Motor drive device and power supply regeneration method for motor drive device

Abstract

The present invention provides a motor drive device in which inrush current is suppressed during power supply regeneration and which can maintain high efficiency of power supply regeneration regardless of the magnitude of output. The motor drive device comprises: a rectifier which includes a plurality of rectifying elements that perform a rectifying operation, a plurality of switching elements that are provided in parallel with the rectifying elements and perform ON / OFF operation, and a capacitor, and which performs power conversion between AC power in a multi-phase AC power supply and DC power on the DC side; and a control device for controlling the ON / OFF operation of the plurality of switching elements on the basis of a determination result as to whether the rectifier is brought into a power supply state or a power supply regeneration state. The motor drive device drives a motor on the basis of the DC power. The control device defines, as a first set ON period, a period obtained by adding a first set value to a period of each phase of the AC power supply. In the power supply regeneration state, the control device adjusts the length of the first set ON period to control the ON / OFF operation of the plurality of switching elements.

Description

Motor drive device and power regeneration method for motor drive device

[0001] The present disclosure relates to a motor drive device and a power regeneration method for the motor drive device.

[0002] Conventionally, motor drive devices for driving motors in machine tools, forging machines, injection molding machines, industrial machines, and various robots have been widely used. The motor drive device, for example, converts AC power supplied from a three-phase AC power source into DC power by a rectifier and outputs it to a DC link, and further converts the DC power in the DC link into AC power by an inverter (inverter) to drive the motor. Here, the "DC link" is a circuit portion that electrically connects the DC output side of the rectifier and the DC input side of the inverter, and is also referred to as a "DC link section", "DC link", "DC link section", "DC bus", or "DC intermediate circuit".

[0003] By the way, in recent years, in order to achieve energy saving by effectively using the power supply in the motor drive device, power regeneration that returns the energy during motor deceleration to the power supply has been performed. As a motor drive device having such a power regeneration function, for example, a 120-degree conduction method that can return the regenerative power generated during motor deceleration to a three-phase AC power source is known.

[0004] The rectifier in a motor drive device using the 120-degree conduction method is configured as a three-phase bridge circuit in which power elements composed of rectifying elements and switching elements are provided in the upper arm and the lower arm of each of the three phases. In such a motor drive device using the 120-degree conduction method, the phase of the three-phase AC power source is detected, and every time the voltage of each phase of the three-phase AC power source is switched, the switching element in the upper arm of the phase where the phase voltage becomes maximum among the phases is turned on, and at the same time, the switching element in the lower arm of the phase where the phase voltage becomes minimum among the phases is turned on, so that the DC power is converted into AC power and regenerated to the three-phase AC power source. Here, the "degree (°)" in "120 degrees" is a unit representing the phase angle of the three-phase voltage or the three-phase current.

[0005] Conventionally, various proposals have been made for motor drive devices (rectifiers) having a power regeneration function.

[0006] Japanese Patent Publication No. 2021-093803, Japanese Patent Publication No. 2013-165600, Japanese Patent Publication No. 62-104481, Japanese Patent Publication No. 01-047280

[0007] As mentioned above, a motor drive device has been realized that performs power regeneration by controlling the on / off operation (switching) of a switch element using a 120-degree energization method. This power regeneration starts, for example, when the DC link voltage (DC voltage from the rectifier) ​​rises above a threshold (> peak power voltage). Here, the start of power regeneration is set to include a predetermined margin between the threshold and the peak power voltage, for example, to suppress malfunctions. However, if the margin is large and the threshold is too far from the peak power voltage, there is a problem in that an inrush current flows when power regeneration starts, resulting in large losses in the switch element.

[0008] Furthermore, in conventional 120-degree phase switching, a method is known to improve the efficiency of power regeneration by overlapping (overlapping) the on-periods of the switching elements in the phases before and after the switching, thereby improving the current connection. However, there is a problem in that overlapping the on-periods of the switching elements when the output is small can actually decrease the efficiency of power regeneration.

[0009] Therefore, there is a need for a motor drive system and a power regeneration method for a motor drive system that can suppress inrush current during power regeneration and maintain high power regeneration efficiency regardless of the output level.

[0010] According to one embodiment of the present disclosure, a motor drive device is provided that drives a motor based on DC power, comprising: a rectifier that performs power conversion between AC power in a multiphase AC power source and DC power on the DC side, including a plurality of rectifier elements that perform rectification operation, a plurality of switch elements that are provided in parallel with the rectifier elements and perform on / off operation, and a capacitor, and a control device that controls the on / off operation of the plurality of switch elements based on a determination result of whether the rectifier is in a power supply state or a power regeneration state.

[0011] The control device defines the period obtained by adding a first set value to the duration of each phase of the AC power supply as the first set on period, and controls the on / off operation of multiple switch elements by adjusting the length of the first set on period during power regeneration.

[0012] Figure 1 is a circuit block diagram showing an example of a motor drive device. Figure 2 is a diagram illustrating an example of the operation of a rectifier in the motor drive device shown in Figure 1. Figure 3 is a waveform diagram illustrating the challenges during power regeneration in the motor drive device shown in Figure 1. Figure 4 is a circuit block diagram showing one embodiment of the motor drive device according to this embodiment. Figure 5 is a circuit block diagram showing a modified example of the motor drive device shown in Figure 4. Figure 6 is a diagram illustrating an example of processing based on the determination result of the current interruption determination unit in the motor drive device shown in Figure 5. Figure 7 is a diagram illustrating an example of the current interruption operation in the motor drive device shown in Figure 5. Figure 8 is a diagram illustrating one embodiment of the power regeneration method of the motor drive device according to this embodiment. Figure 9 is a diagram illustrating another embodiment of the power regeneration method of the motor drive device according to this embodiment. Figure 10 is a diagram illustrating an embodiment of the power regeneration method performed by the motor drive device shown in Figure 4. Figure 11 is a waveform diagram illustrating the current limit operation in the embodiment of the motor drive device according to this embodiment shown in Figure 10. Figure 12 is a diagram illustrating an example of power regeneration operation in one embodiment of the motor drive device according to this embodiment. Figure 13 illustrates another example of the power regeneration operation in one embodiment of the motor drive device according to this embodiment. Figure 14 illustrates a modified example of the power regeneration operation described with reference to Figure 13. Figure 15 illustrates an example of the power regeneration operation in another embodiment of the motor drive device according to this embodiment. Figure 16 illustrates a modified example of the power regeneration operation shown in Figure 15. Figure 17 is a waveform diagram illustrating a modified example of the power regeneration method of the motor drive device described with reference to Figure 10. Figure 18 illustrates the value of β in the power regeneration method of the motor drive device according to this embodiment.

[0013] First, before detailing the embodiments of the motor drive device and the power regeneration method for the motor drive device according to this embodiment, an example of a motor drive device and its problems will be described with reference to Figures 1 to 3. In this specification, a three-phase AC power supply is used as the power supply for the motor drive device (rectifier), and a 120-degree energization method is used to return the regenerative power generated during motor deceleration to the three-phase AC power supply, but it goes without saying that various changes and modifications are possible.

[0014] Figure 1 is a circuit block diagram showing an example of a motor drive device, illustrating an example of a motor drive device (200) that receives power from a three-phase AC power supply 2 and drives a three-phase AC motor (M) 3. Here, the motor 3 is not limited to a three-phase AC motor, but may be a motor with other numbers of phases, and may be an induction motor or a synchronous motor.

[0015] As shown in Figure 1, the motor drive unit 200 includes a rectifier 1, a voltage detection unit 11, a current detection unit 12, a control device 13', a DC voltage detection unit 14, and an inverter 15. The rectifier 1 includes a plurality of switching elements RHa, SHHa, THa, RLa, SLa, TLa and rectifying elements RHb, SHb, THb, RLb, SLb, TLb, and a capacitor (DC link capacitor) 10, and has a rectification function that converts AC voltage to DC voltage, as well as a power regeneration function. That is, the rectifier 1 performs power conversion between AC power in the three-phase AC power supply 2 and DC power on the DC side.

[0016] Here, the switching elements RHa, SH, THa, RLa, SLa, TLa and the rectifying elements RHb, SHb, THb, RLb, SLb, TLb are connected in parallel to form the power elements RHa, RHb, SHHa, SHb, THa, THb, RLa, RLb, SLa, SLb, TLa, TLb. Note that power regeneration by the rectifier 1 is performed based on the switching (on / off operation) of the switching elements RHa, SHb, THa, RLa, SLa, TLa, so in Figure 2(a) described later, the rectifying elements RHb, SHb, THb, RLb, SLb, TLb are drawn with dashed lines. Also, in Figure 1, for example, an electromagnetic contactor and an AC reactor are provided on the three-phase AC power supply 2 side of the rectifier 1, but their illustration is omitted.

