ARRANGEMENT FOR FEEDING ELECTRICAL POWER INTO AN AC VOLTAGE NETWORK

Description

[0001] The invention relates to an arrangement for feeding electrical power into an alternating current network.

[0002] Energy generation from renewable sources presents a challenge in terms of the volatility of production and the quality of transmission. Both feeding the generated energy into the grid and storing it require new solutions for the existing AC power grid infrastructure.

[0003] A suitable arrangement is known from the prior art that converts a direct current voltage supplied by a power generation plant into an alternating current voltage by means of a power converter and feeds it into a connected alternating current network. However, this type of power feed-in does not meet the requirements arising from the volatility of power generation.

[0004] Furthermore, arrangements for the (intermediate) storage of electrical energy are known that can be connected to an AC power grid. EP 3 487 026 A1 discloses a converter arrangement comprising a converter and a storage arrangement. The converter can be connected to the AC power grid via its AC voltage side. The storage arrangement is connected to the DC voltage side of the converter. By exchanging active and reactive power with the AC power grid, the known converter arrangement is particularly suitable for grid stabilization.

[0005] From US patent 2015 / 0270801 A1, a storage arrangement is known which comprises a series connection of modules, each comprising a storage unit or a PV module, and which can feed the stored or generated energy into an AC grid.

[0006] Another energy storage and feed-in device is known from WO 2014 / 181081 A1 and CN 109 921 448 A.

[0007] The object of the invention is to propose an arrangement mentioned above which enables the most reliable possible energy feed-in, in particular from renewable energy sources, in accordance with the requirements of energy generation.

[0008] The object of the invention is achieved by an arrangement for feeding electrical power into an AC network, comprising a plurality of feed-in modules, wherein each feed-in module comprises a converter module for converting an (input-side) DC voltage into an (output-side) AC voltage and a storage module for storing electrical energy, wherein the storage module is connected to a DC side of the converter module and an AC side of the converter module is provided for connection to the AC network and / or to at least one further (advantageously one adjacent in the resulting series connection) of the feed-in modules, so that the feed-in modules form a series connection on the AC side that can be connected to the AC network (connected to the AC network during operation of the arrangement), wherein one of the storage modules is provided for connection to a power generation plant.The present invention therefore proposes an arrangement that enables both the direct feed-in of generated energy and its storage. By integrating the conversion and storage functionalities into the arrangement of cascaded feed-in modules, the required operating resources can be reduced, which also applies to operational losses. The energy generated by the power generation plant is fed into at least one of the storage modules. The energy stored there can be fed into the output AC grid via at least one of the converter modules, whereby a DC voltage can be converted into an AC voltage of the AC grid. The feed-in modules are connected in series on the output side, so that the output voltage corresponds to the sum of the voltages generated at the individual feed-in modules.Such a modular design advantageously allows for adaptation to the respective operating voltage of the AC power grid.

[0009] Suitablely, only some of the feed-in modules in the series connection can be connected to the power generation plant, or are connected to the power generation plant during operation. Accordingly, the system is connected to the power generation plant exclusively via these selected storage modules, so that electrical energy is transferred from the power generation plant to these selected storage modules. The energy absorbed by some of the storage modules can be transferred to the remaining storage modules by means of recharging. In this context, the feed-in and storage modules are referred to as a cascaded arrangement. The recharging can, for example, occur cyclically to achieve an even charge distribution in the storage modules. The storage modules suitably include capacitors, whereby a capacitor voltage can be generated across the capacitors through recharging or charge equalization.According to the invention, only the storage module of a first feed-in module, i.e., the feed-in module with the lowest potential, can be connected to the power generation plant or is connected during operation. Due to the cascaded arrangement or series connection of the feed-in modules, the feed-in modules are at different potential levels during operation. The first or lowest module in the arrangement is therefore the one with the lowest potential, i.e., the one that is at the lowest potential level during operation. Connecting the storage module with the lowest potential, or the storage module of the feed-in module with the lowest potential, to the power generation plant has the advantage that the insulation requirements are relatively low. The feed-in modules themselves can also be supplied with energy by means of cascading.

[0010] The feed-in modules are ideally configured to exchange electrical energy with each other. Charge balancing between the feed-in and storage modules ensures even utilization of the storage modules and, if necessary, the previously described cascading.

