Converter control device

Abstract

To provide a converter control device with a power regeneration function that does not require adjustment of an off-operation time and a current detector for detecting a direct current, and that can suppress fluctuations in direct current voltage while suppressing switching loss and leakage current to a power supply.SOLUTION: A converter control device 10 with a power regeneration function comprises: a converter circuit 2 which converts alternating current power from a multiphase power supply into direct current power and converts the direct current power into the alternating current power; and a converter control unit 10 which controls switching of the converter circuit 2. The converter control unit 10 comprises: a current control unit 60 which generates a conduction width command from a difference between a current command and a direct current of the converter circuit; and a timing controller 20. The timing controller 20 generates a conduction start signal for the converter circuit on the basis of a phase signal of each phase of the multiphase power supply and the conduction width command during a regeneration operation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a converter control device. [Background technology]

[0002] A motor control device with a power regeneration function consists of a converter, a smoothing capacitor, and an inverter. When operating the motor in power mode, the motor control device converts AC power to DC power using the converter, and then converts the DC power back into AC power using the inverter, to drive the motor. When operating the motor in regenerative mode, the motor control device converts AC power generated by the motor into DC power using the inverter, and then converts the DC power back into AC power using the converter, which is then regenerated into the power supply.

[0003] Due to cost considerations, 120° energization power regeneration is often used for power regeneration converters. In 120° energization power regeneration, when AC power generated by a motor is converted to DC power through an inverter, the voltage of the DC section rises. When the voltage of the DC section reaches a predetermined voltage higher than the peak value of the full-wave rectified voltage of the power supply voltage, power regeneration is activated. Specifically, in the 120° section where the voltage of each phase of the power supply voltage is high, the switch of the converter for each phase is turned on to regenerate current to the power supply. In such motor control devices with power regeneration function, if the regenerative power from the motor is small, the power regeneration operation is repeatedly turned on and off, which makes the DC voltage of the DC section more likely to fluctuate.

[0004] For example, Patent Document 1 discloses a three-phase converter device that, in a regeneration mode, sets a reference drive signal with an ON operation time set so that switching elements are turned on during a 120° section where the voltage of each phase of the power supply voltage is high, calculates a DC current based on a three-phase AC current detected by a current detection means, sets an OFF operation time according to the magnitude of the DC current, and generates an ON correction drive signal adjusted based on the OFF operation time to shorten the ON operation time of the reference drive signal. The ON correction drive signal ensures an OFF operation time that delays the ON timing at the front end of the ON operation time of the reference drive signal and an OFF operation time that advances the OFF timing at the rear end of the ON operation time of the reference drive signal, correcting the OFF operation time so that twice the OFF operation time is ensured in the center of the reference drive signal. This allows for suppression of DC voltage fluctuations.

[0005] Furthermore, for example, Patent Document 2 discloses a converter control device including: a peak value detection means for detecting a phase-to-phase voltage peak value of an input AC power supply; a regeneration voltage setting means for setting a regeneration start voltage value obtained by adding a constant value to the phase-to-phase voltage peak value; a current command value setting means for outputting a current command value corresponding to the difference when the DC voltage at the output terminal of the regenerative converter exceeds the regeneration start voltage value; and a control means for generating an ON signal having a pulse width proportional to the difference when the regenerative current flowing from the output terminal to the regenerative converter is below the current command value, and applying the ON signal to a switching element to flow the regenerative current to the AC power supply side, thereby controlling the effective value of the regenerative current. By using the difference between the DC voltage and the regeneration start set voltage as the regenerative current command, fluctuations in the DC voltage can be suppressed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-165600 [Patent Document 2] Japanese Patent Application Publication No. 60-226778 Summary of the Invention [Problem to be solved by the invention]

[0007] The three-phase converter device disclosed in Patent Document 1 sets the off operation time according to the magnitude of the DC current. However, if the off operation time is set long relative to the DC current, the current cannot be regenerated to the power supply, resulting in a high DC voltage. On the other hand, if the off operation time is set short relative to the DC current, the regenerated current to the power supply increases, resulting in a drop in the DC voltage. For this reason, it is necessary to adjust the off time appropriately according to the DC current, which poses a problem of difficulty in adjustment.

[0008] The converter control device of Patent Document 2 outputs a current command based on the difference between the regeneration start voltage and the DC voltage, and controls the on-time of the pulse width based on the difference between the current command and the current. This controls the DC voltage to match the regeneration start voltage and the on-time to an appropriate value according to the current deviation. Therefore, when the regenerative power from the motor is small, fluctuations in the DC voltage due to the on / off switching of the power regeneration are suppressed, eliminating the need for the off-time adjustment described in Patent Document 1. However, the converter is controlled using a pulse width obtained by comparing the amplified current deviation with a triangular wave. The frequency of the triangular wave is set higher than the power frequency, which can lead to problems such as increased losses in semiconductor switching elements and increased leakage current to the power supply. Furthermore, in 120° conduction-type power regeneration, a current detector is typically provided to detect the power supply current of each phase to protect the semiconductor switches that make up the converter. However, the converter control device of Patent Document 2 requires an additional current detector to detect the regenerative current flowing from the output terminal to the regenerative converter, which increases costs.

