KR100398616B1 - Multi-Pulse Thyristor Converting Apparatus using An Auxiliary Circuit - Google Patents

Abstract

The present invention provides a multi-pulse thyristor converter device that improves the waveform of input current and output voltage by increasing the number of pulses by using an auxiliary circuit in a conventional 6-pulse thyristor converter. Provides an auxiliary circuit that can minimize the number of 6-pulse bridge and the number of auxiliary thyristor required, and calculates the optimum control angle of the auxiliary thyristor for the total phase angle by analyzing the input current and output voltage to provide. To this end, the present invention is a three-phase bridge thyristor converting device for converting a three-phase AC input power into a three-phase thyristor bridge to supply a load, a single winding transformer (phase reactor in parallel with the load in the center of the DC terminal) ); Two capacitors connected to both sides of the single winding transformer to divide the DC voltage applied to the DC terminal; A single phase transformer including a primary side connected between an egg tap and a three-phase AC input power source in the center of the single winding transformer, and a secondary side connected between a lower side of the single winding transformer and a lower side of the load; A zigzag transformer connected between the three-phase input AC power source and the primary side of the single-phase transformer; And a plurality of auxiliary thyristors connected to the secondary side of the single phase transformer.

Description

Multi-Pulse Thyristor Converting Apparatus using An Auxiliary Circuit}

The present invention relates to performance improvement through harmonic reduction of a thyristor converter, and increases the number of pulses by adding a simple auxiliary circuit to a conventional 6-pulse thyristor converter, in particular, to improve the waveform of input current and output voltage. A pulse thyristor converting apparatus.

AC / DC (AC / DC) converters using thyristor elements are thyristor controlled, a type of DC motor drive, UPS (Uninterruptable Power Supply) input, HVDC (High Voltage Direct Current) converter, and static reactive power compensator. Reactor). However, due to the switching operation of the thyristor converter, harmonic components related to the number of pulses of the converter are generated in the input current and the output voltage. That is, if the number of pulses of the converter is P, harmonics of Pn ± 1 (n is an integer) are generated at the input current and Pn harmonics are generated at the output voltage.

The harmonics generated in this way cause interference, communication failure, etc. in the adjacent telephone line, and cause malfunctions such as a circuit breaker. Therefore, in order to reduce harmonics, a method of increasing the number of pulses of the converter by multiplexing the thyristor bridge and the phase transformer has been proposed.

1 is a circuit configuration diagram of a typical two three phase 12 pulse rectifier. The waveform of the DC terminal voltage ed between the terminals A0 and B and the voltage vm applied to the phase-reactor is varied according to the phase angle (or control angle) α of the thyristors T1 to T12. At this time, by double-connecting two 6-pulse converters, the input current is has a stepped waveform having the characteristics of 12-pulse, and the fifth and seventh harmonics are removed (see FIG. 2 (a)).

The DC-link voltage ed includes a pulse current (12f, where f is the power frequency) corresponding to 12 times the power frequency (see FIG. 2 (b)), wherein a phase transformer having a 30 ° phase difference between the two bridges ( 2, 4, 8), and in order to operate the two six-pulse bridge (1, 3) independently, it is necessary to use the interphase reactor 5 as shown in FIG. However, this dual connection does not eliminate the 11th and 13th order or higher harmonics in the input current. In order to remove the higher harmonics, the number of pulses of the converter must be further increased. To increase the number of pulses, the number of 6-pulse bridges must be increased and a phase transformer accordingly can be used. In order to implement P-pulse in such a multiplexing method, P thyristors must be used and the number of phase transformers must be increased.

Figure 3 is shown in the prior art US Pat. No. 4,532,581. 4 is a circuit diagram for reducing harmonics and pulse flow applied to a double three-phase 12-pulse rectifier.

