JPH06153528A - Inverter - Google Patents

Abstract

PURPOSE:To provide an inverter and a controlling method thereof that improves the distortion factor of an output voltage waveform. CONSTITUTION:An inverter is provided with an inverter 2 and an output filter 3, and an output voltage is detected by a voltage transformer 5 and an output voltage detecting filter 6. A deviation detecting means 8 detects a deviation between the detected voltage and a voltage set point set by an output voltage setting means 7. An output voltage waveform of the inverter 2 is controlled by providing an output from the deviation detecting means 8 to an operation signal preparation means 9. To eliminate a control time lag due to a primary delay element, an output voltage is detected from the secondary side of the instrument transformer 5, and a correction signal is outputted in accordance with a difference between the detected voltage and the voltage set point set by the output voltage setting means 7. Providing the correction signal without any substantial time lag has the effect of improving an output voltage distortion factor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device which suppresses distortion of an output voltage waveform caused by a sudden change in load current.

[0002]

2. Description of the Related Art A conventional method of controlling an output voltage waveform of an inverter is to detect an instantaneous value of an output voltage as described in Japanese Patent Application Laid-Open No. 2-81106, and use an output voltage waveform control means based on the detected value. A method of controlling the output voltage waveform is used. That is, after detecting the instantaneous value of the output voltage and passing it through a harmonic filter, the deviation voltage is detected by subtracting the instantaneous value of the detected output voltage value from the output voltage waveform command value. A waveform correction signal is created and output so as to remove this deviation voltage, and the target voltage waveform is maintained.

[0003]

However, when the load current changes, the output voltage waveform is distorted because the voltage drop amount changes due to the internal impedance of the DC power supply, the inverter and the output filter. This distortion is controlled to a target voltage value by an operation signal from the output voltage waveform control means, but since the operation signal has a time delay, when the load current suddenly changes, the control is not in time and the output voltage waveform changes. It will be distorted. If the output voltage waveform is distorted and harmonics are contained, adverse effects such as an increase in load loss will occur.

Therefore, when connecting a load with large fluctuations, the capacity of the inverter is allowed to have a margin with respect to the load to reduce the amount of voltage drop of the internal impedance, and the output side of the inverter has a lower harmonic wave. Although a measure is taken such as adding a filter to reduce the distortion factor of the output voltage, there is a drawback that the device becomes large in both cases. An object of the present invention is to provide an inverter device that improves the distortion factor of the output voltage waveform with respect to a sudden load change.

[0005]

In order to achieve the above object, P created based on a waveform command of an output voltage and a carrier wave.
A voltage detection unit that detects an AC output voltage of an inverter controlled by a WM signal, an output voltage detection filter for removing harmonics that is connected to an output of the voltage detection unit, and a reference value of the AC output voltage are set. Output voltage setting means, deviation detecting means for subtracting the output of the output voltage detecting filter from the output of the output voltage setting means, and a waveform of the output voltage for removing the deviation according to the output of the deviation detecting means. In an inverter device provided with an operation signal creating means for creating and outputting, a difference detecting means for obtaining a difference between an output of the voltage detecting means and an output of the output voltage setting means, and an output of the difference detecting means are arbitrary. It is provided with an operation signal correction amount adjusting means for adjusting the value to a value and an operation signal correcting means for adding the output of the operation signal correction amount adjusting means to the output of the operation signal creating means. It was the inverter apparatus.

Further, current detecting means for detecting an AC output current of the inverter device, current change detecting means for detecting a current change in the output of the current detecting means, and output of the current change detecting means for the operation signal generating means. Operation signal correction means for adding to the output of the above may be provided.

[0007]

With this structure, the above-mentioned object can be achieved by the present invention by the following operations. Harmonics are removed from the detected output voltage waveform by the output voltage detection filter. The deviation between the output waveform and the reference value is calculated by the deviation detecting means, and the signal is created and output by the operation signal creating means so as to remove the deviation to become the waveform command, and the output voltage is maintained at the predetermined waveform. .

However, the output voltage detection filter and the operation signal generating means used here are an operational amplifier, a resistor,
Since it is composed of a capacitor, there is a time delay in signal transmission, and when the load suddenly changes, the voltage waveform distortion caused by the voltage drop in the inverter device may not be sufficiently removed.

The detected output voltage waveform is directly subtracted by the difference detection means from the output of the output voltage setting means, which is a reference value, to obtain the output voltage waveform distortion. Since the output voltage detection filter is bypassed, there is no time delay, and since the harmonics are not removed, the distortion of the output voltage waveform is clearly detected. The difference corresponds to the waveform of the output voltage waveform to be corrected. By adding the signal of this difference to the output side of the operation signal generating means, the voltage waveform command can be output without a time delay. The signal of the difference may be adjusted to an arbitrary amount by the operation signal correction amount adjusting means and added, or the object can be achieved by directly adding. This makes it possible to obtain an inverter device in which the distortion of the output voltage waveform is small even when a load that changes rapidly is connected.