[0011] Preferably, each of the power supply modules has a balancing module for exchanging electrical energy with other power supply modules, wherein the balancing module comprises switchable semiconductor switches and the energy exchange is carried out by controlling the semiconductor switches. The semiconductor switches, e.g., IGBT, IGCT, or other suitable power semiconductors, can, for example, be connected to the electrical switch of the storage module in such a way that, by means of suitable switching operations, the storage module is electrically connected or bridged with an adjacent storage module.

[0012] Preferably, the connection of the arrangement to the AC power grid is transformerless. Accordingly, the arrangement, or rather the series connection of the feed-in modules, is directly connected to the AC power grid during operation, i.e., without an intermediate transformer. Voltage adjustment is achieved solely by means of the converter modules, thus advantageously eliminating the need for a transformer. This significantly simplifies maintenance of the arrangement during operation.

[0013] Advantageously, the arrangement includes a support structure designed to accommodate the feed-in modules. This support structure can, for example, be in the form of a tower in which the individual feed-in modules are arranged one above the other and / or side by side. A mounting position can be provided in the support structure for each stabilization module. This mounting position can be equipped with appropriate connections so that the feed-in module can be inserted into the support structure by forming the electrical contacts for the series connection of the feed-in modules, or removed from the support structure by disconnecting the contacts. Ideally, the feed-in module is inserted into the module holder during operation.

[0014] According to one embodiment of the invention, each feed-in module is assigned a module holder in the support structure, the module holder having a module short-circuiting device configured to short-circuit the assigned feed-in module. The module short-circuiting device is configured to bypass the assigned feed-in module. In this way, the device can continue to operate even in the event of a fault in one of the feed-in modules, by bypassing the faulty feed-in module in the series connection of the feed-in modules using the module short-circuiting device. The module short-circuiting device can, for example, comprise a mechanical switch. The module short-circuiting device can be controllable or have an automatic tripping mechanism. The feed-in modules are preferably individually removable from the support structure.

[0015] Preferably, at least one of the power supply modules can be connected to the support structure by means of extendable contacts with a touch guard, so that the power supply module can be removed from the support structure during operation of the device. The touch guard ensures safe removal of the power supply module. Advantageously, this means that even if one of the power supply modules fails, the operation of the arrangement does not have to be interrupted.

[0016] Preferably, the potential difference between adjacent feed-in modules in the series connection is less than 5 kV, preferably less than 2 kV. By connecting the feed-in modules in series or cascading them, a total voltage of virtually any desired value, adapted to the specific application, can be generated without significantly increasing the insulation requirements of the arrangement.

[0017] According to one embodiment of the invention, each feed-in module comprises an electronic module for data acquisition and / or data exchange of operating data of the respective feed-in module. The operating data is acquired, for example, by means of suitable measuring devices. The operating data can be transmitted to a central data acquisition unit. The operating data can advantageously be used for monitoring the feed-in modules. Furthermore, the data exchange allows for the control and regulation of the voltage balancing of the arrangement.

[0018] It is considered advantageous if the arrangement includes a power generation plant connected to one of the storage modules, so that the energy generated by the power generation plant can be temporarily stored in the storage module. This provides an arrangement for generating and feeding electrical energy, compensating for fluctuations in energy generation and achieving (especially short-term) stabilization / support of the AC grid.

[0019] A suitable energy generation system is either a photovoltaic (PV) system or a wind turbine. A PV system is particularly suitable because it typically supplies a direct current (DC) voltage, which can be directly converted into the alternating current (AC) voltage of the AC power grid using this setup.

[0020] The invention will be further explained below with reference to an embodiment shown in the figure.

[0021] The figure shows an embodiment of an arrangement according to the invention in a schematic representation.

[0022] The figure shows an arrangement 1 for feeding electrical energy into an AC power grid 2. The arrangement 1 comprises feed-in modules E1...En, the number of which can be arbitrary, as indicated by a dotted line 3. Each feed-in module E1...En includes a storage module S and a converter module W. In the illustrated example, a balancing module is integrated into the storage module S. In the embodiment shown in the figure, all feed-in modules E1...En have the same construction, although this is not generally necessary. An electronic module 8 for acquiring and exchanging operating data with a central control unit 4 is integrated into the converter module W in the illustrated example.