The U.S. Patent No. 4,532,581 discloses a 12-pulse converter while maintaining the bridge dual connection of FIG. 1 without increasing the number of 6-pulse bridges in reducing the harmonics of the AC input current is and the pulsation of the DC-link voltage ed. It is a multi-pulse thyristor converter device that increases the number of pulses by using an auxiliary thyristor connected to a tap of a phase-reactor as a base. As an example of this method, the waveforms of the input current and the output voltage in the case of performing 24-pulse operation using two thyristor elements in the auxiliary circuit are shown in FIG. This method does not need to increase the number of bridges simply to increase the number of pulses, and there is an advantage that does not require the use of a complicated phase transformer. However, the two 6-pulse bridges (1, 3) must be doubled. Should be based on a 12-pulse converter. In addition, phase transformers 2, 4 and 8 must be used to produce a 30 ° phase difference. Such a phase transformer has a capacity rating almost equal to the load capacity, and the phase reactor 5 is saturated due to the difference in leakage inductance caused by the asymmetry of the Δ-Υ type transformers 2 and 4, causing the circuit to malfunction. There is a problem that can be.

In order to solve the above problems, the present invention adds an auxiliary circuit to a conventional 6-pulse thyristor converter without using a separate phase transformer to increase the number of pulses of input current and output voltage to reduce harmonics. It provides an auxiliary circuit that can minimize the number of auxiliary thyristors required to increase the number of pulses by improving the performance, add P / 6 thyristors of the auxiliary circuit to enable the operation of the P-pulse, An object of the present invention is to provide a multi-pulse thyristor converting apparatus using an auxiliary circuit that calculates and provides an optimum control angle of an auxiliary thyristor for an entire phase angle by analyzing input current and output voltage.

1 is a circuit diagram of a typical two three phase 12 pulse rectifier;

2 is a waveform diagram of an input current and an output voltage in the circuit diagram of FIG. 1;

Figure 3 is shown in the prior art US Pat. No. 4,532,581. 4,

4 is a waveform diagram of an input current and an output voltage during 24-pulse operation in the circuit diagram of FIG. 3;

5 is a diagram illustrating an embodiment of a multi-pulse converter according to the present invention;

6 is a waveform diagram of each part of the multi-pulse converter according to the present invention;

7 is an operation explanatory diagram of the auxiliary thyristors Tp and Tq configured on the secondary side of the current injection single phase transformer TFm in the auxiliary circuit according to the present invention;

8 is a switching function expression diagram for showing the relationship between the input current for the 'a' phase of the three-phase thyristor bridge front and the output current of the rear stage according to the present invention,

9 is an exemplary view of the optimum firing angle β of the auxiliary thyristor with respect to the phase angle α of the multi-pulse thyristor converter according to the present invention;

10 is an exemplary diagram of total harmonic distortion of an input current with respect to a phase angle α of a multi-pulse thyristor converter according to the present invention;

11 is a configuration and operation waveform diagram of the auxiliary thyristor for 18-pulse and 24-pulse operation according to the present invention,

12 is a waveform diagram of input current and load voltage of a P-pulse when the phase angle α of the multi-pulse thyristor converter according to the present invention is 30 °.

13 is an exemplary diagram of a power disconnect type multi-pulse thyristor converter according to the present invention;

14 is an operational waveform diagram of a 12-pulse converter according to the present invention;

15 is an operational waveform diagram of an 18-pulse converter according to the present invention;

16 is an operational waveform diagram of a 24-pulse converter according to the present invention;

Table 1 is a control method and performance table of the multi-pulse thyristor converter according to the present invention.

* Description of the symbols for the main parts of the drawings *

510: three-phase AC input power 520: three-phase thyristor bridge

530: single winding transformer 540: single phase transformer and auxiliary thyristor

550: Zig-zag transformer 560: DC voltage division capacitor

570: load

Multi-pulse thyristor converting apparatus using the auxiliary circuit of the present invention for achieving the above object is a three-phase thyristor bridge converting apparatus for supplying a load by converting the three-phase AC input power into a three-phase thyristor bridge A single winding transformer (phase reactor) connected in parallel with the load in the center of the DC terminal; Two capacitors connected to both sides of the single winding transformer to divide the DC voltage applied to the DC terminal; A single phase transformer including a primary side connected between an egg tap and a three-phase AC input power source in the center of the single winding transformer, and a secondary side connected between a lower side of the single winding transformer and a lower side of the load; A zigzag transformer connected between the three-phase AC input power and the primary side of the single-phase transformer; And a plurality of auxiliary thyristors connected to the secondary side of the single phase transformer.

