JP2782616B2 - Converter device control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a converter for converting a three-phase alternating current into a direct current. It relates to a control method.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a configuration of a conventional control circuit for turning on / off three sets of switching elements in a converter main circuit diagram. FIG. 5 shows a converter suitable for applying this control circuit. FIG. 4 is an explanatory diagram showing a main circuit of FIG. In FIG. 4, 1 is a DC current command value, 2 is a feedback value of the DC current, 3 is an adder, 4 is an error operational amplifier such as a PI amplifier, 5 is a multiplier,
6 is a sine wave generator, 8 is a triangle wave generator, 9 is a comparator, 10
Is a gate signal generator, and 11R is an R-phase synchronization signal of the sine wave generator. Similarly, 11S and 11T are S and T phase synchronization signals, respectively. 13R, 13S, and 13T represent R, S, and
The parts unique to the T phase are shown, and the same reference numerals inside have the same functions. Reference numeral 12 denotes a gate signal group, which is supplied to a switching element 21 of the converter section shown in FIG.

In FIG. 5, reference numeral 21 denotes a converter unit using a semiconductor switching element; 22, 23, and 24 AC power supplies for each of three phases; 25, 26, and 27 reactors; 28, a DC voltage source; Is the direct current, 31, 32, and 33 are the alternating currents of each phase,
104 is an AC line voltage of the converter unit, 105 is a line voltage of the AC power supply, and the semiconductor switching elements constituting the converter unit 21 are turned on / off in a predetermined procedure, and the DC current 30 and the AC currents 31, 32 , 33 to a desired value.

The operation of the block diagram of FIG. 4 will be described. The difference between the command value 1 of the direct current and the feedback value 2 of the direct current is calculated and amplified by the error operational amplifier 4, and the output of the sine wave generator 6 is calculated. Is compared with the output of the triangular wave generator 8, and a signal indicating the magnitude is supplied to the gate signal generator 10. The gate signal generator 10 can be configured as shown in FIG.
Are turned on / off. FIG. 6 is a time chart showing the on / off operation of the element. In the figure, a1 is the output 102 of the triangular wave generator 8 of FIG.
2 and a3 are one input 101R, 101S of the comparator 9 of FIG.
(B) and (c) are outputs 103R and 10R of the comparator 9, respectively.
3S and (d) show respective waveforms of the AC side line voltage 104 of the converter section 21 in FIG.

[0005]

The conventional example shown in FIG. 4 has two problems. First, at the time of startup, the output of the error operational amplifier 4 usually starts from 0,
The output of the multiplier 5 becomes 0, the input of the gate signal generator becomes 1: 1 in duty, and as a result, the ratio of the short-circuit time of the converter unit 21 in FIG. Unnecessary current flows temporarily.

Second, the gain of the error operational amplifier 4 must be increased and the response time must be increased in order to reduce the effects of the first problem. Therefore, it is difficult to design a control system. There is a disadvantage that the control system tends to be unstable. The present invention has been made in view of the above points, and its purpose is to prevent unnecessary current from flowing at start-up, and to reduce the gain of the error operational amplifier,
It is an object of the present invention to provide a converter control method that does not require a very fast response time.

[0007]

Means for achieving the object is as follows. In FIG. 4 of a block diagram showing a configuration of a conventional control circuit, a circuit between an output of an error operational amplifier 4 and a multiplier 5 is provided. As shown in FIG. 1, a voltage correction circuit 7 is inserted. According to a first aspect of the present invention, there is provided a converter unit which is connected between a three-phase AC power supply and a DC voltage source and mainly converts AC into DC, and a deviation between a DC or AC current command value and a feedback value of the converter unit. An error operational amplifier for amplifying the three-phase AC power supply, a sine wave generator synchronized with the three-phase AC power supply, a triangular wave generator, a comparator, a voltage correction circuit, and a multiplier, the output of the error operational amplifier and the voltage The output of the triangular wave generator is compared with a value obtained by multiplying the output of the sine wave generator by the result of addition and the output of the triangular wave generator. In a control method of a converter device that turns on and off a switching element constituting a unit, an output of the voltage correction circuit is proportional to a value obtained by dividing a voltage of the three-phase AC power supply by a voltage of the DC voltage source. Those were Unishi.

