodiment of the present invention. 1, motor drive device 100 includes motor control device 1 and an AC reactor ACL. Motor control device 1 also includes converter circuit 2, smoothing capacitor 3, inverter circuit 4, current detector 5, voltage detection unit 6, and converter control unit 10. Motor control device 1 has AC reactor ACL connected to its input side and motor M connected to its output side. AC reactor ACL is also connected to a three-phase AC power supply 200.

[0013] During powering operation, the motor control device 1 energizes the semiconductor switching elements of the converter circuit 2 in response to gate signals from the converter control unit 10 in a 120° section of the phase of the three-phase AC power supply where the voltage is maximum, thereby supplying power from the three-phase AC power supply 200 to the motor M. During regenerative operation, the motor control device 1 energizes the semiconductor switching elements of the converter circuit 2 in response to gate control signals from the converter control unit 10 in a 120° section where the voltage of each phase of the three-phase AC power supply is maximum and in a 120° section where the voltage of each phase of the three-phase AC power supply is minimum, thereby regenerating power to the AC power supply 200.

[0014] The converter circuit 2 is a three-phase (R-phase, S-phase, T-phase) full-bridge circuit and is composed of six semiconductor switching elements. The semiconductor switching elements are composed of, for example, IGBTs. When the motor M is in power running mode, the converter circuit 2 converts three-phase AC input from the three-phase AC power supply 200 into DC. When the motor M is in regenerative mode, the converter circuit 2 converts DC into three-phase AC.

[0015] The smoothing capacitor 3 is, for example, an electrolytic capacitor, and smoothes the direct current output from the converter circuit 2.

[0016] The inverter circuit 4 is a three-phase (U-phase, V-phase, W-phase) full-bridge circuit and is composed of six semiconductor switching elements. The semiconductor switching elements are composed of, for example, IGBTs. The inverter circuit 4 converts the direct current from the smoothing capacitor 3 or the direct current output by the converter circuit 2 into three-phase alternating current for driving the motor M and supplies it to the motor M.

[0017] The current detector 5 detects the power supply current of each phase flowing between the three-phase AC power supply 200 and the converter circuit 2 .

[0018] The voltage detection unit 6 detects the three-phase AC voltage between the AC reactor ACL and the converter circuit 2 (hereinafter also referred to as the ACL output voltage).

[0019] The converter control unit 10 includes a DC current estimation unit 20, a power supply voltage estimation unit 30, a regenerative voltage control unit 40, a boost voltage control unit 50, a regenerative operation determination unit 60, a boost operation determination unit 70, and a gate control unit 80. The DC current estimation unit 20 includes a phase detector 21, a current selection signal generation unit 22, and a selector 23. The power supply voltage estimation unit 30 includes a full-wave rectified voltage calculator 31, a voltage drop calculator 32, and a peak value calculator 33. The regenerative voltage control unit 40 includes a regenerative voltage command calculator 41, a regenerative voltage controller 42, and a regenerative current controller 43. The boost voltage control unit 50 includes a boost voltage command calculator 51, a boost voltage controller 52, and a boost current controller 53. The regenerative operation determination unit 60 includes a regeneration start detector 61 and a regeneration stop detector 62. The boost operation determination unit 70 includes a boost start detector 71 and a boost stop detector 72. The gate control unit 80 includes a gate controller 81.

[0020] The DC current estimation unit 20 estimates the DC current Id flowing from the converter circuit 2 to the smoothing capacitor 3. The phase detector 21 detects the phase of the 120° section in which the voltage of each phase of the ACL output voltage is maximum, and outputs a phase signal. The current selection signal generation unit 22 generates an AC current selection signal for current selection based on the phase signal. The AC current selection signal is generated so as to select the power supply current of the phase in which the voltage increases or decreases, out of the two phases through which current flows.

[0021] The process of selecting an AC current will now be described in detail with reference to FIG. 2. FIG. 2 is a diagram showing the power supply voltage, phase signal, current selection signal, power supply current (AC current) selected based on the current selection signal, and DC current Id in an embodiment of the present invention. For example, in the first 60° section of the 120° section in which the R-phase voltage is maximum, indicated by reference numeral 22a, power supply currents for the R and S phases flow, and the R-phase voltage is increasing, so the R-phase is selected. Also, in the second 60° section of the 120° section in which the R-phase voltage is maximum, indicated by reference numeral 22b, power supply currents for the R and T phases flow, and the T-phase voltage is increasing in the negative direction, so the T-phase power supply current is selected with its sign inverted. The sign is inverted so that the sign of the DC current Id of the converter circuit 2 during regenerative operation is negative.

