Power conversion device

Abstract

The present application provides an elevator power conversion device capable of suppressing the loss of an inverter even when the running state of a car approaches a stop. In the power conversion device (11), an inverter (15) generates AC power from DC power converted by a commutator (12) from AC power and smoothed by a smoothing capacitor (14), and supplies the AC power to a drive device (3) that runs a car (5) of an elevator (1). A control section (16) sets a control mode of the commutator (12) to a first mode when the car (5) is run at a running speed equal to or higher than a reference value. The control section (16) sets the control mode of the commutator (12) to a second mode when the car (5) is run at a running speed lower than the reference value. The first mode is a control mode in which the commutator (12) is caused to operate at a first power factor set in advance. The second mode is a control mode in which the commutator (12) is caused to operate at a second power factor lower than the first power factor.

Description

Technical Field

[0001] This disclosure relates to power conversion devices. Background Technology

[0002] Patent Document 1 discloses an example of an elevator control device. The control device includes an inverter and a controller. The inverter converts alternating current (AC) into direct current (DC). The controller controls the operation of the inverter. During the elevator's powered operation, the controller makes it more difficult for the reactive current of the inverter to flow compared to regenerative operation; conversely, during the elevator's regenerative operation, it makes it easier for the reactive current of the inverter to flow compared to powered operation.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2017 / 163312 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the elevator described in Patent Document 1, the motor used in the drive unit that moves the car operates on alternating current (AC) power, which is generated by an inverter based on the direct current (DC) power output from a converter. The inverter provides the motor's torque current. Here, when the elevator car's speed is close to 0 and the travel state is close to a stop, such as immediately after starting or when it is about to stop, the motor current phase hardly changes. Therefore, when the car's travel state is close to a stop, the inverter's losses are high, and in the case of three phases, the losses may be concentrated in the components of a specific phase.

[0008] This disclosure addresses such a problem. It provides an elevator power conversion device that can suppress inverter losses even when the car is nearing a stop.

[0009] means for solving problems

[0010] The power conversion device disclosed herein includes:

[0011] The system comprises: a converter that converts input AC power into DC power; an AC reactor connected to the input side of the converter; a smoothing capacitor connected to the output side of the converter; an inverter that generates AC power from the DC power converted from AC power by the converter and smoothed by the smoothing capacitor, and supplies it to a drive unit that moves the elevator car; and a control unit that controls the movement of the car through the control of the inverter and the converter. When the car's speed is above a preset reference value, the control unit sets the converter's control mode to a first mode that operates with a preset first power factor; when the car's speed is below the reference value, the control mode sets the converter's control mode to a second mode that operates with a second power factor lower than the first power factor.

[0012] The effects of the invention

[0013] According to the power conversion device disclosed herein, inverter losses can be suppressed even when the elevator car is nearly stopped. Attached Figure Description

[0014] Figure 1 This is a structural diagram of the elevator in Implementation Method 1.

[0015] Figure 2 This is a diagram showing the single-phase equivalent circuit of the converter in Embodiment 1.

[0016] Figure 3A This is a diagram showing the operating region of the converter in Embodiment 1 and the upper limit of the inductance of the corresponding AC reactor.

[0017] Figure 3B This is a diagram showing the operating region of the converter in Embodiment 1 and the corresponding input current values.

[0018] Figure 4 This is a diagram showing the operating region of the converter in Embodiment 1 and the corresponding DC bus voltage.

[0019] Figure 5A This is a conceptual diagram of the operation of the converter in the first mode of implementation method 1.

[0020] Figure 5B This is a conceptual diagram of the operation of the converter in the first mode of implementation method 1.

[0021] Figure 6A This is a conceptual diagram of the operation in the second mode of the converter according to implementation method 1.

[0022] Figure 6B This is a conceptual diagram of the operation in the second mode of the converter according to implementation method 1.

[0023] Figure 7A This is a diagram illustrating an example of the motion waveform in an elevator according to Embodiment 1.

[0024] Figure 7B This is a diagram illustrating an example of the motion waveform in an elevator according to Embodiment 1.

[0025] Figure 8A This is a diagram showing an example of the switching waveform of the inverter in the elevator according to Embodiment 1.

