KR20080016373A - Apparatus and method thereof for suppressing inertia load - Google Patents

Abstract

An apparatus and a method for suppressing inertial load of an inverter system are provided to suppress an excessive current in an excessive current condition caused by large inertia load. In an inverter system for driving an induction motor, an acceleration/deceleration control part(13) outputs a deceleration/acceleration control signal accelerating/decelerating the induction motor according to input conditions. A df calculation part(12) calculates variation of frequency per hour according to the acceleration/deceleration control signal, and outputs the calculated frequency variation according to the acceleration/deceleration control signal. A first adder(17) generates an output frequency of the inverter system by adding the calculated frequency variation to an input frequency. A V/f pattern generation part(14) generates voltage reference value in proportion to the amplitude of the output frequency. An excessive current trip suppressing part(50) generates the variation of a control voltage to suppress excessive current trip of the inverter system according to the acceleration/deceleration control signal. A second adder(56) generates a corrected voltage reference value by adding the control voltage variation to the voltage reference value.

Description

Inertial load suppression device of inverter system and its method {APPARATUS AND METHOD THEREOF FOR SUPPRESSING INERTIA LOAD}

1 is a block diagram of an inverter control system for driving a conventional flow motor.

2 is a diagram illustrating a relationship between a voltage command value and an output frequency according to the prior art.

3 is a detailed configuration diagram of the operation command and the controller of FIG. 1.

Figure 4 (a) is a relationship between the current frequency and the output frequency according to an embodiment of the present invention, Figure 4 (b) is a speed change diagram for each time when the inverter is normal acceleration.

5 is a configuration diagram of a specific operation command and the control unit of the inertial load suppression apparatus of the inverter system according to an embodiment of the present invention.

6 is a control flowchart of an inertial load suppression method of an inverter system according to an exemplary embodiment of the present invention.

7 is an output voltage control diagram illustrating a control region of an output voltage according to an exemplary embodiment of the present invention.

The present invention relates to an inertial load overcurrent suppression apparatus and method thereof of the inverter system, and more particularly, a device for suppressing an overcurrent trip of an inverter when a general-purpose inverter system that is a speed control device of an induction motor drives an acceleration / deceleration or constant speed of an electric motor. And to a method thereof.

1 is a general system configuration diagram of a control device for driving a conventional induction motor, and is composed of an AC power source 1, a general-purpose inverter system 20, and an induction motor 5. In particular, as shown in FIG. 1, the conventional inverter system 20 according to the related art includes a converter 2, a smoothing capacitor 3, an inverter 4, an operation command and a controller 6, and a coordinate converter 7. And a pulse width-modulated (PWM) signal generator 8, an integrator 9, a current detector 10 and a voltage detector 11.

Referring to the operation of the general-purpose inverter system 20, the converter 2 receives an AC voltage from the AC power source 1 and converts it into a DC voltage, and the smoothing capacitor 3 is input from the converter 2. Smooth the DC voltage received. The inverter 4 is composed of a switching control element such as an IGBT, a GTO, etc., in order to operate the induction motor 5, in accordance with a pulse width-modulation (PWM) signal, the received smoothing voltage is alternating current having an appropriate frequency. Convert it to voltage and output it.

At this time, the frequency of the AC voltage output to drive the induction motor may be changed as necessary.

The inverter 4 is controlled by a pulse width modulated signal, and this pulse width modulated signal is generated through the following specific process.

First, the voltage detector 11 detects a DC link voltage that is a voltage across the smoothing capacitor. The operation command and the control unit 6 are spaces that are voltage command values based on the DC link voltage detected by the voltage detector 11 and the coordinate-converted spatial coordinate currents idse and iqse converted by the coordinate conversion unit 7. Coordinate voltages VdseRef, VqseRef and the switching frequency fo of the switching elements constituting the inverter are output. The coordinate converting unit 7 converts the detected three-phase coordinate currents ias ', ibs' into the spatial coordinate currents idse and iqse, and the voltage command value spatial coordinate voltages VdseRef and VqseRef into three-phase coordinate voltages Vas *, Vbs * and Vcs *. Convert the coordinates to.

