JP2553511B2 - Control device for thyristor converter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable speed control device, and more particularly to a control device for a thyristor converter that shortens the switching time at the time of forward / reverse switching.

[Conventional technology]

In the current direction switching by the variable speed control device of this type, the current direction is switched after detecting that the current flowing through the electric motor has become zero. In other words, when the current flowing through the motor decreases and is intermittent, this is detected by the current zero detector, and after surely detecting the current zero, the gate signal of the thyristor bridge operating for a certain period of time is output. After blocking, the gate block signal of the opposite side thyristage was released.

[Problems to be solved by the invention]

However, in the conventional device, the voltage recovery capability of the thyristor itself cannot be directly detected and is predicted.Therefore, it is necessary to sufficiently secure the block state of the bidirectional bridge.
It is necessary to provide TD time. Therefore, in the conventional device, a dead time is generated for a predetermined time each time the current direction is switched. This dead time becomes a problem especially when the torque direction of the electric motor, that is, the current direction is switched at high speed.

An object of the present invention is to eliminate the possibility of anti-parallel short-circuiting and shorten the switching time by performing a gate block on a bridging device operating at a current below a specified value and ensuring a period for blocking both bridging. The purpose of the present invention is to provide a control device for a thyristor converter.

[Means for solving problems]

The present invention, which solves the above problems and achieves the object, includes a positive side bridge circuit and a negative side bridge circuit, and controls a thyristor converter having a reversible thyristor bridge circuit that supplies a current in a forward and reverse directions to a load. In the device, a gate signal generation unit that outputs a gate signal to each thyristor of the reversible thyristor bridge circuit, a current detection unit that detects a load current, and an anode-cathode voltage of each thyristor of the reversible thyristor bridge circuit. A gate of the bridge circuit in operation of one of the positive side bridge circuit and the negative side bridge circuit when the voltage detection means and the detection outputs of the current detection means and the voltage detection means are taken in and the load current becomes a predetermined value or less. Stop the signal supply,
And a control means for controlling the gate signal generating means so as to confirm the recovery of the voltage blocking capability of the thyristor of each arm and start the supply of the gate signal to the other inoperative bridge circuit. Converter control unit.

[Action]

When switching the current, the gate signal of the operating bridging circuit is blocked when the load current falls below a specified value. In addition, the voltage of all thyristors is monitored, and when this is restored, the block is released.

In this way, the current switching time becomes extremely short.

〔Example〕

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

FIG. 1 is a block diagram showing a reversible speed controller using a stationary Leonard to which an embodiment of the present invention is applied.

In FIG. 1, 1 is a three-phase power supply (PS), 2 is a reversible thyristor (THYB) consisting of 6-arm thyristors (P _{1 to} P ₃ , N _{1 to} N ₃ ) connected in antiparallel, and 3 is a direct current. Electric motor (DC
M), 4 is a current detector (CS), 5 is a speed sensor (SS), 6 is a speed controller (SC), 7 is a minor current controller (CC), 8 is a gate pulse generator (GPG), 9 Is a logic circuit (LOGIC) for switching the current direction, 20 is a current level detector (CLS), and 21 is a thyristor voltage blocking recovery detector (VRS).

The operation of the embodiment having the above configuration will be described with reference to FIG.

2 (I) and (II) are time charts for explaining the operation of the embodiment together with the operation of the conventional example. Ia
Is the load current of DCM3, CR is the polarity of the current direction generated by processing the current command CR, that is, the bridge to be operated.Here, CR ₀ is the positive bridge when this is positive, and the reverse when it is negative This shows that the side bridge is operated. FG
Is the area where the positive side bridge operates, RG is the area where the reverse side bridge operates, and these signals are output from LOGIC9.
Further, CZS indicates the operation of the conventional current detector, and CLS _P and CLS _N indicate the operation and output signals of the current level detector 20, which indicate the positive side and negative side current level signals, respectively. . In addition, VRS indicates the operation of the thyristor voltage blocking recovery detector 21 and indicates a voltage recovery signal between the thyristor anode (A) and the cathode (K).

Then, from the left side, the positive side current level signal below the specified value
Block the gate signal of the thyristor in operation by CLS _P , and then the voltage recovery signal VR between AK of the thyristor.
The block on the opposite side of the thyristage is released after S is established sufficiently. Switching from the reverse side bridge to the positive side bridge is performed in the same manner as the reverse side current level signal CLS _N.
Block the gate signal of the operating thyristor, and then release the block of the positive side thyristor by establishing the AK voltage recovery signal VRS between the thyristors. In this way, the current direction can be switched without the time delay TD as shown in the figure (see FIG. 2 (1)).

FIG. 3 is a block diagram showing an example of a voltage recovery detection circuit between thyristors AK. 30 is one arm of anti-parallel connection thyristor, 31 is light emitting diode driver circuit (DRV), SD
Is a light emitting diode, 32 is an optical fiber (LF), 33 is an amplifier circuit (AMP), RD is a light receiving diode, and 34 is a comparison circuit. When the voltage across the thyristor A-K of 30 is well established, but to obtain a high (H _IgH) level signal VR.

