JPS6162361A - thyristor conversion device - Google Patents

Abstract

PURPOSE:To reduce harmonic waves due to unbalance of upper and lower bridges by constructing to control two circulating current loops in balance by one circulating current control system. CONSTITUTION:An error current controller CCC is provided at the rear stage of a circulating current regulator CCR. The error of the circulating current is obtained from the current ITH of a connecting wire a-b when the directions of thyristor converters TH1 are connected as shown. If an output current is set to zero while controlling two circulating current loops by one circulating current control system, the gate block of other loop is performed while flowing the circulating current only to one side loop. Thus, the responding speed is accelerated, and the harmonic waves due to the unbalance of upper and lower bridges can be reduced.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a circulating current type thyristor conversion device, and in particular,
The present invention relates to a WI ring current source thyristor conversion device suitable for use as a power conversion device that uses both output current control and reactive power control.

[Background of the invention]

A circulating current type thyristor converter generally has a configuration as shown in FIG. In other words, a thyristor bridge has a positive polarity thyristor converter TH and a negative polarity thyristor converter THN connected in parallel to the load LD, and there is a circulating current between the two converters. Output current ■ to the load LD while flowing. supply. In order to suppress the circulating current, the circulating current circuit may be omitted by utilizing the leakage inductance of the AC input power transformer TR, in which a direct current reactor DCL is usually inserted. The output current is controlled by the command Iop of the current command device OCP and the output current control. This is done by applying a gate pulse phase shift control signal to the gate control circuits GC, , GC, by the current regulator ACR so that the deviation of .

Here, since the thyristor converters TH and THII are connected with opposite polarities, the output of the current regulator ACR is of positive polarity to the input side adder AD of the positive side gate control circuit GC, and Input side addition DA of reverse side gate control circuit GC,
Give negative polarity to DN. FIG. 3 shows the output voltage characteristics of the thyristor converter with respect to the input signals of each gate control circuit.

In this way, when the output of the current regulator is applied to the gate control circuit, the voltages of both converters are balanced. In this state, the output of the I# ring current regulator OCR is that the circulating current I0 is
It is added to each adder in order to add a difference between the output voltages of both converters so that the command Icp of CP is obtained. That is, m5w4
If is smaller than the command value, the output voltage of TH increases;

The output voltage of TH, decreases and this differential voltage increases the circulating current.

As shown in Figure 2, this type of device is equipped with a phase advancing capacitor C on the AC power supply side, and is used to control the overall power factor by adjusting the lagging reactive power using the w1 ring current, and to control the output current. It is used for purposes such as smooth polarity cutting and precise small current control. By the way, in the case of one generation as shown in Figure 2.

It was impossible to completely reduce the output current to zero (electrically disconnect the load circuit) while controlling reactive power by flowing a circulating current. In other words, in order to completely reduce the output current to zero, it is necessary to suppress the gate of the thyristor conversion, and in this way, reactive power control cannot be performed.An example where such operation is necessary is the 41 ring current type. There is a switch on the output side of the thyristor converter, and this switch is turned off in a no-current state. When used in a superconducting magnetic levitation railway linear motor power supply device as shown in FIG. 1, exactly such an operation is performed. Therefore, if residual DC current flows, even if it is small, the switch will generate a large amount of arcing, and its life will be extremely shortened.

In order to solve this problem, we decided to connect thyristor bridges in multiple stages to form two or more circulating current circuits to completely control the output current while adjusting the reactive power using the UA ring current. Japanese Patent Application No. 147941/1987 discloses a system in which a circulating current is passed through each thyristor bridge when energized, and when the output current is stopped, the 4111 current of at least one thyristor bridge is set to zero and the 4111 current is transferred to the remaining thyristor bridges. It has been proposed as a number.

Figure 4 shows the control system implantation that has been considered in the past.
The difference from the diagram is that in the main circuit, thyristor bridges THI and TH2 are connected in two stages to form two circulating current circuits, and in the control circuit, gate control circuits GC1 and TH2 are connected in two stages for each thyristor bridge. GC1 and Wi ring current regulator OCR.

0CR2 is provided, and circulating current switching I! I control circuit CC
C and gate suppressor circuit G of thyristor bridge TH2
The point is that S is provided.

The operation shown in FIG. 4 will be explained with reference to the signal chart shown in FIG. Thyristor bridge TH when output current is applied
Both I and TH2 are working.