In addition, the pulse width-modulated (PWM) signal generation unit 8 generates a pulse width-modulated (PWM) signal by comparing the reference voltage for each phase and a triangular wave to generate a gate terminal of the switching element of each phase of the inverter 4. A switching voltage is applied to the integrator 9, and the integrator 9 converts the switching frequency fo into a phase value, and the current detector 10 detects the output current ias and ibs of the inverter 4. do.

A general-purpose inverter (hereinafter referred to as an inverter) system for driving an induction motor configured as described above uses voltage / frequency (V / F, Voltage / Frequency) control and is widely used in the field of speed control of an induction motor. The V / F control method used in the inverter system is a method of controlling the average torque by proportionally controlling the stator voltage effective value and the frequency of the induction motor.

The V / F control method keeps the magnitude of the rotor flux constant and close to the rated torque value of the induction motor even if the speed and torque of the induction motor change. This means that the V / F control method controls the induction motor by constant flux operation.

2 shows the ratio of the inverter output voltage and the output frequency for the constant flux operation.

In the case where the motor is accelerated or decelerated by an inverter, the speed of the induction motor is generally controlled according to a value obtained by adding and subtracting the acceleration / deceleration time-varying amount per unit time. The induction motor using the acceleration / deceleration control method as described above is used. Accelerates and decelerates while maintaining average torque.

However, in the acceleration / deceleration process of maintaining the above-described average torque, in the case of acceleration or deceleration or start of a short time, the required current of the load increases so that an overcurrent trip occurs.

3 shows a detailed configuration of the operation command and the control unit 6, wherein the operation command and the control unit 6 includes a df calculation unit 12 that calculates a frequency variation per unit time, and deciding whether to perform deceleration or not. The speed control part 13 and the V / f pattern generation part 14 which make the voltage command value Vi which has a proportional relationship with the drive frequency fo of the induction motor.

Referring to the operation according to the operation command and the specific configuration of the control unit 6, when the inverter needs to accelerate and decelerate, the frequency command value is calculated by calculating the speed variation amount (df) per unit time and subtracting the value for each unit time. If (fo) is printed and expressed as an expression, it is as follows.

(가속의 경우),

(감속의 경우) (1)

(For acceleration),

(In case of deceleration) (1)

(2) 이다. here,

(2)

The frequency variation df per hour is calculated by the df calculator 12 based on Equation (2), and becomes a constant value when the acceleration / deceleration time is determined. The acceleration / deceleration command unit 13 determines whether to execute the acceleration / deceleration according to a user's selection or other conditions. When the flow motor is accelerated according to the signal of the inverter, if the current of the current detector 10 is greater than the set rated value, the acceleration / deceleration command unit 13 commands the acceleration stop to converge the frequency variation amount df per hour to zero. do.

During deceleration, if the voltage (DC link voltage) across the smoothing capacitor (3) is greater than the set rated voltage or the current is larger than the set value as in the case of acceleration, the frequency variation amount (df) for each time is converged to zero according to the deceleration stop command. do.

In general, the inverter performs normal acceleration and deceleration, and the speed decreases according to the value substituted into Eq. (1). In addition, as shown in FIG. 2, the V / f pattern generator 14 outputs a voltage command value Vi having a proportional relationship with the frequency command value fo.

FIG. 4 illustrates one method of the deceleration pattern in which the frequency command value fo, which is the output frequency of the inverter, reaches from the current frequency f2 to the target frequency f1. FIG. Fig. 4 (b) shows the change in the speed variation amount df for each time the inverter decelerates normally.

As shown in FIGS. 4 (b) and 2, the induction motor control apparatus according to the related art calculates the speed variation amount df for each time and controls the speed with an output obtained by adding the value for each unit time, and the voltage is frequency. Determined by the relationship with the setpoint (fo).

While the inverter 4 accelerates the motor 5, if the current detected by the current detector 10 is greater than the set rated value, the output frequency df for each time becomes zero by commanding the acceleration stop. . In addition, while the motor 5 rotates at a constant speed, if the current detected by the current detector 10 is greater than a set value, the motor 5 decelerates.

