SU900402A1 - Method of control of rectifiers of three-phase bridge converter during shunting - Google Patents

Description

(5) METHOD OF MANAGING THE VENTS OF THE THREE-PHASE BRIDGE CONVERTER DURING THE PROCESS

I

This invention relates to electrical engineering, in particular, to automatic control systems for direct current transmissions.

A known method of controlling the valves of a bridge converter in the process of shunting it is used for short-term current flow during normal and emergency shutdowns and switching on of the bridge, which consists in simultaneously switching on bridge gates belonging to the same series 1.

The drawback of the device is that the valves used for shunting undergo a three-time overcurrent, as a result of which this mode is allowed only briefly.

There are various methods that implement the principle of a three-phase bridge converter in the process of shunting it with a chain of series-connected working valves. HIS PASSES

belonging to the same phase, in particular, by transferring it to a mode characterized by separate control of the anodic and cathodic group 2 valves.

With this control, one of the valve groups is supplied with a sequence of control pulses delayed relative to the moment of natural ignition of the valves on

10 switching angle d. less than 90 el. hail (which corresponds to the rectifying mode), and the other group of gates is controlled by a sequence of pulses delayed at an angle of d or greater than 90 el. degrees corresponding to the inverse mode.

This mode is known as the circular mode of the converter. He can be provided

20 by applying to the three-phase bridge converter any of two sequences of control pulses that differ from the normal sequence and have the following form: 1-4 3 L 5 1 ID. B, Hfe, 8.3. Io, B5 where the index I corresponds to the pulses of the inverse mode, B to the rectifying mode, the lower indices correspond to the number of the bridge valve. When using a sequence of control pulses (1), the cathode group of bridge gates operates in the inverse mode with turn-on angles. "1 ball valve valve d. and the anodbridge vents are in the rectifier NOI rpynmj with switching angles. Mode Let's call this mode the first circular mode of the bridge (KR-1). When using a sequence of control pulses (2), the bridge operates in the second circular mode (CR-2), characterized by the fact that the anode group of valves is controlled by inverse mode pulses from the switching angles and cathode group valves operate in the rectifying mode with switching on angles dl 2 . However, the known method has significant drawbacks. The use of only one randomly selected circular mode control pulse sequence for shunting a bridge leads in some cases to unacceptable shunting delays, and besides, the bridge cannot be shunted in emergency situations accompanied by valve failures or supply bans. control pulses on the valves belonging to the two phases of the converter transformer, which, at the time of the shunting command, flowed around the operating current of the bridge, which reduces the reliability of the device oyst The purpose of the invention is the increase of reliability and reliability. The goal is achieved by controlling the valves of a three-phase bridge converter D by shunting it by pressing the valves of one of its groups of control pulse sequences corresponding to the inverse mode, and the valves of the other group of control pulse sequences corresponding to straightening mode form synchronizing impulses for each of the converter valves, the leading front of each of which coincides with the moment of natural switching on of its own valve and the rear one - with the moment of the natural switching on of the subsequent valve and after the shunting command has been received, if there is a synchronizing pulse from one of the cathode group valves and no current in the input phase circuit, to: To which this valve belongs, the sequence is fed to the cathode group of valves control pulses, corresponding to the inverse mode, and on the anode group of valves, a sequence of control pulses, corresponding to the rectifying mode, in the presence of a synchronizing pulse one From the valves of the anode group and the absence of current in the input circuit of the phase to which the valve belongs, a sequence of control pulses corresponding to the rectifying mode is fed to the cathode group of valves, and a sequence of control pulses corresponding to the inverse mode to the anode group of valves. a synchronizing pulse, any gate valve and a current in the input circuit of the phase to which the valve belongs, for each of the valve groups both sequences are fed to them control pulses, while simultaneously switching on two valves belonging to the same phase, the control pulses are stopped. Fig. 1 shows a three-phase bridge converter circuit and a block diagram of the control of the shunting process. The circuit contains gates 1-6, logic device 7, software device 8, keys 9 12, driver 13 for control pulses corresponding to the rectifier mode, driver 1 for control pulses corresponding to the inverter mode. Fig. 2 shows a) phase voltage diagrams of the input circuit; b) a sequence of control pulses KP-1; c) diagrams of phase currents corresponding to the mode of operation with control from КР-1; d) voltage at the poles of the converter bridge corresponding to the mode of operation when controlling from the CR-L, e) sequence of control pulses of the CR-2 e) phase current diagram corresponding to the mode of operation of the KR-25 g) voltage at the poles of the converter the bridge, corresponding to the mode of operation at the offices of the KR-2.

