Method for operating an energy storage device in a submarine without active cooling

Abstract

The present invention relates to a method for operating a submarine 10, wherein the submarine 10 has an on-board power supply 20, wherein the on-board power supply 20 has a maximum power supply, wherein the submarine 10 has 4 to 400 energy storage devices 30, wherein each energy storage device 30 is electrically separably connected to the on-board power supply 20 via a respective DC-DC converter 40, wherein each energy storage device 30 has a maximum power supply, wherein each energy storage device 30 has a maximum storage capacity, wherein the submarine 10 has a cooling device 50 for the energy storage devices 30 and / or the DC-DC converters 40, wherein the method has a control mode and a secondary mode, wherein the secondary mode occurs when the cooling device 50 has failed or is switched off,wherein the method in secondary operation limits the power of the energy storage devices 30 to a maximum of 60% of the maximum storage power, wherein the method in secondary operation limits the maximum discharge of each energy storage device 30 to a maximum of 10% of the maximum storage capacity and electrically disconnects it from the vehicle electrical system 20 by means of the DC-DC converter 40 at the latest when this discharge is reached.

Description

[0001] The invention relates to a method for operating an energy storage device even if, for example, the cooling system has failed.

[0002] While lead-acid batteries were previously commonly used in submarines, which, due to the large unit cell size, delivered high currents but only low voltage, lead-acid batteries were now connected in series, so that usually only one or two energy storage devices made up of such series-connected lead-acid batteries were connected to the on-board electrical system. With the development of new batteries, particularly lithium-based ones, strings consisting of modules, with each module having several lithium batteries connected in series and in parallel, are now often connected individually and directly to the on-board electrical system via a DC-DC converter. DC-DC converters make it possible to separate the voltage and charge state, so that any combination of strings (energy storage devices) can be connected to the on-board electrical system. However, this requires reliable cooling, particularly of the DC-DC converters.

[0003] A battery module is known from DE 10 2019 216 606 A1.

[0004] DE 10 2019 216 608 A1 discloses a battery module with monitoring of the thermal runaway of individual cells.

[0005] From DE 10 2020 205 327 A1, a submarine with a situation-independent power supply for a string battery management system is known.

[0006] DE 10 2019 217 796 A1 describes a bridging of a battery management system in a submarine in the event of danger.

[0007] From DE 10 2020 203 469 A1 a method for operating a lithium accumulator on an on-board network designed for lead accumulators in a submarine is known.

[0008] A low-stray-field battery module is known from DE 10 2021 200 765 A1.

[0009] From DE 10 2021 202 537 A1 a method for operating a submarine with a fuel cell and an accumulator is known.

[0010] DE 10 2021 203 947 A1 describes the determination of the ageing state of an energy storage device on board a submarine.

[0011] From DE 10 2021 210 447 A1 a method for operating an on-board power system of a submarine at high loads is known.

[0012] DE 10 2022 208 979 A1 discloses a method for increasing the range of a submerged submarine.

[0013] DE 10 2022 205 773 A1 discloses a submarine with two different battery systems and a method for operating them.

[0014] A submarine with two converters on the traction motor is known from DE 20 2022 102 716 U1.

[0015] A battery module is known from EP 4 340 113 A1.

[0016] From DE 10 2022 132 635 A1 a submarine with an energy storage device arranged outside the pressure hull is known.

[0017] A battery storage system is known from DE 20 2016 100 559 U1.

[0018] However, if the cooling system fails, safe operation must still be ensured, at least in emergency mode, in order to bring the crew to the water surface as safely as possible.

[0019] The object of the invention is to provide an operation as a secondary operation (or emergency operation) that still provides the energy necessary for safe emergency operation.

[0020] This object is achieved by the method having the features specified in claim 1. Advantageous further developments emerge from the subclaims, the following description, and the drawing.

