DK145029B - POWER SUPPLY UNIT FOR SHIP GENERATOR - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a constant-frequency AC power supply system on ships with a widely varying rpm synchronous generator as a shaft generator, after which an uncontrolled rectifier and a grid-controlled inverter are provided and provided with at least one synchronous mask. which serves as a blind power machine and which has a control device which sets the synchronizing current of the synchronous machine to obtain a constant mains voltage.

There are known power supply systems with shaft generators, in which the shaft generator designed as a three-phase alternator rotates with varying rpm and is magnetized by a turning field, the size and frequency of which is set in such a way that a three-phase alternating supply provided by the shaft generator is constant. constant frequency.

Such shaft generator systems require greater expense, especially when designed for small rated rpm. The shaft generator then has many poles and a small air gap. It is also a disadvantage that a costly inverter is required in order to produce the variable frequency range and magnitude for magnetization of the shaft generator.

Furthermore, a shaft generator known as a DC machine is known. By means of a direct current motor driving a three-phase alternator, the ship's network is supplied with three-phase alternating current. When controlling the magnetization of the DC machine, the frequency is kept constant, and when controlling the magnetization of the three-phase alternator, the voltage in the ship network is kept constant. Also this shaft generator-35 system with commutator machines is relatively expensive.

145029 2 1 In addition, this system requires a lot of space and constant care.

It is also known to use, as a shaft generator, an a-5 synchronous machine that operates oversynchronously. The required constant frequency is provided by means of an adjustable load circuit consisting of a rectifier and a DC motor. The secondary winding of the asynchronous machine feeds the rectifier to which the DC motor is coupled 10. after. The power obtained from the secondary winding is preferably returned to the grid by means of a synchronous machine coupled to the DC motor, whereby the synchronous machine simultaneously supplies the blind power required for the asynchronous machine. At this plant, 15 also apply the disadvantages mentioned for the devices already mentioned. As a disadvantage, it should be pointed out in particular that this plant is not self-starting. The shipping network must already be live when the asynchronous machine serving as a shaft generator is switched on.

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Furthermore, a shaft generator system is known in which the shaft generator generates the three-phase alternating current which is rectified and is again converted to three-phase alternating voltage by means of an autonomous inverter. However, self-controlling inverters are costly and complicated, since means are needed to generate the blind and commutation currents. Furthermore, to obtain a fairly sinusoidal output voltage, filter circuits are required. Finally, it is difficult to take protective measures against short circuits, as the autonomous inverter cannot supply a short-circuit current that can fuse the fuses.

The object of the invention is therefore to provide a power supply system for ships to produce a constant frequency AC voltage which can be economically produced with simple means and at low cost, and which, in the short term, also does not fail and can be removed. In operation, the grid is already live. This object is fulfilled by the shaft generator having a control device which sets the shaft generator's magnetization current to obtain a constant frequency and that the synchronous machine in shaft generator operation is permanently connected to the inverter output and the ship network.

The main advantage of the supply system according to the invention consists in the fact that the costs compared to known plants are very low and that a good control of frequency and voltage is ensured in the supplied ship network at any frequency of the shaft generator.

According to claim 2, the system can be characterized in that a net choke coil is connected between the synchronous machine and the ship network. The compounding or regulating means of the synchronous machine are hereby dimensioned in such a way that the voltage drop at the mains coil is equalized, so that the ship network voltage remains constant.

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According to claim 3, the system can be characterized in that the mains coil has an outlet to which the synchronous machine is connected. This measure is advantageous in that the choke acts as a transformer and at a short circuit in the ship network provides a higher voltage at the output of the inverter than is the case with a direct connection of the synchronous machine to the inverter.

The system according to claim 4 can be characterized in that v: -v ·; ·· '145029 4 1 a ship network generator is used as a synchronous machine, which ship generator in the shaft generator operation is disconnected from its auxiliary power machine. Hereby it is obtained that the auxiliary machine does not have to rotate at idle when the shaft generator is in operation.

Finally, the system according to claim 5 can be characterized in that the synchronous machine is switched directly to shaft generator-10 when started without the aid of a primary motor. clean by bypassing the rectifier and inverter, whereby the inverter receives no ignition pulse. .. This achieves that the shaft generator system can: be put into operation without a sufficiently strong network available for starting the vision. 15 The crown machine, When the inverter receives no ignition pulses, it does not conduct any current.

The invention is further explained with reference to the drawing, in which:

FIG. 1 shows a principle diagram of a supply system according to the invention; FIG. 2 shows an advantageous further development for connecting the synchronous machine, and fig. 3a, 3b, 3c show the setting of the ignition angle of the controllable valves in the inverter.

A shaft generator 10 (Fig. 1) with a magnet winding 11 and an anchor winding 12 driven by a propeller shaft 13 feeds an uncontrolled rectifier 14.

Further to rectifier 14, there is connected a grid controlled inverter 15 which feeds a ship network 16. A synchronous machine 17 is further connected to the output of the inverter 15 as a ship generator which is connected to a diesel generator by means of a switchable coupling 18 - hole 19.

