Patent Application
20250175095
This application claims priority to European Patent Application No. 23212656.5, filed Nov. 28, 2023, the entire disclosure of which is incorporated herein by reference.
The present invention relates to a grid-connectable multilevel converter, a multilevel converter system and a charging system.
The demand for reliable and efficient energy storage solutions has grown significantly with the increasing integration of (renewable) energy sources and the need for grid stability. In this context, the concept of an AC battery operated on a grid, also known as a battery-supplied multilevel converter, has emerged as a promising technology. Such a system combines the benefits of energy storage batteries with the flexibility and functionality of a multilevel converter, enabling seamless integration and operation within an alternating current (AC) power grid.
The battery-supplied multilevel converter functions as a bridge between the grid and the energy storage battery, facilitating bidirectional power flow and ensuring optimal utilization of stored energy. By utilizing a multilevel converter architecture, which consists of multiple power converter modules with varying voltage levels, the system achieves enhanced voltage quality, reduced harmonic distortion, and improved power flow control.
The core component of this system is the energy storage battery, which serves as a reliable and efficient source of electricity. The battery is designed, for example, to store excess energy during periods of low demand or high renewable energy generation, and subsequently release the stored energy during peak demand or periods of low energy availability. By operating within the AC grid, the battery-supplied multilevel converter provides dynamic support to the grid, contributing to grid stability, load balancing, and frequency regulation.
Also, in the realm of electric vehicles (EVs) and their charging infrastructure, the demand for faster charging times and increased driving range continues to drive innovation. One essential component of this ecosystem is the DC charger, which allows for efficient and rapid charging of EV batteries. To optimize the charging process, conventional battery boosters have been developed as a key technology to enhance the performance of DC chargers.
Conventional battery boosters for DC chargers are devices specifically designed to augment the charging capabilities of the DC charging system. They are utilized to overcome the limitations associated with power distribution networks, grid constraints, and the capacity of the charging station infrastructure. By integrating a battery booster into the charging system, the charging power can be significantly increased, leading to reduced charging times and improved user convenience.
The conventional battery booster operates by storing energy from the grid during periods of low demand or excess electricity generation. This stored energy is then utilized to provide an additional power boost during high-demand periods or when rapid charging is required. By effectively managing the power flow and providing a temporary energy buffer, battery boosters enable the DC charger to operate at higher power levels without overloading the grid or compromising the stability of the power supply.
This technology not only benefits EV owners by reducing charging time and increasing the availability of charging stations, but also addresses the challenges associated with the overall electricity grid infrastructure. Conventional battery boosters for DC chargers play a crucial role in the transition to sustainable transportation by optimizing the charging process, improving the charging experience, and facilitating the widespread adoption of electric vehicles.
However, conventional battery boosters for DC chargers usually connect the to be charged battery directly to a DC link. Such a configuration leads to harmful micro cycling which leads to a decreasing battery lifetime. Alternatively, the battery is connected via a DC/DC converter, that is usually configured as a cascaded DC/DC converter. However, such cascaded DC/DC converters suffer from low efficiency and a therefore not preferably for the overall efficiency of the provided boosting function. Furthermore, the conventional DC charger topology does not allow bidirectional power/energy flow.
Against this background, it is an object to provide an improved multilevel converter, and/or a corresponding improved multilevel converter system. Also, it is an object to provide an improved charging system.
The object is attained by a grid-connectable multilevel converter having the features of claim 1. Furthermore, the object is attained by a multilevel converter system having the features of claim 12. Also, the object is attained by a charging system having the features of claim 13.
Advantageous embodiments of the present disclosure are the subject matter of the dependent claims. Any and all combinations of at least two features disclosed in the description, the claims, and/or the figures fall within the scope of the present disclosure. Naturally, the explanations given in connection with the grid-connectable multilevel converter equivalently relate to the multilevel converter system and/or the charging system according to the present disclosure without being mentioned redundantly in its/their context. In particular, linguistically common rephrasing and/or an analogous replacement of respective terms within the scope of common linguistic practice, in particular the use of synonyms backed by the generally recognized linguistic literature, are, of course, comprised by the content of the disclosure at hand without every variation having to be expressly mentioned.