[0017] The capacitor 10 of the rectifier 1 is provided in the DC link connecting the DC output side of the rectifier 1 and the DC input side of the inverter 15. Here, the capacitor 10 has a smoothing function that smooths the pulsating component of the DC output of the rectifier 1 and a storage function that stores the DC power used by the inverter 15 to generate AC power. Here, for example, an electrolytic capacitor or a film capacitor can be used as the capacitor 10. The configuration and operation of the rectifier 1 will be described in detail later.

[0018] The voltage detection unit 11 detects the voltage value (power supply voltage peak value) input to the rectifier 1 (motor drive device 200) from the three-phase AC power supply 2 and outputs it to the control device 13'. The current detection unit 12 detects the current value input to the rectifier 1 from the three-phase AC power supply 2 and outputs it to the control device 13'. The DC voltage detection unit 14 detects the value of the DC voltage (DC link voltage: voltage across the capacitor 10) output from the rectifier 1 and outputs it to the control device 13'. A DC voltage detection unit can also be provided to detect the value of the DC current between the rectifier 1 and the inverter 15. The control device 13' receives, for example, the output of the voltage detection unit 11 and the output of the current detection unit 12, and determines whether the rectifier 1 is in a power supply state (power supply state) where it converts AC power in the three-phase AC power supply 2 to DC power and outputs it to the DC side, or in a power regeneration state where it converts DC power on the DC side to AC power and outputs it to the three-phase AC power supply 2 side, and controls the switching of the switch elements in the rectifier 1.

[0019] The inverter 15 is connected to the DC output side (capacitor 10) of the rectifier 1 and converts the DC power supplied from the DC link into AC power to drive the motor 3 and outputs it. Here, the inverter 15 only needs to have a configuration that can convert DC power into AC current, and may be, for example, a PWM (Pulse Width Modulation) inverter equipped with a switch element inside. The inverter 15 can be configured as a three-phase bridge circuit when the motor 3 is a three-phase AC motor, and can be configured as a single-phase bridge circuit when the motor 3 is a single-phase motor. Examples of switch elements include FETs (Field effect transistors), IGBTs (Insulated Gate Bipolar Transistors), thyristors, GTO thyristors (Gate Turn Off thyristors), bipolar transistors, etc., but other semiconductor elements may also be used. The motor 3's speed, torque, or rotor position is controlled based on the AC power supplied from the inverter 15. Furthermore, the inverse converter 15 can also convert the AC power regenerated by the motor 3 into DC power and return it to the DC link (capacitor 10) on the DC side, by appropriately controlling the on / off operation of the switching element using PWM.

[0020] Next, we will describe the rectifier 1 in detail. Figure 2 is a diagram illustrating an example of the operation of the rectifier in the motor drive device shown in Figure 1. Figure 2(a) shows the circuit diagram of the rectifier 1, and Figure 2(b) shows a waveform diagram (timing diagram) to explain the operation of the rectifier 1.

[0021] As shown in Figures 1 and 2(a), the rectifier 1 performs power conversion between the AC power in the three-phase AC power supply 2 and the DC power on the DC side. It has three legs, R phase, S phase, and T phase, and each phase leg has an upper arm and a lower arm. The upper arm and lower arm are each provided with a power element consisting of a rectifier element and a switch element connected in parallel to the rectifier element.

[0022] Specifically, the upper R-phase arm is provided with a parallel-connected switch element RHa and a rectifier element RHb, the upper S-phase arm is provided with a parallel-connected switch element Sha and a rectifier element SHb, and the upper T-phase arm is provided with a parallel-connected switch element THa and a rectifier element THb. Similarly, the lower R-phase arm is provided with a parallel-connected switch element RLa and a rectifier element RLb, the lower S-phase arm is provided with a parallel-connected switch element SLa and a rectifier element SLb, and the lower T-phase arm is provided with a parallel-connected switch element TLa and a rectifier element TLb.

[0023] In the three-phase AC power supply 2, the R-phase, S-phase, and T-phase power lines are connected to the connection points of the R-phase upper arm and R-phase lower arm, the S-phase upper arm and S-phase lower arm, and the T-phase upper arm and T-phase lower arm, respectively. Furthermore, the common connection line of the R-phase upper arm, S-phase upper arm, and T-phase upper arm is connected to one end of the capacitor 10, the common connection line of the R-phase lower arm, S-phase lower arm, and T-phase lower arm is connected to the other end of the capacitor 10, and the DC power lines on both ends of the capacitor 10 are connected to the inverter 15. Here, the switching elements RHa, SHa, THa and RLa, SLa, TLa of the upper and lower arms of each phase are switched on / off based on the control signal from the control device 13'.

[0024] First, in the power supply state (powering state) where the AC power in the three-phase AC power supply 2 is converted to DC power and output to the DC side, all the switching elements RHa, SHa, THa, RLa, SLa, and TLa in the rectifier 1 are turned off, and the function of the three-phase bridge circuit is performed by each rectifying element RHb, SHb, THb, RLb, SLb, and TLb. That is, the rectifier 1 converts the AC power in the three-phase AC power supply 2 to DC power and outputs the DC power, which has been smoothed by the capacitor 10, to the inverter 15. Note that the function of the three-phase bridge circuit itself is well known, so its explanation will be omitted.

[0025] Next, in the power regeneration state where the DC power on the DC side is converted to AC power and output to the three-phase AC power supply 2, the switch elements RHa, SHa, THa, RLa, SLa, and TLa in the rectifier 1 are switched based on the control signal from the control device 13', and power regeneration is performed by the on / off operation of each of these switch elements RHa, SHa, THa, RLa, SLa, and TLa.

[0026] Specifically, for example, the value P of power flowing between the three-phase AC power supply 2 and the DC side via the rectifier 1 is calculated based on the outputs of the voltage detection unit 11 and the current detection unit 12. Here, the power supply state and the power regeneration state are recognized based on the magnitude of the power flowing from the three-phase AC power supply 2 to the DC side via the rectifier 1.

[0027] Specifically, in the power regeneration state, each switch element RHa, SHa, THa, RLa, SLa, TLa of the rectifier 1 is switched by a control signal from the control device 13', and power regeneration is performed according to the 120-degree energization method. Here, the control of each switch element in the rectifier 1 is, for example, by detecting the phase of the three-phase AC power supply 2, and each time the voltage of each phase (R phase, S phase, and T phase) of the three-phase AC power supply 2 changes, the switch element on the upper arm of the phase where the phase voltage (power supply voltage peak value) of the three-phase AC power supply 2 is maximum is turned on, and the switch element on the lower arm of the phase where the phase voltage of the three-phase AC power supply 2 is minimum is turned on. Therefore, in power regeneration according to the 120-degree energization method, the ON state of each switch element exists over a phase interval of 120° per cycle (360°) of the three-phase AC power supply 2. In other words, if AC power source 2 is a three-phase AC power source, the duration of each phase (R, S, T) is 360° ÷ 3 = 120°. For example, if AC power source 2 is a four-phase AC power source, the duration of each phase is 360° ÷ 4 = 90°.

[0028] In other words, in the power regeneration state, for example, in the 0°–60° interval (1) of one cycle, only the switch element RHa on the upper arm of the R phase where the phase voltage is maximum and the switch element SLa on the lower arm of the S phase where the phase voltage is minimum are turned on. Furthermore, in the 60°–120° interval (2), only the switch element RHa on the upper arm of the R phase where the phase voltage is maximum and the switch element TLa on the lower arm of the T phase where the phase voltage is minimum are turned on. Then, in the 120°–180° interval (3), only the switch element SHa on the upper arm of the S phase where the phase voltage is maximum and the switch element TLa on the lower arm of the T phase where the phase voltage is minimum are turned on.

[0029] Similarly, in the power regeneration state, in the 180°–240° section (4), only the switch elements Sha and RLa are turned on; in the 240°–300° section (5), only the switch elements THa and RLa are turned on; and in the 300°–360° section (6), only the switch elements THa and SLa are turned on. Here, Figure 2(a) shows the state of the switch elements in section (2), where only the switch element RHa on the upper arm of the R phase where the phase voltage is maximum, and the switch element TLa on the lower arm of the T phase where the phase voltage is minimum are turned on.