[0022] Returning to the explanation of Fig. 1, the selector 23 selects the power supply current of each phase flowing between the three-phase AC power supply 200 detected by the current detector 5 and the converter circuit 2 based on the AC current selection signal from the current selection signal generation unit 22, and estimates the DC current Id of the DC power converted by the converter circuit 2. Furthermore, the estimated DC current Id is output to the voltage drop calculator 32, the regenerative current controller 43, and the boost current controller 53. Here, the selection of the power supply current by the selector 23 is equivalent to AC-to-DC conversion.

[0023] In this way, the DC current estimation unit 20 detects the phase of the AC power in which the voltage is maximum, and selects the current of one of the phases of the AC power based on the detected phase, thereby making it possible to estimate the DC current Id of the converter circuit 2 with high accuracy.

[0024] The power supply voltage estimation unit 30 estimates the power supply voltage peak value Vp for each cycle of the three-phase AC power supply 200. The full-wave rectified voltage calculator 31 calculates and outputs the ACL output full-wave rectified voltage Vacl from the ACL output voltage detected by the voltage detection unit 6. The voltage drop calculator 32 calculates and outputs the voltage drop Vdr of the AC reactor ACL from the product of the estimated DC current Id and the impedance of the AC reactor ACL. The peak value calculator 33 calculates and outputs the power supply voltage peak value Vp for each cycle of the three-phase AC power supply 200 from the power supply voltage full-wave rectified voltage, which is the sum of the ACL output full-wave rectified voltage Vacl and the voltage drop Vdr of the AC reactor ACL.

[0025] In this way, by estimating the power supply voltage peak value Vp for each cycle of the three-phase AC power supply 200 in consideration of the voltage drop Vdr of the AC reactor ACL, it is possible to estimate the power supply voltage peak value Vp with high accuracy while reducing the wiring cost for detecting the voltage of the three-phase AC power supply 200.

[0026] The regenerative voltage command calculator 41 calculates and outputs a regenerative voltage command based on the power supply voltage peak value Vp from the peak value calculator 33. The regenerative voltage controller 42 controls the DC voltage Vd applied to the smoothing capacitor 3 during regenerative operation to be constant based on the regenerative voltage command from the regenerative voltage command calculator 41, and calculates and outputs a regenerative current command. The regenerative current controller 43 controls the semiconductor switching elements of the converter circuit 2 during regenerative operation via the gate controller 81 as an inner loop for regenerative voltage control. To this end, the regenerative current controller 43 calculates and outputs a regenerative current command based on the regenerative current command from the regenerative voltage controller 42.

[0027] The boost voltage command calculator 51 calculates and outputs a boost voltage command based on the power supply voltage peak value Vp from the peak value calculator 33. The boost voltage controller 52 controls the DC voltage Vd applied to the smoothing capacitor 3 during boost operation to be constant based on the boost voltage command from the boost voltage command calculator 51, and calculates and outputs a boost current command. The boost current controller 53 controls the semiconductor switching elements of the converter circuit 2 during boost operation via the gate controller 81 as an inner loop of the boost voltage control. To this end, the boost current controller 53 calculates and outputs a boost energization command based on the boost current command from the boost voltage controller 52.

[0028] In this way, by controlling the DC voltage Vd applied to the smoothing capacitor 3 to be constant based on the estimated power supply voltage peak value Vp, the converter circuit 2 can be appropriately controlled without being affected by the voltage drop Vdr in the AC reactor due to the power running current or regenerative current.

[0029] The regeneration start detector 61 compares the DC voltage Vd applied to the smoothing capacitor 3 with the peak value Vp of the power supply voltage, and turns on the regeneration signal when the DC voltage Vd is equal to or greater than a first threshold Th1 that is higher than the peak value Vp of the power supply voltage by a predetermined value (+40 V in the example of FIG. 3). The regeneration stop detector 62 turns off the regeneration signal when, for example, the regeneration energization command is off (for example, the energization command is 0) for a predetermined time. The regeneration signal generated by the regeneration operation determination unit 60 is output to the gate controller 42.

[0030] The boost start detector 71 compares the DC voltage Vd applied to the smoothing capacitor 3 with the peak value Vp of the power supply voltage, and turns on the boost signal when the DC voltage Vd is equal to or less than a second threshold Th2 that is lower than the peak value Vp of the power supply voltage by a predetermined value (15 V in the example of FIG. 3). The boost stop detector 72 turns off the boost signal when it detects that the boost energization command has been off (e.g., the energization command is 0) for a predetermined time, for example. The boost signal generated by the boost operation determination unit 70 is output to the gate controller 42.

