JPS62138059A - Dc intermediate circuit for voltage type static converter - Google Patents

Abstract

PURPOSE:To enable return from the state of the short-circuit of an arm by fractionating a DC intermediate circuit by the ripple order width of output currents from the circuit and selecting a circuit constant so that output currents from a circuit outputting ripple currents having the high order are reduced. CONSTITUTION:A reactor 3 and a DC intermediate capacitor 20 are mounted to an intermediate circuit between a thyristor rectifier 2 and a GTO thyristor converter 5. A reactor 21 is connected in series with the DC intermediate capacitor 20, and a series circuit of a DC intermediate capacitor 23 having small capacity and the reactor 21 is connected in parallel with the series circuit. Diodes 19, 22 shorten the electrification time of the DC intermediate capacitors 20, 23. The series resonance frequency of the DC intermediate capacitor 23 and a reactor 24 is selected so as to reach a value higher than that of the DC intermediate capacitor 20 and the reactor 21, and the DC intermediate capacitor 23 and the reactor 24 are used s a small-current output circuit and higher- order ripple currents from the DC intermediate capacitor 20 are compensated.

Description

[Detailed Description of the Invention] [Industrial Application Modification] The present invention supplies current to an AC output circuit constituted by self-extinguishing semiconductor elements such as GTO (gate turn-off) silices from a DC intermediate capacitor. This invention relates to a DC intermediate circuit of a voltage source static converter to be supplied.

[Conventional technology and its problems]

For example, as shown in FIG. 5, the output from an AC power supply 1 is rectified by a Cyrisk rectifier 2, and DC power is supplied to a voltage source GTO Cyrisk converter 5, where the power is converted and the AC load 6
In a circuit that supplies AC power to a load 6 or obtains regenerated power from a load 6, a DC reactor 3 and a DC intermediate capacitor used for DC power smoothing are installed in an intermediate circuit between the Cyrisk rectifier 2 and the GTO Cyrisk converter 5. 4 is known.

On the other hand, FIG. 6 shows an example of the voltage type GTO cyrisk converter 5, in which GTO cyrisks 7 to 12 connected in a bridge are connected to reflux diodes 13 to 18, respectively.
are connected in parallel in opposite directions.

By the way, in the configuration of the DC intermediate circuit as shown in FIG. In the event of an arm short-circuit, such as when the GT○ thyristor 8 is erroneously fired during the conduction period of the GTO thyristor 7 shown in the figure, a sudden and large arm short-circuit current flows from the capacitor 4 to the GT○ thyristor 7 of the GTO thyristor converter 5. and 8, resulting in damage to these elements due to overcurrent.

Furthermore, since this arm short-circuit current is sudden, even if the control system detects this arm short-circuit and issues an extinguishing command to GTO thyristors 7 and 8, the arm short-circuit current value after the turn-off time of these elements exceeds the controllable current value of these elements, so it is impossible to recover from the arm short-circuit state by such a method.

Furthermore, if the voltage of capacitor 4 in Fig. 5, that is, the DC intermediate voltage, is high voltage exceeding 1500V, G
There is no high-voltage fuse that can protect the TO Sirisk from overcurrents, and it is impossible to protect the element with a fuse when the arm of a voltage-type GTO Sirisk converter is short-circuited.

Therefore, at present, there is no known reliable method for returning to tM without destroying the element from the arm short-circuit state when the voltage is high as described above.

The purpose of the present invention is to solve the above-mentioned disadvantages of the conventional example, and when an AC output circuit constituted by a self-extinguishing semiconductor element such as a GT○ Zyristor is short-circuited in an arm, it is possible to recover from this state by a method other than using a fuse. An object of the present invention is to provide a DC intermediate circuit for a voltage-type static converter that can protect elements from overcurrent damage.

[Means for solving problems]

In order to achieve the object of the present invention, when DC power is supplied through an intermediate circuit including a DC intermediate capacitor of an AC output circuit constituted by a self-extinguishing semiconductor element, a reactor is connected in series to the intermediate capacitor. In addition, this capacitor and the series circuit of the reactor are connected in parallel with another small-capacity DC intermediate capacitor and a series circuit with an accelerator or resistor to compensate for the high-order ripple current from the DC intermediate capacitor blocked by the reactor. The gist of this is to

[Effect]

According to the present invention, when an arm short-circuit occurs in an AC output circuit constituted by a self-extinguishing semiconductor element such as a GTO thyristor, the rate of increase of this arm short-circuit current is suppressed, and the AC output circuit During the time period until the self-extinguishing semiconductor element of the current phase self-extinguishes itself in response to a command from the control system that has detected the arm short circuit, the arm short-circuit current is used as the cut-off current (controllable) of the self-extinguishing semiconductor element. By suppressing the current to a value equal to or lower than the current value, it becomes possible to recover the AC output circuit from the arm short-circuit state.

〔Example〕

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

FIG. 1 is a circuit diagram showing a first embodiment of a DC intermediate circuit of a voltage-type static converter according to the present invention, in which the output from an AC power supply 1 as shown in FIG. is applied to the voltage type GT○ thyristor converter 5, which converts the power and supplies AC power to the AC load 6, or obtains the power regenerated from the load 6.
and reactor 3 in the intermediate circuit of GTO Cyrisk converter 5.
and a DC intermediate capacitor 20, a reactor 21 is connected in series with this first DC intermediate capacitor 20.
A second small-capacity DC intermediate capacitor 23 and a second series circuit of the reactor 24 are connected in parallel with this first series circuit.
A series circuit is connected.