[0021] The method according to the invention serves to operate a submarine. The submarine has an on-board electrical system. The on-board electrical system serves to distribute the electrical energy and thus to supply the consumers. The on-board electrical system can preferably consist of two preferably independent sub-systems. The on-board electrical system has a maximum network power. The maximum network power is the maximum electrical power that can be permanently transmitted by the on-board electrical system and thus made permanently available to the consumers. The submarine has 4 to 400 energy storage devices. An energy storage device within the meaning of the invention is a unit that can be electrically connected directly to the on-board electrical system. In particular, energy storage devices within the meaning of the invention mean galvanic secondary cells or accumulators or capacitors, in particular galvanic secondary cells based on lead, nickel, sodium or lithium. This could also mean fuel cells.This does not include fuel-powered generators or other combustion engines, which do not store electrical energy but generate it by converting it from chemical energy. Thus, all energy storage devices can be electrically connected to or disconnected from the vehicle electrical system independently of one another. Any selected energy storage devices can therefore be selectively connected to the vehicle electrical system and the others disconnected accordingly. An energy storage device can preferably be a so-called string of 3 to 10, preferably 5 to 8, modules, each module having a plurality of secondary elements connected in parallel and / or in series, the actual accumulators. Each energy storage device is electrically disconnectably connected to the vehicle electrical system via a DC-DC converter.In this case, the separation can also be achieved by selecting a voltage on the energy storage device side that is lower than the voltage of the on-board network for a given current flow direction from the energy storage device to the on-board network, or by semiconductor converters that do not supply any current from the energy storage device to the on-board network but are nevertheless connected to a supply voltage. This means that no electrical power is supplied from the energy storage device to the on-board network. However, if the on-board network voltage drops, for example because the consumers require more power than is provided, the energy storage device feeds in at the reduced voltage level and is therefore connected to the on-board network when the on-board network voltage drops. This is referred to as hot standby. Such a hot standby is understood to be separated within the meaning of the invention because no current flows and therefore no thermal load occurs.This allows, on the one hand, the number of energy storage devices connected to the on-board electrical system to be controlled specifically according to the load requirements in the on-board electrical system. On the other hand, the on-board electrical system voltage can be selected or maintained independently of the voltage of the energy storage device, which depends on the charge state of the energy storage device. Each energy storage device has a maximum storage power. The maximum storage power is the highest electrical power that the energy storage device is designed to deliver continuously. Short-term peak powers that the energy storage device is capable of delivering, for example in the event of a short circuit, cannot be delivered continuously and can therefore briefly exceed the maximum storage power. Each energy storage device has a maximum storage capacity.The maximum storage capacity is the electrical capacity that is provided as the actually available electrical capacity between fully charged and fully discharged. The submarine has a cooling device for the energy storage devices and / or the DC-DC converters. For example, one cooling device can be provided jointly for the energy storage devices and the DC-DC converters. Alternatively, one cooling device can be provided for the energy storage devices and another cooling device for the DC-DC converters. However, one cooling device can also be provided for some of the energy storage devices and the DC-DC converters, for example in a first battery compartment, and another cooling device can be provided for the other part of the energy storage devices and the DC-DC converters, for example in a second battery compartment.In this case, the method according to the invention is preferably carried out only for the part, for example the battery compartment, in which the cooling device has failed.

[0022] To illustrate this purely by way of example, let us assume that the submarine has 200 energy storage devices. The on-board electrical system is designed for a maximum power output of 100 kW, and each energy storage device has a maximum storage capacity of 1 kW. This means that 100 energy storage devices could be connected to the on-board electrical system and 100 could be disconnected from the on-board electrical system, so that at full load, 100 energy storage devices with maximum storage capacity supply the on-board electrical system. Alternatively, all 200 energy storage devices could be connected to the on-board electrical system and then supply the on-board electrical system with half the maximum storage capacity (0.5 kW) at the maximum power output of 100 kW. If the on-board electrical system is only operated at a partial load, for example 50 kW, this opens up significantly more possibilities for providing the power required in the on-board electrical system.The advantage of this design is that the energy storage devices connected to the vehicle electrical system can be selectively and continuously reselected, for example, and in particular, taking into account the current state of charge of the energy storage devices. This control mode is known from the prior art.

[0023] The method comprises normal operation and secondary operation. Normal operation corresponds to the operation of such a submarine, known to those skilled in the art, during normal operation, with the cooling device functioning properly. Of course, the cooling device does not always have to run at full load during normal operation; rather, the cooling device can also be shut down or even switched off during normal operation, for example when only minimal energy is required in a very cold environment. It is important that the cooling device can be controlled without restriction during normal operation. Secondary operation occurs when the cooling device is not fully functional, for example if it has failed, partially failed, or is switched off. This also includes when its cooling performance is impaired, either unintentionally due to a defect or intentionally reduced, particularly to minimize noise.The secondary operation thus represents the inventive deviation from the standard operation according to the state of the art.

