Power conversion device and metal working device

Abstract

The present application provides a power conversion device capable of shortening the time required for acceleration of a motor and a metal processing device including the power conversion device. The power conversion device (10) has a rectifier (100) that converts an alternating voltage from the outside into a direct current voltage (Vo) and a rectifier controller (107) that controls the rectifier (100). The rectifier (100) has a voltage doubling circuit (104) that steps up the direct current voltage (Vo) at the time of start-up and outputs direct current voltages (Vo) having different voltage values in response to start-up and stop of the voltage doubling circuit (104). The rectifier controller (107) starts up the voltage doubling circuit (104) at a first time point before a prescribed period from a second time point at which a speed command value (ω*) of the motor 130 rises from a prescribed value.

Description

Technical Field

[0001] The present invention relates to power conversion devices and metal processing apparatus, for example to power conversion devices including voltage doubler rectifier circuits and metal processing apparatus including such power conversion devices. Background Technology

[0002] The inverter device described in Patent Document 1 has a voltage multiplier circuit capable of switching between full-wave rectification mode and voltage multiplier rectification mode according to the load state of the motor. The DC voltage from the voltage multiplier circuit is the full-wave rectified voltage (1 times) in full-wave rectification mode and doubled (2 times) in voltage multiplier rectification mode. Consequently, in voltage multiplier rectification mode, compared to full-wave rectification mode, the output voltage of the inverter operating under the DC voltage from the voltage multiplier circuit is also doubled.

[0003] Furthermore, Patent Document 1 focuses on the operation of switching from full-wave rectification mode to voltage doubler rectification mode. When the control circuit receives an acceleration command from a load device such as a refrigerator, the voltage doubler circuit uses voltage doubler rectification mode to boost the DC voltage. The motor begins to accelerate when the DC voltage boost is complete, accelerating to the required speed. This allows for increased motor speed when rapid cooling is needed inside the refrigerator, thus improving cooling performance.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2002-64992 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Power conversion devices that convert DC power to three-phase AC power are widely used for speed control of electric motors. These devices typically use rectifier circuits to convert mains frequency power (such as three-phase 200V) to DC power, and then use inverters at the back end to output AC power with arbitrary voltage and frequency. The rectifier circuits in these devices mostly perform full-wave rectification of the three-phase AC voltage, and the DC voltage from the rectifier circuit is approximately √2 times the effective value of the input line-to-line voltages.

[0009] Generally, the upper limit of the output voltage of a power conversion device is determined by the DC voltage supplied to the inverter, and it cannot output voltages exceeding that. On the other hand, the induced voltage of a typical electric motor increases as its rotational speed increases. Therefore, in order to enable the motor to rotate at high speed, the inverter needs to output a higher voltage. For example, when the motor's load is a processing machine such as a press, it is necessary to reduce the cycle time to improve production efficiency. For this purpose, a mechanism that drives the motor with high-speed rotation and high acceleration is required.

[0010] Regarding the issue of high-speed rotation of such electric motors, a method using a voltage multiplier circuit to boost the DC voltage is known, as shown in Patent Document 1. However, in the method described in Patent Document 1, because the DC voltage boosting begins after receiving the motor acceleration command, the transition time caused by the boosting and acceleration is relatively long. As a result, if this method is applied to a servo motor of a machining machine that performs actions such as rapidly descending the machine to apply pressure to the workpiece and then rapidly ascending the machine, it may be difficult to achieve high-acceleration operations. In other words, the acceleration of the motor takes time, and there is a risk that it will be difficult to reduce the cycle time of the machining machine.

[0011] The present invention is based on the following circumstances, and one of its objectives is to provide a power conversion device capable of shortening the time required for electric motor acceleration and a metal processing apparatus including the power conversion device.

[0012] The above and other objects and novel features of the present invention will be explained by way of description and drawings in this specification.

[0013] Technical solutions for solving the problem

[0014] A brief summary of representative embodiments of the invention disclosed in this application is provided below.

[0015] A representative embodiment of the power conversion device of the present invention includes a rectifier that converts an external AC voltage into a DC voltage and a rectifier controller that controls the rectifier to supply power to a motor. The rectifier includes a voltage multiplier circuit that boosts the DC voltage during startup, and outputs DC voltages with different values ​​in response to the startup and shutdown of the voltage multiplier circuit. The rectifier controller activates the voltage multiplier circuit at a first moment before a predetermined period compared to a second moment when the motor speed command value rises from a predetermined value.

[0016] Invention Effects

[0017] The effects obtained by representative embodiments of the invention disclosed in this application will be briefly described, which can shorten the time required for electric motor acceleration. Attached Figure Description

[0018] Figure 1 This is a circuit diagram illustrating a structural example of the power conversion device surrounding an embodiment 1 of the present invention.

[0019] Figure 2 It means Figure 1 A schematic diagram of the main structure of the voltage multiplier controller.