However, when an overcurrent occurs, if the acceleration stop and deceleration operation schemes are applied to a load having a large inertia, the time to return to normal operation from an overcurrent situation becomes long, and even a problem such as being unable to return at all and staying in the stall state occurs. This happens.

The present invention was devised to solve the above problems of the prior art, and an object of the present invention is to provide an overcurrent in an overcurrent situation that may occur when the load inertia is large in a general-purpose inverter system that is a speed control device of an induction motor. The present invention is to implement an overcurrent suppression method for smoothly performing a suppression operation and quickly returning to a normal state.

The overcurrent trip suppression apparatus of the inverter system according to the present invention for achieving the above object is an acceleration system for outputting an acceleration / deceleration control signal for accelerating and decelerating the floating motor according to an input condition in an inverter system for driving an induction motor. Control unit; A df calculation unit calculating a variation amount of frequency per time according to the acceleration / deceleration control signal and outputting the calculated frequency variation amount according to the acceleration / deceleration control signal; A first adder for generating and outputting an output frequency of the inverter system by adding the calculated frequency variation to an input frequency; A V / f pattern generator for generating and outputting a voltage command value proportional to the magnitude of the output frequency; An overcurrent trip suppression unit configured to generate and output a control voltage variation amount for suppressing an overcurrent trip of the inverter system according to the acceleration / deceleration control signal; And a second adder for generating and outputting a corrected voltage command value by adding the control voltage variation amount to the voltage command value.

The overcurrent trip suppression method of the inverter system according to the present invention for achieving the above object, in the control method of the inverter system for driving a floating motor, in order to control the acceleration and deceleration, the acceleration and deceleration control signal according to an input condition Outputting the process; Calculating a change amount of the frequency per time according to the acceleration / deceleration control signal and outputting the calculated frequency change amount according to the acceleration / deceleration control signal; Generating and outputting an output frequency obtained by adding the frequency variation amount to an input frequency; Generating and outputting a voltage command value proportional to the output frequency; An overcurrent trip suppression step of generating and outputting a control voltage variation amount for suppressing an overcurrent trip of the inverter system according to the acceleration / deceleration control signal; And generating a corrected voltage command value by adding the control voltage variation amount to the voltage command value.

In the following, the inverter system, which can smoothly perform the operation by suppressing the trip of the inverter system due to the overcurrent in the overcurrent situation that can occur when the load inertia is large, and also return the inverter system to the normal state quickly. The preferred embodiment of the overcurrent trip suppression apparatus and its method will be described in detail with reference to FIGS.

5 is a circuit diagram showing an embodiment of an overcurrent trip suppression apparatus of an inverter system according to an embodiment of the present invention.

The overcurrent trip suppression apparatus of the inverter system according to the embodiment of the present invention shown in FIG. 5 includes an acceleration / deceleration control signal for accelerating and decelerating the induction motor according to an input condition in an inverter system for driving an induction motor. An acceleration / deceleration control unit 13 for outputting; A df calculation unit 12 calculating a variation amount of frequency per time according to the acceleration / deceleration control signal and outputting the calculated frequency variation amount according to the acceleration / deceleration control signal; A first adder (17) for generating and outputting an output frequency of the inverter system by adding the calculated frequency variation to an input frequency; A V / f pattern generator 14 generating and outputting a voltage command value proportional to the magnitude of the output frequency; An overcurrent trip suppression unit 50 generating and outputting a control voltage variation amount for suppressing an overcurrent trip of the inverter system according to the acceleration / deceleration control signal; And a second adder 56 for generating and outputting a corrected voltage command value by adding the control voltage variation amount to the voltage command value.

The overcurrent trip suppression unit 50 includes a feedback current calculating unit 51 that receives a d-axis current and a q-axis current of the flow motor and calculates a feedback current; A subtractor 52 for detecting an error current between the rated current and the feedback current; A PI controller 53 for calculating a control voltage variation amount based on the detected error current; A limit 54 for limiting an upper and lower limit of the control voltage variation amount; And switching means 55 for interrupting the supply of the control voltage variation amount in order to suppress an overcurrent trip in accordance with the acceleration / deceleration control signal.

