Stationary energy storage system

Abstract

The invention relates to a stationary energy storage system (1). Said energy storage system (1) comprises a battery rack (2) having a plurality of cells and comprises a load connection (10) to which a load (16) is connected at least in the intended use state. In addition, the energy storage system (1) has an AC / DC converter (14) connected between a mains connection (12) and the load connection (10) for providing operating energy at the load connection (10), and a DC / DC converter (6) connected between the battery rack (2) and the load connection (10) for providing operating energy at the load connection (10). In addition, the energy storage system (1) has switching means (8) by means of which the AC / DC converter (14) and the DC / DC converter (6) can be reversibly connected to the load connection (10). The switching means (8) are designed to connect the DC / DC converter (6) to the load connection (10) automatically and independently of an energy supply via the AC / DC converter side in an energy-free state on an AC / DC converter side.

Description

[0001] Description

[0002] Stationary energy storage system

[0003] The invention relates to a stationary energy storage system, which in particular comprises a battery rack.

[0004] Stationary energy storage systems, also known as ESS (energy storage systems), are known for storing energy. However, they differ from conventional battery systems, such as those used in private households for storing energy generated by photovoltaics. ESS systems typically include integrated operating units such as air conditioning systems, particularly cooling systems (e.g., HVAC) designed for extremely low operating temperatures in the range of -10 to -40 degrees Celsius, especially -20 to -30 degrees Celsius, battery management systems, and sometimes also fire extinguishing and / or fire suppression systems. Under normal operating conditions, these operating units are usually powered by energy supplied via a grid connection, i.e., from an external power grid (utility network). This allows for energy savings within the ESS system.

[0005] "Stationary" here does not mean completely immobile. Systems are also known that are housed in a container-like enclosure and can therefore be set up and used, for example, at construction sites. "Stationary" in this context means that a connection to the power grid is required, and the ESS (Energy Supply System) cannot be used completely arbitrarily or even in a mobile manner.

[0006] However, such energy storage systems (ESS) are also interesting if they can continue operating in the event of a power outage. For this purpose, ESS conventionally include an auxiliary or emergency power supply (UPS for "uninterruptible power supply"). This typically comprises a number of battery cells to bridge a short power outage. The longer the required bridging period, the more expensive such UPS systems become. Disadvantages of a UPS include the usually limited lifespan of the internal battery cells (especially since they must always be kept at a near-full charge level), as well as the required installation space and weight. The invention is based on the objective of improving a stationary energy storage system.

[0007] This problem is solved according to the invention by a stationary energy storage system with the features of claim 1. Advantageous and partly inventive embodiments and further developments of the invention are set out in the dependent claims and the following description.

[0008] The stationary energy storage system (ESS) comprises a battery rack, which in turn contains a plurality of (preferably secondary) cells (in particular, a large number of these subdivided into separate battery modules). Furthermore, the ESS has a load terminal to which, at least in its intended operating state, a load (consumer) is connected. The ESS also includes an AC / DC converter (rectifier) ​​connected between a grid connection and the load terminal to provide operating power at the load terminal, and a DC / DC converter (voltage-direction converter) connected between the battery rack and the load terminal to provide operating power at the load terminal. Finally, the ESS includes switching means by which the AC / DC converter and the DC / DC converter (in particular, each) can be reversibly connected to the load terminal.These switching devices are designed to automatically connect the DC / DC converter to the load connection in a power-free state on one AC / DC converter side (i.e., in particular at the mains connection or at least on the output side to the AC / DC converter) and independently of a power supply via the AC / DC converter side.

[0009] Preferably, the ESS does not include an uninterruptible power supply (UPS) module for the additional power supply of auxiliary modules that are connected to the load terminal as consumers, at least during the intended operation of the ESS. Such auxiliary modules include, for example, HVAC (heating, ventilation and air conditioning), a battery management system (BMS), a fire suppression system, and / or the like.

[0010] The use of the switching devices described above advantageously enables automatic switching from external power supply (provision of operating energy) to "internal" power supply, even in cases where the external power supply unexpectedly fails, for example, in the event of a power outage in a grid to which the ESS is connected via its mains connection. This allows for near-autonomous operation, particularly of the ESS's additional modules, which are otherwise operated with externally supplied power in conventional ESS systems. For example, cooling can be maintained via the HVAC system or a separate cooling unit.