[0009] Therefore, an object of the present invention is to provide a converter control device with a power regeneration function that can suppress fluctuations in DC voltage while suppressing switching loss and leakage current to the power supply, without requiring adjustment of the off operation time or a current detector for detecting DC current. [Means for solving the problem]

[0010] A converter control device with a power regeneration function according to one aspect of the present invention includes: a converter circuit that converts AC power from a multi-phase power supply into DC power and converts the DC power into the AC power; a converter control unit that controls switching of the converter circuit; Equipped with The converter control unit a current control unit that generates a current width command based on a difference between a current command and the DC current of the converter circuit; a timing controller; and During regenerative operation, the timing controller generates a current-on start signal for the converter circuit based on the phase signals of each phase of the multi-phase power supply and the current-on width command. [Effects of the Invention]

[0011] It is possible to provide a converter control device with a power regeneration function that suppresses fluctuations in DC voltage while suppressing switching loss and leakage current to the power supply, without requiring adjustment of the off operation time or a current detector to detect DC current. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram of a motor control device according to an embodiment of the present invention; [Figure 2] 10A and 10B are diagrams illustrating a power supply voltage, a current selection signal, a power supply current selected based on the current selection signal, and a regenerative current. [Figure 3] 10 is a graph showing the relationship between a current width command and a phase. [Figure 4] FIG. 10 is a diagram showing the waveform of a gate timing signal when the energization width command is large. [Figure 5] FIG. 10 is a diagram showing the waveform of a gate timing signal when a current width command is small. [Figure 6] FIG. 10 is a diagram showing the DC voltage and the operation mode when the motor is slowly decelerated. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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. [Embodiment]

[0014] FIG. 1 is a block diagram of a motor control device 1 according to an embodiment of the present invention. As shown in Fig. 1, motor control device 1 includes an AC reactor ACL, a converter circuit 2 having a power regeneration function, a smoothing capacitor 3, an inverter circuit 4, a current detection unit 5, and a converter control unit 10. Motor control device 1 is connected to an AC power supply 100 on the input side and a motor M on the output side. Note that AC power supply 100 is a three-phase AC power supply, but is not limited to three phases and may be any polyphase AC power supply.

[0015] 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, for example, of IGBTs and anti-parallel freewheeling diodes. When the motor M is in power running mode, the converter circuit 2 converts the three-phase AC input from the AC power supply 100 into DC. When the motor M is in regenerative mode, the AC power generated by the motor M is converted into DC by the inverter circuit 4, and the converter circuit 2 converts the converted DC into three-phase AC.

[0016] The smoothing capacitor 3 is, for example, an electrolytic capacitor, and smoothes the direct current output from the converter circuit 2.

[0017] 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, for example, of IGBTs and anti-parallel freewheeling diodes. When the motor M is in power running mode, the inverter circuit 4 converts the DC from the smoothing capacitor 3 or the DC output from the converter circuit 2 into three-phase AC for driving the motor and supplies it to the motor M. When the motor M is in regenerative mode, the inverter circuit 4 converts the AC power generated by the motor M into DC power.

[0018] The current detection unit 5 detects the power supply current of each phase flowing between the AC power supply 100 and the converter circuit 2.

[0019] 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 during the 120° section where the voltage of each phase of the power supply voltage is high, thereby regenerating power to the AC power supply 100.

[0020] Converter control unit 10 is composed of a timing creation unit 20, a regenerative operation determination unit 30, and a gate controller 11. Timing creation unit 20 has a voltage control unit 40, a DC current estimation unit 50, and a current control unit 60. Voltage control unit 40 has a voltage command calculator 41, a voltage controller 42, a limiter 43, and a filter 44. DC current estimation unit 50 has a phase detector 51, a current selection signal generation unit 52, a selector 53, and a filter 54. Current control unit 60 has a current controller 61, a limiter 62, a filter 63, and a gate timing controller 64. Regenerative operation determination unit 30 has a regeneration start detector 31 and a regeneration stop detector 32.