[0023] The converter modules W each have an AC voltage side and a DC voltage side. On the AC voltage side, the converter modules W are connected to each other in series and to the AC voltage network 2. On the DC voltage side, each converter module W is connected to the associated storage module S.

[0024] The storage module of the first, or lowest-potential, feed-in module E1 is connected to a power generation plant 5 in the form of a photovoltaic system. The electrical energy supplied by the power generation plant 5 is stored in the storage module S of the first feed-in module E1 (or its storage capacitor) and distributed to the other storage modules by means of charge equalization. Each converter module W can convert the energy stored in its assigned storage module S (in the form of direct current) into alternating current and feed it into the AC grid 2.

[0025] The arrangement 1 further comprises a support structure 6 in which the feed-in modules E1...En are arranged during operation. A separate mounting position is provided in the support structure 6 for each of the feed-in modules E1...En. The feed-in modules E1...En are inserted into a designated module holder M, which includes a module short-circuiting contact 7 by means of which a faulty feed-in module E1...En can be bypassed. The module holder M also includes features such as touch protection and extendable contacts, which allow the faulty feed-in module to be removed from the support structure 6 without interrupting the operation of the arrangement.

[0026] By means of a balancing module 9, each of the feed-in modules E1...En can exchange energy with the other feed-in modules.

Claims

1. An arrangement (1) for supplying electric power to an alternating current network (2) with a plurality of supply modules (E1...En), wherein each supply module (E1...En) comprises a converter module (W) for converting a DC voltage into an AC voltage and a storage module (S) for storing electrical energy, wherein the storage module (S) is connected to a DC voltage side of the converter module (W), and an AC voltage side of the converter module is configured for connecting to the alternating current network (2) and / or to at least one further one of the supply modules (E1...En) such that the supply modules (E1...En) form a series circuit connectable to the alternating current network (2) on the AC voltage side, wherein one of the memory modules is configured for connecting to an energy generating system, wherein only the storage module of a supply module having a lowest potential is connected to the energy generating system during operation of the arrangement.

2. The arrangement (1) according to claim 1, wherein storage modules of only some of the supply modules of the series circuit, preferably only the storage module of a first of the supply modules, are connectable to the energy generating system.

3. The arrangement (1) according to any one of the preceding claims, wherein the supply modules (E1...En) are configured to exchange electric energy between one another.

4. The arrangement (1) according to claim 3, wherein each of the supply modules (E1...En) has a balancing module for exchanging electrical energy with other supply modules, wherein the balancing module (9) comprises semiconductor switches which can be switched off, and the energy exchange is performed by controlling the semiconductor switches.

5. The arrangement (1) according to any one of the preceding claims, wherein the connection of the arrangement (1) to the alternating current network (2) is transformerless.

6. The arrangement (1) according to any one of the preceding claims, wherein the arrangement comprises a support structure (6) configured for receiving the supply modules (E1...En).

7. The arrangement (1) according to claim 6, wherein a module holder (M) is associated with each supply module (E1...En) in the support structure (6), wherein the module holder (M) has a module short-circuiter (7) configured for short-circuiting the associated supply module (E1...En).

8. The arrangement (1) according to claim 6 or 7, wherein at least one of the supply modules (E1...En) is connectable to the support structure (6) by means of extendable contacts to a touch protection of the arrangement such that the supply module (E1... En) is removable from the support structure (6) during operation of the device.

9. The arrangement (1) according to any one of the preceding claims, wherein a potential difference between adjacent supply modules (E1...En) of the series circuit is less than 5 kV, preferably less than 2 kV.

10. The arrangement (1) according to any one of the preceding claims, wherein each supply module comprises an electronic module (8) for data collection and / or data exchange of operating data of the respective supply module (E1...En).

11. The arrangement (1) according to any one of the preceding claims, wherein the arrangement (1) comprises an energy generating system (5) connected to at least one of the storage modules (S) such that the energy generated by meany of the energy generating system (5) can be temporarily stored in the at least one storage module (S).

12. The arrangement (1) according to claim 11, wherein the energy generating system is a PV system or a wind turbine.