[0030] In this way, in the power regeneration state, it becomes possible to regenerate the DC power on the DC side of the rectifier 1 into AC power in the three-phase AC power supply 2. Here, semiconductor elements such as FETs, IGBTs, thyristors, GTO thyristors, and bipolar transistors can be used as the switching elements RHa, SHB, THa, RLa, SLa, and TLa. Diodes can be used as the rectifier elements RHb, SHb, THb, RLb, SLb, and TLb, but it is also possible to use switching elements by controlling the switching so that they function as diodes, for example.

[0031] Figure 3 is a waveform diagram illustrating the challenges of power regeneration in the motor drive device shown in Figure 1, and shows the case where a margin of Δ50V is provided to prevent malfunctions due to voltage detection errors. Specifically, Figure 3 shows the waveform when power regeneration is started when the condition is met that the peak value of the power supply voltage ≥ DC link voltage (DC voltage of rectifier 1) + 50V. In Figure 3, the reference numeral VDC represents the DC link voltage, VR represents the R phase voltage (peak value of the power supply voltage), VS represents the S phase voltage, IR represents the R phase current (inrush current), and IS represents the S phase current.

[0032] As shown in Figure 3, when the condition of power supply voltage peak value ≥ DC link voltage + 50V is met, for example, when power regeneration is initiated, a large inrush current is generated in the R-phase current IR and the S-phase current IS. When such a large inrush current flows, the power loss in the switching elements (switch element RHa on the upper arm of the R-phase and switch element TLa on the lower arm of the T-phase) increases, and the efficiency of power regeneration decreases.

[0033] Hereinafter, embodiments of the motor drive device and the power regeneration method for the motor drive device according to this embodiment will be described in detail with reference to the attached drawings. In each drawing, identical or similar components are denoted by the same or similar reference numerals. Furthermore, the embodiments described below do not limit the technical scope of the invention and the meaning of terms as described in the claims.

[0034] Figure 4 is a circuit block diagram showing one embodiment of the motor drive device according to this embodiment, and shows one embodiment of a motor drive device 100 that receives power from a three-phase AC power supply 2 and drives a three-phase AC motor (M) 3. Here, the motor 3 is not limited to a three-phase AC motor, but may be a motor with other numbers of phases, and may be an induction motor or a synchronous motor. Furthermore, the machines in which the motor 3 is installed include, for example, machine tools, robots, forging machines, injection molding machines, industrial machinery, transportation machinery, various electrical appliances, etc., and the motor drive device 100 of this embodiment is used to drive the motor 3 in such various machines. The three-phase AC power supply 2 may be, for example, a three-phase AC 400V power supply, a three-phase AC 200V power supply, or a three-phase AC 600V power supply, but it does not necessarily have to be three-phase, and therefore, power regeneration is not limited to power regeneration according to the 120-degree energization method.

[0035] As is clear from comparing Figure 4 with the aforementioned Figure 1, the rectifier 1, voltage detection unit 11, current detection unit 12, DC voltage detection unit 14, and inverter 15 in the motor drive device 100 according to this embodiment are substantially the same as those in the motor drive device 200 shown in Figure 1, and a detailed explanation of them will be omitted. Here, in the rectifier 1, the switching elements RHa, SHa, THa, RLa, SLa, TLa and the rectifying elements RHb, SHb, THb, RLb, SLb, TLb are each connected in parallel to form the power elements RHa, RHb, SHa, SHb, THa, THb, RLa, RLb, SLa, SLb, TLa, TLb. Furthermore, since power regeneration by the rectifier 1 is performed based on the on / off operation of the switching elements RHa, SHHa, THa, RLa, SLa, and TLa, the rectifier elements RHb, SHb, THb, RLb, SLb, and TLb are depicted with dashed lines in Figures 7 and 8(a), which will be described later. Also, in Figure 4, for example, an electromagnetic contactor and an AC reactor are provided on the three-phase AC power supply 2 side of the rectifier 1, but their illustrations are omitted.

[0036] As shown in Figure 4, the control device 13 comprises a power phase calculation unit 131, a power calculation unit 132, a state determination unit 133, and a control unit 134. The power phase calculation unit 131 detects, for example, the phases of the R, S, and T phases of the three-phase AC power supply 2 and outputs them to the control unit 134. The power calculation unit 132 receives the outputs of the voltage detection unit 11 and the current detection unit 12, calculates the power (AC power) of the three-phase AC power supply 2, and outputs it to the state determination unit 133.

[0037] The state determination unit 133 determines, based on the power value P calculated by the power calculation unit 132, whether the rectifier 1 is in a power supply state where it converts AC power in the three-phase AC power supply 2 to DC power and outputs it to the DC side, or whether the rectifier 1 is in a power regeneration state where it converts DC power on the DC side to AC power and outputs it to the three-phase AC power supply 2 side. Specifically, the state determination unit 133 recognizes the power supply state and the power regeneration state based on the value of power flowing from the three-phase AC power supply 2 side to the DC side via the rectifier 1. That is, for example, the state determination unit 133 determines that the power supply state is in effect when the power value P calculated by the power calculation unit 132 (supplied power) is equal to or greater than a predetermined threshold (P0), and determines that power regeneration has started (power regeneration state) when the power value P calculated by the power calculation unit 132 is equal to or greater than the predetermined threshold P0. Here, the power calculation unit 132 may be configured to calculate only the DC power on the DC side of the rectifier 1 without calculating the AC power on the AC side of the rectifier 1, or it may be configured to calculate both AC power and DC power. Alternatively, the start of power regeneration (power regeneration state) may be determined when the voltage detected by the DC voltage detection unit 14 rises.

[0038] The control unit 134 controls the on / off operation of each switch element RHa, SHa, THa, RLa, SLa, TLa in the rectifier 1 based on the determination result of the state determination unit 133. Here, the control device 13 (power phase calculation unit 131, power calculation unit 132, state determination unit 133, and control unit 134) may be implemented by a program (software program) executed on a processing unit (MPU, CPU, etc.), but it can also be implemented by hardware such as an electrical circuit. The control of the switch elements by the control device 13 (control unit 134) will be described in detail along with an embodiment of the power regeneration method of the motor drive device according to this embodiment, with reference to Figure 8 and later.

[0039] Figure 5 is a circuit block diagram showing a modified version of the motor drive device shown in Figure 4. As is clear from the comparison between Figure 5 and Figure 4 described above, in the modified version shown in Figure 5, the control device 13 includes not only a power phase calculation unit 131, a power calculation unit 132, a state determination unit 133, and a control unit 134, but also a current interruption determination unit 135 and a receiving unit 136. The receiving unit 136 receives motor power information from the inverter 15 and outputs this information to the state determination unit 133. That is, the state determination unit 133 determines whether the rectifier 1 is in a power supply state or a power regeneration state based on the output information from the receiving unit 136. Here, the information that the receiving unit 136 receives from the inverter 15 is not limited to motor power information, but may be, for example, motor drive information for driving the motor 3.

[0040] The current interruption determination unit 135 determines whether to interrupt the current flowing from the rectifier 1 to the AC power supply 2 if, for example, in a power regeneration state, the current detected by the current detection unit 12 is likely to exceed the rating of the switch elements RHa, Sha, THa, RLa, SLa, TLa, or if it has exceeded the rating. Based on the determination result of the current interruption determination unit 135, the control unit 134 (control device 13) turns off the switch elements RHa, Sha, THa, RLa, SLa, TLa to interrupt the current (regenerative current) flowing from the rectifier 1 to the AC power supply 2.

[0041] Here, the control device 13, for example, after the control unit 134 turns off the switch elements to interrupt the regenerative current flowing from the rectifier 1 to the AC power supply 2, if the current detected by the current detection unit 12 decreases to below a certain threshold, the current interruption determination unit 135 determines that it is not necessary to interrupt the current flowing from the rectifier 1 to the AC power supply 2. Based on the determination result of the current interruption determination unit 135, the control unit 134 turns on the switch elements RHa, SHa, THa, RLa, SLa, TLa again to restart power regeneration so that power regeneration from the rectifier 1 to the AC power supply 2 is possible. If the value of the current is about to exceed the predetermined rating of the switch elements or has exceeded the rating, the same process is repeated, making it possible to perform power regeneration while limiting the upper limit of the current value.

[0042] Figure 6 is a diagram illustrating an example of processing based on the determination result of the current interruption determination unit (135) in the motor drive device shown in Figure 5. Here, Figure 6(a) is a flowchart illustrating an example of processing based on the determination result of the current interruption determination unit, and Figure 6(b) is a diagram showing the relationship between the regenerative current and time at that time. As shown in Figure 6(a), when an example of processing based on the determination result of the current interruption determination unit starts, in step ST1, the switch elements RHa, SHa, THa, RLa, SLa, TLa are turned on to perform power regeneration. Furthermore, the process proceeds to step ST2, where it is determined whether the regenerative current is greater than the first current threshold Ith1.

