RU53081U1 - POWER SUPPLY SYSTEM - Google Patents

Abstract

The name of the utility model; power supply system. Field of technology: the utility model relates to electrical systems and can be used: to supply local consumers with electrical energy; as a source of electrical energy at transport facilities at a frequency of generated voltage from 50 to 400 Hz or more; for parallel operation with other electrical systems, including with centralized. Effect: simplification, cheaper system and increase its reliability. The technical result is achieved in that in a power supply system including a generator driven by a prime mover, a synchronous compensator and a capacitor bank connected by their output buses to a common power supply bus, the generator is asynchronous.

Description

The utility model relates to electrical systems and can be used:

- to supply electric energy to consumers of local importance;

- as a source of electrical energy in transport facilities (land, rail and water transport, aircraft) at a frequency of generated voltage from 50 to 400 Hz or more;

- for parallel operation with other electrical systems, incl. with centralized.

A centralized electrical system is known, which is a combination of power plants, power lines, substations and distribution networks, interconnected due to the continuity of the process of production and consumption of electric energy into one whole by a common operating mode. (Electrical reference book. Volume 2. Book One. Energy, Moscow, 1972, p. 476) The disadvantage of this system is their centralized purpose, which leads to difficulties in the practical implementation of technical measures for connecting local consumers to power lines (power lines) with voltage above 10 kV, as well as to the distribution networks of 10, 6 and 0.4 kV centralized systems.

The closest to this decision on technical essence is the power system in the form of stationary and mobile power plants of electric trains, ship and ship power stations, aircraft, including a generator connected via output buses with a common power supply bus, a primary engine used as a generator drive, a synchronous compensator and a capacitor bank ( Electrotechnical Reference Book, Volume 2. Book One, Energy, Moscow, 1972, p. 476). The disadvantage of this technical solution is that synchronous generators (SG) are used as sources of electricity. With a lack of generated power for parallel operation of the SG in the electrical system, the use of complex and expensive

automated devices for synchronizing the SG at the moment of switching on parallel operation and distribution of reactive loads between them in proportion to the rated power of each of them. In addition, the specified technical solution is difficult when performing installation work.

The task to which the described utility model is directed is to create simple, reliable and inexpensive power systems. The problem is solved by the use of asynchronous generators in the power system, for the excitation and regulation of voltage of which, as well as to stabilize the frequency of the alternating current at a given level, to provide consumers with reactive power, use a synchronous compensator with automatic voltage regulation. Asynchronous generators and consumers of electricity are supplied with reactive energy from a synchronous compensator (s) with automatic regulation and stabilization of the voltage of the power system centrally. At the same time, the technical problem of starting and operating asynchronous motors with a power commensurate with the power of the asynchronous generator (s) was solved.

The essence of the proposed autonomous power supply system is as follows:

An asynchronous electric machine, at a speed greater than synchronous, switches from motor mode to electric power generator mode, transferring only active power to the network and consuming reactive power from the network for its operation, while the alternating current frequency is determined by the frequency of the network and does not depend on the rotational speed of the rotor of the asynchronous generator . Therefore, when an asynchronous generator is operating, for its excitation and voltage maintenance at a given level, an adjustable source of reactive power and AC reference frequency is required. These requirements of the asynchronous generator are fully met by the capabilities of the synchronous compensator. On the other hand, a synchronous compensator for its operation requires only active power from the network, which is fully met by the capabilities of an asynchronous generator. Thus, the use of a synchronous compensator in an autonomous power supply system ensures the start-up and operation of asynchronous generators. For unloading

synchronous compensator asynchronous motors are compensated by capacitors.

The distribution of active power between asynchronous generators is carried out using automatic regulators of primary engines.

The combination of an asynchronous generator and a synchronous compensator in one system, in which the requirements for the energy system of one of them are fully satisfied by the capabilities of the other, and the combined capabilities of these elements with partial compensation of reactive currents by a capacitor fully satisfy the requirements of consumers of electric energy, indicating the achievement of the set tasks.

Parallel operation of asynchronous generators among themselves, as well as their connection to other power systems, including centralized ones, can be done without the use of complex automatic synchronization devices.