[0026] Figure 8B This is a diagram showing an example of the switching waveform of the inverter in the elevator according to Embodiment 1. Detailed Implementation

[0027] The embodiments of the present disclosure will be described with reference to the accompanying drawings. In the drawings, identical or equivalent parts are labeled with the same reference numerals, and repeated descriptions are simplified or omitted as appropriate. Furthermore, the present disclosure is not limited to the following embodiments; any modifications to the structural elements of the embodiments or omissions of any structural elements of the embodiments are possible without departing from the spirit of the present disclosure.

[0028] Implementation method 1.

[0029] Figure 1 This is a structural diagram of elevator 1 according to implementation method 1.

[0030] Elevator 1 is used in buildings with multiple floors. A shaft 2 for elevator 1 is provided within the building. The shaft 2 is a relatively long space extending vertically through multiple floors. Elevator 1 includes a drive unit 3, a main rope 4, a car 5, a counterweight 6, and a control unit 7.

[0031] The drive unit 3 is disposed, for example, at the upper or lower part of the hoistway 2. For example, if a machine room for the elevator 1 is located above the hoistway 2, the drive unit 3 may also be disposed in the machine room. The drive unit 3 is, for example, a traction machine. The drive unit 3 includes a motor 8 and a drive sheave 9. The motor 8 receives an electrical supply and generates torque. The drive sheave 9 is a device that rotates due to the torque generated by the motor 8.

[0032] The main rope 4 is wound around the drive sheave 9. The main rope 4 supports the load of the car 5 on one side of the drive sheave 9. The main rope 4 supports the load of the counterweight 6 on the other side of the drive sheave 9. The main rope 4 moves by the rotation of the drive sheave 9, causing either side of the drive sheave 9 to be wound up.

[0033] The car 5 is a device that transports users of the elevator 1 between multiple floors by traveling vertically in the hoistway 2. The car 5 travels vertically in the hoistway 2 in conjunction with the movement of the main rope 4 caused by the rotation of the drive sheave 9.

[0034] The counterweight 6 is a device that balances the load applied to both sides of the drive sheave 9 between the counterweight 6 and the car 5. The counterweight 6 moves in the hoistway 2 in the vertical direction opposite to the car 5, linked to the movement of the main rope 4 caused by the rotation of the drive sheave 9.

[0035] The control device 7 is a device for controlling the operation of the elevator 1. The control of the elevator 1's operation includes controlling the movement of the car 5. The elevator 1 receives power from an external system power supply 10 to operate. In this example, the system power supply 10 is a commercial power supply providing three-phase alternating current. The control device 7 includes a power conversion device 11. The power conversion device 11 converts the power received from the system power supply 10 and supplies it to the motor 8 of the drive unit 3. The power conversion device 11 includes an inverter 12, an AC reactor 13, a smoothing capacitor 14, an inverter 15, and a control unit 16.

[0036] Converter 12 converts the three-phase AC power input from system power supply 10 into DC power. In this example, converter 12 is a three-phase voltage-source PWM converter (PWM: Pulse Width Modulation). The DC-side voltage output by converter 12 is the DC bus voltage (DC: Direct Current). Converter 12 performs the conversion to DC power using switching elements such as power semiconductors. Switching elements are provided for each phase.

[0037] The AC reactor 13 is connected to each phase of the input side of the converter 12. The AC reactor 13 suppresses the high-order harmonic components of the AC power input from the system power supply 10 to the converter 12.

[0038] The smoothing capacitor 14 is connected to the output side of the converter 12. The smoothing capacitor 14 smooths the DC power converted by the converter 12.

[0039] Inverter 15 generates three-phase AC power from DC power converted from AC power by converter 12 and smoothed by smoothing capacitor 14. In this example, inverter 15 is a three-phase PWM inverter or the like. Inverter 15 supplies the generated AC power to drive unit 3, which moves car 5. Inverter 15 performs the conversion to AC power using switching elements such as power semiconductors. Switching elements are provided for each phase.

[0040] The control unit 16 controls the movement of the car 5 by controlling the inverter 15 and the converter 12. The control unit 16 can also be separated into a part that controls the inverter 15 and a part that controls the converter 12. For example, the control unit 16 controls the output voltage and output frequency of the inverter 15 based on the speed command value of the motor 8. For example, the control unit 16 controls the DC voltage output by the converter 12 based on the deviation between the command value and the actual value of the DC voltage, such as the DC bus voltage.

