Lifting and / or construction machine, in particular crane, and method for operating same

Abstract

A lifting and / or construction machine, in particular a crane (1). The invention relates to a lifting and / or construction machine, in particular in the form of a crane (1), comprising a plurality of electric drives (6, 7, 8), which are supplied from at least one intermediate circuit (9) via current controllers such as frequency converters (10), a central power connection (11) for supplying the at least one intermediate circuit (9), and at least one energy storage device (12), which is connected to the at least one intermediate circuit (9) and is designed to provide additional energy in the event of a high power requirement of the drives (6, 7, 8). The invention further relates to a method for controlling such a lifting and / or construction machine, wherein the electric drives (6, 7, 8) are supplied from a central power connection (11) and, in the event of a high power requirement, additionally also from the energy storage device (12). According to the invention, control means are provided and designed to limit the power consumption via the central power connection (11) of the machine to a permissible limit value, to charge the energy storage device (12) from the central power connection (11) in operating phases in which the power requirement of the drives (6, 7, 8) is lower than the aforementioned limit value, and to discharge the energy storage device (12) in order to supply at least one of the drives (6, 7, 8) in operating phases in which the power requirement of the drives (6, 7, 8) is higher than the aforementioned limit value.

Description

[0001] Lifting and / or construction machinery, in particular cranes, and methods for operating them

[0002] The present invention relates to a lifting and / or construction machine, in particular in the form of a crane such as a tower crane, with a plurality of electrical consumers comprising drives that are fed from at least one intermediate circuit via current controllers such as frequency converters, a central power connection for feeding the at least one intermediate circuit, and at least one energy storage device that is connected to the at least one intermediate circuit and is provided for providing additional energy when the drive demand is high. The invention further relates to a method for controlling such a lifting and / or construction machine, in which the electrical drives are supplied from a central power connection and, when demand is high, additionally from the energy storage device.

[0003] Due to the high drive power required for the electric drives to generate positioning movements such as raising the load hook or luffing a boom, high-performance lifting and / or construction machinery such as large tower cranes require an equally high grid connection power on the construction site. Depending on the country or location of the construction site, this can be costly to provide or even impossible for the grid operator to implement. Such drive power is required not only for electric drives, whose movement is directly converted into positioning movements, possibly via a gear, but also for drives of pumps, for example, which provide hydraulic pressure for hydraulic drives, which then hydraulically generate the desired positioning movement, e.g., luffing a boom via one or more hydraulic cylinders.In addition to such drive power, there is regularly additional power consumption from other electrical consumers such as air conditioning systems.

[0004] Conversely, such large cranes and construction machines also generate high regenerative braking power, for example, when lowering heavy loads, which, however, has so far been difficult to utilize effectively. Due to the high fluctuation in power, such regenerative braking power cannot be fed into the public grid or is not permitted by the grid operator. Therefore, the excess energy generated by such large cranes or machines is regularly converted into unused heat using resistors, which reduces the crane's system efficiency.

[0005] In order to operate such large tower cranes or such high-performance construction machinery despite the aforementioned restrictions at the respective site, sufficiently large generators are usually used, which are primarily diesel-powered or driven by an internal combustion engine. Such generators provide the required power regardless of the grid voltage and stability. Although the tower cranes or construction machinery would in principle be fully electrified, CO2 emissions are released during operation. To avoid such CO2 emissions, the plan is to replace the diesel generators with battery- and / or hydrogen-based systems in order to operate locally emission-free on the construction site. However, due to the high peak power of the cranes or construction machinery, the generator still needs to be large.

[0006] Such current or future adaptation of the construction site infrastructure to the energy requirements of large machines such as tower cranes not only results in relatively high operating costs for the construction site, but also in costs for the purchase and operation of the power generators or the rental of such additional equipment.

[0007] It has already been proposed to cover a crane's energy demand peaks from an energy storage system. A short-term energy storage device in the form of a double-layer capacitor can be connected to the intermediate circuit via a DC / DC converter, from which the electric drives are powered. The short-term storage device is charged during regenerative braking of the travel and hoist drives and can be used as a kind of booster during short-term energy demand peaks.

[0008] For example, WO 2011 / 098542 A1 describes a crane with a diesel-electric drive, whose generator feeds an AC circuit to which a DC circuit is connected. A short-term energy storage device is connected to the AC circuit or to the DC circuit, with the AC circuit being connected to the DC circuit via a rectifier in such a way that an energy exchange between the AC circuit and the DC circuit is possible.

