JP6177034B2 - Elevator equipment - Google Patents

Description

  The present invention relates to a drive system for an AC motor that drives an AC motor by a parallel multiplexed inverter, and an elevator apparatus using the drive system.

  Conventionally, when realizing a large-capacity AC variable speed drive system for driving a high-speed or large elevator device, etc., the power capacity is increased by multiplexing unit power converters that perform pulse width modulation control using semiconductor switching elements. As an example of multiplexing, there is a power conversion system in which a plurality of unit power conversion devices are connected in parallel and parallel operation is performed based on the same three-phase voltage command.

  In such a power conversion system, in general, a delay time is generated in the voltage command due to the operation delay of the control circuit and the variation in the switching speed of the semiconductor switching element. When a difference occurs in the voltage command of a plurality of unit power converters connected in parallel due to a delay time, a different signal is input to the gates of the upper and lower arms, and a circulating current flows between the unit power converters.

  FIGS. 6A to 6D show examples of circulating current paths when two unit power converters are connected in parallel. The circulating current flows to the inverter side in FIGS. 6 (a) and 6 (b), and flows to the converter side in FIGS. 6 (c) and 6 (d). In each figure, a circuit for one phase of an inverter and a converter included in the circulation current path is illustrated. As shown in FIGS. 6A and 6B, when the circulating current flows through the inverter side, the upper arm of one unit power converter, the AC output, the lower arm of the other unit power converter, and a smoothing capacitor It flows on the route including. 6C and 6D, when the circulating current flows through the converter side, the upper arm of one unit power converter, the power input, the lower arm of the other unit power converter, and It flows along the path including the smoothing capacitor. Such a circulating current increases the power loss of the power conversion system and causes not only torque pulsation but also equipment failure.

  As a conventional technique related to parallel multiplexing and the suppression of circulating current associated therewith, there are techniques described in Patent Document 1 and Patent Document 2.

  In the technique described in Patent Document 1, a power conversion circuit including a converter circuit, an inverter circuit, and a smoothing circuit is provided, and two power conversion circuits that are controlled in three-phase modulation are connected in parallel. Further, in the present technology, the circulating current component of the current flowing through the inverter side or the converter side is detected, and a compensation amount is added to the voltage command so that the detected circulating current approaches zero.

  In the technique described in Patent Document 2, a plurality of three-phase inverters that are controlled in two-phase modulation are connected in parallel. Further, in the present technology, in order to suppress the circulating current between the inverters, current control is performed on the phase current while outputting the line voltage based on the stationary phase.

JP 2003-134833 A JP 2004-364351 A

  When an AC motor is driven by a parallel multiplexed inverter device, a three-phase modulation method is generally used as a control method for the power conversion device. In order to reduce the switching loss by reducing the number of switching times of each switching element. In some cases, a two-phase modulation method is used. In the two-phase modulation method, an upper arm and a lower arm of one phase of the three phases are always on (off) and always off (on), respectively, and the other two phases are PWM-controlled during a predetermined period. For this reason, there are 3n (n: natural number) modes of voltage command patterns for three phases, for example, 12 modes, and the modes are sequentially switched. When there is a difference in the voltage command between the power conversion devices during this mode switching, the amount of change in the output voltage becomes larger than in the case of the three-phase modulation method, so that a large circulating current flows. In particular, the circulating current increases in a region where the amount of change in output voltage between the power converters is large and the modulation rate is low.

  FIG. 7A and FIG. 7B show examples of the waveform of the circulating current studied by the present inventors. FIG. 7B is an enlarged view of the time axis of FIG. In each figure, when two inverters are connected in parallel, the waveform of the voltage command of the first inverter, the waveform of the voltage command of the second inverter, and the waveform of the circulating current are shown from the top. From this figure, it can be seen that the circulating current increases in the control section when the voltage command mode is switched.

  On the other hand, when the technique disclosed in Patent Document 1 is applied, when the timing for adding the compensation amount for suppressing the circulating current to the voltage command is in the vicinity of the mode switching time, the voltage command is originally based on the added compensation amount. Transition to a mode different from the control section. For this reason, when the mode of a control section differs between each power converter, the effect of circulating current suppression control cannot fully be acquired.

  Further, in the technique disclosed in Patent Document 2, since LC filters having the same impedance are connected to each power conversion device, the number of components increases, the power conversion device becomes larger and the cost increases.

