HK1118644B - Device for redundantly supplying power to at least one load - Google Patents

Description

Device for providing redundant power supply to at least one load

Technical Field

The invention relates to a device for providing a redundant power supply to at least one load, comprising: the system comprises a first converter connected to a first ac network via a first connection, a second converter connected to a second ac network via a second connection, and a dc voltage intermediate circuit connecting the first converter and the second converter on the dc voltage side.

Background

Such a device is known, for example, from DE 10340625 a 1. The device shown there has a first pulse current transformer and a second pulse current transformer, wherein the two pulse current transformers are connected to each other via a dc voltage intermediate circuit. Each pulse current transformer consists of a so-called 6-pulse bridge circuit with power semiconductor components that can be switched off. Such devices, also called short connections (Kurzkupplung), are used in the field of power distribution for the coupling of power distribution transport networks, which may have different frequencies, voltage levels, star point processing or phases.

Devices for redundant power supply are used, for example, in drilling ships or drilling platforms. For example, it is known that a drilling vessel or a drilling platform is not moored during drilling in deeper water, but is positioned dynamically by means of so-called thrusters. The thruster is designed to be driven with adjustable speed and azimuth so that the drilling vessel or platform can be positioned accurately without mooring. A power failure of more than 45 seconds can result in high costs, since in this case the drill rods necessary for drilling need to be mechanically decoupled and recoupled together after the drill ship or drilling platform has been relocated. Therefore, a reliable power supply is required for driving such a motor or drive. For this reason, drilling vessels and/or drilling platforms are often equipped with redundant power supply networks. In addition to the two power supply networks, there is usually a backup network to which it can be adjusted in the event of a fault. Each supply network is fed with electrical energy via a respective generator. For example, a mechanical switch is used to couple the supply network. However, a disadvantage of this coupling is that a faulty supply network adversely affects a fault-free supply network. This effect is undesirable. It is also known to connect two power supply systems via a changeover switch with a variable-speed drive instead of a switch. However, this access of the drive is time consuming and can lead to incorrect positioning during the transition phase of the transition.

Disclosure of Invention

The object of the invention is to provide a device of the type mentioned in the introduction, with which a redundant power supply can be provided.

The technical problem is solved as follows: the direct voltage intermediate circuit has at least one load connection for supplying a load.

According to the invention, the known device with the concept of a short connection is no longer used for coupling the second network. Instead, a redundant supply of power can be provided for a load which can be connected to the load connection by means of the provision of a load connection which is connected to the dc voltage intermediate circuit. Such a device is therefore particularly suitable for installation on a drilling vessel or platform: which is equipped with a drive with adjustable rotational speed and azimuth, such as a so-called thruster, for positioning a drilling vessel or a drilling platform in deeper water. For example, in normal operating situations, a load connected to the dc voltage intermediate circuit can be supplied from the second ac power supply system, the first ac power supply system taking over the supply of the load in the event of a breakdown of the ac voltage of the second ac power supply system. The converter according to the invention has suitable power semiconductor components, such as GTOs or IGBTs, which can be switched off. The power semiconductor components that can be switched off are synchronized, for example, in the kilohertz range by means of a pulse width modulation, so that a correspondingly short transition time can be used when switching from the second ac power supply system to the first ac power supply system. Such short transition times may ensure that erroneous positioning is avoided.

The regulation of the converter (also referred to as inverter in this case) is basically arbitrary within the scope of the invention.

However, according to a suitable development, the first converter has a first dc voltage regulation for regulating the dc voltage of the dc voltage intermediate circuit. The first inverter is used to build up a suitable direct voltage in the direct voltage intermediate circuit.

According to one suitable development, the second converter has a power regulation for regulating the power flow via the second converter, wherein the power regulation regulates the power to a negative rated dc power, the absolute value of which corresponds to the absolute value of the power consumed by all loads. According to this preferred embodiment, the supply of the load connected to the dc voltage intermediate circuit is carried out via the second ac power supply system, wherein the power regulation regulates the power to a negative rated dc power. Particularly in the case of using a motor as a load, the power consumed by it continuously changes over a period of time, and therefore it is appropriate to measure the power consumed on the load side with a measurement sensor. For example, the output signal of a calibrated voltage and current transformer, before being connected to the load terminals, can be used to measure the power dissipated by the load. The measured power consumed is used to determine an absolute value, which is equal to the negative rated dc power, by means of the regulation and is used as a setpoint value in the power regulation. Thereby, the load is supplied through said second supply network. The first converter is then used to maintain the direct voltage in the direct voltage intermediate circuit and at the same time to control the reactive power in the first alternating current network. In the event of a fault in the second ac power supply system, the first converter readjusts the dc voltage of the dc voltage intermediate circuit despite the lack of power supply, with little delay, so that despite a breakdown of the second ac power supply system no significant interruption of the power supply to the load results. In the embodiment of the invention, the collapse of the first ac voltage system results in a collapse of the dc voltage in the dc voltage intermediate circuit, so that a further drive of the load is excluded.

