JP7048419B2 - Inverter device - Google Patents

Description

Embodiments of the present invention relate to an inverter device.

Generally, in sensorless vector control executed in an inverter device, the torque is relatively high in the region where the drive frequency is close to zero, in the vicinity of a straight line where the drive frequency = 0 Hz, as shown in FIG. 8 and, for example, FIG. 2 of Patent Document 1. In the high region, the state of the motor becomes unobservable in principle, and the control state may not be maintained. Then, in the inverter device, when the operating point of the motor control falls into an unsustainable region where the sensorless vector control cannot be maintained, or when a sign of the fall is detected, the motor drive is cut off.

For example, in an inverter device applied to the lateral traveling drive of a crane, when the suspended load is suspended and laterally traveled, a force is applied to pull the suspended load back in the traveling direction, as shown in FIG. It may be started in the state of being in the state.

Japanese Unexamined Patent Publication No. 2003-11148 Japanese Unexamined Patent Publication No. 2015-151211

At this time, if the starting torque constrained by the outputable torque or the load current of the inverter device is insufficient than the force to be pulled back, a situation is assumed in which the force is dragged in the acting direction. When the above-mentioned inverter device that performs the protection operation is applied, in such a situation, the operating point of the motor control will detect a sign that the operating point has fallen into an unsustainable area or will fall, and the protection operation will be performed to stop the drive of the motor. Will be done. Therefore, it takes a long time to start the motor.
Therefore, we provide an inverter device that can start the motor without interrupting the drive by protection even in a state where an external force in the direction opposite to the direction in which the motor is driven is acting.

The inverter device of the embodiment includes an inverter circuit for driving a motor and an inverter circuit.
A control unit that controls the motor in a sensorless vector via this inverter circuit,
A drive condition determination unit that determines whether or not the operating point of the motor, which is determined according to the drive condition, has reached an unsustainable region where the sensorless vector control may not be maintained.
When the drive condition determination unit determines that the operating point has reached the unsustainable region, the control unit stops the control of the motor and executes a restart process for restarting the motor after a certain period of time has elapsed. It is provided with a restart processing unit to be operated.

It is an embodiment, and is a flowchart showing mainly the processing by the operability judgment unit. Flow chart showing the "operability judgment" subroutine A flowchart showing an operating point determination process executed by the control unsustainable determination unit. Time chart showing the operation of the inverter device Time chart showing operation by conventional inverter device Functional block diagram showing the configuration of the inverter device with the main parts The figure which shows the state which moves the suspended load suspended from the tip of the rope suspended from a crane trolley. Figure showing uncontrollable region of sensorless vector control

Hereinafter, one embodiment will be described with reference to the drawings. FIG. 6 is a functional block diagram showing the configuration of the inverter device with the main parts. The inverter device 1 includes an inverter circuit 2 and an inverter control unit 3. The inverter circuit 2 has a well-known configuration in which six switching elements are connected by a three-phase bridge, and the AC power supplied from the three-phase AC power supply 4 is converted into DC power by an internal rectifying circuit, and the DC power thereof. Is converted to alternating current by switching and output to the motor 5.

The inverter control unit 3 includes a vector control unit 6, an operability determination unit 7, a control unsustainable determination unit 8, a brake control unit 9, a memory unit 10, a parameter setting unit 11, and the like. An operation command and a frequency command are input to the inverter control unit 3 from a higher-level control device (not shown). When the operation command is input, the operability determination unit 7 determines whether or not the operation is possible according to the state of the drive system at that time, and outputs the determination result to the control unsustainable determination unit 8 and the brake control unit 9. .. The brake control unit 9 controls the opening and closing of the mechanical brake 12 and restrains the motor 5 as necessary. The operability determination unit 7 corresponds to a restart processing unit.

The vector control unit 6 performs sensorless vector control based on the DC voltage Vdc of the drive power supply detected in the inverter circuit 2 and the phase currents Iu and Iv energized in the motor 5, and estimates the speed of the motor 5. Then, the vector control unit 6 generates the three-phase PWM signals Vu, Vv, Vw and outputs them to the inverter circuit 2.

The control unsustainable determination unit 8 determines whether or not the sensorless vector control is in an unsustainable state based on the control information given by the vector control unit 6, and determines the determination result in the vector control unit 6 and the operability determination unit. Output to 7. Further, the control unsustainable determination unit 8 reads the data necessary for the above determination from the memory unit 10 and uses it. The control unsustainable determination unit 8 corresponds to a drive condition determination unit. The parameter setting unit 11 is an interface for the user to input and set the control parameters of the inverter device 1. The function of each functional block in the inverter control unit 3 is realized by software or hardware, or by collaboration between software and hardware.

Here, as shown in FIG. 7, for example, the motor 5 is applied to a crane system that laterally moves a suspended load 15 suspended from the tip of a rope suspended from a crane trolley 13, and travels on the crane trolley 13. Gives a driving force to make it. FIG. 7 shows an image of driving a crane carriage 13 in order to move the suspended load 15 in the traveling direction in a situation where the suspended load 15 is swinging in a pendulum state.