[0011] In a suitable design, the AC / DC converter is configured to provide operating energy at a higher operating voltage than the DC / DC converter under normal operating conditions. For example, the "mains-side" operating voltage provided by the AC / DC converter is 27 V, while the "battery-side" operating voltage provided by the DC / DC converter is 24 or 25 V.

[0012] According to a preferred embodiment, the switching means are configured to conduct the operating energy from the AC / DC converter or from the DC / DC converter to the load, depending on a voltage difference resulting from the aforementioned difference between the operating voltage values.

[0013] In particular, the switching devices include (have) passive components designed such that, based on the higher operating voltage value when the AC / DC converter provides the operating energy, the injection of operating energy by the DC / DC converter to the load connection is blocked or at least reduced. Here and in the following, "passive component" is understood to mean, in particular, one that does not require and / or has no active (especially external) control for switching from one switching state to another.

[0014] Preferably, the passive components described above are formed by at least two diodes, in particular of identical construction. One diode is connected between the AC / DC converter and a connection point to the load terminal, and another is connected between the DC / DC converter and the connection point. In particular, each diode is arranged in the forward direction when viewed from the respective converter to the load terminal.

[0015] The use of diodes offers the significant advantage that no switching losses occur during the changeover between the "power sources" (from the perspective of the load connected to the terminal). Instead, the power supplied by the DC / DC converter is constantly available, its flow to the load terminal only being blocked by the associated diode. As soon as the power supply on the AC / DC converter side ceases, the power supply from the DC / DC converter side is immediately available. This allows for a particularly simple and continuous power supply (especially in terms of timing) at the load terminal. In an alternative design, the switching elements include a single-pole dual-throw relay (SPDT relay or "switch"). This relay has a first input and a second input, an output, and an actuator.Both inputs can be reversibly connected to the output by the actuator, so that only one input is ever connected to the output at any given time. In a normal state (especially one that is inherently stable, i.e., only changeable by the actuator), the first input is always connected to the output. The actuator is configured to connect the output to the second input in an "active state" when the AC / DC converter supplies power. Thus, in the active state, which is forced, particularly by the actuator, the output is connected to the second input; otherwise, when the actuator is deactivated, it is connected to the first input. "Intrinsically stable" therefore means that without the actuator's action, the SPDT switch assumes its normal state and thus connects the output to the first input.The load connection is connected to the output, the (battery-side) DC / DC converter to the first input, and the AC / DC converter to the second input. Therefore, for normal (mains) operation, the output is actively connected to the second input and automatically reverts to its normal state when the active circuit is deactivated, so that the (battery-side) DC / DC converter is (again) connected to the output and thus to the load connection.

[0016] According to a preferred further development, the actuator of the SPDT switch is connected to the AC / DC converter side for power supply (or activation). In particular, the actuator is connected in such a way that when the mains-side operating energy (i.e., that supplied by the AC / DC converter side) is present, the actuator automatically activates the SPDT switch to switch to the active state.

[0017] According to another alternative embodiment, the circuitry comprises a diode connected between the AC / DC converter and the load terminal, and a transistor connected between the DC / DC converter and the load terminal. Preferably, the transistor is a field-effect transistor (FET), in particular an N-channel FET. The advantage of the transistor lies in its comparatively short switching times compared to the SPDT switch (which is based primarily on mechanical switching operations), resulting from purely electrical switching processes. For example, the switching time of such a transistor is in the range of approximately one millisecond. The diode prevents the operating energy supplied by the DC / DC converter from being passed through to the AC / DC converter. A gate driver for the gate terminal of the transistor is preferably connected on the DC / DC converter side of the transistor.This advantageously provides the switching energy required for the transistor's operation independently of the operating energy available on the mains side, which is a particularly reliable approach.

