Direct-current direct access system of energy storage battery
Technical Field
The invention belongs to the field of electric power energy storage, and particularly relates to an energy storage battery direct current direct access system which is used for directly accessing an energy storage battery system to an external direct current system and omitting intermediate links such as a direct current/direct current converter.
Background
In recent years, the proportion of wind power generation and photovoltaic power generation in power systems is increasing on a large scale, and in order to overcome the intermittent and fluctuating problems caused by large-scale new energy power generation, power storage becomes an indispensable part of future power systems.
In the fields of light storage integration and others, an energy storage battery system is generally required to be connected to other direct current systems such as a direct current output side of a photovoltaic power generation system, so that the power fluctuation problem of other new energy power generation systems such as photovoltaic power generation is stabilized through the energy storage battery system on the direct current side.
The existing energy storage battery system is generally provided with a battery management system to balance the charge states of different battery monomers in the same battery pack and balance the charge states of different battery packs in the same battery pack. The existing energy storage battery system cannot adjust the voltage of a direct current port of the existing energy storage battery system, and an external direct current/direct current converter is usually needed to adjust the voltage of the direct current port of the energy storage battery system, so that the voltage of the direct current port of the energy storage battery system is matched with the direct current voltage of an external direct current system, and the power and the electric energy exchanged between the energy storage battery system and the external direct current system are adjusted.
The disadvantages of the prior conventional technology are:
1. an additional direct current/direct current converter needs to be equipped for the energy storage battery system, so that the primary investment cost and the loss of the system are increased;
2. the dc/dc converter can only adjust the total voltage value of the dc port of the energy storage battery system, thereby adjusting the power and electric quantity exchanged between the whole energy storage battery system and the external dc system, and cannot adjust the power and electric quantity exchanged between each battery cluster and each battery pack and the external dc system.
Disclosure of Invention
In order to improve the defects of the prior art, the invention provides an energy storage battery direct current direct access system which is used for directly accessing an energy storage battery to an external direct current system, omitting other intermediate link links such as a direct current/direct current converter between the energy storage battery and the external direct current system, and solving the problems of high cost and high loss caused by the fact that the direct current/direct current converter needs to be additionally configured in order to access the energy storage battery to the external direct current system.
In order to achieve the above object, the present invention provides an energy storage battery dc direct access system, which includes a modular multilevel energy storage battery system, the modular multilevel energy storage battery system is formed by connecting one battery cluster or a plurality of battery clusters in parallel, the battery cluster is formed by connecting one battery pack or a plurality of battery packs in series, at least one half-bridge battery pack is arranged in the battery cluster, the half-bridge battery pack is formed by a battery pack and a half-bridge module, a dc output port of the battery pack is connected in parallel with a dc port of the half-bridge module, an ac output port of the half-bridge module is an output port of the half-bridge battery pack, and the battery pack can be put into or cut off by controlling the on and off of a switching tube of the half-bridge module, so as to change the voltage of the battery cluster. The modular multi-level energy storage battery system is called as a modular multi-level energy storage battery system because the output level number of the battery clusters can be changed by changing the number of battery packs thrown into each battery cluster. And the positive direct-current bus and the negative direct-current bus of the modular multilevel energy storage battery system are respectively and directly connected with the positive direct-current bus and the negative direct-current bus of the external direct-current system, so that the modular multilevel energy storage battery system can directly interact with the external direct-current system to generate electric energy.
The switching tube may be a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET), an Insulated Gate Bipolar Transistor (IGBT), or other well-known fully-controlled power electronic devices.
The battery pack is formed by connecting one or more battery monomers in series, and the battery pack can also be formed by connecting one or more battery monomers in series and parallel.
In the above technical scheme, the half-bridge battery pack includes a battery pack, a first switch group and a second switch group, a low-voltage end of the first switch group is connected with a high-voltage end of the second switch group, a leading-out terminal at a connection point is a first output port of the battery pack, a low-voltage end of the second switch group is connected with a low-voltage end of the battery pack, a leading-out terminal at a connection point is a second output port of the battery pack, and a high-voltage end of the first switch group is connected with a high-voltage end of the battery pack.
In the above technical solution, the battery cluster includes one or more full-bridge battery packs, each full-bridge battery pack is composed of a battery pack and a full-bridge module, positive and negative dc ports of the battery pack are connected to positive and negative dc ports of the full-bridge module, and an ac output port of the full-bridge module is an output port of the full-bridge battery pack and is used for being connected in series with one or more other battery packs.
