JP2000092852A - Pwm inverter controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely output/estimate voltage by adding correction values discriminated by phases and the polarity of the output current of the respective phases to the voltage commands of the respective phase, and making signal waves compared with a modulation wave. SOLUTION: A correction value storage unit 5ap stores a correction value when the current of an a-phase is positive and a correction value storage unit 5an stores the correction value when the current of the a-phase is negative. Correction value storage units 5bp, 5bn, 5cp and 5cn are similar. A switch 11a selects the output of the correction value storage unit 5ap when the current of the a-phase is positive and selects a value obtained by multiplying the output of the correction value storage unit 5an by -1 when the current of the a-phase is negative. The correction values of the respective phases selected by the switches 11a, 11b and 11c are added with the voltage commands of the respective phases, which are the outputs of a voltage command generator 3 in adders 4a, 4b and 4c. The outputs of the adders 4a, 4b and 4c are compared with the triangular wave of the output of a modulation generator 7 in comparators 10a, 10b and 10c. They are outputted to a PWM inverter 1 as switching signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PWM inverter control device for generating a predetermined voltage with high accuracy by a PWM inverter and estimating the output voltage of the PWM inverter with high accuracy.

[0002]

2. Description of the Related Art FIGS. 3 and 4 are block diagrams showing an example of a conventional PWM inverter control device. The prior art will be described with reference to these drawings. In FIG. 3, PWM
The inverter 1 applies a voltage based on the switching signal of each phase to the load 2. The current detectors 9a, 9b, 9c detect the current of each phase. Current polarity discriminators 8a, 8
b, 8c determine the polarity of the current of each phase,
When the current is flowing from the PWM inverter 1 to the load 2, that is, when the current is positive, 1 is output, and when the current is flowing in the opposite direction, that is, when the current is negative, -1 is output. The product of the correction value of the output of the correction value storage 5 and the output of the current polarity discriminators 8a, 8b, 8c is multiplied by multipliers 6a, 6
b, 6c, and are added to the voltage command of each phase of the output of the voltage command generator 3 in the adders 4a, 4b, 4c. The outputs of the adders 4a, 4b, 4c are compared with the triangular wave output from the modulation wave generator 7 by the comparators 10a, 10b, 10c, respectively, and output to the PWM inverter 1 as a switching signal. That is, the voltage command to be compared with the triangular wave is
When the current is positive, the correction value is increased by the correction value of the output of the correction value storage 5, and when the current is negative, the correction value is decreased by the correction value.

The reason why the voltage command is corrected according to the polarity of the current as described above will be described below. FIG. 5 shows the relationship between the one-phase switching signal Sx and the output voltage waveform Vx of the corresponding phase of the output of the PWM inverter 1. PW
The one-phase configuration of the M inverter 1 is as shown in FIG. 6, and the two switching elements operate like Qxp and Qxn in FIG. Usually, in order to avoid that Qxp and Qxn are turned on at the same time, a short-circuit prevention period is provided during which switching signals are switched off at the same time. Thereby, as shown in the waveform of Vx in FIG.
When the current is positive (ix> 0), the pulse width of Vx is Sx
If the current is negative (ix <0), then
The pulse width of Vx becomes wider than that of Sx. Therefore Vx
The pulse width of Sx is corrected by correcting the voltage command to be compared with the triangular wave so that the pulse width becomes the same as the voltage command.

In FIG. 4, a voltage estimator 14 comprising a correction value, a multiplier, a subtractor, and a current polarity discriminator is provided, and comparators 10a, 10b, and 10c determine a voltage command of each phase compared with a triangular wave. , Multiplier 6 which is a correction value of each phase
The outputs of a, 6b and 6c are subtracted by subtractors 13a, 13b and 13c.
, The voltage applied to the load 2 is estimated and output.

When the voltage estimation is obtained as described above, the reason why the voltage command is corrected by the value corresponding to the current polarity is as described in FIG. This is because a pulse having the waveform Vx cannot be obtained.