So, the technical result achieved by the application of this utility model is to simplify and reduce the cost of the well-known energy systems listed above, while increasing their reliability, especially under peak loads, due to the stability of the electromechanical system represented by the relationship of an asynchronous generator with a synchronous compensator.

To achieve the aforementioned technical result, the power supply system includes a generator connected by means of output buses with a common power supply bus, the rotor of which is coupled to the shaft of a variable speed primary motor used as a generator drive, a synchronous compensator, the output of which is connected in parallel with the generator and a capacitor bank . The generator according to the present utility model is made asynchronous.

The essence of the utility model is illustrated by drawings, on which, in Fig. 1, is a schematic electrical diagram of the power system; figure 2 is a diagram of an electrical system of local value of 0.4 kV.

The power system (see Fig. 1) includes at least one electric generator 1, consisting of an asynchronous generator 3.1 connected to the corresponding output bus 2 and driven by the prime mover 4.1, at least one synchronous compensator 5 connected to the corresponding output bus 2, and at least one capacitor bank 6.1,

connected to the corresponding output bus 2. Moreover, the indicated output buses 2 of the asynchronous generator 3.1, the synchronous compensator 5 and the capacitor bank 6.1 are interconnected by switches 7.1, 7.4, 7.5 forming a common power supply bus 8.

An asynchronous generator is a low-cost, reliable serial induction motor, turned into a generator mode.

As an asynchronous generator 3.1, an squirrel-cage induction motor, for example, series 4A or 5A, can be used.

As the primary engine 4.1, gasoline engines, diesel engines, gas engines, turbines (gas, steam, hydraulic), wind engines, etc. can be used.

As a synchronous compensator 5 can be used asynchronous serial motors with a phase rotor, for example, series 4ANK or 5ANK.

Serial capacitors can also be used as a capacitor bank.

The power system operates as follows.

Synchronous compensator 5 provides the excitation of the asynchronous generator 3.1 and the supply of reactive energy to consumers, especially in transients at the moment of switching on the induction motors with a power comparable with the power of the electrical system.

The use of synchronous compensators 5 with an automatic excitation system provides voltage stabilization of parallel-running asynchronous generators 3.1, 3.2, 3.3.

Let us explain the operation of the power system by the example of an electric system of local value 0.4 kV.

Figure 2 shows a diagram of an electrical system of local value 0.4 kV in the form of a fragment or a private implementation of the many possible circuit solutions.

The local power line consists of power transformers 9.1, 9.2, 9.3 with switching devices 10.4, 10.5, 10.6: 10.1, 10.2, 10.3 for connecting a local electrical system to a centralized power system or other power systems. Switching device 11 is used to connect a local distribution network of 0.4 kV.

Primary motors 4.1, 4.2, 4.3 drive asynchronous generators 3.1, 3.2, 3.3. The active power of each is P _i kW.

Electric units 3.1-4.1, 3.2-4.2, 3.3-4.3 have automatic speed controllers. Asynchronous generators 3.1, 3.2, 3.3 are connected to the network at a sub-synchronous speed with simple switching devices 7.1, 7.2, 7.3, like transformers at idle. Synchronous compensator 5 has an automatic excitation control system, for example, similar to the phase compounding system used on synchronous machines. Capacitor banks 6.1, 6.2 are used for partial compensation of reactive energy. They are connected by switching devices 7.5, 7.6.

The commissioning of electrical units 3.1-4.1, 3.2-4.2, 3.3-4.3 is carried out in the following sequence:

1. One of the prime movers, for example 4.1, is started and displayed at the rated speed.

2. The capacitor bank 6.1, designed to excite the asynchronous generator 3.1, is connected to the bus 0.4 kV switch 7.5.

3. The synchronous compensator 5 is started from the asynchronous generator 3.1 by turning on the switch 7.1. In this case, the starting current of the synchronous compensator 5 should be limited by a common method - by introducing starting resistance in the phase rotor of the induction motor.

4. When the synchronous compensator 5 reaches the sub-synchronous speed, the starting resistances are automatically or manually disconnected from the rotor, and a direct current is introduced into the rotor, for example, from the phase compounding system of the synchronous compensator 5. A stable electromechanical system 3.1-5 is formed.