In accordance with a first aspect, a grid-connectable multilevel converter configured for at least temporarily interfacing a particularly three-phase power grid and/or for at least temporarily providing a direct current mode. The multilevel converter comprising at least a first modular energy storage string having a plurality of energy sources and at least one power converter module, the at least one power converter module comprising at least two switching elements. The at least two switching elements being configured for selectively switching each of the plurality of energy sources, preferably with respect to one another, to operate the at least first modular energy storage string in an alternating current mode, in which the at least first modular energy storage string is connectable to a first phase of the particularly three-phase power grid. Furthermore, the at least two switching elements being configured for selectively switching each of the plurality of energy sources to operate the at least first modular energy storage string in the direct current mode.
The present application thus relates to a grid-connectable multilevel converter designed to interface with a particularly three-phase power grid and provide a direct current mode when needed. The multilevel converter incorporates a first modular energy storage string consisting of multiple energy sources and at least one power converter module. The power converter module comprises a set of at least two switching elements. These switching elements are preferably strategically configured to selectively switch each of the energy sources, allowing the first modular energy storage string to operate in either an alternating current mode, where it can be connected to a first phase of the particularly three-phase power grid, or in a direct current mode. Thus, herein, a technical solution for the above-identified object is provided. Particularly, the grid-connectable multilevel converter can be operated on the grid and can provide a power boosting and/or charging function, preferably for multiple different and or selectable voltage levels, in the DC mode. Thereby, it becomes possible to operate the grid-connectable multilevel converter on the grid in an AC mode and/or for charging and/or discharging and/or boosting in the DC mode. Thereby, the herein presented multilevel converter preferably provides a direct DC link to the to be charged or charge-boosted electrical energy storage. Thus, no additional power conversion, such as a DC/DC converter, is needed. The herein presented multilevel converter is preferably a single star multilevel converter and/or a modular multilevel converter. Thus, particularly due to the at least two switching elements, a circuit of the plurality of energy sources may be reconfigurable for different purposes, such as an AC grid operation and/or a DC charging boost, preferably providable for different voltage levels. The AC grid operation may be to provide a support service and/or an energy trading function and/or a self-charging function for the multilevel converter. The claimed grid-connectable multilevel converter presents a novel and efficient solution for integrating energy sources into existing power grids while enabling flexible operation modes.
The claimed multilevel converter is preferably configured to be operated on the particularly three-phase power grid and furthermore, in the direct current mode, where the multilevel converter is preferably reconfigurable such that at least one phase can be disconnected from the particularly three-phase power grid to provide at least two direct current (DC) terminals. In other words, the grid-connectable multilevel converter can at least temporarily be configured to interface the power grid and/or to provide a DC output in the direct current mode (also named DC mode hereinafter). In such a DC mode, the grid-connectable multilevel converter may be preferably configured to provide a power boosting function and/or a charging function for a direct current charging operation of an electrical DC-load connectable to the at least two DC terminals of the grid-connectable multilevel converter.
The power grid may be considered as a single-or multiphase power grid. Thus, the term “three-phase power grid” may be replaceable with single-or multiphase power grid without leaving the claimed scope. Such a multiphase power grid may have at least two phases. Thus, the claimed three-phase power grid should not be understood as to narrow down the claimed scope.
It should be noted that the plurality of energy sources may preferably be at least temporarily connected in series. The plurality of energy sources may at least temporarily be connected in series positive and/or in series negative. Also, particularly depending on the setup of the power converter module, the plurality of energy sources may at least temporarily be connected in parallel or in a bypass connection. Such a setup of a power converter module may comprise at least three switches to provide parallel connection. The connection options may depend on the topology of the power converter module and/or the number of switching elements. Topologies with two switching elements may be configured for series positive and/or bypass connection. Topologies with three switching elements may be configured for parallel connection, particularly preferable with single polarity. Topologies with four switching elements may be configured for series positive, series negative and/or bypass connection. Topologies with five or more switching elements may be configured for series positive, series negative, bypass and/or parallel connection. The energy source may be any kind of energy source, like, for example, a battery and/or a photovoltaic cell and/or a fuel cell and/or an electromechanical power converter and/or a capacitive energy source.
“Grid-connectable multilevel converter” preferably refers to a device designed to facilitate the connection and/or interaction between a power grid and an energy storage system, preferably allowing bidirectional power flow and/or the exchange of electrical energy. The converter is preferably capable of adapting to the voltage and/or frequency requirements of the power grid, preferably enabling seamless integration and/or operation.
