JP3272495B2 - Power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter for converting power between an AC power supply and a DC load.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a configuration diagram showing a conventional power conversion device disclosed in Japanese Patent Application Publication No. H10-207, in which reference numeral 1 denotes an AC power supply; Is converted to DC power and supplied to the DC load 9, and the DC power regenerated from the DC load 9 is converted to AC power and regenerated to the AC power supply 1.
The WM converter 6 is connected in parallel with the PWM converter 5 via a DC reactor 7 connected to one end on the DC output side,
A rectifier that converts AC power supplied from the AC power supply 1 into DC power and supplies the DC power to a DC load 9, 7 is a DC reactor,
Reference numeral 8 denotes a smoothing capacitor connected between the DC output terminals of the PWM converter 5, and reference numeral 9 denotes a DC load such as an inverter.

Next, the operation will be described. The power converter includes a power running operation in which the AC power supplied from the AC power supply 1 is converted into DC power and supplied to the DC load 9, and a DC power recovered from the DC load 9 is converted into AC power and the AC power The regenerative operation of regenerating to 1 is performed. First, the case of performing the power running operation will be described.

First, during a power running operation, a control unit (not shown) sends P
By controlling the WM converter 5, the AC power supplied from the AC power supply 1 is converted into DC power and supplied to the DC load 9. Supply according to capacity. That is, when the capacity of the DC load 9 increases, the amount of DC power to be supplied is increased in order to avoid a shortage of power supply, and when the capacity of the DC load 9 decreases, the supplied DC power becomes excessive. The amount of DC power to be supplied is reduced in order to avoid the situation.

During power running operation, the DC load 9
Therefore, the PWM converter 5 controls the DC power so that the DC voltage Vdc applied to the DC load 9 (equivalent to the DC voltage applied to the smoothing capacitor 8) does not fluctuate. In order to supply the DC load 9, the DC voltage applied to the DC load 9 operates so that the value Vdc of the DC voltage matches the predetermined voltage value Vdc * that is the rated voltage of the DC load 9. Therefore, the value of the DC voltage Vdc applied to the smoothing capacitor 8 fluctuates when the capacity of the DC load 9 fluctuates (when the capacity of the DC load 9 increases, the DC load 9 is smoothed to compensate for the shortage of power supply). When the shortage is received from the capacitor 8, the DC voltage Vdc applied to the smoothing capacitor 8 decreases). When the control unit (not shown) adjusts the difference between the DC voltage value Vdc and the predetermined voltage value Vdc *. PWM
Since the converter 5 is controlled, the value of the DC voltage Vdc matches the predetermined voltage value Vdc *.

However, it goes without saying that the PWM converter 5
In the case where the capacity of the DC load 9 is increased more than necessary, the DC power exceeding the limit is not supplied and the PWM converter 5 becomes overloaded. And the value Vdc of the DC voltage applied to the smoothing capacitor 8 starts to decrease.

The rectifier 6 in this conventional example is provided to avoid such an overload, and operates only when the PWM converter 5 is overloaded. That is, the value Vdd of the DC output voltage at the rectifier 6 is equal to the predetermined voltage value Vdd.
dc * (set by AC power supply 1 voltage fluctuation
Since the voltage is set lower than the value when the voltage drops within the allowable range), the diode element in the rectifier 6 is in a reverse bias state and the power running operation is performed in a normal state where the overload does not occur in the PWM converter 5. However, when the value Vdc of the DC voltage applied to the smoothing capacitor 8 decreases and becomes lower than the value Vdc of the DC output voltage in the rectifier 6, the reverse bias state is released, and the power supply operation is performed. Become. As a result, overload is avoided, and the value Vd of the DC voltage applied to the smoothing capacitor 8 is reduced.
c rises and becomes equal to the predetermined voltage value Vdc *.

On the other hand, in the regenerative operation, the DC load 9 regenerates the DC power, so that the value Vdc of the DC voltage applied to the smoothing capacitor 8 increases. Similarly, the PWM converter 5 is controlled so that the DC voltage value Vdc matches the predetermined voltage value Vdc *, and the PWM converter 5 converts the DC power regenerated by the DC load 9 into AC power, and To regenerate.

As a power conversion device for converting power between an AC power supply and a DC load, one disclosed in Japanese Patent Application Laid-Open No. 59-70185 (FIGS. 20 and 21) besides the above-mentioned conventional example. is there. In the figure, 10 is a high-speed fuse, 11
Is a switch, and 12 is a current limiting resistor for initial charging.

[0010]

Since the conventional power converter is configured as described above, when an overload occurs in the PWM converter 5, the rectifier 6 starts power running operation.
Although the power equal to or larger than the capacity of the PWM converter 5 can be supplied to the DC load 9, the value of the DC voltage V
There is a problem that the operation of the DC load 9 is hindered because the dc drops sharply. When an overload occurs, the PWM
Since the converter 5 is already carrying the maximum rated current,
The current cannot be increased due to the adjustment of the reactive power,
There was a problem that the reactive power could not be adjusted substantially. In addition, the rectifier 6 performs the power running operation only when the overload occurs in the PWM converter 5 and does not perform the power running operation in the normal time when the overload does not occur. All the power must be converted and supplied, and there is a problem that the capacity of the PWM converter 5 increases. Further, when the duration of the overload is relatively long, a harmonic current flows through the rectifier 6, so that the harmonic current flows to the AC power supply 1 and causes various problems in the power system. there were.