[0020] Figure 3A This is a schematic diagram illustrating a structural example of a metal processing apparatus according to Embodiment 1 of the present invention.

[0021] Figure 3B It means Figure 3A The timing diagram of the operation of a metal processing device.

[0022] Figure 4 This is a circuit diagram illustrating a structural example of the power conversion device surrounding an embodiment 2 of the present invention.

[0023] Figure 5 It means Figure 4 A schematic diagram of the main structure of the voltage multiplier controller.

[0024] Figure 6 This is a circuit diagram showing a structural example of the main components surrounding the power conversion device according to Embodiment 3 of the present invention.

[0025] Figure 7 It means to Figure 6 Power conversion devices are used in Figure 3A A figure showing an example of the operation verification results of a metal processing device. Detailed Implementation

[0026] Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. In all the drawings used to illustrate the embodiments, the same reference numerals are generally used for the same components, and repeated descriptions are omitted.

[0027] (Implementation Method 1)

[0028] Structure of Power Conversion Devices

[0029] Figure 1 This is a circuit diagram illustrating a structural example of the power conversion device surrounding an embodiment 1 of the present invention. Figure 1 The power conversion device 10 shown is a device for supplying power to the motor 130. The motor 130 is, for example, a three-phase servo motor, controlling the position, speed, etc., of a motor load (e.g., a pressure mechanism, etc.) not shown. The power conversion device 10 includes a rectifier (converter) 100, an inverter 103, an AC voltage sensor 105, a DC voltage sensor 106, a voltage multiplier controller (rectifier controller) 107, and an inverter controller 108.

[0030] Additionally, a load controller 109 may be provided externally to the power conversion device 10. The load controller 109 controls the sequence of motor loads (e.g., pressure mechanisms). The load controller 109 determines various driving conditions of the motors 130 corresponding to each sequence. Consequently, the load controller 109 can determine the timing changes of the rotational speed, torque (current), etc., of the motors 130.

[0031] The rectifier 100 receives three-phase AC power from an external three-phase AC power supply 120 and converts the three-phase AC voltage (Vu, Vv, Vw) into a DC voltage Vo. Specifically, the rectifier 100 includes a three-phase diode bridge 101, a DC link section 102, and a voltage multiplier circuit 104. The three-phase diode bridge 101 performs full-wave rectification on the three-phase AC power from the three-phase AC power supply 120 and converts it into a DC voltage Vo using the DC link section 102. The DC link section 102 has two DC link capacitors C1 and C2 connected in series between the positive output node Np1 and the negative output node Nn1 of the three-phase diode bridge 101.

[0032] In this example, the voltage multiplier circuit 104 receives three-phase AC power from the three-phase AC power supply 120. Upon startup, it boosts the DC voltage Vo to a specified voltage via the common connection node of DC link capacitors C1 and C2. Specifically, the voltage multiplier circuit 104 boosts the DC voltage Vo to approximately twice its rated voltage by alternately charging the DC link capacitors C1 and C2. Consequently, the rectifier 100 outputs a different DC voltage Vo depending on whether the voltage multiplier circuit 104 is running or stopped (i.e., in voltage multiplier rectification mode or full-wave rectification mode). The DC voltage Vo is the full-wave rectified voltage in full-wave rectification mode and the doubled voltage in voltage multiplier rectification mode.

[0033] AC voltage sensor 105 detects the voltage values ​​(Vu', Vv', Vw') of each phase of the three-phase AC power supply 120. DC voltage sensor 106 detects the DC voltage value (Vo'). The detection results of AC voltage sensor 105 and DC voltage sensor 106 are input to voltage multiplier controller (rectifier controller) 107 via signal lines 110 and 112, respectively. Based on these detection results, voltage multiplier controller 107 controls the switching elements (not shown) within voltage multiplier circuit 104 via signal line 111 using the switching signal Gsw.

[0034] Furthermore, the voltage multiplier controller 107 receives load information (motor information) LDI from the load controller 109 via signal line 113. The load information LDI includes, for example, load power information and load control information, as detailed later. Based on this load information LDI, the voltage multiplier controller 107 determines the start-up time of the voltage multiplier circuit 104. Then, the voltage multiplier controller 107 begins switching control of the voltage multiplier circuit 104 from this start-up time.

[0035] In this example, inverter 103 is a three-phase inverter comprising six switching elements SW. Inverter 103 converts the DC voltage Vo from rectifier 100 into AC voltage (three-phase AC voltage) and outputs it to motor 130. The switching elements SW are, for example, IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), or thyristors. Additionally, inverter 103 includes current sensors (not shown) that detect the current values ​​(Iu', Iv', Iw') of each phase. The detection results of these current sensors are input to inverter controller 108 via signal line 115.