[0031] The gate controller 81 generates a gate signal based on the phase signal from the phase detector 21, the regenerative current command from the regenerative current controller 43, the boost current command from the boost current controller 53, the regenerative signal from the regenerative operation determination unit 60, and the boost signal from the boost operation determination unit 70. The gate controller 81 also outputs the gate signal to the converter circuit 2 to control the semiconductor switching elements of the converter circuit 2.

[0032] Specifically, when the regeneration signal from the regeneration operation determination unit 60 is turned on, the gate controller 81 starts the regeneration operation, and generates a gate signal to control the semiconductor switching elements of the converter circuit 2 based on the regeneration current command from the regeneration current controller 43, and outputs the gate signal to the converter circuit 2. Also, when the regeneration signal from the regeneration operation determination unit 60 is turned off, the gate controller 81 ends the regeneration operation.

[0033] Furthermore, when the boost signal from the boost operation determination unit 70 is turned on, the gate controller 81 starts the boost operation, generates a gate signal to control the semiconductor switching elements of the converter circuit 2 based on the boost current command from the boost current controller 53, and outputs the gate signal to the converter circuit 2. Furthermore, when the boost signal from the boost operation determination unit 70 is turned off, the gate controller 81 ends the boost operation.

[0034] FIG. 3 shows waveforms of the boost operation and regenerative operation when the motor M is accelerated and decelerated. As shown in FIG. 3, when the motor M accelerates at time t0, a powering current flows through the AC reactor ACL. As a result, the ACL output full-wave rectified voltage Vacl drops due to a voltage drop Vdr across the AC reactor ACL in the direction in which the powering current flows. When the motor M decelerates and starts regenerative operation at time t1, a regenerative current flows through the AC reactor ACL. As a result, the ACL output full-wave rectified voltage Vacl rises due to the voltage drop Vdr across the AC reactor ACL in the direction in which the regenerative current flows. When the motor M decelerates and then accelerates again and starts boost operation at time t2, a powering current flows through the AC reactor ACL again. As a result, the ACL output full-wave rectified voltage Vacl drops again due to the voltage drop Vdr across the AC reactor ACL in the direction in which the powering current flows.

[0035] Here, the power supply voltage estimation unit 30 compensates for the voltage drop Vdr of the AC reactor ACL, thereby estimating the power supply voltage peak value Vp as a substantially constant value without being affected by the power running current or regenerative current flowing through the AC reactor ACL. This allows the boost operation and regenerative operation to be performed at appropriate timing when the motor M accelerates or decelerates. That is, when the motor M accelerates, the DC voltage Vd temporarily drops and starts the boost operation, and then the DC voltage Vd is controlled to be substantially equal to the power supply voltage peak value Vp. When the motor M decelerates, the DC voltage Vd rises and starts the regenerative operation, and the DC voltage Vd is controlled to a value obtained by adding +40 V to the power supply voltage peak value Vp. Furthermore, when the motor M decelerates once and then accelerates again, the DC voltage Vd drops to the power supply voltage peak value Vp and starts the boost operation again, thereby controlling the DC voltage Vd to be substantially equal to the power supply voltage peak value Vp.

[0036] [Second embodiment] FIG. 4 is a block diagram of a motor drive device 100′ according to a second embodiment of the present invention. As shown in FIG. 4, the motor drive device 100′ includes a motor control device 1′ and an AC reactor ACL. The motor control device 1′ also includes a converter circuit 2, a smoothing capacitor 3, an inverter circuit 4, a current detector 5′, a voltage detection unit 6, and a converter control unit 10. The converter control unit 10 includes a phase detection unit 20′, a power supply voltage estimation unit 30′, a regenerative voltage control unit 40, a boost voltage control unit 50, a regenerative operation determination unit 60, a boost operation determination unit 70, and a gate control unit 80.

[0037] Below, only the differences from motor drive device 100 according to the first embodiment shown in Fig. 1 will be explained. The AC reactor ACL, converter circuit 2, smoothing capacitor 3, inverter circuit 4, voltage detection unit 6, regenerative voltage control unit 40, boost voltage control unit 50, regenerative operation determination unit 60, boost operation determination unit 70, and gate control unit 80 are common to motor drive device 100 according to the first embodiment shown in Fig. 1, and therefore explanations thereof will be omitted.

[0038] The current detector 5' detects the DC current Id flowing between the converter circuit 2 and the inverter circuit 4. That is, in the second embodiment, the DC current Id is not estimated as in the first embodiment, but is directly detected. This allows the regenerative current controller 43 and the boost current controller 53 to more accurately control the semiconductor switching elements of the converter circuit 2 during regenerative operation and boost operation via the gate controller 81, respectively.

[0039] The phase detection unit 20' has a phase detector 21. The phase detector 21 detects the phase of the 120° section in which the voltage of each phase of the ACL output voltage is at its maximum, and outputs a phase signal.