[0021] A voltage command calculator 41 detects a peak value Vp of the power supply voltage, and generates and outputs a voltage command Vc by adding a constant value Vs1 to the peak value Vp. A voltage controller 42 is configured, for example, as a proportional controller, and generates and outputs a current command Ic from the difference between the voltage command Vc and the DC voltage Vd applied to the smoothing capacitor 3. A limiter 43 limits the current command Ic so as to restrict the range of the regenerative current to the AC power supply 100, and a filter 44 removes ripple components from the current command Ic limited by the limiter 43.

[0022] A phase detector 51 detects the phase of a 120° section where the voltage of each phase of the power supply voltage is high and outputs a phase signal. A current selection signal generator 52 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 where the voltage increases or decreases, out of the two phases through which current flows.

[0023] The process of selecting an AC current will now be described in detail with reference to FIG. 2. FIG. 2 is a diagram showing a power supply voltage, a current selection signal, a power supply current (AC current) selected based on the current selection signal, and a regenerative current in an embodiment of the present invention. For example, in the first 60° section of a 120° section in which the R-phase voltage is high, indicated by reference numeral 52a, 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 a 120° section in which the R-phase voltage is high, indicated by reference numeral 52b, 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 DC current Id of the converter circuit 2 during regenerative operation has a negative sign.

[0024] Returning to the explanation of Fig. 1, the selector 53 selects the power supply current detected by the current detection unit 5 based on the AC current selection signal from the current selection signal generation unit 52, and outputs the selected power supply current. Here, the selection of the power supply current by the selector 53 is equivalent to AC-DC conversion, and a positive current value is output during power running. The filter 54 removes ripple components from the power supply current selected and output by the selector 53. The power supply current from which the ripple components have been removed by the filter 54 is output to the current control unit 60 and the regenerative operation determination unit 30 as an estimated value of the DC current Id.

[0025] In this way, the DC current estimation unit 50 detects the phase of the AC power with the highest voltage and selects the current of one of the phases of the AC power based on the detected phase, thereby making it possible to estimate with high accuracy the DC current Id of the converter circuit 2 during regenerative operation.

[0026] The current controller 61 is configured by, for example, a proportional controller, and generates and outputs a current width command Iwc from the difference between the current command Ic from the voltage control unit 40 and the estimated value of the DC current Id from the DC current estimation unit 50. A limiter 62 limits the range of the current conduction width, and a filter 63 removes ripple components from the current width command Iwc limited by the limiter 62.

[0027] The gate timing controller 64 generates a gate timing signal by advancing or delaying the phase of the gate-on timing based on the energization width command Iwc in response to the phase signal from the phase detector 51. FIG. 3 is a graph showing the relationship between the energization width command and the adjustment phase. As shown in FIG. 3, as the energization width command Iwc increases, the adjustment phase φ also increases. When the energization width command Iwc is Iwc0, the adjustment phase φ becomes 0, and the phase of the gate-on timing becomes the same as the phase signal. When the energization width command Iwc is greater than Iwc0, the adjustment phase φ becomes a positive value, and the phase of the gate-on timing is advanced. When the energization width command Iwc is smaller than Iwc0, the adjustment phase φ becomes a negative value, and the phase of the gate-on timing is delayed.

[0028] The specific process for generating the gate timing signal will be described with reference to Figures 4 and 5. Figure 4 is a diagram showing the waveform of the gate timing signal when the energization width command is large. Figure 5 is a diagram showing the waveform of the gate timing signal when the energization width command is small.

[0029] When the conduction width command Iwc is greater than Iwc0, the gate timing signal is generated by advancing the gate-on timing of the phase signal for each phase by the adjustment phase φ, as shown in Figure 4. This increases the conduction width of the semiconductor switching element for each phase. Furthermore, when any of the upper R-phase, S-phase, and T-phase semiconductor switching elements is in a conducting state and any of the lower R-phase, S-phase, and T-phase semiconductor switching elements is in a conducting state, regenerative operation is performed. Therefore, for example, if the gate timing signal for the R phase on the upper side is on and at least one of the gate timing signals for the S phase and T phase on the lower side is on, regeneration operation is performed in that section. As shown in FIG. 4, for example, in the section Turn when the gate timing signal for the R phase on the upper side is on, at least one of the gate timing signals for the S phase and T phase on the lower side is always on. The same is true for the section Tsron when the gate timing signal for the S phase on the upper side is on and the section Ttron when the gate timing signal for the T phase on the upper side is on. Therefore, power regeneration is always performed.

[0030] When the conduction width command Iwc is smaller than Iwc0, the gate timing signal is generated by delaying the gate-on timing of the phase signal of each phase by the adjustment phase φ, as shown in Figure 5. This reduces the conduction width of the semiconductor switching element of each phase. In the case of Figure 5, for example, in the section Tur on the upper side where the R-phase gate timing signal is on, the section on which at least one of the S-phase and T-phase gate timing signals on the lower side is on is limited. The same is true for the section Tsr on the upper side where the S-phase gate timing signal is on and the section Ttr on the upper side where the T-phase gate timing signal is on. Therefore, the section Tpr where power regeneration is performed is limited.