In the above technical solution, the full-bridge battery pack includes a battery pack, a first switch group, a second switch group, a third switch group, and a fourth switch group, a low-voltage end of the first switch group is connected to a high-voltage end of the second switch group, a leading-out terminal at a connection point is a first output port of the battery pack, a low-voltage end of the third switch group is connected to a high-voltage end of the fourth switch group, a leading-out terminal at a connection point is a second output port of the battery pack, a high-voltage end of the first switch group, a high-voltage end of the third switch group, and a high-voltage end of the battery pack are connected together, and a low-voltage end of the second switch group, a low-voltage end of the fourth switch group, and a low-voltage end of the battery pack are connected.
In the technical scheme, the output voltage of the full-bridge module is adjusted to be negative voltage, zero voltage or positive voltage, so that the battery pack connected with the full-bridge module in parallel outputs the negative voltage, the zero voltage or the positive voltage, and the direct-current voltage output range of the battery cluster is expanded.
In the technical scheme, the direct current output voltage of the modular multilevel energy storage battery system is changed by changing the number of battery packs thrown into each battery cluster of the modular multilevel energy storage battery system, and the power and the electric quantity exchanged between the modular multilevel energy storage battery system and an external direct current system are adjusted.
In the technical scheme, one or more battery packs in each battery cluster in the modular multilevel energy storage battery system work in a pulse width modulation mode, so that the output voltage of the battery packs is adjusted in a closed loop manner, and the output direct-current voltage of the battery clusters can be continuously adjusted and controlled.
According to the invention, the direct current side of the modularized multi-level energy storage battery system is directly connected with the direct current side of the photovoltaic inverter of the photovoltaic power generation system to form a direct current side direct light storage integrated system.
Generally, compared with the conventional scheme of connecting the energy storage battery to other direct current systems through a direct current/direct current converter, the direct current direct connection system of the energy storage battery has the following beneficial effects:
(1) the direct current/direct current converter which is additionally arranged when the conventional battery system is connected to other direct current systems is omitted, so that the investment cost is reduced, and taking a 50MW/100MWh energy storage system as an example, the cost of the direct current/direct current converter which is required to be configured when the conventional energy storage battery system is connected to an external direct current system is about 750 ten thousand yuan;
(2) because a direct current/direct current converter is not required to be configured, the invention can effectively reduce the system loss, and the cost reduction of the system loss which can be saved is 112.5 ten thousand yuan by taking a 50MW/100MWh energy storage system and 3000 times of cyclic charge and discharge as an example.
Drawings
Fig. 1 is a schematic diagram of a conventional energy storage battery dc access system, where 21 is a conventional energy storage battery system, 7 is a dc positive bus of the energy storage battery system, 8 is a dc negative bus of the energy storage battery system, 9 is an external dc positive bus, 10 is an external dc negative bus, and 11 is a dc/dc converter.
Fig. 2 is a topology schematic diagram of an energy storage battery dc direct access system of the present invention, wherein 1 is a modular multi-level energy storage battery system, 2 is a battery pack, 3 is a battery pack, 4 is a battery cluster, 5 is a half-bridge module, 6 is an isolating switch, 7 is an energy storage battery system dc positive bus, 8 is an energy storage battery system dc negative bus, 9 is an external dc system dc positive bus, and 10 is an external dc system dc negative bus.
Fig. 3 is a direct-current side optical storage and direct integration system proposed by the present invention, in which 1 is a modular multilevel energy storage battery system, 9 is a common positive electrode direct current bus, 10 is a common negative electrode direct current bus, 12 is a photovoltaic cell panel, 13 is a direct current combiner box and a maximum power point tracking controller, 14 is a photovoltaic inverter, 15 is an alternating current transformer, and 16 is an alternating current grid.
Fig. 4 is a conventional light-storage dc integrated system, 21 is a conventional energy storage battery system, 7 is an energy storage battery system dc positive bus, 8 is an energy storage battery system dc negative bus, 11 is a dc/dc converter, 12 is a photovoltaic cell panel, 13 is a photovoltaic dc combiner box and a maximum power point tracking controller, 9 is a common positive dc bus, 10 is a common negative dc bus, 14 is a photovoltaic inverter, 15 is an ac transformer, and 16 is an ac power grid.