[0043] In step ST2, if it is determined that the regenerative current is greater than the first current threshold Ith1 (Yes), the process proceeds to step ST3, where the switch elements RHa, SHa, THa, RLa, SLa, TLa are turned off to create a power-off state, and then the process proceeds to step ST4. On the other hand, in step ST2, if it is determined that the regenerative current is not greater than the first current threshold Ith1 (No), the process returns to step ST1, where the switch elements RHa, SHa, THa, RLa, SLa, TLa are turned on and the same process is repeated.

[0044] In step ST4, it is determined whether the regenerative current is smaller than the second current threshold Ith2. In step ST4, if it is determined that the regenerative current is smaller than the second current threshold Ith2 (Yes), the process returns to step ST1, and the switching elements RHa, SHa, THa, RLa, SLa, and TLa are turned on to repeat the same process. On the other hand, in step ST4, if it is determined that the regenerative current is not smaller than the second current threshold Ith2 (No), the process returns to step ST3, and the switching elements RHa, SHa, THa, RLa, SLa, and TLa are turned off to repeat the same process. Here, the first current threshold Ith1 and the second current threshold Ith2 are set such that Ith1 > Ith2.

[0045] As described above, according to an example of the process based on the determination result of the current cutoff determination unit described with reference to FIG. 6(a), for example, a regenerative current with respect to the passage of time as shown in FIG. 6(b) can be obtained. That is, the regenerative current changes in a zigzag manner between the first current threshold Ith1 and the second current threshold Ith2 with the passage of time.

[0046] FIG. 7 is a diagram for explaining an example of the current cutoff operation in the motor drive device shown in FIG. 5. When the rectifier 1 receives regenerative power from the inverter circuit 15 and is in the power regeneration state, it is for explaining the time when the switching element (for example, the switching element RHa in the upper arm of the R phase) is turned off. For example, the regenerative current (reflux current) from the inverter circuit 15 (the high potential side of the DC link voltage) to the R phase of the AC power supply 2 through the switching element RHa is cut off when the switching element RHa is turned off, and a current (reflux current) flows from the low potential side of the DC link voltage to the R phase of the AC power supply 2 through the rectifying element (the rectifying element connected in parallel with the switching element RLa in the lower arm of the R phase), and the regenerative current decreases.

[0047] FIG. 8 is a diagram for explaining an example of a power regeneration method of a motor drive device according to the present embodiment. Here, FIG. 8(a) shows a circuit diagram of the rectifier 1. Similar to FIG. 2(a) described above, only the switch element RHa in the upper arm of the R phase where the phase voltage becomes maximum and the switch element TLa in the lower arm of the T phase where the phase voltage becomes minimum are in the ON state (the state in section (2) of FIG. 2(b)). Note that FIG. 8(b) is a waveform diagram before applying an example of the power regeneration method of the motor drive device according to the present embodiment, that is, a waveform diagram corresponding to the left side portion of FIG. 2(b) described above, and FIG. 8(c) is a waveform diagram after applying an example of the power regeneration method of the motor drive device according to the present embodiment.

[0048] As shown in FIG. 8(c), an example of the power regeneration method of the motor drive device according to the present embodiment determines the start of power regeneration based on the condition that the peak value of the power supply voltage ≤ the DC link voltage, for example, without providing a margin such as Δ50V described with reference to FIG. 3. Thereby, it becomes possible to prevent the generation of a large inrush current when starting power regeneration.

[0049] Further, an example of the power regeneration method of the motor drive device according to the present embodiment adjusts the ON periods of the switch elements RHa and TLa to be narrowed down to 〈120° at a place (period) where the inter-phase voltage is high. That is, the control device 13 in an example of the motor drive device according to the present embodiment adjusts the ON periods of the switch elements RHa and TLa to be narrowed down to 〈120° at a place where the inter-phase voltage is high.

[0050] Specifically, the control unit 134 receives the outputs of the power supply phase calculation unit 131 and the state determination unit 133 and adjusts the 120° energizing width (on period) that turns on the R phase upper arm switch element RHa in the three-phase bridge circuit shown in Figure 8(b) to a shorter energizing width than 120°, excluding the portions at both ends where the potential of the R phase is low, as shown in Figure 8(c). Similarly, the control unit 134 adjusts the 120° energizing width that turns on the T phase lower arm switch element TLa in the three-phase bridge circuit shown in Figure 8(b) to a shorter energizing width than 120°, excluding the portions at both ends where the potential of the T phase is high, as shown in Figure 8(c). As a result, the on period of the switch elements RHa and TLa is narrowed to only the period when the phase-to-phase voltage between the R phase and the S phase is high (the period when the voltage difference between the potential of the R phase and the potential of the S phase is large), and adjusted to 120° or less. The duration for which each switch element is turned on (current-on width: 60° + 2α) can be adjusted based on at least one of the power regeneration power (regenerative power) P [W] and the difference voltage ΔV between the DC link voltage and the peak value of the AC voltage. When applying the 120-degree current-on power regeneration method, α must satisfy the condition of at least 0° ≤ α ≤ 30°.

[0051] As described above, according to one embodiment of the power regeneration method for a motor drive device according to this embodiment, by narrowing the on period of the switch element based on at least one of the regenerative power P and the difference voltage ΔV between the DC link voltage and the peak value of the AC voltage at a point where the inter-phase voltage is high, it becomes possible to prevent the generation of a large inrush current when power regeneration is started, without causing malfunctions in power regeneration due to voltage detection errors, for example. It should be noted that the motor drive device (power regeneration method) according to this embodiment is not limited to a three-phase AC power supply 2 and a three-phase rectifier 1 (three-phase bridge circuit).

[0052] Figure 9 is a diagram illustrating another embodiment of the power regeneration method for a motor drive device according to this embodiment, and shows how the ON periods of the switch elements of the preceding and succeeding phases overlap, which is a prerequisite for the power regeneration method of this embodiment. Figure 9 shows a period corresponding to the state of section (2) in Figure 2(b) described above, and shows how the ON period of the switch element TLa on the lower arm of the succeeding phase T phase overlaps with the ON period of the ON period of the ON period of the ON period of the R phase upper arm of the preceding phase R phase by β (first set value). Specifically, in a 120-degree energization method using a 50 Hz three-phase power supply, β can be set to, for example, about 10° (approximately 556 μsec.) to improve the current connection and improve the efficiency of power regeneration. Note that β must satisfy the condition of at least 0° ≤ β.

[0053] In this embodiment, another embodiment of the power regeneration method for the motor drive device is to adjust the duration (length) of β over which the on-periods of the switch elements of the preceding and succeeding phases overlap. The on-period β of the switch elements that overlap in consecutive preceding and succeeding phases can be adjusted based on at least one of the regenerative power P and the difference voltage ΔV between the DC link voltage and the peak value of the AC voltage. That is, the control device 13 in one embodiment of the motor drive device according to this embodiment adjusts the on-period β of the switch elements RHa and TLa that overlap in consecutive preceding and succeeding phases R and T. The first set value (overlap width) β is not limited to being set before the on-period Φ of 120° (left side in the waveform diagram), but may also be set after the on-period Φ (right side in the waveform diagram), or both before and after the on-period Φ (both sides).

[0054] Thus, according to another embodiment of the power regeneration method for a motor drive device according to this embodiment, by adjusting the on-period β over which the switch elements are covered in consecutive preceding and succeeding phases based on at least one of the regenerative power P and the difference voltage ΔV between the DC link voltage and the peak value of the AC voltage, it becomes possible to maintain high power regeneration efficiency regardless of the magnitude of the regenerative power (output). It goes without saying that the power regeneration method of this embodiment is not limited to controlling the on / off operation of each switch element in a three-phase bridge circuit.

[0055] Figure 10 is a diagram illustrating an embodiment of the power regeneration method performed by the motor drive device shown in Figure 4. Figure 10(a) is a graph showing the relationship between the on-period Φ[°] of the switch element and the regenerated power P[W]. Here, Figures 10(b) and 10(c) illustrate one embodiment of the power regeneration method of the motor drive device according to this embodiment. Figure 10(b) is a waveform diagram corresponding to Figure 8(c) described above, and Figure 10(c) is a waveform diagram corresponding to Figure 8(b) described above. Figure 10(d) illustrates another embodiment of the power regeneration method of the motor drive device according to this embodiment and is a waveform diagram corresponding to Figure 9 described above.