[0036] Furthermore, the inverter controller 108 receives speed command values ​​ω* and torque command values ​​(current command values) I* from the load controller 109 via signal line 114. The inverter controller 108 performs PI control (proportional-integral control) to make the rotational speed of the motor 130 close to the speed command value ω*. Alternatively, the inverter controller 108 performs PI control to make the current value of the motor 130 (the detected current values ​​(Iu', Iv', Iw')) close to the current command value I*.

[0037] Then, the inverter controller 108 determines the duty cycle of the PWM signal through PI control and other means, and generates PWM signals PWMu, PWMv, and PWMw for each phase in accordance with the specified power-on mode (e.g., 180° power-on mode). The inverter controller 108 controls the switching of each switching element SW in the inverter 103 according to the PWM signals PWMu, PWMv, and PWMw.

[0038] Figure 1 In this configuration, the voltage multiplier controller 107 and the inverter controller 108 are typically composed of one or more microcontrollers. The signal lines 110-116 are not limited to wired connections and can also be wireless. They are then mounted together with the components constituting the rectifier 100 and inverter 103 on one or more wiring circuit boards, housed within the casing constituting the power conversion device 10. Additionally, the load controller 109 is typically mounted in an external upper-level device outside the power conversion device 10.

[0039] Furthermore, the installation method is not limited to this one and can be modified appropriately. For example, part or all of the voltage multiplier controller 107 and inverter controller 108 can be constructed using FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit). That is, each controller can be constructed appropriately using software or hardware or a combination thereof.

[0040] Furthermore, both the rectifier 100 and the inverter 103 here use a three-phase (u-phase, v-phase, w-phase) structure, but any structure with two or more phases is acceptable. Moreover, here, the motor 130 is driven by the three-phase AC power obtained using the inverter 103, but depending on the situation, the motor 130 can also be driven by a DC voltage Vo.

[0041] Figure 2 It means Figure 1 A schematic diagram of the main structure of the voltage multiplier controller. Figure 2 The voltage multiplier controller 107 includes a start-up timing arithmetic unit 203 and a switch signal arithmetic unit 205. Load information (motor information) LDI, namely load power information 201 and load control information 202, is input to the start-up timing arithmetic unit 203. The load control information 202 includes timing information for when the speed command value ω* of the motor 130 rises from a predetermined value. In other words, it includes timing information required for the voltage multiplier circuit 104 to start. The load power information 201 indicates the power consumption of the motor 130.

[0042] Based on the load information LDI, the start-up timing calculator 203 determines the start-up timing as the time before the moment when the speed command value of the motor 130 rises from a specified value, compared to a specified period earlier. At this start-up timing, the start-up timing calculator 203 activates the voltage doubler start signal EN. Corresponding to the activation of the voltage doubler start signal EN, the switch signal calculator 205 starts generating a switch signal Gsw, which is used to control the switching elements (not shown) within the voltage doubler circuit 104.

[0043] Furthermore, the startup timing arithmetic unit 203 is implemented, for example, using program processing performed by the CPU (Central Processing Unit) within the microcontroller. The switch signal arithmetic unit 205 is implemented, for example, using a counter within the microcontroller.

[0044] Examples of applications in metal processing equipment

[0045] Figure 3A This is a schematic diagram illustrating a structural example of a metal processing apparatus according to Embodiment 1 of the present invention. Figure 3A The metalworking apparatus 310 is a pressure device that uses a slider (pressure mechanism) 311 to process metal, which is the workpiece 315. The metalworking apparatus 310 includes a slider 311, a worktable 312, an electric motor (servo motor) 130, and a power conversion device 10. A lower die 314 is mounted on the worktable 312, and the workpiece 315 is positioned across the lower die 314. The slider 311 is arranged opposite the worktable 312, with the workpiece 315 in between. An upper die 313 is mounted on the slider 311.

[0046] The electric motor 130 controls the position of the slider (pressure mechanism) 311 between the processing position P0 and the standby position P1. The processing position P0 is the position when processing the workpiece (metal) 315. The power conversion device 10 includes, as follows: Figure 1 The rectifier 100 and inverter 103 shown control the rotation of the motor 130 (and the position of the slider 311) by supplying a specified power to the motor 130. When the position of the slider 311 is controlled to the processing position P0 via the motor 130, the workpiece (metal) 315 is processed into a specified shape based on the shapes of the upper mold 313 and the lower mold 314. During this processing, the torque control (current control) of the motor 130 is appropriately performed.

[0047] Figure 3B It means Figure 3A The timing diagram of the operation of a metal processing device. Figure 3B The diagram shows the control states for the mechanical position (position of slider 311), motor rotation speed (and speed command value ω*), motor torque (and current command value I*), voltage multiplier start signal EN, and DC voltage Vo. The motor torque (I*) is expressed positively with respect to the direction of pressure applied to the workpiece 315. The components other than the DC voltage Vo will be explained first.