FIG. 4 is a block diagram showing the configuration of the present invention in the case of a reversible speed control system using a 12-phase rectifying static leonard. Gate pulse generators GPG ₁ and GPG ₂ are used in correspondence with the thyristors THYB ₁ and THYB ₂ , respectively, but the operation of the control circuit CTR is the same as in FIG. Here, 12 AK voltage signals are applied as inputs to the thyristor AK voltage recovery circuit VRS.

FIG. 5 is a block diagram showing a configuration example when the present invention is applied to a reversible speed control system for an induction motor (IM) using a 12-phase rectification type cycloconverter. Variable frequency power supplies for each phase of IM are bridges THYB _U-1 and THYB for U phase.
_{The U-2} and V phases are supplied by the bridges THYB _V-1 and THYB _V-2 and the W phases are supplied by bridges THYB _W-1 and THYB _W-2 .
Switching between the positive side and reverse side bridges in each phase variable frequency power supply is exactly the same as the operation of the embodiment shown in FIG. In the case of a cycloconverter, the thyristor bridge is always switched between the positive side and the negative side of the AC current waveform, so it is essential to shorten the dead time in order to increase the frequency and also from the viewpoint of reducing the high frequency of the AC current. It is a condition.

 According to this embodiment, there are the following advantages.

(1) In the stationary Leonard, the dead time of the conventional method is 5 to 10 mS, while the dead time of the conventional method is 1 mS.
It becomes the following.

(2) In the cycloconverter, the non-circulating current can generate the output frequency _m up to about 1/3 of the power supply frequency _s . Where _s = 60Hz, _m = 60 × 1/3 = 20Hz _o
If the period T _m = 1/20 = 50 mS, the dead time of the conventional technology is
3 + 6 + 3 = 12mS, which is 24 [%], while
In this embodiment, 4/50 = 8 [%], that is, 24/8 = 300.
[%] It can be improved.

(3) When the TD is packed by the conventional method, the timing of blocking the gate of the thyristor in operation is delayed, so the intermittent period may be long, but this is eliminated according to the present embodiment.

Further, according to the present embodiment, in the static leonard or cyclone converter of the non-circulation current type, the switching time can be shortened by reducing the dead time at the time of switching the current direction. Further, according to the present embodiment, in the cycloconverter, it is possible to raise the output frequency and reduce the harmonics of the output variable frequency by shortening the switching time.

〔The invention's effect〕

As described above, according to the present invention, there is an effect that the switching time of the current direction of the positive side bridge circuit and the negative side bridge circuit of the thyristor converter is significantly shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a time chart shown for explaining the operation of the embodiment of the present invention.
FIG. 3 is a circuit diagram showing a concrete example of the voltage recovery detection circuit between thyristors AK, FIG. 4 is a block diagram showing a 12-phase rectification reversible speed control system to which the same embodiment is applied, and FIG. It is a block diagram showing a cycloconverter type speed control system to which an example is applied. 1 ... Three-phase AC power supply, 2 ... Cyris tabular circuit,
3 ... DC motor, 4 ... Current detector (shunt), 5
...... Speed detector (rotary generator), 6 …… Speed controller, 7
...... Current controller, 8 ... Gate pulse generator, 9 ... Switching logic circuit, 20 ... Current level detector, 21 ... Thyristor AK voltage recovery detector, 30 ... Inverse-parallel connection thyristor 1 Arm, 31 ... Light emitting diode drive circuit, 32
...... Optical fiber, 33 …… Photodiode amplification circuit, 34 ・ ・ ・
… Comparison circuit, 40 …… Control circuit including current control circuit, switching logic circuit, gate pulse generation circuit.

Claims (1)

(57) [Claims] 1. A thyristor converter that supplies a forward and reverse current to a load by a reversible thyristor bridge circuit composed of a positive side bridge circuit and a negative side bridge circuit, and a current detecting means for detecting the current supplied to the load. A current control means for inputting a current command value and a load current value detected by the current detection means and outputting an ignition phase command; and a gate signal for inputting the ignition phase command and a phase corresponding to the ignition phase command To the thyristor converter, a voltage detecting means for detecting an anode-cathode voltage of each thyristor of the reversible thyristor bridge circuit, a load current detected by the current detecting means, and the voltage detecting means. Input the voltage signal detected in, and apply the gate signal to one of the positive side bridge circuit or the negative side bridge circuit. Blocking the gate signal application to the other bridge circuit during operation, and blocking the gate signal application to the one bridge circuit in operation when the load current detected by the current detection unit becomes a specified value or less, A thyristor for confirming that the thyristor of each arm of one bridge circuit has recovered its voltage blocking capability by the voltage signal and for canceling the block of gate signal application to the other bridge circuit. Converter control unit.