For this reason, in one development of the invention, the second converter is provided with a second voltage regulation for regulating the voltage in the direct voltage intermediate circuit. Since, according to this development, the two converters regulate the dc voltage in the dc voltage intermediate circuit, all loads can likewise be supplied by the two power grids. Thus, a failure of one network (and regardless of which network) has no adverse effect on the drive, since the supply of the load is respectively taken over by the intact ac network. According to the invention, the transition time from one ac network to another is in the range of a few milliseconds. By suitable selection of the control parameters, the converter interactions due to fluctuations in the dc voltage intermediate circuit can be prevented. The converter is thus suitably designed such that overshoots and mutual influences of the converter are prevented. Such adjustments are well known to the skilled person.

According to a suitable development in connection with this, the direct voltage intermediate circuit has a direct current breaker. Such a dc circuit breaker is implemented as a normal fuse, a bursting fuse (spraysicherung), or an electronic switch, for example. The dc voltage intermediate circuit is preferably composed of a plurality of dc branches, wherein each dc branch, which may also be referred to as a power block, is individually monitored and protected by a dc circuit breaker. The direct current circuit breaker can realize the optional circuit breaking of each direct current branch circuit under the fault condition without influencing the operation of other direct current branch circuits.

Preferably, each converter consists of power blocks connected in series. Such Power blocks are also known as Power Electronic Building blocks (Power Electronic Building blocks) according to the prior art and are known to the person skilled in the art and therefore need not be described in detail. These power blocks implement the modular structure of the converter and in this way regulate the converter to any voltage level. The converter and the dc voltage intermediate circuit are expediently designed as medium voltage and are used to drive the respective load, the medium voltage range being between 1kV and 52 kV.

According to a suitable development in this connection, each power block is connected to the dc voltage intermediate circuit via a circuit breaker unit. In this way, the power block can be replaced without disconnecting the other power blocks from the dc voltage intermediate circuit, thereby simplifying the maintenance and servicing of the device according to the invention.

Preferably, each load connection is connected to the dc voltage intermediate circuit via an inverter drive. The ac motor can be driven by using an inverter drive, in which the driving frequency of the load can be arbitrarily adjusted.

According to a preferred embodiment, the device of the invention comprises: a first parallel converter, which is connected to the first terminal and the first converter via a first terminal branch, and a second parallel converter, which is connected to the second terminal and the second converter via a second terminal branch, wherein the first parallel converter and the second parallel converter are connected to each other via a parallel direct voltage intermediate circuit. In other words, according to this development, two short connections can be connected in parallel or better antiparallel between the first ac power grid and the second ac power grid. In this case, the parallel short connections can be designed as main short connections for small voltages and therefore at low cost. The parallel short connection is for example a low-voltage short connection with a corresponding converter. The parallel short-connected parallel converters are used to supply the first converter with an ac voltage substantially in the event of an ac grid fault, so that the supply of power is possible even if the first ac grid is interrupted due to the fault. However, the parallel short-circuit connection is operated without load in normal operation and in the event of a second ac power grid fault. It is important that, in the event of a disruption or fault of the first ac power network, the faulty first ac power network is blocked with respect to the first parallel converter, i.e. with respect to the parallel short connection. The blocking is effected, for example, by a switch between the first ac power supply system and the first parallel converter and connected to the first converter. The first connection is realized, for example, by the switch. For normal operation, the parallel short connection suitably has a droop characteristic (Statik) which is smaller than the droop characteristic of the generator feeding the first ac power supply system. Otherwise, the parallel short connection operates in relation to the first ac power network, which is not blocked by the first converter during normal operation.