  Therefore, the present invention drives an AC motor that can reliably suppress the circulating current between the inverters without increasing the size of the device or increasing the cost when the AC motor is driven by a parallel multiplexed inverter controlled by two-phase modulation. A system and an elevator apparatus using the system are provided.

In order to solve the above problems, an elevator apparatus according to the present invention comprises a sheave, a rope wound around the sheave, the car that the sieve is driven vertically by said rope which is driven to rotate, the, ac The sheave is rotationally driven by a motor drive system, and the AC motor drive system includes a first power converter and a second power converter connected in parallel, the first power converter and the second power. An AC electric motor driven by a converter, wherein the first power converter has a first inverter unit that is controlled by two-phase modulation, and the second power converter is controlled by two-phase modulation. The first power converter includes a first converter unit having a DC output connected to a DC input of the first inverter unit, and the second power unit. The force conversion device includes a second converter unit in which a DC output is connected to a DC input of the second inverter unit, and is connected to the DC output of the first converter unit and the DC output of the second converter unit. The AC motor has a first three-phase winding which is fixedly Y-connected and a second three-phase winding whose connection state is changed during normal operation and during an emergency stop test. In the normal operation, the second three-phase winding is Y-connected, and neutral points and terminals between the first three-phase winding and the second three-phase winding are electrically separated, At the time of the emergency stop test, the connection state of the second three-phase winding is changed so that the first three-phase winding and the second three-phase winding are in one Y connection. The first three-phase winding is connected to the AC output of the first inverter unit, and the second The phase winding is connected to the AC output of the second inverter unit, and the first converter unit is three-phase so that the zero-phase current component of the current flowing on the AC input side of the first converter unit approaches zero. The second converter unit is modulation-controlled and three-phase modulation controlled so that the zero-phase current component of the current flowing on the AC input side of the second converter unit approaches zero .

  According to the present invention, since the path of the circulating current on the inverter side is opened by the AC motor having the double winding, the circulating current flowing on the inverter side is suppressed. For this reason, it is possible to suppress the circulating current without adding any special change such as addition of new parts in the power conversion apparatus connected in parallel and thus without increasing the size and cost of the apparatus. Further, according to the present invention, the reliability of the elevator apparatus can be improved without increasing the size of the elevator apparatus and increasing the cost.

  Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.

1 shows a drive system for an AC motor according to a first embodiment of the present invention. The voltage mode conditions for two-phase modulation control are shown. The voltage command waveform of two-phase modulation control is shown. It is a connection diagram of the coil | winding of the three-phase alternating current motor at the time of the normal driving | operation of an elevator. It is a connection diagram of the coil | winding of a three-phase alternating current motor at the time of an emergency stop test driving | operation. The electric current path in which a circulating current is suppressed in Example 1 is shown. The electric current path in which a circulating current is suppressed in Example 1 is shown. The electric current path in which a circulating current is suppressed in Example 1 is shown. The electric current path in which a circulating current is suppressed in Example 1 is shown. The drive system of the alternating current motor which is the 2nd example of the present invention is shown. An example of the path | route of the circulating current in the power converter device connected in parallel is shown. An example of the path | route of the circulating current in the power converter device connected in parallel is shown. An example of the path | route of the circulating current in the power converter device connected in parallel is shown. An example of the path | route of the circulating current in the power converter device connected in parallel is shown. The example of a waveform of a circulating current is shown. It is an enlarged view of Fig.7 (a).

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an AC motor drive system according to a first embodiment of the present invention. This drive system is for elevator drive.

  In this embodiment, the power converter 31 and the power converter 32 connected in parallel convert the three-phase AC power having a constant voltage and a constant frequency input from the commercial power supply 11 into a three-phase AC power having a variable voltage and a variable frequency. Output. The three-phase AC motor 21 is driven by the output three-phase AC power. Although the three-phase AC motor 21 includes double windings, the circulating current flowing between the power converters is suppressed as described later. As the three-phase AC motor 21, an induction motor, a permanent magnet synchronous motor, or the like is used.

  In the elevator in this embodiment, the rope 45 is wound around the sheave 41 and the pulley 46, and the counterweight 42 and the car 43 are attached to both ends of the rope 45. A balance chain 47 wound around the pulley 44 is attached to the lower part of the car 43 and the balance weight 42. In this elevator, the sheave 41 is rotated by the AC motor 21 to drive the rope 45, and the car 43 moves up and down in the hoistway.

