JPH0487571A - Control device for inverter device - Google Patents

Abstract

PURPOSE:To suppress the variations of AC output voltage by operating an estimated voltage variation of a DC capacitor to be generated, when power supply is switched from a commercial AC power source over to the second converter, and by correcting an AC voltage command for the second converter so as to correct the voltage variation. CONSTITUTION:When a switching signal is generated in a state that the first switch 9A is off and the second switch 9B is on, the first switch 9A is switched on and the second switch 9B is switched off, and power is supplied to a load 11 from an inverter 6. Simultaneously, a voltage variation calculator 21 calculates and estimates the variation (k) of the terminal voltage of a DC capacitor 4 to be generated by the switching on the basis of the output P from a power calculator 20. A divider 22 divides a voltage amplitude command V* from an amplitude command operator 15 by this voltage variation (k), and its divided value A/B is given to an AC voltage command operator 16. Accordingly, AC voltage commands Vu*, Vv*, Vw* are corrected so that the DC voltage variation may be corrected.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention relates to a constant voltage/constant frequency inverter device (hereinafter referred to as CV
This invention relates to a control device for a CF inverter device (referred to as a CF inverter device), and in particular to a control device for an inverter device that can suppress fluctuations in AC output voltage that occur when switching power supply to a load from a commercial AC voltage source to an inverter. It is.

(Prior Art) Generally, a CVCF inverter device is used as an uninterruptible power supply device or an independent power supply device for supplying power to a device such as a computer that cannot tolerate instantaneous power outage. This CVCF inverter is required to always supply a stable voltage to the load.

FIG. 4 is a block diagram showing an example of the configuration of a conventionally used CVCF inverter device of this type.

In FIG. 4, a commercial AC voltage source 1 and an AC voltage source 1 are shown.
A rectifier circuit 2, which is a first converter that converts the AC output from the rectifier circuit 2 into DC, a DC reactor 3, a DC capacitor 4, a capacitor 5, and a gate signal G, which will be described later, for the DC output from the rectifier circuit 2. G.

A second converter that connects an inverter 6, which is a second converter that modulates according to Gv and converts it into AC, an AC reactor 7, an AC capacitor 8, and an AC output terminal 10 to which an output terminal of the inverter 6 and a load 11 are connected. 1 switch 9A,
A main circuit is configured from a second switch 9B that directly connects the output terminal of the AC voltage source 1 and the AC output terminal 10, and supplies power to the load 11 via the AC output terminal 10.

On the other hand, the voltage detector 12, the amplitude detector 13, and the adder 1
4, amplitude command calculator 15, and AC voltage command calculator 16
, a carrier wave generator 17, and a gate signal generator 18 constitute a control device.

In such a CVCF inverter device, an AC voltage source 1
The AC output from the rectifier circuit 2 is converted to DC by the rectifier circuit 2. At this time, it is assumed that the DC output from the rectifier circuit 2 is controlled to be approximately constant. Rectifier circuit 2
The DC output obtained from the DC reactor 3 and the DC capacitor 4 reduce ripples, and is supplied to the inverter 6 and the capacitor 5 . This condenser 5 is provided so that power can be supplied to the inverter 6 even when AC output cannot be obtained from the AC voltage source 1 due to a power outage or the like.

The power supplied to the inverter 6 is G,,G,.

It is modulated according to G and converted into alternating current. Inverter 6
The AC reactor 7 and the AC capacitor 8 remove harmonic components from the AC output obtained from the AC output.

Normally, the first switch 9A is on and the second switch 9B
is used in an off state, and power is supplied to the load 11 from the inverter 6. On the other hand, when the inverter 6 is in an overcurrent state, such as when too much load current flows due to an accident such as a load short circuit, the first switch 9A is turned off and the second switch 9B is turned off.
By turning on the inverter 6, the inverter 6 is protected.

Then, when the inverter 6 is no longer in an overcurrent state, the first switch 9A is turned on and the second switch 9B is turned off again, so that the load 11 is again supplied with power from the inverter 6.