5 The synchronous machine 17, which in the operation of the shaft generator 10 is firmly connected to the inverter output and the ship network 16, fulfills several functions. It, on the one hand, fully or partially covers the blind power needs of the shipping network 16 and, on the other hand, the need for commutation current to the inverter 15 and thus provides a commutation aid to the inverter. Furthermore, the synchronous machine 17 constitutes a filter circuit for the overtones of the inverter 15.

In order to obtain a constant voltage at the output of the synchronous machine, a compound device can also advantageously be used.

The shutter output of the shaft generator 10 is proportional to the differential voltage between the voltage of the synchronous machine 17 and the voltage of the shaft generator 10. The need for the inverter current blind and commutation current is thereby proportional to the output of the blind generator 10. If the power output now rises dynamically due to an external disturbance, the voltage drops on the inverter 15 output, while the synchronous machine 17 must output a larger blind. effect. If the voltage at the rectifier input is maintained dynamically, the differential voltage will be increased and the power output will thus be further increased. The plant will thus be unstable; power increases across all boundaries.

The shaft generator 10 has a dynamic relationship whereby the voltage at a larger scale current increase - -; 14, as is the case with the synchronous machine 17.

This ratio of the shaft generator 10 is obtained, for example, in that it has a relatively large short-circuit reactance. Hereby, a synchronous machine as a shaft generator 10 can be arranged without damping winding with the added advantage that the synchronous machine without damping winding is less expensive than one with damping winding 10. A comparator 20 for a control device for the synchronous machine 17 compares the voltage of the ship network 16 with a desired voltage. The control deviation is sent to a regulator amplifier 21 to which the magnetizing winding 22 of the synchronous machine 17 is coupled. Thus, the synchronous machine also keeps the ship's grid voltage constant when it runs without idle as a phase shifter.

In order to control the ship network frequency, an additional control device 28 for the shaft generator 10 is used. Here, the frequency of the ship network voltage is compared with a predetermined desired value at the comparison site 27 and amplified in the regulator amplifier 28. It is known in this context that a symmetrically efficient 25 distribution of several parallel generators on a grid can be achieved by giving all drives the same rpm and the same idle characteristic. Thus, the frequency regulator 27, 28 'is equipped with the same decreasing characteristic as the ship network generator speed regulator. As a result, in practice, the frequency is kept load independent and constant, just like the frequency of the ship network generator. With this prerequisite, the shaft generator can work with any large grid that is fed by several ship network generators, and it can also run 1 single operation. In the present case, when the grid consists of the shaft generator 10 and the rotating synchronous machine 17, the frequency retention is determined solely by means of the shaft generator.

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A control deviation in the comparison site 2J is fed as a magnetizing current to the magnetization winding of the shaft generator 10. At too low a frequency in the ship network voltage, the magnetization current becomes γ-10. through the regulator 27, 28, so that the shaft generator 10 provides a higher voltage on the rectifier 14. In the DC intermediate circuit voltage and current are increased. Since the inverter 15 can only supply power to the three-phase network, then the network is supplied with an increased power 15. This speeds up the synchronous machine 17 lying at the output of the inverter 15 and, where appropriate, other three-phase machines running on the grid so that the frequency deviation is offset. In this way, the machine 17 supplies a blind current to the mains and the inverter 20. The mains voltage is kept constant by the voltage regulation 20, 21 of the machine 17.

Usually, in the case of an inverter, the ignition angle will be enlarged by the occurrence of voltage drops at the inverter output so that the current does not increase.

This is e.g. the case of DC voltage high voltage transmission. In case of voltage reductions in the secondary grid the inverter's ignition angle is increased. In the power supply system according to the invention, however, such large voltage reductions, e.g. by short-circuiting that the ignition angle cannot be increased to such an extent that excessive currents are prevented. Furthermore, the danger of tilting the inverter is also particularly great, with both overcurrents and 35 large ignition angles. According to the invention, the inverter can be made up of single controllable electric valves, and the angle of ignition of the individual controllable electric valve in such a way depends on the voltage driving its commutation current that ignition 5 occurs when this voltage becomes less than one limit value formed by a selected reference voltage. Hereby, an improvement in the control ratio of a power supply system according to the invention is achieved with respect to the regulation speed and stability, especially at 10. not normal operating conditions, for example, when starting a local power supply generator, by connecting additional local power supply generators and by disruptions in the local grid. Controllable electric valves can also be arranged according to the invention in groups of parallel coupled electric valves to control large currents.

In the case of an inverter, the ignition angle should not be reduced to below 90 °, as it otherwise switches to rectifier operation and 20 is then shorted in the local power supply system.

In a power supply system according to the invention, Pette would short-circuit the local grid and the parallel power supply generator. The power supply system according to the invention for increasing the safety against false commutation of the inverter is arranged in such a way that the ignition angle of each controllable electric valve is reduced to a value of more than 90 °.