5. The primary engines 4.2 and 4.3 are started alternately and are output by the frequency controllers to the sub-synchronous speed.

6. By alternately turning on the switches 7.2 and 7.3, asynchronous generators 3.2 and 3.3 are connected to 0.4 kV buses. At the moment of switching on, in each of the generators there are no starting currents, since the connection of unexcited generators 3.2 and 3.3 occurs at zero rotor currents. Asynchronous generators 3.1, 3.2, 3.3 form with a synchronous compensator 5 a stable electromechanical system, ready to receive the load.

7. The commissioning of asynchronous generators 3.1, 3.2, 3.3 is made by connecting a local 0.4 kV network to 0.4 kV buses.

A stable electrical system is formed from the electromechanical system of electrical units 3.1-4.1, 3.2-4.2, 3.3-4.3 and a local electric network of 0.4 kV.

As the load in the local network of 0.4 kV increases smoothly, the rotation frequency of each of the electrical units must simultaneously increase with the help of automatic regulators of each of the units in proportion to the slip. Thus, the frequencies in the electrical system are set given, for example, 50 Hz, in accordance with GOST tolerances. The voltage on the tires is maintained at 0.4 kV within the established tolerance according to GOST.

Transient processes in an electric system of local importance can occur at the moment of switching on or off loads with a capacity comparable with the capacity of the electric system asynchronous generator - synchronous compensator.

Turning on and off asynchronous motors with a power commensurate with the capacity of the asynchronous generator - synchronous compensator system is especially hard to perceive. In this case, there is a shortage of reactive energy for the formation of magnetic fluxes in the gaps of all asynchronous machines of the electrical system, including working asynchronous generators, in asynchronous motors operating under load and, especially, in the starting mode (short circuit mode at very low cosφ = 0.2-0.3). With this transient process, the stability of the local electrical system is ensured by forcing the excitation current of the synchronous compensator using, for example, a high-speed phase compounding system.

Almost synchronous compensator 5 should work at a load of its stator by 50% at a rated load of asynchronous generators 3.1, 3.2, 3.3. At the time of forcing, the power of the synchronous compensator 5 can exceed its rated power by about 2.5 times during the transient t _p ≈ 3.0 s. In this case, the voltage on the tires is reduced to an acceptable value, but not lower than 300 V on the 0.4 kV buses. When the load is disconnected, the synchronous compensator 5 acts in the reverse order. For

to facilitate the operation of the synchronous compensator 5 with a switch 7.6, a capacitor bank 6.2 is connected.

The shutdown of some units 3.1-4.1, 3.2-4.2, 3.3-4.3 can be carried out according to the established rules at power plants - by gradually reducing the energy supply to the prime movers 4.1, 4.2, 4.3 with the help of the speed controller of the switched-off unit and turning off the asynchronous generators 3.1, 3.2, 3.3 from tires 0.4 kV.

The connection of the local electrical system to the centralized power system is carried out in the following order:

1. A local network of 0.4 kV is connected to a centralized power system or other power systems through transformers 9.1, 9.2, 9.3 through the appropriate switching equipment 10.4, 10.5, 10.6, 10.1, 10.2, 10.3. In this case, the synchronous compensator 5, asynchronous generators 3.1, 3.2, 3.3 are disconnected from the busbars 0.4 kV.

2. Asynchronous generators 3.1, 3.2, 3.3 are connected to 0.4 kV busbars in the previously established order, i.e. at sub-synchronous speed, non-excited, without synchronization system. In this case, preliminarily, 0.4 kV busbars must be supplied with voltage from a centralized power system or other power systems. Asynchronous generators 3.1, 3.2, 3.3 are loaded with the help of frequency controllers in the previously established order. In this case, the voltage and frequency on the busbars is determined by a centralized power system or other leading power systems.

There are other possible operational switching in the current electrical system, not contradicting the established rules of the PUE.

Tests have shown that the capacity of the proposed local electrical systems can range from a few kW to several MW.

Claims (1)

The power supply system, including a generator connected by means of output buses with a common power supply bus, a prime mover used as a generator drive, a synchronous compensator and a capacitor bank, characterized in that the generator is made asynchronous.