[0041] The control unit 16, for example, has a processing circuit as hardware, including a processor 16a and a memory 16b. The processor 16a is, for example, a CPU, a computing device, a microprocessor, or a microcomputer. The memory 16b is, for example, a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, and EEPROM, or a disk, floppy disk, optical disk, high-density disk, mini-disk, or DVD. The memory 16b stores programs, such as software or firmware. Furthermore, the control unit 16 executes the programs stored in the memory 16b through the processor 16a to perform pre-set processing, realizing various functions as a result of hardware and software cooperation. Each function of the control unit 16 can also be implemented by the processing circuit. Alternatively, some or all of the functions of the control unit 16 can be implemented uniformly by the processing circuit. Furthermore, the processing circuit can be implemented, for example, by a single circuit, a composite circuit, a programmable processor, a parallel programmable processor, an ASIC or FPGA, or a combination thereof.

[0042] Figure 2 This is a diagram showing the single-phase equivalent circuit of the converter 12 according to Embodiment 1.

[0043] exist Figure 2 In the middle, the input voltage from system power supply 10 is V in Indicated. The input current from system power supply 10 is determined by I. in Indicated. The voltage applied to AC reactor 13 is determined by V. L Indicated. The voltage on the output side of converter 12 is determined by V. conv express.

[0044] exist Figure 2 In the single-phase equivalent circuit shown, when only the fundamental component is extracted, the instantaneous value v of the input voltage from system power supply 10 is... in [V], instantaneous value of the output voltage from system power supply 10 in [A] and the instantaneous value v of the voltage on the output side of converter 12. conv The relationship of [V] is expressed by the following equation (1a). Here, the inductance of the AC reactor 13 is given by L. ac [H] represents time. Additionally, time is represented by t[s].

[0045] [Formula 1]

[0046]

[0047] Furthermore, let the effective value of the voltage of system power supply 10 be E[Vrms], and let the angular frequency of system power supply 10 be ω. s [rad / s], let the DC bus voltage be Vdc[V], and let the fundamental modulation rate of converter 12 be m. a Let the phase of the voltage of converter 12 be... At this time, the voltage v in and v conv They are represented as shown in equations (1b) and (1c) respectively.

[0048] [Formula 2]

[0049]

[0050] [Formula 3]

[0051]

[0052] According to these equations (1a), (1b), and (1c), the current i in It is represented as shown in equation (1d).

[0053] [Formula 4]

[0054]

[0055] Here, the amplitude I of the effective current component, expressed by equation (2), is used. a The amplitude I of the reactive current component rea .

[0056] [Formula 5]

[0057]

[0058] Based on this, the fundamental modulation rate m of converter 12 is calculated. a When, it is expressed as in equation (3) below.

[0059] [Formula 6]

[0060]

[0061] Let the fundamental frequency modulation rate m of converter 12 be... a The upper limit is m a_max When, it is expressed by the following equation (4a), therefore, the DC bus voltage V dc The lower limit is represented by the following formula (4b).

[0062] [Formula 7]

[0063]

[0064] [Formula 8]

[0065]

[0066] Furthermore, the power P of each phase when the converter 12 is operating in_u Using system power supply cycle T 10 s [s] is represented by the following formula (5a).

[0067] [Formula 9]

[0068]

[0069] Using this formula, the input voltage of converter 12 is represented by the following formula (5b).

[0070] [Formula 10]

[0071]

[0072] When the converter 12 operates at its maximum efficiency point in the maximum power range, the condition of the following equation (6a) is applied to avoid the current flowing with reactive power components.

[0073] [Formula 11]

[0074]

[0075] The conditions of equation (6a) are expressed as shown in equation (6b).

[0076] [Formula 12]

[0077]

[0078] Furthermore, according to equation (5b), the fundamental modulation rate m of converter 12 a Phase with voltage The relationship is expressed as shown in equation (6c).

[0079] [Formula 13]

[0080]

[0081] When using equations (6b) and (6c), the fundamental modulation rate m of converter 12 is... a Phase of voltage It is represented by equations (7) and (8) respectively.

[0082] [Formula 14]

[0083]

[0084] [Formula 15]

[0085]

[0086] Therefore, when the fundamental modulation rate m of converter 12 a Phase of voltage When equations (7) and (8) are satisfied, the power factor of the input side of the converter 12 relative to the system power supply 10 becomes 1, enabling power conversion operation with the minimum current value. The control unit 16 controls the converter 12 by switching between multiple control modes, including the first mode and the second mode. The control mode that sets the power factor of the input side of the converter 12 relative to the system power supply 10 to 1 is an example of the first mode. The power factor of the converter 12 in the first mode is an example of the first power factor. The second mode is a control mode that sets the power factor of the input side of the converter 12 relative to the system power supply 10 to a value lower than 1. The power factor of the converter 12 in the second mode is an example of the second power factor. Although the input current increases by using the second mode, which sets the power factor to a value lower than 1, optimization of the operating mode of the converter 12 relative to the input voltage specification can be achieved.

