JP2003088124A - Rectifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain further improvement in a harmonic distortion reducing function by a sufficiently practical structure without requiring addition of a DC reactor, and attain miniaturization of the whole device. SOLUTION: A valley of DC voltage ripple outputted from a main three-phase full-wave rectifying circuit 5 is filled with the output of auxiliary three-phase full-wave rectifying circuits 7, 8, thus reducing the voltage ripple and the harmonic distortion. A transformer 6 outputs voltage based on a specific output voltage vector diagram, so that it becomes sufficient to use small capacity thereof. A voltage generating means 11 generates voltage so as to compensate for the voltage ripple included in the three-phase full-wave rectifying circuits 5, 7, 8, thus improving the harmonic distortion reducing function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifying device for supplying a load with DC power obtained by rectifying AC power from a three-phase AC power supply with a three-phase full-wave rectifying circuit and then smoothing it with a smoothing capacitor. is there.

[0002]

2. Description of the Related Art When converting a three-phase AC voltage into a DC voltage, a three-phase full-wave rectifying circuit composed of six rectifying elements is often used. FIG. 9 is a block diagram showing an example of a conventional rectifier using such a three-phase full-wave rectifier circuit.

In FIG. 9, a three-phase AC power supply 101 is a three-phase full-wave rectifier circuit 1 composed of six diodes 104 via a resistor 101 and a system inductance 103.
05 is connected to the input side. Three-phase full-wave rectifier circuit 10
A smoothing capacitor 107 is connected to the output side of 5, and a load 108 is connected in parallel with the smoothing capacitor 107. A DC reactor 106 is connected between the positive side (P side) terminals of the three-phase full-wave rectifier circuit 105 and the smoothing capacitor 107.

This three-phase full-wave rectifier circuit 105 rectifies the AC voltage from the power supply lines R, S, T of each phase of the three-phase AC power supply 101, and includes a ripple having a frequency 6 times the power supply frequency fs. The phase full-wave rectified voltage Vrec is output to the DC side. At this time, the rectified voltage Vrec has a ripple reduced by the DC reactor 106, and the smoothing capacitor 107
Is smoothed by and is supplied to the load 108.

FIG. 10 is a waveform diagram of the three-phase full-wave rectified voltage Vrec, that is, the six-phase rectified voltage Vrec, which includes a ripple having a frequency six times the power supply frequency fs. The average value Vdc of the 6-phase rectified voltage Vrec is the system inductance 1
When the overlapping angle due to the influence of 03 is θ0 and the effective voltage between system lines is VLL, it is expressed by the following equation (1). Further, the minimum value Vmin of the 6-phase rectified voltage Vrec is expressed by the equation (2). Therefore, the average values Vdc and Vmi are calculated from the equations (1) and (2).
The voltage difference ΔVdc with respect to n is expressed as in equation (3).

The DC voltage ripple effective value ΔVr is
It is expressed as in equation (4) by the triangular wave approximation with the amplitude of the difference voltage ΔVdc. Therefore, the DC voltage fluctuation rate due to the DC voltage ripple is expressed by the equation (5). At this time, if the value of θ0 is 15.3 °, the voltage fluctuation rate of the equation (5) is finally expressed as the equation (6).

[0007]

[Equation 1] Here, the above-mentioned DC voltage ripple effective value ΔVr is a harmonic voltage that oscillates in a cycle 6fs that is six times the power supply frequency fs of the three-phase AC power supply 101, and causes various troubles. Therefore, the DC reactor 106 is provided as a countermeasure against this harmonic. As another conventional device provided with other harmonics countermeasure means, there is, for example, one in which an 18-phase AC / DC converter is configured by using three 3-phase full-wave rectifier circuits (Japanese Patent Laid-Open No. 4-229077). ). FIG. 11 is a block diagram showing an example of a conventional rectifying device adopting the 18-phase AC / DC converter.

In FIG. 11, a main three-phase full-wave rectifier circuit 10 is shown.
5A is similar to the three-phase full-wave rectifier circuit 105 in FIG. 9, and is a power supply line R for each phase of the three-phase AC power supply 101.
The AC voltage from 1, S1, T1 is rectified. However, in this conventional device, the power lines R1, S1, T1 are
Voltages are equal and phase is + 40 ° and -40 ° respectively
Two transformers 109 that output 6-phase alternating current,
The primary side of 111 is connected. The secondary sides of these transformers 109 and 111 are connected to lines R2 and S, respectively.
It is connected to each input side of the first auxiliary three-phase full-wave rectifying circuit 110 and the second auxiliary three-phase full-wave rectifying circuit 112 via 2, T2 and lines R3, S3, T3. The output sides of these auxiliary three-phase full-wave rectifier circuits 110 and 112 are connected to the main 3
They are connected in parallel to the output side of the phase full-wave rectifier circuit 105A, that is, the DC lines P and N, respectively.