In this case, control when power is being supplied from the inverter 6 to the load 11 is performed as follows. That is, the voltage supplied to the load 11 is detected by the voltage detector 12.
and is manually input to the amplitude detector 13. Then, in the amplitude detector 13, the output V of the voltage transverse ratio device 12,
The voltage amplitude is detected from V, ,V, and the voltage amplitude value ■6.
．． is input to the adder 14. Then, the adder 14 compares the voltage amplitude command V r e l and the voltage amplitude value V, . The amplitude command calculator 15 outputs a voltage amplitude command (1) that reduces the deviation output from the adder 14. In addition, the AC voltage command calculator 16 calculates three-phase AC voltage commands v, , v, , v,'' from the voltage amplitude command v8 and phase command θ8 from the amplitude command calculator 15 as shown in the following equation. It is calculated and input to the gate signal generator 18.

V, "-V" -CO3(θ) Vv -V"-CO8(θ-(:l)r/3))V,
"-V" -COS (θ+(2π/3)) On the other hand, the carrier wave generator 17 generates a carrier wave e having a frequency sufficiently faster than the output frequency of the inverter 6.

is input to the gate signal generator 18. This results in
In the gate signal generator 18, AC voltage commands V, , V
, ,V, and the carrier wave e, are compared, and gate signals G, ,G, ,G, are output to the inverter 6. This AC voltage command V. y.

vv'' and carrier wave e, and gate signal G u * Gw
The relationship with +G is shown in Figure 5.

By the way, in such a CVCF inverter device, when switching the load 11 from a state in which power is being supplied from the AC voltage source 1 via the second switch 9B to the inverter 6, a voltage change at the time of switching occurs. In order to reduce the voltage, it is necessary to match the magnitude and phase of the output voltage of the inverter 6 with the voltage of the AC voltage source 1 before switching.

However, since the inverter 6 shifts from a no-load state to a full-load state at the time of such switching, the inverter current I lay in FIG. 4 increases, and the DC capacitor 4
voltage decreases. Then, the AC voltage command v at this time,
Assuming that ,v, ,v,'' is constant, the output voltage of the inverter 6 changes in proportion to the DC voltage, so the AC output voltage decreases.The situation at this time is shown in Figure 6. Become.

Therefore, as a method to eliminate such a drop in the AC output voltage, the capacitance of the DC capacitor 4 may be increased to make it difficult for the terminal voltage of the DC capacitor 4 to drop, or the terminal voltage of the DC capacitor 4 may be detected and the terminal voltage Is there a way to compensate for the variation on the AC side? However, the former method has the problem of increasing the size of the device, and the latter method requires the addition of a high-speed detector for DC voltage detection, which poses a problem in terms of cost.

(Problems to be Solved by the Invention) As described above, in the conventional control device for an inverter device,
There is a problem in that it is not possible to suppress fluctuations in the AC output voltage that occur when switching the power supply to the load from a commercial AC voltage source to an inverter.

An object of the present invention is to control a small, inexpensive, and extremely reliable inverter device that can suppress fluctuations in AC output voltage that occur when switching power supply to a load from a commercial AC voltage source to an inverter. The goal is to provide equipment.

[Configuration of the Invention (Means for Solving the Problem) In order to achieve the above object, the present invention includes a first converter that converts an AC output from a commercial AC voltage source into DC;
a second converter that modulates the DC output from the first converter according to an AC voltage command and converts it into AC; a first switch that connects the output terminal of the second converter and the AC output terminal;
In a device for controlling an inverter device configured to directly connect an output terminal of an AC voltage source and a second switch that directly connects the AC output terminal, the AC output terminal is configured to supply power to a load via the AC output terminal. a power detection means for detecting the power supplied to the load via the power detector; When switching to the first converter, the fluctuation of the DC voltage that is the output of the first converter is calculated and predicted from the power detected by the power detection means from the characteristics of the converter, and the change of the DC voltage is calculated based on the prediction result. It is configured to include a correction means for correcting the AC voltage command of the second converter so as to correct the fluctuation.

(Function) Therefore, in the control device for an inverter device according to the present invention, the power detection means detects the power being supplied to the load via the AC output terminal, and the power supply is switched from the commercial AC voltage source to the second When switching to a converter, the voltage fluctuation of the DC capacitor caused by stepwise application of power is calculated in accordance with the characteristics of the converter, and the AC of the second converter is adjusted to compensate for the voltage fluctuation. By correcting the voltage command, it is possible to suppress fluctuations in the AC output voltage when switching the power supply to the load from a commercial AC voltage source to the second converter, and further improve the high-speed controllability of the first converter. By not requiring , the cost of the device can be reduced.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of the configuration of a CVCF inverter device equipped with a control device according to the present invention. The same elements as those in FIG. I will only describe it.

