JP2647204B2 - Power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a power conversion device connected via a voltmeter to a power supply system used by switching a plurality of power supply buses.

(Prior Art) FIG. 5 shows a configuration of a power converter connected to a power supply system used by switching between two power supply buses. A power supply system 5 in which a first system bus 1 and a second system bus 2 are connected via circuit breakers 3 and 4 for the respective buses;
A main circuit input transformer 6 and a control circuit transformer 9 connected to the main circuit, a main circuit 8 of a power conversion device 7 connected to the main circuit input transformer 6 to receive power, and a control circuit transformer 9, a phase control circuit 10, a motor 11 connected to the main circuit 8, and a circuit breaker 3, 4 interlocking with the on / off of the circuit breakers 3, 4 to which the voltage waveform of the power supply system is inputted and inputted. It consists of state signals 12a and 12b input to the phase control circuit.

FIG. 6 shows the configuration of the main circuit 8 of the power converter. The main circuit is controlled in phase by an output signal of the phase control circuit 10, and is a thyristor 8a1 to 8a6 that converts supply power supplied through the main circuit input transformer 6 into DC power.
DC reactor 8a1 for smoothing this DC power, thyristors 8b1 to 8b6 for converting this smoothed DC power to AC power of any frequency, commutation capacitors 8d1 to 8d6 for storing commutation energy of these thyristors 8b1 to 8b6, It is composed of commutation capacitors 8d1-8d6 and diodes 8c1-8c6 for separating the terminal voltage of the motor 11. The operation of this type of circuit is
For example, since it is described in detail in “New Drive Electronics” (published by Denki Shoin, edited by Naohiko Ueyama), Chapter 4, pp. 103-109, the description is omitted here. Next, FIG. 7 shows a detailed configuration of the phase control circuit 10. The voltage phase of the power supply system 5 is input by the control circuit transformer 9 and a filter 10 for preventing disturbance from the power supply system 5 is used.
a, a comparator 10b for converting a zero-cross of an AC signal, which is an output signal, into a pulse waveform having a duty of 50%, which is detected, and outputting the output signal and a synchronizing pulse signal from a gate pulse generator 10i described later to resistors 10c, 10b A comparator 10b, which integrates the phase difference between the output signal of the comparator 10b and the synchronization pulse signal from the gate pulse generator 10i, a resistor 10e, a capacitor 10g and an amplifier 10f. Oscillator 10h that oscillates at an arbitrary frequency according to the output signal,
It comprises a gate pulse generator 10i whose operation time is determined by the oscillation frequency.

Now, when switching from the system 1 bus to the system 2 bus,
Consider a case where the circuit breaker 3 for the first system bus is closed and the circuit breaker 4 for the second system bus is closed while the circuit breaker 3 for the first system bus is closed. At this time, the voltage waveform on the secondary side of the main circuit input transformer 6 may be transiently asymmetric with respect to the zero point voltage as shown in FIG. This is because the magnetizing phenomenon of the voltage core occurs. The duration of this transient is the phase difference of the bus,
It is not always constant because it varies depending on conditions such as the voltage phase when the circuit breaker is turned on.

No power is supplied to the power converter between the time the circuit breaker 3 is opened and the time the circuit breaker 4 is closed. In addition, during the transitional state, the voltage phase input to the phase control circuit of the power converter and the voltage phase input to the main circuit do not match, so that the phase control of the power converter cannot be performed. Therefore, the power converter is set in advance for a certain period of time equal to or longer than the maximum time that can be expected in the transient state, and is operated from the time when the circuit breaker 3 is opened to the time when the circuit breaker 4 is closed and the above-mentioned certain time elapses. Is controlled to stop.

(Problems to be Solved by the Invention) However, the conventional power converter having the above-described configuration has the following problems.

(1) Even if the above transient state converges in a shorter time than the set value, the operation is not restarted until a preset time elapses. Therefore, when a quick restart is required, a useless waiting time may be generated.