The invention of claim 1 has been made in order to solve the above-mentioned problems, and it is possible to prevent the DC voltage value Vdc from sharply lowering even if an overload occurs. The reactive power can be adjusted, and P
It is an object to obtain a power converter that can reduce the capacity of the WM converter 5.

According to the second and third aspects of the present invention, even when the DC voltage value Vdc fluctuates greatly due to load fluctuations or the like, the capacity of power conversion by the power running operation of the PWM converter 5 is reduced as much as possible. It is an object to obtain a power converter that can reduce the capacity of the converter 5.

A fourth object of the present invention is to provide a power converter capable of performing a stable power conversion even if the AC voltage on the primary side of the rectifier 6 fluctuates.

A fifth object of the present invention is to provide a power converter capable of performing stable power conversion by changing a predetermined voltage Vdc * in inverse proportion to a value of a current flowing through the rectifier 6.

A further object of the present invention is to provide a power converter capable of preventing a harmonic current generated from a rectifier 6 from flowing out to an AC power supply 1.

A seventh object of the present invention is to provide a power converter capable of limiting the rate of change of current when controlling the PWM converter 5 and reducing the harmonic current. .

It is an object of the present invention to provide a power converter capable of reducing a harmonic current contained in a circulating current.

The object of the ninth, tenth and twelfth aspects of the present invention is to provide a power converter having the same object as the first aspect of the present invention.

Another object of the present invention is to provide a power converter capable of controlling reactive power even with a rectifier.

[0020]

According to a first aspect of the present invention, there is provided a power converter for smoothing a value of a DC output voltage in a rectifier.
A predetermined value that matches the DC voltage value to be applied to the capacitor
Set the voltage to the value of AC power supplied from the AC power supply.
While supplying the converted DC power to the DC load,
DC power to be applied to the smoothing capacitor due to load fluctuation
If the voltage value does not match the predetermined voltage value, the value of the DC voltage
And the PWM converter according to the deviation between the predetermined voltage value and
DC power converted from AC power supplied from AC power supply
It is provided with a control unit for supplying a DC load.

According to a second aspect of the present invention, there is provided a power conversion apparatus which obtains a command value for matching a DC voltage value applied to a smoothing capacitor with a predetermined voltage value from a deviation between the DC voltage value and the predetermined voltage value. The PWM converter is controlled according to the deviation between the command value and the current value flowing through the rectifier.

According to a third aspect of the present invention, there is provided a power converter wherein upper and lower limits of a deviation between a command value and a current value flowing through the rectifier are set based on a current value flowing through the rectifier.

According to a fourth aspect of the present invention, there is provided a power converter, wherein a predetermined voltage value is changed in proportion to a change in an AC voltage on the primary side of a rectifier.

According to a fifth aspect of the present invention, in the power converter , a predetermined voltage value is changed so as to subtract an amount proportional to a current value flowing through the rectifier.

[0025] The power converter according to the invention of claim 6 is characterized in that P
A transformer is provided on the primary side of the WM converter and the rectifier.

According to a seventh aspect of the present invention, the power converter
At least one of an AC reactor and a transformer is provided on the primary side of the WM converter.

[0027] The power converter according to the invention of claim 8 reduces the harmonic current contained in the circulating current.
Means are provided .

According to a ninth aspect of the present invention, in the power converter, the rectifier includes a diode element.

The power converter according to the invention of claim 10 is
The rectifier is constituted by a thyristor element.

The power converter according to the invention of claim 11 is:
The rectifier comprises a gate turn-off thyristor element.

A power converter according to a twelfth aspect of the present invention
The DC reactor is composed of a superconducting coil.

A power converter according to a thirteenth aspect of the present invention is
This is a multi-phase PWM converter and rectifier.

[0033]

In the power converter according to the first aspect of the present invention, by setting the value of the DC output voltage of the rectifier to a predetermined voltage value, the rectifier performs power running operation in a normal state where the PWM converter is not overloaded. .

The power converter according to the second aspect of the present invention
A command value for matching the value of the DC voltage applied to the smoothing capacitor with the predetermined voltage value is obtained from the deviation between the DC voltage value and the predetermined voltage value, and the command value is determined according to the deviation between the command value and the current value flowing through the rectifier. By controlling the PWM converter, the capacity of the power conversion performed by the PWM converter when the value of the DC voltage greatly fluctuates due to load fluctuation or the like is limited.

According to the third aspect of the present invention,
By setting the upper and lower limits of the difference between the command value and the current value flowing through the rectifier based on the current value flowing through the rectifier, the PWM converter performs the operation when the DC voltage value greatly fluctuates due to load fluctuation or the like. Power conversion capacity is limited.

The power converter according to the invention of claim 4 is:
By changing the predetermined voltage value in proportion to the change in the AC voltage on the primary side of the rectifier, stable power conversion can be performed even if the AC voltage on the primary side of the PWM converter fluctuates. Become like

According to a fifth aspect of the present invention, there is provided a power converter,
By changing the predetermined voltage value so as to subtract an amount proportional to the current value flowing through the rectifier, stable power conversion can be performed even if the value of the current flowing through the rectifier changes. Will be able to

The power converter according to the invention of claim 6 is:
The provision of the transformer on the primary side of the PWM converter and the rectifier prevents the harmonic current generated from the rectifier from flowing out to the AC power supply.