[0048] During the period T1 up to time t2, the metal processing apparatus 310 operates in a processing mode where the workpiece (metal) 315 is pressurized by the slider 311. During period T1, the mechanical position is the processing position P0. The motor rotational speed (ω*) is low, close to zero, because the workpiece 315 is being pressurized. On the other hand, the motor torque (I*) is high, because the workpiece 315 is being pressurized.

[0049] During the period T2 from time t2 to time t5, the metal processing apparatus 310 operates in a transfer mode that moves the slider 311 from the processing position P0 to the standby position P1. When the processing of the workpiece 315 is completed, it is required that the slider 311 quickly return to the standby position P1. Therefore, the control causes the motor rotation speed (speed command value ω*) to increase from the time t2 when the processing of the workpiece 315 ends. Correspondingly, the motor 130 begins to accelerate towards the upper limit target speed determined by the speed command value ω* from time t2, reaching the upper limit target speed at time t3. During the period from time t3 to time t4, the motor 130 maintains its rotation at this upper limit target speed.

[0050] At time t4, in order for slider 311 to reach the standby position P1 in a sufficiently decelerated state (with a speed approximately zero), the control reduces the motor's rotational speed (ω*). Then, slider 311 reaches the standby position P1 at time t5 in a sufficiently decelerated state. The motor torque (I*) is a small negative value during the period from time t2 to time t4 because only the torque required to move slider 311 is needed. Furthermore, the motor torque (I*) becomes positive during the period from time t4 to time t5 as the motor's rotational speed (ω*) decelerates.

[0051] During the period T3 following time t5, the metal processing apparatus 310 operates in a standby mode awaiting the next processing operation. During period T3, the mechanical position remains in standby position P1, and both the motor rotational speed (ω*) and motor torque (I*) are zero. Additionally, although not illustrated, a transfer mode is set after standby mode T3 to perform transfer in the opposite direction to period T2.

[0052] Next, the DC voltage Vo will be explained. For Figure 3B The DC voltage Vo, indicating the use of Figure 1 The control state 301 is shown in the case of the power conversion device 10, and the control state 302 is shown in the case of the power conversion device of the comparative example. During the processing mode period T1, the voltage doubler start signal EN is at a negative level until time t1. Correspondingly, the voltage doubler circuit 104 is in a stopped state.

[0053] On the other hand, the voltage multiplier controller 107 activates the voltage multiplier start signal EN at time t1. Correspondingly, the voltage multiplier circuit 104 starts. That is, the voltage multiplier controller 107 begins outputting a switching signal Gsw to the voltage multiplier circuit 104. Then, at time t2, it switches from processing mode to transfer mode. The voltage multiplier controller 107 maintains the activation level of the voltage multiplier start signal EN in the transfer mode (during period T2) and the subsequent standby mode (during period T3). Correspondingly, the voltage multiplier circuit 104 continues its boost operation after time t2.

[0054] During the period T1 up to time t1, the DC voltage Vo is the full-wave rectified voltage value V1 because the voltage multiplier circuit 104 is in a stopped state. Then, during the period T12 from time t1 to time t2, the voltage multiplier circuit 104, in response to the activation of the voltage multiplier start signal EN, boosts the DC voltage Vo from the full-wave rectified voltage value V1 to a higher pre-set voltage value V2. Furthermore, after time t2, the voltage multiplier circuit 104 boosts the DC voltage Vo from the pre-set voltage value V2 to a higher voltage value V3, approximately twice the voltage value V1.

[0055] Here, the voltage multiplier circuit 104, under the requirement of miniaturization of the power conversion device 10, such as... Figure 3B As shown, the design is based on the premise of supplying power in a transfer mode with relatively low motor torque (I*). Therefore, the voltage multiplier circuit 104 is composed of components that are smaller in size and have a smaller power capacity compared to the inverter 103. As a result, during the period T12 included in the processing mode period T1, when the voltage multiplier circuit 104 is started, the DC voltage Vo cannot reach the multiplied voltage value V3, but instead reaches a stable value at the voltage value V2 between the voltage values ​​V1 and V3.

[0056] This stable value (voltage value V2) is determined based on the known power capacity of the voltage multiplier circuit 104 and the power consumption of the motor 130 during the operation mode. Specifically, voltage value V2 is the voltage value at which the charging current from the voltage multiplier circuit 104 to the DC link section 102 is balanced with the discharge current from the DC link section 102 caused by the power consumption of the motor 130. Therefore, Figure 2 The start-up timing arithmetic unit 203 can calculate the voltage value V2 by inputting load power information 201, which represents the power consumption of the motor 130 during the processing mode.

[0057] Furthermore, the startup timing calculator 203, based on the known capacitance values ​​(i.e., boost time constants) of each capacitor (C1, C2) constituting the DC link section 102 and the effective charging current of the DC link section 102, can calculate the time required to boost the DC voltage Vo from voltage value V1 to voltage value V2. The startup timing calculator 203 determines this calculated time as... Figure 3B The period T12. Additionally, the startup timing calculator 203 can obtain the load control information 202. Figure 3B The time t2 is the moment when the slider (pressure mechanism) 311 begins to move from the processing position P0 to the standby position P1.