Fig. 5 is a topology schematic diagram of an energy storage battery dc direct access system of the invention, wherein 1 is a modular multi-level energy storage battery system, 2 is a battery pack, 3 is a battery pack, 4 is a battery cluster, 25 is a full-bridge module, 6 is an isolating switch, 7 is an energy storage battery system dc positive bus, 8 is an energy storage battery system dc negative bus, 9 is an external dc system dc positive bus, and 10 is an external dc system dc negative bus.
Fig. 6 is a direct-current side direct-storage integrated system ii proposed by the present invention, in which 1 is a modular multilevel energy storage battery system, 9 is a common positive electrode direct-current bus, 10 is a common negative electrode direct-current bus, 12 is a photovoltaic cell panel, 13 is a direct-current combiner box and a maximum power point tracking controller, 14 is a photovoltaic inverter, 15 is an alternating-current transformer, and 16 is an alternating-current power grid.
Fig. 7 is a circuit diagram of a half-bridge type battery pack, in which 2 is a battery pack, 3 is a battery pack, 5 is a half-bridge module, 31 is a first switch group, and 32 is a second switch group.
Fig. 8 is a circuit connection diagram of a full-bridge type battery pack, in which 2 is a battery pack, 3 is a battery pack, 25 is a full-bridge module, 33 is a full-bridge module first switch group, 34 is a full-bridge module second switch group, 35 is a full-bridge module third switch group, and 36 is a full-bridge module fourth switch group.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Fig. 1 is a schematic diagram of a dc access topology of a conventional energy storage battery, and the principle of the topology is that a dc positive bus and a dc negative bus of a conventional energy storage battery system 21 are connected to a positive electrode and a negative electrode of an input end of a dc/dc converter 11, and a dc output end of the dc/dc converter 11 is connected to a dc positive bus and a dc negative bus of an external dc system.
Fig. 2 shows an energy storage dc direct access system according to an embodiment of the present invention, an output end of each battery pack 2 is connected in parallel with a half-bridge module 5 to form a battery pack 3, one or more battery packs 3 are connected in series to form a battery cluster 4, one or more battery clusters 4 are connected in parallel to form a modular multilevel energy storage battery system 1, and a dc positive bus and a dc negative bus of the modular multilevel energy storage battery system 1 are directly and respectively connected to a dc positive bus and a dc negative bus of an external dc system.
As can be seen from fig. 2 in comparison with fig. 1, the conventional energy storage battery system 21 of fig. 1 needs a dc positive bus bar coupled to an external dc system through the dc/dc converter 11, whereas the energy storage battery of fig. 2 can be directly connected to the external dc system. Due to the fact that the direct current/direct current converter 11 is omitted, the technical scheme of the embodiment of the invention can reduce one-time investment cost and operation loss caused by the direct current/direct current converter in the technical scheme of the figure 1.
As a specific application scenario of the present invention, fig. 3 shows a direct-current side optical storage direct integration system topology, a photovoltaic cell panel 12 is collected by a maximum power point tracking controller 13 of a direct-current combiner box and then connected to a common positive direct-current bus 9 and a common negative direct-current bus 10, positive and negative direct-current buses of a modular multilevel energy storage cell system 1 are correspondingly connected to the common positive direct-current bus 9 and the common negative direct-current bus 10, the common positive direct-current bus 9 and the common negative direct-current bus 10 are further connected to positive and negative electrodes of a photovoltaic inverter 14, and an alternating-current side of the photovoltaic inverter 14 is further connected to an alternating-current power grid through an alternating-current transformer 15. In fig. 3, the outputs of the modular multilevel energy storage battery system 1 and the photovoltaic cell panel 12 are directly collected at the direct current side, so as to form a direct current side light storage and direct integration system.
For comparison, fig. 4 shows an implementation manner of a conventional optical storage dc integrated system, in which a conventional energy storage battery system 21 is connected to a common positive dc bus 9 and a common negative dc bus 10 through a dc/dc converter 11, a photovoltaic cell panel 12 is also connected to the common positive dc bus 9 and the common negative dc bus 10 after collecting dc through a dc combiner box maximum power point tracking controller 13, so that the conventional energy storage battery system 21 and the photovoltaic cell panel 21 form an integrated system on a dc side through a certain dc link, the common positive dc bus 9 and the common negative dc bus 10 are further connected to a dc side of a photovoltaic inverter 14, and an ac side of the photovoltaic inverter 14 is further connected to an ac power grid 16 through an ac transformer 15.