[0087] In elevator 1, when the power of the car 5 at a constant speed during operation is set to the rated power, the power required for the car 5 to accelerate to its peak is approximately 2 to 2.5 times the rated power, and more power is required depending on the lifting distance of the object or the speed of the car 5. Furthermore, elevator 1 is preferably configured to accommodate various system power supply conditions, such as voltage fluctuations in the system power supply 10. Therefore, in the power conversion device 11 of elevator 1, the converter 12 needs to handle a wide range of input voltages.

[0088] Let the maximum effective value of the input voltage be E. in_max [Vrms], let the minimum effective value of the input voltage be E. in_min [Vrms]. At this time, the power of elevator 1 during operation remains constant relative to any input voltage value. Therefore, according to equation (5b), the maximum value P of the input power at the acceleration peak is... in_max [W] is represented by the following formula (9).

[0089] [Formula 16]

[0090]

[0091] Here, let the input voltage E in_min The effective value of the input current under the condition is I a_Ein_min [Arms], let the input voltage Ein_max The effective value of the input current under the condition is I a_Ein_max [Arms].

[0092] Furthermore, according to equation (9), the input voltage E in_min The effective value of the input current and the input voltage E under the following conditions in_max The relationship between the effective values ​​of the input current under the given conditions is expressed by the following equation (10).

[0093] [Formula 17]

[0094]

[0095] Based on equation (10) and the preconditions, the conditions for equations (11) and (12) are obtained for voltage and current.

[0096] [Formula 18]

[0097] E in_min <E in_max (11)

[0098] [Formula 19]

[0099]

[0100] As shown in equation (9), under the condition of constant power, the input current becomes low when the input voltage is high, and high when the input voltage is low. Therefore, when the input voltage reaches its maximum value E... in_max In the case of elevator 1, within the range of the input voltage of the elevator 1 specification, the input current value is minimized. As a result, compared with the case of the input voltage being other values, the conduction loss of each device can be suppressed.

[0101] On the other hand, in the design of electronic devices, device design is performed for each input voltage. Therefore, as long as each product does not have a large number of devices, the device selection can be made in conjunction with the maximum operating current. Thus, a device with a rated current that can withstand operation when the input voltage is at its minimum is used.

[0102] Therefore, in the second mode, the input voltage input to the converter 12 by the control unit 16 becomes the maximum value E. in_max In this case, reactive power is transferred to the system power supply 10, thereby extending the fundamental modulation rate m expressed by equation (3). aThe range is expanded to replace the increase in the effective value of the input current. Therefore, the application range of the AC reactor 13 as a reactor for PWM converters is broadened. Furthermore, the condition of equation (12) is applied to the input current value increased by the facilitation of reactive power. In addition, in cases where there are power factor constraints due to legal regulations or requirements of the installer, the increased input current value becomes the power factor within that constraint. The above methods were selected.

[0103] Under the above conditions, let the effective value of the current be I when the effective value of the input current is increased. + [Arms]. At this point, according to the condition of equation (12), it becomes I. a_Ein_min ≥I + Therefore, when using the effective value of current I + Effective current component I +_a [Arms] and reactive current component I +_rea [Arms] and power factor angle At that time, the instantaneous value of the current i in_Ein_max_+ [A] is represented by the following formula (13).

[0104] [Formula 20]

[0105]

[0106] RMS current value I + As input power, it needs to satisfy equation (9). This condition is expressed by equation (14).

[0107] [Formula 21]

[0108]

[0109] Furthermore, when the constraint on the power factor is limited by a limit value When expressed, the condition of the constraint is represented by the following formula (15).

[0110] [Formula 22]

[0111]

[0112] Therefore, for the case where the effective value of the input current increases, the effective value of the current I... + The condition is expressed by the following equation (16).

[0113] [Formula 23]

[0114]

[0115] Furthermore, regarding the effective value of the current I when the equality of equation (16) holds... +Effective current component I +_a and reactive current component I +_rea It is represented by equations (17) and (18) respectively.

