JP2013247833A - Electric motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric motor drive device which can properly reconnect AC motors free-running at rotation speeds differing between groups and can restore them to a steady state in as short time as possible.SOLUTION: The electric motor drive device comprises: an inverter device 2; a plurality of branch switches 31, 32 and 33 which branch a plurality of AC motors into a plurality of motor groups 41, 42 and 43 so that they are separately supplied with power; reconnection control means 7 which exerts control to drive the AC motors again when the inverter device 2 is restored from abnormality; frequency detectors 71, 72 and 73 which are each connected to the output sides of the plurality of branch switches; and reconnection computation means 8 which computes a condition necessary for reconnection on the basis of the signals of the frequency detectors 71, 72 and 73 and gives the result of computation to the reconnection control means 7. When the inverter device 2 is restored from abnormality, the reconnection computation means 8 computes an inverter frequency condition at reconnection time for the inverter 2 not to be overloaded and a closing condition for the branch switches 31, 32 and 33 to be closed.

Description

  The present invention relates to a motor drive device that drives a plurality of AC motors in parallel.

  In a motor drive device that drives a plurality of AC motors as a load, when a power failure or a drive device failure occurs, the load is once in a free-run state. When reconnecting a free-running load with a drive device, restarting at the frequency before the occurrence of an abnormality and connecting all loads, the capacity required for the drive device increases and the device becomes huge. For this reason, a method is adopted in which load connections are sequentially entered in a predetermined sequence divided into a plurality of activation groups. (For example, refer to Patent Document 1).

JP 2002-204554 A (page 4-5, FIG. 1)

  In the drive device reconnection method disclosed in Patent Document 1, once an abnormal signal indicating a power failure or a drive device failure occurs, the load once enters a free-run state. In this case, the branch switch provided above the plurality of motor groups is closed and all the AC motors are free-runned while being connected in parallel. It is assumed that when the free-run is performed in this manner, all the AC motors in the free-run are in a state of being synchronized at the same rotational speed by the synchronization force of the AC motor. Under this premise, overload at the time of reconnection of the drive device is prevented by matching the output frequency of the drive device to the frequency of the AC motor during free running at the time of restart after the abnormal signal is removed.

  However, in reality, due to variations in load torque during free running of a plurality of AC motors, an AC motor that falls out of synchronization appears after a predetermined time has elapsed. In order to prevent such a dropout, it is necessary to create several groups with similar load torque magnitudes, separate them between the groups, and free-run only the AC motors belonging to each group in a synchronized state. . In such a case, a method for appropriately restarting by reconnection and returning to a steady state in as short a time as possible remains as an examination subject.

  The present invention has been made in view of the above problems, and can properly reconnect AC motors that are free-running at different rotational speeds between groups, and can return to a steady state in as short a time as possible. It is an object to provide a drive device for a vehicle.

  In order to achieve the above object, an electric motor drive device according to the present invention includes an inverter device for driving a plurality of AC motors, and an output side of the inverter device. A plurality of branch switches for branching and feeding power to the motor group, and when the inverter device has stopped abnormally, the plurality of branch switches are opened, and when this abnormality is recovered, the AC motor is driven again. A connection control means; a frequency detector connected to each of the output sides of the plurality of branch switches; and a condition for reconnection based on a frequency signal supplied from the frequency detector; Reconnection calculation means for giving a calculation result to the means, and the reconnection calculation means is configured such that when the abnormality of the inverter device is restored, the inverter Location is characterized in that so as to calculate the charged condition of the branch switch and inverter frequency conditions at the time of re-connection, such as not to overload.

  According to the present invention, it is possible to provide an electric motor drive device capable of appropriately reconnecting AC motors that are free-running at different rotational speeds between groups and returning them to a steady state in as short a time as possible. It becomes possible.

1 is a system configuration diagram of an electric motor drive device according to Embodiment 1 of the present invention. FIG. Operation | movement explanatory drawing of the drive device for electric motors which concerns on Example 1 of this invention. Operation | movement explanatory drawing of the drive device for electric motors which concerns on Example 2 of this invention. Operation | movement explanatory drawing of the drive device for electric motors which concerns on Example 3 of this invention.