According to a seventh aspect of the present invention, there is provided a power converter,
By providing at least either the AC reactor or the transformer on the primary side of the PWM converter, the rate of change of the current when controlling the PWM converter is limited, and the harmonic current is reduced.

The power converter according to the invention of claim 8 is:
Low harmonic current reduces harmonic current contained in circulating current
By providing the reducing means, the harmonic current contained in the circulating current is reduced.

According to a ninth aspect of the present invention, a power converter
Since the rectifier is constituted by the diode element, the rectifier performs the power running operation at the normal time when the PWM converter is not overloaded, similarly to the first aspect of the present invention.

In the power converter according to the tenth aspect of the present invention, the rectifier is constituted by a thyristor element, so that the rectifier performs the power running operation in a normal time when the PWM converter is not overloaded, similarly to the first aspect of the present invention. become.

According to the eleventh aspect of the present invention, since the rectifier is constituted by a gate turn-off thyristor element, the rectifier can control the reactive power.

According to the twelfth aspect of the present invention, in the power converter, the DC reactor is constituted by a superconducting coil, so that the rectifier performs the power running operation at the normal time when the PWM converter is not overloaded, similarly to the first aspect of the invention. Will do it.

According to a thirteenth aspect of the present invention, the power converter has a multi-phase PWM converter and a rectifier.
The harmonic current contained in the circulating current is reduced.

[0046]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a power conversion device according to an embodiment of the present invention. In the figure, the same reference numerals as those in the related art denote the same or corresponding parts, and a description thereof will be omitted. Reference numeral 21 denotes a transformer connected to the primary side of the transformer 2 and the rectifier 6. Reference numeral 22 denotes a case where the PWM converter 5 or the rectifier 6 converts AC power into DC power and supplies the DC power to the DC load 9.
In order to make the value Vdc of the DC voltage applied to the smoothing capacitor 8 equal to the predetermined voltage value Vdc *, a control unit that controls the PWM converter 5 according to the deviation between the value Vdc of the DC voltage and the predetermined voltage value Vdc *. is there.

Reference numeral 23 denotes an AC voltage VS1 on the secondary side of the transformer 2.
, A phase lock loop circuit (hereinafter, referred to as a PLL circuit) 25 for detecting the phase θ of the AC voltage VS1 in order to synchronize with the AC voltage VS1.
Are alternating current ICs (Iu, Iu) input to the PWM converter 5.
v, Iw), and 26 is an alternating current IC (Iu, Iv, Iw) detected by the current detection circuit 25.
w) is a three-phase / two-phase converter for converting a current Iq having the same phase component as the phase θ detected by the PLL circuit 24 and a current Id having a phase difference component of 90 °.

Reference numeral 27 denotes a reference voltage setting device for setting a predetermined voltage value Vdc *, and reference numeral 28 denotes a value for subtracting the value Vdc of the DC voltage applied to the smoothing capacitor 8 from the predetermined voltage value Vdc * set by the reference voltage setting device 27. A subtractor 29 is a voltage controller that outputs a current command value Iq * such that the subtraction result of the subtracter 28 becomes zero, and 30 is a 3-phase / 2-phase current command value Iq * output to the voltage controller 29. A subtractor 31 subtracts the current Iq converted by the converter 26. A voltage command value Vq * (a component in phase with the phase of the secondary side phase voltage of the transformer 2) is set so that the subtraction result of the subtractor 30 becomes zero. A current controller that outputs a voltage having the same.

Reference numeral 32 denotes the phase of the secondary side phase voltage of the transformer 2 and 9
A reference current setting device 33 for setting a current command value Id * having a phase difference component of 0 ° is converted from the current command value Id * output to the reference current setting device 32 to a three-phase / two-phase converter 26. A subtractor 34 for subtracting the current Id is a voltage command value Vd * (a voltage having a phase difference component of 90 ° with the phase of the secondary side phase voltage of the transformer 2) so that the subtraction result of the subtractor 33 becomes zero.
The current controller 35 outputs a PWM pulse SG to be given to the PWM converter 5 based on the phase θ detected by the PLL circuit 24 and the voltage command values Vq * and Vd * output to the current controllers 31 and 34. The generated PWM controller 36 amplifies the PWM pulse SG generated from the PWM controller 35 to turn on the self-extinguishing element constituting the PWM converter 5;
This is a gate amplifier that is turned off. Note that the DC reactor 7
Is constituted by a superconducting coil.

Next, the operation will be described. First, when the present invention is compared with the prior art, the most significant difference is that in the conventional example, the value Vdd of the DC output voltage in the rectifier 6 is set lower than the predetermined voltage value Vdc *, whereas In this case, the DC output voltage value Vdd in the rectifier 6 is set to the predetermined voltage value Vdc *.