FIG. 12 is an output voltage vector diagram of the transformers 109 and 111. The vertices R1, S1, T1 of the equilateral triangle in this figure correspond to the power supply lines R1, S1, T1, and a voltage having a vector corresponding to each side of the equilateral triangle is supplied to the main three-phase full-wave rectifier circuit 105A. Is entered.
Further, from the transformer 109, a voltage having a vector corresponding to each side of the equilateral triangles R2, S2, T2 obtained by rotating the equilateral triangles R1, S1, T1 by + 40 ° is supplied to the auxiliary three-phase full-wave rectification circuit 110. It is output to. Similarly, the transformer 11
From 1, a voltage having a vector corresponding to each side of the equilateral triangles R3, S3, T3 obtained by rotating the equilateral triangles R1, S1, T1 by -40 ° is output to the auxiliary three-phase full-wave rectification circuit 112. To be done.

In the rectifier shown in FIG. 11, the auxiliary three-phase full-wave rectifier circuits 110, 1 are filled so as to fill the valleys of the DC voltage ripple output from the main three-phase full-wave rectifier circuit 105A.
Since 12 outputs, the voltage ripple can be reduced and the generation of harmonics can be reduced.

FIG. 13 is a waveform diagram showing a voltage waveform that has been rectified by 18 phases as described above. First, the voltages for 18-phase rectification are V1, V2, and V3, and these are given in (7)-
It is defined by the equation (9). Here, if the phase θ2 is the phase when the average value of V1 and V2 becomes equal to V3, this θ2
Can be calculated by the equation (10). Also, 18
The average value Vdc of the phase-rectified voltage can be calculated by the equation (11). However, A1 and A2 in the equation (11) are defined by the equations (12) and (13), and (12) and (1
F1 and f2 in the equation (3) are defined by the equations (14) and (15). Then, by substituting the equations (12) to (15) into the equation (11) and rearranging, the equation (16) is obtained.

[0012]

[Equation 2] The minimum value Vmin of the 18-phase rectified voltage Vrec is expressed by the following equation (17). Therefore, from equations (16) and (17), the difference voltage ΔVdc between the average value Vdc and the minimum value Vmin is given by equation (18). The DC voltage ripple effective value ΔVr is represented by the equation (19) by the triangular wave approximation using the difference voltage ΔVdc as the amplitude. Therefore, the DC voltage fluctuation rate due to the DC voltage ripple is expressed as in equation (20).

[0013]

[Equation 3] Here, if the DC voltage ripple due to 18-phase rectification is approximated to be about one-third of the DC voltage ripple due to 6-phase rectification, the overlap angle increases about three times. Then, the change rate of the overlap angle with respect to the change rate of the system inductance L is √ (L
/ L0) (L0 is the rated value), the overlap angle increases to √3 times when the system inductance is tripled.
Therefore, when the overlapping angle during 6-phase rectification is 15.3 °, the overlapping angle during 18-phase rectification is given by equation (21). At this time, θ1, θ2 and θ3 are (22)
It is represented by equation (24). And (22)-(24)
Substituting the equation into the equation (20), the DC voltage fluctuation rate during 18-phase rectification is given by the equation (25). As is clear from a comparison between the equations (25) and (6), the DC voltage fluctuation during 18-phase rectification is reduced to about one-third that during 6-phase rectification. Here, the system line voltage effective value VLL is 200 [V]
Then, from equation (25), the DC voltage ripple effective value is given by equation (26).

[0014]

[Equation 4]

[0015]

As described above, the rectifier of FIG. 11 that performs 18-phase rectification has a higher harmonic distortion than the rectifier of FIG. 9 that performs 6-phase rectification and has the DC reactor 106. Although it is possible to reduce the harmonic distortion, further improvement is required for the harmonic distortion reducing function. Therefore, in the rectifier of FIG. 11, an example in which the DC reactor 106 of the rectifier of FIG. 9 is not provided is shown. However, in some cases, the same rectifier of the rectifier of FIG. The harmonic distortion reduction function may be improved.

However, in the DC reactor, since all the passing current becomes the exciting current of the iron core, magnetic saturation easily occurs, and there is a problem that the iron core cross-sectional area must be increased in order to avoid this. However, if the iron core cross-sectional area is increased, the entire apparatus becomes large and the cost is increased, so that it is usual to dare not to ensure a sufficient cross-sectional area. On the other hand, if the cross-sectional area of the iron core is limited, the iron core is magnetically saturated near the peak value of the current waveform, the current peak cannot be suppressed sufficiently, and it becomes difficult to sufficiently reduce the power supply harmonics. Therefore, in some cases, it is conceivable to increase the iron core cross-sectional area in consideration of the increase in the size of the entire device.However, with a configuration that simply increases the inductance value, the transient change of the input current becomes slow and the load changes suddenly. Correspondingly, the input current cannot be changed suddenly. Therefore, the voltage across the terminals of the smoothing capacitor fluctuates greatly, resulting in a loss of stability of the DC link voltage.