[0056] As shown in Figure 10(a), the motor drive device 100 shown in Figure 4 adjusts α (second setting value) during the period from the minimum value Φmin (second setting on period = 60° + 2α) to 120° for the on period Φ of the switch element. Here, the value of α is set to, for example, 0° < α < 30°. Then, the control device 13 (control unit 134) adjusts the on period Φ(α: 60° + 2α) of the switch element so that the value of α(2α) also increases as the regenerative power P increases, for example, in proportion to the increasing regenerative power P. That is, the control unit 134 receives the output of the power supply phase calculation unit 131 and the state determination unit 133 (power calculation unit 132) and controls, for example, the energizing width that turns on the switch element RHa of the upper arm of the R phase in the three-phase bridge circuit to 60° + 2α, which is shorter than 120°. Here, the value of α in the current-passing width of 60° + 2α is adjusted to increase as the regenerative power P increases. The current-passing widths for turning on the other switch elements SHa, THa, RLa, SLa, and TLa are adjusted in the same way as the current-passing width for turning on the switch element RHa.

[0057] Furthermore, the motor drive device 100 shown in Figure 4 adjusts β (first set value) during the period from 120° to the maximum value Φmax (first set on period = 120° + β: first set on period) of the on period Φ of the switch element. Here, the value of β is set to a range in which the regenerative power P does not exceed the threshold Pth, for example, set to approximately 0° < β < 30°. Then, the control unit 134 (control device 13) adjusts the on period Φ(β: 120° + β) of the switch element so that the value of β also increases as the regenerative power P increases, for example, in proportion to the increasing regenerative power P. That is, the control unit 134 receives the output of the power supply phase calculation unit 131 and the state determination unit 133 (power calculation unit 132) and controls, for example, the energizing width that turns on the switch element RHa of the upper arm of the R phase in the three-phase bridge circuit to 120° + β, which is longer than 120°. Here, the value of β in the energizing width of 120° + β is adjusted to increase as the regenerative power P increases. The energizing widths for turning on the other switch elements SHa, THa, RLa, SLa, and TLa are adjusted in the same way as the energizing width for turning on the switch element RHa. In the above, in Figure 10(a), the length Φ of the on period is depicted to increase linearly as the regenerative power P increases throughout all adjustment periods of α and β, but it goes without saying that it does not necessarily have to change linearly. This is also true in Figures 12(a), 13(a), and 14(a) which will be described later, and it is also possible to change it nonlinearly in the α adjustment period and β adjustment period in Figures 15(a) and 16(b).

[0058] As explained with reference to Figures 10(a) and 10(b), according to one embodiment of the power regeneration method for a motor drive device according to this embodiment, it is possible to prevent the occurrence of a large inrush current when power regeneration is started without causing malfunctions in power regeneration due to voltage detection errors. Furthermore, as explained with reference to Figures 10(a) and 10(d), according to another embodiment of the power regeneration method for a motor drive device according to this embodiment, it is possible to maintain high power regeneration efficiency regardless of the magnitude of the regenerated power.

[0059] Figure 11 is a waveform diagram illustrating the current limit operation in an embodiment of the motor drive device according to the present embodiment shown in Figure 10, and shows the relationship between the phase performing the current limit (cutoff) operation and the regenerative phase. As explained with reference to Figures 10(a) and 10(b), for example, when the switch elements of each phase (R, S, T phases) in a three-phase bridge circuit are operating with a current carrying width of 60° + 2α, if the current exceeds the rating of the switch element, the connection between the rectifier 1 and the three-phase AC power supply 2 is forcibly cut off in the hatched portion of the switching pattern in order to protect the switch element.

[0060] Here, the forced disconnection of the rectifier 1 and the three-phase AC power supply 2 described above is performed, for example, when the current detection unit 12 detects the current (regenerative current) flowing between the rectifier 1 and the three-phase AC power supply 2 and the current is likely to exceed or exceeds the predetermined rating of the switch element. Furthermore, after the disconnection of the rectifier 1 and the three-phase AC power supply 2, the current decreases, and if the current value falls below a certain value, the switch element is turned on again to restart power regeneration. Then, if the current is likely to exceed or exceeds the predetermined rating of the switch element, the above process is repeated, allowing power regeneration to be performed while limiting the upper limit of the current.

[0061] Figure 12 is a diagram illustrating an example of power regeneration operation in one embodiment of the motor drive device according to this embodiment. Figure 12(a) shows the relationship between the ON period Φ of the switch element and the regenerated power P, and is a graph corresponding to Figure 10(a) described above. Figure 12(b) is a flowchart illustrating the process in an example of power regeneration operation in one embodiment of the motor drive device according to this embodiment.

[0062] As described above, Figure 12(a) is a graph corresponding to Figure 10(a), and a detailed explanation thereof has already been given with reference to Figure 10(a), so it will be omitted here. As shown in Figure 12(b), when the processing of an example of power regeneration operation in one embodiment of the motor drive device according to this embodiment starts, in step ST11 it is determined whether it is in a power regeneration state, and if it is determined to be in a power regeneration state (Yes), the process proceeds to step ST12, where it is determined whether the regenerated power P is greater than the threshold Pth.

[0063] In step ST12, if it is determined that the regenerated power P is greater than the threshold Pth (Yes), the process proceeds to step ST13, where the on-period of the switch element is set to Φ = Φmax, and the on / off operation of the switch element is controlled (switching control). Therefore, in the region where the regenerated power P satisfies P > Pth, that is, in Figure 12(a), in the region where the regenerated power P on the horizontal axis is to the right of the threshold Pth, each switch element is switched with an on-period of Φ = Φmax = 120° + β. The value of the overlap width (first set value) β will be described in detail later with reference to Figure 18.

[0064] On the other hand, if it is determined in step ST12 that the regenerated power P is not greater than the threshold Pth (No), the process proceeds to step ST14, where the on-period Φ = f(P) > 60° + 2α of the switch element is used to control the on / off operation of the switch element. If it is determined in step ST11 that the power is not being regenerated (No), the process proceeds to step ST15, where the on-control of the switch element is stopped, that is, the switch element is fixed in the off state.

[0065] In Figures 12(a) and 12(b), the power P can be calculated by the power calculation unit 132 based on the output of the voltage detection unit 11 and the current detection unit 12 provided on the three-phase AC power supply 2 side. However, it is also possible to use power calculated from the output of the DC voltage detection unit 14 and the DC current detection unit (not shown) provided on the DC output side (DC link side) of the rectifier 1. This is also true for other embodiments and modifications.

[0066] Figure 13 is a diagram illustrating another example of power regeneration operation in one embodiment of the motor drive device according to this embodiment. Here, Figure 13(a) shows a graph of the relationship between the ON period Φ of the switch element and the DC link voltage ΔV, and Figure 13(b) shows a flowchart illustrating the processing of another example of power regeneration operation in one embodiment of the motor drive device according to this embodiment. That is, in the example of power regeneration operation described with reference to Figure 12, α (second set value) and β (first set value) were adjusted based on the regenerated power P, but in the other example of power regeneration operation shown in Figure 13, α and β are adjusted based on the DC link voltage ΔV.

[0067] As shown in Figure 13(a), the motor drive device 100 shown in Figure 4 adjusts α during the period from the minimum value Φmin (second set on period = 60° + 2α) to 120° when the on period Φ of the switch element is at its minimum value, and adjusts β during the period from 120° to the maximum value Φmax (first set on period = 120° + β) when the on period Φ of the switch element is at its maximum value, Φmax (first set on period = 120° + β). That is, the control unit 134 (control device 13) controls the power supply phase calculation unit 131 and the state determination unit 133 (DC voltage detection unit). The output of the output unit 14) is received, and for example, the energizing width that turns on the R phase upper arm switch element RHa in the three-phase bridge circuit is controlled to be shorter than 120°, set to 60° + 2α. Here, the value of α in the energizing width 60° + 2α is adjusted to increase as the DC link voltage ΔV increases. The energizing widths that turn on the other switch elements SHa, THa, RLa, SLa, TLa are adjusted in the same way as the energizing width that turns on the switch element RHa.

[0068] Furthermore, the control unit 134 receives the outputs of the power supply phase calculation unit 131 and the state determination unit 133 (DC voltage detection unit 14), and controls, for example, the energizing width that turns on the switch element RHa on the upper arm of the R phase in the three-phase bridge circuit to 120° + β, which is longer than 120°. Here, the value of β in the energizing width 120° + β is adjusted to increase as the DC link voltage ΔV increases. The energizing widths that turn on the other switch elements SHa, THa, RLa, SLa, TLa are adjusted in the same way as the energizing width that turns on the switch element RHa.