[0058] Based on this information, the start-up timing calculator 203 activates the voltage doubler start signal EN at time t1, which is before the time t2, compared to the time T12, when the speed command value ω* of the motor 130 rises from the predetermined value. Here, if time t1 is too early, the operating period of the voltage doubler circuit 104 becomes longer, potentially resulting in unnecessary power loss. On the other hand, if time t1 is too late, the transition to the transfer mode occurs before the DC voltage Vo reaches the voltage value V2. In this case, the acceleration period of the motor 130 during the period T23 from time t2 to time t3 becomes longer, and the transfer mode period T2 becomes longer.

[0059] Therefore, as Figure 3B As shown, it is advantageous to determine time t1 so that the moment when the DC voltage Vo reaches voltage value V2 is approximately the same as the moment t2 when switching from processing mode to transfer mode. Then, when switching from processing mode to transfer mode at time t2, the DC voltage Vo begins to rise again because the motor torque (I*) decreases. Then, during period T23, the DC voltage Vo rises from voltage value V2 to a voltage value V3 that is approximately twice the full-wave rectified voltage value V1. At this time, the rotational speed of motor 130 can be increased accordingly to increase the DC voltage Vo. After time t3, the DC voltage Vo becomes stable.

[0060] In addition, Figure 3B During period T12, the power supply voltage of inverter 103 changes due to the DC voltage Vo boosting during the processing mode. In this case, the stability of the control loop in inverter controller 108 (e.g., changes in current value compared to the current command value I*) is a concern. However, especially in servo mechanisms such as metal processing equipment, inverter controller 108, which acts as a servo amplifier, is typically designed with a sufficiently fast control loop response. Therefore, the stability of the control loop can be adequately maintained (keeping the current value at the current command value I*).

[0061] Furthermore, in the power conversion device used as a comparative example, the voltage multiplier circuit 104 is activated at least after the processing mode is completed, such as... Figure 3B As shown in control state 302, the earliest start time is also at time t2 when switching from processing mode to transfer mode. In this case, starting from time t2, it takes time for the DC voltage Vo to rise from voltage value V1 to voltage value V3, and the acceleration period of motor 130 (and the period of transfer mode T2) also becomes longer accordingly with this rise time.

[0062] Main effects of Implementation Method 1

[0063] By using Embodiment 1, the acceleration time required for the electric motor 130 can be typically shortened (i.e., Figure 3BDuring the period T23). As a result, the cycle time of the metal processing device 310 can be shortened. Furthermore, this effect can be achieved without increasing the power capacity of the voltage multiplier circuit 104. By not increasing the power capacity of the voltage multiplier circuit 104, the power conversion device 10 can be miniaturized.

[0064] in addition, Figure 2 In the example, the start-up timing calculator 203 is used to determine the start-up timing (timing t1) of the voltage multiplier circuit 104. However, typically, if the types of workpieces 315 being processed are the same, then timing t1 remains constant. Therefore, timing t1 can also be predetermined in advance using simulation or similar methods for each type of workpiece 315. In this case, for example... Figure 1 The load controller 109 can activate the voltage doubler start signal EN for the voltage doubler controller 107 at time t1 determined by the simulation.

[0065] in addition, Figure 3B In the example, the prepared voltage value V2 is set to a value passively determined by the various conditions described above. However, it is also possible to actively determine the prepared voltage value V2 through the control loop. For example, if the passively determined prepared voltage value V2 is close to the voltage value V3 of the voltage multiplier, the losses of the inverter 103 in T12 are relatively large, and there is a possibility that the stability of the control loop of the inverter controller 108 becomes non-negligible. In such a case, control can be implemented to limit the upper limit of the prepared voltage value V2.

[0066] (Implementation Method 2)

[0067] Structure and Operation of Power Conversion Devices

[0068] Figure 4 This is a circuit diagram illustrating a structural example of the power conversion device surrounding an embodiment 2 of the present invention. Figure 4 The power conversion device 20 shown is Figure 1 Compared to the previous example, the voltage multiplier controller (inverter controller) 107 has a different structure and operation. Regarding the voltage multiplier controller 107, compared to... Figure 1 Unlike other cases, the current command value I* used in the inverter controller 108 is input via signal line 401. Based on the change in this current command value I*, the voltage multiplier controller 107 determines the start-up time of the voltage multiplier circuit 104 (i.e.,...). Figure 3B (Time t1).

[0069] Here, as Figure 4The inverter controller 108 of the voltage multiplier controller 107 can be implemented in various ways, including in the case of implementation in the same microcontroller or the like, and in the case of implementation in different microcontrollers or the like, but mounted on the same wiring board. On the other hand, the load controller 109, as described above, is mostly located in an upper-level device outside the housing constituting the power conversion device 20. Therefore, it is possible to... Figure 4 Signal line 401 and Figure 1 The signal line 113 is shortened compared to the previous version. As a result, communication noise can be reduced and installation can be simplified.