Further, as another measure for improving the harmonic distortion reducing function, for example, a switching circuit is provided between the positive side diode and the negative side diode (Japanese Patent Laid-Open No. 9-1824).
No. 41), or a configuration in which a chopper is inserted in the DC link section may be adopted. However, in the former case, the switching circuit is expensive, resulting in an increase in the cost of the entire device, and in the latter case,
It is necessary to increase the current capacity of the switching element, which causes another problem that the power loss in the switching element increases. That is, in any case, it was difficult to say that it has sufficient practicality.

Further, the configuration of FIG. 11 has a problem that the device is upsized. That is, in the case of the configuration of FIG.
It is necessary to output a voltage of the same magnitude as the three-phase AC voltage from the power supply 101 from the transformers 109 and 111, and the three three-phase full-wave rectification circuits 105A, 110, 112.
Are conducted evenly, so that the flowing current is also uniform.
Therefore, the current rectified via the transformers 109 and 111 is as large as two-thirds of the total, and the capacity of the transformer is inevitably large, and the miniaturization of the entire rectifying device is sufficiently achieved. Was difficult.

The present invention has been made in view of the above circumstances, and when three three-phase full-wave rectifier circuits are provided to perform 18-phase rectification, it is not necessary to add a DC reactor and is sufficiently practical. It is an object of the present invention to provide a rectifying device capable of further improving the harmonic distortion reducing function with a certain structure and also capable of reducing the size of the entire device.

[0020]

As a means for solving the above-mentioned problems, the invention according to claim 1 rectifies AC power from a three-phase AC power source by a three-phase full-wave rectifier circuit and smoothes it by a smoothing capacitor. The DC power obtained by the above is supplied to the load, and this three-phase full-wave rectifier circuit
One main three-phase full-wave rectifier circuit that directly inputs the AC power from the three-phase AC power supply, and the AC power from the three-phase AC power supply through a transformer and the output side of the main three-phase full-wave In the rectifying device, which is composed of first and second two auxiliary three-phase full-wave rectifier circuits connected in parallel with the output side of the rectifier circuit, the transformer is the main three-phase full-wave rectifier circuit. R1, S1, T1 to the power lines of each phase that are input by R1, S2, T2 and the power lines of the respective phases that the first and second auxiliary three-phase full-wave rectifier circuits input via the transformer. R3,
When S3, T3 and R1, S1, T1 are the vertices of an equilateral triangle in the voltage vector diagram, these arcs are on each arc R1S1, S1T1, T1R1 whose radius is the side length of this equilateral triangle. R3, S2, and
S3, T2, T3, R2 are arranged, and each vertex R1, S1,
T1 and each position S3, T2, T3, R on the arc opposite to this
A total of 6-phase AC power is output so that each straight line connecting 2, R3 and S2 is an output voltage vector, and further, the main 3-phase full-wave rectification circuit and the auxiliary 3-phase full-wave rectification circuit Voltage generating means connected between the output side and the smoothing capacitor and capable of generating an arbitrary voltage waveform, and by controlling this voltage generating means, compensation of the DC ripple component contained in the output of each rectifying circuit is performed. And a control means for performing the control.

According to a second aspect of the present invention, in the first aspect of the invention, the voltage generating means is composed of a capacitor and a plurality of switching elements, and the output voltage of the capacitor is varied by the PWM switching operation of these switching elements. A phase bridge circuit, wherein the control means includes a line voltage detection value of the three-phase AC power supply,
Control for inputting a detected value of current flowing from the phase full-wave rectifier circuit to the single-phase bridge circuit and a voltage detected value of the capacitor in the single-phase bridge circuit, and outputting a switching command signal for PWM controlling the switching element Circuit,
A gate drive circuit that outputs a gate signal to the switching element based on the input of the switching command signal.

According to a third aspect of the present invention, in the rectifier according to the second aspect, the control circuit outputs a ripple compensation pattern signal based on a deviation between the line voltage detection value and the command value of the three-phase AC power supply. A ripple compensation pattern generator, a current controller that outputs a current control signal based on a deviation between a detected value and a command value of a current flowing from the three-phase full-wave rectifier circuit into the single-phase bridge circuit, and the single-phase A capacitor voltage control unit that outputs a capacitor voltage control signal based on the deviation between the detected voltage value and the command value of the capacitor in the bridge circuit, and each output signal from the ripple compensation pattern generation unit, the current control unit, and the capacitor voltage control unit. And a PWM control unit for inputting an added value of the above and outputting a switching command signal to each of the switching elements. And butterflies.