Further, the load current is detected, and its change is detected by the current change detecting means. Since this output corresponds to the timing and magnitude of distortion of the output voltage waveform, this output can be directly added to the output of the operation signal creating means to output the voltage waveform command, and the same purpose can be achieved. .

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

First, an example of conventional output voltage waveform control means is shown in FIG. In the figure, the DC power of the DC power supply 1 is converted into AC power by the inverter 2, the voltage waveform is adjusted by the output filter 3, and the load 4 is fed. Load 4 at this time
The instantaneous value of the AC voltage supplied to is detected by using the instrument transformer 5 and the output voltage detection filter 6 that removes harmonic components. The deviation detecting means 8 subtracts the detected instantaneous value from the voltage target value set by the output voltage setting means 7. The output voltage setting means 7 may be a sine wave voltage source multiplied by a multiplying voltage which is a waveform command. The deviation voltage calculated by the deviation detection means 8 is input to the operation signal creation means 9, and an operation signal for making the deviation voltage input therein zero is output to the control means of the inverter 2. In this way, the inverter 2 can maintain the voltage target value set by the output voltage setting means 7.

An example of the output voltage detection filter 6 is composed of an operational amplifier and an attached resistor / capacitor. A first-order lag element is included, and the output is delayed by the time constant due to the component. The operation signal generating means 9 may also be composed of an operational amplifier and a resistor / capacitor attached thereto.

FIG. 8 shows voltage waveforms of the above-mentioned respective parts.
(A) is a voltage waveform at the output end of the output filter 3, where the load current changes abruptly at point A and the waveform is distorted due to the large amount of voltage drop. (B) is a secondary side waveform of the instrument transformer 5. The waveform distortion at point A remains. (C) is the output side of the output voltage detection filter 6, and the waveform is considerably restored. (D) is an output waveform of the output voltage setting means 7 and is a target voltage. (E) is an output waveform of the deviation detecting means 8 and is a deviation voltage waveform obtained by subtracting (c) from (d). (F) is the output waveform of the operation signal creating means 9, and the waveform distortion at point A is corrected. A block diagram of one embodiment of the present invention is shown in FIG. The same components as those in FIG. 7 are indicated by the same symbols.

In FIG. 1, in this embodiment, a difference detecting means 10 for subtracting the voltage waveform detected from the secondary side of the instrument transformer 5 from the output of the output voltage setting means 7 is provided, and its output signal is operated. The signal correction means 11 is used as the operation signal creation means
Is added to the output of.

In this way, when the load current of the load 4 changes abruptly, the deviation between the output voltage and the voltage target value becomes
Since it is added to the output voltage waveform control means 20 without passing through the output voltage detection filter 6 including the first-order lag element and the operation signal creation means 9, it becomes possible to give the operation signal to the inverter 2 without time delay, and output. The distortion of the voltage waveform can be suppressed.

FIG. 2 shows the waveform of each part according to this embodiment. (A) shows the voltage waveform at the output end of the output filter 3, and is an example in which the load changes suddenly at point A. The distortion of the voltage waveform is improved over when controlled by the conventional technique.
(B) shows the secondary side waveform of the instrument transformer 5, (c) shows the output side of the output voltage detection filter 6, and there is almost no waveform distortion remaining. (D) is the output of the difference detection means 10
Voltage waveform distortion at the time of sudden load change is detected. (E)
Is the output waveform of the operation signal generating means 9 corresponding to the waveform command according to the conventional technique. In this case, although the waveform distortion at the point A is hardly corrected, the output of the operation signal correcting means output 11 shown in (f) is output. A clear correction signal is generated at.

FIG. 3 shows a second embodiment of the present invention.

In FIG. 3, the same components as in FIG.
It is shown using the same symbols. In FIG. 3, an instrument current transformer 12 is installed at the output end of the output filter 3 to detect an output current, and the detected current is input to a current change detection means 13 composed of a differentiation circuit to differentiate the detected current. A proportional signal is created and added to the output of the operation signal creation means 9 at the operation signal correction means output 11 to correct the operation signal of the output voltage waveform.

In this way, also in this embodiment, since the output voltage detection filter 6 including the first-order lag element and the operation signal generating means 9 are not passed, the operation is performed without a time delay by the signal according to the differentiation, that is, the change of the load current. It is possible to correct the signal,
The fluctuation of the output voltage waveform can be suppressed.