“Three-phase power grid” preferably refers to a power distribution system consisting of three alternating current (AC) voltage sources, preferably generated and/or transmitted at 120 degrees phase separation from each other. Of course, the phase power grid may have less than three phases, for example one or two phases, or more than three phases. The three-phase power grid is a common configuration used for large-scale power transmission and/or distribution, preferably providing efficient and balanced power delivery.
“Direct current mode” preferably refers to a mode of operation where the multilevel converter supplies and/or accepts direct current (DC) power. In this mode, the energy sources within the multilevel converter are preferably configured to provide and/or receive a continuous flow of electric current with a constant polarity.
“First modular energy storage string” preferably refers to a set of interconnected energy sources (or energy storage units) arranged in a modular fashion. The plurality of energy sources preferably collectively forms a primary energy storage/delivery component within the multilevel converter. The plurality of energy sources is preferably designed to store and/or provide electrical energy for use and power support as required.
“Energy sources” preferably refer to the individual components or units within the first modular energy storage string that store and/or deliver electrical energy. These sources can include batteries, supercapacitors, or any other energy storage devices capable of storing and delivering electrical power.
“Power converter module” preferably refers to a module within the multilevel converter that facilitates the conversion and/or control of electrical power. It includes circuitry, such as switching elements, to manipulate the flow of electrical energy and regulate voltage and current levels.
“Switching element” preferably refers to electronic devices, such as transistors or thyristors, used within the power converter module to control the flow of electric current. These elements can be turned on or off selectively to enable or interrupt the current path and facilitate the desired energy transfer or conversion.
“Alternating current mode” preferably refers to a mode of operation where the multilevel converter operates in synchrony with the alternating current (AC) waveform of the power grid. The switching elements are preferably configured to selectively switch the energy sources, preferably allowing the multilevel converter to supply and/or receive AC power that preferably matches the characteristics of the grid's AC voltage and/or frequency.
“Connectable to a first phase of the three-phase power grid” preferably refers to the capability of the first modular energy storage string to be electrically connected to one of the three phases of the three-phase power grid. This connection preferably enables the multilevel converter to interface with the grid, exchange power, and/or contribute to grid operations while maintaining synchronization with the grid's voltage and/or phase.
In an embodiment, the at least two switching elements being configured for selectively switching each of the plurality of energy sources, preferably with respect to one another, at least temporarily in series positive and/or in series negative and/or in a positive bypass state and/or in a negative bypass state and/or in parallel to operate the at least first modular energy storage string in an alternating current mode. Alternatively or additionally, the at least two switching elements being configured for selectively switching each of the plurality of energy sources at least temporarily in series positive and/or in series negative and/or in a positive bypass state and/or in a negative bypass state and/or in parallel to operate the at least first modular energy storage string in the direct current mode. Of course, the at least one power converter module may have a switch configuration with more than two switches. “Series positive/negative” preferably refers to that the switching elements allow the energy sources to be connected in series positive or series negative configurations. Series positive preferably refers to connecting the positive terminals of one energy source, i.e., of the first module, to negative terminal of a neighboring energy source, i.e., of the second module. Series negative preferably refers to connecting the negative terminals of one energy source, i.e., of the first module, to positive terminal of a neighboring energy source, i.e., of the second module.
“Positive bypass/negative bypass” preferably refers to that the switching elements enable a positive bypass state or a negative bypass state. Positive bypass preferably means that a positive current rail for bypassing an energy source, i.e., of the first or the second module, is used. Negative bypass preferably means that a negative current rail for bypassing an energy source, i.e., of the first or the second module, is used. It may applies for both current polarities. “Parallel operation” preferably refers to that the switching elements facilitate parallel connection of the energy sources, i.e., of the first and the second module. This preferably means that the positive terminals of the sources can be connected, and the negative terminals can be connected, allowing them to work collectively.