30 Means according to the invention for determining the ignition angle and their effect are shown in FIG. 3a, 3b and 3c.

FIG. 3a shows a conventional inverter constructed of single controllable electrical valves u- ^, u2, v ^ v2j w1 and w2 supplied from the uncontrolled rectifier to a direct current of voltage U and to the local grid. alternating current with phase voltages u, v and w. The sequence of voltages u, v and w forming a rotary current system is shown in FIG. 3 as a function of time t or angle out. In the case shown, at normal operation, the electric valves v- ^ and u2 are first switched on. In the usual cyclic order of the electric valves, then commute to Wp then u2 to v2 and finally w ^ to u ^. The angle of ignition α ^ -j. for the electric valve u ^ must be calculated from 10 the angle ω t, where the voltage u becomes positive and greater than the two voltages v and w. From this angle, it is possible to commute to u.

The voltage that can drive the commutation current at the commutation from w1 to u ^ is the differential voltage 15 u-w between the voltages u and w.

The progression of the differential voltage u-w depending on the ignition angle is shown in fig. 3c, where the voltage gauge differs from that of FIG. 3b. Further, there is shown the course of a sawtooth shaped reference voltage u, which according to the invention is a periodic function of time with the same frequency as the voltage u which drives the commutation current, and which has no positive value for ignition angles u. 25 and 90 °. The intersection of the curve of the voltage difference u-w and the curve of the reference voltage clock as a limit value determines the angle of ignition a ^. Couplings are known which, at values below the limit value, produce a voltage pulse for igniting an electric valve. Decreases the differential voltage, e.g. by overloading the local network, and has e.g. FIG.

3c with dashed lines, the electric valve will be switched on already at the smaller turning angle a2. Thereby, in the desired and simple manner 35, a reduction of the voltage-time area needed for commutation is prevented.

The reference voltage in the FIG. 3c is selected sawtooth shaped because such a voltage loss 5 can be obtained in known manner with simple means. However, in order to achieve an even stronger reduction of the ignition angle in the event of a disturbance, it may be advantageous that the reference voltage has a suitable other, e.g. sinusoidal or rectangular course.

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Between the synchronous machine 17 and the ship network 16, a mains coil 23 is coupled. It prevents the inverter from being switched, since the voltage when shorting the inverter output does not return to 15 0. The reason is that the short-circuit current of the synchronous machine passes through the coil and causes a voltage drop.

Furthermore, the overtones of the inverter 15 are eliminated by means of the mains coil 23 from the ship network 16. In the absence of load-dependent voltage fluctuations in the ship network 16, the voltage drop at the mains coil 23 is offset by the control device of the synchronous machine 17.

. When the shaft generator 10 is switched off, the mains coil 25 is short-circuited by means of a switch 24. This reduces the temporary drop in voltage when the consumers are switched on. When the shaft generator 10 is switched on, the synchronous machine 17 is disconnected from its auxiliary power machine 19. Thus, it does not have to run at idle 30.

In FIG. 2, there is shown a mains coil 26 with an outlet to which the synchronous machine 17 is connected. This measure is due to the fact that the throttle coil 26 acts as a transformer and, by a short circuit in the ship network 16, provides a higher voltage at the output of the inverter than would be the case with a direct connection of the synchronous machine 17 to the inverter 15. The synchronous machine 17 is also connected in parallel. with a capacitor 25 which causes the synchronous machine 17 to be produced in total less. The capacitor 25 partially takes over the functions of the synchronous machine 17.

In many cases, it requires the shaft generator system 10 to be operated without a sufficiently strong network available to connect the synchronous machine. The startup can then be effected in that the synchronous machine 17 is directly connected to the shaft generator 10 by a shunt of the rectifier 14 and the inverter 15 and starts asynchronously. During the asynchronous startup, the inverter 15 receives no ignition pulses. After the synchronous machine has achieved high revolutions and magnetization, the shunt ring is broken and the inverter 15 is supplied with ignition pulses. When the inverter 15 does not receive ignition pulses, it does not conduct current.

If the shaft generator is operated in parallel with the synchronous machine, which is still driven by the auxiliary power machine, this will only be possible when the frequency of the shaft generator is regulated so that the frequency of increasing power output decreases in the same way as that of the power machine. The control size for the shaft generator is then this output or the output of the parallel working synchro machine.

Claims (5)

145029 1. Power supply system for a constant-frequency AC network on ships with a widely varying speed driven synchronous generator as a shaft generator, after which a non-controlled rectifier and a grid-controlled inverter are provided and provided with at least one synchronous machine serving as blind power machine, and having a control device which sets the synchronizing current of the synchronous machine to obtain a constant mains voltage, characterized in that the shaft generator (10) has a control device (28) which sets the magnetization current of the shaft generator (10) to obtain a constant frequency and that the synchronous machine (17) in shaft generator operation is firmly connected to the alternating output (15) and the ship network (16). 15 Power supply system according to claim 1, characterized in that a mains coil (23s26) is connected between the synchronous machine (17) and the ship network (16). Power supply system according to claim 1, characterized in that the mains coil (26) has an outlet to which the synchronous machine (17) is connected. Power supply system according to claim 1, characterized in that a ship network generator (17) is used as a synchronous machine, which during the operation of the shaft generator (10) is disconnected from its auxiliary machine (19). Power supply system according to claim 1, characterized in that the synchronous machine (17) is switched on at start-up.