Preferably, the second parallel converter has a parallel dc voltage regulation for regulating the dc voltage of the parallel dc voltage intermediate circuit. According to a suitable development associated therewith, the first parallel converter has an ac voltage regulation for regulating the ac voltage in the first terminal branch. The regulation of the first and second parallel converters in parallel with the first and second converters is exactly the opposite of the first and second converters. This is naturally associated with the purpose of the parallel short connection, which provides a suitable ac voltage supply in the first connection branch when there is a fault in the blocked first ac power network.

Preferably, the first and/or second connector is a breaking unit. The disconnection unit is, for example, a switching device or a switch known per se, which can be connected to an ac power supply system. These switches may be mechanical switches or electronic switches.

Suitably, the first converter and/or the first parallel converter is connected to the first terminal branch via a first transformer, respectively, and the second converter and/or the second parallel converter is connected to the second terminal branch via a second transformer, respectively. In this way, an electrical decoupling is provided between the device and the ac power supply system during operation. Of course, it is also possible within the scope of the invention to connect a parallel load connection to the load to the parallel dc intermediate circuit.

A further advantage is achieved if the ac voltage drive is connected upstream of the load connection. Connecting the loads to the parallel load terminals is suitable, since the parallel short-circuit connections operate quasi-idly in normal operation. If the first parallel converter and the second parallel converter are designed for small voltages, the electrical energy is also supplied redundantly to the load designed for the respective voltage. The device according to the invention therefore considerably enlarges its application possibilities.

The invention also relates to a system having a first ac power supply system and a second ac power supply system, and an apparatus according to the preceding description.

Drawings

Other suitable structures, advantages and details of the present invention will become apparent from the following description of embodiments thereof, taken in conjunction with the accompanying drawings, in which like elements have like reference numerals, and wherein:

figure 1 shows a short connection for coupling two alternating current networks according to the prior art,

figure 2 shows a schematic view of an embodiment of the device according to the invention,

figure 3 shows a schematic view of another embodiment of the device according to the invention,

figure 4 shows a schematic view of another embodiment of the device according to the invention,

fig. 5 shows a schematic view of another embodiment of a device according to the invention, an

Fig. 6 shows a schematic view of another embodiment of the device according to the invention.

Detailed Description

Fig. 1 shows a short connection 1 as a device according to the prior art. The known short-circuit connection 1 has a first converter 2 and a second converter 3, which are connected to one another on the dc voltage side via a dc voltage intermediate circuit 4. The direct voltage intermediate circuit 4 comprises an energy storage, in this case a capacitor 5 for maintaining the direct voltage. The construction of the converters 2 and 3 is well known to the skilled person and therefore need not be described in detail here. The converter essentially consists of a 6-pulse bridge circuit with turn-off power semiconductor devices (in this case IGBTs), wherein a freewheeling diode connected in the reverse direction is connected in parallel with each turn-off power semiconductor device. The converter 2 is connected on the ac voltage side via a first terminal branch 6 to a first switch 7, which serves as a terminal for connection to a first ac voltage network 8. The transformer 9 serves to inductively couple the first converter 2 to the first ac power supply system 8 when the switch 7 is closed.

The second converter 3 is likewise connected via a transformer 9 and a second terminal branch 10 to a second switch 11 as a second terminal. By closing the switch 11, the second converter 3 can thus be inductively coupled to the second ac power supply system 12.

By suitable adjustment of the converters 2 and 3, any power transmission from the first ac power supply system 8 to the second ac power supply system 12 or from the second ac power supply system 12 to the first ac power supply system 8 can be achieved. In the schematic representation, the first and second current transformers 2, 3 have capacitors and inductors, which are only schematically illustrated, and the manner of interconnection and operation of which is likewise known to the person skilled in the art.

Fig. 2 schematically shows an embodiment of the device 13 according to the invention. The illustrated device 13 likewise has a first converter 2 and a second converter 3, which are connected to one another on the dc voltage side by means of a dc voltage intermediate circuit 4. The first converter 2 can be connected to a first ac voltage network 8 via a first connecting branch 6 and a first switch 7, while the second converter 3 can be coupled to a second ac voltage network 12 via a second connecting branch 10 and a second switch 11. The ac networks 8 and 12 each have their own power supply (here in the form of a generator) and a so-called thruster 14 or the like may be provided for supplying power for positioning the drilling vessel when it is performing drilling in deep waters. As already explained, the propeller is a variable speed and azimuth motor. Since only a short-term failure of the power supply to the propulsion device would lead to high costs, in addition to the second ac power network 12, which provides the power required by the propulsion device 14 during normal operation, a first ac power network 8 is provided, which can be switched on as required.