As can be seen from comparing fig. 4 and fig. 3, in the conventional optical storage dc integrated system in fig. 4, the conventional energy storage battery system 21 needs to be connected to the common positive dc bus 9 and the common negative dc bus 10 through the dc/dc converter 11, whereas in the dc-side optical storage dc integrated system in fig. 3 provided by the embodiment of the present invention, the dc side of the modular multilevel energy storage battery system 1 is directly connected to the common positive dc bus 9 and the common negative dc bus 10, and the intermediate link does not need to pass through the dc/dc converter. Because a direct current/direct current converter between an energy storage battery system and a common direct current bus is omitted, the direct current side optical storage direct integration system can greatly save investment cost and operation loss compared with the system in the figure 4.
Fig. 5 shows another embodiment similar to fig. 2, and fig. 5 is substantially identical to fig. 2, except that the output terminals of one or more battery packs in the battery cluster 4 are connected in parallel with the full-bridge module 25, so that the battery pack connected in parallel with the full-bridge module 25 can output a negative level, a zero level or a positive level, thereby expanding the output range of the dc voltage of the battery cluster 4. The positive and negative dc ports of the battery pack 2 are connected to the positive and negative dc ports of the full-bridge module 25, and the output port of the full-bridge module is the output port of the battery pack 3 and is used for connecting with one or more other battery packs 3 in series.
Fig. 6 shows another embodiment similar to fig. 3, and fig. 6 is similar to fig. 3, except that the output terminals of one or more battery packs in the battery cluster 4 are connected in parallel with the full-bridge module 25, so that the battery pack connected in parallel with the full-bridge module 25 can output a negative level, a zero level or a positive level, thereby expanding the output range of the dc voltage of the battery cluster 4.
Fig. 7 shows an implementation of a half-bridge type battery pack, in which a low-voltage terminal (also referred to as an emitter or a drain, depending on the fully-controlled power electronic device used) of a first switch group 31 is connected to a high-voltage terminal (also referred to as a collector or a source, depending on the fully-controlled power electronic device used) of a second switch group 32, a leading-out terminal at a connection point is a first output port of the battery pack 3, a low-voltage terminal of the second switch group 32 is connected to a low-voltage terminal of the battery pack 2, a leading-out terminal at a connection point is a second output port of the battery pack 3, and a high-voltage terminal of the first switch group 31 is connected to a high-voltage terminal of the battery pack 2.
Fig. 8 shows an implementation manner of a full-bridge battery pack, a low-voltage end of the first switch group 33 of the full-bridge module is connected with a high-voltage end of the second switch group 34 of the full-bridge module, a leading-out terminal at a connection point is a first output port of the battery pack 3, a low-voltage end of the third switch group 35 of the full-bridge module is connected with a high-voltage end of the fourth switch group 36 of the full-bridge module, a leading-out terminal at a connection point is a second output port of the battery pack 3, a high-voltage end of the first switch group 33 of the full-bridge module, a high-voltage end of the third switch group 35 of the full-bridge module and a high-voltage end of the battery pack 2 are connected together, a low-voltage end of the second switch group 34 of the full-bridge module, a low-voltage end of the fourth switch group 36 of the full-bridge module and a low-voltage end of the battery pack 2 are connected.
In summary, the present invention provides an energy storage battery dc direct access system, in which the dc side of the energy storage battery is directly connected to the dc bus of the external dc system, thereby eliminating the dc/dc converter embedded between the energy storage battery and the external dc system in the conventional energy storage battery dc access system. The technical scheme provided by the invention has the advantages that:
(1) the investment of the DC/DC converter is saved;
(2) high operation loss caused by the direct current/direct current converter is avoided;
(3) the output voltage of each battery cluster in the energy storage battery system and the output voltage of the battery pack in each battery cluster can be regulated and controlled, so that the power and the energy exchanged between the energy storage battery and an external direct current system are smoothed;
(4) overall, the energy storage dc access system provided by the invention saves investment and operation loss, improves the control performance of the system, and can save the cost of the dc/dc converter of about 750 ten thousand yuan in a conventional energy storage dc access system by taking a 50MW/100MWh energy storage system as an example, and the cost of the energy storage dc direct access system can save the loss of 112.5 ten thousand yuan by taking a 50MW/100MWh energy storage system and 3000 times of cyclic charge and discharge as an example.
Details not described in the present specification belong to the prior art known to those skilled in the art.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the present invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.