[0070] Figure 5 It means Figure 4 A schematic diagram of the main structure of the voltage multiplier controller. Figure 5 Voltage multiplier controller 107 and Figure 2 Similarly, it includes a start-time arithmetic unit 203 and a switch signal arithmetic unit 205. However, for the start-time arithmetic unit 203, and... Figure 2 In different cases, the input current command value is I*.

[0071] Here, in such Figure 3A In the metal processing apparatus 310 shown, during processing mode, the required processing is generally performed by successively varying the torque (i.e., the current command value I*). Therefore, the start-up timing calculator 203 can calculate which moment within the processing mode period T1 the current time is by comparing the variation pattern of the current command value I* obtained from the inverter controller 108 with the pre-held variation pattern. Accordingly, the start-up timing calculator 203 can estimate... Figure 3B The time t2. Additionally, the start-up timing arithmetic unit 203 can also calculate based on the acquired current command value I*. Figure 3B The period T12. Therefore, the start-time calculator 203 can calculate... Figure 3B The moment t1.

[0072] Main effects of implementation method 2

[0073] By using the above-described Embodiment 2, the same effect as in Embodiment 1 can be achieved. Furthermore, the power conversion device 20 does not need to receive special information from the load controller 109 (e.g., an upstream device) (e.g., ...). Figure 2 The load control information 202 can determine when to start the voltage multiplier circuit 104.

[0074] (Implementation Method 3)

[0075] Structure and Operation of Power Conversion Devices

[0076] Figure 6This is a circuit diagram showing a structural example of the main components surrounding the power conversion device according to Embodiment 3 of the present invention. Figure 6 In, with Figure 1 Alternatively, Figure 3 shows a detailed circuit structure example of the voltage multiplier circuit 104 within the power conversion device 60. The voltage multiplier circuit 104 includes a three-phase diode bridge 601, a half-bridge 602, and an inductor L1. The half-bridge 602 has two switching elements SW1 and SW2. When the voltage multiplier circuit 104 is activated, the three-phase diode bridge 601 performs full-wave rectification of the three-phase AC voltages (Vu, Vv, Vw) from the three-phase AC power supply 120.

[0077] Inductor L1 is connected between the common connection node Nc of the two DC link capacitors C1 and C2 and the switching node Nsw. Switching element SW1 is connected between the positive output node Np2 of the three-phase diode bridge 601 and the switching node Nsw. Switching element SW2 is connected between the negative output node Nn2 of the three-phase diode bridge 601 and the switching node Nsw. Switching elements SW1 and SW2 are, for example, composed of IGBTs, MOSFETs, or thyristors.

[0078] Figure 1 The voltage multiplier controller (rectifier controller) 107 shown controls the switching elements SW1 and SW2 with multiple switching signals Gsw when the voltage multiplier circuit 104 is started. On the other hand, when the voltage multiplier circuit 104 is in a stopped state, the voltage multiplier controller 107 keeps the switching elements SW1 and SW2 fixed to the open state.

[0079] The operation of the voltage multiplier circuit 104 will be explained. First, consider the case where switching element SW1 is controlled to be on and switching element SW2 is controlled to be off. In this case, charging current flows through the path of the three-phase AC power supply 120, the positive output node Np2 of the three-phase diode bridge 601, switching element SW1, inductor L1, DC link capacitor C2, the negative output node Nn1 of the three-phase diode bridge 101, and the three-phase AC power supply 120. As a result, only the DC link capacitor C2 is charged.

[0080] Next, consider the scenario where switching element SW2 is controlled to be on and switching element SW1 is controlled to be off. In this case, charging current flows through the three-phase AC power supply 120, the positive output node Np1 of the three-phase diode bridge 101, the DC link capacitor C1, the inductor L1, the switching element SW2, the negative output node Nn2 of the three-phase diode bridge 601, and the path of the three-phase AC power supply 120. As a result, only the DC link capacitor C1 is charged.

[0081] Therefore, by alternately switching the on / off states of switching elements SW1 and SW2, the DC link capacitors C1 and C2 can be charged alternately. At this time, the DC link capacitors C1 and C2 are charged to the full-wave rectified voltage. As a result, the DC voltage Vo becomes approximately twice the full-wave rectified voltage. Furthermore, the inductor L1 is provided to suppress any inrush current to the capacitors (C1, C2) that may occur after the voltage multiplier circuit 104 is activated until the DC voltage Vo has been boosted.

[0082] Furthermore, the two three-phase diode bridges 101 and 601 appear to be connected in parallel from the perspective of the three-phase AC power supply 120. Therefore, for example in Figure 3B During period T12, the large amount of power required by inverter 103 is mostly supplied by the three-phase diode bridge 101, making it almost unnecessary to supply it with voltage multiplier circuit 104. That is, voltage multiplier circuit 104 can boost DC voltage Vo while outputting less power than inverter 103. As a result, a lower-cost and smaller voltage multiplier circuit 104 with a smaller power capacity than inverter 103 can be used. Specifically, for example, the switching elements SW1 and SW2 within voltage multiplier circuit 104 are configured to have a smaller element size than the switching elements SW within inverter 103.

[0083] Figure 7 It means to Figure 6 Power conversion devices are used in Figure 3A A figure showing an example of the operation verification results of a metal processing device. Figure 7 In the middle, it is shown that... Figure 3B The results are obtained by simulating the inductor current IL and DC voltage Vo flowing in inductor L1, taking the period from around time t1 to around time t3 as the object. Figure 7 During the period up to time t1, the voltage multiplier circuit 104 is in a stopped state, so the inductor current IL is zero, and the DC voltage Vo is the full-wave rectified voltage (voltage value V1). After the voltage multiplier circuit 104 starts at time t1, the inductor current IL changes at a high frequency due to the soft-start control immediately after startup.

[0084] Specifically, firstly, corresponding to the control of the switching elements SW1 and SW2 as described above, the inductor current IL alternately switches between positive and negative currents according to predetermined periods. These predetermined periods are, for example, determined based on the switching of the maximum or minimum voltage phase in the three-phase AC voltages (Vu, Vv, Vw), and are periods corresponding to an electrical angle of 60° of that AC phase. The timing of the switching of the maximum or minimum voltage phase is determined using... Figure 1 The AC voltage sensor 105 is used for detection.

[0085] Then, Figure 1The voltage multiplier controller 107 intermittently controls the switching element (SW1 or SW2) on the turn-on side to be switched on during a period equivalent to an electrical angle of 60°, ensuring that the inductor current IL does not exceed a predetermined limit range (ILmin to ILmax). In other words, the switching element on the turn-on side is switched at a higher switching frequency. This type of control is called soft-start control. That is, during the boosting period, a large inrush current (i.e., overcurrent) may flow through the DC link capacitors C1 and C2, so the voltage multiplier controller 107 uses soft-start control to prevent this overcurrent.

[0086] The DC voltage Vo begins to rise from time t1 and reaches a stable state at the predetermined voltage value V2. At time t2, a switch occurs from processing mode to transfer mode, requiring a decrease in motor current, so the DC voltage Vo begins to rise again. Meanwhile, the inductor current IL remains almost unchanged around time t2. At time t3, the DC voltage Vo reaches double its value (V3).

[0087] Here, near time t3, the voltage of the three-phase AC power supply 120 counteracts the voltage of the DC link capacitors C1 and C2, causing the inductor current IL to decrease to a level below the limiting range (ILmin to ILmax). As a result, intermittent control of the switching elements SW1 and SW2 ceases. Then, the switching elements SW1 and SW2 stabilize while maintaining switching control at intervals of 60° per electrical angle. In other words, a steady state is achieved at a switching frequency three times the frequency of the three-phase AC power supply 120.

[0088] Main effects of implementation method 3

[0089] By using the above-described embodiment 3, similar to embodiments 1 and 2, the acceleration time required for the motor 130 can be shortened without increasing the power capacity of the voltage multiplier circuit 104. Furthermore, by using... Figure 6 The voltage multiplier circuit 104 shown in parallel connection can reduce power loss. That is, as a voltage multiplier circuit configuration, for example, it is known to insert components in series along the path between the three-phase diode bridge 101 and the DC link section 102. In this case, due to these series-inserted components, excess power loss can occur during full-wave rectification mode. Figure 6 Such power loss will not occur when the circuit is configured in this way.

[0090] The invention derived by the inventors has been specifically described above based on the embodiments, but the invention is not limited to the above embodiments and various modifications can be made without departing from its spirit. For example, the above embodiments are described in detail for ease of understanding of the invention and are not limited to having all the structures described. In addition, a part of the structure of a certain embodiment can be replaced with the structure of another embodiment, and the structure of another embodiment can be added to the structure of a certain embodiment. Furthermore, for a part of the structure of each embodiment, other structures can be added, deleted, or replaced.

[0091] For example, an application example of a power conversion device to a metal processing device is shown here, but it is certainly not limited to this. The same application can be made to various devices (systems) that operate by appropriately switching between full-wave rectification mode and voltage doubler rectification mode in accordance with the switching of the rotational speed of the motor.

[0092] Explanation of reference numerals in the attached figures

[0093] 10, 20, 60… Power conversion device, 100… Rectifier, 101, 601… Three-phase diode bridge, 102… DC link section, 103… Inverter, 104… Voltage multiplier circuit, 107… Voltage multiplier controller (rectifier controller), 108… Inverter controller, 109… Load controller, 130… Motor, 310… Metal processing device, 311… Slider (pressure mechanism), 315… Workpiece (metal), C1, C2… DC link capacitor, EN… Voltage multiplier start signal, L1… Inductor, SW, SW1, SW2… Switching element, Vo… DC voltage.