(2) When the transient state lasts longer than the set value, the thyristor of the main circuit is triggered in a state where the voltage phase input to the phase control circuit of the power converter and the voltage phase input to the main circuit do not match. Therefore, an overcurrent, an overvoltage, and the like occur.

The present invention has been made in view of the above problems, and is a power converter connected to a power system to be used by switching a plurality of power buses via a transformer. It is an object of the present invention to provide a power conversion device that does not generate overcurrent, overvoltage, and the like while limiting power consumption.

[Configuration of the Invention] (Means for Solving the Problems) In order to achieve the above object, a first aspect of the present invention is to set a positive-side amplitude of a voltage waveform of an AC power supply supplied to a power converter to a zero-point voltage. A first means for detecting, a second means for detecting a negative amplitude of the voltage waveform with respect to a zero point voltage, and a third means for obtaining a difference between an output of the first means and an output of the second means. And a fourth means for comparing the output of the third means with a predetermined value and outputting the result. Further, a second invention is a first means for detecting a voltage waveform of an AC power supply supplied to a power conversion device, a second means for measuring a time interval at which the voltage waveform coincides with a zero point voltage, and And a third means for comparing the output of the means with a predetermined value and outputting the result. Further, a third invention is a first means for detecting a voltage waveform of an AC power supply supplied to a power converter, a second means for detecting a DC component of the voltage waveform,
The apparatus is provided with third means for comparing the output of the second means with a predetermined value and outputting the result.

(Operation) In the present power converter, the secondary-side voltage waveform of the main circuit input transformer is detected, and whether or not the transient state has ended is detected by any of the following (1) to (3). I do.

(1) The difference between the positive and negative amplitudes of the secondary voltage waveform with respect to the zero point voltage is compared with a predetermined reference.

(2) The time interval at which the secondary voltage waveform matches the zero point voltage is compared with a predetermined reference.

(3) The detected value of the DC component included in the secondary-side voltage waveform is compared with a predetermined reference.

In any of the above cases (1) to (3), when the detected value falls below the reference, it is determined that the transient state has ended, and a restart permission signal is output to the phase control circuit of the power converter. As a result, the power converter can be restarted at the same time that it is in an operable state, so that unnecessary waiting time is eliminated.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numerals 1 to 11 and reference numerals 12a to 12b are the same as those in FIG. 13a to 13b are 2 of the main circuit input transformer 6 respectively.
The positive voltage amplitude of the next voltage waveform, the negative amplitude detection means, 14 is a means for detecting the difference between the positive amplitude and the negative amplitude, 15 is comparing the amplitude difference with a predetermined reference, the amplitude This is a means for outputting the activation permission signal 16 when the difference is smaller. The start permission signal is input to the phase control circuit 10 of the power conversion device 7.

The case of switching from the first system bus 1 to the second system bus 2 will be described below. When the circuit breaker 3 for the first system bus is closed and the circuit breaker 3 for the second system bus is opened from the open state, the state of the circuit breaker input to the phase control circuit 10 of the power converter 7 is changed. The signal 12a changes to 12a, 12b
Both are "open", and the power converter stops operating. Next, when the circuit breaker 4 is closed, the state signal 12b of the circuit breaker becomes "closed", and the power converter enters a restart preparation state waiting for the start permission signal 16. On the other hand, the positive and negative amplitudes of the secondary voltage of the main circuit input transformer 6 are detected by the detecting means 13a and 13b, and after the difference is obtained by the difference detecting means 14, the comparing means
Entered in 15. The comparing means 15 compares the input value with a preset reference, and outputs an activation permission signal 16 when the input value is smaller. When the activation permission signal is input to the phase control circuit of the power converter, the power converter restarts. FIG. 2 shows a timing waveform of the above operation. 1 is a voltage waveform of the power supply system 5, 2 is a secondary-side voltage waveform of the main circuit input voltage machine 6, 4 is an operation timing according to the present invention, and 5 is an operation timing according to the conventional example.