[0009] Furthermore, DE 10 2004 010 988 A1 describes a straddle carrier for transporting containers at container terminals. A short-term energy storage device in the form of a double-layer capacitor is connected to the DC link, from which the travel and lifting drives are powered via a current controller, in order to cover short-term energy demand peaks. In addition, another energy storage device in the form of a high-energy battery is connected to the DC link to cover medium power demand peaks that occur during travel or lifting operations lasting a few minutes.

[0010] AT 15 760 U1 further describes a large crawler crane whose power supply is entirely diesel-electric, using one or more generators, each of which feeds electrical energy into the power consumption system via a frequency converter. Several energy storage units are connected to the power consumption system to store excess energy generated during braking and provide it for short-term high power draws. The crane is designed to be switchable between different operating modes, allowing it to be operated either in a semi-hybrid or full-hybrid mode, or in a fully electric mode.

[0011] Even if these well-known cranes and hoists can overcome the limitations regarding the power supply at the respective site, they ultimately do not solve the underlying problem of the high connected load. Instead, they attempt to adapt the infrastructure at the site by using sufficiently large diesel generators. Thus, the problem remains that such additional diesel generators incur high costs for the purchase, operation, and possibly rental. At the same time, diesel generator operation still produces CCh emissions.

[0012] The present invention is therefore based on the object of creating an improved lifting and / or construction machine, particularly in the form of a large tower crane, and an improved method for operating the same, which avoids the disadvantages of the prior art and advantageously develops the latter. In particular, it is intended to enable locally emission-free operation even with limited grid connection power at the site of use, and to avoid the costs of additional equipment to increase the limited grid connection power.

[0013] The stated object is achieved by a lifting and / or construction machine according to claim 1 and a method according to claim 16. Preferred embodiments of the invention are the subject of the dependent claims.

[0014] It is therefore proposed to significantly reduce the connected load required at the central power connection of the machine by means of an energy storage device which is connected to at least one intermediate circuit from which the drives are fed via power points such as frequency converters and which is charged from the central power connection during operating phases of low demand and discharged during operating phases of high demand in order to limit the power consumption via the central power connection and not to overtax the grid connection load.According to the invention, control means are provided and designed to limit the power consumption via the central power connection of the machine to a permissible limit value, to charge the energy storage device from the central power connection in operating phases in which the power requirement of the drives is lower than the said limit value, and to discharge the energy storage device for supplying at least one of the drives in operating phases in which the power requirement of the drives is higher than the said limit value.

[0015] Unlike previous attempts at a solution, the existing infrastructure on a construction site is no longer improved and adapted to the high power requirements of a tower crane or other construction machine. Instead, the power consumption via the machine's central power connection is, so to speak, evened out and kept sufficiently low, despite higher power requirements, so as not to overload a grid connection. To this end, the control device takes advantage of the fact that, in addition to operating phases of high energy demand that cannot be met by the central power connection itself, the machine also has operating phases of low demand, during which more energy is drawn from the central power connection than the drives themselves require to charge the energy storage system from the grid or via the central power connection during these low-demand phases.

[0016] In a further development of the invention, the energy storage device comprises a power battery that can not only cover short-term energy demand peaks, such as a double-layer capacitor, but can also cover medium-term demand cycles of high demand in order to compensate for the difference between the limited connected power at the central power connection and the higher power consumption of the drives. In particular, a lithium-ion battery can be provided as the power battery, which is connected in the manner mentioned to the at least one intermediate circuit for supplying one or more drives. Several such power batteries can also be provided, for example in the form of a lithium-ion battery pack, which can be connected to form one or more battery banks.In particular, the energy storage device mentioned is designed to be able to provide the energy required for a complete lift of a tower crane, in particular to be able to provide the amount of energy exceeding the limited energy consumption of the central power connection in order to be able to carry out a full lift. Conventional technologies such as supercapacitors or flywheels as intermediate storage devices achieve the necessary performance, but have a low energy density, so that such conventional solutions are unsuitable or at least uneconomical for a complete lift of a large tower crane with maximum load. In contrast, lithium-ion batteries have recently developed to such an extent that, depending on the electrode material, not only high energy density but also very high power densities with high cycle counts can be achieved.By integrating such a power battery into the DC link of the machine to supply the drives, the necessary connected load, which is drawn via the central power connection, can be significantly reduced.