In addition, the present invention is a power separation type three-phase thyristor bridge converting device for converting a three-phase AC input power into a three-phase thyristor bridge to supply a load, a single winding transformer connected in parallel with the load at the center of the DC terminal ( Interphase reactor); Two capacitors connected to both sides of the single winding transformer to divide the DC voltage applied to the DC terminal; A single phase transformer including a primary side connected between an egg tap and the three-phase input AC power source in the center of the single winding transformer, and a secondary side connected between a lower side of the single winding transformer and a lower side of the load; And a plurality of auxiliary thyristors connected to the secondary side of the single phase transformer.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. .

5 is a diagram illustrating an embodiment of a multi-pulse converter according to the present invention, which is configured by adding a simple auxiliary circuit to an existing six-pulse converter.

The auxiliary circuit is a low-capacity DC voltage splitting single winding transformer TFpq (530) is connected in parallel with the load 570 at the center of the DC terminal, the primary side of the current injection single-phase transformer TFm (540) for splitting the DC voltage The secondary side of the single-phase transformer TFpq 530 for the current injection between the egg tap and the three-phase input stage 510 in the center of the single-stage transformer TFpq 530 and the secondary side of the single-phase transformer TFpq 530 for dividing the DC voltage and the A zigzag transformer TFn 550 connected between the lower side of the load 570 and dividing the injection current evenly into three phases has a three-phase input terminal 510 in front of the three-phase thyristor bridge 520 and the current. It is connected between the primary side of the injection single-phase transformer TFm (540). On the other hand, DC voltage dividing capacitors 560, Cp, and Cq, which divide and divide the DC voltage at the rear end of the three-phase thyristor bridge 520, are formed on both sides of the DC voltage dividing single winding transformer TFpq 530, The secondary side of the current injection single phase transformer TFm 540 is configured with auxiliary thyristors Tp and Tq to control the phase angle α.

6 is a waveform diagram of each part when the phase angle α of the multi-pulse converter according to the present invention is 30 °, and the output voltage vd of the multi-pulse converter varies according to the phase angle α and has six pulse characteristics.

When the DC voltage dividing capacitor 560 is attenuated so that the DC ripple voltage is negligible using a large capacity, the primary voltage of the single-phase transformer TFm 540 for current injection is as shown in Equation 1 below.

That is, the primary side voltage of the current injection single phase transformer TFm 540 has various waveforms according to the phase angle α of the converter and the frequency is three times the power frequency. 6 shows a waveform of the primary side voltage vm of the single-phase transformer TFm 540 for current injection when the phase angle α is 30 °.

7 is an explanatory view of the operation of the auxiliary thyristors Tp and Tq configured on the secondary side of the current injection single phase transformer TFm 540 in the auxiliary circuit according to the present invention.

The auxiliary thyristors Tp and Tq use a rising edge of the primary voltage vm of the single phase transformer TFm 540 for current injection as a reference point of βp and βq, which are the firing angles of the auxiliary thyristors Tp and Tq, respectively. The auxiliary thyristors Tp and Tq allow one of the two to always conduct the load current.

That is, if the auxiliary thyristor Tq is conducting when the primary side voltage vm of the current injection single-phase transformer TFm 540 is positive, the auxiliary thyristor Tp is forward biased and when the auxiliary thyristor Tp is fired at βp, the current ( As shown in Fig. 7A, the output current Io is conducted so that the current in the forward direction flows to the primary side of the single-phase transformer TFm 540 for current injection.

im = (Ns / Np) Io

In addition, if the auxiliary thyristor Tp is conducting when the primary side voltage vm of the current injection single-phase transformer TFm 540 is negative, the auxiliary thyristor Tq is forward biased and when the auxiliary thyristor Tq is fired at βq, the current ( As shown in FIG. 7B, the output current Io is conducted to flow current in the following negative direction to the primary side of the current injection single-phase transformer TFm 540.

im =-(Ns / Np) Io

By repeating the auxiliary thyristors Tp and Tq in this manner, the primary side current im of the current injection single-phase transformer TFm 540 becomes a waveform having a 2-level as shown in FIG. Since 560 is bi-divided into Cp and Cq, the output currents io1 and io2 at the rear of the three-phase thyristor bridge 520 are as follows.