In a further embodiment, the multilevel converter further comprising at least a second modular energy storage string and/or a third modular energy storage string, the second and/or the third modular energy storage string being equivalently configured to the at least first modular energy storage string, wherein, in the alternating current mode, the second modular energy storage string is connectable to a second phase of the particularly three-phase power grid, and/or wherein, in the alternating current mode, the third modular energy storage string is connectable to a third phase of the three-phase power grid; wherein, in a direct current mode, the first and/or the second and/or the third modular energy storage string is/are configured for providing a charging function for a direct current charging operation and/or a power boosting function for a direct current charging operation, respectively or cumulatively. “Charging function” preferably refers to that the first and/or second and/or third modular energy storage string is/are configured to provide a charging function. The charging function preferably refers to a self-charging function. This preferably means they are designed to receive electrical energy from an external source and store it within the energy storage modules. The claim doesn't specify the specific nature of the charging operation or the source of the electrical energy. “Power boosting function” preferably refers to that the first and/or second and/or third modular energy storage string is/are also configured to provide a power boosting function. This preferably implies that the energy storage strings can increase the output current and/or the electric power of a charger unit that is used for charging an electrical load. “Direct current charging operation” preferably refers to that the charging and/or power boosting functions of the modular energy storage strings are preferably intended for direct current (DC) charging operations, respectively. This preferably suggests that the provided multilevel converter is designed to facilitate the charging of DC-powered devices or systems. Cumulative functionality preferably means that the features mentioned above, including the charging function and the power boosting function, can be utilized individually or in combination. The claim indicates that the first, second, and third energy storage strings can perform these functions separately or together, allowing for flexibility and adaptability in different charging scenarios and/or voltage levels for charging.
The second modular energy storage string preferably having a plurality of energy sources and at least one power converter module, the at least one power converter module preferably comprising at least two switching elements. The at least two switching elements being configured for selectively switching each of the plurality of energy sources, preferably with respect to one another, to operate the at least second modular energy storage string in an alternating current mode, in which the at least second modular energy storage string is connectable to a second phase of the particularly three-phase power grid. Furthermore, the at least two switching elements being configured for selectively switching each of the plurality of energy sources to operate the at least second modular energy storage string in the direct current mode.
The third modular energy storage string preferably having a plurality of energy sources and at least one power converter module, the at least one power converter module preferably comprising at least two switching elements. The at least two switching elements being configured for selectively switching each of the plurality of energy sources, preferably with respect to one another, to operate the at least third modular energy storage string in an alternating current mode, in which the at least third modular energy storage string is connectable to a third phase of the particularly three-phase power grid. Furthermore, the at least two switching elements being configured for selectively switching each of the plurality of energy sources to operate the at least third modular energy storage string in the direct current mode.
In a further embodiment, the first modular energy storage string is connectable or connected with the second modular energy storage string via at least a first string contactor. Alternatively, or additionally, the second modular energy storage string is connectable or connected with the third modular energy storage string via at least a second string contactor. Alternatively, or additionally, the first modular energy storage string is connectable or connected with the third modular energy storage string via at least a third string contactor. Alternatively, or additionally, the first to the third modular energy storage string is connectable or connected to a common star point. Here, a contactor may also describe any kind of switch and/or any kind of switch matrix suitable for performing the connection between the respective strings. It may be considered that if the first and the second string contactors are closed, a connection to a common star point is achieved. However, if no optional string contactors are present, the first and/or the second and/or the third modular energy storage may be permanently connected to a common star point, meaning that the first and/or the second and/or the third modular energy storage may be provided in star point connection configuration. The connection between the first and the second phase string may be performed via the common star point. A (common) star point, in electrical systems, preferably refers to a central reference or connection point. It is preferably used in configurations where multiple components or elements are connected in a star or radial pattern. In this context, the first and/or second and/or third modular energy storage string can be interconnected or linked to a shared central connection point known as the common star point. This configuration preferably allows for the consolidation or convergence of electrical connections from these energy storage strings. It preferably enables them to share a common reference point, which may have various advantages in terms of electrical distribution, control, and/or monitoring within the multilevel converter and/or multilevel converter system and/or charging system.
In a further embodiment, the first modular energy storage string is connectable in series with at least the second modular energy storage string via at least a fourth string contactor. Alternatively, or additionally, the second modular energy storage string is connectable in series and/or in parallel with at least the third modular energy storage string via at least a fifth string contactor. It may also be possible that the first modular energy storage string is connectable in series with at least the third modular energy storage string via a sixth string contactor. Here, a contactor may also describe any kind of switch and/or any kind of switch matrix suitable for performing the connection between the respective strings.
In a further embodiment, the at least first modular energy storage string is connectable to the first phase of the three-phase power grid by a preferably phase-individual first grid contactor; and/or wherein the at least second modular energy storage string is connectable to the second phase of the three-phase power grid by a preferably phase-individual second grid contactor; and/or wherein the at least third modular energy storage string is connectable to the third phase of the three-phase power grid by a preferably phase-individual third grid contactor. Here, a contactor may also describe any kind of switch and/or any kind of switch matrix suitable for performing the connection between the respective strings. According to said embodiment, the respective grid contactor is preferably placed at the top grid rails of the respective phase of the preferably three-phase power grid. By said placement, copper savings can be achieved in comparison to a placement of the contactors and a grid connecting side of the at least one multilevel converter and/or the at least one multilevel converter system. Of course, the multilevel converter may have more than three phases, particularly if the power grid comprises more than three phases as well.