According to a second aspect of the present invention, there is provided a converter connected between a three-phase AC power supply and a DC voltage source for mainly converting AC to DC, a command value and a feedback value of an instantaneous AC current of the converter. An error operational amplifier for amplifying the deviation of the signal, a triangular wave generator, a comparator, and a voltage correction circuit, wherein the value obtained by adding the output of the error operational amplifier and the output of the voltage correction circuit and the triangular wave In the control method of the converter device, in which the output of the generator is compared with the output of the comparator, and the result of the comparison is used to turn on and off the switching element constituting the converter, the output of the voltage correction circuit is the three-phase AC. The instantaneous voltage of the power supply is proportional to a value obtained by dividing the voltage of the DC voltage source.

[0009]

The operation of the present invention will be described with reference to the drawings. FIG.
FIG. 2 is a block diagram showing an embodiment of the control circuit of the present invention. 7, reference numeral 7 denotes a voltage correction circuit. Other 1-6,8-
13, 101 to 103 have the same functions as those in FIG. 4 showing the configuration of the conventional control circuit, and the details thereof are as described above.

The voltage correction circuit 7 is configured such that when the output of the error operation amplification circuit 4 is 0, the fundamental wave component current flowing through the converter 21 shown in FIG. 5 becomes 0. More specifically, the relationship between the inputs 101 and 102 of the comparator 9 and the output 103 of the comparator 9 in FIG. 1 and the AC line voltage of the converter section 21 in FIG. 5 is as shown in a time chart shown in FIG. Now, if the peak values of the voltages of the input signals 101 and 102 of the comparator 9 in FIG. 1 are respectively vs and vt, and if vs <vt, the AC line voltage Vac and the DC voltage Vdc of the converter unit 21 in FIG. Is as shown in the following equation. Here, k is a constant.

Vac / Vdc = k · vs / vt (1)

That is, if the Vac of the equation (1) and the line voltage 105 of the AC power supply shown in FIG. 5 are made equal, the voltage relationship is balanced, so that the fundamental wave component becomes 0, and the triangular wave generator 8 shown in FIG. Only harmonic components related to the frequency of Therefore,
When the output of the error operational amplifier 4 in FIG. 1 is 0, the product of the input 106 of the multiplier 5 in FIG. 1 and the output of the sine wave generator 6 becomes a value corresponding to vs in the above equation (1). Then, the voltage correction circuit 7 may be configured. This can be described by the following mathematical expressions. The following equation is obtained by modifying the equation (1).

Vs = (Vac / Vdc) · (vt / k) (2)

Assuming that the peak value of the voltage at the input 106 of the multiplier 5 is vb and the peak value of the output voltage of the sine wave generator 6 is vso, vs is expressed by the following equation.

VS = vb · vso (3)

Equation (4) is obtained from equations (2) and (3).

Vb = (Vac / Vdc) · (vt / vso) · (1 / k) (4)

That is, the configuration may be such as to realize the expression (4).

[0019]

FIG. 1 is a block diagram showing an embodiment of the present invention, the details of which are as described in the operation thereof. FIG. 2 is a block diagram illustrating the voltage correction circuit 7 of the present invention in detail. 1, reference numerals 41 and 42 denote voltage generators for generating values proportional to the peak value vt of the output voltage of the triangular wave generator 8 and the peak value vso of the output voltage of the sine wave generator 6, respectively, and 44 and 45, respectively. , 46 is a divider, 48 is a multiplier,
47 is an adder, 43 is a voltage generator for generating a value corresponding to k in the equation (1), 109 and 110 are the peak value Va of the line voltage 105 of the AC power supply and the voltage of the DC power supply 28 shown in FIG. These are signals having values proportional to Vdc.

Assuming that the voltage of the output 111 of the divider 46 is vc, when observing the flow of each block in FIG. 2, it is apparent that the following equation is obtained.

Vc = (Va / Vdc) · (vt / vso) · (1 / k) (5)

Where the value of Va vs. signal 109 and the value of Vdc vs. signal
The conversion ratio between the value of 110 and the output value of the voltage generator 41 and the output value of the voltage generator 42 and the output value of the voltage generator 42 are also equal to each other. Comparator 9 of FIG.
If the value of the output 108 of the error operational amplifier 4 is represented by ve, the peak value vs of the voltage of one input 101 is expressed by the following equation from FIGS.

Vs = vb · vso = (ve + vc) · vso (6)

That is, when the value v e of the output 108 of the error operational amplifier 4 is 0, v b = v c.
Since the right side of the equation (5) coincides, it is obvious that the block diagram shown in FIG. 2 realizes the equation (4).

1 and 2 have been described as the DC current command value and the DC current feedback value, respectively. However, the effective value or instantaneous value command value of the AC current and the feedback value of the AC current may also be used. Naturally, a similar effect can be obtained.

