JP2614278B2 - How to protect superconducting energy storage systems. - Google Patents

Description

The present invention relates to a superconducting energy storage system, and more particularly to a method for protecting a system in which a plurality of converters are connected when a failure occurs.

(Prior Art) Since the resistance of a superconducting coil is almost zero, the time constant of the coil is very large. For this reason, research has been conducted on a superconducting energy storage system (hereinafter abbreviated as SMES) for storing energy by circulating a direct current in a superconducting coil to prevent pulse loads such as nuclear fusion and peak loads of electric power. SMES has a long-term power adjustment,
If the converter connected to the power system is constituted by a self-extinguishing element (for example, gate turn-off thyristor, hereinafter abbreviated as GTO), it can have functions such as system stabilization and system reactive power compensation. However, in order to effectively perform such a function, the current flowing through the superconducting coil requires a capacity of several KA to several hundred KA. Therefore, the conversion device is also configured by connecting several to several hundred GTOs in parallel.

FIG. 4 shows a conventional SMES. In FIG. 4, 1 is an AC bus, 2 is a transformer, 3 is a self-excited converter constituted by a GTO, 4 is a superconducting coil, and 5 is an overvoltage ignition circuit for igniting a short-circuit switch 6 when an overvoltage occurs. , 7 are resistors for consuming coil energy at the time of failure.

In the SMES as shown in FIG.
Is a current-type converter due to the nature of SMES, which stores energy by the current flowing through the coil. In a current type converter, an overvoltage occurs when the circuit is opened. During normal operation, control is performed so as not to be in the open state. However, when the GTO is erroneously extinguished or erroneously fired, or when the wire is disconnected, the energy of the current flowing through the superconducting coil 4 sharply increases. An excessive rising voltage occurs. At this time, in the circuit shown in FIG. 4, the overvoltage ignition circuit 5 operates, the short-circuit switch 6 is closed, and the coil energy is consumed by the resistor 7 for protection.

(Problems to be Solved by the Invention) However, in the SMES on a practical scale, coil energy ranges from several megawatt hours to several gigawatts, and it is uneconomical to consume all energy by resistance when a failure occurs.

An object of the present invention is to provide a method for protecting a superconducting energy storage system that can effectively use the energy of a coil even when a failure occurs.

[Constitution of the Invention] (Means for Solving the Problems) The present invention is directed to a superconducting energy storage system including a plurality of converters each including a self-extinguishing element and a superconducting coil, which are generated at both ends of the converter. A switch for short-circuiting both ends of the converter by being ignited by an overvoltage; and a means for determining a failed converter based on an operation signal of the switch, a stop signal is given to the failed converter, and a healthy converter is provided. A bypass pair signal is given, and then a forward conversion operation is performed.After detecting that the current flowing through the short-circuit switch of the failed converter is zero, the system is restarted only with a healthy converter, so that the coil is turned on. A superconducting energy storage system that can effectively use stored energy can be provided.

(Operation) According to the present invention, even if one of the plurality of converters fails and an overvoltage occurs, the short-circuit switch can be fired and protected by the overvoltage generated at both ends of the converter. Further, by providing a means for determining a failed converter, a stop signal is given to the failed converter, a bypass pair signal is given to the healthy converter, and thereafter, the healthy converter is operated by performing the forward conversion operation. In addition, the current of the short-circuit switch of the failed converter is made sufficiently small, the failed converter can be disconnected, and the operation can be restarted only with a healthy converter, thereby providing protection that can effectively use the energy of the coil.

(Embodiment) An embodiment of the present invention is shown in FIG. In FIG.
The same elements as those in FIG. 4 already described are denoted by the same reference numerals, and description thereof will be omitted. 8A and 8B are reactors for balancing the current between multiple converters, 9A and 9B are current detectors that detect the current of the short-circuit switch, and 10 is a converter that has failed from the outputs of 9A and 9B. A failure group determination circuit, 11 is a delay circuit for delaying the failure occurrence signal 51 output from the failure group determination circuit 10 to the healthy group, 12A and 12B are AND circuits, 13 is an inversion circuit, 1
4A and 14B control on / off of the self-excited converters 3A and 3B by a bypass pair command 52, a forward conversion operation command 53, a restart command 54, a gate block command 55, etc., and a command from a power supply control circuit (not shown). It is a firing control circuit. Reference numeral 56 denotes a failure group separation completion signal indicating that the current of the short-circuit switch of the failure group is zero.