In a further embodiment, the first modular energy storage string comprises at least two terminal connections, the terminal connections configured for, in the direct current mode, providing a direct current input and/or output, preferably for a power boosting and/or charging and/or discharging function; and/or wherein the second modular energy storage string comprises at least two terminal connections, the terminal connections configured for, in the direct current mode, providing a direct current output, preferably for the power boosting and/or charging and/or discharging function; and/or wherein the third modular energy storage string comprises at least two terminal connections, the terminal connections configured for, in the direct current mode, providing a direct current output, preferably for the power boosting and/or charging and/or discharging function. Multiplexing and/or routing may be used to change between terminal connections, in particular, if a to be provided voltage level between two respective terminal connections may be changed. “Terminal connections” preferably refers to specific points and/or connectors on the first and/or second and/or third modular energy storage string where external connections or connections to an exterior of the multilevel converter can be made. The claim indicates that there are at least two terminal connections, preferably suggesting there are two separate points on the respective string for making external connections. “Direct current output” preferably refers to the terminal connections on the first and/or second and/or third modular energy storage string that are configured to provide a direct current (DC) output. In the direct current mode of operation, the respective string is designed to deliver electrical energy in the form of direct current. This output can be used to power and/or boost-charge and/or charge other devices or systems that require DC input. By having at least two terminal connections on the respective modular energy storage string, the system allows for the transfer of direct current output to external components or devices, preferably enabling the utilization of the stored energy in a direct current mode of operation.
In a further embodiment, a respective first terminal connection of the at least two terminal connections, particularly per string, is provided on a grid connecting side of the respective first and/or second and/or third modular energy storage string, and wherein a respective second terminal connection of the at least two terminal connections is provided at the common star point. In other words, at least one of at least two respective terminal connections per string may be arranged at the common star point, whereas the other one of the at least two respective terminal connections per string may be arranged at a grid-side of the respective modular energy storage string. “Grid connecting side” preferably means that the respective terminal connection is located on the side of the energy storage string that is connected or connectable to the power grid.
In a further embodiment, each of the at least two terminal connections of the respective first and/or second and/or third modular energy storage string is operable via a respective terminal contactor. Here, a contactor may also describe any kind of switch and/or any kind of switch matrix suitable for performing the connection between the respective strings. “Terminal contactor” preferably refers to a device or component that enables the operation or control of the terminal connections. Each of the at least two terminal connections in the respective modular energy storage string is operable via a respective terminal contactor. This means that there may be a contactor preferably associated with each terminal connection, preferably allowing for independent operation and/or control of the respective terminal connection.
In a further embodiment, the first energy storage string comprises a first grid filter arranged between the first grid contactor and a respective first one of the preferably series connected plurality of energy sources of the first energy storage string; and/or wherein the second energy storage string comprises a second grid filter arranged between the second grid contactor and a respective first one of the preferably series connected plurality of energy sources of the second energy storage string; and/or wherein the third energy storage string comprises a third grid filter arranged between the third grid contactor and a respective first one of the preferably series connected plurality of energy sources of the third energy storage string. “Grid filter” preferably refers to a component that is positioned between the first grid contactor and a particular energy source within the first energy storage string. The grid filter is preferably designed to filter and/or condition the electrical signals and/or power flowing between the grid contactor and the specified energy source and/or string. These filters may be used to remove noise and/or harmonics and/or other undesirable components from an electrical signal and/or energy flow. “Grid contactor” preferably refers to a device and/or component that enables the connection and/or disconnection of the respective energy storage string to or from the power grid. It preferably controls the electrical connection between the respective energy storage string and the power grid.
In a further embodiment, at least one terminal filter is provided on at least one of the terminal connections of the respective first and/or second and/or third modular energy storage string.