Therefore, in the case of the conventional example, as described above, the rectifier 6 is required to reduce the DC voltage value Vdc due to the overload of the PWM converter 5 and the like, and become lower than the DC output voltage value Vdd in the rectifier 6. Although the power running operation was not started, that is, the power running operation was not started unless an overload occurred in the PWM converter 5, in the case of the present invention, the value of the DC output voltage Vdd in the rectifier 6 was changed to a predetermined voltage value Vdc.
Since it is set to *, the rectifier 6 does not become reverse-biased as in the conventional example in the normal state where the PWM converter 5 is not overloaded, and the rectifier 6 performs the power running operation even in the normal state where the PWM converter 5 is not overloaded. Become like In other words, since the rectifier 6 in the present invention is always forward biased except during power regeneration, the rectifier 6 always performs power running except during power regeneration.

On the other hand, as will be described in detail later, the PWM converter 5 operates normally when the DC voltage value Vdc applied to the smoothing capacitor 8 does not fluctuate with the predetermined voltage value Vdc * due to overload or the like. In, the power running operation is not performed, and the power running operation is performed only when the voltage fluctuates from the predetermined voltage value Vdc *.
However, the control of the reactive power is performed irrespective of the fluctuation of the load.

Hereinafter, the operation of the PWM converter 5 will be described by describing the operation of the control unit 22. First, the PLL circuit 24 detects the phase θ of the AC voltage VS1, and the three-phase / two-phase converter 26 detects the AC current IC (Iu, Iv, Iw) detected by the current detection circuit 25 by the PLL circuit 24. And a current Id having a phase difference component of 90 °. The conversion formula is as shown below. As can be seen from FIG. 2, the current Iq is a current component that generates active power, and the current Id is a current component that generates reactive power.

[0054]

(Equation 1)

When the value Vdc of the DC voltage applied to the smoothing capacitor 8 fluctuates, the predetermined voltage value Vd set in the reference voltage setting unit 27 to eliminate the fluctuation.
In order to supply the DC converter 5 with the DC power corresponding to the variation from dc * to the PWM converter 5, the subtracter 28 sets the predetermined voltage value Vdc *.
And the difference between the DC voltage value Vdc and the DC voltage value Vdc (the DC voltage value V
When dc matches voltage set value Vdc *, the deviation becomes zero, so that PWM converter 5 does not perform the power running operation.) Then, the voltage controller 29 outputs a current command value Iq * such that the subtraction result of the subtractor 28 becomes zero, and the subtractor 30 converts the current command value Iq * from the three-phase / two-phase converter 26.
Is subtracted from the current Iq, and the current controller 31 sets the voltage command value Vq * such that the subtraction result of the subtractor 30 becomes zero.
(A voltage having the same phase component as the phase of the secondary side phase voltage of the transformer 2).

Further, in order to supply the PWM converter 5 with reactive power corresponding to the current set value Id * previously set in the reference current setter 27, the subtracter 33 sets the current command value Id *.
The current controller 34 subtracts the current Id converted by the three-phase / two-phase converter 26 from d *, and the current controller 34 sets the voltage command value Vd * (the secondary side of the transformer 2) so that the subtraction result of the subtractor 33 becomes zero. (A voltage having a phase difference component of 90 ° with the phase of the phase voltage).

Then, the PWM controller 35 operates the PLL circuit 2
A PWM pulse SG to be applied to the PWM converter 5 is generated based on the phase θ detected by the controller 4 and the voltage command values Vq * and Vd * output to the current controllers 31 and 34. Specifically, the voltage command values Vq *, Vd * are subjected to the inverse transformation of the equation (1) to obtain three-phase phase voltage command values V * (Vu *, Vv *).
*, Vw *), and compares the phase voltage command value V * with the triangular wave carrier as shown in FIG. 3 to generate a PWM pulse SG. And, finally, the gate amplifier 36
The PWM converter 5 is controlled by amplifying the WM pulse SG and turning on and off the self-extinguishing element constituting the PWM converter 5.

Here, to summarize the description so far, the rectifier 6 always performs a power running operation, but the PWM converter 5 is applied to the smoothing capacitor 8 because the rectifier 6 becomes overloaded due to a change in load. The power running operation is performed only when the DC voltage value Vdc fluctuates. That is, the overload in the power converter is equivalent to the overload of the rectifier 6 (corresponding to the overload of the PWM converter 5 in the conventional example),
Since the M converter 5 only supplies power transiently to eliminate overload or the like, even when the power converter is overloaded, the PWM converter 5 has a margin for supplying extra power ( In the case of the conventional example, since the PWM converter 5 itself is overloaded, there is no extra power to supply power.) Therefore, even if the power converter is overloaded, the PWM converter 5 has an extra current. Can be output, so that the reactive power can be controlled even in such a case.

In the case of the conventional example, as described above, PW
When the M converter 5 is overloaded, the rectifier 6 performs the powering operation only when the value of the DC voltage Vdc applied to the smoothing capacitor 8 decreases and becomes lower than the value of the DC output voltage Vdd in the rectifier 6. Start, but in the case of the present invention,
When the rectifier 6 becomes overloaded and the value of the DC voltage Vdc applied to the smoothing capacitor 8 fluctuates, the PWM converter 5 immediately starts the power running operation. The phenomenon that the voltage value Vdc sharply decreases does not occur.

Further, in the case of the present invention, the rectifier 6 capable of easily increasing the capacity always performs the power running operation.
The PWM converter 5 only needs to be able to cope with the overload of the rectifier 6 and can have a smaller capacity than the conventional PWM converter 5.