[0116] [Formula 24]

[0117]

[0118] [Formula 25]

[0119]

[0120] Based on the condition for the converter 12 to operate without overmodulation, i.e., equation (4), the inductance value L of the AC reactor 13, which is the reactor for the PWM converter, is determined. ac+ The limitation is expressed by the following formula (19).

[0121] [Formula 26]

[0122]

[0123] Furthermore, regarding the inductance value L of the AC reactor 13 required without reactive power switching... ac The limitation is that the reactive current component I is reduced in equation (19). +_rea The value is set to 0 and derived as shown in equation (20).

[0124] [Formula 27]

[0125]

[0126] Using equations (19) and (20), the inductance value L in the case of reactive power transfer to system power supply 10 is expressed by equation (21). ac+ The inductance value L when reactive power is not supplied. ac The relationship between them.

[0127] [Formula 28]

[0128] L ac <L ac+ (twenty one)

[0129] As described above, by allowing reactive power to flow into the system power supply 10, the inductance range of the AC reactor 13, which allows the converter 12 to operate in PWM mode without overmodulation, can be expanded. Furthermore, in this operating region, the DC bus voltage at which the converter 12 can operate without overmodulation is represented by equation (4b). Therefore, by allowing reactive power to flow from the converter 12 into the system power supply 10, the control unit 16 reduces the DC bus voltage V. dc .

[0130] Next, specific numerical examples will be given to illustrate the circuit parameters. In this example, let the rated power P of elevator 1 be... in Given a power of 40kW, and assuming the peak acceleration power P... in_max It is 2.5 times the rated power, i.e., 100kW. Furthermore, let the maximum input voltage E be... in_max Given an input voltage of 440Vrms, and assuming a minimum input voltage E... in_min Given a voltage of 380Vrms, and assuming the frequency f of the system power supply 10 is... s Given a frequency of 60Hz, let the angular frequency ω be... s For 2πf s Furthermore, let the commanded value V of the average DC bus voltage between converter 12 and inverter 15 be... dc It is 700V.

[0131] At this point, according to equation (5b), the input voltage is calculated to its maximum value E as shown in equation (22). in_max =440Vrms and the input voltage becomes the minimum value E in_min The current value at 380Vrms.

[0132] [Formula 29]

[0133]

[0134] Here, the input voltage value becomes the maximum value E. in_max The allowance for reactive power at 440Vrms gives a limit to the power factor. The constraints. At this time, according to equations (17) and (18), the effective value of the current I under the condition of reactive power being transferred to the system power source 10 is calculated as follows: equations (23) and (24). + And for the effective value I of this current + Effective current component I +_a and reactive current component I +_rea .

[0135] [Formula 30]

[0136]

[0137] [Formula 31]

[0138]

[0139] Here, the operating range of the fundamental modulation rate for stable PWM operation of converter 12 under maximum line-to-line control also depends on the modulation method and needs to be 0 ≤ m. a ≤2 / √3=ma_max Furthermore, in practice, due to the dead time set in the power semiconductor switch for short-circuit protection, the maximum value of the fundamental modulation rate, i.e., m... a_max A margin is required. With a margin of 5%, the maximum value of the fundamental modulation rate m... a_max The result is 2 / √3×0.95=1.097. At this point, the range of inductance values ​​of AC reactor 13 required for converter 12 to avoid overmodulation can be obtained according to equations (19) and (20).

[0140] exist Figure 3A The diagram shows the upper limit of the inductance of the AC reactor 13 required for the converter 12 to avoid overmodulation.

[0141] Figure 3A This is a diagram showing the operating region of the converter 12 in Embodiment 1 and the upper limit of the inductance of the corresponding AC reactor 13.

[0142] exist Figure 3A In the diagram, the horizontal axis represents the effective value E of the input voltage of system power supply 10. in [Vrms]. The vertical axis represents the upper limit of the inductance L [mH] of the AC reactor 13 required for the converter 12 to avoid overmodulation. Regarding the first mode where reactive power is not supplied to the system power supply 10, i.e., when the power factor is set to 1, the inductance L... ac The upper limit is represented by a solid line. Regarding the second mode of reactive power transfer to system power supply 10, i.e., when the power factor is set to 0.95 (less than 1), the inductor L... ac+ The upper limit is represented by a dashed line.

[0143] In this example, the control unit 16 switches the control mode of the converter 12 based on the relationship between the effective value of the input voltage and the reference value. The reference value is set to, for example, 415Vrms.