That is, in this embodiment, in addition to the control device shown in FIG.
It is configured by providing a current detector 19, a power calculator 20, a DC voltage fluctuation calculator 21, and a divider 22.

Here, the current detector 19 detects the current flowing to the load 11 via the AC output terminal 10. Further, the power calculator 20 inputs the output from the current detector 19 and the output from the voltage detector 12, and calculates the power supplied to the load 11 via the AC output terminal 10 based on these. It is something to do. Furthermore, the DC voltage fluctuation calculator 21
The output from the power calculator 20 is input, and the first switch 9
When a switching signal for switching from a state where A is off and the second switch 9B is on to a state where the first switch 9A is on and the second switch 9B is off is input, the power calculator 20 Based on the output from the rectifier circuit 2, the fluctuation in the output DC voltage of the rectifier circuit 2 is calculated and predicted from the characteristics of the rectifier circuit 2, and the DC voltage fluctuation value is calculated. Furthermore, the divider 22 divides the voltage amplitude command from the amplitude command calculator 15 by the DC voltage fluctuation value from the DC voltage fluctuation calculator 21, and outputs the divided value to the AC voltage command calculator 16. It is something to do.

Here, the voltage detector 12, the current detector 19, and the power calculator 20 constitute a power detection means, and the DC voltage fluctuation calculator 21 and the divider 22 constitute a correction means.

Next, the operation of this embodiment configured as above will be explained.

In FIG. 1, the first switch 9A is now turned off, and the second
It is assumed that power is being supplied to the load 11 from the AC voltage source 1 with the switch 9B in the on state. Further, the output voltage of the inverter 6 is equal to the output voltage of the AC voltage source 1 and the magnitude 9
It is assumed that the motors are operated with the same phase.

In the power calculator 20, the output 1. from the current detector 19. ．．
1. ．． 1. and the output V from the voltage detector 12. ,V,,
From V=, the power P being supplied to the load 11 via the AC output terminal 10 is calculated. That is, this power P
,I,,1. .

1, and V, ,V, ,V, by the following calculation.

P-1, -V, , +Iy-V, +1. −V=on the other hand, the first
When a switching signal is generated from the state in which the first switch 9A is off and the second switch 9B is on, the first switch 9A is turned on and the second switch 9B is turned off, and the load 11 is turned off. Power is supplied from an inverter 6.

At the same time, the voltage fluctuation calculator 21 also uses the power calculator 2.
Based on the output P from 0, a fluctuation value k of the terminal voltage of the DC capacitor 4 (output DC voltage of the rectifier circuit 2) caused by the switching is calculated and predicted. Then, in the divider 22, the voltage amplitude command v1 from the amplitude command calculator 15 is divided by this DC voltage fluctuation value k, and the divided value A/B is given to the AC voltage command calculator 16. AC voltage command v to correct voltage fluctuations
, ,vv,v,'' are corrected.The situation at this time is shown in Fig. 2.

As described above, in the control device for an inverter device according to the present embodiment, a switching signal for supplying power from the inverter 6 to the load 11 is given from a state where power is being supplied to the load 11 from the AC voltage source 1. DC capacitor 4 from the power output P being supplied to the load 11 when
By calculating and predicting the fluctuation value k of the terminal voltage (output DC voltage of the rectifier circuit 2), and dividing the voltage amplitude command v8 from the amplitude command calculator 15 by this DC voltage fluctuation value k, the DC voltage is calculated. AC voltage command v to compensate for fluctuations
, , v, v,''.

Therefore, by calculating the fluctuation of the DC voltage, the AC voltage command V
D. Since y, , y, * are corrected, there is no control delay, and fluctuations in the AC output voltage that occur when switching the power supply to the load 11 from the commercial AC voltage source 1 to the inverter 6 are suppressed. This makes it possible to smoothly switch the power supply from the commercial AC voltage source 1 to the inverter 6. This eliminates the need to increase the capacitance of the DC capacitor 4 or add a high-speed detector for DC voltage detection as in the past (in other words, it is not necessary to add a rectifier circuit 2 with a slow response on the DC side). ), it is possible to reduce the size and cost of the device. Therefore, since the AC output voltage does not fluctuate, there is no adverse effect on the load 11.