[0069] As shown in Figure 13(b), when the processing of another example of the power regeneration operation in one embodiment of the motor drive device according to this embodiment starts, in step ST21 it is determined whether the power is in a regeneration state. If it is determined that the power is in a regeneration state (Yes), the process proceeds to step ST22, where it is determined whether the DC link voltage ΔV is greater than the threshold Vth. In step ST22, if it is determined that the DC link voltage ΔV is greater than the threshold Vth (Yes), the process proceeds to step ST23, where the on-period of the switch element is set to Φ = Φmax and the on / off operation of the switch element is controlled.

[0070] On the other hand, if it is determined in step ST22 that the DC link voltage ΔV is not greater than the threshold Vth (No), the process proceeds to step ST24, where the on-period Φ = f(P) > 60° + 2α of the switch element is set to control the on / off operation of the switch element. If it is determined in step ST21 that the power regeneration state is not active (No), the process proceeds to step ST25, where the on-control of the switch element is stopped.

[0071] Figure 14 illustrates a modified version of the power regeneration operation described with reference to Figure 13. Figure 14(a) shows a graph of the relationship between the on-period Φ of the switch element and the DC link voltage ΔV, corresponding to Figure 13(a) described above. Figure 14(b) shows a flowchart illustrating the processing of the modified version of the power regeneration operation described with reference to Figure 13. Note that Figure 14(a) corresponds to Figure 13(a) described above, and its explanation is omitted.

[0072] As shown in Figure 14(b), when the modified power regeneration operation described with reference to Figure 13 starts, in step ST31 it is determined whether the power is in a regeneration state. If it is determined that the power is in a regeneration state (Yes), the process proceeds to step ST32, where the on / off operation of the switch element is controlled with an on period Φ = 60° + 2α, and then the process proceeds to step ST33.

[0073] In step ST33, it is determined whether the DC link voltage ΔV is less than or equal to the minimum voltage Vmin, and / or whether the regenerative power P is less than or equal to the threshold P0'. That is, in step ST33, it is determined whether both the determination that the DC link voltage ΔV is less than or equal to the minimum voltage Vmin and the determination that the regenerative power P is less than or equal to the threshold P0' are true (Yes), or whether one of the determinations that the DC link voltage ΔV is less than or equal to the minimum voltage Vmin and the determination that the regenerative power P is less than or equal to the threshold P0' are true (Yes). Therefore, in step ST33, it is determined whether at least one of the determinations that the DC link voltage ΔV is less than or equal to the minimum voltage Vmin and the determination that the regenerative power P is less than or equal to the threshold P0' is true (Yes). The determination conditions in step ST33 are determined, for example, based on the configuration of the motor drive system to which one embodiment of the motor drive device according to this embodiment is applied, or the characteristics required of the motor drive system.

[0074] In step ST33, if it is determined that the judgment condition is not met (No), the process proceeds to step ST34, where the on / off operation of the switch element is controlled as Φ = 60° + 2α + f(P) + f(ΔV), and the processing of steps ST33 and ST34 is repeated until it is determined in step ST33 that the judgment condition is met (Yes). On the other hand, if it is determined in step ST33 that the judgment condition is met (Yes), the process proceeds to step ST35, where the on control of the switch element is stopped, and the process returns to step ST31.

[0075] Furthermore, the modified examples described with reference to Figure 14 are not limited to their application to other examples of the power regeneration operation in one embodiment of the motor drive device according to the present embodiment shown in Figure 13, but can be appropriately applied to various embodiments of the motor drive device according to the embodiment.

[0076] Figure 15 is a diagram illustrating an example of power regeneration operation in another embodiment of the motor drive device according to this embodiment. Here, Figure 15(a) shows a graph of the relationship between the ON period Φ of the switch element and the regenerated power P, and Figure 15(b) shows a flowchart illustrating the processing of an example of power regeneration operation in another embodiment of the motor drive device according to this embodiment. Specifically, in Figure 15(a), in the graph shown in Figure 12(a) above, one threshold Pth is divided into three thresholds Pth1, Pth2, and Pth3 for processing.

[0077] As shown in Figure 15(b), when an example of power regeneration operation in another embodiment of the motor drive device according to this embodiment starts, in step ST41 it is determined whether the power is in a regeneration state. If it is determined that the power is in a regeneration state (Yes), the process proceeds to step ST42, where it is determined whether the power P is greater than the first threshold Pth1. In step ST42, if it is determined that the power P is greater than the first threshold Pth1 (Yes), the process proceeds to step ST43, where it is determined whether the power P is greater than the second threshold Pth2.

[0078] In step ST43, if it is determined that the power P is greater than the second threshold Pth2 (Yes), the process proceeds to step ST44 to determine whether the power P is greater than the third threshold Pth3. In step ST44, if it is determined that the power P is greater than the third threshold Pth3 (Yes), the process proceeds to step ST45 to control the on / off operation of the switch element by setting the on-period Φ = Φmax. Also, in step ST44, if it is determined that the power P is not greater than the third threshold Pth3 (No), the process proceeds to step ST46 to control the on / off operation of the switch element by setting the on-period Φ = f(P) > 120°.

[0079] On the other hand, if it is determined in step ST43 that the power P is not greater than the second threshold Pth2 (No), the process proceeds to step ST47, where the on-period Φ of the switch element is set to 120° and the on / off operation of the switch element is controlled. Furthermore, if it is determined in step ST42 that the power P is not greater than the first threshold Pth1 (No), the process proceeds to step ST48, where the on-period Φ of the switch element is set to f(P) > 60° + 2α and the on / off operation of the switch element is controlled. If it is determined in step ST41 that the power regeneration state is not active (No), the process proceeds to step ST49, where the on-control of the switch element is stopped.

[0080] Thus, according to an example of power regeneration operation in another embodiment of the motor drive device according to this embodiment, compared to the case of one threshold Pth described with reference to Figure 12, by controlling the on / off operation of each switch element based on three thresholds Pth1, Pth2, and Pth3, it is possible to perform fine control, for example, by adjusting the current supply width only when the output is extremely small or large, based on a current supply width of 120°.

[0081] Figure 16 is a diagram illustrating a modified version of the power regeneration operation shown in Figure 15. As is clear from comparing Figure 16 with Figure 15(a) described above, in the example of power regeneration operation in another embodiment of the motor drive device according to this embodiment shown in Figure 15, the regenerated power P is processed based on three thresholds Pth1, Pth2, and Pth3, whereas in the modified version shown in Figure 16, the regenerated power P is processed based on two thresholds Pth1 and Pth2. In this modified version shown in Figure 16, the energizing width adjustment for an on-period Φ of 120° or less is adjusted by the first function Φ = f(P), and the energizing width adjustment for an on-period Φ of 120° or more is adjusted by the second function Φ = g(P), thereby adjusting the optimal on-period Φ in each region.

[0082] Thus, by processing the regenerative power P based on thresholds, and dividing the number of thresholds into multiple parts, it becomes possible to adjust the optimal on-period Φ in each region divided by the multiple thresholds, for example, by using a function suitable for that region.

[0083] Figure 17 is a waveform diagram illustrating a modified example of the power regeneration method for the motor drive device described with reference to Figure 10. Here, Figure 17(a) is a waveform diagram corresponding to Figures 10(b) and 8(c) described above, Figure 18(b) is a waveform diagram corresponding to Figures 10(c) and 8(b) described above, and Figure 18(c) is a waveform diagram corresponding to Figure 10(d) described above. However, in the waveform diagram shown in Figure 18(c), for example, the end (off) timing of the on period Φ (=Φmax = 120° + β) of the switch element RHa is made earlier (shorter) by Y (third set value).

[0084] In this way, by ending the first set ON period (Φmax) earlier by the third set value Y, it becomes possible to stabilize the operation of the rectifier 1 that performs power regeneration. Specifically, for example, when the timing of the phase detection signal change coincides with the timing of the ON / OFF operation (switching) of the power regeneration switch element, there is a risk that a spike-like distortion voltage will be generated due to the ON / OFF operation of the power regeneration switch element. In such cases, by ending the ON period Φ earlier by the third set value Y, it is possible to avoid the problem of misdetecting the power phase due to the influence of the spike-like distortion voltage. In other words, by ending the ON period Φ earlier by the third set value Y, it becomes possible to avoid the occurrence of unstable operation such as mistakenly turning on the power regeneration switch element.