FIG. 3 is a block diagram showing another embodiment of the control circuit of the present invention. In the figure, components having the same reference numerals as those in FIG. 1 have the same functions, and the details thereof are as described above.
In the figure, 14R, 14S and 14T are command values of the instantaneous AC current values indicated by 31, 32 and 33 in FIG. 5, respectively, and 15R, 15S and 15T are their feedback values, respectively. 14R, 14S, 14T above
Although there are various possible means for generating, the DC current command value shown in FIG. 1 is obtained by multiplying the output of the sine wave generator shown in FIG.

The detailed configuration of the voltage correction circuit 7 shown in FIG. 3 is almost the same as that of FIG. 1 as in FIG. 2, but the only difference is that the signal 109 in FIG. In contrast to the peak value of the line voltage 105 of the power supply, here, the instantaneous voltage of any one of the AC power supplies 22, 23, and 24 shown in FIG. 5 is used. Accordingly, the input 111 shown in FIG. 2 is steadily DC in the former case, and has an AC waveform similar to the signal 109 here. Therefore, when the output of the error operational amplifier 4 shown in FIG. 3 is 0, the operating point of the comparator shown by 9 in FIG. 3 is determined by the AC waveform of the input 111, and the value is determined by the signal 101R shown in FIG. , 101S, 101T. A feature of the other embodiment of the present invention is that, since the instantaneous current on the AC side of the converter is directly controlled, the current waveform becomes a good sine wave even when the power supply voltage waveform is distorted.

[0028]

As described above, according to the present invention, since the operating point of the control system at the time of starting the converter is determined from its AC voltage and DC voltage, no unnecessary current is generated. Also, since the operating point of the control system is roughly determined irrespective of the current command value, the followability to the current command is good, and the gain of the error operational amplifier can be reduced, so that the stability is improved.
The practical effect is extremely large. Further, by directly controlling the instantaneous current on the AC side of the converter, the current waveform becomes a good sine wave even if the power supply voltage waveform is distorted.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a voltage correction circuit according to the present invention.

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

FIG. 4 is a block diagram illustrating a configuration of a conventional control circuit.

FIG. 5 is an explanatory diagram showing a main circuit of the converter.

FIG. 6 is a time chart showing an on / off operation of an element.

[Explanation of symbols]

 Reference Signs List 1 DC current command value 2 DC current feedback value 3 Adder 4 Error operational amplifier 5 Multiplier 6 Sine wave generator 7 Voltage correction circuit 8 Triangular wave generator 9 Comparator 10 Gate signal generator 11R Synchronous signal 12 Gate signal group 14R Command value of instantaneous AC current value 15R Feedback value of instantaneous AC current value 21 Converter section 22 AC power supply 23 AC power supply 24 AC power supply 25 Reactor 26 Reactor 27 Reactor 28 DC voltage source 30 DC current 31 AC current 32 AC current 33 AC current 41 Voltage generator 42 Voltage generator 43 Voltage generator 44 Divider 45 Divider 46 Divider 47 Adder 48 Multiplier 101 Comparator input signal 102 Comparator input signal 103 Comparator output signal 104 AC line voltage 105 Line voltage

Claims (2)

(57) [Claims] 1. A converter connected between a three-phase AC power supply and a DC voltage source for mainly converting AC to DC, and an error for amplifying a deviation between a command value and a feedback value of the DC or AC current of the converter. An operational amplifier, a sine wave generator synchronized with the three-phase AC power supply, a triangular wave generator,
A comparator, a voltage correction circuit, and a multiplier, the output of the error operational amplifier and the output of the voltage correction circuit are added,
Further, a value obtained by multiplying the result of the addition by the output of the sine wave generator and the output of the triangular wave generator are compared by the comparator, and the comparison result is used to turn on / off a switching element constituting the converter unit. Wherein the output of the voltage correction circuit is proportional to a voltage obtained by dividing the voltage of the three-phase AC power supply by the voltage of the DC voltage source. Control method. 2. A converter connected between a three-phase AC power supply and a DC voltage source for mainly converting AC to DC, and an error calculation for amplifying a deviation between a command value and a feedback value of an instantaneous AC current of the converter. An amplifier, a triangular wave generator, a comparator, and a voltage correction circuit, wherein the value obtained by adding the output of the error operational amplifier and the output of the voltage correction circuit and the output of the triangular wave generator are In the control method of the converter device, in which a comparison is made by a comparator, and a switching element constituting the converter unit is turned on and off based on a result of the comparison, an output of the voltage correction circuit is an instantaneous voltage of the three-phase AC power supply. A method for controlling a converter device, wherein the value is proportional to a value divided by a voltage of a voltage source.