[0017] In particular, the time or operating phase between individual lifts can be used to charge the power battery, ensuring that power consumption from the grid remains consistently low. In addition, the machine's energy consumption can be reduced through recuperation, for example, through regenerative braking energy when lowering a load, since the potential energy released during load lowering can be partially recovered during normal operation.

[0018] The proposed concept is particularly efficient for tower cranes, as tower cranes, by design, do not require their peak power continuously. Return trips with empty hooks are necessary between energy-intensive hoists under full load. The sequential nature of high and low power requirements makes it sensible to integrate an energy storage unit into the intermediate circuit to supply the drives, covering the difference between the mains connected load and peak power. This significantly reduces the required connected load, enabling operation directly from the public grid on many construction sites or at many locations. The machine can nevertheless also be connected to other power sources, such as a generator, via the central power connection. This also offers advantages, as smaller generators are sufficient and can be operated and utilized more consistently.

[0019] Advantageously, the limit value used to limit the power consumption at the central power connection can be set variably in order to be able to limit the power consumption appropriately for different power grids and to use each connected power grid as fully as possible without overloading it.

[0020] The energy storage device can be connected to the machine's on-board network in various ways, or different system architectures can be provided for integrating the energy storage device.

[0021] One integration variant could involve connecting the energy storage unit to a DC link of the machine's main consumer, for example, the DC link for a crane's hoist drive. This allows for a simple topology and a significant reduction in the power consumption required via the central power connection, since the hoist drive accounts for a significant portion of a crane's maximum power consumption, and the limited grid connection power is sufficient for the other drives in many locations.

[0022] Alternatively or additionally, the energy storage unit or another energy storage unit can be connected to a common DC link for several drives. The energy storage unit can be connected to the link via a bidirectional DC / DC converter to adapt the fluctuating battery or storage voltage to the rectified mains voltage. Advantageously, one of the converters that are part of the common DC link can function as a rectifier, while the remaining converters only generate the rotating field of the connected drive.

[0023] Alternatively or additionally, a controllable rectifier can be provided between the central power connection of the machine and the at least one intermediate circuit from which the drives are supplied, in particular in the form of an active front-end converter, sometimes referred to as an AFE feed-in / feed-back unit. In particular, such a controllable rectifier can be designed to enable a bidirectional energy exchange between the central power connection of the machine and the aforementioned intermediate circuit. In particular, this allows the intermediate circuit voltage to be set independently of the supply voltage, enabling feedback into the public grid or feedback via the central power connection.

[0024] Advantageously, when using such an adjustable rectifier between the central power connection and the intermediate circuit, the energy storage device can be connected directly to the common intermediate circuit that supplies the machine's drives without a DC / DC controller.

[0025] The invention is explained in more detail below with reference to preferred embodiments and the accompanying drawings. In the drawings:

[0026] Fig. 1: a side view of a lifting and / or construction machine in the form of a fully electrically operated tower crane according to an advantageous embodiment of the invention, wherein the tower crane is designed as a top-slewing crane and has a power battery pack as an energy storage device as counterballast on the counterjib,

[0027] Fig. 2: a schematic representation of the drives of the crane from Fig. 1 , which are fed from an intermediate circuit via frequency converters, showing a central power connection and an energy storage device connected to the intermediate circuit via a bidirectional DC / DC converter,

[0028] Fig. 3: a schematic representation of the drives similar to Fig. 2, where the central power connection of the machine is connected to the intermediate circuit for supplying the drives via a controllable rectifier in the form of an active front-end unit and the energy storage is connected directly to the intermediate circuit without the interposition of a DC / DC converter, and

[0029] Fig. 4: a time diagram showing typical time courses of the power demand of the energy storage of the machine from the previous figures.

[0030] As shown in Fig. 1, the lifting or construction machine can be designed in the form of a crane 1 having a boom 3, from which a lifting device 14 can be raised and lowered, in particular a load hook that can be attached to a hoist rope or reeved therein. A trolley can be movably mounted on said boom 3 and moved by a trolley drive in order to adjust the hoisting point of the lifting device 14 or the outreach.