For this purpose, the dc voltage intermediate circuit 4 is connected to two load connections. The connection between the dc voltage intermediate circuit and the load terminals is effected by means of load terminal lines 15a and 15b, which are electrically connected to the positive connection line 4a of the dc voltage intermediate circuit 4 or to the negative connection line 4b of the dc voltage intermediate circuit 4. Two drive inverters 16 are connected upstream of the load terminals for converting the dc voltage into an ac voltage. The drive inverter 16 is also well known to those skilled in the art and therefore need not be described in detail herein. The drive inverter 16 produces alternating voltage and alternating current having a desired voltage amplitude, phase angle and frequency.

The first converter 2 is controlled by a dc voltage regulation, which sets a setpoint dc voltage, which is specified as a setpoint value for the regulation, in the dc voltage intermediate circuit 4. This dc voltage regulation is schematically indicated in fig. 2 by an arrow with Udc. The dc voltage regulation can also be used to regulate the reactive power Q of the first ac power supply system 8. This is indicated in fig. 2 by the arrow labeled Q.

The second converter 3 then has a power regulation device 17, which is connected to a schematically indicated measuring unit 18, wherein the measuring unit 18 comprises a voltage converter, which generates an output signal proportional to the dc current and/or the ac current and the dc voltage and/or the ac voltage, respectively, which signal is sampled by a sampling unit when a sampling value is obtained and converted into a digital dc current value and a digital dc voltage value by means of an analog/digital converter. The dc voltage regulation also has a parameterisable nominal dc power, which acts as a setpoint value for the dc voltage regulation, according to which the power semiconductor components (in the present case IGBTs) of the second converter 3 are activated in such a way that a power predetermined by the nominal dc power is transmitted by the second converter 3. Within the scope of the invention, a negative rated dc power is specified, which corresponds to the absolute value of the power consumed by the propulsion unit 14. In other words, a power flow is provided from said second ac grid 12 to the thruster 14 in the direction of the arrow designated by P due to the negative rated dc voltage. The first ac power network 8 is then used to maintain the dc voltage Udc in the dc voltage intermediate circuit 4.

In the event of a disruption of the second ac power supply system 12, the first ac power supply system 8 takes over the supply of power to the propulsion device 14 substantially without a time delay. In this case, the dc voltage Udc in the dc voltage intermediate circuit is maintained by the first converter 2 despite the interruption of the second ac power supply system 12. In this case, however, it is no longer possible to control the reactive power in the first ac power grid 8.

However, if a fault occurs in the first ac power supply system 8, the dc voltage in the dc voltage intermediate circuit 4 is no longer maintained. The power supply to the propeller 14 is interrupted.

Fig. 3 shows an exemplary embodiment in which the supply of power to the propulsion unit 14 is also ensured in the event of a disruption of the first ac power supply system 8. The parallel short connections 19 are to some extent antiparallel the short connections 13 in this illustrated embodiment of the invention. For this purpose, the first parallel converter 20 is inductively coupled to the first terminal branch 6 by means of a transformer 9. On the dc voltage side, the first parallel converter 20 and the second parallel converter 21 are connected via a parallel bipolar dc voltage intermediate circuit 22. The second converter 21 is connected to the second terminal branch 10 by means of the second transformer 9 and has a parallel dc voltage regulation for controlling a dc voltage of a parallel dc current intermediate circuit 22, which is indicated in fig. 3 only by the arrow labeled UDC.

The first parallel converter 20 has an ac voltage regulation with which the ac voltage which can be generated in the first terminal branch 6 can be controlled. In this way, the parallel short-circuit connection 19 generates an ac voltage in the connecting branch 6, so that the operation of the first converter 2 is maintained despite a disruption of the first ac power network 8. The first switch 7 is used to block the first ac voltage network 8 to the first connecting branch 6. In this way, even in the event of a fault in the first ac power network 8, as indicated by the cross-hatching in fig. 3, the motor or propeller 14 can be supplied with power. It is important, however, that in the event of a fault the switch 7 is opened, decoupling the first ac power supply system 8 from the first ac connection 6 and thus from the first converter 2. In addition, for a smooth normal operation, it is to be noted that the droop characteristic of the voltage regulation by the first parallel converter 20 is smaller than the droop characteristic of the generator, not shown in the figures, which feeds the first ac power supply system 8. Otherwise, the first parallel converter 20 is operated with respect to the first ac power network 8. Which is undesirable.

