SU1203629A1 - Method and apparatus for protection of excited bridge thyristor voltage inverter - Google Patents

Abstract

The invention allows to increase reliability, speed, efficiency and reduce weight and size parameters. This is achieved by the fact that, in the method of protecting an autonomous bridge thyristor voltage inverter, simultaneously with the supply of control pulses to the thyristors of the short-circuit, they remove the control pulses Q of the inverter thyristors. Introduce back EMF into the shoulders of the inverter thyristor bridge in the interval of the first half-period of the oscillatory discharge of the J-C capacitor, and then remove the control pulses from the short-circuit thyristors .4 Il. S (L Od 05 ka; o

Description

The invention relates to a converter technique, in particular, to methods and devices for the protection of contact-type multiphase bridge voltage inverters against through short circuits during the inverting thyristor bridge.

The purpose of the invention is to increase reliability, speed, efficiency and reduction in weight and size parameters.

FIG. 1 shows the principle-i schematic diagram of an apparatus for carrying out the method; Fig. 2 shows equivalent circuit replacement circuits for a row of a filter capacitor for individual stages of the discharge process; in FIG. 3, timing diagrams illustrating electromagnetic processes in the proposed protection device when it is activated; 4 is a schematic diagram of the device, the second option.

In the diagrams / fig. 1, 2, and 4) are labeled 1-1 SOURCE 1 of the input alternating voltage with terminals A., 5, C uncontrollable bridge rectifier 2 t +) and (-), respectively, positive --- positive I negative poles of a DC link resistor 3 and diode 4 extinguishing RD-circuit, transformer 5 with primary winding 6 (winding turning point); filter capacitor 7, secondary windings 8-3, main inverting bridge thyristors 14-19, reverse diodes 20-25, thyristor short circuiter 26, inverter tipping sensor 27, threshold unit 28, short-circuit thyristor control pulse forming unit 29 kozamikatel, storage element 30, the inverter control system 31, the inverting thyristor control signal generating unit 32, while IJ (. - voltage across the condenser - current of the filter capacitor 7;

filter 7; ij; - current extinguishing

RD chains; Q is the total current of the filter capacitor and the quenching R5 circuit;

“- current thyristor korotkozamy- katel.

, Fig. 3 shows the curves of the listed currents and voltages when the protection is triggered as a function of the current electric angle b, associated with the current time t by the ratio

-

one

ten

15

EO

25

and.

 - WITH ,

HLC

where L is reduced to primary

winding 6 is equivalent to the inductance of the windings of the transformer 5;

C is the capacitance of the filter capacitor 7.

At the moment the protection is triggered, the conditionally accepted value of the angle, the characteristic points along the axis 0 are designated: Q ,,, ..., Q. In the circuit of FIG. 1 to the poles of the DC link are connected directly. The output terminals of the rectifier 2, the input terminals of the inverting bridge on the thyristors 4-19 and the diodes 20-25, as well as a filter with an extinguishing RD circuit and thyristor short circuit conditionally shown in the form of a thyristor 26. The primary winding 6 of the transformer 5 is connected in series with the filter capacitor 7 and in the normal mode of operation of the inverter serves as a current-limiting reactor of the LC filter, and when it is protected, it provides the oscillatory nature of the discharge process. The capacitor 7, the secondary windings 8, 11, 9, 12, 10 and 13 of the transformer 5 are included in the inverting thyristor arms of the bridge in relation to the primary winding 6 and in the normal mode of operation of the inverter play the role of reactors installed in the inverting thyristor arms of the bridge, and - when a protection is triggered - they are sources of back-EMF in the arms of the said bridge, i.e. An emf directed in opposite to the normal polarity of a constant voltage link. The transformation ratio of the transformer 5 from the primary winding 6 and its secondary windings is chosen sufficiently large (on the order of k (10-20), on the basis of ensuring reliable switching of the load current in the inverting bridge thyristors due to the back-EMF in the secondary windings of the transformer 5.