When the position of the suspended load 15 in the pendulum state is in the direction opposite to the traveling direction, a force in the direction opposite to the traveling direction is applied to the crane carriage 13. When the crane carriage 13 is to be started in such a state, a force in the reverse direction may be applied more than a force in the traveling direction that can be output by the inverter device 1 depending on the load and position of the suspended load 15. As a result, as shown in FIG. 8, it is assumed that the operating point of the motor 5 falls into a region where the vector control unit 6 cannot maintain the sensorless vector control.

Next, the operation of this embodiment will be described. FIG. 1 is a flowchart showing mainly the processing by the operability determination unit 7. First, the inverter device 1 determines whether or not the protection operation is being executed during the trip (S1), and if it is during the trip (YES), the trip state is continued (S10). At this time, the mechanical brake 12 is maintained in the closed state to restrain the motor 5. On the other hand, if the inverter device 1 is not on a trip (NO), the subroutine of "operability determination" is called (S2).

As a result of the above determination, if the operation is possible (S3; YES), if an operation command is input and there is an operation request (S4; YES), a frequency command for accelerating the motor 5 to reach a predetermined speed is issued. The calculation is performed (S5), the start of the motor 5 is started based on the frequency command, and the motor 5 is set to the operating state (S6).

On the other hand, even when the operation is possible, if the operation command is not input and there is no operation request (S4; NO), the frequency command for decelerating the motor 5 to reach a predetermined speed is calculated (S7). If the stop condition of the motor 5 is not reached (S8; NO), the process proceeds to step S6, and if the stop condition is reached (YES), the operation is stopped and the mechanical brake 12 is closed (at the same time, the mechanical brake 12 is closed). S9). If the operation is not possible in step S3, the process proceeds to (NO) step S9.

FIG. 2 is a flowchart showing the “operability determination” subroutine. The interval timer is a timer used by the operation availability determination unit 7, and first determines whether or not the timer is stopped (S11). If the interval timer is stopped (YES), the operation itself is stopped, or the operating point is not in the control unsustainable region as described later, and the process proceeds to step S12. If the interval timer has started timing (S11; NO) and has timed the preset time T2 (S15; YES), the timer has stopped timing (S16) in step S12. Transition.

In step S12, an operating point determination is performed as to whether or not the current operation or stop state is in a control-unmaintainable region in which the sensorless vector control state cannot be maintained. This determination will be described later. If the operating point is not in the control unsustainable region (NO), the control unsustainable timer used by the operation enablement determination unit 7 is reset (S13), and the status "enabled; operation or continuation possible" is returned (S14).

On the other hand, in step S12, when the operating point is in the control unsustainable region (YES), the control unsustainable timer is incremented (S17). Then, when the control unsustainable timer clocks T1 for a predetermined time (S18; YES), the interval timer starts timing (S19) and returns the status "disabled; cannot be operated or continued" (S20). If the uncontrollable timer has not timed T1 for a certain period of time (S18; NO), the process proceeds to step S14. The length of T1 for a certain period of time may be appropriately set by the user from the parameter setting unit 11.

In step S15, if the interval timer is not timing the time T2 (NO), the timer is incremented and then (S21) the process proceeds to step S20. This interval timer is not limited to the preset time, but the movement of the suspended load 15 when the lateral traveling operation is performed with the suspended load 15 suspended is approximated to the simple vibration of the pendulum, and the following (1) It is also possible to set a half or a quarter of the period T of the simple vibration shown in the equation as a guide.
T = 2π√ (L / g)… (1)
L: Length of rope 14
g: Gravitational acceleration

FIG. 3 is a flowchart showing an operating point determination process executed by the control unsustainable determination unit 8 in step S12. First, unless the inverter device 1 is in operation (S31; NO), the operating point is not in the control unsustainable region, so that the value is “NO” in step S12 (S35). On the other hand, if the inverter device 1 is in operation (S31; YES), it is determined whether or not the value of the load current is larger than the value obtained by multiplying the preset current limit level by the coefficient K less than "1" (S31; YES). S32). The coefficient K is set to, for example, about "0.8" in order to prevent erroneous determination. If the load current value is larger than the above value, the process proceeds to (YES) step S33, and if it is less than the above value, the process proceeds to (NO) step S35.

In step S33, it is determined whether or not the sign of the primary frequency of the motor 5, which is the speed estimated by the sensorless vector control in the vector control unit 6, is different from the sign of the speed command output by the vector control unit 6 as a control result. do. If the two codes are different (YES), the operating point is in the control unsustainable region, and the result is “YES” in step S12 (S34). If the two codes match, the process proceeds to (NO) step S35. The process shown in FIGS. 1 and 2 corresponds to the "restart process".