[0024] In secondary operation, the method limits the current power of the on-board electrical system to a predetermined maximum power value, for example and in particular less than 50% of the maximum grid power, preferably a maximum of 30% of the maximum grid power. In particular, the maximum power value is between 20% and 30% of the maximum grid power. This does limit the maximum power that a consumer can draw, for example and in particular a traction motor, and thus the maximum achievable speed for this. However, it does make it possible to generate power at all and thus, for example and in particular, propulsion, in order to be able to bring the submarine to the surface in a controlled manner. This limitation is undesirable but must be accepted for secondary operation.If the current power of the on-board electrical system exceeds the maximum power value, for example, higher than 30% of the maximum grid power, proper functioning of the secondary operation is no longer guaranteed. Since degradation concepts are usually present in submarines, the prioritization of consumers and their respective throttling are usually regulated, so that these procedures can be used to reduce the current power. In secondary operation, the method limits the power of the energy storage devices to a maximum storage value, for example and in particular a maximum of 60% of the maximum storage power. This specifically limits the current flowing through the DC-DC converter and thus limits the heating rate of the DC-DC converter, which is subject to the greatest thermal load in secondary operation.The process ensures, on the one hand, that the resulting grid load is applied to only selected energy storage devices. Non-selected energy storage devices are then de-energized during this time frame. In addition, the process ensures that the resulting grid load is cyclically commutated between all available energy storage devices. To this end, the process limits the maximum discharge of each energy storage device in secondary operation, for example, to a maximum of 10% of the maximum storage capacity. At the latest when this discharge is reached, the energy storage device is electrically disconnected from the vehicle electrical system by means of the DC-DC converter. Cyclical commutation limits the time during which the DC-DC converter is heated by the current flowing through it.The reduced power combined with cyclic commutation limits the total amount of heat introduced into the DC-DC converter, allowing continued operation even without active cooling. The de-energized phase allows the DC-DC converter to passively dissipate heat into the environment and thus cool down again.

[0025] In effect, this results in a rotation of the energy storage devices connected to the on-board power system, and thus also the DC-DC converter, during secondary operation. This allows for a lower electrical output in secondary operation, but still allows for reliable electrical output, for example, to enable a safe and controlled surfacing.

[0026] In a further embodiment of the invention, the method limits the power of the energy storage devices in secondary operation to a maximum of 60% of the maximum storage power for a maximum of 30 minutes. If the energy storage device is to remain connected to the vehicle electrical system for longer than 30 minutes, the method limits the power of the energy storage devices to a maximum of 20% of the maximum storage power for periods exceeding 30 minutes in secondary operation. The stronger the current flow through the DC-DC converter (the higher the power), the more the DC-DC converter heats up. At high power levels up to a maximum of 60%, therefore, only short-term operation of up to a maximum of 30 minutes is possible; after that, rotation via other energy storage devices must occur.Even though this involves a greater number of switching operations, the faster temperature rise and the subsequent significantly longer cooling phase result in good long-term temperature stability overall, without an excessively rapid temperature increase over multiple cycles. On the other hand, longer operation with lower power from the individual energy storage devices can also be advantageous, especially for very low power requirements in the on-board electrical system.

[0027] In a further embodiment of the invention, an energy storage device that has been electrically disconnected from the vehicle electrical system by means of the DC-DC converter is only electrically reconnected to the vehicle electrical system by means of the DC-DC converter after a waiting period. This is intended to allow sufficient cooling, particularly of the DC-DC converter. To ensure this, the waiting period is selected to be at least equal to the previous discharge time before disconnection from the vehicle electrical system. Preferably, the waiting period is selected to be at least three times as long as the previous discharge time before disconnection from the vehicle electrical system.

[0028] In a further embodiment of the invention, at the start of secondary operation, the method limits the maximum discharge of each energy storage device to a maximum partial discharge value in secondary operation. The maximum partial discharge value is, for example, a maximum of 20%, particularly preferably 10% of the maximum storage capacity. This preferably occurs when a fixed temperature level of all energy storage devices has been exceeded. At the latest when a discharge equal to the maximum partial discharge value is reached, the energy storage device is electrically disconnected from the vehicle electrical system by means of the DC-DC converter. This takes into account that, due to possible previous operation with higher flowing currents, the DC-DC converter is already at an elevated temperature level, which is, however, to be considered limited by ongoing cooling.Alternatively or additionally, this counteracts further heating of the energy storage devices after a defined temperature level is exceeded.