[0018] According to a practical embodiment, a monitoring circuit for the operating energy supplied by the AC / DC converter is provided on the DC / DC converter side of the transistor. For example, this circuit is integrated into a control unit on the battery side of the transistor. The monitoring circuit is configured to initiate the switching of the transistor for the operating energy supplied by the DC / DC converter, particularly when the monitoring circuit detects the absence of this energy. Preferably, the monitoring circuit is linked to the aforementioned gate driver. Thus, the monitoring circuit checks whether the mains-side operating energy is present through the AC / DC converter and, as long as this is the case, prevents the transmission of the battery-side operating energy (i.e., supplied by the DC / DC converter) to the load connection.If the mains-side operating energy fails, the monitoring circuit therefore initiates the transmission of the battery-side operating energy.

[0019] As indicated or explained above, the designs using the SPDT switch and the transistor each exhibit switching delays during which no supply of operating power to the load terminal can be guaranteed. Therefore, according to an advantageous further development of these two designs, the ESS includes at least one capacitor (also referred to as "external") for the short-term power supply during a switching operation of the switching elements. This capacitor is connected between the switching elements (in particular the aforementioned connection point) and the load terminal. The switching delay or switching duration in the case of the SPDT switch is in the range of 40 to 80 milliseconds, particularly in the range of 50 milliseconds, while in the case of the transistor it is approximately one millisecond.

[0020] The embodiments of the invention described above advantageously enable the ESS to operate autonomously, at least independently of a UPS, even during a mains power outage. Furthermore, the use of two diodes (especially those connected in opposite directions) allows switching between external (mains-side) and battery-side power supplies advantageously without switching losses, making this a simple yet particularly advantageous design. The battery rack is preferably configured to provide a battery voltage of approximately 1000 to 1400 V, particularly 1008 to 1314 V. The DC / DC converter is therefore preferably configured to convert the battery voltage to the aforementioned operating voltage value of, for example, 24 V.

[0021] The conjunction “and / or” is to be understood here and in the following in particular as meaning that the features linked by means of this conjunction can be formed both jointly and as alternatives to each other.

[0022] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. The drawing shows, in schematic and simplified representations:

[0023] Fig. 1 shows a section of a generalized circuit diagram of a stationary energy storage system according to the invention,

[0024] Fig. 2 shows a first embodiment of the energy storage system in the view shown in Fig. 1, Fig. 3 shows a schematic diagram of the course of different operating voltage values ​​over time for the first embodiment.

[0025] Figs. 4 and 5, each in view according to Fig. 1, show a second and a third embodiment of the energy storage system, and

[0026] Fig. 6 in view according to Fig. 3 of a course of the operating voltage values ​​over time for the second and the third embodiment.

[0027] Corresponding parts and sizes are always marked with the same reference symbols in all figures.

[0028] Figure 1 schematically depicts a section of a stationary energy storage system (“ESS 1”). The ESS 1 comprises a battery rack 2 with a plurality of battery cells grouped together as (high-voltage) batteries 4, which are connected in series. Furthermore, the ESS 1 includes a DC / DC converter (direct-voltage converter; abbreviated: converter 6) which is connected to the battery rack 2 on its output side and is configured to convert a high-voltage value output by the battery rack 2, e.g., 1314 V, to a “battery-side” operating voltage value BBV, in this embodiment 24 V. On its output side, the converter 6 is connected to a load terminal 10 via switching elements 8, which are described in more detail below. The ESS 1 also has a mains connection 12, by means of which the ESS 1 is connected to a power supply network in its intended operating state.The ESS 1 also includes an AC / DC converter (rectifier 14) which is connected between the mains connection 12 and the switching devices 8 and is thus indirectly linked to the load connection 10 via the switching devices 8. The rectifier 14 is designed to rectify and convert an AC voltage received from the mains supply to a "mains-side" operating voltage value NBV. The two operating voltage values ​​BBV and NBV are reference values ​​for the operating energy supplied by the converter 6 and the rectifier 14, respectively. The ESS 1 also includes loads, such as an air conditioning unit (HVAC 16) shown here only as an example, which are connected to the load connection 10.

[0029] Other components that are usually present, e.g. fuses and / or common-mode filters, which are arranged, for example, between the rectifier 14 and the circuit elements 8 or between the battery rack 2 and the converter 6, are not shown here.

[0030] The switching means 8 serve to enable automatic switching of the battery-side operating energy to the load connection 10 and thus to the HVAC 16 during the operation of the ESS 1 in the event of the loss of the mains-side operating voltage value NBV, e.g. due to a power failure in the supply network.