As described above, according to the present invention, the time during which a power converter connected to a power supply system used by switching a plurality of power supply buses via a transformer stops operation at the time of bus switching is minimized, and Current and overvoltage can be prevented from being generated.

Another embodiment of the present invention is shown in FIGS. FIG. 3 shows a means for detecting the secondary voltage waveform of the main circuit input transformer instead of the means 13a and 13b for detecting the positive amplitude and the negative amplitude in FIG.
FIG. 4 shows an example including a means 18 for measuring a time interval at which the output voltage waveform of the detection means coincides with the zero point voltage. FIG. 4 shows the detection means 13a, 13b of the positive amplitude and the negative amplitude in FIG. Instead, means for detecting the secondary side voltage waveform of the main circuit input transformer, means for detecting the DC component of the output voltage waveform of the detecting means,
This is an example including:

[Effects of the Invention] As described above, according to the present invention, the time during which the power conversion device connected to the power supply system used by switching a plurality of power supply buses via the transformer stops the operation when the buses are switched is reduced. It is possible to minimize the occurrence of overvoltage, overcurrent and the like.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of operation waveforms of the present invention, and FIGS. 3 and 4 show other different embodiments of the present invention. Configuration diagram, fifth
FIG. 6 is a configuration diagram of a conventional example, FIG. 6 is a configuration diagram of a main circuit of the power conversion device of FIG. 5, and FIG. 7 is a configuration diagram of a control circuit of the power conversion device of FIG. 1 ... 1 system bus, 2 ... 2 system bus, 6 ... main circuit input transformer, 13a ... positive amplitude detection means, 13b ... negative amplitude detection means, 14 ... subtraction means, 15 ... Comparison means, 16 ... activation permission signal, 17 ... waveform detection means, 18 ... time interval measurement means, 19 ... DC component detection means.

Claims (3)

(57) [Claims] 1. A power converter in which AC power is supplied by selecting either one of an AC bus or the other AC bus via a circuit breaker, wherein an AC power supply supplied to the power converter is provided. A first means for detecting a positive amplitude of the voltage waveform with respect to the zero voltage; a second means for detecting a negative amplitude of the voltage waveform with respect to the zero voltage;
A third means for calculating a difference between the output of the second means and the output of the second means, and comparing the output of the third means with a predetermined value, and generating an output signal when the difference is equal to or less than a predetermined value. A fourth means for shutting off the circuit breaker of the one AC bus and switching on the circuit breaker of the other AC bus to switch the AC input of the power converter, and turning on the circuit breaker of the other AC bus After that, the operation of the power converter is restarted by the output signal of the fourth means. 2. A power converter in which either one of the AC buses or the other AC bus is selected via an interrupter to be supplied with AC power, wherein an AC power supply supplied to the power converter is provided. First means for detecting a voltage waveform;
A second means for measuring a time interval at which the voltage waveform coincides with the zero point voltage, and an output signal for generating an output signal when a difference between the output of the second means and a predetermined value is smaller than a predetermined value. In the case where the circuit breaker of the one AC bus is shut off and the circuit breaker of the other AC bus is turned on to switch the AC input of the power converter, after the circuit breaker of the other AC bus is turned on. The power converter according to claim 3, wherein the operation of the power converter is restarted by the output signal of the third means. 3. A power converter in which AC power is supplied by selecting either one of the AC buses or the other AC bus via a circuit breaker. First means for detecting a voltage waveform;
A second means for detecting a DC component of the voltage waveform detected by the first means, and comparing an output of the second means with a predetermined value, and when the difference is equal to or less than a predetermined value, outputting an output signal. A third means for generating power, wherein when the circuit breaker of the one AC bus is shut off and the circuit breaker of the other AC bus is turned on to switch the AC input of the power converter, the other AC bus is cut off The power converter, wherein the operation of the power converter is restarted by an output signal of the third means after the device is turned on.