[0085] In the above, each embodiment of this embodiment is not limited to controlling the on / off operation of each switch element RHa, SHa, THa, RLa, SLa, TLa in a 120-degree energization type power regeneration (three-phase bridge circuit). That is, when the AC power supply 2 is a three-phase AC power supply, 360° ÷ 3 = 120° is the period for each phase (R, S, T), but when the AC power supply 2 is a four-phase AC power supply, for example, 360° ÷ 4 = 90° is the period for each phase. Therefore, "Φmax = 120° + β" and "Φmin = 60° + 2α" in the three-phase case described above become "Φmax = 90° + β" and "Φmin = 45° + 2α" in the four-phase case, for example. Thus, the motor drive device (power regeneration method) of this embodiment is not limited to the application of a three-phase AC power supply 2 and a three-phase rectifier 1 (three-phase bridge circuit).

[0086] Figure 18 is a diagram illustrating the value of β in the power regeneration method of the motor drive device according to this embodiment. Here, Figure 18(a) shows the relationship between β (cover width) and electromagnetic strain rate during the ON period of each switch element, and Figures 18(b) to 18(e) show examples of simulation results of the regenerative current waveform, respectively.

[0087] Incidentally, the value of β is set to, for example, 10° (approximately 556 μsec.) and 15° (approximately 833 μsec.), but this value of β is set to an appropriate value based on conditions such as the reactor value and power supply impedance of the system to which the motor drive device (rectifier) ​​is applied. Specifically, for example, the waveform distortion rate of the regenerative current was confirmed by performing a simulation under the following conditions: ・Three-phase AC power supply 200V, 50Hz ・20kW rated converter (rectifier, motor drive device) ・Reactor 0.118mH (%Z = 2%, reactor value for 20kW) ・Power supply impedance 2 patterns: %Z = 1%, 0.1% ・Regenerative power 2 patterns: 20kW (continuous rating), 54kW (short-time maximum rating)

[0088] In other words, the current distortion rate of the regenerative current was checked when β was changed using the above simulation conditions, and the results shown in Figures 18(a) to 18(e) were obtained. Summarizing these results, the following insights were gained: - For continuous ratings, it is preferable not to perform switching overlay (overlapping the on periods of the switching elements of the phases before and after switching) (β = 0° results in a small waveform distortion rate). - For short-time maximum ratings, it is preferable to perform switching overlay. - The optimal overlay width (first setting value) β that minimizes current distortion at short-time maximum ratings is approximately 10° when the power supply %Z = 0.1% and approximately 15° when %Z = 1%. In reality, it is thought that various conditions other than those shown as simulation conditions also have a complex influence.

[0089] Thus, it is preferable to set the value of β (1st setting value) to approximately 0° < β < 30°. Also, as mentioned above, it is preferable to set the value of α (2nd setting value) to approximately 0° < α < 30°. Needless to say, these values ​​of β and α may change depending on the configuration of the system to which the motor drive device according to this embodiment is applied, the characteristics required of the system, or various conditions such as power supply impedance and reactor value.

[0090] As described above, the power regeneration method for the motor drive device according to this embodiment can also be implemented, for example, as a power regeneration program executed by the arithmetic processing unit (MPU, CPU, etc.) of the control device 13. This power regeneration program for the motor drive device may be provided by recording it on a computer-readable non-temporary recording medium or non-volatile semiconductor memory, or it may be provided via wired or wireless connection. Here, examples of computer-readable non-temporary recording media include optical discs such as CD-ROMs (Compact Disc Read Only Memory) and DVD-ROMs, or hard disk drives. Examples of non-volatile semiconductor memory include PROMs (Programmable Read Only Memory) and flash memory. Furthermore, for distribution from the server device, provision via a wired or wireless LAN (Local Area Network) or WAN such as the Internet is possible. The program (computer program) may also be provided in the form of a computer program product.

[0091] As described in detail above, the motor drive device and the power regeneration method for the motor drive device according to this embodiment make it possible to suppress inrush current during power regeneration and maintain high power regeneration efficiency regardless of the output level.

[0092] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. Furthermore, these embodiments can be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

[0093] With respect to the above embodiments and modifications, the following additional notes are disclosed. [Addendum 1] A motor drive device (100) that drives a motor (3) based on the DC power, comprising: a rectifier (1) that performs power conversion between AC power in a multiphase AC power source (2) and DC power on the DC side, including a plurality of rectifier elements (RHb, SHb, THb, RLb, SLb, TLb) that perform rectification operation, a plurality of switch elements (RHa, SHa, THa, RLa, SLa, TLa) that are provided in parallel with the rectifier elements and perform on / off operation, and a capacitor (10); and a control device (13) that controls the on / off operation of the plurality of switch elements (RHa, SHa, THa, RLa, SLa, TLa) based on the DC power, wherein the control device (13) is A motor drive device (100) defines a first set on period (Φmax) as the period (120°) of each phase (R, S, T) of the AC power supply (2) plus a first set value (β), and controls the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) by adjusting the length of the first set on period (Φmax) in the power regeneration state. [Note 2] The motor drive device (100) described in Note 1, wherein the control device (13) defines a period (60° + 2α) obtained by adding a second set value (α) to half the period of each phase (R, S, T) of the AC power supply (2) centered on the peak of each phase (R, S, T), and controls the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) by adjusting the length of the second set on period (Φmin) in the power regeneration state. [Note 3] The motor drive device (100) described in Note 1 or Note 2, wherein the control device (13) controls the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) so that the first set on period (Φmax) ends earlier by a third set value (Y) in the power regeneration state.[Note 4] The motor drive device (100) according to any one of Notes 1 to 3, comprising: a control device (13) comprising: a power phase calculation unit (131) that calculates the phase of each phase (R, S, T) in the AC power supply (2); a power calculation unit (132) that calculates the power in the AC power supply (2); a state determination unit (133) that determines whether the rectifier (1) is in the power supply state or the power regeneration state based on the output of the power calculation unit (132); and a control unit (134) that receives the output of the power phase calculation unit (131) and the output of the state determination unit (133) and controls the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa). [Note 5] The motor drive device (100) described in Note 4, wherein the control unit (134) controls the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) based on the output of the power phase calculation unit (131) and the output of the power calculation unit (132) in the power regeneration state. [Note 6] The motor drive device according to Note 4 or Note 5, wherein the state determination unit (133) determines that the power supply state is when the output (P) of the power calculation unit (132) is equal to or greater than a predetermined threshold (P0), and determines that the power regeneration state is when the output (P) of the power calculation unit (132) is less than the predetermined threshold (P0), and the control unit (134) controls the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) to regenerate power when the state determination unit (133) determines that the power regeneration state is, and stops the operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) to supply power when the state determination unit (133) determines that the power supply state is[Note 7] The motor drive device (100) described in Note 6, wherein the predetermined threshold (P0) is set as a plurality of thresholds (Pth1, Pth2, Pth3) of different predetermined power values ​​with respect to the power output from the power calculation unit (132), and the control unit (134) controls the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) based on the plurality of thresholds (Pth1, Pth2, Pth3). [Note 8] The motor drive device (100) according to any one of Notes 1 to 3, further comprising a DC voltage detection unit (14) for detecting the DC voltage on the DC side, the control device (13) comprising: a power phase calculation unit (131) for calculating the phases of each phase (R, S, T) in the AC power supply (2); a state determination unit (133) for determining whether the rectifier (1) is in the power supply state or the power regeneration state based on the output of the DC voltage detection unit (14); and a control unit (134) for receiving the output of the power phase calculation unit (131) and the output of the state determination unit (133) and controlling the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa). [Note 9] The motor drive device (100) described in Note 8, wherein the control unit (134) controls the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) based on the output of the power phase calculation unit (131) and the output of the DC voltage detection unit (14) in the power regeneration state. [Note 10] The motor drive device (100) as described in Note 8 or Note 9, wherein the control unit (134) controls the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) to regenerate power when the output of the DC voltage detection unit (14) exceeds a predetermined threshold (Vth) and the state determination unit (133) determines that the power regeneration state is in place, and stops the operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) to supply power when the output of the DC voltage detection unit (14) becomes less than the threshold (Vth) and the state determination unit (133) determines that the power supply state is in place.[Note 11] The switching elements (RHa, Sha, THa, RLa, SLa, TLa) and the rectifying elements (RHb, SHb, THb, RLb, SLb, TLa) are each connected in parallel to form a power element (RHa, RHb, Sha, SHb, THa, THb, RLa, RLb, SLa, SLb, TLa, TLa), the AC power supply is a three-phase AC power supply (2) that outputs three-phase (R, S, T) AC waveforms, the rectifier includes an upper arm and a lower arm provided for the three phases (R, S, T) from the three-phase AC power supply (2), and the power elements (RHa, RHb, Sha, SHb, THa, THb, RLa, RLb, SLa, SLb, TLa, TLa) are each provided on the upper arm and the lower arm of the three phases (R, S, T). A motor drive device (100) according to any one of the appendices 1 to 10. [Appendix 12] A motor drive device (100) according to any one of the appendices 1 to 11, further comprising: a voltage detection unit (11) for detecting the voltage of each phase (R, S, T) of the AC power supply (2); a current detection unit (12) for detecting the current of each phase (R, S, T) of the AC power supply (2); and a reverse converter (15) for receiving the DC power from the rectifier (1), converting it to AC power, and controlling the drive of the motor (3). [Note 13] The motor drive device (100) described in Note 12, wherein, in the power regeneration state, if the current detected by the current detection unit (12) is likely to exceed the rating of the switch element (RHa, Sha, THa, RLa, SLa, TLa) or has exceeded the rating, the control device (13) determines whether to interrupt the current flowing from the rectifier (1) to the AC power supply (2), and if the value of the current decreases to or below a certain value after interruption, the switch element (RHa, Sha, THa, RLa, SLa, TLa) is turned on again to restart power regeneration, and if the value of the current is likely to exceed or has exceeded the predetermined rating of the switch element (RHa, Sha, THa, RLa, SLa, TLa), the same process is repeated, thereby limiting the upper limit of the value of the current while performing power regeneration.[Note 14] The control device (13) comprises: a power phase calculation unit (131) that calculates the phases of each phase (R, S, T) in the AC power supply (2); an inverse converter (15) that receives the DC power from the rectifier (1), converts it to AC power, and controls the drive of the motor (3); a receiving unit (136) that receives motor power information from the inverse converter (15); a state determination unit (133) that determines whether the rectifier (1) is in the power supply state or the power regeneration state based on the output information from the receiving unit (136); and a control unit (134) that receives the output of the power phase calculation unit (131), the output of the state determination unit (133), and the output information from the receiving unit (136), and controls the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa). A motor drive device (100) as described in any one of the appendices 1 to 13. [Appendix 15] A power regeneration method for a motor drive device (100) comprising a rectifier (1) that performs power conversion between AC power in a multi-phase AC power source (2) and DC power on the DC side, wherein the period obtained by adding a first set value (β) to the period (120°) of each phase (R, S, T) of the AC power source (2) (120°) is defined as the first set on period (Φmax), and it is determined whether to enter a power supply state or a power regeneration state. A power regeneration method comprising controlling the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa) by adjusting the length of the first set on period (Φmax) in the power regeneration state.[Note 16] Furthermore, the power regeneration method described in Note 15, wherein the second set on period (Φmin) is defined as a period (60° + 2α) obtained by adding a second set value (α) to half the period of each phase (R, S, T) of the AC power supply (2) centered on the peak of each phase (R, S, T), and the length of the second set on period (Φmin) is adjusted in the power regeneration state to control the on / off operation of the plurality of switch elements (RHa, Sha, THa, RLa, SLa, TLa). [Note 17] A power regeneration program for a motor drive device (100) comprising a rectifier (1) that performs power conversion between AC power in a multi-phase AC power source (2) and DC power on the DC side, the rectifier (1) which includes a plurality of rectifier elements (RHb, SHb, THb, RLb, SLb, TLb) that perform rectification operation, a plurality of switch elements (RHa, SHa, THa, RLa, SLa, TLa) that are provided in parallel with the rectifier elements and perform on / off operation, and a capacitor (10), wherein the rectifier (1) performs power conversion between AC power in a multi-phase AC power source (2) and DC power on the DC side, the power regeneration program which causes a processing unit to execute the power regeneration method described in Note 15 or Note 16.