Here, the rated current may be preset to a value determined by the specification of the system or may be directly input by the user.

The acceleration / deceleration control unit 13 blocks the output of the df calculator 12 when the feedback current Imag is greater than the rated current Isup, and simultaneously maintains the output of the overcurrent trip suppression unit 50. Outputs the acceleration / deceleration control signal.

The df calculator 12 switches the switching means 15 disposed between the df calculator 12 and the first adder 17 to control the supply of the frequency variation per hour according to the acceleration / deceleration control signal. It may include.

6 is a flowchart illustrating an embodiment of an overcurrent trip suppression method of an inverter system according to an exemplary embodiment of the present invention.

In the overcurrent trip suppression method of the inverter system according to the embodiment of the present invention shown in FIG. 6, in the control method of the inverter system for driving a floating motor, the acceleration and deceleration control is performed according to an input condition. Outputting a speed control signal (S60); Calculating a change amount of the frequency per time according to the acceleration / deceleration control signal and outputting the calculated change amount of frequency according to the acceleration / deceleration control signal (S61); Generating and outputting an output frequency obtained by adding the frequency variation amount to an input frequency (62); Generating and outputting a voltage command value proportional to the output frequency (S63); An overcurrent trip suppression step (S64) of generating and outputting a control voltage variation amount for suppressing an overcurrent trip of the inverter system according to the acceleration / deceleration control signal; And generating a corrected voltage command value by adding the control voltage variation amount to the voltage command value (S65).

The overcurrent trip suppression step (S64) may include calculating a feedback current from d-axis current and q-axis current of the induction motor; Detecting an error current between the calculated feedback current and rated current; A PI control step of calculating and outputting a control voltage variation based on the detected error current; Limiting and outputting a maximum value of the control voltage variation amount; And controlling the supply of the control voltage variation amount to suppress an overcurrent trip of the inverter system according to the acceleration / deceleration control signal.

In the overcurrent trip suppression process S64, when the feedback current Imag is greater than the rated current Isup, the overcurrent trip is suppressed by adding or subtracting the control voltage variation VL to an output voltage.

In the suppression process S64 of the overcurrent trip, if the feedback current Imag is not greater than the rated current Isup, the voltage command value is corrected by using the error accumulation value of the frequency variation amount and the control voltage variation amount to quickly return to a normal state. It is characterized by returning.

Figure 7 shows the control region of the output voltage according to the present invention, the prior art controls the induction motor by making the output voltage greater than the reference output voltage, as shown in Figure 7, the present invention is always the reference value of the output voltage Control the output voltage so that it is in the shaded area below the output. In other words, by controlling the voltage in the negative direction according to the magnitude of the current to suppress the overcurrent to control to maintain the operation of the induction motor.

Brief description of the technical features of the present invention.

The present invention further includes an overcurrent trip suppressing unit indicated by a dotted line in FIG. 5 in order to prevent a trip caused by an overcurrent existing in the inverter control system for a conventional induction motor.

In the present invention, the acceleration / deceleration control unit 13 activates the df calculation unit 15 and deactivates the trip suppression unit 50 when the inverter normally decelerates at the request of the user. Is computed and output in the conventional manner.

However, when the inverter accelerates or constant speeds the induction motor, the induction motor increases in magnitude due to the frictional load, the inertia load, and the slip caused by the set deceleration time. At this time, when the feedback current Imag representing the magnitudes of the d-axis current and the q-axis current fed back from the induction motor with respect to the rated current Isup is increased, the acceleration / deceleration control unit 13 is the df calculation unit 15. By deactivating, the trip suppression unit 50 changes the acceleration / deceleration control signal by activating. In response to the change of the acceleration / deceleration control signal, the output voltage Vi is finally changed to a new output voltage Vi_New, which is a voltage command value corrected by adding a voltage variation amount.

That is, if the magnitude of the load current does not cause a trip, acceleration and deceleration are performed as in the conventional method. If the state of the load changes and a situation may occur, the overcurrent suppression operation of the PI controller to suppress the trip is performed.