According to a fourth aspect of the present invention, in the second or third aspect of the invention, the voltage generating means is a compact LC filter for removing or reducing harmonics generated during PWM switching operation of the switching element. It is characterized by comprising at least one of a reactor, an LC filter capacitor, and an attenuation resistor.

According to a fifth aspect of the invention, in the invention according to any one of the second to fourth aspects, the control circuit detects a value of a current flowing from the three-phase full-wave rectifier circuit into the single-phase bridge circuit. When a preset overcurrent threshold is exceeded, one of the upper and lower arms of the single-phase bridge circuit is always turned on and the other arm is always turned off. It is characterized by having a protection part.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, one of the upper and lower arms of the single-phase bridge circuit, which is always in the ON state, is formed by a plurality of switching elements connected in parallel. It is characterized in that it is formed.

According to a seventh aspect of the present invention, in the invention according to any one of the first to sixth aspects, an overcurrent suppressing means for suppressing a current of a certain level or more from flowing through the smoothing capacitor, and the smoothing device. A current detector for detecting a current flowing through the capacitor, and an overcurrent suppression control unit for controlling a suppression operation of the overcurrent suppression unit based on a detection value from the current detector are provided.

According to an eighth aspect of the present invention, in the seventh aspect, the overcurrent suppressing means includes a switching element connected in series with the smoothing capacitor and a resistor connected in parallel with the switching element. According to another aspect of the present invention, the overcurrent suppression control unit turns off the switching element when a detection value from the current detector exceeds a preset threshold value.

[0028]

1 is a block diagram of a first embodiment of the present invention. In this figure, the power supply lines R1, S1, T1 of the three-phase AC power supply 1 are connected to the input side of the main three-phase full-wave rectifier circuit 5 composed of six diodes 4 via a resistor 2 and a system inductance 3. It is connected. The primary side of the transformer 6 is also connected to the power supply lines R1, S1, T1. The lines R2, S2, T2 on the secondary side of the transformer 6 are connected to the first auxiliary three-phase full-wave rectifier circuit 7, and the lines R3, S3, T3 are connected to the second auxiliary three-phase full-wave rectifier circuit 8. It is connected to the.

A smoothing capacitor 9 is connected to the output side of these three-phase full-wave rectifier circuits 5, 7, 8 and a load 10 is connected in parallel with the smoothing capacitor 9. Further, between the output sides of the three-phase full-wave rectifier circuits 5, 7, and 8 and the smoothing capacitor 9, voltage generating means 11 capable of generating an arbitrary voltage waveform is connected. This voltage generating means 11 is
It is controlled by the control means 12 having a control circuit 13 and a gate drive circuit 14.

The voltage generating means 11 is a single-phase bridge circuit 15
have. The single-phase bridge circuit 15 is composed of a capacitor 16 and four switching elements SW1 to SW4, and the output voltage of the capacitor 16 is varied by the PWM switching operation of these switching elements. The voltage generating means 11 also includes a small reactor 17 and a capacitor 18 which form an LC filter for removing higher harmonics generated when the switching elements SW1 to SW4 perform a switching operation, and also the switching elements SW1 to SW4. Attenuation resistor 19 for reducing harmonics generated when switching operation is performed
And have.

On the input side of the main three-phase full-wave rectifier circuit 5, a voltage detector 20 for detecting the line voltage between the power supply lines R1 and S1 is provided, and its detection signal is sent to the control circuit 13. It has become. Further, in the vicinity of the small reactor 17, a current detector 21 that detects a current flowing from the three-phase full-wave rectifier circuits 5, 7, 8 into the single-phase bridge circuit 15 via the small reactor 17 is provided. The detection signal is sent to the control circuit 13. Further, a voltage detector 2 for detecting the voltage across the capacitor 16
2 is connected in parallel with the capacitor 16, and its detection signal is sent to the control circuit 13.

FIG. 2 is an output voltage vector diagram of the transformer 6. R1 to R3, S1 to S3, T1 to T3 in this figure
Correspond to the lines R1 to R3 and S1 to S3 in FIG. 1, respectively. And the vertices of the equilateral triangle are R1, S1, T
It is 1, and R3 and S2 are arranged on a circular arc R1S1 whose radius is the side length of this regular triangle and whose center is T1 and which divides the circular arc R1S1 into three equal parts. Similarly, an arc S1T1 whose radius is the side length of this regular triangle and whose center is R1
S3, at the position above the arc S1T1
T2 is arranged and is on an arc T1R1 whose radius is the side length of this equilateral triangle and which is centered on S1 and which is T1R.
T3 and R2 are arranged at positions that divide 1 into three equal parts.