Thus, the number of turns of the secondary windings of the transformer 5 55 can be chosen sufficiently small (on the order of 1 to 2 turns), which, on the one hand, causes a small influence of electromagnetic processes.

thirty

35

40

45

50

in the filter on the corresponding processes in the phases of the inverter and small. The mutual interaction of the latter in the normal mode of operation of the inverter, and on the other hand, facilitates the design requirements of the transformer 5 as part of the inverter. At the same time, the inductance of the primary winding 6 of the transformer 5, which acts as a current-limiting filter reactor, is chosen to be rather small compared with the inductance of the stator windings of the generator 1 brought to the constant voltage link and, therefore, turn on the secondary winding with the filter capacitor 7 does not practically impair the operation of the filter

The tilting inverter sensor 27 (emergency condition sensor) may be configured as a transformer, the primary winding of which is connected in series with the filter capacitor 7, and the secondary winding is the output of the tilting sensor connected to the input of the threshold unit 28. Vpsod the block 28 is connected to the input of the short-circuit thyristor control pulse shaping unit 29 of the short circuit 26. The block 29 can be performed, for example, as a single-oscillator with output output amplifiers connected by its output circuits and to the control electrodes of the short-circuit thyristor 26. The output of the threshold unit 28 is also connected to the input of the storage element 30 (executed, for example, on a trigger), the output of which is connected to the blocking input of the thyristor control signal generating unit 32, to another input of the unit 32 the output of the inverter control system 31 is connected, and the output of the block 32 is connected to the control electrodes of the inverting thyristors 14-19.

The device works as follows.

When the inverter overturns (through the inclusion of two thyristor arms in any of the inverter phases), the voltage of the filter capacitor 7 is applied to the windings of the transformer 5, as well as to the primary winding of the tilt sensor transformer 27. In this case, on the second time, 036294

A voltage pulse is generated in the winding of the transformer of the tilting sensor 27, which is fed to the input of the threshold unit 28. At the time

5, the amplitude of this impulse of the set level, the threshold unit 28 generates a signal which, on one side through the short-circuit thyristor control pulse generation unit 29, produces a pulse-fixed-duration control of the thyristor rotor 26, and on the other side, through the storage element 30

The ts blocks the supply of control pulses to the inverting thyristors 14 to 19 from the control system 31. Thereby, all the thyristors of the short circuit 26 are subjected to a grazing with simultaneous removal of control from all the inverting thyristors, and the filter capacitor 7 begins to discharge in the circuit of the capacitor plate 7, connected to the beginning of the winding 25 and 6, - the beginning of the primary winding 6 of the transformer 5 - the end of the primary winding 6 of the transformer 5 is a three-short short-circuiter 26 — a plate of a capacitor 7 connected

3Q To the negative pole (-) of the link. constant voltage. At the same time, on the one hand, the thyristors of the short-circuited phase of the inverted inverter are unloaded from the discharge current of the filter capacitor, and on the other hand, the positive discharge pulse i of the capacitor 7 of the filter through the primary winding 6 trans4) of the formator 5 induces in the secondary windings 8 13, tapped at the shoulders of the inverting bridge, the protrusion-emf, directed to meet the normal polarity of the constant-voltage link 5: at the expense of which the interval of the first half-wave of the filter capacitor is provided Unloading the load current from the shoulders of the bridge of inverting thyristors to the short-circuit circuit and disconnecting them. The parameters of the oscillation process of the discharge of the filter capacitor 7 at the initial stage of the process are determined by the capacitance C of the capacitor 7 and the inductance L of the transformer 5 equivalent to the primary winding 6. The equivalent circuit for replacing the discharge circuit of the capacitor 7 at the initial stage

35

40

45

50

bit at O - S t

shown in FIG. 2a. In this area, the currents and voltages in the discharge circuit are determined with sufficient accuracy by the ratios

and. and,. soBe.

i- co 3

(2) t3)

where Ufj, is the initial value of the PIR voltage and, on the filter capacitor at 1, the amplitude of the discharge current of the filter capacitor, defined according to the expression

()

g for example. At values b b-,

According to (3), changes: sign and becomes negative, as a result of which the diode 3 of the extinguishing RO-circuit is turned on and the parameters for the selective process of the discharge of the capacitor 7 are determined in accordance with. VII with an equivalent replacement circuit of FIG. 2 & In this case, currents and voltages can be calculated by the following expressions:

I.