In a further embodiment, at least one of the least two terminal connections of the first and/or second and/or third modular energy storage string is connected to at least partly bypass the first and/or second and/or third grid filter. In other words, the bypass configuration may allow the electric current to at least partly bypass or at least partly avoid the respective filter in the circuit. In this case, at least one of the terminal connections associated with the first and/or second and/or third modular energy storage string may be connected in a way that partially or completely bypasses the first and/or second and/or third grid filter. This means that the electric current can flow directly from the terminal connection to another part of the circuit of the multilevel converter without passing through the respective grid filter or only by passing through a part of the respective grid filter. It should be understood that the first and/or second and/or third grid filter may only partly be bypassed. Grid filters may be used for filtering or may be bypassed depending on the operating mode, in particular, a modulating mode or a stable mode. The modulating operating mode may have an alternating output voltage and therefore may require use of filters. During the stable operating mode, the stable operating mode having a constant or only slowly varying output voltage, the filters may be bypassed. It should be noted that the grid filters may be designed to filter out modulation noise, which may be the same in every phase or string, particularly when connected in series. Therefore, connecting three filters in series may not be required, as it may add additional conduction and core losses to the overall system. In such a configuration, the respective grid-connecting side terminal connection may be placed such that only a part of the first and/or second and/or third grid filter is utilized. In such a configuration, not the whole respective grid filter, but only a part of it is used for the direct current mode operation. A main advantage of providing the option for bypassing the first and/or second and/or third grid filter is that, depending on the setup and/or configuration of the multilevel converter and/or respective energy storage string, string specific filters and/or string individual filters may be used. Thus, not every energy storage string needs to be provided with the same filter. This may be advantageous regarding capital costs. In addition, bypassing redundant filters or filter stages may reduce conduction and/or core losses.
In a further embodiment, in the alternating current mode, the at least first modular energy storage string is configured to be run in an energy trading mode, when the at least first modular energy storage string is connected to the first phase of the three-phase power grid,
wherein, in the energy trading mode, electric energy is transferable and/or interchangeable between the plurality of energy sources of the at least first modular energy storage string and at least the first phase of the three-phase power grid; and/or wherein, in the alternating current mode, the at least first modular energy storage string is configured to be run in a grid support mode, when the at least first modular energy storage string is connected to the first phase of the three-phase power grid, wherein, in the grid support mode, electric energy is transferable and/or interchangeable between the plurality of energy sources of the at least first modular energy storage string and at least the first phase of the three-phase power grid for supporting a grid frequency control operation and/or for supporting a reactive power compensation. It should be understood that these features equally apply for the second and/or third modular energy storage string. The particularly three-phase grid may be part of a charging system including at least one of the claimed multilevel converters.
In a further embodiment, in the alternating current mode, the at least first modular energy storage string is configured to be run in a self-charging mode, when the at least first modular energy storage string is connected to the first phase of the three-phase power grid, wherein, in the self-charging mode, electric energy is transferable from the at least the first phase of the three-phase power grid to the plurality of energy sources of the at least first modular energy storage string.
In accordance with a second aspect, a multilevel converter system is provided. The multilevel converter system comprising at least two multilevel converters as claimed herein before and hereinafter. The at least two multilevel converters are connectable via at least one multilevel converter contactor. Here, a contactor may also describe any kind of switch and/or any kind of switch matrix suitable for performing the connection between the respective strings. Considering the technically smallest possible entity, the at least one multilevel converter contactor may be configured to connect the respective first strings of the respective multilevel converters together.
In an embodiment of the multilevel converter system, the at least one multilevel converter contactor is configured to connect the at least two multilevel converters to the common star point, wherein, in the direct current mode, an output voltage of a common direct current output of the at least two multilevel converters is increased, particularly for providing a power boosting and/or charging function.
In accordance with a third aspect, a charging system for direct current charging or discharging of an electrical energy storage of at least one electrical consumer, preferably an electric vehicle, is provided. The system comprises the at least one electrical consumer including the electrical energy storage; a preferably three-phase power grid; a front-end converter unit connectable to the preferably three-phase power grid and configured for converting and/or rectifying an alternating current of the preferably three-phase power grid to a direct current used for charging the electrical energy storage; and a direct current charging unit connectable to the front-end converter unit; the electrical energy storage being at least temporarily connectable to the direct current charging unit to perform a direct current charging operation; and at least one multilevel converter according to any one of the herein presented embodiments and/or at least one multilevel converter system according to any one of the herein presented embodiments. It should be understood that the energy flow of the charging system may be bidirectional. Thus, energy can be charged into the electrical energy storage and/or can be discharged from the electrical energy storage, for example to provide said discharge energy to at least one phase of a preferably three-phase grid. For example, the charging system, in particular, the electrical energy storage, may get charged from any suitable direct current (DC) source, such as a power bank or a power wall or the like, wherein said charging energy is directly or indirectly provided to the at least one phase of the preferably three-phase grid. In such a configuration, the at least one multilevel converter and/or the at least one multilevel converter system may be configured to provide said energy flow to the at least one phase of the preferably three-phase grid in an alternating current configuration. This may be considered as a reversal mode, where the at least one multilevel converter and/or the at least one multilevel converter system converts and/or transfers and/or pushes energy from the electrical energy storage into at least one phase of the preferably three-phase grid.
