JP2742154B2 - Short circuit prevention time correction device for voltage type inverter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for correcting a short-circuit prevention time of a voltage type inverter used for controlling an induction motor at a variable speed.

[0002]

2. Description of the Related Art FIG.
C Servo System Theory and Practice of Design ”, P54-P5
9, a block diagram showing a conventional short-circuit prevention time correction device for a voltage-type inverter shown in the first edition of May 8, 1990, in which 5 is a U-phase voltage-type inverter device, and 6 is a current. Detector, 7 is a three-phase induction motor (hereinafter referred to as a motor), 12 is a pulse width modulation circuit, and 13 is a short-circuit prevention time generation for generating a short-circuit prevention time so that two transistors connected in series are not turned on simultaneously. Circuit, 1
Reference numeral 6 denotes a correction voltage generation circuit for generating a correction voltage ΔV from a U-phase inverter output current, and reference numeral 20 denotes a DC voltage source. FIG. 3 is a timing chart showing signals of the respective blocks in FIG.

Next, the operation will be described. First, a voltage command value _Vu3 ^* is input to a pulse width modulation circuit 12 necessary for controlling the inverter output voltage. The pulse width modulation circuit 12, as shown in FIG. 3 (a), to compare the magnitude of this voltage command value V _u3 ^* and internal triangular wave E, V _u3 ^* ≧
When E, and outputs an ON signal of the U-phase upper transistor T _u U ^* as shown in FIG. 3 (b), when the V _u3 ^* <E, U
Outputs an ON signal X ^* phase lower transistor T _x as shown in Figure 3 (c). However, in this state, because of the off-delay time of each transistor T _u, T _x, there is a period during which the transistor T _u, T _x is simultaneously turned on, the DC power source short circuit is generated. Therefore, in order to prevent this DC power supply short circuit, when each of the signals U ^* and X ^* is turned on, the short circuit prevention time td
The signals U and X as shown in FIGS. 3D and 3E with only a delay in the rise are generated by the short-circuit prevention time generation circuit 13.

According to the signal generated by the short-circuit prevention time generating circuit 13, an error voltage Δv is generated for a time corresponding to the hatched portions in FIGS. 3 (d) and 3 (e). Therefore, the order to correct the error voltage Delta] v, as shown in FIG. 2, the current detector current I _u flowing in the motor 7 6
And if I _u ≧ 0, ΔV = + V _td , I _u <
In the case of 0, a voltage that satisfies ΔV = −V _td is created by the correction voltage generation circuit 16, and is added to the original voltage command value V _u2 ^* and the voltage command value V _u3 ^* to be input to the pulse width modulation circuit 12 ^. Has been created. V _td is represented by the following equation (1).
_d is a DC voltage, td is a short circuit prevention time, and fc is a frequency of the pulse width modulation signal E.

[0005]

[Number 1] _{V td ≒ E d × td ×} fc

[0006]

Since the conventional apparatus for correcting short-circuit prevention time of a voltage-type inverter is constructed as described above, a current actually flowing through the motor 7 is detected to correct the error voltage. It is necessary to create a correction voltage ΔV that should be corrected. Further, since the detected current contains a harmonic component caused by the pulse width modulation operation, the correction voltage ΔV fluctuates when the current becomes near zero, and the correction performance becomes poor. There were issues such as worsening.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and it is possible to accurately correct a short-circuit prevention time without being affected by a harmonic component caused by a pulse width modulation operation. It is an object of the present invention to obtain a short-circuit prevention device for a voltage-type inverter that can be used.

[0008]

According to a first aspect of the present invention, there is provided an apparatus for correcting short-circuit prevention time of a voltage type inverter, comprising: a current detection value of a current detector of an inverter connected to a DC voltage power supply; and a preset current command value. A current controller that outputs a control signal based on the error of the current command value, a short-circuit prevention time correction voltage generation circuit that generates a short-circuit prevention time correction voltage based on the sign of the current command value, and a correction obtained by the correction voltage generation circuit. An adder for applying a voltage to the control signal output by the current controller, a pulse width modulation circuit for performing pulse width modulation control based on the output of the adder, and a series connected to a DC voltage power supply based on the output of the pulse width modulation circuit. a dead time generation circuit for supplying a short-circuit prevention time output signal for controlling the transistors constituting the connected the voltage source inverter, the transistors There are those having a stop means for stopping the supply to the adder period correction voltage not switching.

[0009]

The correction voltage generating circuit according to the first aspect of the present invention
Since the correction voltage for the short-circuit prevention time is created based on the preset current command value, the correction voltage does not include the harmonic component caused by the pulse width modulation operation by the pulse width modulation circuit, and the correction near the current zero is performed. In addition, the stopping means stops the supply of the correction voltage to the adder during a period when the transistor is not switching, and further suppresses the fluctuation of the correction voltage near the zero current and the deterioration of the correction function. Function to prevent more reliably.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 5 denotes a voltage source inverter device, 6 denotes a current detector for detecting a motor drive current, 7 denotes a motor, 9
Is a current controller that outputs a control current based on an error between the detected current from the current detector 6 and a current command value, 12 is a pulse width modulation circuit, 13 is a short circuit prevention time creation circuit, 14 is an adder, and 16 is a short circuit prevention time , A signal selection circuit, 18 a correction cycle determination circuit, and 20 a DC voltage power supply.