[0144] Regarding the cases where reactive power is supplied to system power source 10 and cases where reactive power is not supplied to system power source 10, when the effective value of the input voltage is E... in When the voltage is 440Vrms, the upper limit of the inductance of the AC reactor 13 required for the converter 12 to not become overmodulated is expressed by the following formula (25).

[0145] [Formula 32]

[0146]

[0147] Regarding the cases where reactive power is supplied to system power source 10 and cases where reactive power is not supplied to system power source 10, when the effective value of the input voltage is E... inWhen the current is 415Vrms, the upper limit of the inductance of the AC reactor 13 required for the converter 12 to not become overmodulated is expressed by the following formula (26).

[0148] [Formula 33]

[0149]

[0150] Based on these values, the inductance value of the AC reactor 13 for converter 12 is selected, for example, as L. ac = 2.4mH. At this time, the control unit 16 has an effective value of 380Vrms≤E. in When the voltage is less than 415Vrms, the converter 12 is controlled in mode 1 with a power factor cosφ = 1 at rated power output. Furthermore, the control unit 16 controls the converter 12 when the effective value of the input voltage is 415Vrms ≤ E. in When the voltage is ≤440Vrms, reactive power is allowed to be supplied, and the converter 12 is controlled in mode 2 with a power factor cosφ=0.95 at rated power output. Therefore, the effective value of the input voltage, which is the operating region of the converter 12, is 380Vrms≤E. in In the range of ≤440Vrms, the inductance value of AC reactor 13 is lower than the upper limit used to prevent converter 12 from becoming overmodulated.

[0151] exist Figure 3B The figure shows the input current value from the system power supply 10 in the operating region of the converter 12.

[0152] Figure 3B This is a diagram showing the operating region of the converter 12 in Embodiment 1 and the corresponding input current values.

[0153] exist Figure 3B In the diagram, the horizontal axis represents the effective value E of the input voltage of system power supply 10. in [Vrms]. The vertical axis represents the input current value I from system power supply 10. in [Arms]. Input current value I in the first mode without reactive power transfer to system power supply 10, i.e., with the power factor set to 1. a Represented by a solid line. The input current value I in the second mode of reactive power transfer to system power supply 10, i.e., when the power factor is set to 0.95, which is less than 1. a+ Represented by dashed lines.

[0154] exist Figure 4 The figure shows the DC bus voltage value that can be controlled in the operating region of converter 12.

[0155] Figure 4This is a diagram showing the operating region of the converter 12 in Embodiment 1 and the corresponding DC bus voltage.

[0156] exist Figure 4 In the diagram, the horizontal axis represents the effective value E of the input voltage of system power supply 10. in [Vrms]. The vertical axis represents the DC bus voltage V between converter 12 and inverter 15. dc [V]. The command value V of the DC bus voltage under the normal condition of the first mode (no reactive power transfer to system power supply 10), i.e., setting the power factor to 1. dc_ref Represented by a solid line. The command value V of the DC bus voltage in the second mode of reactive power transfer to system power supply 10, i.e., when the power factor is set to 0.95, which is less than 1. dc_ref (+I rea The value is represented by a dashed line. Furthermore, the commanded value of this DC bus voltage can be freely changed based on equation (4b) according to the allowable reactive current of the system power supply 10. Figure 4 The diagram shows the reactive current I. rea Set it to 20 Arms and set the inductance L of AC reactor 13 to 20 Arms. ac The value is set to 2.4mH.

[0157] Figure 5A and Figure 5B This is a conceptual diagram of the operation of the converter 12 in the first mode of implementation method 1.

[0158] Figure 5A This represents the input waveform of converter 12 in mode 1. Figure 5A In the diagram, the horizontal axis represents time. Figure 5A In the diagram, the vertical axis represents the input voltage v from system power supply 10. in and input current i in .exist Figure 5B In the complex plane, it is represented as Figure 2 The relationship between the amplitude and phase difference of each voltage and current in the equivalent circuit.

[0159] Figure 6A and Figure 6B This is a conceptual diagram of the operation of the converter 12 in the second mode of implementation method 1.

[0160] Figure 6A This represents the input waveform of converter 12 in mode 2. Figure 6A In the diagram, the horizontal axis represents time. Figure 6A In the diagram, the vertical axis represents the input voltage v from system power supply 10. in and input current i in .exist Figure 6B In the complex plane, it is represented as Figure 2The relationship between the amplitude and phase difference of each voltage and current in the equivalent circuit.

[0161] Next, an example of the operation of the power conversion device 11 corresponding to the driving state of the car 5 will be explained.

