JPS5932996B2 - DC power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC power supply device in which a large capacity capacitor is connected to a DC terminal, which has a function of regenerating capacitor energy to an input power source when a load is short-circuited or stopped.

Figure 1 shows a typical conventional DC power supply.
The input AC power supply 1 is converted into a variable DC power supply by a thyristor rectifier 2 composed of thyristors 51 to 56, smoothed by a reactor 3 and a capacitor 4, and then smoothed by a terminal 5.
6 to obtain a smoothed DC output.

FIG. 2 shows, for example, the inverter 11 and its load 12 energized by the DC power supply shown in FIG. 1, including main thyristors 57 to 510 and flywheel diode D1.
~D4 is shown, and the normally required commutation circuit is not shown. When such an inverter 11 is connected to a DC power supply (terminals 5 and 5', and 6 and c are connected respectively),
The lower the load power factor of the inverter 11, the more ripple current flows in the output current of the DC power supply, so the capacitor capacity is increased so that the ripple voltage between terminals 5 and 6 is several percent or less. To give specific numbers, DC2OOV
When a 100 KVA inverter is connected to a DC power supply device, the capacitance of the capacitor 4 is approximately 100,000 μF. If commutation failure occurs for some reason in the inverter 11, which is the load in a DC power supply device equipped with such a large capacity capacitor, the upper and lower thyristors S7 or S8 in the inverter and the SlO As a result, a large discharge current will flow from the capacitor 4 through the shorted thyristor. In order to prevent thyristor deterioration due to this, for example, when commutation fails, all main thyristors S7 to S, O are fired to disperse the discharge current and reduce the current flowing to one thyristor, etc. There are methods such as a dispersion method that reduces the current, and a method that limits the current by inserting a fuse. In the former case, it is necessary to insert a reactor into the discharge loop of the capacitor to suppress excessive discharge current, and also to provide a surge absorber to absorb the spike voltage generated by the reactor during commutation, etc. Originally, capacitors were inserted solely to reduce the impedance on the DC power supply side as seen from the load side, so inserting a reactor would defeat that purpose.
Inevitably, the inductance of the reactor cannot be increased, and a discharge current of about 30 KA will flow in the 100 KVA class. In the latter case, it is difficult to obtain a DC fuse that matches the characteristics of the thyristor, and it is inconvenient that the fuse must be repeatedly blown until the cause of the inverter failure is eliminated. Furthermore, recently 10-100M
The production of a W-class self-excited inverter is currently under consideration, but when the DC voltage is 1.5 to 20 KV, there is no suitable fuse, and fuses are completely unusable. However, there remain problems such as unbalanced voltages applied to the elements after overcurrent.

As described above, the conventional methods have focused on how to protect thyristors and the like from overcurrents caused by short circuits. SUMMARY OF THE INVENTION An object of the present invention is to provide a DC power supply device that does not cause overcurrent during a short circuit without impairing its steady-state characteristics.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 3 shows an embodiment of the present invention, in which an auxiliary power supply device 20 surrounded by a dashed line is added to the DC power supply device of FIG. 1. In FIG. 3, the capacitor 4 is a diode. 21 to terminals 5 and 6.

The diode 21 includes an isolation transformer 22 and a controlled rectifier 23.
A constant current 10 is applied from a DC power supply consisting of a . During normal operation of the above-mentioned DC power supply device, a ripple current Ir, which is a combination of the ripple current generated by the thyristor rectifier 2 and the ripple current caused by connecting a load such as the inverter 11, flows through the capacitor 4.

Here, if IO is set so that IO>11r1, the current flowing through the diode 21 will not become negative, and the voltage between the electrodes of the diode 21 will be maintained at about 1V at most, with the anode side being positive. Therefore, there is no substantial difference in characteristics from the power supply shown in FIG. 1 without the diode 21. Next, if a short circuit occurs on the load side, most of the voltage Ec charged in the capacitor 4 is applied to the diode 21 with the cathode side being positive. As a result, diode 21 blocks and current 10 in reactor 24 continues to flow through capacitor 4 and the short circuit. Therefore, only the sum of the current of the reactor 3 and the reactor 24 flows into the short-circuited part, and the current is limited to a value slightly exceeding the normal maximum load current (peak value). Further, the voltage detector 25 detects the voltage applied between the poles of the diode 21 at the time of the accident, and immediately shifts the firing control angle (a) of the thyristor rectifiers 2 and 23 to the delay side and shifts to the reverse conversion operation. The energy of 3 is passed through the thyristor rectifier 2, and the energy of the reactor 24 and capacitor 4 is passed through the controlled rectifier 23.
Since each is regenerated to the power supply 1, the current at the time of a short circuit attenuates quickly. As described above, according to the present invention, compared to the conventional method in which most of the energy of the capacitor 4 was consumed in a short circuit and passed as an excessive discharge current (for example, 50 times the load current), the energy of the capacitor 4 is large. The part is returned to the power supply, and the discharge current is only slightly higher than the load current,
It becomes very easy to protect a device configured by providing a transistor or thyristor with low overcurrent resistance on the load side.