Further, in the case of the present invention, since the rectifier 6 always performs the power running operation, as shown in FIG. 1, the circulating current I between the PWM converter 5, the rectifier 6 and the DC reactor 7 always flows.
dd flows, but even when the circulating current Idd contains a harmonic current, since the transformer 21 is connected to the primary side of the PWM converter 5 and the rectifier 6, the harmonic current is supplied to the AC power supply 1. Is prevented from flowing out.

Embodiment 2 FIG. FIG. 4 is a block diagram showing a power converter according to another embodiment of the present invention.
When controlling the PWM converter 5, a current command value Iq * that can make the DC voltage value Vdc applied to the smoothing capacitor 8 coincide with the predetermined voltage value Vdc * is set to 1.
c and a deviation between the predetermined voltage value Vdc * and the current command value Iq * and the circulating current Idd flowing through the rectifier 6.
A control unit for controlling the PWM converter 5 in accordance with the deviation of
Is a current detector that detects a circulating current Idd flowing through the rectifier 6, 43 is a diode rectifier that converts the circulating current Idd, which is an AC current, into a DC current, and 44 is a diode based on the current command value Iq * output to the voltage controller 29. A subtractor 45 subtracts the circulating current Idd converted by the rectifier 43, and 45 is an upper / lower limiter.

Next, the operation will be described. Example 1 above
In the above description, the PWM converter 5 immediately starts the power running operation when the DC voltage value Vdc fluctuates due to a load fluctuation or the like, and the PWM converter 5 suppresses such fluctuation. In P.2, even when the DC voltage value Vdc fluctuates greatly due to a load fluctuation or the like, PW
The purpose is to minimize the power conversion capacity due to the power running operation of the M converter 5 and to suppress such fluctuations by the rectifier 6 as much as possible.

That is, in the case of the first embodiment, the voltage controller 29
Was output directly to the subtractor 30 in the second embodiment, but in the second embodiment, the subtractor 44
The circulating current Idd converted into a DC current by the diode rectifier 43 is subtracted from the current command value Iq *,
The result of the subtraction is output to the subtractor 30. However, since the upper and lower limiters 45 set the upper and lower limits, if the subtraction result exceeds the upper or lower limit, the upper or lower limit is output to the subtractor 30. Let me.

As described above, since the circulating current Idd is subtracted from the current command value Iq *, it is equivalent to the power supply of the PWM converter 5 to the extent that the rectifier 6 alone cannot cover.

Embodiment 3 FIG. FIG. 5 is a block diagram showing a power converter according to another embodiment of the present invention.
6 is based on the value of the circulating current Idd flowing through the rectifier 6,
A control unit 47 is capable of setting upper and lower limits for the deviation between the current command value Iq * and the circulating current Idd.
When dd is equal to or less than a predetermined value, the upper limit of the variable upper and lower limiter 47 is set so that the output of the variable upper and lower limiter 47 becomes substantially zero (but a positive value) until the circulating current Idd becomes equal to or more than the predetermined value. When the DC voltage Vdc rises and the regenerative operation starts, the upper limit value generating circuit 49
This is a lower limit value generating circuit that opens the limiter value of the variable upper / lower limiter 47 to the negative side when dd decreases to a predetermined value or less.

Next, the operation will be described. Example 2 above
In the case where the circulating current Idd is hardly flowing, a value substantially equal to the current command value Idd * is output to the current controller 31 as in the first embodiment, so that the DC voltage Vd
Most of the power supply for eliminating the fluctuation of c is performed by the PWM converter 5. In the third embodiment, when the circulating current Idd hardly flows, the output of the variable upper and lower limiter 47 is substantially zero ( However, since the upper limit value of the variable upper / lower limiter 47 is set so as to be a positive value, the PWM
The converter 5 hardly supplies power, and the rectifier 6 supplies power. (Currently, even if the circulating current Idd hardly flows, if the DC load 9 is present, the circulating current Id
d flows continuously). Therefore,
According to the third embodiment, since the operation ratio of the PWM converter 5 is smaller than that of the second embodiment, the capacity of the PWM converter 5 can be further reduced.

Embodiment 4 FIG. In the above embodiment, as shown in FIG. 6, since the reference voltage setter 27 is constituted by a fixed setter 50, the predetermined voltage value Vdc * fluctuates in the AC voltage VS on the primary side of the rectifier 6. However, as shown in FIG. 7, the primary side AC voltage V
The predetermined voltage value Vdc * may be changed in proportion to the change of S.

In FIG. 7, reference numeral 51 denotes a voltage detector for detecting the AC voltage VS, and 52 denotes an AC voltage V on the primary side of the rectifier 6.
A reference voltage setting unit that changes the predetermined voltage value Vdc * in proportion to the variation of S, 53 is a gain, 54 is a subtractor for subtracting the output of the gain 53 from the AC voltage VS, 55 is a predetermined voltage value Vdc * and a subtractor 54 Are added.

