JPH0636670B2 - Power converter control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to, for example, a GTO thyristor (hereinafter, simply referred to as GTO).
Call. ) And other controllable electric valves capable of self-extinguishing (switching elements) and ordinary thyristors that cannot self-extinguish (hereinafter simply referred to as thyristors) are connected in anti-parallel to form a reversible bridge rectifier. The present invention relates to a method of controlling a gate pulse that enables a GTO to be fired at any firing phase in a power converter.

[Conventional technology]

The applicant has previously proposed FIG. 4 (Japanese Patent Application No. 60-1446).
2, 14465) Circuit diagram showing a reversible bridge rectifier,
FIG. 4A is a waveform diagram showing the applied voltage to a certain GTO in FIG.

As shown in FIG. 4, the GTO rectifier 11 and the thyristor rectifier 12 are connected in anti-parallel to each other to form a reversible bridge rectifier, and when the GTO is conducting, the reactive current of the phase advances to the power source and flows. The control angle is adjusted, and has the following features.

(1) In a multi-phase output cycloconverter composed of a plurality of the above reversible rectifiers, the reactive current of the delayed phase generated by the thyristor and the reactive current of the advanced phase generated by the GTO are canceled and the combined power supply Reactive current is reduced.

(2) By connecting two reversible rectifiers in series, for example, when the thyristor is conducting on the one hand, the GTO is conducting on the other hand. Reactive power is reduced.

That is, the GTO is characterized in that the firing angle is controlled so that the reactive current of the advanced phase flows in order to cancel the reactive current of the delayed phase generated by the thyristor. That is, the firing angle of the GTO is in the range of 0 to 180 degrees in the case of a thyristor, but must be in the range of -180 degrees to 0 degrees (or 180 to 360 degrees). I have to. On the other hand, in order for the GTO to be able to fire, it is necessary to use the GT when the on-gate signal is given.
A forward voltage must be applied to O, but when the firing angle is in the range of -180 degrees to 0 degrees, the on-gate signal is applied to the GTO starting from the state where the load current is zero, as when starting. Is not always applied with a forward voltage. That is, in FIG. 4, assuming that the output current is passed in the direction of the arrow and the voltage is gradually increased from zero, the control angle α of the GTO rectifier 11 is set.
Is started from -90 degrees, for example. Now, in U ₁ , α =-
If an on-gate signal is given at 90 degrees,
As indicated by the solid line in FIG. (B), the U ₁ and the reverse voltage is applied, U ₁ can not be fired. Moreover, since in order to flow a current must create a closed loop power -GTO- load -GTO- power, typically on-gate signal is given to Y _1. FIG. 4A (b) shows the voltage waveform applied to Y ₁ . When U ₁ is α = −90 degrees (4th
In the point A in Fig. A), Y ₁ is a process of transition from a negative voltage to a positive voltage, and Y ₁ is ignited. When Y ₁ fires, the impedance of Y ₁ becomes almost zero, and GT
O is shared voltage applied Instead, the U ₁ is the voltage represented by the dashed line in FIG. 4A (b) is applied, also U
_{Since a} reverse voltage is applied to _1, U ₁ cannot fire.

Therefore, GT with a phase different from the originally desired firing angle
A method in which O is ignited, the GTO is once made conductive, and then an on-gate signal is given to the GTO at a desired phase can be easily considered. In other words, this is a method that utilizes the fact that once the GTO becomes conductive, a forward voltage is applied to the GTO that is next ignited by the energy stored in the inductance of the power supply, and the GTO can commutate.

[Problems to be solved by the invention]

However, turning on the GTO at a phase different from the desired firing angle at the time of starting in this manner gives an unfavorable voltage or current to the load, and it should be avoided as much as possible.

Therefore, it is an object of the present invention to apply a forward voltage to the GTO without giving harmful voltage or current to the load and enable the GTO to be ignited at any ignition phase.

[Means for solving problems]

This GT which should be ignited when the on-gate signal is given to the GTO starting from the state where the load current is zero as in the start-up
A gate signal generation circuit is provided which also fires a thyristor connected in anti-parallel with O.

[Action]

For example, in FIG. 4, assuming that U ₁ and Y ₁ are ignited when the load current is zero as in the case of starting, at this time, the thyristor connected in antiparallel with U ₁ and Y ₁ from the gate signal generating circuit. A gate signal is also given to X ₂ and V ₂ so that it is ignited. Then, by applying a forward voltage to the GTO by using the voltage generated when the thyristor extinguishes the arc, the GTO is supplied without giving harmful voltage or current to the load.
Allow the rectifier to start.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. This shows a gate signal generation circuit, which includes a point-extinguishing pulse generator 1 that forms a point-extinguishing pulse to be applied to the GTO, an ignition pulse generator 2 that forms an ignition pulse to be applied to a thyristor, and an AND gate 3. , 4, an OR gate 5, an inverter gate 6 and the like. The signal a is a signal for selecting which of the GTO or the thyristor the gate signals U to Z are to be applied in correspondence with the positive or negative of the desired current. For example, when selecting the GTO, “1”, the thyristor is selected. When it does, it becomes "0". Further, the signal b is a signal for causing the thyristor to generate a gate signal even when the GTO is selected, and becomes “1” at the time of start-up, when the current polarity is inverted, or when the current is interrupted.