Fig. 3 shows: a) phase voltage diagrams of the input circuit; b) synchronizing pulses of the bridge bridge a-a, c) and d) —control sequences of control pulses KR-1 and KR-2, respectively; e) shunting command signal; e) diagrams of input currents, in the absence of failures and prohibitions on the inclusion of valves, g) logical signals at the outputs of block 8; h) diagrams of input currents in the presence of prohibitions or failures to turn on the valves of phase B (and) logical signals at the input of block 8; k) diagrams of input currents in the presence of prohibitions or failures in

aza a and l) logical signals on the output of block 8.

To clarify the proposed method, the processes of shunting the bridge from the rectifying mode are considered. Without limiting the generality of the results, it can be assumed that the command to shunt dj is given in the interval V t / 1 after switching the current from valve 5 to valve 1, (V, r Vri moments of natural switching of the corresponding valves).

At that, valves 6 and 1 are open, and the phases in and a of the valve windings of the power transformer flow around the bridge current. In accordance with the interval V t Vij we set the logical synchro impulse SI 1 (similar to the interval Vj, impulse SI ij, etc.).

In the interval .- V, the logical synchro impulse of the SI 1 is equal to one, and the rest to zero, and the bridge is allowed to feed both sequences of control pulses of the circular mode (the logical signals at the corresponding output 8 of the RC x1 and KPrj are equal to one). As a result, an impulse of AND 5 is supplied to the bridge, if dl 120, or Vlu, if, as well as impulse B, ecp d d BO = where, the ignition angle of the rectifying operating mode, f is the current switching angle. These pulses do not change the state of the circuit, since valves 1 and 6 are already open, and there is no

. conditions (voltage on valve 5 is negative).

On the interval li V, the logical synchro impulse SI ij is equal to one, and the rest to zero, and it is allowed to use only the sequence of control pulses of the second circular mode (the logical signal Krl is equal to one, and КР ,, to zero).

The use of the first circular mode is unacceptable, since a control pulse B 0 of the first circular mode is generated at the indicated interval. The pulse B ij controls the valve 2 of phase C, which does not participate in the passage of current (i 0). Applying this impulse to the bridge leads to the continuation of the rectifying mode and returning the circuit to the initial state. The inverter impulses controlling the valves of the inoperative phase C, and all the impulses controlling the valves of the operating phases of the quince can be shunted. Consequently, in the interval Vni Vj, only one control impulse AND (of the second circular mode if cC 120 is supplied to the bridge. In this case, the state of the circuit does not change, since valve 6 is already open.

It should be noted that at the intervals V ,, -f Vj and Vj there are no physical conditions for shunting the bridge with valves of any phase, since the voltage at the valves 3 and 4 of the working (participating in current transmission) phases in and a and the valve 5 idle phase is negative. This fact causes a delay in shunting, regardless of the method of shunting, the maximum value of which does not exceed 120 °.