Next, the operation will be described. First, before explaining FIG. 7, the following relationship is established between the AC voltage VS (the value of VS is the effective value of the line voltage) and the DC output voltage Vdd of the rectifier 6. Vdd = 1.35 × VS (2) In a normal state where no load fluctuation or the like occurs, the DC output voltage Vdd is between the DC voltage Vdc applied to the smoothing capacitor 8 and the predetermined voltage value Vdc *. The following relationship is established. Vdc * = Vdc = Vdd (3)

Accordingly, if the AC voltage VS does not fluctuate, the DC output voltage Vdd of the rectifier 6 is always constant according to the equation (2). If it fluctuates, the DC output voltage Vdd fluctuates according to the equation (2), so that the equation (3) is not satisfied (because the predetermined voltage value Vdc * is constant, the predetermined voltage value Vdc * and the DC output voltage Vdd are equal to one another). No longer)
The predetermined voltage value Vdc * is not an appropriate value in the control system, and the control system becomes unstable.

Therefore, in the fourth embodiment, the AC voltage VS
The specific voltage value Vdc * is changed in proportion to the variation of the AC voltage VS. Specifically, first, in order to detect the variation of the AC voltage VS, the subtractor 54 calculates the predetermined voltage value Vdc * from the AC voltage VS. The output of the gain 53 to which Vdc * has been input is subtracted. However, the gain 53 is initially adjusted so that the output of the subtractor 54 becomes zero in normal times when there is no change in the AC voltage VS. Then, in the adder 55, the subtractor 54
Is added to the predetermined voltage value Vdc * set in the setting device 50. As a result, a predetermined voltage value Vdc * proportional to the variation of the AC voltage VS is obtained, and the control system can be stabilized.

Embodiment 5 FIG. FIG. 8 is a block diagram showing a power converter according to another embodiment of the present invention.
6 is a gain for multiplying the circulating current Idd by a constant K, and 57 is a subtractor for subtracting the output of the gain 56 from the output of the reference voltage setting device 52.

Next, the operation will be described. First, when the DC voltage Vdc applied to the smoothing capacitor 8 changes due to a load change or the like, a deviation voltage occurs between the DC voltage Vdc and the DC output voltage Vdd of the rectifier 6, and as a result, the circulating current Idd changes. The rate of change of the circulating current Idd can be expressed as follows. di / dt = (Vdd-Vdc) / L2 (4) Further, a graph showing a relationship between the average value of the DC output voltage Vdd of the rectifier 6 and the circulating current Idd is as shown in FIG. FIG. 9 shows how the DC output voltage Vdd decreases in inverse proportion to the increase in the circulating current Idd. This is due to the effect of commutation overlap in the rectifier 6.

Therefore, the DC output voltage Vdd and the circulating current I
Unless the predetermined voltage Vdc * is changed in consideration of the relationship of dd, equations (2) and (3) are not actually satisfied, and a stable control system cannot be obtained. Therefore, in the fifth embodiment,
The subtractor 57 subtracts the output of the gain 56 for multiplying the constant K by inputting the circulating current Idd from the output of the reference voltage setter 52. As a result, a more stable control system than that of the above embodiment can be obtained.

Embodiment 6 FIG. In the above embodiment, the case where both the transformer 2 and the AC reactor 4 are connected to the primary side of the PWM converter 5 has been described. For example, only the transformer 2 may be connected. That is, AC reactor 4
Is for limiting the rate of change of the current, but the rate of change of the current can also be limited by the leakage inductance of the transformer 2.

Embodiment 7 FIG. FIG. 10 is a block diagram showing a power converter according to another embodiment of the present invention. In the figure, reference numeral 58 denotes an active filter which is connected in parallel with the PWM converter 5 and reduces the harmonic current included in the circulating current Idd. (Harmonic current reduction means)
It is. As described above, when the duration of the overload is relatively long, a harmonic current is generated from the rectifier 6. However, when the active filter 58 is connected as shown in FIG. , The harmonic current can be canceled.

Embodiment 8 FIG. FIG. 11 shows a configuration in which the rectifier 6 in the above embodiment is configured using the diode element 6a, and the operation of the above embodiment can be obtained by this configuration. In addition, as shown in FIG. 12, the rectifier 6 may be multi-phase, and in this case, the harmonic current included in the circulating current Idd can be reduced.

Embodiment 9 FIG. In FIG. 13, the rectifier 6 in the above embodiment may be replaced by a thyristor rectifier 59 using a thyristor element 60, and the same effect as in the above embodiment can be obtained. Also, as shown in FIG.
The thyristor rectifier 59 may be multi-phased. In this case,
The harmonic current included in the circulating current Idd can be reduced.

FIG. 15 shows a control configuration in the case where the power converter is configured using a thyristor rectifier 59. In the figure, reference numeral 61 denotes a phase shifter for advancing the phase of the AC voltage VS by π / 2, and 62 denotes a phase shifter. A setting device for setting a reference value Vdd * of the DC output voltage Vdd of the thyristor rectifier 59; 63, a comparator for comparing the reference value Vdd * with the output of the phase shifter 61 to obtain a phase control angle α; A gate logic 65 outputs a gate firing signal having a width of 120 ° based on the phase control angle α, and a gate amplifier 65 amplifies the output of the gate logic 64 and fires the thyristor element 60 of the thyristor rectifier 59.

