JP2008061477A - Inverter device and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter device and its control method to monitor a primary frequency at a maximum current and output it to a monitor. <P>SOLUTION: This inverter device is provided with a coordinate conversion portion (12a), a voltage limit value calculation portion (15), a frequency command calculation portion (1), a voltage command correction portion (23) that generates a dq-axis corrected voltage command from a primary frequency command calculation portion, a dq-axis voltage limit command calculation portion, and a dq-axis voltage limit command, a PWM command calculation portion (9) that generates a PWM command from the dq-axis corrected voltage command and a reference phase, and a power conversion portion (10) that converts the PWM command into power. In this inverter device, the frequency command calculation portion (1) comprises a current limit acceleration correction portion (11a) that corrects the acceleration of the frequency command from the voltage limit value and a primary current phase. There are further provided, a current alarm generation portion (18), which generates a current alarm from a difference value between primary current amplitude and the current limit value, and a current alarm display portion (19), which display the current alarm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inverter device in which suppression of overcurrent when an induction motor or the like is driven by V / f control and a control method thereof.

The conventional inverter device gives a command to the control circuit from the level setter that limits the current using the output frequency command based on the information from the current detection means, and the voltage frequency ratio and acceleration / deceleration time are incorrectly adjusted However, the current is limited before the energization current reaches the overcurrent protection level, and the operation is continued without stopping the device (Patent Document 1). Also, overcurrent control is performed using a memory that stores an angular velocity-current limit value table in which the relationship between the angular velocity calculated according to the thermal time constant of the junction of the semiconductor switching element and the allowable junction temperature is tabulated. There are some (Patent Document 2).
Furthermore, in order to prevent destruction of the semiconductor switching element power cycle due to overcurrent, the protection information of the semiconductor switching element is output based on a signal from a resistor or a circuit that changes depending on the temperature in the immediate vicinity of the semiconductor switching element. There is also (patent document 3). FIG. 3 is for performing the optimum current limitation at the time of V / f control.
As described above, the overcurrent limitation of the conventional inverter device prevents the semiconductor switching element from being damaged by the power cycle, warns of the abnormality of the semiconductor element, and does not stop the operation of the inverter device.
Japanese Utility Model Publication No. 6-70498 Japanese Patent Laid-Open No. 9-14187 JP 2000-341960 A

Since the conventional inverter device disclosed in Patent Document 1 only performs current limitation according to the output frequency according to the state of the current limitation level, the optimum output voltage is not adjusted, and at that time Since the state of the current value and the output frequency is unknown, there is a problem that the operator and the adjuster cannot perform appropriate measures for the inverter device. In particular, there is also a problem that the state cannot be directly monitored if the inverter device such as a crane and the operator and the adjuster are located away from each other.
In addition, the inverter device disclosed in Patent Document 2 adjusts the current value and output frequency based on the junction of the semiconductor element and the temperature allowable value, and the current adjustment of the d-axis and q-axis of the motor using a magnetic flux converter. However, as described above, there is a problem that the state cannot be directly monitored if the inverter device and the operator and the adjuster are located at a distance. Since the inverter device disclosed in Patent Document 3 is temperature monitoring and warning output only for semiconductor elements, it cannot perform processing such as overcurrent limiting.
The present invention has been made in view of such problems, and an object of the present invention is to provide an inverter device capable of monitoring and outputting the primary frequency at the maximum current and a control method thereof.