8 is a switching function expression diagram for showing the relationship between the input current for the 'a' phase of the three-phase thyristor bridge 520 according to the present invention and the output current of the rear stage.

That is, in order to show the relationship between the input current of the 'a' phase of the three-phase thyristor bridge 520 and the output current of the rear stage, the switching functions Sa + and Sa- are defined as shown in FIG. The switching function is

Sb + = Sa + ∠-120 °, Sb- = Sa-∠-120 °

Sc + = Sa + ∠ + 120 °, Sc- = Sa-∠ + 120 °

The input current of the front end of the three-phase thyristor bridge 520 from the switching function of Equations 6 and 7 is as follows.

Under the action of the zigzag transformer TFn 550, the primary side current im of the single-phase transformer TFm 540 for current injection is equally divided into three so that the injection currents (ix, iy, iz) are as follows.

At this time, the input current ia is as shown in Equation 10 below.

The input current is summarized according to the above equations as follows.

From Equation 11, the input current is changed according to the winding ratio K = Ns / Np of the current injection single phase transformer TFm 540, and when the winding ratio K is 0.929, the total harmonic distortion (THD: Total Harmonic Distortion) Is the minimum of 14.19 percent.

9 is an exemplary view of the optimum firing angle β of the auxiliary thyristor with respect to the phase angle α of the three-phase thyristor bridge 520 according to the present invention.

That is, for the 12-pulse operation, the auxiliary cycle for maintaining the total harmonic distortion of the input current at 14.19 percent in the entire phase angle (phase angle 0 ° <α <180 °) of the three-phase thyristor bridge 520. The firing angle β of the Lister is as follows. The phase angle α is 0 ° ≦ α ≦ 30 ° 0 ° ≦ β ≦ 30 °, 30 ° ≦ α ≦ 150 ° β = 30 ° and 150 ° ≦ α ≦ 180 ° 30 ° ≦ β ≦ 60 °.

In addition, the firing angle β of the auxiliary thyristor to maintain the total harmonic distortion of the input current to 9.26 percent in the phase angle of 10 ° <α <170 ° of the three-phase thyristor bridge 520 for 18-pulse operation Is as follows. The phase angle α is 10 ° ≦ α ≦ 30 ° 0 ° ≦ β ≦ 20 °, 30 ° ≦ α ≦ 150 ° β = 20 ° and 150 ° ≦ α ≦ 170 ° 20 ° ≦ β ≦ 40 °.

Finally, the firing angle of the auxiliary thyristor for maintaining the total harmonic distortion of the input current at 7.42 percent in the phase angle 15 ° <α <165 ° of the three phase thyristor bridge 520 for 24-pulse operation. β is as follows. The phase angles α are 15 ° ≦ α ≦ 30 ° 0 ° ≦ β ≦ 15 °, 30 ° ≦ α ≦ 150 ° β = 15 ° and 150 ° ≦ α ≦ 165 ° 15 ° ≦ β ≦ 30 °.

10 is an exemplary diagram of total harmonic distortion of the input current with respect to the phase angle α of the three-phase thyristor bridge 520 according to the present invention.

The 12-pulse converter can maintain the total harmonic distortion at 14.19 percent over the entire phase angle of the three-phase thyristor bridge 520. In addition, in the case of an 18-pulse converter, the total harmonic distortion can be maintained at 9.26 percent at a phase angle of 10 ° <α <170 ° in the three-phase thyristor bridge 520, and in the case of a 24-pulse converter, the three-phase It is possible to maintain the total harmonic distortion at 7.42 percent in the phase angle 15 ° <α <165 ° of the thyristor bridge 520.