The Wi ring current of each bridge flows by dividing the circulating current command value Icp by the ratio of the divider DIV. That is, in the circulating current switching control circuit CCC, the output of the time constant circuit TC is a cloud, and the IJl ring current command ICP outputs the circulating current value according to the division ratio via the divider DIV and the proportional amplifier LMT to the thyristor bridge TH2. circulating current regulator,
The remaining WI circulating current value is given to the circulating current value of the thyristor bridge THI. When an output stop command is issued in such a state, the output current command device sets the current command I+1pti- atmosphere, and the current regulator ACR changes the output current 1. It operates to reduce to zero. On the other hand, the output of the time constant circuit of the circulating current switching control circuit gradually increases, and the output of the time constant circuit of the circulating current switching control circuit gradually increases.
The ring current command goes to zero, and the thyristor bridge T
The circulating current circuit of HIO1i changes towards Icy. And w1 ring current I of thyristor bridge TI+2
When C2 becomes zero and the transfer of the circulating current to the thyristor bridge THI side ends, the gate suppress circuit GS is activated, the output pulse of the gate control circuit GC2 is suppressed, and the thyristor bridge TH2 is completely stopped. Then, it becomes possible to open the output side switch SW of the thyristor conversion device in a no-current state while continuing reactive power control. Note that when the Wi ring current becomes negative, the thyristor is in a non-conducting state, but in order to more reliably bring the thyristor bridge into a non-conducting state, the gate pulse is suppressed in the embodiment shown in Figure i53. Also.

In FIG. 4, the dotted line signal given from the gate suppressor circuit GS to the gate suppressor circuit GC2 is a gate shift signal, which is effective when shifting quickly.

By the way, in the case of the control method shown in FIG. 4, two circulating current control systems are required. Furthermore, since the circulating current systems of THl and TR2 are controlled separately, the number of pulses in each control system during normal operation is half the number of pulses in the main circuit, and the response is delayed accordingly. Furthermore, due to errors in the two control systems, an error current flows through the intermediate bar during normal times, which causes extra harmonics to be generated.

[Purpose of the invention]

An object of the present invention is to control two circulating current loops with a single circulating current control system and to make the output current zero, the circulating current is passed through only one loop while the other loop is controlled. The purpose of the present invention is to provide a control device that enables gate blocking.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention, which differs from FIG. 4 in that one WI ring current regulator OCR is provided with an error current control circuit CCC at its subsequent stage. Here, the error in the circulating current can be determined from the current IτB of the connection line a-b by connecting the directions of the thyristor converters as shown in the figure.

The operation when the output stop is commanded is the same as that shown in FIG. 5, so a description thereof will be omitted.

〔Effect of the invention〕

According to the present invention, two circulating current loops can be controlled in a balanced manner using one circulating current control system.

(1) Compared to the conventional method, it can be controlled with two stages of pulse numbers, so the response speed is faster.

(2) Since the current flowing through the connection line a-b can be normally reduced to zero, harmonics due to imbalance between the upper and lower bridges can be reduced.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an embodiment of the present invention, Figure 2 is a circuit diagram explaining a conventional example of a circulating current type thyristor converter, Figure 3 is an input/output characteristic diagram of the thyristor converter, and Figure 4 is A circuit diagram of a conventionally considered device, FIG. 5 is an operation chart of FIG. 4. THI, , THI N... Thyristor converters forming the first thyristor bridge, TR2, TR2N...
Thyristor converter constituting the second thyristor bridge, IC1p IC3"' Circulating current of the first and second circulating 8fI! current circuits, CCC... Circulating IM current switching control circuit. GS... Second thyristor bridge gate suppress circuit, ACR...output current regulator, OCR...circulating current regulator, GC...gate control circuit, sw...output side switch, TR...f of thyristor converter!! Source Transformer Transformer Patent Attorney Akio Takahashi 4 Swords

Claims (1)

[Claims] 1. In a cycloconverter in which an AC output and a circulating current can be controlled by connecting thyristor conversion devices in antiparallel, two circulating current loops can flow through the cycloconverter. so that two stages are connected in series, the one circulating current loop is gate-blocked, the circulating current can continue to flow through the other circulating current loop, and the circulating current goes around the series-connected cycloconverters. Circulation of the cycloconverters connected in two stages in series by one circulating current control device that controls the current and a correction circuit that controls to zero the error current flowing in the connection line of the cycloconverters connected with DC. A thyristor conversion device characterized by controlling current.