5 C05 tp

, 6-2 | С05Ц; -Ц,

 . (five)

 SOC)

 e- ° (. (9- |) cosc., (6)

, .I ,, n ((7)

T) 5Ч Ь (8)

where D is the attenuation coefficient determined according to the formula

D - -JT O 5 2Rlc

where C is the capacity of the smoothing capacitor 7;

U is the sum of the inductances of the reactors 8.11 or 9.12 or 10.13, respectively, when substituting the corresponding values of L and C (and the range of values of the parameter D 1 is considered);

 is the attenuation angle associated with the attenuation coefficient D by the ratio

D dinl. (9)

Relations (5) - (8) are valid for describing electromagnetic processes in the recharge circuit of capacitor 7 in the interval 9 t ts 9 b 9v, where 6 is defined in accordance with the expression

 ten

,, „..

(ten)

At this interval, at

angle & 0, where b |

t

+ -J-x

2 D0 (f

the current of the capacitor 7 changes sign, providing at b 62 the charge of the capacitor 7 in positive relative to the normal polarity

(P)

20

DC link from

voltage level

, ifif (,. (12) Uc49., e,

For values of the angle Q - 0, where 01 is determined by the formula

(3)

", 5-L)

The positive current t of the filter flows from the beginning to the end of the primary winding 6 of transformer 5 along the circuit of short circuit 26, if the equality i t is the strength is approximately equal to neglecting the component of the load current and the components of the current of the secondary windings of the transformer 5. switching current pulses are induced oppositely to the normal polarity of the dc link and ensure the switching of the inverting thyristors 14 19 during the half-wave of the transient charge capacitor filter. With Q values, the current i g changes sign, becomes negative and closes through the diodes of uncontrolled top 2, ensuring that the thyristors of the short circuit 26 turn off, the thyristor control of the short circuit 26 should be removed at that time). Thus, to ensure the removal of the control pulses of the short-circuit thyristors after the time of the first half-period of the oscillatory discharge of the capacitor

LC filter duration

t kch

the thyristor control pulse of the short-runner 26, set by a single vibrator in the formation unit 29, must satisfy the inequality

t..e ,,

where Q is determined according to formula 13) .: when the angle S 0 4 5 is determined according to formula (1E), the polarity of the voltage on the capacitor 7 changes, resulting in a diode 3 of the extinguishing Q-circuit, and the charge circuit of the capacitor 7 is determined again in accordance with the equivalent replacement circuit by the formulas

with

-one,

(

, e-cos

IflA 2Uco

-litd iJ

b.

sm

CoZ (f I

r coetpj

K14)

(15)

of

Process

charge capacitor 7

five

Where

moment W

9 is determined by

e, 1g (

1 +

costp

(sixteen)

In this case, the voltage on the torus 7.

U, 19

THAT, at the selected value And 0.5, provides a decrease in the voltage Up on the capacitor 7 to 16.3% of its initial level. When the described process proceeds, switching of the main thyristors of the short-circuit inverter is provided, and switching of the main thyristors of the inverter takes place in the interval

0 e

ё9 during the first flow

filter through the primary winding 6 of the transformer 5 due to the switching current in the secondary windings of Transformer 5 in the inverter arms with approximate equality

,

where VT- is the transformation ratio of the transformer 5, and the switching of the thyristors of the short circuit 26 is provided on the interval when the second (negative) half-wave current ig of the filter flows

0

five

0

five

0

five

0

five

five

through unmanaged diode 2 diodes,

Thus, the duration. the commutates of the lean current for the main thyristors of the inverter tj-r and for the thyristors of short circuit i are determined in accordance with the expressions

.-:; s

t, fLCtЭ5-00

 kT 0.