FIG. 4 is a circuit diagram showing another embodiment of the present invention, in which the diode 21 is inserted into a path through which the load current passes.

In this case, the current 10 of the rear turtle 24 is set to a value that slightly exceeds the maximum load current (peak value) including ripple current. The reason why the diode 21 is larger than that shown in FIG. 3 is because it limits the short-circuit current to IO, including the short-circuit current that flows from the power supply 1 through the diode rectifier 2' when the load is short-circuited, in addition to the discharge current of the capacitor 4. can. When a diode rectifier 2' is used as shown in FIG. 4, the energy of the reactor 3 cannot be regenerated into the power supply, so the disconnector 7 must be opened. To explain the current control method of the reactor 24 in FIGS. 3 and 4, the input side current of the control rectifier 23 or the reactor current is detected and constant current control of the thyristor rectifier 23 is performed, but the accuracy of the current value is Since this will not be a problem, the controlled rectifier 23 is configured to provide a DC voltage that is the sum of the on-voltage of the diode 21 and the resistance drop of the reactor 24.
The control angle may also be determined.

Although the loss increases, by inserting a resistor in series with the reactor 24, the influence of voltage fluctuations of the input power source 1 can be reduced. However, once a short-circuit accident occurs and the controlled rectifier 23 is reverse-converted in order to quickly return the energy of the capacitor 4 to the power supply 1, the higher the input voltage of the controlled rectifier 23, the faster the energy regeneration will be. Both the transformer 22 and the control rectifier 23 are large in size and require a lot of constant reactive power. Therefore, a rectifier that uses both a low voltage rectifier and a regenerative rectifier may be used. On the other hand, if the input voltage of the controlled rectifier 23 is low, the regeneration of the energy of the capacitor 4 will be prolonged, and in some cases, the reverse conversion operation of the controlled rectifier 23 may cause commutation failure. However, the inductance of the reactor 24 is 100 to 100 times the inductance included in the inverter shown in FIG.
0 times the magnitude, the current value generated in the reactor 24 due to a commutation failure in the controlled rectifier 23 is low, and the commutation failure quickly recovers, so there is no need to worry. This can be considered a design issue. FIG. 5 is a circuit diagram showing still another embodiment of the present invention. The difference from FIG. 3 is that the energy regeneration of the reactor 24 and the capacitor 4 is performed together by the controlled rectifier 2.

In the figure, 31 is a low voltage DC power supply using a controlled rectifier or a non-controlled rectifier, and 32 is a thyristor. The DC power supply 31 is a power supply of several volts to several tens of volts that compensates for the voltage drop of the diode 21, thyristor 32, and reactor 24, and is not particularly expected to have regenerative ability. Normally, a power source called IO is flowing from this DC power source 31 in a closed circuit of the reactor 24, the diode 21, the thyristor 32, and the DC power source 31. Also,
The capacitor 34 is charged with the peak value of the voltage generated by the thyristor rectifier 2 via the diode 33 . If a load short circuit occurs in this state, the load short circuit is detected by the reverse voltage detection of the diode 21 or other means, and the thyristor 35 is fired, and the thyristor rectifier 2 is shifted to reverse conversion operation. At this point, the voltage of the capacitor 34 is applied to the thyristor 32 as a reverse voltage, and the thyristor 32 is turned off.

As a result, the energy possessed by the reactor 32 and the capacitor 4 is transferred from the power supply 1 to the thyristor rectifier 2 to the diode 3.
3 → Thyristor 35 → DC power supply 31 → Reactor 24 →
Capacitor 4 → Short circuit → Thyristor rectifier 2 → Power supply 1
The energy of the capacitor 4 and the reactor 24 is returned to the power source in the closed circuit of. Of course, the energy in the reactor 3 is also regenerated. In this way, the DC source 31 may be simple.
In FIG. 6, the DC power source 31 and thyristor 32 in FIG. 5 are replaced with a DC power source 315 using a thyristor.

However, this DC power supply 3f is of low voltage and is not expected to have regenerative ability. As in Fig. 5, the thyristor rectifier 3 is normally used.
1', IO flows into the reactor 24, and in case of an accident, the thyristor 35 is ignited and the thyristor rectifier 3 is activated.
1' flow is blocked. The subsequent operation is similar to that shown in FIG. The above describes the overcurrent suppression function when the load is short-circuited. However, if you want to quickly discharge the charge in the capacitor 4, such as when the load is stopped, you can actively short-circuit the load side and transfer the capacitor energy to the input power supply. It is possible to take a method of regenerating the

For example, in order to short-circuit between terminals 5 and 6 when stopping, thyristors S7 and S of the inverter 11 should be connected to the stop command.
so that they fire at the same time. Further additional functions can be expected by using the present invention.