As described above, although the embodiments of the present invention have been described in detail with reference to the drawings, the spirit and scope of the present invention should not be construed as being limited to the above embodiments, but are defined by the appended claims. It will be apparent to those skilled in the art that various modifications are possible within the scope of.

As described above in detail, the inertial load suppression apparatus and method of the inverter according to the present invention are applied to the acceleration and deceleration of the induction motor by using the information of the current and voltage of the induction motor, and the inertial load suppression system including the inverter and the motor. The controller's performance including good acceleration, adaptability, and speed ripple reduction can be achieved by implementing an acceleration method that can suppress the overcurrent trip of the inverter system without overloading the motor and simultaneously match the actual speed of the motor to the acceleration time selected by the user. Has the effect of improving.

Claims (8)

In the inverter system for driving an induction motor, An acceleration / deceleration control unit outputting an acceleration / deceleration control signal for accelerating and decelerating the flow motor according to an input condition; A df calculation unit calculating a variation amount of frequency per time according to the acceleration / deceleration control signal, and outputting the calculated variation amount of frequency according to the acceleration / deceleration control signal; A first adder for generating and outputting an output frequency of the inverter system by adding the calculated frequency variation to an input frequency; A V / f pattern generator for generating and outputting a voltage command value proportional to the magnitude of the output frequency; An overcurrent trip suppression unit configured to generate and output a control voltage variation amount for suppressing an overcurrent trip of the inverter system according to the acceleration / deceleration control signal; And A second adder for generating and outputting a corrected voltage command value by adding the control voltage variation amount to the voltage command value; Inertial load suppression apparatus of the inverter system comprising a. The method of claim 1, wherein the overcurrent trip suppression unit A feedback current calculating unit configured to calculate a feedback current by receiving the d-axis current and the q-axis current of the flow motor; A subtractor for detecting an error current between the rated current and the feedback current; A PI controller configured to calculate a control voltage variation based on the detected error current; A limit for limiting an upper and lower limit of the control voltage variation amount; And Switching means for interrupting the supply of the control voltage variation amount in order to suppress an overcurrent trip in accordance with the acceleration / deceleration control signal; Inertial load suppression apparatus of the inverter system comprising a. According to claim 1, wherein the acceleration and deceleration control unit And the feedback current is greater than the rated current, and outputs the acceleration and deceleration control signal for maintaining the output of the overcurrent trip suppression unit and simultaneously outputting the df calculator. The method of claim 1, wherein the df calculation unit And switching means for controlling the supply of the frequency variation per hour in accordance with the acceleration / deceleration control signal. In the control method of the inverter system for driving a flow motor, Outputting an acceleration / deceleration control signal according to an input condition to control the acceleration / deceleration of the motor; Calculating a change amount of the frequency per time according to the acceleration / deceleration control signal and outputting the calculated frequency change amount according to the acceleration / deceleration control signal; Generating and outputting an output frequency obtained by adding the frequency variation amount to an input frequency; Generating and outputting a voltage command value proportional to the output frequency; An overcurrent trip suppression step of generating and outputting a control voltage variation amount for suppressing an overcurrent trip of the inverter system according to the acceleration / deceleration control signal; And And controlling the voltage command value by adding the control voltage fluctuation amount to the voltage command value. The method of claim 5, wherein the suppression of the overcurrent trip is performed. Calculating a feedback current from d-axis current and q-axis current of the induction motor; Detecting an error current between the calculated feedback current and rated current; A PI control step of calculating and outputting a control voltage variation based on the detected error current; Limiting and outputting a maximum value of the control voltage variation amount; And Intermitting the supply of the control voltage fluctuation amount to suppress an overcurrent trip of the inverter system according to the acceleration / deceleration control signal; Inertial load suppression method of the inverter system comprising a. The method of claim 5, wherein the suppression of the overcurrent trip, And if the feedback current is greater than the rated current, generating an amount of control voltage fluctuation to add or subtract to the voltage command value to suppress an overcurrent trip. The method of claim 5, wherein the suppression of the overcurrent trip, And if the feedback current is not greater than the rated current, correcting the voltage command value by using the error accumulation value of the frequency variation amount and the control voltage variation amount to quickly return to a normal state.

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