[0006]

In FIGS. 5 and 6, the switching element Qxp turns on with a delay of Tdpon,
It is assumed that Tdpoff has a characteristic of turning off with a delay. The switching elements Qxn have T
dnon and Tdnof. Then, when the current is positive, V
The ON pulse width of x is Ton− (Tdpon−Tdpo
f), and when the current is negative, the ON pulse width of Vx is T
on + (Tdnon−Tdnof). Tdpon
If −Tdpof = Tdnon−Tdnof, the above-described correction value of the related art may be equivalent to Tdpon−Tdpof or Tdnon−Tdnof. However, since the characteristics of each switching element are not always uniform, Tdp
On-Tdpof = Tdnon-Tdnof does not generally hold. Then, in the prior art, there is only one correction value, so that correction cannot be performed with a correct correction value. From the above,
The voltage cannot be output as instructed, or the error of the estimated voltage of the output of the voltage estimator from the actual voltage increases. The present invention has been made in view of the above points,
An object of the present invention is to provide a PWM inverter control device which solves these drawbacks, can obtain a voltage output as instructed, and does not increase the error between the estimated voltage of the output of the voltage estimator and the actual voltage. It is in.

[0007]

Means for achieving the object are as follows: 1) In claim 1, a correction value that is distinguished by the polarity of the phase and the output current of each phase in the voltage command of each phase. Are added to obtain a signal wave to be compared with the modulated wave. 2) In claim 2, the output voltage of each phase is estimated by subtracting the correction value distinguished by the polarity of the phase and the output current of each phase from the signal wave. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment according to claim 1 of the present invention, and FIG. 2 is a block diagram showing an embodiment according to claim 2 of the present invention. 3 and 4 have the same configuration and function. 1 and 2, the correction value storage 5ap stores a correction value when the current of the a-phase is positive. The correction value storage 5an stores a correction value when the current of the a-phase is negative. The same applies to the correction value storages 5bp, 5bn, 5cp, 5cn. The switch 11a activates the correction value storage 5 when the current of the a-phase is positive.
The output of ap is selected, and when the a-phase current is negative, a value obtained by multiplying the output of the correction value storage 5an by -1 is selected. The same applies to the switches 11b and 11c.

In FIG. 1, switches 11a and 11
The correction value of each phase selected by b, 11c and the voltage command of each phase of the output of voltage command generator 3 are added to adders 4a, 4b, 4c.
Is added to. The outputs of the adders 4a, 4b, 4c are the triangular wave of the output of the modulated wave generator 7 and the
The signals are compared at 0a, 10b, and 10c and output to the PWM inverter 1 as a switching signal.

In FIG. 2, a voltage estimator 1 comprising each correction value storage, a current polarity discriminator, a subtractor and a switch.
4, the comparators 10a, 10b, and 10c determine the switches 11a, 11
b, 11c, the subtractor 13a,
By subtracting at 13b and 13c, the voltage applied to the load 2 is estimated and output.

[0011]

As described above, according to the present invention, the PW
Equipped with six correction values considering the deviation of the characteristics of each switching element of the M inverter, and these can be selected according to the current polarity of each phase, so that the correction of the voltage command and the correction of the voltage estimation can be accurately performed. Since it can be performed, accurate voltage output and accurate voltage estimation can be performed, which is extremely useful in practical use.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a block diagram of one embodiment used for voltage estimation according to claim 2 of the present invention.

FIG. 3 is a block diagram of a conventional PWM inverter control device.

FIG. 4 is a block diagram of voltage estimation of a conventional PWM inverter control device.

FIG. 5 is a relationship diagram between a one-phase switching signal and an output voltage waveform.

FIG. 6 is a configuration diagram of one phase of a PWM inverter.

[Explanation of symbols]

Reference Signs List 1 PWM inverter 2 Load 3 Voltage command generator 4a, 4b, 4c Adder 5, 5ap, 5an, 5bp, 5bn, 5cp, 5cn
Correction value storage 6a, 6b, 6c Multiplier 7 Modulated wave generator 8a, 8b, 8c Current polarity discriminator 9a, 9b, 9c Current detector 10a, 10b, 10c Comparator 11a, 11b, 11c Switch 13a, 13b, 13 Subtractor 14 Voltage estimator

Claims (2)

[Claims] A PWM for controlling a PWM inverter by generating a switching signal by comparing a magnitude of a signal wave with a modulated wave represented by a triangular wave using a voltage command of each phase as a signal wave. In the inverter control device,
A PWM inverter control device, wherein a correction value distinguished by a polarity of a phase and an output current of each phase is added to the voltage command of each phase by an adder to obtain the signal wave, thereby providing a PWM signal. 2. A PWM inverter control device having a function of estimating an output voltage of each phase by using a signal wave of each phase which is compared with a modulated wave to generate a switching signal. A PWM inverter characterized in that a correction value distinguished by a polarity of a phase and an output current of each phase is subtracted from a phase signal wave by a subtractor, and an output voltage of each phase is estimated by a voltage estimator. Control device.