SU1557626A1 - Device for coupling two power systems - Google Patents

Abstract

The invention relates to electrical engineering, in particular to devices for flexible communication of alternating current sources. The purpose of the invention is to improve the quality of electricity in the power system. As a phase shifter 5, a phase switch is used, which is necessary to transfer an asynchronized machine 1 from one mode to another when excited from an auxiliary asynchronized synchronous generator 2. If prior to switching machine 1 worked in a motor mode when connecting the moving contacts of the phase shifter 5 respectively to phases A, B and C of the network through transformer 6, then after switching when changing the direction of power flow, the moving contacts of phase shifter 5 will t connected respectively to the phases b, c and a network. This will correspond to the generator mode of machine 1. Synchronous machine 3 will operate in motor mode. The power flow is regulated by varying the magnitude of the excitation current of the machines. In machine 1, this is accomplished by means of an excitation control unit 4 receiving a control signal from the error block 7 about the required amount of power flow. The power system detection unit 8 with a power shortage determines the magnitude and direction of the required power flow from one power system to another by comparing the parameters of two power systems, such as frequencies. 2 Il.

Description

fit / e. one

315

water of an asynchronized machine 1 from one mode to another when excited from an auxiliary asynchronized synchronous generator 2 "If prior to switching machine 1 worked in motor mode when connecting the moving contacts of phase-shifting device 5 respectively to phases A, B and C of the network through a transformer 6 then, after switching when changing the direction of the power overshoot, the moving contacts of the phase shifter 5 will be connected respectively to phases B, C and A of the network c This will correspond to the generator Machine mode 1

Synchronous machine 3 will operate in motor mode. The power flow is regulated by varying the magnitude of the excitation current of the machines. In machine 1, this is accomplished by means of an excitation control unit 4 receiving a control signal from the error block 7 about the required amount of power flow. The power system detection unit 8 with a power shortage determines the magnitude and direction of the required power flow from one power system to another by comparing the parameters of two power systems, for example, frequencies, 2 or less.

The invention relates to electrical engineering, where where -f is the voltage frequency

at the exit of the WASH 2.

devices, namely, devices for flexible communication of AC sources.

The purpose of the invention is to improve the quality of electricity in the power system.

Fig. 1 shows a device for connecting two power systems; in fig. 2 - phase switch.

The device for communication of two power systems contains an asynchronized synchronous machine (AFM) 1 and an auxiliary asynchronized synchronous generator (VASG) 2 with the same number of pole pairs, a synchronous machine (CM) 3, block 35 4 of excitation control, phase the shifting device 5 is a three-phase transformer 6, a mismatch block 7 and a power deficiency detection unit 8 (BWEDDM).

The phase shifter 5 uses a phase switch containing moving contacts and stationary contacts of phase A 12 and 13, phases 14 and 15, and phases C 16 and 17, as well as the switch actuator 18. The phase shifting device 5 is connected to the transformer 6 from the fixed contacts 12-17.

Due to the fact that for excitation of AFM 1, VASG 2 is used, having with it an equal number of pole pairs connected to the same power system through a three-phase transformer 6, the voltage frequency at the output of the AFM 1. is set by VASG 2:

40

45

50

55

The frequency f4 does not depend on the shaft rotation frequency, given by CM 3, equal to n, i.e. WASG 2 Provisions

normal electromechanical communication in frequency between power systems

In order to achieve the minimum power loss for WASH 2, and therefore its minimum dimensions and maximum efficiency, it is necessary to ensure sufficient slip in it, i.e. sufficient & f0

-Li- JU- Pa PC

about 1.5 times or more, which, for example, with equality of the nominal values of the frequencies f, and f2 is reached with pc, tg the number of pairs

Jq smaller p

ratio pa and poles pc

Power flows between energy systems can be ensured by operating AFM 1 and CM 3 in different modes: one in the motor mode, the other in the generator mode, depending on the direction of the power flow.

A phase shifting device 5 does not exist to switch the CM 3 from the mode to the mode of difficulty, and the phase shifter 5 is needed to switch the AFM 1 from one mode to another when excited from WASH 2, otherwise it is impossible to create the necessary AFM response that determines the machine

f He f 1 60 Q

.-Ј

five

0 5

0

five

0

five

The frequency f4 does not depend on the shaft rotation frequency, given by CM 3, equal to n, i.e. WASG 2 Provisions

normal electromechanical communication in frequency between power systems

In order to achieve the minimum power loss for WASG 2, and, consequently, its minimum dimensions and maximum efficiency, it is necessary to ensure sufficient slip in it, i.e. sufficient & f0

-Li- JU- Pa PC

about 1.5 times or more, which, for example, when the nominal values of the frequencies f are equal, and f2 is reached equal to,

Jq smaller p

ratio pa and poles pc

Power flows between power systems can be ensured when the AFM 1 and CM 3 are operating in different modes: one in the motor mode, the other in the generator mode, depending on the direction of the power flow.