In other words, if the input of the DC power supply is a storage battery (of course not including the thyristor rectifier 2) or a DC power supply using the diode rectifier 2, if you suddenly connect it to the input of the DC power supply, the capacitor will be rapidly charged and the life of the capacitor will be shortened. Undervoltage or overcharging will cause unnecessary inrush current to flow through the diode rectifier, input line, or disconnector. To avoid this, conventionally, the capacitor is precharged using a resistor or the like. Controlled rectifier 23 in the circuit of the invention
When switched in the opposite direction before starting, the flywheel diodes D, , D3 provided in the inverter on the load side
Alternatively, the capacitor 4 may be precharged via D2, D4 or the diode rectifier 2/, and then the controlled rectifier 23 may be returned to its original direction.

Alternatively, as shown in Figure 7, if a new winding is added to the isolation transformer and connected as shown through the thyristor 40, the current 1 precharges the capacitor through the diode or diode rectifier 7 on the load side. be able to. Modified Examples Although the rectifier 23 in FIGS. 3, 4, and 7 has been described using a center tap type rectifier, it is clear that any other type of rectifier may be used.

As described above, the present invention has the following features: 1) It is possible to prevent overcurrent during abnormal conditions without impairing steady-state characteristics.

2) The capacitor can be quickly discharged when stopped.

3) When manufacturing a high-voltage, large-capacity converter, protection of elements becomes very simple, and one of the practical problems of large-capacity converters is solved.

4) Capacitor pre-charging function can also be added.

This method has excellent effects such as, and has a great effect on contributing to industry.

[Brief explanation of the drawing]

Figure 1 is the main circuit diagram of a conventional DC power supply, and Figure 2 is the main circuit diagram of a conventional DC power supply.
FIG. 3 is a circuit diagram showing one embodiment of the present invention, and FIGS. 4 to 7 are circuit diagrams of other different embodiments of the present invention. 1... AC power supply, 2... Thyristor rectifier, 7... Diode rectifier, 3, 24...
...Reactor, 4,34...Capacitor, 5,6...Output terminal, 5,6t...Input terminal, 7...Shrinking equipment, 11...Inverter, 12...Inverter load, 20.
...Auxiliary power supply device, 21, 33', D1 to D4.
...Diode, 22, 22t...Isolation transformer, 23, 31...Control rectifier, 25...
...Voltage detector, 35, 40, S1~SlO...
...thyristor.

Claims (1)

[Claims] 1. In a DC power supply device having a smoothing circuit consisting of a DC reactor and a parallel capacitor, a diode is provided in the discharge loop of the capacitor with a polarity that blocks the discharge current, and an auxiliary power supply consisting of a controlled rectifier and a reactor is provided. A predetermined forward current is supplied to the diode through the device, and in the event of a short circuit accident on the output side of the DC power supply, the energy of the capacitor is regenerated to the AC power supply through the controlled rectifier. DC power supply. 2. In a DC power supply device having a smoothing circuit consisting of a DC reactor and a parallel capacitor, a diode is provided in the discharge loop of the capacitor with a polarity that blocks the discharge current, and the diode is When stopping the operation of the DC power supply while supplying a predetermined forward current to the DC power supply, a discharge path for the capacitor is formed on the output side of the DC power supply, and the energy of the capacitor is transferred to the AC power supply via the controlled rectifier. A DC power supply device characterized by regeneration. 3. In a DC power supply device having a smoothing circuit consisting of a DC reactor and a parallel capacitor, a diode is provided in the discharge loop of the capacitor with a polarity that blocks the discharge current, and one of the auxiliary power supply devices consisting of two sets of controlled rectifiers and a reactor is provided. A predetermined forward current is supplied to the diode through the controlled rectifier, and in the event of a short circuit accident on the output side of the DC power supply, the energy of the capacitor is regenerated to the AC power source through the other controlled rectifier. A DC power supply device characterized by: 4. In a DC power supply device having a smoothing circuit consisting of a thyristor rectifier, a DC reactor, and a parallel capacitor that converts AC voltage into a desired DC voltage, a diode is provided in the discharge loop of the capacitor with a polarity that blocks the discharge current, and control is performed. A predetermined forward current is supplied to the diode through an auxiliary power supply device consisting of a rectifier or an uncontrolled rectifier and a reactor, and in the event of a short-circuit accident on the output side of the DC power supply device, the forward current is blocked and the energy of the capacitor is A DC power supply device comprising a thyristor for regenerating the AC power through the thyristor rectifier.