FIG. 4 shows the waveform of each part of the second embodiment.
(A) is a voltage waveform at the output end of the output filter 3, and (b) is a current waveform. The load is applied at point A in (a), and the load current begins to flow. (C) is an output waveform of the current change detection means 13, and the time and magnitude of the sudden change of the load current are detected by using a differentiating circuit. (D) is an operation signal creating means 9
(E) is the output of the operation signal correcting means output 11, and shows the voltage waveform command at point A.

FIG. 5 shows a third embodiment of the present invention.

FIG. 5 shows a difference between the difference detecting means 10 and the operation signal correcting means 11 in the block diagram described in FIG. The feedforward function can be composed of a gain or a combination of functions of gain, delay, and lead elements. Therefore, since the magnitude of the operation signal correction amount can be arbitrarily adjusted, by adding the operation signal correction amount adjusting means 14, an optimum operation signal correction amount is given to the output voltage waveform control means 20. It is possible,
Therefore, it becomes possible to perform optimum output voltage waveform control.

FIG. 6 shows the waveform of each part of the third embodiment.
(A) is an input waveform of the operation signal correction amount adjusting means 14, and shows a voltage waveform that needs to be corrected at point A where the load suddenly changes. Similarly, (b) is an output waveform, and shows the result of adjusting the gain of the input waveform and the like as necessary. (C) Operation signal creating means 9 and (d) are output waveforms of the operation signal correcting means output 11.

[0025]

According to the present invention, the output voltage waveform of the inverter device is detected, and the deviation from the target output voltage waveform is obtained,
When adding a correction signal to remove the deviation, it is compensated by means without time delay, so even if there is a sudden load change, the correction signal can be added without time delay to suppress the distortion of the output voltage waveform. There is an effect that can be improved.

[Brief description of drawings]

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

FIG. 2 is an example of a waveform of each part of a block showing an embodiment of the present invention.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is an example of a waveform of each part of a block showing a third embodiment of the present invention.

FIG. 5 is a block diagram showing a third embodiment of the present invention.

FIG. 6 is an example of a waveform of each part of a block showing a third embodiment of the present invention.

FIG. 7 is a block diagram showing a conventional example of an output voltage control circuit of an inverter.

FIG. 8 is an example of a waveform of each part of a block of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inverter 3 Output filter 4 Load 5 Instrument transformer 6 Output voltage detection filter 7 Output voltage setting means 8 Deviation detection means 9 Operation signal creation means 10 Difference detection means 11 Operation signal correction means 12 Instrument current transformer 13 Current change detection means 14 Operation signal correction amount adjustment means 20 Output voltage waveform control means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Toyoda 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Mihiro Taniguchi 3-chome, Saiwaicho, Hitachi, Ibaraki No. 1 Stock company Hitachi Ltd. Hitachi factory (72) Inventor Hayato Ishida 3-2-1, Saiwaicho, Hitachi City, Ibaraki Prefecture Hitachi Engineering Co., Ltd. (72) Inventor Yoshimi Sakurai Omika Town, Hitachi City, Ibaraki Prefecture 7-1-1, Hitachi, Ltd. Hitachi Research Laboratory

Claims (2)

[Claims] 1. A voltage detection means for detecting an AC output voltage of an inverter controlled by a PWM signal created based on an output voltage waveform command and a carrier wave, and a harmonic elimination connected to an output of the voltage detection means. Output voltage detection filter, output voltage setting means for setting a reference value of the AC output voltage, deviation detection means for subtracting the output of the output voltage detection filter from the output of the output voltage setting means, and the deviation detection In an inverter device including an operation signal creating unit that creates and outputs a waveform of an output voltage so as to remove the deviation according to the output of the unit, an output of the voltage detecting unit and an output of the output voltage setting unit. Difference detecting means for obtaining the difference between the operation signal, the operation signal correction amount adjusting means for adjusting the output of the difference detecting means to an arbitrary value, and the output of the operation signal correction amount adjusting means for the operation signal. An inverter device comprising an operation signal correction means for adding to the output of the creation means. 2. A voltage detection means for detecting an AC output voltage of an inverter controlled by a PWM signal created based on an output voltage waveform command and a carrier wave, and a harmonic elimination connected to an output of the voltage detection means. Output voltage detection filter, output voltage setting means for setting a reference value of the AC output voltage, deviation detection means for subtracting the output of the output voltage detection filter from the output of the output voltage setting means, and the deviation detection In an inverter device including an operation signal creating unit that creates and outputs a waveform of an output voltage so as to remove the deviation according to the output of the unit, a current detecting unit that detects an AC output current of the inverter unit, A current change detecting means for detecting a current change in the output of the current detecting means, and an operation signal correcting means for adding the output of the current change detecting means to the output of the operation signal creating means. An inverter device comprising a stage.