[0162] Figure 7A and Figure 7B This is a diagram showing an example of the motion waveform in elevator 1 according to embodiment 1.

[0163] exist Figure 7A and Figure 7B In the diagram, the horizontal axis represents time. Furthermore, in... Figure 7A and Figure 7B In the diagram, the graphs, from top to bottom, represent the speed v [m / s] of the car 5, the input power P of the converter 12, and so on. in [W], Input current i of converter 12 in [Arms], and DC bus voltage V dc [V]. In this example, after accelerating from a stationary state and traveling at a constant speed, car 5 decelerates and comes to a stop. Then, after accelerating from a stationary state in the opposite direction and traveling at a constant speed, car 5 decelerates and comes to a stop.

[0164] exist Figure 7B The image shows an example of the operating waveform when the control unit 16 switches the control mode of the converter 12 according to the driving state of the car 5. For comparison, in... Figure 7A The diagram shows an example of the operating waveform when the control unit 16 does not switch the control mode of the converter 12 corresponding to the driving state of the car 5. Figure 7A In this mode, the control unit 16 controls the converter 12 in a first mode where the power factor is set to 1. In this first mode, the control unit 16 sets the command value of the DC bus voltage to 700V. This command value is an example of the first command value.

[0165] like Figure 7B As shown, when the speed of the car 5 approaches 0 and the driving state is close to a stop, or when it is about to stop, the control unit 16 controls the converter 12 in a second mode to facilitate the transfer of reactive power to the system power supply 10. For example, when the speed of the car 5 is less than a preset reference value and the drive unit 3 is activated, the control unit 16 controls the converter 12 in the second mode. In the second mode, the control unit 16 sets the command value of the DC bus voltage to a voltage value lower than 700V. This command value is an example of the second command value.

[0166] Figure 8A and Figure 8B This is a diagram showing an example of the switching waveform of the inverter 15 in the elevator 1 of Embodiment 1.

[0167] exist Figure 8A and Figure 8B In the diagram, the horizontal axis represents time. Furthermore, in... Figure 8A and Figure 8B In the diagram, the vertical axis represents the current and voltage in each switching element of inverter 15. The current in the switching element is, for example, the collector current i. C [A] etc. The voltage in a switching element is, for example, the collector-emitter voltage V. CE [V] etc.

[0168] exist Figure 8B The image shows an example of the switching waveform of the inverter 15 when the control unit 16 controls the converter 12 in the second mode. For comparison, in... Figure 8A The image shows an example of the switching waveform of the inverter 15 when the control unit 16 controls the converter 12 in the first mode.

[0169] In mode 2, the commanded value of the DC bus voltage is lower than that in mode 1; therefore, the DC bus voltage is lower than when converter 12 is controlled in mode 1. Therefore, as... Figure 8B As shown, the voltage v applied to the switching elements of inverter 15 decreases along with the DC bus voltage. CE The voltage also decreases. This suppresses switching losses in inverter 15. Furthermore, common-mode voltage oscillations generated by the switching operations in inverter 15 and converter 12 are reduced along with the decrease in DC bus voltage. This suppresses common-mode noise originating from the DC bus voltage.

[0170] As described above, the power conversion device 11 of Embodiment 1 includes a converter 12, an AC reactor 13, a smoothing capacitor 14, an inverter 15, and a control unit 16. The converter 12 converts input AC power into DC power. The AC reactor 13 is connected to the input side of the converter 12. The smoothing capacitor 14 is connected to the output side of the converter 12. The inverter 15 generates AC power based on the DC power converted from AC power by the converter 12 and smoothed by the smoothing capacitor 14, and supplies it to the drive unit 3 that moves the elevator car 5. The control unit 16 controls the movement of the car 5 by controlling the inverter 15 and the converter 12. When the car 5 is traveling at a speed above a reference value, the control unit 16 sets the control mode of the converter 12 to mode 1. When the car 5 is traveling at a speed below the reference value, the control unit 16 sets the control mode of the converter 12 to mode 2. The first mode is a control mode in which the converter 12 operates according to a preset first power factor. The second mode is a control mode in which the converter 12 operates according to a second power factor that is lower than the first power factor. Furthermore, the control unit 16 sets the command value of the DC voltage output by the converter 12 in the second mode to be lower than the command value of the DC voltage output by the converter 12 in the first mode.

