SU1196997A1 - Method of protection of power electric converter - Google Patents

Description

The invention relates to electrical engineering and can be applied to protect electrical current transducers, voltage or frequency from possible damage, for example. breaks in power circuits and short circuits.

The purpose of the invention is the expansion of the scope.

FIG. 1 shows the waveforms of the signal of a good converter; in fig. -2 - the same, and at some point in time (point A) an open thyristor circuit occurs. converter; in fig. 3 is an example of a comparison of the above-mentioned signals when at the time point A there is a short circuit of the anode-cathode circuit of the power thyristor of the converter; in Fig. · 4 is a diagram of the device for implementing the method of protection of a power electric converter.

The device (Fig. 4) contains an auxiliary low-current thyristor switch 1 current, the circuit of which is similar to that of the power thyristor switch 2 of the main transducer 3 to be protected. The input of the auxiliary switch 1 is connected to the input of the main protected transducer 3 of the auxiliary switch 3 connected to unit 4 controls the main converter 3. At the output of the auxiliary converter 1, a circuit 5 is provided, which is a model of the real load 6 of the main transducer educator 3.

To the outputs of the main and auxiliary thyristor switches are connected essentially the same nodes 7 and 8 of the selection of the same harmonic voltage components. The outputs of both of these nodes are connected to the inputs of the element 9 of the comparison signals. At the output of this element provides a threshold element 10.

Its output is connected to the tripping device of the power circuit breaker 11 and the element of prohibiting the supply of unlocking pulses of the control unit 4 of the main converter 3.

The method is as follows.

The variable component of the rectified voltage taken from the output of the converter depends on the state

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its power circuits (output parameter ν _Β Μ _Χ ) · The variable component of the rectified voltage, modified in the same way as mentioned, does not depend on the state of the power circuits of the converter (reference parameter ν _οη ).

During normal operation of the transducer (Fig. 1), the output and reference parameters are equal in amplitude, phase, shape, frequency, and when compared, subtracted. Their resulting signal is practically absent (ν _ρ = 0). Therefore, there is no output signal of the threshold protection element (ν _? = 0).

With an open circuit in at least one of the power thyristor of the converter (point A in Fig. 2) or a short circuit at -the (point A in FIG. 3)

20, the parameters of the output and reference signals differ significantly ( _{Vb)) 1} / ν _οπ ) and the signal of their difference ν _ρ is different from zero. This results in the operation of the executive threshold element of protection of the power converter * (ν ₃ = 0).

The device (Fig. 4) operates as follows.

During operation of the converter 3, its control unit 4 simultaneously opens the next thyristor of the main power switch 2 and the corresponding low-current thyristor of the auxiliary switch 1. When the circuits of switches 2 of 35 and 1 are in good order and their thyristors at the outputs of both voltage switches change in time completely equally and contain the same spectrum of harmonic components. Nodes 7 and 8 emit harmonic components. same frequency. At their outputs, voltages of the same frequency and amplitude are produced. Due to this, two completely identical signals are brought to the comparison element 9. Therefore, with good switches 2 and 1 and the normal unlocking of all their thyristors at the output of element 9, there is no signal.

If the power circuit of switch 2 fails, for example, an open circuit, short circuit, unplugging of one or several power lines or ⁵⁵ or similar damage in the auxiliary switch 1, the voltage at the outputs of the switches 2 and 1 changes in time neod3

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nakovo. Because of this, they have different amplitudes of harmonic components of the same frequency. Now, two different signals are fed to reference element 9.

The parameters of elements 7 and 8 are configured in such a way that when one of the converters 2 or 1 fails, the signals to the element 9 sig are so different from each other that they appear at its output

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signal sufficient to switch the threshold element 1O. _hours worked, the element delivers a signal to the control unit 4, whereby

5, unlocking pulses are removed in all operable thyristors of switches 2 and 1. In addition, element 10 sends a signal to the circuit breaker 11, which performs a protective disconnection of the network with a damaged converter.

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Claims (1)

METHOD OF PROTECTION OF POWER ELECTRIC CONVERTER, which consists in measuring the output electrical parameter the converter, form the reference parameter, select the variable components of the measured and reference parameters, compare them with each other and, if the difference between the parameters exceeds a given value, disconnect the converter from the power source, characterized in that, in order to expand the application, the electrical parameter is measured on the input of the converter, change it in time similarly to the change in time of the output parameter of the intact converter and is used as a reference parameter. FIG. one > one