Next, the operation will be described. First, after the phase shifter 61 advances the phase of the AC voltage VS by π / 2, the comparator 63 compares the reference value Vdd * with the output of the phase shifter 61 to obtain and output the phase control angle α. . Then, the gate logic 64 outputs a gate firing signal having a width of 120 ° based on the phase control angle α to control the gate timing of the thyristor element 60 in the thyristor rectifier 59. The output is amplified to fire the thyristor element 60 of the thyristor rectifier 59. Here, the following relationship is established between the AC voltage VS (the value of VS is the effective value of the line voltage), the DC output voltage Vdd of the thyristor rectifier 59, and the phase control angle α. Vdd = 1.35 × VS × cosα (5) Vdd = 1.35 × VS × Vdd * / Vdd0 (6) where Vdd0 is the peak value of the sine wave in FIG.

Embodiment 10 FIG. FIG. 17 shows that the rectifier 6 in the above embodiment may be replaced by a gate turn-off thyristor rectifier 66 constituted by using a gate turn-off thyristor element 68, whereby the same effect as in the above-described embodiment can be obtained and the gate turn-off thyristor rectifier can be obtained. 6
6 itself can control the reactive power.

In the case of the ninth embodiment, the thyristor element 60
, The phase control angle α is positive (α> 0), that is, the phase control is delayed. However, when the gate turn-off thyristor element 68 is used as in the tenth embodiment, the self-extinguishing can be performed. Therefore, the phase control angle α is negative (α <0), that is, leading phase control can be performed, and therefore, the reactive power can be controlled by the gate turn-off thyristor rectifier 66 itself.

[0084]

As described above, according to the first aspect of the present invention, the value of the DC output voltage in the rectifier is reduced by the smoothing capacitor.
Set to a predetermined voltage value that matches the DC voltage value to be applied to the
The AC power supplied from the AC power supply
Supply DC power to DC load and change DC load
The value of the DC voltage to be applied to the smoothing capacitor
If the voltage does not match the constant voltage value, the DC voltage value and the predetermined voltage
By controlling the PWM converter according to the deviation of the value,
DC power obtained by converting AC power supplied from
Since the control unit for supplying the power supply is provided , the rectifier performs the power running operation in the normal time when the PWM converter is not overloaded, while the PWM converter operates immediately when the value of the DC voltage applied to the smoothing capacitor fluctuates. Is started, there is an effect that the DC voltage can be prevented from sharply dropping even if an overload occurs in the rectifier. Further, since the PWM converter only performs transiently power running when the DC voltage varies, with overload can control the reactive power be generated in the rectifier, a capacity of PWM converter There are effects such as reduction.

According to the second aspect of the present invention, a command value for matching the value of the DC voltage applied to the smoothing capacitor with the predetermined voltage value is obtained from the deviation between the DC voltage value and the predetermined voltage value. Since the PWM converter is configured to be controlled according to the difference between the current value and the current value flowing through the rectifier,
The PWM converter supplies power only to the extent that the rectifier cannot provide enough power. Therefore, there is an effect that the capacity of the PWM converter can be reduced.

According to the third aspect of the present invention, the upper and lower limits of the deviation between the command value and the current flowing through the rectifier are set based on the value of the current flowing through the rectifier. Further, the operation ratio of the PWM converter is reduced, and as a result, there is an effect that the capacity of the PWM converter can be further reduced.

According to the fourth aspect of the present invention, since the predetermined voltage value is changed in proportion to the fluctuation of the AC voltage on the primary side of the PWM converter, even if the AC voltage fluctuates,
There are effects such as stable power conversion.

According to the fifth aspect of the present invention, since the predetermined voltage value is changed so as to subtract an amount proportional to the current value flowing through the rectifier, even if the value of the current flowing through the rectifier changes, There are effects such as stable power conversion.

According to the sixth aspect of the present invention, since the transformer is provided on the primary side of the PWM converter and the rectifier, it is possible to prevent the harmonic current generated from the rectifier from flowing out to the AC power supply. And so on.

According to the seventh aspect of the present invention, at least one of the AC reactor and the transformer is provided on the primary side of the PWM converter, so that when controlling the PWM converter, the rate of change of the current is reduced. And it is possible to reduce the harmonic current.

According to the invention of claim 8, there is provided a harmonic current reducing means for reducing a harmonic current included in the circulating current.
With such a configuration, harmonic currents included in the circulating current can be offset, and as a result, there is an effect that the harmonic current can be reduced.

According to the ninth aspect of the present invention, since the rectifier is formed of a diode element, the rectifier is formed by a P element as in the first aspect of the present invention.
The rectifier performs the power running operation at the normal time when the WM converter is not overloaded, and the same effect as the first aspect of the invention can be obtained.

According to the tenth aspect of the present invention, the rectifier is constituted by a thyristor element.
The rectifier performs the power running operation at the normal time when the PWM converter is not overloaded, and the same effect as the first aspect of the invention can be obtained.

According to the eleventh aspect of the present invention, since the rectifier is constituted by the gate turn-off thyristor element, there is an effect that the rectifier can control the reactive power.

According to the twelfth aspect of the present invention, since the DC reactor is constituted by a superconducting coil, the rectifier performs the power running operation in the normal state when the PWM converter is not overloaded, similarly to the first aspect of the invention. Thus, the same effect as the first aspect of the invention can be obtained.

According to the thirteenth aspect of the present invention, since the PWM converter and the rectifier are configured to have multiple phases, there is an effect that the harmonic current included in the circulating current can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a power conversion device according to an embodiment of the present invention.