[0029] In a further embodiment of the invention, secondary operation occurs as soon as the cooling device fails or is switched off to reduce the acoustic signature. While the first case, the (unintentional) failure is unplanned and enables the necessary energy security in such an emergency, the second case serves to minimize the acoustic signature and thereby reduce the probability of detection and thus increase the probability of survival. In a case in which the acoustic signature is so low that it can be reduced by switching off a cooling device and thereby preventing the movement of the cooling fluid, the submarine is usually in a state with minimal energy consumption, especially at extremely low speed. Therefore, in such a state, also referred to as creep mode, secondary operation can be used to further reduce the acoustic signature.

[0030] In a further embodiment of the invention, the method limits the power of the energy storage devices in secondary operation to a maximum of 60% of the maximum storage power, depending on the ambient temperature inside the submarine. For example, the above-mentioned values ​​can be used for a temperature of 10 to 30 °C. At temperatures above 40 °C inside the submarine, the method can then, for example, limit the power of the energy storage devices to below the specified maximum power value, for example, a maximum of 30% of the maximum storage power, and increase the commutation frequency for the load of the energy storage devices. This takes into account the lower heat dissipation of the DC-DC converter when switched off, thus enabling a longer operating time in secondary operation without permanent damage to the submarine.

[0031] In a further embodiment of the invention, the predetermined maximum power value can be increased briefly in a first phase by more than 50% of all energy storage devices briefly storing energy at the maximum storage value, followed by a second phase in which only the energy storage devices not active in the first phase feed in, meaning correspondingly less energy is available, i.e. a significantly reduced maximum power value is available. Ultimately, the maximum power value is thus limited on average across the two phases together according to the invention. This enables a short-term increase in power, for example in order to be able to provide a power reserve, for example for the drive. After that, significantly less power is available to allow cooling.

[0032] The method according to the invention is explained in more detail below using an embodiment shown in the drawing. Fig. 1 submarine with inventive operable on-board power system

[0033] In Fig.1 shows a submarine 10. The submarine 10 has an on-board electrical system 20 to which the consumers (not shown) are connected, for example and in particular the traction motor (as one of the most powerful consumers). In order to feed electrical power into the on-board electrical system 20, the submarine 10 has eight energy storage devices 30 in the example shown; the actual number will typically be closer to 50 to 100. However, the internal structure of the energy storage devices 30 is irrelevant for the method according to the invention. The energy storage devices 30 are typically designed as strings consisting of 3 to 10 modules, wherein the modules have a larger number of secondary elements connected in parallel and in series, the actual accumulators.The energy storage devices 30 are connected to the on-board network 20 via DC-DC converters 40, so that they can be easily electrically connected to the on-board network 20 or electrically disconnected from the on-board network 20, individually, selectively and independently of the voltage of the energy storage devices 30 influenced by the state of charge. In order to protect the energy storage devices 30 and, above all, the DC-DC converters 40 from overheating during normal operation, the submarine 10 has a cooling device 50, which in the example shown is designed as a simple ring line through all the energy storage devices 30 and all the DC-DC converters 40 for the sake of simplicity.During normal operation, the ship's battery management system 60 can now connect or disconnect any energy storage device 30 to the on-board electrical system 20 by controlling the corresponding DC-DC converters 40 directly (or typically indirectly via a string battery management system (not shown). This ensures that the electrical power required by the on-board electrical system 20 is provided during normal operation. The energy storage devices 30 can thus be selected, for example, depending on the charge states of all energy storage devices 30. Cooling eliminates the time limit for discharging individual energy storage devices 30, and active cooling prevents overheating.

[0034] However, if the cooling device 50 fails or is to be shut down to minimize the acoustic signature, the submarine 10 can no longer be operated in normal mode, as this would lead to overheating, particularly of the DC-DC converter 40. Therefore, the submarine 10 is now operated in secondary mode according to the invention.

