SU1660118A1 - Inverter with emergency current protection - Google Patents

Description

The invention relates to electrical engineering, in particular to the protection of the dependent inverter from emergency currents during rollovers. The aim of the invention is to improve the reliability of the inverter. The device contains a synchronization unit 1, drivers of 2 bursts of pulses connected to the control inputs of thyristor 6kloy 3 of thyristor bridge 4 with system 8 of pulse-phase control, generator of 10 pulses that is connected to control inputs of thyristor blocks 3 via controlled keys

FIG. /

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11, connected in pairs in parallel, a reacting body 9 consisting of a trigger 14, an element OR 15, controlled keys 18 for protection and 20 bypassing, delay elements 16, 17, 21 that determine the starting points of the controlled shunt element 7 connected in parallel to the current-limiting reactor 5, and forming signal to turn off the switch.

The shunting of the current-limiting reactor 5 occurs in the time interval when the counter-EMF of the inverter is greater than the emf of the DC source. As a result, the rate of reduction of the emergency current is much greater than the rate of rise of the current at the beginning of the emergency process. The divergence of the switch contacts occurs at the moment of the minimum current value. 1 hp ff, 2 ill.

The invention relates to electrical engineering and can be used to protect against emergency currents driven by the inverter network, in particular, used in the traction drive. five

The purpose of the invention is to increase the reliability of the inverter.

Figure 1 shows a diagram of an inverter with a device for protection; figure 2 - timing diagrams explaining his work 1.

The device contains a synchronization unit 1, the input of which is connected to the leads for connecting a three-phase AC network, and six outputs are connected every 1 to the input of one of six drivers 2 pulses, the outputs of which are connected to the control input of the corresponding thyristor unit 3. Each of six thyristor blocks 3 is the arm 2 of the thyristor bridge 4 of the inverter, the AC terminals of which are connected to the terminals for connecting a three-phase voltage source (a converter transformer, not shown in the drawing), and 2 DC terminals through the current limiting reactor 5 and switch 6 are connected to the DC terminals for connection to the DC network (for example, to the DC busbars of the traction substation connected to the contact network). In parallel with the current-limiting reactor 5, a controlled shunting element 7 is connected. The switching-on control of the thyristors of the inverter bridge 4 and phase C is controlled by the unit 8 of the pulse-phase control (the communication of the unit 8 with the synchronization unit 1 by feedback sensors, etc. are not shown).

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The blocking input of the unit 8 and the control input of the controlled shunt element 7 and the switch 6 are connected to the corresponding outputs of the reacting body 9, the Generator 10 pulses are output ² connected to the control inputs

thyristor blocks 3 through controlled keys 11 connected in pairs in parallel. The signal passing circuit between the outputs of the formers 2 and the control inputs of the thyristor blocks 3 includes current sensors 12, and a current sensor 13 is included in the circuit between the output of the generator 10 and the keys 11. Block 9 is a trigger 14, the first input connected to the output of the sensor 13, the output to the input of the element OR 15, the inputs of the first delay element 16, the second element of the delay line 17 and the inhibiting input of the block 8 of the pulse-phase control.

The output of the first delay element 16 is connected to the control input of the protection key 18 connected between the generator 10 input and the input of the shutdown unit 19 of the switch 6. The output of the second delay element 17 is connected to the control input of the shunting key 20 connected between the generator 10 output and the control input of the shunting element 7 The outputs of the emergency state sensors (not shown) are connected to the control input of the shutdown key 18 and the second input of the logic element 15, the output of which is connected to the control circuit of switching devices and an inverter (not shown).

The control inputs of the keys 11 are connected to the outputs of the respective current sensors 12 so that one of the pair of keys 11 is connected to the control input of this thyristor unit, the input is connected to the control circuit of the antiphase thyristor unit, and the second to the control circuit of the thyristor unit, which during normal operation the inverter begins to conduct current at a time corresponding to the phase angle 2tg / 3 after the start of the flow of current through the thyristor unit. For clarity, the connection of the thyristors state control circuits of each unit with their emergency control circuits is represented by the correspondence table:

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Circuit control state-emergency circuit

yaniya governing 31 hell, C5 C2 C5, WB up Wb, E1 hell E1, C2 C5 C2, OT WB OT. hell

The principle of operation of the device is as follows.

If a current commutation disturbance occurs (the beginning of the emergency process), for example, between the thyristors and C5 (Fig. 2) and the current through the thyristor continues to flow until the test signal arrives, at this moment t ₀ control pulses are sent to the thyristors, anti-phase, . which, before this momeit, conducted a current, in this case, on the thyristors of the in-line and under the voltage of the windings of the converter transformer, to which the switching thyristors are connected, the current is switched to the newly connected thyristors and the inverter’s counter-EMF curve (figure 1) is formed from this moment line voltage curve, antiphase to the one that determined the back-EMF at the beginning of the emergency process. Due to the change of polarity of the inverter's back-emf, the current in the dc circuit noticeably increases until the moment Gd, until the instantaneous value of the back-emf is above the emf of the external source. The shunt resistor is already connected to the smoothing reactor by that time. The resistance of the resistor is chosen as such; so that the voltage drop on the shunting element was as low as possible (zero in the limit). When the reactor is shunted, the current in the DC target under the action of the difference between the counter-EMF and the EMF of the external source decreases rapidly during the time interval from dd to T5 and if the current was relatively small before the start of the emergency process, it may cease by ί5 and then arcless current quenching occurs. If the current was large enough, this will not happen, but by the time 'ΐδ the current value will be less than it was at the time _ο . Therefore, the break of the current by the switch occurs faster and with a significantly lower energy release in the arc as compared with the case when the current-limiting reactor was not shunted. The moment of giving the signal to switch off the switch is selected taking into account its own time Xb. In (from the moment of actuation until the beginning of the divergence

contacts), determined by the mechanical properties of the switch, so that the moment of contact divergence approximately coincides with the moment 5.