The transformer 6 includes the illustrated straight lines, that is, the straight lines R1S3 and R1T2 having R1 at one end, the straight lines S1T3 and S1R2 having S1 at the one end, and T1R3 having T1 at the one end. , T1S2 and the respective straight lines of T1S2 are used as output voltage vectors, a total of six-phase AC power is output. The AC voltage output from the transformer 6 based on such an output voltage vector is lower than the AC voltage output from the transformers 109 and 111 (FIG. 11) based on the output voltage vector diagram of FIG. There is. Therefore,
Therefore, the capacity of the transformer 6 can be reduced and the size can be reduced. The reason why the output voltage vector shown in FIG. 2 can lower the output voltage of the transformer than the output voltage vector shown in FIG. 12 has already been proposed by the present applicant. It is disclosed in Japanese Patent Application No. 2000-179543.

FIG. 3 is a time chart showing the conduction states of the main three-phase full-wave rectifier circuit 5, the first auxiliary three-phase full-wave rectifier circuit 7, and the second auxiliary three-phase full-wave rectifier circuit 8. . Each of the R1, S1, and T1 phases of the main three-phase full-wave rectifier circuit 5 becomes conductive at 160 ° in the plus side and minus side of one cycle (360 °). In contrast, the first
The auxiliary three-phase full-wave rectifier circuit 7 and the second auxiliary three-phase full-wave rectifier circuit 8 in which each phase of R2, S2, T2 and R3, S3, T3 becomes conductive is 40 °, and the main 3 It is a quarter of the phase full-wave rectifier circuit 5. Therefore, the power supply lines R1, S1, T
Of the current flowing from 1 to the DC lines P and N, the current flowing through the transformer 6 and the two auxiliary three-phase full-wave rectifier circuits 7 and 8 is one third of the total. In the conventional device shown in FIG. 11, two thirds of the total current flows through the transformers 109 and 111, but the amount of current flowing is halved compared to this, and therefore the transformer capacity can be halved. it can.

FIG. 4 is a block diagram showing the configuration of the control circuit 13 in FIG. The control circuit 13 includes a ripple compensation pattern generator 23, a current controller 24, a capacitor voltage controller 25, and a PWM controller 26.

In the ripple compensation pattern generator 23, an arithmetic circuit (not shown) calculates a DC voltage arithmetic value EPN based on the input of the line voltage detected by the voltage detector 20. The adder 27 calculates the deviation amount between the DC voltage command value VC * and the calculated voltage value EPN from the DC voltage control gain circuit 2
Output to 8. The DC voltage control gain circuit 28 multiplies the deviation amount by the gain G1 to generate a ripple compensation pattern.

In the current controller 24, the adder 29 is
The deviation amount between the direct current command value IL * and the current detection value IL from the current detector 21 is obtained. High-pass filter circuit 3
0 calculates the compensation amount of the harmonic component based on the input of this deviation amount, and outputs this to the adder 31. The adder 31 is
The output of the high-pass filter circuit 30 is subtracted from the output of the adder 29, and this is output to the proportional gain circuit 32. The proportional gain circuit 32 multiplies this by a proportional gain G2 to generate a harmonic current compensation amount.

In the capacitor voltage control unit 25, the adder 33 calculates the deviation amount between the capacitor voltage command value VCA * and the voltage detection value VCA from the voltage detector 22. The proportional gain circuit 34 multiplies this by the proportional gain G3, and the sample hold circuit 35 samples and holds the multiplication result. Further, the integral control circuit 37 multiplies the deviation amount from the adder 33 by the integral gain G4, and outputs this to the adder 38. The adder 38 adds the previous output of the sample hold circuit 39 to the output from the integration control circuit 37, and outputs this to the sample hold circuit 39. Adder 36
Outputs the output of the sample hold circuit 35 and the output of the sample hold circuit 39, and outputs the result to the adder 41.

The adder 41 outputs the output from the adder 40,
The output from the capacitor voltage control unit 25 is added, and this is output to the PWM control unit 26. The PWM control unit 26
Comparators 42 to 45 and carrier signal generation circuits 46 to 49
And have. The comparators 42 to 45 compare the output of the adder 41 and the outputs of the carrier signal generating circuits 46 to 49, and output a signal based on the comparison result. The outputs from the comparators 42 and 43 are inverted by the inverters 50 and 51, and the inverted signals are the PWM signals S1 and S2.
Is output to the gate drive circuit 14. This allows
The switching element SW1 and the switching element SW4, or the switching element SW2 and the switching element SW3 are prevented from being turned on at the same time. In addition, the comparators 44 and 4
The output from 5 is directly output to the gate drive circuit 14 as the PWM signals S3 and S4. Gate drive circuit 14
Outputs a gate signal to the switching elements SW1 to SW4 based on these PWM signals S1 to S4.