In an embodiment of the charging system, in the direct current mode, the at least one multilevel converter and/or the at least one multilevel converter system being at least temporarily connectable in parallel to the direct current charging unit for providing a power boosting function and/or a charging function for the direct current charging operation; or wherein, in the direct current mode, the at least one multilevel converter and/or the at least one multilevel converter system being at least temporarily connectable in parallel to the front-end converter unit for providing a power boosting function and/or a charging function for the direct current charging operation. The formulation “connectable in parallel” preferably means that the at least one current of the charging unit and the at least one current of the at least one multilevel converter and/or the at least one multilevel converter system are added and/or summed up together. In other words, “connectable in parallel” or “connected in parallel” means that the respective outputs of at least two devices that are connected in parallel, are in parallel connection. Alternatively, the at least one multilevel converter and/or the at least one multilevel converter system may be connected in parallel with the front-end converter. The front-end converter may be considered as a rectifier.
In an embodiment of the charging system, the system comprises a transformer unit, the transformer unit being interconnectable between the preferably three-phase power grid and the at least one multilevel converter and/or the at least one multilevel converter system. Such a transformer may be applied for galvanic isolation. Thus, such transformers may be redundant when such isolation is not required.
All aspects and embodiments as described above may be combined as deemed fit by the skilled person.
“A(n)” in the present case should not necessarily be understood to be restrictive to exactly one element. Rather, a plurality of elements, such as, for example, two, three or more, can also be provided. Any other numeral used here, too, should not be understood to the effect that there is a restriction to exactly the stated number of elements. Rather, numerical deviations upwards and downwards are possible, unless indicated to the contrary.
Further possible implementations of the invention also comprise not explicitly mentioned combinations of any features or embodiments that are described above or below with respect to the exemplary embodiments. In this case, a person skilled in the art will also add individual aspects as improvements or supplementations to the respective basic form of the invention.
Unless indicated to the contrary, elements that are the same or functionally the same have been given the same reference signs in the figures. It should also be noted that the illustrations in the figures are not necessarily true to scale.
The charging system 100 further includes a preferably three-phase power grid 106, a front-end converter unit 108 that is at least temporarily connectable to the preferably three-phase power grid 106 and configured for rectification of an alternating current of the power grid 106 and/or for inverting a DC current, preferably used for charging the electrical energy storage 102. Also, the charging system 100 may comprise a direct current charging unit 110 that may at least temporarily be connectable to the front-end converter unit 108. Of course, it shall be understood that in other embodiments, there may be more conversion stages, for example isolated DC-DC conversion by a further DC-DC converter. According to the shown refinement, the electrical energy storage 102 is at least temporarily connectable to the direct current charging unit 110 to perform a direct current charging operation for charging the electrical energy storage 102. To support and/or boost and/or at least partly substitute the direct current charging unit 110, especially during the charging operation, the charging system 100 comprises at least one multilevel converter 112 and/or at least one multilevel converter system 114 that comprises at least two multilevel converters 112. The multilevel converter 112 may be considered as an alternating current battery storage (AC battery) that is suitable for being at least temporarily switched into at least one direct current mode.
Only optionally, the charging system 100 may also include a DC/DC converter 116 that may be interconnected on an output side of the at least one multilevel converter 112 and/or the at least one multilevel converter system 114 between the at least one multilevel converter 112 and/or the at least one multilevel converter system 114 and the front-end converter unit 108.