[0031] In particular, the crane 1 can be designed as a tower crane having an upright tower 2 on which the boom 3 is mounted, which can project approximately horizontally from the upper end section of the tower 2, but can also be luffed up and down if necessary. As Fig. 1 shows, the tower crane can be designed as a so-called top-slewing crane, in which the boom 3 sits on the tower 2 so that it can be rotated about an upright axis, although in principle it could also be designed as a bottom-slewing crane, in which the tower 2 can be rotated together with the boom 3 about the upright axis. The boom 3 can be balanced by a ballast 4 on a counter-jib 5, wherein the ballast 4 can be formed at least partially by an energy storage device 12, which can supply the crane's drives with energy.

[0032] As already explained above, the aforementioned energy storage device 12 can have a power battery for covering medium or longer demand peaks, in order to be able to supply the drives of the crane 1 from the energy storage device 12 for at least the entire hoist phase, as will be explained later. As shown in Fig. 1, a power battery pack can be provided in the form of stacked power batteries and mounted as ballast 4 on the counter-jib 5. In particular, the aforementioned power batteries can be lithium-ion batteries.

[0033] The drives of crane 1 include a hoist drive 6, by means of which the lifting device 14 can be raised and lowered, a trolley drive 7 for moving the trolley along the boom 3, and a slewing drive 8 for rotating the boom 3 around its upright axis. The aforementioned drives 6, 7, and 8 comprise electric motors, which can drive and move the respective units, if necessary with the interposition of a gearbox.

[0034] As Figures 2 and 3 show, the aforementioned drives 6, 7 and 8 can be connected to or fed from a common DC link 9, wherein current controllers comprising frequency converters 10 are provided for generating the current field applied to the drives 6, 7 and 8, cf. Fig. 2 and Fig. 3.

[0035] The intermediate circuit is supplied with power via a central power connection 11, whereby one of the frequency converters 10 can serve as a rectifier to convert the alternating current provided via the central power connection 11 into direct current. The frequency converters 10 of the remaining drives 6 and 8 then only generate the rotating field of the respective connected drive 6, 8.

[0036] As Fig. 2 shows, the energy storage device 12, which can comprise the aforementioned lithium-ion batteries, is connected to the aforementioned common intermediate circuit 9 of the drives 6, 7 and 8 via a DC / DC controller 15, which can advantageously be bidirectional, so that the energy storage device 12 can deliver energy to the intermediate circuit 9 and, conversely, can absorb energy from the intermediate circuit 9.

[0037] The system architecture mentioned has or forms a control device 16 which can limit the power consumption via the central power connection 11 to a permissible limit value which does not overload a power grid connected thereto and can charge the energy storage device 12 via the intermediate circuit 9 from the central power connection 11 in an operating phase in which the power requirement of the drives 6, 7 and 8 is lower than the said limit value and, on the other hand, can discharge the energy storage device 12 in operating phases and thereby feed the drives 6, 7 and 8 in which the power requirement of the drives 6, 7 and 8 exceeds the said limit value, ie the power requirement or the power consumption of the crane 1 is greater than the connected power provided by the connected grid.In particular, the energy storage device 12 can cover the difference between the limited power consumption via the central power connection 11 and the higher power requirements of the drives 6, 7, and 8. Power from the connected supply source or the connected network can still be fed into the intermediate circuit via the aforementioned central power connection 11 and made available to operate the drives. The excess power required is then supplied by the energy storage device 12.

[0038] As Fig. 3 shows, the energy storage device 12 can also be connected directly to the intermediate circuit 9 without the interposition of a DC / DC converter, in particular when the said intermediate circuit 9 is connected to the central power connection 11 via a controllable rectifier. The said controllable rectifier can in particular comprise an AFE, i.e. an active front-end unit, which enables energy to be exchanged between the central power connection 11 and the intermediate circuit 9 in both directions. As a result, energy can be fed back into the grid if there is an energy surplus in the intermediate circuit 9. Furthermore, grid operation can take place in parallel with the discharging of the energy storage device 12 and / or in parallel with the charging of the energy storage device 12, i.e. the energy storage device 12 can be charged without an additional charger. The said controllable rectifier can be used to set or control the power drawn from the grid via the central power connection 11.can be variably adjusted or regulated. In particular, this allows the intermediate circuit voltage to be selected independently of the supply voltage, enabling regeneration into the public grid.