The parallel short connections 19 and short connections 13 can be constructed for any voltage range. In the embodiment shown in the figure, the short connection 13 is designed for the medium-voltage range, i.e. for voltages between 1kV and 52kV, while the parallel short connection 21 is designed for the low-voltage range. In this way, redundant drives can be implemented not only for larger loads or motors 14 but also for smaller loads or motors 24, 25. For the sake of completeness only, it is pointed out here that the parallel short connections 19 for the low-voltage arrangement are less expensive than the short connections 13 for the medium-voltage arrangement.

Fig. 4 shows a further exemplary embodiment of the device according to the invention, in which a parallel load connection, not shown in the drawing, is connected to the parallel circuit 22, before which a parallel drive inverter 23 is connected for driving an additional load 24. Furthermore, the direct voltage motor 25 is directly connected to the parallel direct voltage intermediate circuit 22.

Fig. 5 shows a further exemplary embodiment of a device according to the invention, which largely corresponds to the exemplary embodiment shown in fig. 4. In this case, however, the parallel dc voltage intermediate circuit 22 is connected on the dc voltage side via the dc voltage lines 26a and 26b to a backup converter 27, wherein the backup converter 27 is connected on the ac voltage side via a backup switch 28 to a backup supply network 29 which transmits the ac voltage. For the sake of clarity, a further backup converter is not shown in the figure, which is connected on the dc current side to the dc voltage intermediate circuit 4 and on the ac voltage side to a further backup current network or to the same backup supply network 29. The possibility of a failure of the supply to the load is still further reduced by this backup supply network 29 or by several backup supply networks. The first and second alternating voltage networks and the one or more backup power supply networks may have any number of phases independent of each other within the scope of the invention.

Fig. 6 shows a further exemplary embodiment which essentially corresponds to the exemplary embodiment described in fig. 2, but in which the second converter 3 likewise has a dc voltage regulation which is independent of the dc voltage regulation of the first converter 2. In this case, the regulation of the first converter 2 and the second converter 3 is carried out in the following manner: the converters 2 and 3 are prevented from interacting with each other, for example, as a result of fluctuations in the dc voltage intermediate circuit 4. The power converters 2 and 3 are, for example, of modular design and have power blocks, which are also referred to as power electronics bricks. Power electronic bricks are well known to the expert and therefore need not be described precisely here.

For safety reasons, the dc voltage intermediate circuit 4 in the exemplary embodiment shown has a disconnection unit 30, which in the event of a fault causes a current flow through the dc voltage intermediate circuit 4 to be interrupted. The breaking unit 30 is for example a fuse, an electric switch or the like.

Fig. 7 shows the embodiment according to fig. 6, but in which an additional antiparallel parallel short connection 19 is provided for supplying the small loads 24, 25, corresponding to fig. 4. The regulation of the converters 2, 3 of the short-circuit connection 13 is carried out as described in the exemplary embodiment of fig. 6. The parallel short-circuit connections 19 are regulated as described with reference to the exemplary embodiment of fig. 4, wherein a standby converter 27, which can be connected to a standby supply network 29, is also provided for the two short-circuit connections 13, 19.

Claims (5)

1. An apparatus for providing redundant power supply to at least one load (14), the apparatus comprising: a first converter (2) which is connected to a first AC network (8) via a first connection (7), a second converter (3) which is connected to a second AC system (12) via a second connection (11), and a direct voltage intermediate circuit (4) connecting the first converter (2) and the second converter (3) on the direct voltage side, characterized in that the DC voltage intermediate circuit (4) has at least one load connection for supplying a load (14), the first converter (2) and the second converter (3) each comprise a power semiconductor device which can be switched off, the second converter (3) has a power regulation for regulating the power flow via the second converter (3), wherein the power regulation regulates the power to a negative rated power, the absolute value of which corresponds to the absolute value of the power consumed by all loads.

2. The arrangement according to claim 1, characterized in that the first converter (2) has a first direct voltage regulation for regulating the direct voltage of the direct voltage intermediate circuit (4).

3. The arrangement according to claim 1 or 2, characterized in that the second converter (3) has a second voltage regulation for regulating the voltage in the direct voltage intermediate circuit (4).

4. A device according to claim 3, characterized by a direct current breaker (30) arranged in the direct voltage intermediate circuit (4).

5. A system having a first alternating current network (8) and a second alternating current network (12) and an apparatus according to any one of the preceding claims.