Here, the phase angle α of the three-phase thyristor bridge 520 in an 18-pulse operation ranges from 0 ° to 10 ° and 170 ° to 180 °, and the phase angle α of the three-phase thyristor bridge 520 in 24-pulse operation. The total harmonic distortion is slightly increased in the 0 ° to 15 ° and 165 ° to 180 ° sections because the secondary thyristor is not forward biased in this section, making it impossible to make the primary current im of the current injection transformer TFm. to be.

As described above, the input current is always 12 by adjusting the firing angles βp (= β) and βq (= β + 60 °) of the auxiliary thyristors Tp and Tq according to the phase angle α of the three-phase thyristor bridge 520. It is possible to maintain the waveform of the pulse characteristic.

That is, FIG. 6 shows that the input current ia has a 12-pulse waveform when the phase angles α = 30 °, βp = 30 ° and βq = 90 ° of the three-phase thyristor bridge.

Meanwhile, as shown in FIG. 5, the voltage vo applied to the load terminal is as follows.

At this time, the voltage vx in Equation 12 becomes vx = (Ns / Np) vm when Tp conducts, and vx =-(Ns / Np) vm when Tq conducts. As a result, the voltage vx is thus added to the output voltage vd of the three-phase thyristor bridge 520 so that the load voltage vo applied to the load stage obtains an improved waveform of 12-pulse.

11 is a configuration and operation waveform diagram of an auxiliary thyristor for 18-pulse and 24-pulse operation according to the present invention.

According to the present invention, it is possible to operate a 12-pulse by adding two auxiliary thyristors to a conventional 6-pulse converter. In the same manner, a P-pulse converter is used by using P / 6 thyristors in an auxiliary circuit. Can be implemented. That is, the number of pulses can be increased infinitely only by adding the auxiliary thyristors.

When the firing angles βq, βn and βp for the auxiliary thyristors Tq, Tn and Tp for 18-pulse operation are as shown in Fig. 11 (a), the current im induced at the primary side of the current injection transformer TFm is 3-level. Has a waveform. Similarly, when the firing angles βq1, βq2, βp2 and βp1 for the auxiliary thyristors Tq1, Tq2, Tp2 and Tp1 for 24-pulse operation are as shown in Fig. 11 (b), the primary side of the current injection transformer TFm 540 The current im induced at has a four-level waveform.

All equations derived from the 12-pulse converter are also valid in the P-pulse converter, and the input current ia of Equation 11 varies according to the primary current im of the current injection transformer TFm 540.

12 is a waveform diagram of input current and load voltage of the P-pulse when the phase angle α of the three-phase thyristor bridge 520 according to the present invention is 30 °.

12 (a) shows that the input current ia and the load voltage vo have 18-pulse characteristics when the phase angle α of the three-phase bridge thyristor 520 is 30 °, and FIG. 12 (b) shows 24-pulse. It can be seen that it has the characteristics of.

Table 1 shows a control method and a performance example of the P-pulse converter according to the present invention.

That is, the winding ratio of the current injection transformer for the 12-pulse converter, the 18-pulse converter and the 24-pulse converter, the optimum firing angle of the auxiliary thyristor, the conduction order of the auxiliary thyristor, the total harmonic distortion of the input current and the load voltage. Ripple Factor (RF) is presented.

In either case, the degree of freedom for the optimum firing angles of the respective auxiliary thyristors is 1, and the optimum firing angle β for any three-phase bridge thyristor phase angle α may be obtained and then fired at regular intervals. In addition, the firing method for one cycle of the input voltage is operated from the auxiliary thyristor on the left side to the auxiliary thyristor on the right side, and then to the auxiliary thyristor on the left side.

13 is an embodiment of a separate power supply type P-pulse converter according to the present invention.

In applications such as UPS or SVC that require separation from the power supply, it is sufficient to inject current into the Δ-Y peripheral voltage of the existing power stage without using a zigzag transformer separately.

14 is an operational waveform diagram of a 12-pulse converter according to the present invention.

15 is an operational waveform diagram of an 18-pulse converter according to the present invention.