[0171] In elevators, power conversion devices sometimes incorporate three-phase voltage-source PWM converters, enabling efficient utilization of generated regenerative power. Power conversion devices using three-phase voltage-source PWM converters typically control the input current from the AC system power supply and the DC bus voltage between the converter and the inverter to operate the converter. In this case, the power conversion device typically operates by setting the fundamental power factor of the input current to allow the converter to operate at its maximum efficiency point, controlling the DC bus voltage to a value greater than the maximum value of the AC voltage of the system power supply. On the other hand, the power during the car's lifting and lowering varies significantly depending on the operating state. For example, the maximum power during acceleration relative to the rated power when the car is traveling at a constant speed is determined by the system and is 1.5 to 2.5 times, sometimes even higher. Therefore, the inductance value of the AC reactor used in the converter is typically selected as a small value inversely proportional to the power. However, decreasing the inductance value of the AC reactor leads to an increase in current ripple. Furthermore, in the operation of a three-phase voltage-source PWM converter, the DC bus voltage between the inverter and the drive motor is typically controlled at a higher value than the system power supply voltage. On the other hand, when the car is running at low speed or about to stop, the inverter operates at this higher voltage, thus increasing losses in the power conversion device. When the car is nearing a stop, the motor current phase remains almost unchanged, so losses may concentrate on specific phase switching elements. Moreover, due to the low modulation rate of the inverter, the output voltage pulses to the motor are shorter, making it easier to generate common-mode noise and surge voltage.

[0172] In contrast, in the power conversion device 11, the control unit 16 is set to a second mode for transferring reactive power to the system power supply 10 when the car 5 is nearing a stop, controlling the converter 12 with a power factor lower than 1. This allows the DC bus voltage to drop when the car 5 is nearing a stop. By reducing the DC bus voltage, switching losses in the inverter 15 are suppressed, as are the common-mode noise.

[0173] In summary, the possible structures of the technology disclosed herein include the following structures shown as appendices.

[0174] (Postscript 1)

[0175] A power conversion device, wherein,

[0176] The power conversion device includes:

[0177] A converter, which converts input alternating current (AC) power into direct current (DC) power;

[0178] An AC reactor is connected to the input side of the converter;

[0179] A smoothing capacitor is connected to the output side of the converter;

[0180] An inverter that generates AC power from DC power converted from AC power by the converter and smoothed by the smoothing capacitor, and supplies it to a drive unit that moves the elevator car; and

[0181] The control unit controls the movement of the car through the control of the inverter and the converter.

[0182] When the car's travel speed is above a preset reference value, the control unit sets the converter's control mode to a first mode that causes the converter to operate with a preset first power factor. When the car's travel speed is below the reference value, the control unit sets the converter's control mode to a second mode that causes the converter to operate with a second power factor that is lower than the first power factor.

[0183] (Postscript 2)

[0184] According to the power conversion device described in Appendix 1, wherein,

[0185] In the first mode, the control unit sets the command value of the DC voltage output by the converter to a preset first command value, and in the second mode, sets the command value of the DC voltage output by the converter to a second command value that is lower than the first command value.

[0186] Explanation of reference numerals in the attached figures

[0187] 1. Elevator, 2. Shaft, 3. Drive unit, 4. Main rope, 5. Car, 6. Counterweight, 7. Control unit, 8. Motor, 9. Drive pulley, 10. System power supply, 11. Power conversion device, 12. Converter, 13. AC reactor, 14. Smoothing capacitor, 15. Inverter, 16. Control unit, 16a. Processor, 16b. Memory.

Claims

1. A power conversion device, wherein, The power conversion device includes: A converter, which converts input alternating current (AC) power into direct current (DC) power; An AC reactor is connected to the input side of the converter; A smoothing capacitor is connected to the output side of the converter; An inverter that generates AC power from DC power converted from AC power by the converter and smoothed by the smoothing capacitor, and supplies it to a drive unit that moves the elevator car. as well as The control unit controls the movement of the car through the control of the inverter and the converter. When the car's travel speed is above a preset reference value, the control unit sets the converter's control mode to a first mode that causes the converter to operate with a preset first power factor. When the car's travel speed is below the reference value, the control unit sets the converter's control mode to a second mode that causes the converter to operate with a second power factor that is lower than the first power factor.

2. The power conversion device according to claim 1, wherein, In the first mode, the control unit sets the command value of the DC voltage output by the converter to a preset first command value, and in the second mode, sets the command value of the DC voltage output by the converter to a second command value that is lower than the first command value.

Images