  The power conversion device 31 includes a converter unit 151 that converts three-phase AC power input from the commercial power supply 11 into DC power, and an inverter unit 152 that converts DC power output from the converter unit 151 into three-phase AC power. The AC input of the converter unit 151 is connected to the commercial power supply 11 via the filter 121. The DC output of converter unit 151 and the DC input of inverter unit 152 are connected to each other. A smoothing capacitor 161 is connected to the DC output of the converter unit 151. The AC output of the inverter unit 152 is connected to one of the double windings of the three-phase AC motor 21 via the filter 122. Note that the upper and lower arms of each phase in the main circuit of the converter unit 151 and the inverter unit 152 are constituted by an antiparallel circuit of a semiconductor switching element and a diode. In this embodiment, an IGBT (Insulated Gate Bipolar Transistor) is used as the semiconductor switching element, but other switching elements such as MOSFETs may be used. The configuration including the inverter unit and the converter unit in this way is a configuration suitable for a power conversion device that drives a large-capacity AC motor used in a high-speed elevator or the like.

  Converter section 151 and inverter section 152 in power conversion device 31 are controlled by controller 141 and controller 142, respectively, by two-phase modulation pulse width modulation control (hereinafter referred to as PWM control). Specifically, the controller 141 controls the converter unit 151 so that the converter unit 151 outputs a predetermined DC voltage based on the current flowing in the AC input of the converter unit 151 detected by the power supply side current detector 131. A control signal for ON / OFF control of the semiconductor switching element is created. Further, the controller 142 controls the semiconductor of the inverter unit 152 so that the rotational speed of the AC motor 21 follows the speed command value based on the current flowing in the AC output of the inverter unit 152 detected by the motor-side current detector 132. A control signal for ON / OFF control of the switching element is created.

  The circuit configuration of the other power conversion device 32 includes the same circuit configuration as that of the power conversion device 31 described above. However, the three-phase AC output of the power converter 32, that is, the AC output of the inverter unit of the power converter 32 is connected to the other of the double windings of the AC motor 21. That is, the three-phase AC outputs of the power converters 31 and 32 are connected to different windings of the AC motor 21, respectively. As will be described later, the power converters 31 and 32 can have a common smoothing capacitor. However, in this embodiment, the power converters 31 and 32 each have an independent smoothing capacitor.

  Here, the two-phase modulation control will be briefly described.

  FIG. 2A shows the voltage mode conditions for two-phase modulation control. FIG. 2B shows the first voltage command waveform and the second voltage command waveform from the top, and shows the correspondence between each waveform and the voltage mode. The first voltage according to the intermediate value of the first voltage command value (Vu *, Vv *, Vw *) corresponding to each output phase shown in the upper diagram of FIG. 2B and the polarity of the intermediate value. One period of the command waveform is divided into 3n (n: natural number) as shown in FIG. 2A, and in this embodiment, 12 voltage modes. In each mode, when the intermediate value is negative, the upper arm of the phase having the maximum first voltage command value is always turned on and the lower arm is always turned off. When the intermediate value is positive, the first voltage As shown in the lower diagram of FIG. 2B, the second voltage command for comparison with the triangular wave in the PWM control so that the upper arm is always turned off and the lower arm is always turned on at the phase where the command value is minimum. (Vu, Vv, Vw) is created by a known calculation method (see, for example, Japanese Patent Application Laid-Open No. 2011-114991). In each voltage mode, one of the second voltage command values (Vu, Vv, Vw) is maintained at a voltage value equal to the maximum value or the minimum value of the triangular wave carrier. In this region, the corresponding semiconductor switching element is always on or always off, so that no switching loss occurs. Therefore, the power loss generated in the drive system of this embodiment in which a large number of semiconductor switching is controlled to be turned on / off by parallel multiplexing is reduced.

  Next, an AC motor provided with a double winding in the present embodiment will be described.

  FIGS. 3A and 3B show the connection state of the double windings provided in the three-phase AC motor 21 in this embodiment. FIG. 3A is a connection diagram during normal operation of the elevator, and FIG. 3B is a connection diagram during an emergency stop test operation. The three-phase AC motor in the present embodiment includes terminals U2, V2, and W2, three-phase windings that are fixedly Y-connected, terminals U1, V1, and W1, and is used during normal operation and an emergency stop test. It has a three-phase winding that can change the connection state.