Here, in the conventional control, if "NO" is determined in step S3 shown in FIG. 1, the process proceeds to step S10 and the inverter device is tripped. The operation in this case will be described with reference to FIG. Before time t0, the force from the suspended load side is applied to the crane carriage, but the motor is restrained by the mechanical brake. When the inverter device is started and the mechanical brake is released at time t0, the acceleration of the crane carriage is determined by the difference between the output torque of the inverter device and the load side torque. If the latter is larger, it starts accelerating in the direction opposite to the traveling direction. If the torque in the direction opposite to the traveling direction of the crane carriage is not reduced due to the action of the pendulum of the suspended load, the operation can be continued by repeating the process from time t0 to time t3 in FIG. 4 again.

Even if acceleration is performed by a speed command after starting, the output torque requirement increases because the actual speed estimated in the sensorless control does not follow. When it is detected that the preset torque τ1 is reached at the time t1, the timer that measures the time that the operating point stays in the control unsustainable region is started. In this state, at the time t2 when the continuation of the preset time T1 is detected, the inverter device issues a trip, stops the operation, and closes the mechanical brake.

On the other hand, the operation of this embodiment will be described with reference to the time chart of FIG. The behavior up to time t2 is the same as in FIG. Then, when the uncontrollable timer clocks T1 for a certain period of time and the operation enable / disable determination unit 7 detects the status "disable" at time t2, the operation is stopped even if the operation command requests the inverter device 1 to operate. Then, the mechanical brake 12 is closed. At the same time, the interval timer starts timing, and the status becomes "enabled" at time t3 after the time T2 has elapsed. As a result, the inverter device 1 restarts and the mechanical brake 12 is released. At this time, since it is expected that the torque in the direction opposite to the traveling direction of the crane carriage 13 is reduced due to the action of the pendulum of the suspended load 15, the operation can be continued.

As described above, according to the present embodiment, the vector control unit 6 controls the motor 5 in a sensorless vector via the inverter circuit 2. The control unsustainable determination unit 8 determines whether or not the operating point of the motor 5, which is determined according to the drive conditions, has reached an unsustainable region where the sensorless vector control may not be maintained. When the control unsustainable determination unit 8 determines that the operating point of the motor 5 has reached the unsustainable region, the operability determination unit 7 stops the control of the motor 5 by the vector control unit 6, and after a certain period of time elapses, the motor The restart process for restarting 5 is executed.

With this configuration, the suspended load 15 suspended from the rope 14 vibrates like a pendulum, so even if the operating point of the motor 5 reaches an unsustainable region, the inverter device immediately as in the conventional case. Since the restart process is performed without tripping, the crane carriage 13 can be started and the suspended load 15 can be efficiently transferred.

Further, the operation availability determination unit 7 repeatedly executes the restart process until the control unsustainable determination unit 8 determines that the operating point has escaped from the unsustainable region. Therefore, the crane carriage 13 can be reliably restarted. The phrase "determining that the operating point has escaped from the unsustainable region" here means that the state is resolved after the determination is "YES" in step S12 shown in FIG. 2 and the step S17 is reached. S12 determines "NO" to reach step S13, that is, step S33 shown in FIG. 3 determines "YES" to reach step S34, and then step S33 determines "NO" to reach step S35. Means to reach.

Further, in the control unsustainable determination unit 8, the current energized in the motor 5 exceeds the current value less than the preset current limit level, and the code of the motor primary frequency estimated in the sensorless vector control is It is determined that a state different from the sign in the driving direction has reached the unsustainable region when T1 or more is observed for a predetermined period of time. As a result, it can be reliably determined that the suspended load 15 has reached the unsustainable region due to the vibration.
Then, since the user can set the length of T1 for a certain period by the parameter setting unit 11, the optimum time can be set according to the applied system.

(Other embodiments)
The inverter device is not limited to the one that runs the crane carriage 13.
A configuration in which the length of T1 can be set by the user for a certain period by the parameter setting unit 11 may be adopted as necessary.
The restart process may be performed only once.

Although some embodiments of the present invention have been described, 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 embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

In the drawing, 1 is an inverter device, 2 is an inverter circuit, 2 is an inverter control unit, 6 is a vector control unit, 7 is an operability determination unit, 8 is a control unsustainable determination unit, and 11 is a parameter setting unit.

Claims (4)

The inverter circuit that drives the motor and
A control unit that controls the motor in a sensorless vector via this inverter circuit,
A drive condition determination unit that determines whether or not the operating point of the motor, which is determined according to the drive condition, has reached an unsustainable region where the sensorless vector control may not be maintained.
When the drive condition determination unit determines that the operating point has reached the unsustainable region, the control unit stops the control of the motor and executes a restart process for restarting the motor after a certain period of time has elapsed. Inverter device with a restart processing unit to make it. The inverter device according to claim 1, wherein the restart processing unit repeatedly executes the restart processing until the drive condition determination unit determines that the operating point has escaped from the unsustainable region. In the drive condition determination unit, the current energized in the motor exceeds a current value less than a preset current limit level, and the speed or primary frequency of the motor estimated by the sensorless vector control is reached. The inverter device according to claim 1 or 2, wherein it is determined that the unsustainable region is reached when a state in which the code is different from the code in the driving direction is observed for a predetermined period or longer. The inverter device according to any one of claims 1 to 3, further comprising a setting unit for setting the length of the fixed period by the user.

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