The operation of the present invention will be described with reference to FIG. As described above, in a current-type converter, an overvoltage occurs when the circuit is opened. For example, suppose that the element of the converter 3A is erroneously extinguished in FIG. Then, an overvoltage occurs at both ends of the converter 3A, the overvoltage firing circuit 5A operates, and the short-circuit switch 6A turns on. Then, the current detector 9A detects the current flowing through the semiconductor switch 6A. The failure group detection circuit 10 determines a failure and a failure group based on a signal from the current detector, outputs a gate block command 55 to the failure group and stops the operation, and outputs a failure occurrence signal to the healthy group. Then, after the occurrence of the failure, the delay circuit 11
The bypass pair command 52 is output until the time set in. At that time, the load current flows via the healthy converter 3B and the semiconductor switch 6A. When the time determined by the delay circuit 11 has elapsed, a forward conversion operation command 53 is output to the healthy group,
Healthy group converter 3B outputs an appropriate DC voltage. Then, a reverse voltage is applied to the short-circuit switch, the current decreases, and the switch turns off when the current becomes zero. The fault converter is now disconnected from the system. When the failure group determination circuit detects that the current of the short-circuit switch of the failure group has become zero, a restart command 54 is output, and the operation is resumed only with the healthy group.

FIG. 2 is a flowchart showing the protection operation in the event of a failure. The failure group detection circuit 10 determines a failure and a failure group based on a signal from the current detector, outputs a gate block signal to the failure group, and outputs a bypass pair signal to the healthy group. After a certain period of time, the healthy group is operated in the forward conversion mode. The normal group is restarted by detecting that the current of the short-circuit switch of the fault group is zero.

The case where the self-excited converter 3A has failed has been described above. The same applies to the case where the converter 3B has failed. The same applies to a case where two or more converters are used.

As described above, according to the present embodiment, it is possible to provide a protection device that can effectively use the energy stored in the coil even when a failure occurs.

Further, in the present invention, as a self-extinguishing element,
It goes without saying that the same effect can be obtained by using an element other than the GTO, for example, a transistor or an electrostatic induction thyristor.

Another embodiment of the present invention is shown in FIG. In FIG. 3, the same elements as those in FIGS. 1 and 2 described above are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 3, 15A and 15B are circuits for detecting the voltage across the short-circuit switch. FIG. 3 shows the operation of the short-circuit switches 6A, 6B detected by the current detectors 9A, 9B in FIG. 1 detected by the voltage detectors 15A, 15B. 6A, 6B
Needless to say, the same effect can be obtained even if the voltage is detected in the above operation. The same applies to the case where the operation of the short-circuit switches 6A and 6B is detected by the operation current of the overvoltage firing circuits 5A and 5B.

[Effect of the Invention] As in the present invention, in a superconducting energy storage system including a plurality of converters each including a self-extinguishing element and a superconducting coil, the converter is ignited by an overvoltage generated at both ends of the converter. A switch for short-circuiting both ends, and means for determining a failed converter based on an operation signal of the switch, and providing a stop signal to the failed converter;
Apply a bypass pair signal to a healthy converter, then perform forward conversion operation, and after detecting that the current flowing through the short-circuit switch of the failed converter is zero, restart the system with only the healthy converter. Then, it is possible to provide a method for protecting the superconducting energy storage system that can effectively use the energy stored in the coil.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a flowchart for explaining a protection operation of the present invention, FIG. 3 is a block diagram showing another embodiment of the present invention, and FIG. 1 is a diagram showing a superconducting energy storage system of FIG. 1. AC bus, 2A, 2B ... Rectifier transformer, 3A, 3B ...
Self-excited converter, 4 ... superconducting coil, 5A, 5B ... overvoltage ignition circuit, 6A, 6B ... short circuit switch, 7 ... protection resistor, 8A, 8B ... balancer reactor, 9A, 9B ... current Detector, 10: Failure group determination circuit, 11: Delay circuit, 12A, 12B
... AND circuit, 13 ... inversion circuit, 14A, 14B ... ignition control circuit, 15A, 15B ... overvoltage detection circuit, 51 ... fault occurrence signal, 52 ... bypass pair command, 53 ... forward conversion Run command, 54 ... Restart command, 55 ... Gate block signal, 56
...... A failure group separation completion signal.

Claims (1)

(57) [Claims] In a superconducting energy storage system for energizing a superconducting coil by connecting a plurality of converters each composed of a self-extinguishing element in parallel, each converter is activated by an overvoltage generated across the converter. It has a short-circuit switch that ignites and short-circuits the converter, determines the converter that has received an operation signal of the switch and has become overvoltage, gives a stop signal to the converter that has become overvoltage, and provides a sound converter. Gives the bypass pair signal, then shifts to the forward conversion operation, and restarts only the healthy converter after detecting that the current flowing to the overvoltage converter short-circuit switch is zero. A method for protecting a superconducting energy storage system, characterized in that: