SU955356A1 - Device for coupling two power systems - Google Patents

Description

(54) DEVICE FOR COMMUNICATION OF TWO ENERGY SYSTEMS

one

FIELD OF THE INVENTION The invention relates to electrical engineering, in particular, to devices for the connection of alternating current sources.

Devices are known which are asynchronized synchronous electromechanical frequency frequency converters (HP EMF). AC EMPC consists of either a synchronous machine and an asynchronized synchronous machine with rigidly connected shafts l, or of two asynchronized synchronous machines with rigidly connected shafts 2.

In these devices, the input of the thyristor frequency converter of the excitation system of each asynchronized synchronous machine is connected to its stator windings, which during slip operation reduces the total throughput of the device and degrades the quality of electrical energy on the buses of asynchronized synchronous machines, since the thyristor frequency converter is a source of subharmonic oscillations reactive power.

The closest to the present invention is a device for flexible communication of power systems, containing two asynchronized synchronous machines with rigidly connected shafts, the stator circuits of which are connected to the corresponding power system, and static control converters connected to the switch are connected to the rotor circuits of the machines a control unit connected to both power systems, and two frequency sensors, each of which is connected to a corresponding power system. The connection to one or another energy system is carried out on the basis of a comparison of the signs of the voltage of the active power flows in the stators and rotors of machines p,

The disadvantage of known devices

20 is a deterioration in the quality of electrical energy in the power system, to which the inputs of thyristor frequency converters of asynchronized excitation systems are connected.

25 synchronous machines. It is known that thyristor frequency converters with direct connection and natural commutation (cycloconverters) are used to excite asynchronized synchronous machines. The reactive power consumed by cycloconverters from the mains is amplitude modulated with the secondary network frequency. In the prototype device, the supply network is the network to which the stator windings of the asynchronized synchronous machine are connected, and the secondary network is its excitation windings. Therefore, the reactive power of the cycloconverter will be amplified with the slip frequency of the asynchronized synchronous machine. Moreover, the number of oscillations of reactive power values during a slip period of an asynchronized synchronous machine depends on the number of phases of the excitation winding. During the slip period of a two-phase rotor, there will be four oscillations, a three-phase rotor - six oscillations. The depth of oscillations of a scientific research institute in normal mode is the greater, the smaller the number of rotor phases and the range with which the asynchronized synchronous machine operates. So with close to zero slip, the oscillation depth of the value of reactive power at the cycloconverter input is about two and three phase rotors, respectively, about 30% and 14% of its maximum value. If in parallel several asynchronized synchronous machines of the APS EMP units are working, the absolute value of the oscillations of the reactive power increases accordingly. This, as mentioned above, degrades the quality of electrical energy in the excitation circuit of the device’s machines. The purpose of the invention is to improve the quality of electrical energy in the electrical network, to which static frequency converters of asynchronous excitation systems are connected, of synchronous machines of a communication device. This goal is achieved by the fact that a device for connecting two power systems, comprising a unit of two electric machines with rigidly connected shafts; one of which is an asynchronized synchronous, the stator windings of the machines are connected to the corresponding power system, a static frequency converter with a regulator connected to a switch with a control unit connected to both power systems, and two frequency sensors, each of which are connected to the corresponding power system, the second electric machine of the first aiperaTa is made synchronous, the device is equipped with the second unit from electric machines, one of which is asynchronized synchronous, and the second - synchronous, second frequency converter with a regulator connected to the rotor circuits of the second asynchronized synchronous machine and a transformer connected between the terminals of both static frequency converters and a switch, with each field winding the asynchronous synchronized machine is shifted relative to the corresponding axis of the excitation winding of the synchronous machine of its unit. The transformer can be made double winding, and the angle of displacement of the excitation windings of machines of one unit is q-cp. + D - i) KV, where Cpg is an arbitrary angle that is the same for all units; the number of units connected in parallel; the number of phases of the excitation winding of the asynchronized synchronous machine; i is the unit serial number; K Oh, 1, 2 ...; and, - respectively, with a two-phase rotor. The transformers can be made three-winding, the excitation windings of asynchronized synchronous machines are three-phase, the secondary inputs of static frequency converters are connected to different groups, and the specified electrical angle of the excitation windings is 1) .1% + Ktf). Figure 1 shows a diagram of the proposed device, with a double-winding transformer; Fig.2 is the same with a three-winding transformer. A device for connecting two power systems (Fig.1) contains two units, the first of which consists of an asynchronized synchronous machine 1 and a synchronous machine 2, the second unit is made of an asynchronized synchronous MC1 BUS and 3 synchronous machine 4. The excitation windings of the asynchronized synchronous machines 1 and 3 are connected to the outputs of the static converters 5 and 6, respectively, of the frequency, which are controlled by regulators 7 and 8. The inputs of the static converter 5 th and 6 are connected to the switch -tsastoty static converters 9 inputs through the transfer-rate, Matora 10 first contacts which

connected to one power system, the second contacts to another power system. The inputs of the switch control unit 11 are connected to the sensors 12 and 13 of the frequencies of the combined power systems.

To use the device in full capacity, the inputs of static converters 5 and b of the frequency of the excitation systems of asynchronized synchronous machines 1 and 3 are connected by means of a switch 9 to one of the interconnected power systems. Connection to this or another power system is carried out on the basis of mutual comparison of the frequencies of the power systems in the switch control unit 1.1. Sensors 12 and. 13 frequencies produce signals proportional to the frequencies of the power systems. These signals go to block 11, which controls the operation of switch 9 so that the static transducer inputs. The frequency band is always connected to the power system at a lower frequency. As follows from the above, for controlling switch 9, only two signals of the frequency of connected power systems are needed, whereas for control of switch 9 in the prototype device, four parameters are used — the active powers of the stators and rotors of both machines. At the same time, it is very problematic to ensure the measurement of active power in rotor circuits, since the frequency of the currents and excitation voltages is small (not more than 1.5 Hz).

In addition, in the proposed device, the excitation winding of the asynchronized synchronous machine of each unit is multi-phase with respect to, for example, the longitudinal axis of the excitation winding of its synchronous machine at a certain electric angle. I

The excitation windings of machines 1 and 3 shown in Fig. 1 are two-phase. At the same time, the longitudinal axes of the phases of the excitation windings of machines 1 and 3 are displaced in space by 45 e. hail, (angle between axes d and 32). Since both transducers 5 and 6 are powered by a single excitation source, then for dzhfaznyh excitation windings of machines for a period. the slip of their suglmarn reactive power will have eight oscillations. At the same time, the depth of oscillations of reactive power is halved in relation to the prototype device. This happens due to the fact that the mutual shift of the excitation windings of machines by the specified angle provides mutual phase shift by the same angle of oscillation of the reactive powers of the static frequency converters 5 and 6. When performing excitation windings 1 and 3 three-phase (the shear angle between the longitudinal axes of the phases of the excitation windings of machines 1 and 3 is 30 electr.) The total reactive power oscillations at the inputs of static converters 5 and 6 frequencies during the slip period doubles and makes twelve, and the oscillation depth is also halved compared with the prototype device.

As you can see, reducing the depth of oscillations of the total reactive power at the inputs of static converters 5 and b frequency for connecting two power systems improves the quality of electrical energy in the power system,

0 which they are connected to using the switch.

FIG. 2 shows a device for communicating two power systems when two units are connected in parallel, each

5 of which contain one asynchronized synchronous machine with a three-phase field winding. In this case, there is the possibility of not only the mechanical displacement of the systems of the multiphase windings of the machines 1 and 3 at the specified electrical angle, as is done in the device in Fig. 1, but also the electrical displacement. This is achieved as follows. The primary winding of the three-winding transformer 10 is connected to the output of the switch control unit 11. One of the secondary windings is connected to frequency converter 5, and the other to frequency converter b. With

In this, the secondary windings of the transformer 10 are connected in different groups, for example, U / U / D-12-11, and the systems of the multiphase excitation windings of machines 1 and 3 (Fig. 2) are not displaced relative to each other. In this case, the electric offset by the specified electrical angle in the DZ for the three-phase excitation windings of the machines 1 and 3 is provided by

0 secondary windings of a transformer 10.

The power of the static frequency converters 5 and 6 is carried out through a common transformer 10 and switch 9. But each static

5 frequency converter can be equipped with its own transformer and switch.

The invention can be applied

Claims (3)

0 both for combining two power systems with different nominal frequencies, and for uniting power systems with the same nominal frequencies, but having mutual frequency oscillations. Moreover, the quality of electrical energy in the grid, to which the inputs of static frequency converters of excitation systems of asynchronized synchronous machines are connected, the better, the larger the total number of parallel-connected AC EMP units, and hence static frequency converters. The device can be applied if the excitation of asynchronized synchronous machines of the aggregates is carried out from a common excitation machine of alternating current, for example, a special synchronous machine. Claim 1. Device for communication of two power systems, comprising a unit of two electric machines with rigidly connected shafts, one of which is made of asynchronized synchronous stator windings of machines connected to the corresponding power system, a static converter connected to the rotary circuit of the asynchronized synchronous machine a frequency with a controller, associated with a switch with a control unit connected to both power systems, and two 1Mi sensor frequencies, each of which is connected To the corresponding power system, characterized in that, in order to improve the quality of electrical energy in the power system, the second electric machine of the first unit is synchronized, it is equipped with a second unit of two electric machines, one of which is asynchronized synchronous, and the second is synchronous, repeat a frequency converter with a regulator connected to a rotary circuit of a second asynchronized synchronous machine, and a transformer connected between the terminals of both static converters frequency and a switch, while the excitation winding of each asynchronized synchronous machine is shifted relative to the corresponding axis of the excitation winding of the synchronous machine of its unit. 2. The device according to Claim 1, which means that the transformer is double-wound, and the bias angle of the excitation windings of the machines of one unit is Cfg, an arbitrary angle that is the same for all units; n is the number of units connected in parallel; t is the number of phases of the excitation winding of the asynchronized synchronous machine; 1 is the unit serial number, 1, 2 ...; at at a two-phase rotor; (- with a three-phase rotor. 3. The device according to claim 1, characterized in that the transformer is made three-phase, and the windings to which static frequency converters are connected are made with different winding connection schemes, and the excitation windings of asynchronized synchronous machines are three-phase, the specified electrical the angle is Cf q; o Kc). Sources of information taken into account in the examination 1. The author's certificate of the USSR 600662, cl. H 02 J 3/06, 1976. 2. Authors certificate of the USSR 502445, cl. H 02 J 3/06, 1976. 3. Authors certificate of the USSR W 729746, cl. H 02 J 3/06, 1977.