The operation of FIG. 1 will be described below with reference to FIG. Incidentally, FIG. 2 is a timing chart showing an on-gate signal.

Now, assuming that U ₁ and Y ₁ are ignited as shown in FIGS. 2 (a) and 2 (f) when the load current is zero as at the start-up, the signal a is as shown in FIG. When the AND gate 3 is set to 1 "and the AND gate 3 is opened, the signal b is set to" 1 "for a predetermined time as shown in FIG. 8C to open the AND gate. Therefore, U ₁ and Y ₁ and the corresponding thyristor X ₂ , V ₂
Will be ignited as shown in (n) and (ri). Note that this is the same not only when U ₁ and Y ₁ are ignited, but also when other elements are ignited.

That is, for example, if U ₁ and Y ₁ are fired at α = −90 degrees at startup, the thyristor rectifier has α = 90 degrees.
Fired in degrees. FIG. 3A shows the voltage waveforms applied to the thyristors X ₂ (a) and Y ₂ (b), which have opposite polarities with respect to the waveforms of FIGS. 4a (a) and (b), respectively. There is. The points in FIG. 4A and the points in FIG. 3A represent the same time, and a forward voltage is applied to X ₂ when a gate signal is applied as shown in FIG. 3A (a). Therefore, this is fired. Further, when X ₂ is ignited, the voltage indicated by the broken line in FIG. 3A (b) is applied to V ₂ , which is also ignited. It should be noted that when X ₂ and V ₂ are ignited, a current having a polarity opposite to that of the desired current flows through the load, but this is only the current pulsation, and there is no particular possibility of having a harmful effect on the load. Absent. Because the output voltage waveforms are the same whether U ₁ and Y ₁ are fired or X ₂ and V ₂ are fired,
Also, the average value of the output voltage is zero.

Immediately after X ₂ and V ₂ are ignited and a minute current flows, the current immediately decreases. Although Figure 3B shows the voltage applied to the X ₂ and V ₂ at this time, a current reverse voltage is applied to the X ₂ and V ₂ after has decreased to zero, X ₂ and V ₂ are vanishing To arc. That is, from the viewpoint of U ₁ and Y _{1, a} forward voltage is applied due to this arc extinction. Therefore, if an on-gate signal is applied to U ₁ and Y ₁ , U ₁ and Y ₁ become conductive and have a desired polarity. It becomes possible to pass an electric current. FIG. 3C shows an example of output voltage and current waveforms of the power converter controlled in this manner.

In addition, although the case where U ₁ and Y ₁ are ignited has been described above, the same applies to other elements, and at the time of startup, not only from α = −90 degrees, but also from any ignition phase. can do. In addition, when the GTO is ignited to reverse the current polarity from the mode in which the thyristor is conducting, or when the on-gate signal is given to the GTO when the load current is very small and current interruption occurs, the load current is Even in the case of zero, the same control as described above is performed. In addition, when the intermittent current is very small, the intermittent current can be eliminated by providing the firing pulse to both the GTO and the thyristor regardless of the polarity of the desired load current, and the switching from the GTO to the thyristor or vice versa. It is convenient that there is no switching dead time at the time of switching.

〔The invention's effect〕

According to the present invention, the thyristor is extinguished by firing the thyristors connected in anti-parallel with the GTO to which the on-gate signal is applied, even in a phase where the GTO is generally unable to fire due to the reverse voltage applied to the GTO. There is an advantage that the GTO rectifier can be started by applying a forward voltage to the GTO by utilizing the voltage generated when arcing and without giving a harmful voltage or current to the load.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a time chart for explaining the operation of FIG. 1, FIG. 3A is a waveform diagram showing a voltage applied to the thyristor, and FIG. 3B is a thyristor. FIG. 4C is a waveform diagram showing the relationship between the applied voltage and the load current, FIG. 3C is a waveform diagram showing the output voltage and current of the power converter, and FIG. 4 is a circuit diagram showing the reversible bridge rectifier previously proposed by the applicant. The figure is a waveform diagram showing the voltage applied to a certain GTO in FIG. Reference numeral 1 ... GTO rectifier firing pulse generator, 2 ... Thyristor rectifier firing pulse generator, 3, 4 ... AND gate, 5 ... OR gate, 6 ... Inverter gate, 1
1 ... GTO rectifier, 12 ... thyristor rectifier, 13
……load.

Claims (1)

[Claims] 1. A plurality of reversible bridge rectifiers are provided in which a first rectifier made of a switching element capable of self-extinguishing and a second rectifier made of a switching element not capable of self-extinguishing are connected in antiparallel with each other, and a plurality of reversible bridge rectifiers are provided. The control angle of the first rectifier is adjusted so that the reactive current of the phase proceeds to the power supply and the reactive current of the delayed phase generated in the second rectifier is offset by this, thereby reducing the reactive power of the power supply. In the power conversion device, when an on-gate signal is applied to the first rectifier at least when the load current is zero, it corresponds to the switching element of the first rectifier to which the on-gate signal is applied and is connected in antiparallel thereto. A method for controlling a power converter, wherein an on-gate signal is also applied to a switching element of a second rectifier.