  As shown in FIG. 3A, during a normal operation, the three-phase windings having terminals U1, V1, and W1 are Y-connected. Here, in the AC motor, the Y connection terminals U1-U2, V1-V2, W1-W2, and neutral points are electrically insulated. That is, the three-phase AC motor in the present embodiment has a double winding structure including two Y connections that are electrically separated. The terminals U1, V1, W1 of the AC motor are connected to the AC output of the power converter 31 in FIG. The terminals U2, V2, W2 of the AC motor are connected to the AC output of the power converter 32 in FIG. As a result, as will be described later, since the outputs of the power conversion devices 31 and 32 are separated, the circulation current path is electrically opened on the inverter side. Therefore, the circulating current on the inverter side can be suppressed.

  Next, in the emergency stop test operation, as shown in FIG. 3B, terminals U1, V1, and W1 are provided on the neutral point side of each phase of the three-phase winding that is Y-connected during normal operation. Terminals X1, Y1, and Z1 are short-circuited with terminals U2, V2, and W2, respectively. As a result, one Y-connection is formed in which the number of turns of the windings of each phase is twice that in normal operation. For this reason, since the magnetic flux generated when a predetermined current flows in each phase is twice that in normal operation, it is possible to generate twice the torque in normal operation. During the emergency stop test operation, the power converter motors 31 and 32 are connected in parallel to one Y connection. Therefore, the control of each power converter is switched to the three-phase modulation type PWM control, and the inverter unit and the converter unit are controlled so that the zero-phase current component of the current detected by each current detector approaches zero.

  Hereinafter, the operation of this embodiment will be described.

  4A to 4D show current paths in which the circulating current is suppressed in this embodiment. Each figure shows the case where the voltage command of the converter unit is the same between the power conversion device 31 and the power conversion device 32, and the voltage command of the inverter unit is not the same between the power conversion device 31 and the power conversion device 32. ing. For simplification, only one phase is shown.

  As shown in each figure, in the inverter unit, the voltage command does not match between the power conversion device 31 and the power conversion device 32, so the semiconductor in the upper arm of one power conversion device and the lower arm of the other power conversion device A state occurs in which the switching elements are simultaneously turned on. A path comprising these semiconductor switching elements, an upper arm or a lower arm in the converter unit, an AC input of the converter unit connected in parallel, and a loop passing through one smoothing capacitor and the AC motor has a double winding. It is electrically opened by an electric motor. For this reason, the circulating current flowing through this path is suppressed. Even when the converter voltage command does not match between the power converter 31 and the power converter 32, the circulating current is similarly suppressed.

  In the present embodiment, the inverter-side path is opened by the AC motor provided with the double winding, so that the circulating current flowing to the inverter side is suppressed. Furthermore, in this embodiment, since the smoothing capacitor is provided independently for each power converter, the path of the circulating current is a loop including the converter side and the inverter side. For this reason, as shown in FIGS. 4A to 4D, when the path on the inverter side is opened by the electric motor having the double winding, the path including the power input side of the converter unit is opened. Is done. Thereby, the circulating current on the power supply side can also be suppressed. In this embodiment, the switching loss of the entire power conversion device is reduced by controlling the converter unit also by the two-phase modulation control. Similarly, the three-phase modulation control also suppresses the circulating current on the converter side. Can do.

  In addition, according to the present embodiment, the circulating current can be suppressed without adding parts such as a filter by using a double winding as the winding of the electric motor. For this reason, the reliability of the drive system of the AC motor in which the power conversion device including the inverter unit that is multiplexed in parallel is multiplexed in parallel can be improved without causing an increase in size and cost of the device. Furthermore, by using such an AC motor drive system for an elevator apparatus, the reliability of the elevator apparatus can be improved without increasing the size of the apparatus and increasing the cost.

  FIG. 5 shows a drive system for an AC motor that is a second embodiment of the present invention. In this figure, the converter units 151a and 151b (CONV) and the inverter units 152a and 152b (INV) are not shown in a specific main circuit configuration and are shown in a block diagram. In addition, description of the elevator part is omitted. Moreover, the controller of the power converter 32 and the power source side current detector are the same as those of the power converter 31, and the description is omitted.

  As in the first embodiment of FIG. 1, the inverter unit 152a of the power conversion device 31 is PWM-controlled by the controller 142a by the two-phase modulation method, and the inverter unit 152b of the power conversion device 32 is also controlled by the controller (not shown). PWM control. In addition, the AC outputs of inverter units 152a and 152b are connected to one and the other windings of three-phase AC motor 21 having double windings, respectively. Thereby, similarly to Example 1, the circulating current which flows into the inverter part side can be suppressed.