According to
According to
The respective multilevel converter 112 is configured for at least temporarily interfacing the preferably three-phase power grid 106 and/or for at least temporarily providing the above-indicated direct current mode. The respective multilevel converter 112 comprises at least a first modular energy storage string 300 having a plurality of energy sources 302 and at least one power converter module 304. The at least one power converter module 304 may be included in the plurality of energy sources 302. For clearness, only one of the respective energy sources per string is marked in
The at least two switching elements 2800 being configured for selectively switching each of the plurality of energy sources 302 to operate the at least first modular energy storage string 300 in an alternating current mode, in which the at least first modular energy storage string 300 is connectable to a first phase 306 of the three-phase power grid 106. Also, the at least two switching elements 2800 are configured for selectively switching each of the plurality of energy sources 302 to operate the at least first modular energy storage string 300 in the at least one direct current mode. The at least two switching elements 2800 are configured for selectively switching each of the plurality of energy sources 302 at least temporarily in series positive and/or in series negative and/or in a positive bypass state and/or in a negative bypass state and/or in parallel to operate the at least first modular energy storage string 300 in an alternating current mode. Alternatively or additionally, the at least two switching elements 2800 are configured for selectively switching each of the plurality of energy sources 302 at least temporarily in series positive and/or in series negative and/or in a positive bypass state and/or in a negative bypass state and/or in parallel to operate the at least first modular energy storage string 300 in the direct current mode.
The respective multilevel converter 112 further comprises at least a second modular energy storage string 308 and/or a third modular energy storage string 310. The second modular energy storage string 308 preferably having a plurality of energy sources 312 and at least one power converter module 314, the at least one power converter module 314 preferably comprising the at least two switching elements 2800 (consider
The third modular energy storage string 310 preferably having a plurality of energy sources 318 and at least one power converter module 320, the at least one power converter module 320 preferably comprising the at least two switching elements 2800 (consider
In the alternating current mode, the first modular energy storage string 300 is connectable to the first phase 306 of the three-phase power grid 106 by a first grid contactor 324. Alternatively or in addition, in the alternating current mode, the second modular energy storage string 308 is connectable to the second phase 316 of the three-phase power grid 106 by a second grid contactor 326. Alternatively or in addition, in the alternating current mode, the third modular energy storage string 310 is connectable to a third phase 322 of the three-phase power grid 106 by a third grid contactor 328.
In a direct current mode, the first and/or the second and/or the third modular energy storage string 300, 308, 310 is/are configured for providing at least a charging function for a direct current charging operation and/or at least a power boosting function for a direct current charging operation, respectively. Particularly, each of the strings 300, 308, 310 may be configured individually to provide such an additional function for a direct current charging operation. In the alternative or additionally, at least two of the at least three strings 300, 308, 310 may be connected to provide such an additional function for a direct current charging operation and/or to attain the possibility of providing such an additional function at multiple different voltage levels.
According to
According to string connection option A, the first modular energy storage string 300 is connectable with the second modular energy storage string 308 via at least a first string contactor 330. Furthermore, the second modular energy storage string 308 is connectable with the third modular energy storage string 310 via at least a second string contactor 332. Also, according to
According to string connection option B, the first modular energy storage string 300 is connectable with the second modular energy storage string 308 via the first string contactor 330 and the second string contactor 332, particularly, by closing both the first and the second string contactor 330, 332. Furthermore, the second modular energy storage string 308 is connectable with the third modular energy storage string 310 via at least the second string contactor 332 and a third string contactor 338, particularly, by closing both the second and the third string contactor 332, 338. Also, the first modular energy storage string 300 is connectable with the third modular energy storage string 310 via at least the first string contactor 330 and a third string contactor 338, particularly, by closing both the first and the third string contactor 330, 338. According to the shown option B, on the grid-connecting side of the lower multilevel converter 112, the contactors 330, 332 and 338 are pulled or moved outwards towards the first terminal connection 333 via corresponding current taps on the grid-connecting side of the respective string. Furthermore, as already mentioned for option A, from the common star point 334, the second terminal connection 336 is drawn outwardly. According to option B, the string contactors 330, 332, 338 can be used as respective, string individual terminal contactors, preferably for opening and/or closing the terminal connection 333 in a string individual manner.
Further to
It should be understood that the detailed structure of a multilevel converter 112 is shown in
According to
According to
According to
It should be noted that X Volt may be the maximum output voltage providable per modular energy storage string 300, 308, 310, respectively.
It shall be noted that the switching topology may be selected with respect to filtering requirements on an AC-side and a DC-side of the multilevel converter system. The more filtering capability is required on the DC-side, the more inductors may be involved in the DC configuration.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23212656.5 | Nov 2023 | EP | regional |