[0040] The power supply voltage estimation unit 30' has a full-wave rectified voltage calculator 31, a voltage drop calculator 32, and a peak value calculator 33. The full-wave rectified voltage calculator 31 calculates and outputs an ACL output full-wave rectified voltage Vacl from the ACL output voltage detected by the voltage detection unit 6. The voltage drop calculator 32 calculates and outputs a voltage drop Vdr of the AC reactor ACL from the product of the DC current Id detected by the current detector 5' and the impedance of the AC reactor ACL. The peak value calculator 33 calculates and outputs a power supply voltage peak value Vp for each cycle of the three-phase AC power supply 200 from the power supply voltage full-wave rectified voltage, which is the sum of the ACL output full-wave rectified voltage Vacl and the voltage drop Vdr of the AC reactor ACL.

[0041] As with the motor drive device 100 according to the first embodiment shown in FIG. 3, the motor drive device 100′ according to the second embodiment can also perform boost and regenerative operations at appropriate timings when accelerating or decelerating the motor M. That is, when the motor M accelerates, the DC voltage Vd temporarily drops and a boost operation begins, and thereafter the DC voltage Vd is controlled to be substantially equal to the power supply voltage peak value Vp. When the motor M decelerates, the DC voltage Vd rises and a regenerative operation begins, and the DC voltage Vd is controlled to a value obtained by adding +40 V to the power supply voltage peak value Vp. Furthermore, when the motor M decelerates once and then accelerates again, the DC voltage Vd drops to the power supply voltage peak value Vp, and a boost operation begins again, and the DC voltage Vd is controlled to be substantially equal to the power supply voltage peak value Vp.

[0042] As described above, in the first and second embodiments of the present invention, the output voltage of the AC reactor is detected, the voltage of the AC power supply is estimated, and the converter circuit is controlled. This eliminates the need for wiring to detect the voltage of the AC power supply, reducing wiring costs, and makes it possible to appropriately control the converter circuit without being affected by the voltage drop in the AC reactor due to powering current or regenerative current.

[0043] Although the embodiments of the present invention have been described above, it goes without saying that the technical scope of the present invention should not be construed as being limited by the description of the present embodiments. The present embodiments are merely examples, and it will be understood by those skilled in the art that various modifications of the embodiments are possible within the scope of the invention described in the claims. The technical scope of the present invention should be determined based on the scope of the invention described in the claims and its equivalents. [Explanation of symbols]

[0044] 1, 1': Motor control device 2: Converter circuit 3: Smoothing capacitor 4: Inverter circuit 5, 5': Current detector 10, 10': Converter control section 20: DC current estimation section 21: Phase detector 22: Current selection signal generation unit 23: Selector 30: Power supply voltage estimation unit 31: Full-wave rectified voltage calculator 32: Voltage drop calculator 33: Peak value calculator 40: Regenerative voltage control unit 41: Regenerative voltage command calculator 42: Regenerative voltage controller 43: Regenerative current controller 51: Boost voltage command calculator 52: Boost voltage controller 53: Boost current controller 60: Regenerative operation determination unit 61: Regeneration start detector 62: Regeneration stop detector 70: Boost operation determination unit 71: Boost start detector 72: Boost stop detector 80: Gate control section 81: Gate controller 100, 100': Motor drive unit 200: Three-phase AC power supply M: Motor ACL: AC reactor

Claims

1. a converter circuit for converting AC power from a three-phase AC power source into DC power; a converter control unit that controls switching of the converter circuit; an AC reactor disposed between the three-phase AC power supply and the converter circuit; a voltage detection unit that detects a three-phase AC voltage between the AC reactor and the converter circuit; Equipped with the converter control unit estimates the voltage of the three-phase AC power supply based on the three-phase AC voltage detected by the voltage detection unit and impedance of the AC reactor.

2. 2. The converter control device according to claim 1, wherein the converter control unit controls the DC voltage of the DC power based on the estimated voltage of the three-phase AC power supply.

3. 2. The motor drive device according to claim 1, wherein the converter control unit estimates a voltage after full-wave rectification of the three-phase AC power supply based on the three-phase AC voltage detected by the voltage detection unit and impedance of the AC reactor.

4. the converter control unit further includes a DC current acquisition unit that acquires a DC current of the DC power, The motor drive device according to claim 1 , wherein the DC current acquisition unit is configured by a DC current estimation unit or a DC current detector.

5. 5. The motor drive device according to claim 4, wherein the DC current estimation unit detects a phase of the AC power having a higher voltage, selects a current of one of the phases of the AC power based on the detected phase, and estimates the DC current.

Images