Next, the operation of FIG. 1 will be described. When the rectifier is activated, a current flows through the diode 4 of the main three-phase full-wave rectifier circuit 5 at the timing shown by R1, S1, and T1 in FIG. In addition, the transformer 6 has lines R2, S2, T2 and R3, based on the output voltage vector diagram shown in FIG.
Outputs voltage to S3 and T3, and auxiliary three-phase full-wave rectifier circuits 7 and 8
The diode 4 of FIG. 3 has R2, S2, T2 and R3, S of FIG.
Current flows at the timing indicated by 3 and T3. Similar to the conventional device, the valley of the DC voltage ripple output from the main three-phase full-wave rectifier circuit 5 is filled with the outputs of the auxiliary three-phase full-wave rectifier circuits 7 and 8 to reduce the voltage ripple, resulting in harmonic distortion. Is reduced. However, the output voltage of the transformer 6 is low unlike the conventional device, and therefore the transformer 6 has a smaller capacity and a smaller size than those of the conventional device.

Further, in the configuration of FIG. 1, the voltage generating means 11 generates a voltage so as to compensate for the voltage ripple included in the three-phase full-wave rectifying circuits 5, 7, 8 and has a harmonic distortion reducing function. Is improving. That is, the control circuit 13 of the control means 12 generates the PWM signal based on the input of the detection signal from the detectors 20 to 22, and the gate drive circuit 14 outputs the gate signal based on the PWM signal to the switching element SW.
1 to SWS4 for switching control of these switching elements. Then, the harmonics generated by the switching at this time are removed by the small reactors 17 and 18 forming the LC filter, or reduced by the action of the damping resistor 19.

As described above, according to the configuration of FIG. 1, the control means 12 controls the voltage generation means 11 to generate a voltage for compensating for the DC voltage ripple. It is possible to improve the harmonic distortion reduction function without using a DC reactor, and since the transformer 6 that outputs a voltage based on the output voltage vector diagram of FIG. 2 is used, the transformer capacity Can be made smaller, and the device can be made smaller.

Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing the configuration of the control circuit 13A, which is the main part of the second embodiment. That is, the control circuit 13A is different from the control circuit 13 of FIG. 4 in that it has an overcurrent protection unit 52, AND gates 53 and 55, and OR gates 54 and 5.
6 is added. The overcurrent protection unit 52
The detected value IL of the current detector 21 is compared with the threshold value ILT,
The output signals C1 to C4 are output to the gates 53 to 56.

The overcurrent protection unit 52 sets the signals C1 and C3 to "H" in the normal state, that is, when the detected value IL is less than or equal to the threshold value ILT.
And the signals C2 and C4 are set to "L". Therefore, in this state, whether the output signals G1 and G3 of the AND gates 53 and 55 are "H" or "L" is determined by the signals S1 and S3. Similarly, the OR gates 54,
Whether the levels of the output signals G2 and G4 of 56 are "H" or "L" depends on the signals S2 and S4.

Then, the overcurrent protection unit 52 detects the detected value IL.
Exceeds the threshold ILT, the signals C1 and C3 are set to "L" and the signals C2 and C4 are set to "H". Therefore,
In this state, the output signal G of the AND gates 53 and 55
The levels of 1 and G3 are always "L" regardless of the levels of the signals S1 and S3, and the levels of the output signals G2 and G4 of the OR gates 54 and 56 are always "H" regardless of the levels of the signals S2 and S4. Become. As a result, the switching element SW
1, SW3 is off, switching elements SW4, SW2 are on, and the inrush current generated at the time of overcurrent is SW1, SW3.
It will only flow through the lower arm of. Therefore, the overcurrent protection can be effectively performed by appropriately selecting the current capacity of these switching elements. In the above example, the lower arms (SW4, SW2) are turned on,
Although the overcurrent protection is performed by turning off the upper arms (SW1, SW3), the upper arm may be turned on and the lower arm may be turned off.

FIG. 6 is a block diagram of the third embodiment of the present invention. In the configuration of FIG. 6, the switching element SW4 in FIG. 1 is configured by the switching elements SW41 and SW42, and the switching element SW2 is configured by the switching elements SW21 and SW22. That is, also in this embodiment, the control circuit 13A turns on the lower arm and turns off the upper arm to operate the overcurrent protection function, but the lower arm in which the rush current flows is connected in parallel.
It is composed of two switching elements. Therefore, a single-phase bridge circuit can be formed using a switching element having a small current capacity, and a highly reliable overcurrent protection system can be constructed at low cost. Further, in the above example, an example in which one lower arm is configured by two switching elements connected in parallel is shown, but the number of switching elements connected in parallel is
It can be appropriately changed according to the level of the inrush current.