[0039] Fig. 4 shows the typical charging and discharging cycles of the energy storage unit 12 during operation of the crane 1. During a heavy load lift, a relatively large amount of power is drawn from the energy storage unit 12 in order to be able to provide the high drive power despite limited power consumption via the central power connection 11. On the other hand, during empty runs, the operating phases of low demand are used to recharge the energy storage unit 12 from the central power connection 11.

Claims

Claims 1. A lifting and / or construction machine, in particular a crane, with a plurality of electrical consumers comprising drives (6, 7, 8) which can be fed from at least one intermediate circuit (9) via current controllers such as frequency converters (10), a central power connection (11) for feeding the intermediate circuit (9), and at least one energy storage device (12) which is connected to the at least one intermediate circuit (9) and is provided for providing additional energy for high demand of the consumers (6, 7, 8), characterized in that a control device (16) for limiting the power consumption via the central power connection (11) to a permissible limit value, for charging the energy storage device (12) from the central power connection (11) in operating phases in which the power demand of the drives (6, 7, 8) is lower than the said limit value, and for discharging the energy storage device (12) to feed at least one of the drives (6, 7, 8) in operating phases,where the power requirement is higher than the specified limit.

2. Lifting and / or construction machine according to the preceding claim, wherein the energy storage device (12) has at least one power battery for medium and / or longer power requirements.

3. Lifting and / or construction machine according to one of the preceding claims, wherein the energy storage device (12) is designed to supply the drives (6, 7, 8) with energy during an entire crane lift.

4. Lifting and / or construction machine according to one of the preceding claims, wherein the drives (6, 7, 8) have a lifting drive (6) which can be supplied at least partially from the said energy storage device (12), and the control device (16) is designed to carry out the charging of the energy storage device (12) in operating phases without power requirement of the lifting drive (6).

5. Lifting and / or construction machine according to one of the preceding claims, wherein the energy storage device (12) is connected to a DC intermediate circuit (11) of the main consumer of the lifting and / or construction machine, in particular to the DC intermediate circuit of a / the lifting drive (6) of the crane (1).

6. Lifting and / or construction machine according to one of the preceding claims, wherein the or a further energy storage device (12) is connected to a DC voltage intermediate circuit (9) common to several drives (6, 7, 8).

7. Lifting and / or construction machine according to the preceding claim, wherein the energy storage device (12) is connected to the common DC voltage intermediate circuit (9) via a DC / DC converter (15).

8. Lifting and / or construction machine according to one of the preceding claims, wherein a controllable rectifier is provided between the central power connection (11) and the intermediate circuit (9).

9. Lifting and / or construction machine according to the preceding claim, wherein an active front-end converter for bidirectional energy exchange between the central power connection (11) and the intermediate circuit (9) is provided between the central power connection (11) and the intermediate circuit (9).

10. Lifting and / or construction machine according to the preceding claim, wherein the energy storage device (12) is connected directly to the common intermediate circuit (9) without the interposition of a DC / DC converter (15).

11. Lifting and / or construction machine according to one of the preceding claims, wherein the control device (16) comprises adjustment means for variably setting said limit value for connection to different power grids.

12. Lifting and / or construction machine according to one of the preceding claims, wherein the drives comprise a lifting drive (6) for raising and lowering a lifting means (14) and a slewing drive (7) for rotating the boom (3) about an upright axis.

13. Lifting and / or construction machine according to the preceding claim, wherein the drives further comprise a trolley drive (8) for moving a trolley along the boom (3).

14. Lifting and / or construction machine according to one of the preceding claims, which is designed as a tower crane.

15. Lifting and / or construction machine according to the preceding claim, wherein the tower crane is designed as a top-slewing crane and the at least one energy storage device (12) is attached as ballast (4) to a counter-jib (5).

16. Method for controlling a lifting and / or construction machine, in particular in the form of a tower crane, in which the electrical consumers including drives (6, 7, 8) are supplied from a central power connection (11) and, in case of high demand, additionally from the energy storage device (12), characterized in that the power consumption via the central Power connection (11) of the machine is limited to a permissible limit value which is lower than the maximum power consumption of the drives, wherein the energy storage device (12) is charged from the central power connection (11) in operating phases in which the power requirement of the drives (6, 7, 8) is lower than the said limit value, and the energy storage device (12) for supplying at least one of the drives (6, 7, 8) is discharged in operating phases in which the power requirement of the drives is higher than the said limit value.

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