A phase shift does not exist to switch the CM 3 from the mode to the mode, and a phase shifter 5 is necessary to transfer the AFM 1 from one mode to another when energized from WASH 2, otherwise it is impossible to create the necessary AFM response that determines the mode

It is possible to use phase-shifting devices on reactive elements, but they increase the size of the system and increase its cost. The proposed device uses a phase switch, which shifts the stator magnetic field, and, consequently, the three-phase rotor system of the VASG 2 rotor by 120 eLograd, which creates a rotating magnetic field in the AFM 1 rotor, also shifted by 120 electros0. Suppose that before switching, the AFM 1 operated in motor mode, i.e. the magnetic field of the rotor of the AFM 1 lagged behind the magnetic field of the stator by 60 electr., when the first 9, second 10 and third 11 mobile contacts of the phase-shifting device 5 were connected to the A, B and C phases of the network (fixed contacts 12, 14 and 16) through the transformer 6. After switching, when the power flow changes direction, the first 9, second 10 and third 11 mobile contacts are connected respectively to the network B, C and A phases (fixed contacts 15, 17 and 13), resulting in a rotor magnetic field The ACM 1 is shifted by 120 degrees. in the direction of advance and the magnetic field of the rotor is ahead of the magnetic field of the stator by 60 degrees. This corresponds to the generator mode of the AFM 1. CM 3 operates in the opposite mode. The power flow is controlled by changing the magnitude of the excitation current of the machine B AFM 1, this function is carried out by the excitation control unit 4 by receiving a control signal from the error block 7 of the required power flow.

The excitation control unit 4 is made of anti-parallel thyristor pairs included in each phase; controlling the excitation current in it by changing the opening angle of the thyristors determined by the signal from the error unit 7 When the thyristors do not work, there are no subharmonic oscillations in the network Thus, the thyristors operate at a frequency equal to the network frequency, and block 4 is not a frequency converter.

BVEDM 8 determines the magnitude and direction of the required power flow from one power system to another

ten

five

20

five

by comparing the parameters of two power systems that characterize the lack of power in the power system, for example, frequencies In this case, it should be performed on the basis of sensors. power system frequencies The constant difference signal in frequency obtained in BVEDM 8, the polarity of which depends on the frequency ratio, is used to control the device through the error block 7; The error block 7 converts this signal into two types of signals: a signal with a variable polarity, depending on the required direction of the power flow, to control the phase shifter 5 and a signal having a constant polarity, but with a value that depends from the required amount of power flow, to control the excitation control unit 4. A signal of constant polarity can be obtained using a full-wave rectifier.

Thus, the use of two VASG power systems connected to the AFM exciter circuit, as well as an excitation control unit, a phase-shifter, a mismatch unit, and a BWEDDM, in the device for connecting, improves the power quality, since the device does not contain triac inverters contributing subharmonic oscillations of reactive power and deteriorating power quality,

Claims (1)

Q claims A device for the communication of two power systems comprising a unit of two electric machines placed 5 on one shaft, one of which is an asynchronized synchronous with a three-phase rotor, the other is synchronous, the stator windings of the machine are connected with each clamp for JQ connection to the corresponding power system, a three-phase transformer, characterized in that, in order to improve the quality of electricity in the power system, it has an auxiliary asynchronous synchronous generator placed on the shaft of the unit and having an equal number of pole pairs with an asynchronized synchronous machine, a rotor5 The windings of these machines are interconnected, the excitation control unit connected to the stator of the auxiliary asynchronized synchronous generator, phase-shifting device to the input of which the secondary winding of the transformer is connected, the primary winding of the transformer is connected to the terminals for connection to the power system connected to the asynchronized synchronous generator machine, the phase-shifter output is connected to the input of the excitation control unit, the propagation unit, the outputs of which are connected the control inputs of the phase shifter and controlling the driving unit, the detection unit to the power grid deficit sub- 12 15 9 t ha where f. and f "connected to the terminals for connection to the power systems and to the input of the error block, and the number of pairs of poles of the machines are chosen according to the condition of inequality Ji JK PC the frequencies of the power systems to which the synchronous machine and the synchronous machine are connected respectively; the number of pairs of poles, respectively, of the asynchronization of the nth synchronous machine and the synchronous machine. P and PC 18 JU.zi / J eleven 0 / ffЈ / rff / fa paccoesra- cofartvfi Fie.2