FIG. 7 is a block diagram of the fourth embodiment of the present invention. In the fourth embodiment, the smoothing capacitor 9
Is connected to an overcurrent suppressing means 57 composed of a switching element SWa and a resistor 58 connected in parallel with the switching element SWa, and a current detector 59 for detecting a current flowing through the smoothing capacitor 9 is provided, and a detection signal thereof is controlled by a control circuit. It is configured to output to 13B.

FIG. 8 is a block diagram showing the structure of the control circuit 13B shown in FIG. This control circuit 13B is obtained by adding an overcurrent suppression control unit 60 to the control circuit 13 shown in FIG. The overcurrent suppression control unit 60 outputs an overcurrent suppression signal to the switching element SWa via the gate drive circuit 14 based on the comparison between the detection value IC from the current detector 59 and the threshold value ICT. . That is, the overcurrent suppression control unit 60 determines that the detected value IC is the threshold IC.
When it exceeds T, the "L" signal as the overcurrent suppression signal is output to the gate of the switching element SWa via the gate drive circuit 14. As a result, the switching element SWa that has been in the on state until then becomes the off state, and the current flows through the smoothing capacitor 9 through the resistor 58, so that the overcurrent to the smoothing capacitor 9 is suppressed.

In each of the above embodiments, the voltage generating means 11 has been described as having the elements such as the small reactor 17, the capacitor 18, and the damping resistor 19.
It is possible to adjust the number of these elements according to various conditions and uses, which can reduce the cost. For example, the voltage generating means 11 includes at least one of the small-sized reactor 17 and the capacitor 18, omitting only the damping resistor 19 or leaving only the small-sized reactor 17 and omitting the capacitor 18 and the damping resistor 19.
It can contain one element. Alternatively, it is possible in some cases to omit all the elements of the small reactor 17, the capacitor 18, and the damping resistor 19.

[0050]

As described above, according to the present invention, when three three-phase full-wave rectifier circuits are provided to perform 18-phase rectification, it is not necessary to add a DC reactor, and the practicability is sufficiently high. With a certain configuration, the harmonic distortion reducing function can be further improved, and a rectifying device that can reduce the size of the entire device can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

2 is an output voltage vector diagram of the transformer 6 in FIG.

3 is a time chart showing the respective conducting states of a main three-phase full-wave rectifier circuit 5, a first auxiliary three-phase full-wave rectifier circuit 7, and a second auxiliary three-phase full-wave rectifier circuit 8 in FIG.

FIG. 4 is a block diagram showing a configuration of a control circuit 13 in FIG.

FIG. 5 is a block diagram showing a configuration of a control circuit 13A, which is a main part of a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a third embodiment of the present invention.

FIG. 7 is a configuration diagram of a fourth embodiment of the present invention.

8 is a block diagram showing the configuration of a control circuit 13B in FIG.

FIG. 9 is a configuration diagram of an example of a conventional device.

10 is a waveform diagram of the 6-phase rectified voltage Vrec output from the 3-phase full-wave rectifier circuit 105 in FIG.

FIG. 11 is a configuration diagram of an example of a conventional device.

12 is an output voltage vector diagram of the transformers 109 and 111 in FIG.

13 is a three-phase full-wave rectifier circuit 105A, 11 of FIG.
The wave form diagram which shows the voltage waveform 18 phase rectified by 0,112.

[Explanation of symbols]

1 3-phase AC power supply 2 resistance 3 system inductance 4 diode 5 Main 3-phase full-wave rectifier circuit 6 transformer 7 First auxiliary 3-phase full-wave rectifier circuit 8 Second auxiliary 3-phase full-wave rectifier circuit 9 Smoothing capacitor 10 load 11 Voltage generation means 12 Control means 13, 13A, 13B Gate drive circuit 14 Gate drive circuit 15 Single-phase bridge circuit 16 capacitors 17 Small reactor 18 capacitors 19 Damping resistance 20 voltage detector 21 Current detector 22 Voltage detector 23 Ripple compensation pattern generator 24 Current control unit 25 Capacitor voltage controller 26 PWM control 27 adder 28 DC voltage control gain circuit 29 adder 30 high-pass filter circuit 31 adder 32 proportional gain circuit 33 adder 34 Proportional gain circuit 35 sample and hold circuit 36 adder 37 Integral control circuit 38 Sample and hold circuit 40 adder 41 adder 42-45 comparator 46-49 Carrier signal generation circuit 50 inverter 51 inverter 52 Overcurrent protection unit 53,55 AND gate 54,56 OR gate 67 Overcurrent suppressing means 58 Resistance 59 Current detector 60 Overcurrent suppression controller SW1 to SW4 switching elements SWa switching element 101 3-phase AC power supply 102 resistance 103 system inductance 104 diode 105 3-phase full-wave rectifier circuit 105A Main 3-phase full-wave rectifier circuit 106 DC reactor 107 Smoothing capacitor 108 load 109,111 Transformer 110 First auxiliary three-phase full-wave rectifier circuit 112 Second auxiliary three-phase full-wave rectifier circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Junichi Tsuda             No. 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation             Fuchu Office F-term (reference) 5H006 AA07 CA07 CB01 CC04                 5H007 AA02 AA08 CA02 CB05 CC12                       DA05 DC02 DC05 EA02 EA03