16 is an operational waveform diagram of a 24-pulse converter according to the present invention.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains, and the foregoing embodiments and the accompanying drawings. It is not limited to.

As described above, the present invention uses the auxiliary circuit described above as an additional function to the existing 6-pulse converter to increase the number of pulses, thereby reducing the harmonics of the input current and the output voltage to multi-pulse the existing bridge. Unlike the multi-pulse method based on the 12-pulse converter by double connection, it is not necessary to use a phase transformer rated at the same load capacity and solves the saturation problem of the phase reactor due to the asymmetry of the phase transformer which is a problem of the double connection. It is effective. In addition, the auxiliary circuit using the minimum number of thyristors can be used to improve the waveform of the input current and output voltage, and the use of the minimum thyristors enables economical converter implementation.

Claims (10)

In a converting apparatus using a three-phase thyristor bridge that converts a three-phase AC input power into a three-phase thyristor bridge and supplies it to a load, A single winding transformer connected in parallel with the load at the center of the DC terminal; Two capacitors connected to both sides of the single winding transformer to divide the voltage applied to the DC terminal; A single phase transformer including a primary side connected between an egg tap and a three-phase AC input power source in the center of the single winding transformer, and a secondary side connected between a lower side of the single winding transformer and a lower side of the load; A zigzag transformer connected between the three-phase AC input power and the primary side of the single-phase transformer; And And a plurality of auxiliary thyristors connected to the secondary side of the single phase transformer. The method of claim 1, The plurality of auxiliary thyristors are multi-pulse thyristors converting apparatus using an auxiliary circuit, characterized in that using P / 6 to make a P-pulse. The method of claim 2, Multi-pulse thyristor converting apparatus using an auxiliary circuit, characterized in that the plurality of auxiliary thyristors are two. The method of claim 2, Multi-pulse thyristor converting apparatus using an auxiliary circuit, characterized in that the plurality of auxiliary thyristors three. The method of claim 2, Multi-pulse thyristor converting apparatus using an auxiliary circuit, characterized in that the plurality of auxiliary thyristors four. The method according to any one of claims 1, 2, 3, The relationship between the firing angle β of the plurality of auxiliary thyristors and the phase angle α of the three-phase bridge thyristor 0 ° ≤ β≤ 30 ° at 0 ° ≤ α≤ 30 °, 150 ° ≤ α≤ 180 ° 30 ° ≤ β≤ 60 ° Multi-pulse thyristor converting apparatus using an auxiliary circuit characterized in that. The method according to any one of claims 1, 2 and 4, The relationship between the firing angle β of the plurality of auxiliary thyristors and the phase angle α of the three-phase bridge thyristor 0 ° ≤ β≤ 20 ° at 10 ° ≤ α≤ 30 °, 20 ° ≤ β≤ 40 ° at 150 ° ≤ α≤ 170 ° Multi-pulse thyristor converting apparatus using an auxiliary circuit characterized in that. The method according to any one of claims 1, 2, 5, The relationship between the firing angle β of the plurality of auxiliary thyristors and the phase angle α of the three-phase bridge thyristor 0 ° ≤ β≤ 15 ° at 15 ° ≤ α≤ 30 °, 150 ° ≤ α≤ 165 ° 15 ° ≤ β≤ 30 ° Multi-pulse thyristor converting apparatus using an auxiliary circuit characterized in that. In a converting apparatus using a separate power three-phase thyristor bridge that converts the three-phase AC input power into a three-phase thyristor bridge to supply a load to the load, A single winding transformer connected in parallel with the load at the center of the DC terminal; Two capacitors connected to both sides of the single winding transformer to divide the voltage applied to the DC terminal; A single phase transformer including a primary side connected between an egg tap and the three-phase input AC power source in the center of the single winding transformer, and a secondary side connected between a lower side of the single winding transformer and a lower side of the load; And And a plurality of auxiliary thyristors connected to the secondary side of the single phase transformer. The method of claim 9, The plurality of auxiliary thyristors are multi-pulse thyristors converting apparatus using an auxiliary circuit, characterized in that using P / 6 to make a P-pulse.