In order to solve the above problem, the present invention is configured as follows.
The invention according to claim 1 generates a voltage limit value from the primary current amplitude and the overcurrent limit value, and a coordinate converter that converts the primary current and the reference phase into the primary current amplitude and the primary current phase. A voltage limit value calculation unit, a frequency command calculation unit that calculates a first frequency command from the primary current phase, the voltage limit value, and a frequency command, and a primary frequency command from the first frequency command and a slip frequency are generated. A primary frequency command calculation unit, a dq axis voltage limit command calculation unit that generates a dq axis voltage limit command from the voltage limit value and the primary current phase, and generates the reference phase by integrating the primary frequency command. A dq axis correction voltage command from the q axis voltage command, the d axis voltage command, and the dq axis voltage limit command. A voltage command correction unit that performs the d In the inverter device including a PWM command calculation unit that generates a PWM command from the axis correction voltage command and the reference phase, and a power conversion unit that converts the PWM command into power, the frequency command calculation unit includes the voltage limit value and the 1 A current limiting acceleration correction unit that corrects the acceleration of the frequency command based on the next current phase is provided.
A second aspect of the present invention is the inverter apparatus according to the first aspect, wherein the d-axis voltage command is a zero voltage.
According to a third aspect of the present invention, in the inverter device according to the first aspect, a current warning generation unit that generates a current warning from a difference value between the primary current amplitude and the current limit value, and the current warning are displayed. And a current warning display unit.
According to a fourth aspect of the invention, there is provided the inverter device according to the first aspect, further comprising a maximum value display unit for displaying the maximum value of the primary current amplitude and the primary frequency command at that time. It is.
According to a fifth aspect of the invention, there is provided the inverter device according to the third aspect, further comprising a storage unit that stores the maximum primary current value and a comparison unit that compares the maximum primary current value and a primary current amplitude. It is characterized by this.
The invention according to claim 6 outputs a voltage by PWM modulation based on a frequency command and a voltage command obtained by f / V conversion from the frequency command, and performs a protection operation when an overcurrent is detected. In a control method of an inverter device to be performed, a step of converting a primary current and a reference phase into a primary current amplitude and a primary current phase, and when the primary current amplitude exceeds a predetermined current limit value, are proportional to the excess Obtaining a voltage limit value; converting the voltage limit value into voltage limit values ΔVq and ΔVd based on the primary current phase; and adding the voltage limit value to the voltage command to generate a corrected voltage command Instantaneously limiting the current; correcting the frequency acceleration command based on the voltage limit value and the primary current phase; and limiting the current; and the primary current amplitude exceeds the current limit value. A step of giving an overcurrent warning as an abnormal current value based on the obtained current value.
According to a seventh aspect of the present invention, in the control method for an inverter device according to the sixth aspect, when the primary current amplitude exceeds the primary current amplitude maximum value, a new primary current amplitude maximum value is set. Storing the frequency command, and displaying the primary current amplitude maximum value and the frequency command and outputting an analog signal to the outside.

As described above, according to the present invention, the voltage limit vector of the component on the voltage command axis in the reverse direction or the reverse direction of the current vector is added in proportion to the amount exceeding the current limit value with respect to the voltage command. As a result, the current can be instantaneously limited, and further, by providing a current limiting method of three levels, it is possible to reliably prevent the destruction of the element and the stall due to the current. In addition, by correcting the acceleration from the voltage limit value and the current phase, the current is constantly limited, and the induction motor or the like can be operated efficiently.
In addition, by displaying warning alarms for overcurrent conditions, it is possible to confirm power cycle semiconductor element destruction due to overcurrent during low-frequency operation of the inverter device, and to check the maximum current value and the output frequency at that time. Even if the operator and the adjuster are away from the inverter device, it can be easily confirmed and adjusted.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 1, 1 is a frequency command calculation unit, 22 is a voltage limiting unit, 23 is a voltage command correction unit, and 10 is a power conversion unit. 2 is an acceleration command calculation unit, 3 is an integrator, 4 is a command value limiting unit, 5 is a slip frequency calculation unit, 7 is an f / V converter, 8 is a reference phase calculation unit, 9 is a PWM command calculation unit, 10 is a power conversion unit, 11a is a current limit acceleration correction unit, 11a 'is a frequency command switching unit, 12a is a coordinate conversion unit, 13 is a current comparison unit, 14 is a limit unit, 15 is a voltage limit calculation unit, and 16 is a dq axis. , 17a is a q-axis voltage command correction unit, 17b is a d-axis voltage command correction unit, 18 is a current warning generation unit, and 19 is a current warning display unit.