[0031] For this purpose, the circuit elements 8, according to a first embodiment (see Fig. 2), have two diodes connected in opposite directions. A first battery-side diode 20 of these two diodes is connected between the load terminal 10 (here, at an exemplary connection point 22 between the first diode 20 and the load terminal 10). In this embodiment, the diode 20 is connected with its nominal (i.e., according to the circuit symbol) forward direction towards the load terminal 10. A second mains-side diode 24 is connected between the rectifier 14 and the load terminal 10, specifically the connection point 22. The second diode 24 is also connected with its nominal forward direction towards the load terminal 10.

[0032] Rectifier 14 is configured to rectify the AC voltage drawn from the mains supply to the operating voltage value NBV of 27 V. Converter 6 is configured to convert the high voltage of the battery rack 2 to the operating voltage value BBV of 24 V. Due to the arrangement of the two diodes 20 and 24, and the resulting voltage difference between the operating voltage values ​​NBV and BBV, the mains-side operating voltage value NBV, and thus the mains-side operating energy, is switched through to the load terminal, while the battery-side operating energy is blocked or at least significantly reduced at the first diode 20. If the mains voltage, and thus also the mains-side operating voltage value NBV, drops to zero, the battery-side operating voltage value BBV is automatically (automatically) and without delay passed through to the load terminal 10.

[0033] Figure 4 shows an alternative, second embodiment. The switching elements 8 here include a single-pole dual-throw relay (or switch; abbreviated: SPDT 30). This is connected between the converter 6, the rectifier 14, and the load terminal 10. Specifically, the SPDT 30 has a first input 32, a second input 34, and an output 36. The load terminal 10 is connected to the output 36, the converter 6 to the first input 32, and the rectifier 14 to the second input 34. The SPDT 30 is configured such that, under normal operating conditions without external influence, the first input 32 is always connected to the output 36 ("normally closed"), while the second input 34 is disconnected from the output 36 in this normal operating condition (normally open). The SPDT 30 has an actuator 38 which is configured to connect the second input 34 to the output 36 for an active state.In this way, rectifier 14 is connected to the load terminal 10 in the active state, so that the operating voltage value NBV is present at the load terminal 10. For this switching process, actuator 38 is supplied with power from the mains side, here connected to rectifier 14 as an example. If the operating voltage value NBV drops to zero – as shown in Fig. 6 – SPDT 30 returns to the normal state, so that the first input 32 is again connected to output 36. This allows the battery-side operating voltage value BBV to be passed through to the load terminal 10. However, the described switching process results in a switching delay (see Fig. 6).To bridge the duration of this switching delay, in the case of the SPDT 30 approximately 50 ms, the ESS in this embodiment has at least one capacitor 40, specifically two capacitors 40, which serve to supply power over the switching delay and are integrated between the circuit elements 8 and the load terminal 10.

[0034] Figure 5 shows a further alternative, third embodiment. The circuit elements 8 here include a mains-side connected diode 50, which is designed and connected analogously to the second diode 24 from the embodiment according to Figure 2, and a transistor, specifically an n-channel field-effect transistor (FET 52). The FET 52 is connected between the converter 6 and the connection point 22. A gate driver 54 is associated with the FET 52 and is connected on the battery side, i.e., independently of the mains-side operating energy. Furthermore, the ESS 1 includes a monitoring circuit 56, which is also arranged on the battery side. The monitoring circuit 56 is configured to monitor whether the mains-side operating voltage value NBV is not equal to zero, preferably greater than a minimum value. If this is the case, the monitoring circuit 56 causes the gate driver 54 to switch the FET 52 to non-conducting, e.g. by means of a control signal.If the monitoring circuit 56 detects that the operating voltage value NBV is zero or at least less than the minimum value, the monitoring circuit 56 causes the gate driver 54 to switch the FET 52 on, so that the battery-side operating voltage value BBV is passed on to the load terminal 10. Here, too, the capacitors 40 are provided to bridge a switching delay, which, however, is significantly shorter than in the second embodiment (on the order of one millisecond).

[0035] The FET 52 and the gate driver 54 are advantageously configured to switch the FET 52 conducting in a ground state, where the mains supply voltage is zero (or less than the minimum value), and to switch it non-conducting in an active state, similar to the second embodiment. [Question for Mr. Kim: Is this correct?]