In the present embodiment, unlike the first embodiment, the smoothing capacitor 161 is connected to both the DC output of the converter unit 151 a of the power converter 31 and the DC output of the converter unit 152 a of the power converter 32. That is, the power converter 31 and the power converter 32 share a smoothing capacitor. For this reason, the controller 141a sets the converter 151a of the power converter 31 to the three-phase modulation method so that the zero-phase component of the current detected by the power supply-side current detector 131 approaches the current command value I ₀ ^*, that is, zero. PWM control. Similarly, a controller (not shown) of the converter unit 151b of the power converter 32 causes the converter unit 151b to be three-phase modulation so that the zero-phase component of the current detected by the power source-side current detector (not shown) approaches zero. PWM control is performed. Thereby, the circulating current which flows into the converter part side, ie, the power supply side, can be suppressed.

  The converter unit may be simply subjected to three-phase modulation control without applying the circulating current suppression control as described above. Also in this case, since the inverter side path is opened by the AC motor having the double winding, the circulating current flowing to the inverter side is suppressed. In general, since the loss of the converter is smaller than that of the inverter, the power loss of the power converter can be reduced by adopting a two-phase modulation system for the inverter.

  In addition, this invention is not limited to each embodiment mentioned above, Various modifications are included. For example, each of the above-described embodiments has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. A part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and further, the configuration of another embodiment can be added to the configuration of an embodiment. Furthermore, it is possible to add, delete, or replace other configurations for a part of the configuration of each embodiment.

  For example, in the first and second embodiments, another DC power source such as a diode rectifier may be used instead of the converters 151a and 151b. In the second embodiment, DC power may be input to the inverter units 152a and 152b multiplexed in parallel by one converter unit, one diode rectifier, or one other DC power source. Also in these cases, the inverter-side path is opened by the AC motor provided with the double winding, so that the circulating current flowing to the inverter side is suppressed.

  The winding connections shown in FIGS. 3 (a) and 3 (b) are not limited to elevator three-phase AC motors, and drive loads having an operation mode that requires a larger torque than during normal operation. It can also be applied to three-phase AC motors.

DESCRIPTION OF SYMBOLS 11 ... Commercial power supply 21 ... Three-phase alternating current motor 31, 32 ... Power converter 41 ... Sheave 42 ... Balance weight 43 ... Carriage 44 ... Pulley 45 ... Rope 46 ... Pulley 47 ... Balance chain 121, 122 ... Filter part 131 ... Power supply Side current detector,
141, 142... Inverter controllers 151, 151a, 151b...
152, 151a, 152b ... Inverter part 161 ... Smoothing capacitor

Claims (1)

In an elevator apparatus comprising a sheave, a rope wound around the sheave, and a ride that is driven up and down by the rope that is driven when the sheave rotates,
The sheave is rotationally driven by an AC motor drive system,
The drive system for the AC motor is:
A first power converter and a second power converter connected in parallel;
An AC motor driven by the first power converter and the second power converter;
With
The first power conversion device has a first inverter unit that is controlled by two-phase modulation, and the second power conversion device has a second inverter unit that is controlled by two-phase modulation,
The first power conversion device includes a first converter unit having a DC output connected to a DC input of the first inverter unit, and the second power conversion device has a DC output of a DC of the second inverter unit. A second converter connected to the input;
A smoothing capacitor connected to the DC output of the first converter unit and the DC output of the second converter unit;
The AC motor has a first three-phase winding fixedly Y-connected, and a second three-phase winding whose connection state is changed between a normal operation and an emergency stop test. The second three-phase winding is Y-connected, and neutral points and terminals between the first three-phase winding and the second three-phase winding are electrically separated. The connection state of the second three-phase winding is changed so that the first three-phase winding and the second three-phase winding become one Y connection,
During the normal operation,
The first three-phase winding is connected to the AC output of the first inverter unit, and the second three-phase winding is connected to the AC output of the second inverter unit;
In addition, the first converter unit is three-phase modulation controlled so that the zero-phase current component of the current flowing on the AC input side of the first converter unit approaches zero, and the second converter unit includes the second converter An elevator apparatus characterized in that three-phase modulation control is performed so that the zero-phase current component of the current flowing on the AC input side of the section approaches zero.

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