FIG. 2 is a vector diagram showing an operation of the PWM converter.

FIG. 3 is a waveform chart for explaining the operation of the PWM controller 35;

FIG. 4 is a configuration diagram showing a power converter according to another embodiment of the present invention.

FIG. 5 is a configuration diagram showing a power conversion device according to another embodiment of the present invention.

FIG. 6 is a configuration diagram showing a reference voltage setting device 27.

FIG. 7 is a configuration diagram showing a power conversion device according to another embodiment of the present invention.

FIG. 8 is a configuration diagram showing a power conversion device according to another embodiment of the present invention.

FIG. 9 shows the DC output voltage Vdd of the rectifier and the circulating current Idd.
It is a graph which shows the relationship of.

FIG. 10 is a configuration diagram showing a power conversion device according to another embodiment of the present invention.

FIG. 11 is a configuration diagram showing a power converter according to another embodiment of the present invention.

FIG. 12 is a configuration diagram showing a power converter according to another embodiment of the present invention.

FIG. 13 is a configuration diagram showing a power conversion device according to another embodiment of the present invention.

FIG. 14 is a configuration diagram showing a power conversion device according to another embodiment of the present invention.

FIG. 15 is a configuration diagram showing a control configuration when the power conversion device is configured using a thyristor rectifier 59.

FIG. 16 is an explanatory diagram of FIG.

FIG. 17 is a configuration diagram showing a power conversion device according to another embodiment of the present invention.

FIG. 18 is a configuration diagram showing a power conversion device according to another embodiment of the present invention.

FIG. 19 is a configuration diagram showing a conventional power converter.

FIG. 20 is a configuration diagram showing a conventional power converter.

FIG. 21 is a configuration diagram showing a conventional power converter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 AC power supply 4 AC reactor 5 PWM converter 6 Rectifier 6a Diode element 7 DC reactor 8 Smoothing capacitor 2, 21 Transformers 22, 41, 46 Control part 58 Active filter (harmonic current reduction means) 60 Thyristor element 67 Gate turn-off thyristor Element Vdc DC voltage value Vdc * Predetermined voltage value Vdd DC output voltage value

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/17 H02M 7/155

Claims (13)

(57) [Claims] 1. An AC power supply connected to an AC power supply.
The supplied AC power is converted to DC power and supplied to the DC load.
And the DC power regenerated from the DC load
PWM converter that converts AC power and regenerates the AC power
And via a DC reactor connected to the DC output side
Connected in parallel with the PWM converter and supplied from the AC power supply.
The supplied AC power is converted to DC power and supplied to the DC load.
Between the rectifier to be supplied and the DC output terminal of the PWM converter
Connected toCorresponding to the DC power supplied to the DC load
DC voltage is appliedAn electrode with a smoothing capacitor
In the force converter,The value of the DC output voltage at the rectifier is
A predetermined voltage value that matches the DC voltage value to be applied to the sensor
To change the AC power supplied from the AC power supply.
While supplying the converted DC power to the DC load, The DC load fluctuates and is applied to the smoothing capacitor.
DC voltage value to be inconsistent with the predetermined voltage value
And a difference between the DC voltage value and the predetermined voltage value.
The PWM converter is controlled to be supplied from the AC power source.
DC power obtained by converting AC power is supplied to the DC load.
Equipped with a control unit A power converter characterized by the above-mentioned. 2. The control unit, when controlling the PWM converter, sends a command value that allows the value of the DC voltage applied to the smoothing capacitor to match the predetermined voltage value with the DC voltage value and the predetermined voltage value. From the difference between the command value and the current value flowing through the rectifier.
The power converter according to claim 1, wherein the M converter is controlled. 3. The electric power according to claim 2, wherein the control unit sets upper and lower limits of a deviation between the command value and a current value flowing through the rectifier based on a current value flowing through the rectifier. Conversion device. 4. The rectifier according to claim 1, wherein the control unit changes the predetermined voltage value in proportion to a change in an AC voltage on a primary side of the rectifier.
Item 3. The power converter according to item 1. 5. The control unit according to claim 1, wherein the control unit changes the predetermined voltage value so as to subtract an amount proportional to a current value flowing through the rectifier. The power converter according to any one of the preceding claims. 6. A transformer is provided on a primary side of the PWM converter and the rectifier to prevent a circulating current flowing between the PWM converter, the rectifier and the DC reactor from flowing out to the AC power supply. The power converter according to any one of claims 1 to 5, characterized in that: 7. The power converter according to claim 1, wherein at least one of an AC reactor and a transformer is provided on a primary side of the PWM converter. . 8. The apparatus according to claim 1, further comprising a harmonic current reducing unit configured to reduce a harmonic current included in a circulating current flowing between the PWM converter, the rectifier, and the DC reactor. A power converter according to any one of the preceding claims. 9. The power converter according to claim 1, wherein the rectifier comprises a diode element. 10. The power converter according to claim 1, wherein the rectifier comprises a thyristor element. 11. The power converter according to claim 1, wherein the rectifier comprises a gate turn-off thyristor element. 12. The power converter according to claim 1, wherein said DC reactor is constituted by a superconducting coil. 13. The power converter according to claim 1, wherein the PWM converter and the rectifier are multi-phased.