[0094] 1 Rectifier 2 AC power supply (three-phase AC power supply) 3 Motor 10 Capacitor (DC link capacitor) 11 Voltage detection unit 12 Current detection unit 13, 13' Control device 14 DC voltage detection unit 15 Inverter converter 100, 200 Motor drive device 131 Power supply phase calculation unit 132 Power calculation unit 133 State determination unit 134 Control unit 135 Current interruption determination unit 136 Receiving unit RHa, Sha, THa Switch element (upper arm) RHb, SHb, THb Rectifier element (upper arm) RLa, SLa, TLa Switch element (lower arm) RLb, SLb, TLb Rectifier element (lower arm) Y Third setting value α Second setting value β First setting value (overlap width) Φmax First setting ON period (120° + β) Φmin Second setting ON period (60° + 2α)

Claims

1. A motor drive device that drives a motor based on DC power, comprising: a rectifier that performs a rectifying operation, a plurality of rectifying elements that perform a rectifying operation, a plurality of switching elements that are provided in parallel with the rectifying elements and perform an on / off operation, and a capacitor, and which performs power conversion between AC power in a multiphase AC power source and DC power on the DC side; and a control device that controls the on / off operation of the plurality of switching elements based on a determination result of whether the rectifier is in a power supply state or a power regeneration state, wherein the control device defines a period obtained by adding a first set value to the period of each phase of the AC power source as a first set on period, and in the power regeneration state, controls the on / off operation of the plurality of switching elements by adjusting the length of the first set on period.

2. The motor drive device according to claim 1, wherein the control device defines a second set on period as a period obtained by adding a second set value to half the period of each phase, centered on the peak of each phase of the AC power supply, and controls the on / off operation of the plurality of switch elements by adjusting the length of the second set on period in the power regeneration state.

3. The motor drive device according to claim 1 or claim 2, wherein the control device controls the on / off operation of the plurality of switch elements so that the first set on period ends earlier by a third set value in the power regeneration state.

4. The motor drive device according to any one of claims 1 to 3, wherein the control device comprises: a power phase calculation unit that calculates the phase of each phase in the AC power supply; a power calculation unit that calculates the power in the AC power supply; a state determination unit that determines whether the rectifier is in the power supply state or the power regeneration state based on the output of the power calculation unit; and a control unit that receives the output of the power phase calculation unit and the output of the state determination unit and controls the on / off operation of the plurality of switch elements.

5. The motor drive device according to claim 4, wherein the control unit controls the on / off operation of the plurality of switch elements based on the output of the power phase calculation unit and the output of the power calculation unit when the power is being regenerated.

6. The motor drive device according to claim 4 or 5, wherein the state determination unit determines that the power supply state is in effect when the output of the power calculation unit is greater than or equal to a predetermined threshold, determines that the power regeneration state is in effect when the output of the power calculation unit is zero or less than the predetermined threshold, and the control unit controls the on / off operation of the plurality of switch elements to regenerate power when the state determination unit determines that the power regeneration state is in effect, and stops the operation of the plurality of switch elements to supply power when the state determination unit determines that the power supply state is in effect.

7. The motor drive device according to claim 6, wherein the thresholds are set as a plurality of thresholds of different predetermined power values ​​with respect to the power output from the power calculation unit, and the control unit controls the on / off operation of the plurality of switch elements based on the plurality of thresholds.

8. The motor drive device according to any one of claims 1 to 3, further comprising a DC voltage detection unit for detecting the DC voltage on the DC side, the control device comprising: a power phase calculation unit for calculating the phase of each phase in the AC power supply; a state determination unit for determining whether the rectifier is in the power supply state or the power regeneration state based on the output of the DC voltage detection unit; and a control unit that receives the output of the power phase calculation unit and the output of the state determination unit and controls the on / off operation of the plurality of switch elements.

9. The motor drive device according to claim 8, wherein the control unit controls the on / off operation of the plurality of switch elements based on the output of the power phase calculation unit and the output of the DC voltage detection unit when the power supply is in the regenerative state.

10. The motor drive device according to any one of claims 1 to 9, wherein, in the power regeneration state, if the current detected by the current detection unit is likely to exceed the rating of the switch element or has exceeded the rating, the control device cuts off the current flowing from the rectifier to the AC power supply, and if the value of the current decreases to or below a certain value after the cutoff, it turns on the switch element again to restart power regeneration, and if the value of the current is likely to exceed or has exceeded a predetermined rating of the switch element, it repeats the same process, thereby limiting the upper limit of the value of the current while performing power regeneration.

11. A power regeneration method for a motor drive device comprising a rectifier that performs power conversion between AC power in a multi-phase AC power source and DC power on a DC side, the rectifier including a plurality of rectifier elements that perform rectification operation, a plurality of switch elements provided in parallel with the rectifier elements that perform on / off operation and a capacitor, wherein the power regeneration method comprises: defining a period obtained by adding a first set value to the period of each phase of the AC power source as a first set on period; determining whether to enter a power supply state or a power regeneration state; and in the power regeneration state, adjusting the length of the first set on period to control the on / off operation of the plurality of switch elements.

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