RU2451379C1 - Method to limit short-circuit currents and to increase controllability of power flows in power systems and device for its realisation - multimodule dc insert (mdci) - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: reversible controlled electric connections are generated in the required areas of interruption for flow of short-circuit currents by placement of modules of a multimodule DC insert, besides, the required number of controlled links C and the number of modules m required for their formation are related by the following ratio:

A multimodule DC insert comprises m converting modules, every of which represents a reversing controlled converting device of an alternating current or voltage into a direct one, each connected to their unit at the AC side, and at the DC side connected in parallel to the common DC buses.

EFFECT: reliability improvement.

2 cl, 3 dwg

Description

Technical field

The invention relates to the field of electrical engineering and can be used to effectively limit short-circuit currents in complex ring power networks of power systems containing several power generation plants - power plants, and to control the active power flow in ring circuits of both one class and different voltage classes.

State of the art

The most common ways to limit short-circuit currents are: installing current-limiting devices of various types (reactors, etc.), using transformers with split low-voltage windings, sectioning of electric networks with the ineffectiveness of other methods [1]. These methods may not be effective enough in a megalopolis if there is a large installed capacity of power plants and a large number of parallel short power lines forming a complex circuit. Short-circuit currents arising in such a system can significantly exceed the breaking capacity of the circuit breakers.

Network partitioning reduces network reliability. The inclusion of current-limiting reactors in power lines in complex-closed networks characterized by the presence of short power lines is ineffective. In addition, with the prospective development of the network due to the inclusion of new power lines, shunt lines with switched on current-limiting reactors, the efficiency of limiting short-circuit currents is reduced.

To control the flows of active power, it is possible to use DC inserts. The DC insert is a gap for the flow of short circuit currents, i.e. eliminates the "recharge" of the emergency site. However, the insertion of a direct current ensures the execution of one gap and, accordingly, one controlled connection for flows of active power.

Disclosure of invention

The objective of the invention is to increase the reliability of power supply through the use of multi-module DC inserts (MVPT). The increase in reliability lies in the fact that when such a device is introduced into the megalopolis power system, managed links are created between the network nodes, while there is no replenishment of the short circuit point on one of the lines of any node by currents from communication lines to other nodes through a multi-module DC insert. A significant effect of limiting short-circuit currents is observed when installing MHPT in substations having the greatest number of connections with power plants. At the same time, the system remains connected, the controllability of active power flows increases.

This method provides the limitation of short-circuit currents by means of the fact that electrical communication between consumers of electric energy and electric power sources is carried out through the multi-module DC insertion modules, the control and regulation devices of which support converter bridge currents at a level that provides permissible shutdown currents of high-voltage circuit breakers installed on alternating current buses current substation and adjacent power lines.

The number of MVPT modules m depends in the general case on the number of nodes located at the substation (alternating current lines or sections of alternating current buses) that need to be divided relative to each other by controlled connections.

The limitation of short-circuit currents with the help of MVPT is as follows: due to the fact that the m nodes of the alternating current at the substation are separated by converting modules, the feeding of the place of the short circuit on one of the lines of a node with currents from the lines of other nodes is excluded a controllable gap is artificially created in megalopolis networks. In this case, C (2, m) controlled electrical connections are formed:

The term "controlled electrical communication" means electrical communication between two converter modules connected to one common DC unit, which are controlled in accordance with the external characteristics of the converters operating as part of a single MHP.

For example, for a three-module insert (m = 3) the number of managed links is three, for a four-module insert, six, etc.

For bipolar regulation of active power flows at a substation with several power lines, controlled communication must be reversible and be carried out by changing the rectified current direction modules, which is ensured by the implementation of MVPT converters using counter-parallel connection of conventional thyristor valves or using valves on symmetric thyristors.

A device for limiting short-circuit currents and increasing the controllability of power flows in power systems - a multi-module DC insert - consists of m converter modules, each of which in the general case is a reversible controlled converter device of alternating current (or voltage) to constant, made one by one from well-known schemes. The converter modules on the AC side are each connected to their own node, and on the DC side, they are connected in parallel to common DC buses.

The implementation of the invention

The invention is illustrated by a diagram of a device for limiting short-circuit current and increasing the controllability of power flows in the power systems of figure 1. Consider a device, which, for example, consists of four converter modules 1-4, on the DC side connected in parallel to the DC bus 5, and on the AC side - on dedicated AC lines 6-9, and the device control and regulation system ( 2), which interacts between the central power controller 10 and the local power controllers 11-14 of the converter modules.

As an example, Fig. 3 shows a converter module 1, consisting of a multiphase (twelve-phase) current transducer 15 [2, 3], a filter compensating device 16 and a smoothing reactor 17. The multiphase current transducer 15 consists of a transformer transformer 18 and two valve bridges 19 and 20 (Fig. 3 shows one valve bridge 19) connected to the valve windings 21, 22 of the converter transformer 18.

Valve bridges are made according to a three-phase bridge circuit [2], in each arm of which two thyristor valves or a valve on symmetric thyristors 24 (in FIG. 3) are turned on and off for quick mode switching of the converter module.

On the DC side, the multiphase current transducer through the smoothing reactor 17 is connected to the DC terminals “+” and “-” to the DC buses. On the AC side, the network winding 23 of the transformer 18 is connected via a switch 24 to the AC line. The tertiary winding 25 of the transformer transformer 18 through a switch 26 is connected to a filter compensating device 16.

The device operates as follows.

The central power regulator 10 (Fig. 2) of a multi-module DC insert for one converter module, for example 4, sets the setting of the rectified voltage U _d , and for the remaining converter modules 1-3 sets the settings of the rectified current I _d . The settings of the rectified current I _d are formed from the condition of the balance of active powers

and are equal

where i = 1, 2, 3, 4.

The conversion mode (rectifier or inverter) of the converter modules is set according to the sign of the rectified current. The set points are the input signals of the local power controllers 11-14 of the converter modules 1-4. The local power regulator of the converter module according to the given setting of the rectified current I _d and the conversion mode of the converter module (rectifier or inverter) from the central power controller generates the settings for the thyristor turn-off and turn-on angles.

The technical result is:

- in limiting short-circuit currents in a metropolis in the presence of a large installed capacity of power plants and a large number of parallel short transmission lines forming a complex circuit due to the creation of a gap for the flow of short-circuit currents;

- in creating between the nodes of the energy system controlled communications with independent bipolar control of active power flows (or active and reactive power - when using modules based on voltage converters) due to the control and regulation system of the device;

- to minimize the number of converter modules per controlled link (for m> 3).

Information sources

1. Guidelines for the calculation of short circuit currents and the selection of electrical equipment. RD 153-34.0-20.527-98, ed. B. P. Neklepaeva, Publishing House NTs ENAS. M., 2006

2. Posse A.V. Schemes and modes of direct current power. L .: Energy, 1973.

3. Kochkin V.I., Nechaev O.P. The use of static reactive power compensators in electrical networks of power systems and enterprises. M .: Publishing House NTs ENAS, 2000

Claims (2)

1. A method for limiting short circuit currents and increasing the controllability of power flows in power systems, which consists in forming reversible controlled electrical connections at the required break points for the flow of short circuit currents by placing modules of a multi-module DC insert, the required number of controlled connections C and the required for them the formation of the number of modules m is related by

2. A device for limiting short-circuit currents and increasing the controllability of power flows in power systems is a multi-module DC insert consisting of m converter modules, each of which is a reversible controlled converter device of alternating current or voltage to direct, each connected to the AC side to its node, and on the DC side, parallel to the shared DC bus.

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