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

  Hereinafter, a motor drive device according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  1 is a system configuration diagram of a motor drive device according to a first embodiment of the present invention. The inverter device 2 converts the alternating voltage supplied from the alternating current power source 1 into direct current by the converter 21, converts it to alternating current again by the inverter 22, and outputs it. The motor groups 41, 42, and 43 are driven by the outputs of the inverter device 2 via the branch switches 31, 32, and 33, respectively. The motor group 41 includes individual switches 611,... 61N for branching the inputs in parallel, AC motors 511,... 51N connected to each of these individual switches 611,. It is comprised from the frequency detector 71 which detects a rotation frequency by the frequency of the counter electromotive voltage of AC motor 511, ... 51N in the free run when 31 is turned off. Similarly, the motor group 42 includes individual switches 621,... 62N for branching the inputs in parallel, and AC motors 521,... 52N and frequency detectors connected to each of the individual switches 621,. 72, and the motor group 43 includes individual switches 631,... 63N that branch the inputs in parallel, and AC motors 531,. It comprises a detector 73.

  In the inverter device 2, the return operation after an abnormal stop is controlled by the reconnection controller 7, and the reconnection controller 7 exchanges signals with the reconnection calculator 8 to control the return operation. Output signals from the frequency detectors 71, 72, and 73 are given to the reconnection calculator 8. The inverter device 2 has a control device for performing normal control, but this illustration is omitted in FIG.

  Next, the operation will be described with reference to the operation explanatory diagram of FIG. It is assumed that the inverter device 2 is abnormally stopped at time t = T1 while the inverter device 2 is operating the motor groups 41, 42, and 43 at the rated frequency. Here, an abnormality is a stop due to a failure or a power failure, but here a power failure occurs. When the abnormality signal is received, the reconnection controller 7 opens the branch switches 31, 32, and 33 to free-run the motor groups 41, 42, and 43. As shown in FIG. 2, the motor groups 41, 42, and 43 are synchronized within the group and decelerate gradually between the groups. FIG. 2 shows an example in which the load of the motor group 41 is the lightest and the load of the motor group 43 is the heaviest. The AC motor here is assumed to be a hysteresis motor having the characteristics of a synchronous motor during synchronous operation and an induction motor during sliding operation, but may be an induction motor having a large residual voltage.

  Next, it is assumed that the power supply is restored at time t = T2 and the abnormal signal is reset. At this time, the reconnection computing unit 7 overloads the inverter device 2 by reconnecting from the output signals of the frequency detectors 71, 72, 73, that is, the rotational frequency of the motor groups 41, 42, 43 at that time. It is calculated whether all groups can be accelerated to the original rated speed in a short time, and the result is given to the reconnection controller 7.

  The calculation contents in this case will be described with reference to FIG. First, the load characteristics of each motor group can be found from the free run characteristics from time T1 to time T2. However, the moments of inertia of each AC motor and its load body are all equal. If the output torque characteristic and the input current characteristic of the AC motor when it is re-introduced at a predetermined frequency are given in advance, for example, in the state where the inverter frequency is lowered from the rated fr to the fres as shown in FIG. The restart characteristics when the groups 41, 42, and 43 are connected and reconnected can be simulated. As shown in the figure, the rotation frequency of all the groups reaches fres at t = T3, and the rebooting to fres is completed. . The output torque and input current of the AC motor being restarted are considerably larger than those at the rated operation, for example, three times. Therefore, in FIG. 2, the inverter output current is the largest during the period in which all the motor groups are accelerating, and the inverter output current decreases every time the motor groups complete acceleration, and t = It becomes a steady current at the time of T3. In general, the steady current is considerably lower than the rated current of the inverter.

  The point in the above restart operation is whether or not the thermal load of the inverter device 2 due to the acceleration current in the first restart time from T2 to T3 is a problem level. Here, the first restart time is a synchronization arrival time when restarting at a constant restart frequency, and this is simply referred to as a synchronization arrival time. As a method for checking the above level, the temperature of the junction part of the semiconductor element constituting the inverter device 2 is obtained by simulation from the change in the inverter output current during the synchronous arrival time from T2 to T3. It is possible not to. As a simpler calculation method, the overload capability characteristic of the inverter device 2 is determined by the effective current with respect to the overload duration, and the effective value of the inverter output current in the synchronous arrival time from T2 to T3 in FIG. Judgment can be made based on whether the current is within the range. In other words, the upper limit fmax of the restart frequency capable of simultaneously reconnecting all the motor groups can be obtained by performing such calculation. Thus, when the upper limit fmax of the restart frequency is equal to or higher than the rotational frequency fm of the motor group having the highest rotational speed at the time of reconnection, the restart frequency fres may be selected in the range of fm <fres <fmax. Here, when the calculated value of fmax is equal to or higher than the inverter rated frequency fr, the above range is set to fm <fres ≦ fr.

  After t = T3 when all the motor groups have reached the restart frequency fres by the above method, the output frequency of the inverter device 2 is increased at the acceleration rate determined as shown in FIG. The rated frequency recovery is completed. In the above calculation, when the calculated value of fmax becomes equal to or higher than the inverter rated frequency fr, if the restart is performed with fres = fr, the rate acceleration operation performed from t = T3 to t = T4 in FIG. 2 is omitted. Can do.

  The detection of t = T3 may be performed by detecting the output current of the inverter device 2 (not shown), or the time determined by the reconnection computing unit 8 may be detected by a timer.

  FIG. 3 is an operation explanatory diagram of the motor drive device according to the second embodiment of the present invention. In the second embodiment, the upper limit fmax of the restart frequency obtained by the calculation performed by the reconnection calculator 8 at time t = T2 in the first embodiment is equal to or lower than the frequency fm of the motor group having the highest rotational speed. An example of the reconnection method is shown.

  As shown in FIG. 3, when the calculation result performed by the reconnection calculator 8 when the abnormal signal is canceled at time t = T2 is as described above, the inverter device 2 rotates only the motor group 43 having the lowest rotation frequency. Restart at a frequency or slightly higher. In FIG. 1, the branch switch 33 is turned on. The vehicle is accelerated at a predetermined acceleration rate until t = T21. During this time, the reconnection calculator 8 performs the calculation described in the first embodiment at a predetermined sampling period. That is, the upper limit fmax of the restart frequency at which all the motor groups can be simultaneously reconnected is obtained, and the upper limit fmax of the restart frequency at the time of reconnection is equal to or higher than the rotation frequency fm of the motor group with the highest rotation speed at that time. Check if it exists. The branch switch 33 is opened again after a predetermined time after the confirmation, and then the branch switches 31, 32, and 33 are simultaneously turned on with the restart frequency fres of the inverter device 2 set to the range of fm <fres <fmax. As a result, all the motor groups reach the restart frequency fres at time t = T3 after the synchronization arrival time has elapsed. Since the subsequent operation is the same as that of the first embodiment, the description thereof is omitted.

  In the second embodiment, the frequency of the motor group in the free run is accelerated before the upper limit fmax of the restart frequency becomes equal to or higher than the frequency fm of the motor group having the highest rotational speed at that time. When the frequency matches the frequency, the motor group in the free run is put into the inverter device 2, the two motor groups are accelerated, and the confirmation operation is performed. The same applies hereinafter.

  FIG. 4 is an operation explanatory diagram of the motor drive device according to the third embodiment of the present invention. In the third embodiment, when the abnormal signal is reset and the reconnection according to the conditions of the first embodiment is not possible, an operation for accelerating the motor group having the lowest rotation frequency at a predetermined acceleration rate is required. However, performing such an operation complicates the operation procedure. The fourth embodiment provides a method for simplifying the operation procedure even if the entire restart time is somewhat longer.

  As shown in FIG. 4, the restart frequency fres at t = T2 is set to be equal to or lower than the rotation frequency fm of the motor group 41. If it does in this way, the electric motor group 41 will be in the deceleration mode after restart, and regenerative electric power is supplied to the inverter apparatus 2. FIG. Accordingly, the restart frequency fres needs to be equal to or higher than the rotation frequency of the motor group 42. That is, when the inverter device 2 does not have regenerative capability, it is necessary to maintain a power running state as a whole at the time of restart. Therefore, in the third embodiment, the range where the power running state is maintained at the time t = T2 and the minimum frequency that is equal to or higher than the maximum frequency fmax that satisfies the overload condition described in the first embodiment is reconnected. The calculation is performed by the calculator 8 and the restart frequency fres is set within this range to restart. When all the motor groups are in a steady state at time t = T22, the operation is returned to the rated frequency operation before the abnormal signal is given by the same method as in the embodiment.

  Although several embodiments have been described above, these embodiments are presented as examples, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, FIG. 1 shows a case where there are three motor groups, but any number of motor groups may be used.

  In addition, when the electric motor group is turned on at the restart frequency fres in the first to third embodiments, in order to avoid disturbance at the time of turning on, it may be turned on with a little time difference between the groups without simultaneous turning on. .

  In the first to third embodiments, it has been described that all motor groups are accelerated at a predetermined acceleration rate after being synchronously operated. However, when the restart frequency fres is sufficiently lower than the upper limit fmax of the restart frequency. The rate acceleration may be performed before all the motor groups are operated synchronously.

  Further, even if a spare inverter device is separately provided in the system and the inverter device 2 shown in FIG. 1 fails and is reconnected by this spare inverter, the spare inverter device is used in the first embodiment. Obviously, it is possible to perform one to three restart operations.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Inverter apparatus 31, 32, 33 Branch switch 41, 42, 43 Electric motor group 511, ..., 51N, 521, ..., 52N, 531, ..., 53N AC electric motor 611, ..., 61N, 621 ,... 62N, 631,..., 63N Individual switch 7 Reconnection controller 8 Reconnection calculator

Claims (5)

An inverter device for driving a plurality of AC motors;
A plurality of branch switches that are provided on the output side of the inverter device and branch and feed the plurality of AC motors to a plurality of motor groups;
A reconnection control means for opening the plurality of branch switches when the inverter device has stopped abnormally, and performing control to drive the AC motor again when the abnormality is recovered;
A frequency detector respectively connected to the output side of the plurality of branch switches;
A reconnection calculating means for calculating a condition for reconnection based on a frequency signal given from the frequency detector, and for giving a calculation result to the reconnection control means;
The reconnection calculating means includes
A drive device for an electric motor, wherein when the abnormality of the inverter device is recovered, an inverter frequency condition at the time of reconnection and an input condition of the branch switch are calculated so that the inverter device is not overloaded. The reconnection calculating means is
Even if the output frequency of the inverter device is set to a first restart frequency that is greater than or equal to the highest frequency detected by the frequency detector and less than or equal to the rated frequency, and the plurality of branch switches are simultaneously turned on, the inverter device When calculating that is not overloaded,
The reconnection control means simultaneously turns on the plurality of branch switches at a first restart frequency, and performs rate acceleration after the plurality of AC motors have reached the restart frequency, thereby controlling the inverter device. 2. The motor drive device according to claim 1, wherein the motor drive device is returned to a rated value. The reconnection calculating means is
When the output frequency of the inverter device is set to a predetermined restart frequency equal to or higher than the highest frequency detected by the frequency detector and the plurality of branch switches are simultaneously turned on, the inverter device becomes overloaded. Is obtained by calculation,
The reconnection control means includes
In the motor group, the restart switch is turned on in accordance with the frequency of the motor group with the lowest rotation speed, the branch switch is turned on, and the rate is accelerated at a predetermined acceleration rate.
The reconnection calculation means sets the output frequency of the inverter device to a second restart frequency that is greater than or equal to the highest frequency detected by the frequency detector and less than or equal to the rated frequency, and simultaneously turns on the plurality of branch switches. Even when calculating that the inverter device is not overloaded,
The reconnection control means simultaneously turns on the plurality of branch switches at a second restart frequency, and performs rate acceleration after the plurality of AC motors have reached the restart frequency. 2. The motor drive device according to claim 1, wherein the motor drive device is returned to a rated value. The reconnection calculating means is
The output frequency of the inverter device is set to a third restart frequency that is less than or equal to the highest frequency detected by the frequency detector and the inverter device does not perform regenerative operation, and the plurality of branch switches are simultaneously turned on. However, when calculating that the inverter device is not overloaded,
The reconnection control means simultaneously turns on the plurality of branch switches at a third restart frequency, and performs rate acceleration after the plurality of AC motors have reached the restart frequency. 2. The motor drive device according to claim 1, wherein the motor drive device is returned to a rated value. The reconnection calculating means includes
The overload capability characteristic of the inverter device is set and stored as an effective current with respect to the overload duration, and the effective value of the inverter output current obtained by the calculation in the synchronous arrival time at the restart with a predetermined restart frequency is the above effective The motor drive device according to any one of claims 1 to 4, wherein whether or not restarting is possible is determined based on whether or not the current is within the current range.

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