Claims

1. A power conversion device for supplying power to an electric motor, characterized in that, include: A rectifier that converts AC voltage from an external source into DC voltage; and The rectifier controller controls the rectifier. The rectifier has a voltage multiplier circuit that boosts the DC voltage during startup, and outputs different DC voltage values ​​in response to the startup and shutdown of the voltage multiplier circuit. The rectifier controller activates the voltage multiplier circuit at a first moment before a predetermined period compared to the second moment when the speed command value of the motor rises from a predetermined value. The power conversion device further includes: An inverter, comprising multiple switching elements, converts the DC voltage from the rectifier into an AC voltage for output to the motor; and An inverter controller that controls the switching of the plurality of switching elements within the inverter in a manner that brings the rotational speed of the motor close to a speed command value. The rectifier includes: First three-phase diode bridge; A first DC link capacitor and a second DC link capacitor are connected in series between the positive and negative output nodes of the first three-phase diode bridge; and The voltage multiplier circuit comprises a second three-phase diode bridge, a first switching element, a second switching element, and an inductor. The inductor is connected between the common connection node of the first DC link capacitor and the second DC link capacitor and the switching node. The first switching element is connected between the positive output node of the second three-phase diode bridge and the switching node. The second switching element is connected between the negative output node of the second three-phase diode bridge and the switching node. The rectifier controller controls the switching of the first and second switching elements as the voltage multiplier circuit is activated.

2. The power conversion device as described in claim 1, characterized in that: The rectifier boosts the DC voltage from a first voltage value to a second voltage value higher than the first voltage value during the specified period, and after the second time point, boosts the DC voltage from the second voltage value to a third voltage value higher than the second voltage value.

3. The power conversion device as described in claim 2, characterized in that: The second voltage value is a stable value determined based on the power capacity of the voltage multiplier circuit and the power consumption of the motor. The specified period is determined based on the time it takes for the DC voltage to reach the stable value from the first voltage value.

4. The power conversion device as described in claim 1, characterized in that: The element size of the first switching element and the second switching element is smaller than the element size of each of the plurality of switching elements in the inverter.

5. A metal processing apparatus that uses a pressure mechanism to process metal as the workpiece, characterized in that, include: An electric motor controls the position of the pressure mechanism between a processing position during metal processing and a predetermined standby position; and A power conversion device for supplying power to the motor. The power conversion device includes: A rectifier that converts AC voltage from an external source into DC voltage; and The rectifier controller controls the rectifier. The rectifier has a voltage multiplier circuit that boosts the DC voltage during startup, and outputs different DC voltage values ​​in response to the startup and shutdown of the voltage multiplier circuit. The rectifier controller activates the voltage multiplier circuit at a first moment before a predetermined period compared to the second moment when the speed command value of the motor rises from a predetermined value. The second moment is the moment when the pressure mechanism begins to move from the processing position to the standby position. The power conversion device further includes: An inverter, comprising multiple switching elements, converts the DC voltage from the rectifier into an AC voltage for output to the motor; and An inverter controller controls the switching of the plurality of switching elements within the inverter in a manner that brings the rotational speed of the motor close to a speed command value or the current value of the motor close to a current command value. The rectifier includes: First three-phase diode bridge; A first DC link capacitor and a second DC link capacitor are connected in series between the positive and negative output nodes of the first three-phase diode bridge; and The voltage multiplier circuit comprises a second three-phase diode bridge, a first switching element, a second switching element, and an inductor. The inductor is connected between the common connection node of the first DC link capacitor and the second DC link capacitor and the switching node. The first switching element is connected between the positive output node of the second three-phase diode bridge and the switching node. The second switching element is connected between the negative output node of the second three-phase diode bridge and the switching node. The rectifier controller controls the switching of the first and second switching elements as the voltage multiplier circuit is activated.

6. The metal processing apparatus as described in claim 5, characterized in that: The rectifier boosts the DC voltage from a first voltage value to a second voltage value higher than the first voltage value during the specified period, and after the second time point, boosts the DC voltage from the second voltage value to a third voltage value higher than the second voltage value.

7. The metal processing apparatus as described in claim 6, characterized in that: The second voltage value is a stable value determined based on the power capacity of the voltage multiplier circuit and the power consumption of the motor due to the metal processing. The specified period is determined based on the time it takes for the DC voltage to reach the stable value from the first voltage value.

8. The metal processing apparatus as described in claim 5, characterized in that: The element size of the first switching element and the second switching element is smaller than the element size of each of the plurality of switching elements in the inverter.

9. The metal processing apparatus as described in claim 5, characterized in that: The rectifier controller takes the current command value used in the inverter controller as input and determines the first moment based on the change of the current command value.

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