Next, the operation will be described. The frequency command calculation unit 1 generates a first frequency command from the frequency command, and the primary frequency command calculation unit 24 adds the first frequency command and the slip frequency to generate a primary frequency command. The f / V conversion unit 7 converts the primary frequency to f / V and generates a q-axis voltage command. The PWM command calculation unit 9 converts the q-axis voltage command and the d-axis voltage command with a reference phase θ obtained by integrating the primary frequency command to generate a three-phase voltage command, further converts it into a PWM signal, and converts it into a PWM signal. 10 is driven. Next, the primary current amplitude and the current phase θi with respect to the reference phase θ are obtained by the coordinate conversion unit 12a, and the primary current amplitude I1 is subtracted from the current limit value Imax set by the current comparison unit 13. The limit unit 14 sets 0 when the subtraction result is negative, and limits it to a predetermined value when the subtraction result is greater than or equal to the predetermined value. The voltage limit calculation unit 15 performs gain and filter processing (K / 1 + Ts) to obtain a voltage limit value ΔV. The dq-axis voltage limit calculation unit 16 calculates the dq-axis voltage limit values ΔVq and ΔVd from the calculated voltage limit value ΔV and the current phase θi using the formulas (1) and (2).
ΔVq = −ΔVsin θi (1)
ΔVd = −ΔVcos θi (2)
Note that the same result can be obtained even if the current detection values Id and Iq are used to obtain the equations (3) and (4).
ΔVq = −ΔV × Iq / I1 (3)
ΔVd = −ΔV × Id / I1 (4)
Next, the calculated ΔVq and ΔVd are added to the voltage commands Vq * and Vd * by the adders 17a and 17b to obtain the dq-axis corrected voltage commands Vq and Vd, and the PWM command calculator 9 calculates the three-phase (UVW phase) voltage. A command is obtained, converted into a PWM pattern, output to the power conversion unit 10, and a voltage is applied to the motor IM. This makes it possible to limit the current instantaneously. The relationship between the voltage limit vector ΔV, the voltage command vector V *, and the current vector I during this time is obtained by adding the voltage limit vector ΔV in the reverse direction to the current to the voltage command V * on the q axis in the regenerative state, and applying the applied voltage A state in which the current vector I is limited by decreasing V is shown. Conversely, ΔV is added in the same direction to increase the applied voltage V to limit the current vector I, and the current can be instantaneously limited regardless of the state of the motor. When ΔI of the current warning generator 18 becomes 0, an overcurrent warning is displayed on the 19 current warning indicators. In the case of an instant, the display is lit for 3 seconds so that anyone can confirm, so the state can be confirmed without fail.

  In FIG. 2, 11a is a current limiting acceleration correcting unit for correcting acceleration, 11a 'is a frequency command switching unit for switching between a frequency command and a current limiting output frequency, and 12a outputs a primary current amplitude I1 and a primary current phase θ1. The coordinate conversion unit 13 is a current comparison unit that compares the primary current amplitude I1 and the overcurrent limit value Imax, and its output is ΔI. 14 is a limit unit that outputs a comparison result, 15 is a voltage limit calculation unit that calculates a voltage limit value ΔV, 16 is a dq axis voltage limit calculation unit that calculates dq axis voltage limit values ΔVq and ΔVd, and 17a and b are voltage command corrections. The voltage command and the dq axis voltage limit value are added at the unit, 18 is a current warning generation unit that compares ΔI for overcurrent warning, 19 is the current warning display unit at the time of current warning, and the maximum value of the primary current amplitude I1 Compare and hold the output frequency 6 at the maximum value.

  In FIG. 2, the maximum value I1 is always monitored by the 20 maximum value comparing means, the 6 output frequencies at the maximum value are stored, and the value can be displayed on the maximum value display unit 21, so the overcurrent state can be displayed. Power cycle semiconductor element destruction due to overcurrent during low-frequency operation of the inverter device can be confirmed while monitoring, and the maximum current value and the output frequency at that time can be confirmed. You can easily check and adjust even if you are away.

FIG. 4 is a flowchart showing a method for controlling the inverter device of the present invention. In FIG. 4, the primary current amplitude and the primary current phase are detected in step ST1, and in step ST2, a voltage limit value proportional to the excess is obtained when the primary current amplitude exceeds a predetermined current limit value. In step ST4, the voltage limit value is converted into voltage limit values ΔVq and ΔVd based on the primary current phase, the voltage limit value is added to the voltage command in step ST4 to generate a corrected voltage command, and the current is instantaneously limited. The current acceleration is corrected by correcting the frequency acceleration command based on the voltage limit value and the primary current phase, and the current value abnormality is determined based on the current value ΔI in which the primary current amplitude exceeds the current limit value in step ST6. Perform overcurrent warning.