[0035] In the example shown, for example, the ship's battery management system 60 selects two of the eight energy storage devices 30 and connects them to the on-board network 20 via their DC-DC converters 40. The other six energy storage devices 30 are disconnected from the on-board network. The power of the two connected energy storage devices 30 is limited to, for example, 20% of the maximum storage power. Thus, the maximum grid power is limited to, for example, 10%, assuming that the sum of all maximum storage powers corresponds to twice the maximum grid power, i.e., half of all energy storage devices 30 are sufficient to provide the full maximum grid power to the on-board network 20, which would correspond to full redundancy. These two energy storage devices are discharged by, for example, 5% of their maximum storage capacity.These two energy storage devices 30 are then disconnected from the on-board electrical system, and two other energy storage devices 30 are connected to the on-board electrical system. This allows the DC-DC converters 40 of the first connected energy storage devices 30 to cool down. The energy storage devices 30 now connected to the on-board electrical system 20 in the second step are also limited, for example, to 20% of their maximum storage power. These and all energy storage devices 30 subsequently connected to the on-board electrical system 20 are discharged, for example, by 10% of their maximum storage capacity, since their DC-DC converters 40 were not previously loaded and thus had time to cool down. This allows the submarine to operate with a maximum network power of 10%, which, for example, does not allow for high cruising speeds, but at least enables safe surfacing. Reference symbol 10 submarines 20 On-board network 30 Energy storage device 40 DC-DC converters 50 Cooling device 60 Ship Battery Management System

Claims

[1] A method for operating a submarine (10), wherein the submarine (10) has an on-board power supply (20), wherein the on-board power supply (20) has a maximum power supply, wherein the submarine (10) has 4 to 400 energy storage devices (30), wherein each energy storage device (30) is electrically separably connected to the on-board power supply (20) via a respective DC-DC converter (40), wherein each energy storage device (30) has a maximum power supply, wherein each energy storage device (30) has a maximum storage capacity, wherein the submarine (10) has a cooling device (50) for the energy storage devices (30) and / or the DC-DC converters (40), wherein the method has a control mode and a secondary mode, wherein the secondary mode takes place when the cooling device (50) is not fully functional, for example, has failed, partially failed, or is switched off,wherein the method in secondary operation limits the power of the on-board network (20) to a predetermined maximum power value, for example, a maximum of 30% of the maximum power, wherein the method in secondary operation limits the power of the energy storage devices (30) to a maximum storage value, for example, a maximum of 60% of the maximum storage power, wherein the resulting network load is cyclically commutated between all available energy storage devices, wherein the method in secondary operation limits the maximum discharge of each energy storage device, wherein at the latest when this discharge is reached, the energy storage device is electrically disconnected from the on-board network by means of the DC-DC converter, wherein the cyclic commutation limits the time in which the DC-DC converter is heated by the current flowing through it. [2] Method according to claim 1, characterized bythat the method in secondary operation limits the power of the energy storage devices (30) to a maximum of 60% of the maximum storage power for a maximum of 30 minutes, wherein for times exceeding 30 minutes the method in secondary operation limits the power of the energy storage devices (30) to a maximum of 20% of the maximum storage power. [3] Method according to one of the preceding claims, characterized by that the method limits the maximum discharge of each energy storage device (30) in secondary operation to a maximum partial discharge value of a maximum of 10% of the maximum storage capacity and electrically disconnects it from the vehicle electrical system (20) by means of the DC-DC converter (40) at the latest when a discharge equal to the maximum partial discharge value is reached. [4] Method according to one of the preceding claims, characterized bythat an energy storage device (30) which has been electrically disconnected from the vehicle electrical system (20) by means of the DC-DC converter (40) is only electrically reconnected to the vehicle electrical system (20) by means of the DC-DC converter (40) after a waiting time, wherein the waiting time is selected to be at least equal to the preceding discharge time before disconnection from the vehicle electrical system (20). [5] Method according to one of the preceding claims, characterized by that for the start of secondary operation, the method in secondary operation limits the maximum discharge of each energy storage device (30) to a maximum of 20% of the maximum storage capacity and, at the latest when this discharge is reached, electrically disconnects it from the on-board network (20) by means of the DC-DC converter (40). [6] Method according to one of the preceding claims, characterized by that secondary operation takes place as soon as the cooling device (50) fails or is switched off to reduce the acoustic signature. [7] Method according to one of the preceding claims, characterized by that in secondary operation, depending on the ambient temperature inside the submarine (10), the power of the energy storage devices (30) is limited to a maximum of 60% of the maximum storage power.

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