Claims (8)

[Claims] 1. A DC power obtained by rectifying AC power from a 3-phase AC power supply by a 3-phase full-wave rectifying circuit and then smoothing it by a smoothing capacitor, and further, supplying the DC power to a load. The rectifier circuit inputs one main three-phase full-wave rectifier circuit that directly inputs the AC power from the three-phase AC power supply, and the AC power from the three-phase AC power supply via a transformer, and the output side is the main power supply. In the rectifying device, which is composed of first and second two auxiliary three-phase full-wave rectifier circuits connected in parallel with the output side of the three-phase full-wave rectifier circuit, the transformer is the main three-phase R1, S1, T1 are the power supply lines of the respective phases input by the full-wave rectification circuit, and R2 are the power supply lines of the respective phases input by the first and second auxiliary three-phase full-wave rectification circuits via the transformer. S2, T2 and R3, S3, T3,
Moreover, when R1, S1, T1 are the vertices of an equilateral triangle in the voltage vector diagram, the position on each arc R1S1, S1T1, T1R1 whose radius is the side length of this equilateral triangle and which divides these arcs into three equal parts R3, S2, S3, T2, T respectively
3, R2 are arranged in advance, and each vertex R1, S1, T1 and each position S3, T2, T3, R2, R3, S2 on the arc facing the vertex
A total of 6-phase AC power is output so that each straight line connecting to and is used as an output voltage vector, and further, the output side of the main 3-phase full-wave rectifier circuit and the auxiliary 3-phase full-wave rectifier circuit and the A voltage generating means connected between the smoothing capacitor and capable of generating an arbitrary voltage waveform; and a control means for controlling the voltage generating means to compensate for the DC ripple component contained in the output of each rectifier circuit. A rectifying device characterized by being provided. 2. The voltage generating means includes a single-phase bridge circuit which is composed of a capacitor and a plurality of switching elements, and which varies the output voltage of the capacitor by PWM switching operation of these switching elements, and the control means comprises: The detected value of the line voltage of the three-phase AC power supply, the detected value of the current flowing into the single-phase bridge circuit from the three-phase full-wave rectifier circuit, and the detected voltage value of the capacitor in the single-phase bridge circuit are input, and the switching element is input. And a gate drive circuit that outputs a gate signal to the switching element based on the input of the switching command signal. The rectifying device according to claim 1, which is characterized in that. 3. The control circuit includes a ripple compensation pattern generator that outputs a ripple compensation pattern signal based on a deviation between a line voltage detection value and a command value of the three-phase AC power supply, and the three-phase full-wave rectification circuit. From the current control unit that outputs a current control signal based on the deviation between the detected value of the current flowing into the single-phase bridge circuit and the command value, and the deviation between the voltage detection value and the command value of the capacitor in the single-phase bridge circuit A capacitor voltage control unit which outputs a capacitor voltage control signal based on the ripple compensation pattern generation unit, the current control unit, and the added value of each output signal from the capacitor voltage control unit is input, and a switching command signal for each switching element. The rectifying device according to claim 2, further comprising: a PWM control unit that outputs 4. A small reactor for an LC filter, L for removing or reducing harmonics generated during PWM switching operation of said switching element, said voltage generating means, L.
The rectifier according to claim 2 or 3, comprising at least one of a C filter capacitor and an attenuation resistor. 5. The single-phase bridge circuit when the detected value of the current flowing from the three-phase full-wave rectifier circuit into the single-phase bridge circuit exceeds a preset overcurrent threshold value. 5. An overcurrent protection unit that always turns on one of the upper and lower arms of the circuit and always turns off the other arm of the circuit. The rectifying device according to claim 1. 6. One of the upper and lower arms of the single-phase bridge circuit, which is always on, is formed by a plurality of switching elements connected in parallel. 5. The rectifying device according to 5. 7. An overcurrent suppressing means for suppressing an electric current of a certain level or more flowing through the smoothing capacitor, a current detector for detecting a current flowing through the smoothing capacitor, and a detection value from the current detector. 7. The rectifier according to any one of claims 1 to 6, further comprising: an overcurrent suppression control unit that controls the suppression operation of the overcurrent suppression unit based on the above. 8. The overcurrent suppressing means includes a switching element connected in series with the smoothing capacitor and a resistor connected in parallel with the switching element, and the overcurrent suppressing control section includes the current detector. The rectifying device according to claim 7, wherein the switching element is turned off when a detection value from the sensor exceeds a preset threshold value.