The control block diagram of the inverter apparatus which shows 1st Example of this invention Control block diagram of inverter device showing second embodiment of the present invention Control block diagram of conventional inverter device The flowchart which shows the control method of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frequency command calculating part 2 Acceleration command calculating part 3 Acceleration frequency integrating part 4 Command value limiting means part 5 Slip frequency deducing part 6 Output frequency 7 f / V converting part 8 Phase calculating part 9 PWM command calculating part 10 Power converting part 11a Current Limit acceleration correction unit 11a ′ Frequency command switching unit 12a Coordinate conversion unit 13 Current comparison unit 14 Limit circuit 15 Voltage limit value calculation unit 16 Voltage limit vector calculation unit 17a q-axis voltage command correction unit 17b d-axis voltage command correction unit 18 Current warning Generating unit 19 Current warning indicator 20 Maximum value comparing unit 21 Maximum value displaying unit 22 Voltage limiting unit 23 Voltage command correcting unit 24 Primary frequency command calculating unit

Claims (7)

A coordinate conversion unit that converts the primary current and the reference phase into a primary current amplitude and a primary current phase; a voltage limit value calculation unit that generates a voltage limit value from the primary current amplitude and an overcurrent limit value; A frequency command calculation unit that calculates a first frequency command from a secondary current phase, the voltage limit value, and a frequency command; a primary frequency command calculation unit that generates a primary frequency command from the first frequency command and a slip frequency; A dq-axis voltage limit command calculation unit that generates a dq-axis voltage limit command from the voltage limit value and the primary current phase; an integrator that integrates the primary frequency command to generate the reference phase; and the primary frequency An f / V converter that generates a q-axis voltage command from the command, a voltage command correction unit that generates a dq-axis correction voltage command from the q-axis voltage command, the d-axis voltage command, and the dq-axis voltage limit command, and the dq Axis correction voltage command and reference A PWM command computing section for generating a PWM command from the phase, the inverter device and a power converter for power conversion of the PWM command,
The inverter apparatus, wherein the frequency command calculation unit includes a current limit acceleration correction unit that corrects a first frequency command based on the voltage limit value and the primary current phase.   The inverter device according to claim 1, wherein the d-axis voltage command is a zero voltage.   The current warning generation unit that generates a current warning from a difference value between the primary current amplitude and the current limit value, and a current warning display unit that displays the current warning are provided. Inverter device.   2. The inverter device according to claim 1, further comprising a maximum value display unit that displays a maximum value of the primary current amplitude and a primary frequency command at that time.   The inverter device according to claim 4, further comprising: a storage unit that stores the maximum primary current value; and a comparison unit that compares the primary current maximum value with a primary current amplitude. In a control method for an inverter device that generates a voltage by PWM modulation based on a frequency command and a voltage command obtained by f / V conversion from the frequency command, and performs a protective operation when an overcurrent is detected,
Converting a primary current and a reference phase into a primary current amplitude and a primary current phase;
Obtaining a voltage limit value proportional to the excess when the primary current amplitude exceeds a predetermined current limit value;
Converting the voltage limit value to dq axis voltage limit values ΔVq and ΔVd based on the primary current phase;
Adding the dq axis voltage limit value to the voltage command value to generate a corrected voltage command and instantaneously limiting the current;
Correcting the frequency acceleration command based on the voltage limit value and the primary current phase to limit the current;
Performing an overcurrent warning as a current value abnormality based on a current value at which the primary current amplitude exceeds the current limit value;
An inverter device control method comprising: When the primary current amplitude exceeds the primary current amplitude maximum value, a new primary current amplitude maximum value is set, and a frequency command at that time is stored;
Displaying the primary current amplitude maximum value and the frequency command and outputting an analog signal to the outside;
The method for controlling an inverter device according to claim 6, further comprising:

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