 2 3

0 b

where 0.0 and bj are defined according to formulas (11), (13) and (, 16),

All the above calculated ratios characterizing the electromagnetic processes in the converter during the implementation of the proposed method of protection, according to. Under the assumption that the load current 1.p is small, compared with amplitude 1, the discharge current of the filter capacitor. Such an assumption takes place when considering the relays of operation of power inverters and is quite acceptable in the qualitative analysis of the aforementioned electromagnetic processes.

The second variant of the device circuit differs from the circuit of FIG. 1 in that the transformer 5 is structurally made in the form of two transformers. They provide similar functions as the inverting thyristors of the anodic and cathodic groups, respectively, in the process of direct half-wave of the filter capacitor.

The specified separation of the transformer under certain conditions allows to simplify the design of the transformer. The operation of the circuit in FIG. 4 is similar to the operation of the circuit in FIG. 1,

The proposed protection device for an autonomous voltage inverter, realizing a method for protecting an inverter during the overturning of inverting thyristors with a direct current from the discharge of a filter capacitor, ensures an increase in the protection speed and reliability of the specified inverting thyristor quenching, does not require installing a special separation reactor loaded the normal operation of the inverter with the full current of the converter, which ensures an increase in the efficiency and a decrease in the maximum

9.1203629

compared to the known device. At the same time, shock currents from the side of the power source and the load of the inverter through the short-circuit DC link when the inverter overturns are eliminated, a significant reduction of the voltage filter being restored during the reloading of the capacitor in the link of the constant April applied to the inerting bridge, also provided and, consequently, the reserve of energy in the Iltra condenser.

Claims (2)

1. A method of protecting an autonomous bridge thyristor voltage inverter equipped with a thyristor short-circuit, shunting the constant voltage link, and an input LC filter, which implies control pulses at the time of the emergency process to drive short-circuit thyristors with tiri. After the expiration of the oscillating discharge half-period of the filter capacitor and removing the control pulses from the inverter thyristors, they are distinguished, and so that, in order to increase reliability, speed, efficiency, and weight and size, the control pulses are fed to the short-circuit thyristors remove the control pulses from the thyristors of the inverter, inject counter-emf into the shoulders of the bridge ti pe. and 5 pack but ra ten . no sun 15 on the next page 20 but de va che i 25 ya ka me ka va 30 Yusch kP for - po vk then pr in Q by ten inverter thyristors on the interval of the first half-period of the oscillatory discharge of the LC filter capacitor and then remove the pulses Controls with short coil thyristors. 2. Device for protection of autonomous bridge thyristor voltage inverter, including . an inverting thyristor bridge with oppositely connected reverse diodes and fed from an uncontrollable transistor through an intermediate link of a constant a voltage containing a circuit of a series-connected resistor and a diode connected parallel to the filter capacitor in the blocking direction with respect to the normal polarity of the voltage across the filter capacitor, an inverter tilt sensor whose output through the threshold unit is connected to the input of the pulse shaping unit controlling the thyristor of the shorting switch, and through the storage element it is intended to be connected to the blocking input of the unit for generating control signals of the inverting thyristors, characterized in that, in order to increase reliability, speed, efficiency and reduce mass and dimensions, it is equipped with a transformer rum, the primary winding of which included in series with the filter capacitor, and the secondary windings are designed for switching inverting thyristors into the shoulders according to in relation to the primary winding. L. FIG. / -T c  sS 5 1t ABOUT & i vg n I. t Oz Q 05 s at f C I t at fig. 3 Compiled by O. Mescher Kova Editor Oh, Golovach Tekhred M. Parotsay - Proofreader V. But ha 8426/57 Circulation 619 Subscription VNSh ShN State Committee of the USSR for inventions and discoveries 113035, Moscow, Zh-35e Raushsk nab., 4/5 Branch PPP Patent, Uzhgorod, Proektna St., 4 FIG.