The given sequence of operations allows to ensure the minimum current value by the time of the breaker contacts divergence, and in many cases arc-free quenching of the torus, without using additional power equipment.

The device works as follows.

At the outputs of synchronization unit 1, six sinusoidal voltage signals are formed, in which they form a symmetrical six-pointed star with angles between adjacent π / 3 beams. After going through the zero of each voltage sinusoid, the corresponding driver 2 produces a test signal in the form of a bundle of high-frequency voltage pulses (in the form of shaded rectangles ). Synchronization of the generators 2 is performed in such a way that during normal operation of the inverter these signals arrive at each thyristor unit 3 at intervals when its thyristors are locked, and, as a result, there is no current at the output of each driver 2. At the outputs of each current sensor 12 signals neti keys 11 close · (open). The generator 10 continuously produces voltage pulses, but since all the keys 1 ι are closed, there is no current at the output of the generator 10, there is no signal at the output of sensor 13, trigger 14 is in the initial state, at its output a signal is "0", at the outputs of all delay lines the signal "0", keys 18 and 19 are closed. If there is no current switching from one phase to another and one of the thyristor blocks (for example, charging) continues to conduct current after the moment when the next signal arrives at this block, a control appears between the output of driver 2 and the control input of the thyristor block current, which causes the appearance of a signal at the output of current sensor 12, as a result of which the corresponding keys 11 are opened (closed) by connecting generator 10 to the control inputs of the corresponding thyristor 6 (in this example, a1 and le). Under the action of a linear voltage (in this case, voltage av), the previously switched on thyristor blocks (Vz and Hell) and the antiphase (V and β) turn off. Simultaneously with the appearance of a current pulse at the output of the generator 10, a signal appears at the output of the sensor 13, which switches the trigger 14 and

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At its output, a signal "1" appears, which causes the appearance of a signal "1" at the output of the element OR 15, leading to blocking the possible reclosing of the converter until the end of the inverter alarm state.

The appearance of the signal "1" at the inputs of the elements 16 and 17 of the delay leads to the appearance of the signal "1" after the time An at the control input of the switch 18 and after time / kg at the control input of the switch 20, the first of which activates switch 6 through block 19, and the second includes a shunting element 7 of the current-limiting reactor 5. When the reactor is bridged, the current in the inverter's DC circuit in the interval of -4 -15 rapidly decreases under the action of the difference between the inverter's counter-emf and the external voltage of the external DC source, and the switch 15 opens. Xia. After the occurrence of the signal "1" at the output of the second delay line 17, after a time Δΐ3, the signal "1" appears at the output of the third delay line 21 and at the second input of the trigger 14, which returns to the initial state. After that, all elements of the reacting organ return to the initial state. 9.

Thus, the device allows to significantly reduce emergency currents that are switched off by switching devices, and, consequently, to increase the service life and increase the reliability of the converter unit as a whole.

Claims (2)

Claim 1. Inverter with protection against emergency currents, containing power thyristor controlled blocks, equipped with control and control inputs and connected in a three-phase bridge circuit, a pulsed-phase control unit with a control input, the outputs of which are connected to the control inputs of the corresponding thyristor controlled blocks, a pulse shaping unit, synchronous with linear switching voltages, the input of which is connected to the leads for connecting a three-phase AC network, equipped with outputs on the number of thyristic pny controlled blocks connected to the inputs of the corresponding pulse shapers, a pulse generator and the executive body of protection, characterized in that, in order to increase reliability, six pairs of controlled keys and seven current sensors are introduced, the pulse shapers made in the form of pulse shapers and their outputs through the input circuits of the corresponding current sensors connected to the control inputs of the corresponding thyristor controlled blocks, the output of the pulse generator through the input The circuit of the seventh current sensor is connected to the inputs of all controlled keys, the outputs of each pair of which are connected to the control inputs of the corresponding thyristor controls In this case, the control inputs of the controlled keys in each pair are connected to the outputs of current sensors connected to the control inputs of the thyristor controlled blocks, respectively, antiphase and entering into operation with delay 2Tg / 3 with respect to the thyristor controlled block connected by the control input the outputs of the controlled keys of this pair, and the output of the seventh current sensor is connected to the input of the protection executive. 2. Invertoropop.1, which differs in that the protection executive is made in the form of a trigger, three delay elements, two key elements, an OR element and a circuit breaker connected in series to the circuit breaker with a shutdown unit and a current limiting choke the input of the protection executive is connected to the first input of the trigger, the output of which is connected to the first input of the OR element, which controls the input of the pulsed-phase control unit and the inputs of the first and second elements s, the output of the pulse generator is connected respectively via the first and second key elements to the control inputs of the shunt element and the switch-off unit, the output of the first delay element is connected to the control input of the first key element and through the second delay element is connected to the second trigger input, and the output of the second key element element is connected to the second input of the element OR “control input of the second key element. 1660118 Fi.g.2