Next, other embodiments of the present invention will be described.

FIG. 3 is a diagram showing a configuration example of a CVCF inverter device equipped with a control device according to another embodiment of the present invention;
Elements that are the same as those in the figures are given the same reference numerals and their explanations are omitted.
Only the different parts will be described here.

That is, in this embodiment, in the control device of FIG.
The DC voltage fluctuation calculator 21 and the divider 22 are omitted, and a pattern ROM 23 and a multiplier 24 are provided in their place.

Here, the pattern ROM 23 stores in advance a correction gain as a pattern that corrects the variation at the time of switching in accordance with the characteristics of the rectifier circuit 2, and inputs the output from the power calculator 20, and From the state where the first switch 9A is off and the second switch 9B is on, the first
When a switching signal is input to turn on the switch 9A and turn off the second switch 9B, a correction gain is output based on the output from the power calculator 20. Further, the multiplier 24 multiplies the voltage amplitude command from the amplitude command calculator 15 by the correction gain from the pattern ROM 23 and outputs the multiplied value to the AC voltage command calculator 16. Here, pattern RO
The M23 and the multiplier 24 constitute a correction means.

In this embodiment, by writing the correction gain to be added at the time of switching as a pattern into the pattern ROM 23 in advance, the load 1
It becomes possible to suppress fluctuations in the AC output voltage that occur when switching the power supply to the AC voltage source 1 from the commercial AC voltage source 1 to the inverter 6. Further, when changing the parameters of the DC circuit section, it is only necessary to replace the pattern ROM 23, so the entire control device can be shared among many models, and the device can be made inexpensive.

[Effects of the Invention] As explained above, according to the present invention, the power being supplied to the load via the AC output terminal is detected, and the power supply is switched from the commercial AC voltage source to the second converter. At this time, the voltage fluctuation of the DC capacitor caused by the stepwise addition of power is predicted and calculated according to the characteristics of the converter, and the AC voltage command of the second converter is corrected to compensate for the voltage fluctuation. This makes it possible to control a small, inexpensive, and extremely reliable inverter device that can suppress fluctuations in AC output voltage that occur when switching the power supply to a load from a commercial AC voltage source to an inverter. Equipment can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a CVCF inverter device equipped with a control device according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the same embodiment, and FIG. 3 is a control device according to the present invention. 4 is a block diagram showing a configuration example of a conventional CVCF inverter device; FIG. 5 is a waveform diagram for explaining the operation in FIG. 4; FIG. 6 is a waveform diagram for explaining the problems in FIGS. and 4. DESCRIPTION OF SYMBOLS 1... AC voltage source, 2... Rectifier circuit, 3... DC reactor, 4... DC capacitor, 5... Capacitor, 6... Inverter, 7... AC reactor, 8...
...AC capacitor, 9A...first switch, 9B
...Second switch, 10...AC output terminal, 11
Load, 12 Voltage detector, 13 Amplitude detector, 14 Adder, 15 Amplitude command calculator,
16... AC voltage command calculator, 17... Carrier wave generator, 18... Gate signal generator, 19... Current detector, 20... Power calculator, 21... DC voltage fluctuation Arithmetic unit, 22... Divider, 23... Pattern ROM,
24... Multiplier.

Claims (1)

[Claims] A first method for converting AC output from a commercial AC voltage source into DC.
a second converter that modulates the DC output from the first converter in accordance with an AC voltage command and converts it into AC;
A first switch that connects the output terminal of the second converter and the AC output terminal, and a second switch that directly connects the output terminal of the AC voltage source and the AC output terminal, A device for controlling an inverter device configured to supply power to a load via an AC output terminal, comprising: power detection means for detecting power supplied to the load via the AC output terminal; and the first switch. When switching from a state where the second switch is off and the second switch is on to a state where the first switch is on and the second switch is off, the power detected by the power detection means is used to convert the power detected by the power detection means to the first converter. calculate and predict fluctuations in the DC voltage that is the output of the converter from the characteristics of the converter, and correct the AC voltage command of the second converter so as to correct the fluctuations in the DC voltage based on the prediction result. 1. A control device for an inverter device, characterized in that it comprises a correction means for