Furthermore, diodes 19 and 22 are connected to these reactors 21 and 24, and DC intermediate capacitors 20 and 23 are connected to the reactors 21 and 24.
are connected in parallel to reduce charging time.

By the way, the series resonance frequency of the DC intermediate capacitor 23 and the reactor 24 is set to be a higher value than that of the DC intermediate capacitor 20 and the reactor 21 in the first series circuit, and moreover, the voltage type GTO Sirisk converter 5 has an arm short circuit. The control system detects this and issues an arc extinguishing command to the GTO sirisk of the shorted phase, and calculates the sum of the discharge current from the DC intermediate capacitors 20 and 23 and the current of the DC reactor 3 at the time when these elements self-extinguish the arc. The constants of the DC intermediate capacitors 20 and 23 and the reactors 21 and 24 are selected so that the current value is equal to or less than the controllable current value of the GTO thyristor.

That is, the DC intermediate capacitor 23 is selected to have a smaller value than the DC intermediate capacitor 20, and the reactors 21 and 2
4 is selected to a value that satisfies the conditions of the series resonance frequency and discharge current value.

In this way, the small capacitance DC intermediate capacitor 23 and reactor 24 of the second series circuit act as a small current output circuit to prevent high-order ripples from the DC intermediate capacitor 20 blocked by the first series circuit's axle 21. This will compensate for the current.

As a result, when the GTO thyristors 7 to 12 of the GTO thyristor converter 5 have an arm short circuit, the rate of increase in current is suppressed, and the control system detects the arm short circuit and issues an arc extinguishing command to the GTO thyrisk of the shorted phase. When given, the arm short-circuit current value after the turn-off time of the element can be made equal to or less than the controllable current value of the GTO Cyrisk.

FIG. 2 shows a second embodiment, and shows the first embodiment of the first embodiment.
The difference from the one shown is that the resistor 25 is replaced by the reactor 24.
This is the point connected in series with . As a result, reactor 24
, the resonance phenomenon inside the DC intermediate circuit caused by the DC intermediate capacitors 20 and 23 can be suppressed.

Furthermore, as a third embodiment, a resistor 26 may be connected in series with the DC intermediate capacitor 23 instead of the reactor in order to prevent resonance within the DC intermediate circuit, as shown in FIG.

Further, as another embodiment, as shown in FIG.
In addition to the DC circuit, there is a capacitor 28 and an accelerator 29.
, a third series circuit of resistors 30 was connected in parallel. In this case, the DC intermediate capacitor 23 is replaced by 20, and 28 is replaced by 2
3, the order width of the output current ripple of the DC intermediate circuit is divided into smaller capacitances, and the smaller the capacitor capacity, that is, the circuit that outputs a higher order ripple current, the smaller the output current (discharge current). The reactor 29 or resistor 30 connected in series with the DC intermediate capacitor 28 was selected to reduce its size.

As a result, the arm short-circuit current value at which the GTO syrisk of the short-circuited phase is cut off after the voltage type GTO syrisk converter 5 short-circuits the arm can be made smaller than in the first to third embodiments.

〔Effect of the invention〕

As described above, in the DC intermediate circuit of the voltage source static converter of the present invention, the DC intermediate circuit is subdivided according to the ripple order width of its output current. Since the circuit constants are selected to reduce the size, when an arm short-circuit occurs in an AC output circuit composed of a self-extinguishing semiconductor device such as GTO Cyrisk, the rate of increase in arm short-circuit current can be suppressed, making it possible to control When the system detects an arm short circuit and issues an arc extinguishing command to the element of the shorted phase, the arm short circuit current value after the element turn-off time can be kept below the controllable current value of the element. It becomes possible to restore the AC output circuit from the arm short-circuit state, and it is possible to protect the device from overcurrent destruction by a method other than using a fuse.

[Brief explanation of drawings]

1 to 4 are circuit diagrams showing the first to fourth embodiments of the DC intermediate circuit of the voltage-type static converter of the present invention, FIG. 5 is a circuit diagram showing a conventional example, and FIG. 6 is a voltage-type static converter. FIG. 2 is a circuit diagram showing an example of a GTO thyristor converter. 1... AC power supply 2... Thyristor rectifier 3.
...DC reactor 4...DC intermediate capacitor 5...Voltage type GTO thyristor converter 6...AC load 7-12...GTO thyristor 13-18.
...Diode 19...Diode 20...DC intermediate capacitor 21...Reactor 22...Diode 23
．． 28...DC intermediate capacitor 24.29...Reactor

Claims (1)

[Claims] In a device that supplies DC power to an AC output circuit composed of self-extinguishing semiconductor elements via an intermediate circuit including a DC intermediate capacitor, a reactor is connected in series to the intermediate capacitor, and a series circuit of the capacitor and the reactor is used. Voltage-type static conversion characterized in that a series circuit with a reactor or resistor is connected in parallel with another small-capacity DC intermediate capacitor to compensate for the high-order ripple current from the DC intermediate capacitor blocked by the reactor. DC intermediate circuit of the device.