[0036] The subject matter of the invention is not limited to the embodiments described above. Rather, further embodiments of the invention can be derived by a person skilled in the art from the foregoing description. In particular, the individual features of the invention and their various configurations described with reference to the different embodiments can also be combined with one another in other ways.

[0037] Reference symbol list

[0038] 1 ESS

[0039] 2 battery racks

[0040] 4 batteries

[0041] 6 converters

[0042] 8 switching devices

[0043] 10 Load connection

[0044] 12 Network connection

[0045] 14 rectifiers

[0046] 16 HVAC

[0047] 20 diode

[0048] 22 Connection point

[0049] 24 diode

[0050] 30 SPDT

[0051] 32 Entrance

[0052] 34 Entrance

[0053] 36 Exit

[0054] 38 Actuator

[0055] 40 Capacitor

[0056] 50 diode

[0057] 52 FET

[0058] 54 Gatedriver

[0059] 56 Monitoring circuit

[0060] BBV operating voltage value

[0061] NBV operating voltage value

Claims

Patent claims 1. Stationary energy storage system (1), comprising - a battery rack (2) with a plurality of cells, - a load connection (10) to which a load (16) is connected at least in the intended operating state, - an AC / DC converter (14) connected between a mains connection (12) and the load connection (10) to provide operating energy at the load connection (10), - a DC / DC converter (6) connected between the battery rack (2) and the load terminal (10) to provide operating energy at the load terminal (10), - Switching means (8) by means of which the AC / DC converter (14) and the DC / DC converter (6) can be reversibly connected to the load terminal (10), wherein the switching means (8) are configured to automatically connect the DC / DC converter (6) to the load terminal (10) independently of an energy supply via the AC / DC converter side in an energy-free state on one AC / DC converter side.

2. Stationary energy storage system (1) according to claim 1, wherein the AC / DC converter (14) is configured to provide operating energy with a higher operating voltage value than the DC / DC converter (6).

3. Stationary energy storage system (1) according to claim 2, wherein the switching means (8) comprise passive components (20, 24) which are designed such that, based on the larger operating voltage value when the operating energy is provided by the AC / DC converter (14), the injection of operating energy by the DC / DC converter (6) to the load connection (10) is blocked or at least reduced.

4. Stationary energy storage system (1) according to claim 3, wherein the passive components are formed by at least two, in particular identical, diodes (20, 24) which are each connected between the AC / DC converter (14) and a connection point (22) to the load connection (10) or between the DC / DC converter (6) and the connection point (22).

5. Stationary energy storage system (1) according to claim 1 , wherein the switching means (8) comprise a single pole dual throw relay (30) having a first input (32) and a second input (34), an output (36) and an actuator (38), wherein in a normal state the first input (32) is always connected to the output (36), wherein the actuator (38) is configured to connect the output (36) to the second input (14) in an active state when the operating energy is supplied by the AC / DC converter (14), wherein the load terminal (10) is connected to the output (36), the DC / DC converter (6) to the first input (32) and the AC / DC converter (14) to the second input (34).

6. Stationary energy storage system (1) according to claim 5, wherein the actuator (38) is connected to the AC / DC converter side for energy supply.

7. Stationary energy storage system (1) according to claim 1, wherein the switching means (8) comprise a diode (50) connected between the AC / DC converter (14) and the load terminal (10) and a transistor, in particular a field-effect transistor, preferably an N-channel FET (52), connected between the DC / DC converter (6) and the load terminal (10).

8. Stationary energy storage system (1) according to claim 7, wherein a gate driver (54) for the gate connection of the transistor (52) is connected on a DC / DC converter side of the transistor (52).

9. Stationary energy storage system (1) according to claim 7 or 8, wherein a monitoring circuit (56) for the operating energy provided by the AC / DC converter (14) is arranged on a DC / DC converter side of the transistor (52), wherein the monitoring circuit (56) is configured to initiate a switching of the transistor (52) for the operating energy provided by the DC / DC converter (6).

10. Stationary energy storage system (1) according to one of claims 5 to 9, wherein at least one capacitor (40) is connected between the circuit means (8) and the load connection (10) for short-term energy supply during a switching operation of the circuit means (8).

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