Auxiliary Power Supply for Energy Storage System

Abstract

This disclosure relates to an energy storage system (ESS 100) that includes an energy storage circuit (122) having a string (111) of interconnected energy storage cells (110) configured to store electrical energy and supply power to an electrical grid using the stored electrical energy. The ESS further includes: an auxiliary module (112) configured to provide an auxiliary function to at least one of the plurality of energy storage cells (110); and an auxiliary power supply circuit (124) for supplying power to the auxiliary module (112) from a ground power source (126). The auxiliary power supply circuit (124) is configured to electrically isolate the energy storage circuit (122) from the ground power source (126) to prevent arcing between the ESS (100), which may be at a high voltage, and ground at the ground power source (126).

Description

Technical Field

[0001] The present disclosure generally relates to electrical energy storage systems. More specifically, the present disclosure relates to an auxiliary power supply arrangement for an electrical energy storage system. Background Art

[0002] An energy storage system (ESS) is a system for storing large amounts of electrical energy. The electrical energy may be generated by non-continuous power generation devices. Therefore, the ESS conveniently provides a way to store the generated electrical energy for later use as needed, even when the power generation device itself is offline. Thus, the ESS can form an important part of a renewable energy power distribution network including, for example, solar or wind power generation.

[0003] The ESS generally may include energy storage units (ESUs) arranged in a cabinet, where the term "cabinet" may be considered a collection of interconnected ESUs. Each ESU may include one or more energy storage cells, such as (super) capacitors, etc. Thus, arranging the ESUs into a cabinet can advantageously provide a modular ESS. Summary of the Invention

[0004] The present disclosure relates to an ESS that includes an energy storage circuit that includes a string of interconnected ESUs configured to store electrical energy and supply power to the power grid using the stored electrical energy.

[0005] According to one aspect of the present disclosure, the ESS includes an auxiliary module (AM) configured to provide an auxiliary function for at least one of a plurality of energy storage units. The auxiliary function may include performing (e.g., electrical and / or thermal) measurements in the ESU, monitoring the ESU, transmitting data between, for example, the ESU and a central control unit, operating a protection system in the ESU when needed, and / or performing diagnostics, etc.

[0006] To perform such an auxiliary function, the (plural) AM may require power. According to a comparative example that may not necessarily be included in the prior art, the power for the AM may be provided by the ESU itself, e.g., the same ESU for which the (plural) AM is configured to provide an auxiliary function.

[0007] However, according to this arrangement, in order to power the AM, the ESU must first be powered on. Therefore, there may be a period of time between when the ESU is powered on and when power is supplied from the ESU to the AM, during which the ESU is powered on while the AM cannot provide at least some of the auxiliary functions to the ESU. Thus, during this initial power-on time, the ESU may be at a particular risk of failure or damage, thereby losing the protection, monitoring, and similar auxiliary functions provided by the AM during this time.

[0008] Accordingly, in view of the above aspects of the present disclosure, there is further provided an auxiliary power supply (APS) circuit for supplying power from a ground power source to an auxiliary module. In some examples, the ground power source may obtain power from the same power grid to which the ESU of the ESS is configured to supply power, but not directly from the ESU itself. In other examples, the ground power source may obtain power from a generator (e.g., a diesel generator, etc.).

[0009] In any case, using a ground power source that does not directly draw power from the ESU can beneficially allow powering of the (one or more) AMs even when the ESU is not powered on. Thus, the ESU can be powered on and off (i.e., electrical energy is supplied to it and drawn from it), while still having the auxiliary functions provided to it. Accordingly, the ESS can beneficially maintain protection systems, monitoring systems, etc. throughout the operation, thereby enhancing the operational safety of the ESS.

[0010] According to a comparative example that may not necessarily be included in the prior art, the auxiliary power supply circuit may form a direct electrical connection between the ground power source and the (one or more) AMs. In such an example, the ESS may be limited in its ability to reach a high voltage and may thus be less suitable for grid support applications, as the AM may have a direct electrical connection to the (one or more) ESU for which it provides auxiliary functions.

[0011] Thus, if the ESU (relatively high in electrical potential) is electrically connected to the ground power source via the auxiliary power supply circuit that supplies power to the AM, there may be a risk of arcing from the ESU to ground (i.e., zero electrical potential) when the electrical energy stored in the ESU exceeds a threshold amount.

[0012] In an exemplary ESS, the ESUs are configured to supply power to the power grid (i.e., “grid-supporting ESS”) and are connected together on an energy storage circuit, the electrical potential of which may be in the tens to thousands of kilovolts (10s - 100s kV). At such an electrical potential, any component in the direct electrical connection path between the energy storage circuit and ground may be severely damaged by arcing. Accordingly, as part of the present disclosure, it has been recognized that grid-supporting ESSs may require special adaptation to supply power from a ground power source to the AMs in the ESS.

[0013] Accordingly, in view of the above aspects of the present disclosure, the auxiliary power supply circuit is configured to galvanically isolate the energy storage circuit from the ground power source. As used herein, “galvanic isolation” means an electrical connection without a direct conduction path. By galvanically isolating the energy storage circuit from the ground power source, the AMs can be safely powered by the ground power source even when the ESUs are powered on to a high electrical potential (i.e., collectively storing electrical energy suitable for supplying power to the power grid).

[0014] As part of the configuration of the APS circuit that isolates the energy storage circuit from the ground supply current, the APS can include at least one inductive coupling. Thus, the power for the AM can be beneficially obtained from the ground supply without forming a direct conduction path with the APS circuit, which may be electrically connected or poorly insulated from the energy storage circuit.

[0015] The inductive coupling can be a non-resonant inductive coupling (such as an isolation transformer) or a resonant inductive coupling. The resonant inductive coupling can include, for example, a transmitter configured to inject a power signal into the energy storage circuit; and a receiver configured to receive the power signal on the energy storage circuit and convert the received power signal into power for the auxiliary module.

[0016] The inductive coupling can take any suitable form, depending on the desired implementation, taking into account several potentially important factors such as the amount of potential to be isolated from the ground, the amount of modularity required, the maximum allowable cost, and / or space limitations.

[0017] For example, the inductive coupling (or other current isolation device) can be arranged as part of a two-stage isolation. That is, the auxiliary power supply circuit includes a primary unit, a primary circuit, a secondary unit, and a secondary circuit, where the primary circuit is isolated from the ground supply current through the primary unit, and the secondary circuit is connected to the auxiliary module and isolated from the primary circuit current through the secondary unit. The inductive coupling can be in either or both of the primary unit and the secondary unit.

[0018] As an improvement to this example, the auxiliary power supply circuit can include multiple primary circuits, each primary circuit being isolated from the ground supply current through a corresponding primary unit. Additionally or alternatively, the auxiliary power supply circuit can include multiple secondary circuits, each secondary circuit being isolated from the primary circuit current through a corresponding secondary unit.

[0019] In some examples, either the primary circuit or the secondary circuit can be connected to the energy storage circuit, and the other (i.e., the secondary circuit or the primary circuit, respectively) is connected to the AM(s).

[0020] As a further example, the resonant inductive coupling can inject a power signal at a frequency higher than the grid characteristic frequency (which can be, for example, 50 Hz or 60 Hz), such that the transmitter and receiver can send and receive more power while beneficially making the form factor smaller as well.

[0021] In the event of a fault, error, or other interruption (temporary or otherwise) in the grounded power supply, the APS circuit can be further configured to provide power from a backup power supply, such that the AM is redundantly powered and the risk of the AM being de-energized is advantageously reduced. Accordingly, the security of the ESS can be further enhanced. In some examples, the backup power supply can be a local power supply for the AM and can preferably include an energy storage module in a string of energy storage modules.

[0022] By providing a modular redundancy scheme, the resilience of the auxiliary power supply circuit can be further improved. For example, if multiple primary (and / or secondary) circuits are implemented, power can be supplied to a first auxiliary module via a first primary circuit and to a second auxiliary module adjacent to the first auxiliary module via a second primary circuit. The same solution can be readily envisioned for the secondary circuits.

[0023] Accordingly, the impact of any primary (or secondary) circuit failure can be mitigated because adjacent AMs may not all be powered on the same circuit. If combined with the above optional features and an ESU is employed as the backup power supply, the faulty circuit can readily draw power from an adjacent ESU serving as the backup power supply. Accordingly, a more resilient and secure ESS can be provided.

[0024] The solutions described herein can be applied to any power grid system that supplies power to and / or obtains power from an ESS. By enhancing the security and reliability of the ESS, the solutions currently described can thus enhance the reliability of any power grid system in which an ESS is installed. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Exemplary embodiments will now be described in more detail with reference to the following drawings, in which:

[0026] Figure 1 An energy storage system according to an embodiment is schematically illustrated;

[0027] Figure 2 An example configuration of an energy storage unit according to an embodiment is schematically illustrated;

[0028] Figure 3 An example configuration of an energy storage circuit and an auxiliary power supply circuit according to an embodiment is schematically illustrated;

[0029] Figure 4 Another example configuration of an energy storage circuit and an auxiliary power supply circuit with two-stage isolation according to an embodiment is schematically illustrated;

[0030] Figure 5Schematically shows another example configuration of an energy storage circuit and an auxiliary power supply circuit having a primary isolation stage and a secondary isolation stage according to an embodiment;

[0031] Figure 6 Schematically shows another example configuration of an energy storage circuit and an auxiliary power supply circuit having a primary circuit and a secondary circuit according to an embodiment; and

[0032] Figure 7 Schematically shows another example configuration of an energy storage circuit and an auxiliary power supply circuit that employs resonant inductive coupling and an injected power signal according to an embodiment. Detailed Description

[0033] The present disclosure will be elaborated by means of a plurality of illustrative examples below. It should be understood that these examples are provided for illustration and explanation only and are not intended to limit the scope of the present disclosure. Rather, the scope of the present disclosure will be defined by the appended claims. Additionally, although the examples may be presented in the form of separate embodiments, it should be recognized that the present disclosure also encompasses combinations of the embodiments described herein.

[0034] Figure 1 Schematically shows an energy storage system 100 according to an embodiment of the present disclosure. The energy storage system 100 (ESS100) may include a plurality of energy storage cabinets 102 (or simply referred to as "cabinets 102") connected in series to form a group 104 of energy storage cabinets 102, thereby providing a modular ESS100.

[0035] The group 104 of cabinets 102 may be connected between terminals 106a and 106b such that the group of cabinets 104 can be collectively charged and discharged via the terminals 106a, 106b. For example, the terminals 106a, 106b may be connected to a power grid and / or an electric energy generating device (not shown) such that the ESS100 can store electric energy (from the electric energy generating device and / or the power grid) and supply power to the power grid using the stored electric energy.

[0036] It should be understood that although only one series-connected group of cabinets 104 is shown, additional groups of cabinets 104 may also be provided between terminals 106a and 106b, and the additional groups of cabinets are connected in series or in parallel with the illustrated group of cabinets 104.

[0037] The ESS100 may further include a control unit 108 that is configured to provide various control functions for the ESS100, such as power management, monitoring, and similar functions. The control unit 108 may be local or remote with respect to the group 104 of cabinets 102 and may be connected via any suitable wired or wireless device (i.e., a power and / or data connection).

[0038] In an exemplary embodiment, the power generation device may include a non - continuous renewable electrical energy generation device that cannot generate electricity continuously, such as a wind turbine, a solar panel, etc. In such an embodiment, during the time when the power generation exceeds the grid demand (i.e., not immediately used), the ESS 100 can be advantageously charged by the electrical energy generation device (i.e., for example, electrical energy is provided via terminals 106a, 106b). Then, the electrical energy can be stored in the ESS 100 for future use.

[0039] Accordingly, when the grid demand exceeds the supply capacity of the electrical energy generation device, the electrical energy stored in the ESS 100 can be used to supplement the electrical energy supply. For example, the terminal 106 can be connected to a converter device (such as a STATCOM), which is configured to supply power to the grid. Thus, a more flexible grid can be provided by incorporating the ESS 100 according to the present disclosure.

[0040] Figure 2 such as shown in Figure 1 an example configuration of the cabinet 102 as shown. As shown, the cabinet 102 may include a plurality of energy storage units 110 (ESU 110) arranged in one or more strings 111, where the plurality of strings 111 of ESU 110 may be connected in parallel with each other, for example.

[0041] An example internal configuration of the ESU 110 is shown in an enlarged view, in which an auxiliary module 112 (AM 112) is shown, which is configured to provide auxiliary functions for the ESU 110. The ESU may further include a plurality of cells 114 (which may be (super) capacitors, batteries, etc.) and a protection and bypass system (which may include a discharge resistor 116 and a plurality of switches 118).

[0042] It should be understood that Figure 2 the protection and bypass system illustrated in is merely an example of a possible system that can be incorporated into the ESU 110 for controlling and / or protecting the power flow. Depending on the specific embodiment, sensors, monitors, fuses, and / or other control, protection, or monitoring devices may also be included.

[0043] As shown by the dashed line in the figure, the AM 112 can be configured to monitor and / or control one or more of the various internal components of the ESU 110. For example, the AM 112 can be communicatively coupled to each cell 114 and each switch 118 to identify errors (or faults or other interruptions (intentionally or otherwise interrupted)) of the cells 114 and take appropriate measures in response to the errors.

[0044] For example, AM 112 can monitor the health of the cell 114. If AM 112 detects a fault in the cell 114, then AM 112 can control one or more of the switches 118 to bypass the faulty cell(s) 114 (e.g., only the faulty cell or a group of cells that includes the faulty cell 114), and AM 112 can further connect the faulty cell(s) 114 to the discharge resistor 116, thereby discharging the faulty cell(s) 114, which makes the maintenance, removal, or replacement of the ESU 110 safer.

[0045] Therefore, it should be understood that the normal operation of AM 112 may be important for the safe and reliable operation of the ESS 100. Faults in the cells 114 in the ESU 110 and other such potential errors in the cabinet 102 are more likely to occur during the energization of the ESS 100 (e.g., during its initial charging). Therefore, it may be preferable to ensure that the auxiliary functions provided by AM 112 are operational before starting such energization.

[0046] Therefore, it may be preferable to continuously power AM 112, for example, via the AM power supply 120, or at least ensure that the power supplied to AM 112 is available before the ESU 110 is energized.

[0047] Therefore, according to the present disclosure, an auxiliary power supply for the auxiliary module 112 in the ESS 100 is provided, which reliably provides power from a power source independent of the ESS 100 itself. That is, power can be provided to AM 112 without relying on the ESU 110, because this may require energizing the ESU 110 first to enable the auxiliary functions (including monitoring and / or protection functions, such as the functions described above) to operate fully.

[0048] Therefore, according to the auxiliary power supply configuration described herein, it can be ensured that the ESS 100 operates more safely and reliably, and specific examples and variations of the auxiliary power supply configuration will be described below in conjunction with Figures 3 to 7 Describe specific examples and variations of the auxiliary power supply configuration.

[0049] Figure 3 An example circuit configuration 300 is schematically shown, which can be incorporated into an ESS (such as the ESS 100 described above with respect to Figure 1 and Figure 2 described ESS100).

[0050] The circuit configuration 300 may include a string (or subset of strings) of ESU 110s, each string having an AM 112 connected thereto for providing auxiliary functions (as described above). In some examples, the AM 112s are illustrated as components separate from the ESU 110s, but they may also be included as internal components of the ESU 110s. Additionally, although each ESU 110 is illustrated as having its own associated AM 112, some example embodiments may also configure one AM 112 to provide auxiliary functions to multiple ESU 110s.

[0051] The ESU 110s are connected to the energy storage circuit 122 via direct electrical connections. The AM 112s may be directly electrically connected to the ESU 110s and thus to the energy storage circuit 122, or the AM 112s may have poor insulation from the energy storage circuit 122.

[0052] Thus, if the ESU 110s are collectively implemented as part of a power grid system as described above, the electric potential caused by the large amount of electrical energy stored in the ESU 110s may be in the high voltage range (i.e., 10s kV to 100s kV).

[0053] The AMs are powered via an auxiliary power supply circuit 124, which may be connected (e.g., via a direct electrical connection) to the energy storage circuit 122. The auxiliary power supply circuit 124 may be configured to supply power to the AM 112s from a ground power supply 126.

[0054] By obtaining power from the ground power supply 126, the AM 112s can beneficially remain powered regardless of whether the ESU 110s are powered on. Thus, the AM 112s may be operable to provide auxiliary functions such as protection and monitoring even before and during the initial power-on of the ESU 110s. This can provide a safer and more reliable ESS 100.

[0055] Since the ESU 110s have such a relatively high electric potential (relative to ground, i.e., zero electric potential), there is a risk of arcing between the high electric potential portion of the energy storage circuit 122 (and the auxiliary power supply circuit 124 if it is connected to or has poor insulation from the energy storage circuit 122) and the ground power supply 126.

[0056] As shown, the auxiliary power supply circuit 124 may thus be configured to current isolate the energy storage circuit 124 from the ground power supply 126. As used herein, "current isolating" a circuit from ground is intended to mean that no direct electrical connection is formed between the circuit and ground.

[0057] In the illustrated example, current isolation can be provided by coupling 128, which can be an inductive coupling such as resonant or non-resonant coupling. It should be understood that current isolation can also be provided by capacitive coupling, reactance coupling, optical coupling, or other such couplings that provide current isolation. However, as part of the present disclosure, it should be recognized that coupling 128 can preferably be an inductive coupling, which provides a beneficial balance between cost and size. For example, coupling 128 can be an isolation transformer.

[0058] In Figure 3 the illustrated example, each AM 112 is directly electrically connected to a corresponding auxiliary power supply circuit 124, and each auxiliary power supply circuit 124 is current isolated from the ground power supply 126 by a corresponding coupling 128. In such an example, it should be understood that each coupling 128 may be required to isolate the total collective electrical potential of the energy storage circuit 122 (to which all ESU 110 are connected) from ground (i.e., the ground power supply 126).

[0059] That is, each coupling 128 may be required to reliably isolate a potential of 10s kV to 100s kV from ground, i.e., prevent arcing across coupling 128. The size and cost of coupling 128 can be proportional to the amount of electrical potential that needs to be isolated from ground. Therefore, Figure 3 the example configuration 300 shown in Figures 4 to 7 may be relatively more expensive and less space-efficient than the configuration shown in

[0060] Figure 4 An alternative circuit configuration 400 including two-stage isolation is shown. More specifically, as Figure 4 illustrated, instead of each coupling 128 being configured to withstand the collective electrical potential of the energy storage circuit 122, only one such configured coupling 128 may be required to do so.

[0061] According to the illustrated configuration 400, the auxiliary power supply circuit 124 includes a primary circuit 124a and a plurality of secondary circuits 124b, and each secondary circuit 124b supplies power from the primary circuit 124a to a corresponding AM 112. The secondary circuit 124b is current isolated from the primary circuit 124a via a secondary coupling 128b (which may also be referred to as a secondary unit 128b), and the primary circuit 124 is current isolated from the ground power supply 126 via a primary coupling 128a (which may also be referred to as a primary unit 128a).

[0062] The respective primary couplings 128a and secondary couplings 128b can be similar to the coupling 128 described with respect to Figure 3 i.e., the coupling 128 (collectively referring to the primary coupling 128a and the secondary coupling 128b) can include, for example, resonant or non-resonant inductive coupling.

[0063] However, only the primary coupling 128a can be configured to isolate the collective potential of the ESU 110 on the energy storage circuit 122 from the ground potential. That is, the primary coupling 128a can supply power to the primary circuit 124a in a current-isolated manner and can then distribute the power among the plurality of secondary circuits 124b.

[0064] Accordingly, the secondary coupling 124b may not need to be configured for the entire voltage between the highest voltage of the energy storage circuit 122 and the ground, but only for the voltage between the highest voltage of a subset of the ESU 110s and the ground. In this example, the voltage potential isolated from the ground by the secondary coupling 128b can be the voltage potential corresponding to a single ESU 110 because each AM 112 of each ESU 110 is provided with its own corresponding secondary circuit 124b that is connected to the primary circuit 124a via its own secondary coupling 128b.

[0065] Accordingly, it should be understood that the cost and space of the secondary coupling 128b can be saved while only one more expensive and larger primary coupling 128a can be used.

[0066] In some example variations, multiple primary circuits 124a can be provided, each isolated from the ground power supply 126 by a respective primary coupling 128a, and then each primary circuit 124a can be coupled to one or more secondary circuits 124b via a respective secondary coupling 128b. The secondary circuits 124b can supply power to one or more AMs. In fact, the number of secondary couplings 128b and the manner in which they are connected to the ESU 110 (grid) may be constrained by cost requirements, space limitations, and / or the maximum voltage isolation of the (multiple) secondary circuits 124b.

[0067] The circuit configuration 400 can further include additional components such as resistors 130 and / or fuses 132 in any part thereof as needed, for example, to serve as protection measures.

[0068] In addition, in some examples, a bridging connection 133 can be provided across the secondary coupling 128b to strengthen the potential of the primary circuit 124a, thereby ensuring that most of the current isolation is provided by the primary coupling 128a. This can allow the secondary coupling 128b to be configured to provide current isolation only between one or more adjacent ESU 110s.

[0069] Figure 5 Illustrated is Figure 4 a variation of the configuration 400. Figure 5 The circuit configuration 500 shown in Figure 4 employs an alternative connection of the secondary circuits 124b, different from the connection shown in

[0070] That is, the secondary circuit 124b in the configuration 400 can distribute power such that each secondary coupling 128b can be configured to have the same rated power, but may be subject to different voltage stresses. In contrast, Figure 5 the secondary circuit 124b in the configuration 500 shown in can distribute power such that each secondary coupling 128b can be configured to have different rated powers, but may be subject to the same voltage stress.

[0071] Nevertheless, Figure 5 the configuration 500 illustrated in can share the beneficial characteristics discussed with respect to Figure 4 because fewer primary couplings 128a (which may be more expensive or larger) can be used due to the use of two-stage isolation (i.e., the use of the (one or more) primary circuits 124a and the (one or more) secondary circuits 124b discussed above). In some examples, depending on the particular implementation, combinations of the different connections described above can be used.

[0072] Figure 6 An alternative circuit configuration 600 is shown that includes a primary circuit 124a and multiple secondary circuits 128b that share the same secondary coupling 128b. According to the illustrated example, the primary coupling 128a and / or the secondary coupling 128b can include a resonant inductive coupling, which can also be referred to as a "wireless power transfer device".

[0073] The primary circuit 124a (the circuit on the ground side) and / or the secondary circuit 124b can include an additional coupling circuit 134 for starting or enhancing the wireless power transfer device. For example, the coupling circuit can include means for changing the signal frequency such that the characteristic frequency of the ground power supply 126 (e.g., the power grid) can be increased. For example, the additional coupling circuit 134 can include a power factor controller (PFC), a rectifier, and / or an inverter.

[0074] Thus, the size of the primary coupling 128a and / or the secondary coupling 128b can be reduced because a smaller resonant inductive coupling can be used to transfer the same amount of power at a higher frequency. By using the capacitor 136, resonance can be introduced into the circuit, thereby further enabling or enhancing the wireless power transfer device. According to such a coupling system, power can be inductively transferred from the transmitting antenna to the receiving antenna via impedance matching.

[0075] Figure 7FIG. illustrates another alternative configuration 700 of the auxiliary power supply circuit 124, where a voltage (e.g., a high-frequency voltage signal, which can also be referred to as a power signal) is superimposed on the operating voltage of the ESU 110 of the energy storage circuit 122, i.e., the voltage associated with the current flow for charging and discharging the ESU 110 during normal operation of the ESS100.

[0076] Thus, the primary circuit 124a including the capacitor 136 can be connected to the energy storage circuit 122 and is galvanically isolated from the ground power supply 126 (e.g., the AC grid) via the primary coupling 128a. The primary coupling 128a can include a transmitter configured to inject a power signal into the energy storage circuit 128a.

[0077] The primary coupling 128a can be used as a high-frequency external input, e.g., it can be connected to the link between two ESU 110s. Thus, the connection point of this external input may be the location where the voltage of the ESS100 with respect to the ground is the lowest. In a monopole system, this may occur at one end of the ESS100, while in a bipolar system, this point may be the midpoint of the ESS100. Each primary coupling 128a (e.g., the high-frequency link transfer module) can be equipped with a transformer and a capacitor 136.

[0078] Then, the AM 112 can be connected to the secondary circuit 124b, and the secondary circuit is galvanically isolated from the energy storage circuit 122 via the secondary coupling 128b (and thus galvanically isolated from the primary circuit 124a connected to the energy storage circuit). The secondary coupling can include a receiver for receiving the power signal and converting the power signal into electricity for the AM 112.

[0079] It should be understood that if the (one or more) AM 112 includes components that require DC power, the (one or more) secondary couplings 128b can be connected to, for example, an AC-DC converter, which can then feed DC power to the secondary circuit 124b.

[0080] The frequency of the power signal can be higher than the characteristic frequency of the AC grid used as the ground power supply 126. Thus, the primary coupling 128a and / or the secondary coupling 128b can be made smaller and cheaper than would be required if the characteristic frequency of the AC grid were used as the frequency of the power signal.

[0081] It should be understood that depending on the intended implementation, all the concepts disclosed above as alternative configurations can be combined in any compatible manner.

[0082] Additionally, although schematically illustrated as separate, the primary circuit 124a and the secondary circuit 124b and their respective couplings 128 may be placed in one unit or in separate units. In some examples, depending on the dielectric strength of the insulation, the secondary circuit 124b and / or the secondary coupling 128b may remain floating. This may enable both the primary coupling 128a and the secondary coupling 128b to contribute to providing voltage isolation between the ESU 110 and the grounded power supply 126.

[0083] A common shield may also be provided on the secondary circuit 124b and / or the secondary coupling 128b and connected to a point in the ESU 110 section. In this configuration, the secondary coupling 128b may only need to provide voltage isolation between this connection point and the ESU 110 that is furthest from the connection point in the vertical direction.

[0084] Although some embodiments and their exemplary modifications may have been presented independently herein, it should be understood that these embodiments and examples may be combined in any form in order to realize collective and / or synergistic advantages therefrom.

[0085] It should be understood that any combination of the above exemplary embodiments may advantageously allow powering of the auxiliary module 112 of the ESU 110, which may have (or "be at") a very high electrical potential. According to the present disclosure, this advantage may be achieved by transmitting power from the grounded power supply 126 via some current isolation means (e.g., the coupling 128).

[0086] In any case, it should be understood that the foregoing description merely lists a number of illustrative examples that fall within the scope of the present disclosure and does not necessarily delimit its full breadth. To avoid doubt, the scope of the present disclosure will be defined by the appended claims.

Claims

1. An energy storage system (ESS) (100), comprising: an energy storage circuit (122) including a string (111) of interconnected energy storage units (110) configured to store electrical energy and supply electrical power to an electrical grid using the stored electrical energy; an auxiliary module (112) configured to provide an auxiliary function to at least one of the plurality of energy storage units (110); and an auxiliary power supply circuit (124) for supplying power from a ground power source (126) to the auxiliary module (112); wherein the auxiliary power supply circuit (124) is configured to electrically isolate the energy storage circuit (122) from the ground power source (126), wherein: the auxiliary power supply circuit includes a primary unit, a primary circuit, a secondary unit, and a secondary circuit; the primary circuit is connected to the energy storage circuit and is electrically isolated from the ground power source through the primary unit; and the secondary circuit is connected to the auxiliary module and is electrically isolated from the primary circuit through the secondary unit, and wherein: the primary unit includes a transmitter configured to inject a power signal into the energy storage circuit; and the secondary unit includes a receiver configured to receive the power signal from the energy storage circuit and convert the received power signal into electrical power for the auxiliary module.

2. The ESS according to claim 1, wherein: the auxiliary power supply circuit includes at least one inductive coupling.

3. The ESS according to claim 2, wherein: the at least one inductive coupling includes a resonant inductive coupling.

4. The ESS according to claim 1, wherein: the auxiliary power supply circuit includes a plurality of primary circuits, each primary circuit being electrically isolated from the ground power source through a respective primary unit.

5. The ESS according to claim 4, wherein: the auxiliary power supply circuit includes a plurality of secondary circuits, each secondary circuit being electrically isolated from a primary circuit through a respective secondary unit.

6. The ESS according to claim 4 or claim 5, wherein: power is supplied to a first auxiliary module via a first primary circuit; and power is supplied to a second auxiliary module adjacent to the first auxiliary module via a second primary circuit.

7. The ESS according to any one of claims 4 to 6, wherein: the primary unit and / or the secondary unit includes a resonant inductive coupling.

8. The ESS according to claim 1, wherein: the frequency of the power signal is higher than the characteristic frequency of the electrical grid.

9. The ESS according to any of the preceding claims, wherein: the auxiliary power supply circuit is further configured to supply power from a backup power source.

10. The ESS according to claim 9, wherein: the backup power source includes an energy storage module from the string of energy storage modules.

11. A power grid system comprising the ESS according to any of the preceding claims, wherein, the power grid system is configured to receive and distribute electrical energy from the ESS.

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