[0031] Returning to the explanation of Fig. 1, the regeneration start detector 31 detects that the DC voltage Vd applied to the smoothing capacitor 3 is equal to or greater than the regeneration operation reference voltage Vstd, and outputs a regeneration operation start signal to the gate controller 11. Here, the regeneration operation reference voltage Vstd is a value that is higher than the peak value Vp of the power supply voltage by a predetermined value Vs2, and is a reference value used by the converter control unit 10 to determine whether or not to perform regeneration. The regeneration stop detector 32 detects that the estimated value of the DC current Id output from the DC current estimator 50 is 0 for a certain period of time, and outputs a regeneration operation stop signal to the gate controller 11.

[0032] The gate controller 11 generates a gate control signal based on the gate timing signal from the gate timing controller 64, the regenerative operation start signal from the regenerative start detector 31, and the regenerative operation stop signal from the regenerative stop detector 32. The gate controller 11 also outputs the gate control signal to the converter circuit 2 to control the semiconductor switching elements of the converter circuit 2.

[0033] FIG. 6 shows the DC voltage and operating mode when the motor is slowly decelerated. As shown in FIG. 6, slowly decelerating the motor M increases the DC voltage Vd across the smoothing capacitor 3. Next, at time t0, the regeneration start detector 31 detects that the DC voltage Vd is equal to or greater than the regeneration operation reference voltage Vstd, and outputs a regeneration operation start signal to the gate controller 11. Consequently, the gate controller 11 turns on the semiconductor switching elements of the converter circuit 2 to start regeneration. After that, the estimated value of the DC current Id and the current command increase in the negative direction (the regeneration direction), and the conduction duration command Iwc increases. After that, from time t1, the estimated value of the DC current Id and the current command gradually increase in the positive direction, and the conduction duration command Iwc decreases. Therefore, the period Tpr during which regeneration is performed gradually narrows. After that, at time t2, the regeneration stop detector 32 detects that the estimated value of the DC current Id is 0 for a certain period of time, and outputs a regeneration operation stop signal to the gate controller 11. As a result, the gate controller 11 turns off the semiconductor switching elements of the converter circuit 2 to stop the regeneration operation.

[0034] In this way, when the motor M is slowly decelerated, the regenerative operation continues without the operation mode repeatedly transitioning between the power running operation and the regenerative operation, even though the regenerative power from the motor M to the AC power supply 100 is small. Furthermore, the DC voltage Vd during the regenerative operation is stable in the range of 290V to 300V.

[0035] As described above, the embodiment of the present invention does not require adjustment of the off operation time or a current detector for detecting DC current, and suppresses fluctuations in DC voltage while suppressing switching loss and leakage current to the power supply.

[0036] 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]

[0037] 1: Motor control device 2: Converter circuit 3: Smoothing capacitor 4: Inverter circuit 5: Current detection section 10: Converter control section 11: Gate controller 20: Timing creation section 30: Regenerative operation determination unit 31: Regeneration start detector 32: Regeneration stop detector 41: Voltage command calculator 42: Voltage controller 43, 62: Limiter 44, 54, 63: Filter 50: DC current estimation section 51: Phase detector 52: Current selection signal generation unit 53: Selector 61: Current controller 64: Gate timing controller 100: AC power supply M: Motor φ: Adjustment phase

Claims

1. A converter control device with a power regeneration function, a converter circuit that converts AC power from a multi-phase power supply into DC power and converts the DC power into the AC power; a converter control unit that controls switching of the converter circuit; Equipped with The converter control unit a current control unit that generates a current width command based on a difference between a current command and the DC current of the converter circuit; a timing controller; and The converter control device according to claim 1, wherein the timing controller generates a current start signal for the converter circuit based on the phase signals of each phase of the multi-phase power supply and the current width command during regenerative operation.

2. the converter control unit further includes a voltage control unit, the voltage control unit has a voltage command calculator, and generates the current command from a difference between a voltage command and a DC voltage of the DC power; 2. The converter control device according to claim 1, wherein the voltage command calculator calculates the voltage command as a value obtained by adding a constant value to a peak value of the voltage of the multi-phase power supply.

3. the converter control unit further includes a DC current acquisition unit that acquires the DC current; The converter control device according to claim 1 , wherein the DC current acquisition unit is configured by a DC current estimation unit or a DC current detector.

4. The DC current estimation unit 4. The converter control device according to claim 3, wherein a phase of the AC power having a higher voltage is detected, and a current of any one of the phases of the AC power is selected based on the detected phase to estimate the DC current.

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