On the interval Uch4 Ud, the logical sync pulse CHj is one, the others are zero, and both sequences of control pulses are allowed. As a result, an impulse can be applied to the bridge, AND -1, if 20, or IL, if. , and also impulse В J, if d,. bo, with the impulse MQ given after the impulse Bo ,. When a control pulse is applied to the bridge, AND the state of the circuit does not change (valve 1 is on), when a pulse B is applied, the current from valve 1 passes to valve 3, as a result of which the bridge is shunted by two series-connected phase valves. 7 At the moment when the current passes to the phase valves, all pulses, including IL, are prohibited. If the 3 phase valve is prohibited or not turned on, the bridge in the interval Y ,, 1 is given a pulse HQ1 H20 ° or AND, if dL 120 °. The pulse AND of the pulse does not change the state of the circuit, and when the pulse is applied AND Q, the current switches from valve 6 to the gate (at a time 7120 on the interval Od, the state of the circuit does not change). In the V5 interval, the logical sync pulse is equal to one, the others are equal to zero, and both sequences of circular mode pulses are allowed (the logical signals KP and KP are equal to one). 8l pulses are applied to the bridge if, as well as AND, if d is 120 °, or Hj, i1 is 20 °, with pulse I1j followed by pulse Bd. When a pulse B is applied to the bridge, the current passes to the valve, regardless of whether the pulse is applied AND Q to the bridge before pulse 8 or later, or simultaneously, since the conditions for switching on the valve k are more favorable than for switching on valve 2. As a result, the bridge shunt by valves 1 and phase A. At the moment the current passes to the valves of phase a, all pulses are inhibited. For prolonged shunting of the bridge, either a shunt apparatus is also turned on, or the bridge is placed in a circular mode. When prohibiting or refusing to turn on the valves of both phases in and at the moment of applying a pulse to the bridge, the IL from valve 6 goes to valve 2 As a result, the bridge current passes through valves 1 and 2. In the interval U, the logical clock is equal to one, the rest are zero, both sequences of pulses of the circular mode (signals KR and KR) (equal to unity) are allowed. Impulses Hj are applied to the bridge. Regardless of how these pulses are located relative to each other, the current passes from valve 1 to valve 5 because the conditions for switching on valve 5 are more favorable than for valve 3. As a result, the bridge is shunted by two valves 2 and 5 of phase C, after all pulses are prohibited. The long shunting of the bridge is the same as in the previous cases. Similarly, the processes occur during the shunting of the bridge of the inverter mode, with the only difference that the physical conditions for shunting the bridge are already at the moment of giving the shunting command. Therefore, bypassing is possible without a time delay. The process of shunting does not fundamentally change when giving the command for shunting d, at the time of switching the current from one valve to another. The proposed method provides a fairly fast bypass and with the prohibition or refusal to turn on the valves of any two or one phase. The bridge is shunted by the proposed method by a device whose block diagram is depicted in FIG. Six pulses with angles included; and O-O corresponding to the rectifying mode, produces device 13, and six pulses with inverter switching on angles, device k, which control six valves of the converter bridge (1-6). On three channels through the switch 9, control valves of the cathode group are turned on with the switching angle A. (B, B and B j) produced by the device 13, and on three channels through the switch 19 on the same valves of the cathode group, control valves impulses with switching-on angle oL (I, I, and I) produced by device 1. Control valves for impulse with angle of incidence (B, Bg, and B j) generated by device 13 are applied to the anode group valves through three channels, and on three channels, through the key 12, the plant drives control pulses with an angle of incidence ((AND, AND {, and And 2) The keys 10 and 11 are controlled by a single logical signal to which the logical signal KR corresponds, and the keys E and 12 are controlled by a logical signal to which the logical signal KFij corresponds. The logical signals KPxj and KPf are generated by device 7- At the input of the device 7 six logical sync pulses (mi, mi), and three logic signals are provided, which correspond to the currents of the input phase circuits.

Logical signals KR and KRP plant on the keys 9-12 through the software device 8, specifying the mode of operation of the bridge. A logic signal corresponding to the bridge shunting command and a logical signal corresponding to the difference in the currents of the bridge and the average value of rectified currents of the input phase circuits are fed to the input of the software device.

Logic device 7 constantly analyzes the state of the bridge based on the information about clock pulses and phase currents received at its input and sends logical signals to the input of the software device 8, thereby implementing the desired control algorithm.

The proposed method of controlling the valves of a three-phase bridge converter during its shunting provides sufficient shunting operation speed and a high degree of reliability in various emergency situations.

Claims (2)

1. US Patent No., cl. 321-P, 1972. 2. The patent of Sweden (f 339509, class H 02 M 1/08, 1972. k & C V | tfj 1 | g «.atf .j. | g / | 4fi 1, f4 I ( /