JPS5910152B2 - How to control cycloconverter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a cycloconverter configured by connecting a plurality of unit converters including self-excited thyristor converters in antiparallel relation to a load.

FIG. 1 is a configuration diagram showing an example of a cycloconverter configured by combining unit converters, and FIGS. 2 a and b are detailed diagrams showing the specific configuration of each converter in FIG. 1. .

In FIG. 1, Al and A2 are separately excited thyristor converters, respectively, and as shown in FIG. Consisting of thyristors U-Z, B1 and B2 are each self-excited thyristor converters, and as shown in Fig. 2, six main thyristors UM-ZM connected in a three-phase bridge and a forced commutation circuit. It is equipped with

As is well known, the forced commutation circuit includes a commutating capacitor Cu, a commutating reactor Lu, an auxiliary charging thyristor UQ, and an inverting quencher common to the upper group main thyristors UM to WM.
Consists of arc thyristor Up, commutating capacitor CD common to lower group main thyristors XM to ZM, commutating reactor LD, auxiliary charging thyristor LQ, inverting arc-extinguishing thyristor Lp, and commutating capacitor charging diode bridge Du-D2. has been done. Note that R1 and R2 are dipping resistors. By connecting these unit converters as shown in Figure 1, and operating the separately excited converter at a slow phase control angle and the self-excited converter at a leading phase control angle, The reactive power that the cycloconverter takes in from the power supply system can be reduced to substantially zero. A so-called reactive power compensation type cycloconverter can be obtained. Each unit converter constituting such a cycloconverter is divided into Al and Bl, which operate on each positive half-wave of the output current (load current), and A2 and B2, which operate on each negative half-wave of the output current (load current). Switching can be done, for example, by determining the polarity of the output current.
After confirming that the output current has become zero, the current switching command circuit P selects one of the converter groups.

On the other hand, the output voltage or output current of a cycloconverter can be controlled by the firing phase or gate pulse given to each thyristor's power supply voltage, but in order to obtain a good sine wave output current, it is necessary to At the time of cycle switching or when a current switching command is given, it is necessary for the cycloconverter to output an output voltage that is at its full capacity.

In other words, if the output voltage phase of the self-exciting converter becomes negative polarity during current switching, the cycloconverter will not generate an output voltage even if the gate pulse is applied until the output voltage phase becomes positive polarity. Therefore, this time is wasted. Therefore, the present invention has been made in view of the above, and it is an object of the present invention to immediately obtain the maximum output voltage that the cycloconverter can output immediately after changing the polarity of the output current in the cycloconverter. purpose.

The above object, according to the present invention, includes a main thyristor bridge, a diode bridge sharing an AC terminal with the main thyristor bridge, and a commutating capacitor connected between the corresponding DC terminals of both bridges. , an inverting arc-extinguishing thyristor connected in parallel to each commutating capacitor in a series relationship with the diode in forward polarity, and an inverting arc-extinguishing thyristor inserted in a closed loop between each commutating capacitor and the inverting arc-extinguishing thyristor. In a cycloconverter that supplies desired AC to a load by switching control of multiple unit converters, including a self-excited converter consisting of a current reactor, self-excited conversion By generating an additional firing pulse that simultaneously fires the inverted extinguishing thyristor at the beginning of operation, the power supply voltage rectified by the diode bridge becomes the output voltage of the self-exciting converter. This is achieved by making it occur as follows.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a schematic configuration diagram showing an embodiment of the present invention.

In the figure, the gate pulse generation timing is determined by comparing the phase control signal SP, which is created by comparing the current value of the output current with the target value, and the synchronization signal SY (u-z), which is created from the power supply voltage. a comparator 1 that receives the output of the comparator 1 and operates for a time corresponding to 1200e1 (electrical angle) to output a pulse signal; and a flip-flop 2 that receives the switching command signal SS and adds a certain time width. The additional pulse generating circuit 4, which generates a pulse signal and is composed of, for example, a monostable multi, performs an OR operation on the output of the monostable multi 5 that receives the output of each flip-flop 2, and the additional pulse signal, and outputs the output as shown in FIG. 2b. Inverted arc-extinguishing thyristor U shown in
OR circuits 31 and 32 are provided for supplying signals to the gates of p and Lp.

When self-exciting converters are provided exclusively for positive and negative polarities, a gate (not shown) at a subsequent stage selects which self-exciting converter the ignition pulse is guided to. Therefore, when the switching command signal SS is issued, the predetermined upper group and lower group main thyristors UM-WM and XM,Z determined by the place card removal control signal SP and the synchronization signal SY are
Gate pulses are sequentially supplied to each of M in a predetermined phase order, and the gate pulses are supplied only to either one of the inverted arc-extinguishing thyristors Up or Lp via the OR gate 3 or 32. be done.

Furthermore, in this invention, the inverted arc-extinguishing thyristor Up, Lp
Since additional pulses are applied to the switch via the OR circuits 31 and 32, when a specific main thyristor determined at that time becomes conductive at the time of generation of a switching command, two inverted arc-extinguishing thyristors Up , Lp conduct at the same time, and based on this, the diode bridge Du-
The power supply voltage rectified by Dz is connected to both thyristors Up,
It appears between the output terminals via Lp, and as a result, the cycloconverter outputs the maximum output voltage at that time. In addition, the inverted arc-extinguishing thyristor Up that was triggered at the same time
, Lp is extinguished using a commutating capacitor Cu (CD) and a reactor Lu (LD) in the same manner as in a well-known ordinary commutating circuit. As described above, according to the present invention, it is possible to eliminate wasted time during switching operation of the converter with a simple circuit configuration.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an example of a cycloconverter configured by combining a self-excited converter and a separately-excited converter, and Fig. 2 shows a specific configuration of the self-excited converter and separately-excited converter. The detailed diagram, FIG. 3, is a schematic configuration diagram showing an embodiment of the present invention. Explanation of symbols, Al, A2...Separately excited converter, B,,
B2...Branch converter, U-Z, UM-ZM...
...Main thyristor, Up, Lp...Inverting arc-extinguishing thyristor, UQ, LQ...Auxiliary charging thyristor, CU, CD...Commuting capacitor, Lu, L
D... Commutation reactor, Du-Dz...
・Commuting capacitor charging diode, Rl, R2...
...Resistor, 1...Comparator, 2...Flip-flop, 31, 32...OR circuit, 4
...Additional pulse generation circuit, 5... Monostable multi.

Claims (1)

[Claims] 1 A main thyristor bridge, a diode bridge that shares an AC terminal with the main thyristor bridge, a commutating capacitor connected between the corresponding DC terminals of both bridges, and a series relationship with the diode with forward polarity. The converter includes a self-excited converter consisting of a reversing arc-extinguishing thyristor connected in parallel to each commutating capacitor such that In a cycloconverter that supplies a desired alternating current to a load by switching control of a plurality of unit converters, among the converters that should be newly operated for load current switching, for a self-excited converter, the above-mentioned inverting arc-extinguishing thyristor is installed at the beginning of operation. Control of a cycloconverter characterized in that the power supply voltage rectified by the diode bridge is generated as the output voltage of the self-exciting converter by generating additional firing pulses that are fired at the same time. Method.