Next, the operation will be described. First, the current controller 9 determines the current command values _Iu ^* , _Iv ^* , _Iw ^* and the motor 7
Current value I of the current supplied to the
_u, I _v, for matching the I _w, based on these differences, performs U, V, W phases of the current control, the output of the current controller 9, respectively V _u2 ^*, V _v2 ^*, V _w2 ^* . The reference inputs of the correction voltage generating circuit 16 are the above-mentioned current command values _Iu ^* , _Iv ^* , _Iw ^*, and a correction voltage ΔV for the short-circuit prevention time is created by the sign of each current command value. 14 each voltage command value I _u2 ^*, I _v2 ^*, it is added to the I _w2 ^*, an input signal of the pulse width modulation circuit. Further, a period during which switching is not performed is detected by the correction cycle determination circuit 18.

More specifically, for example, for the U phase, the short-circuit prevention time correction voltage generation circuit 16 generates ΔV = + V _td when the current command value I _u ^* = 0 and ΔV when I _u ^* <0. = −V _td are generated. Further, as the current command value I _u ^* and the detected current value I _u match, enter the difference I _u ^* -I _u of it to the current controller 9 performs the current control as described above.

Now, the output of the current controller 9 is V _u2 ^*
Then, the adder 14 adds the correction voltage ΔV output from the correction voltage generation circuit 16 to the output V _u3 ^*
Create Here, the correction voltage ΔV is set when V _u2 ^* is larger than the maximum value of the pulse width modulation carrier or smaller than the minimum value, that is, V _u2 ^* ≧ E _max or V _u2 ^* ≦ −.
At the time of _Emax , it is set to 0. As a result, the addition of ΔV during the non-switching period is equivalently stopped. The determination of this period is performed by the correction cycle determination circuit 18.
ΔV = 0 is implemented by disconnecting a switch in the signal selection circuit 17. Then, V _u3 ^* is input to the pulse width modulation circuit 12, and further, the short circuit prevention time creation circuit 1
By inputting to 3, to create a signal to be supplied to the base of the transistor T _u, T _x. Although the U-phase has been described in the above embodiment, the same operation is performed for the V-phase and the W-phase.

[0014]

As described above, according to the first aspect of the present invention, the control signal is generated based on the error between the current value detected by the current detector of the inverter connected to the DC voltage power supply and the preset current command value. A current controller to output, a short-circuit prevention time correction voltage generation circuit for generating a short-circuit prevention time correction voltage based on the sign of the current command value, and a correction voltage obtained by the correction voltage generation circuit. An adder to be added to the control signal; a pulse width modulation circuit for performing pulse width modulation control based on the output of the adder; and the voltage source inverter connected in series to a DC voltage power supply based on the output of the pulse width modulation circuit. a dead time generation circuit for supplying a short-circuit prevention time output signal for controlling the transistors constituting a correction electric during a period when the transistor is not switching Since it is configured to supply to the adder to comprise a stop means for stopping, to the pulse width modulation operation
To prevent the incorporation of harmonic components caused by
Deterioration of correction performance in the vicinity can be avoided, and each series
Prevents short circuit of DC power supply by transistor with high accuracy
There is an effect that what can be obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an apparatus for correcting a short-circuit prevention time of a voltage type inverter according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a conventional device for correcting a short-circuit prevention time of a voltage-source inverter.

FIG. 3 is a timing chart showing signals of respective blocks in FIGS. 1 and 2;

[Explanation of symbols]

 Reference Signs List 6 Current detector 7 Three-phase induction motor (motor) 9 Current controller 12 Pulse width modulation circuit 13 Short circuit prevention time creation circuit 14 Adder 16 Correction voltage generation circuit 20 DC voltage power supply

Claims (1)

(57) [Claims] 1. A DC voltage power supply is converted into AC power and supplied.
Current detection to detect the supply current to the load of the voltage type inverter
And the current value detected by the current detector and preset.
Current that outputs a control signal based on the error with the current command value
Short-circuit prevention by the controller and the sign of the current command value
Short-circuit prevention time correction voltage generation to create time correction voltage
Circuit and the correction voltage obtained by the correction voltage generation circuit
Adder added to the control signal output by the current controller
And a pulse width modulation control based on the output of the adder.
A pulse width modulation circuit and an output of the pulse width modulation circuit.
And connected in series to a DC voltage power supply
Signal to control each transistor that composes the data.
The short-circuit prevention time creation circuit and the transistor
During the period in which switching is not performed, the correction voltage is supplied to the adder.
And a stop means for stopping the supply.
Short circuit prevention time correction device.