Energy storage system
By introducing an energy storage converter and DC-DC circuit into the energy storage system, combined with a dual active series resonant converter and controller, the SOC balance problem when battery modules are connected in parallel is solved, improving energy utilization and system flexibility, and adapting to single-phase and three-phase applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-11
- Publication Date
- 2026-03-13
AI Technical Summary
When multiple battery modules are connected in parallel in an energy storage system, there is a state of charge (SOC) balancing problem, which leads to a decrease in circulating current and energy utilization.
The system employs an energy storage converter and multiple DC-DC converters, combined with dual active series resonant converters and a controller, to achieve SOC balancing for each battery module. The charging and discharging are independently controlled by the DC-DC converters, and the DC bus can be connected or disconnected as needed.
It achieves SOC balancing of each battery module, improves energy utilization, enhances system flexibility and safety, reduces the number of BDC circuits, and is adaptable to single-phase and three-phase systems.
Smart Images
Figure CN121663718A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power electronics technology, specifically to an energy storage system. Background Technology
[0002] Currently, energy storage systems are being used more and more widely. As the capacity of energy storage systems increases, the number of battery cells in battery modules is also increasing. Furthermore, energy storage systems may include multiple battery modules connected in parallel. There is a need to balance the remaining state of charge (SOC) among the parallel battery modules; otherwise, circulating currents can easily occur between the parallel battery modules.
[0003] Currently, many battery modules achieve SOC balance through passive resistor balancing, which results in a significant "weakest link" effect and reduces the energy utilization rate of the energy storage system. Summary of the Invention
[0004] In view of this, this application provides an energy storage system that can balance the SOC of each battery module and improve the energy utilization rate.
[0005] This application provides an energy storage system, including: an energy storage converter and multiple DC-DC converters; the energy storage converter includes a bidirectional DC-DC converter, an inverter circuit, and a boost circuit; the first terminal of each DC-DC converter is connected to a corresponding battery module; the second terminal of each DC-DC converter is connected to a DC bus; the first terminal of the BDC converter is connected to the DC bus, and the second terminal of the BDC converter is connected to the first terminal of the inverter circuit, the second terminal of the inverter circuit being used to connect to at least one of the power grid or a load; the second terminal of the BDC converter is connected to the first terminal of the boost circuit, the second terminal of the boost circuit being used to connect to a photovoltaic panel.
[0006] One possible implementation further includes: a switching circuit; the DC-DC circuit includes a first dual active series resonant converter and a second dual active series resonant converter; the first terminals of the first dual active series resonant converter and the second dual active series resonant converter are both connected to the same battery module; the second terminals of the first dual active series resonant converter and the second dual active series resonant converter are connected together in series or in parallel through the switching circuit and then connected to the DC bus.
[0007] In one possible implementation, the DC-DC circuit includes a switching circuit, a first dual active series resonant converter, and a second dual active series resonant converter; the first terminals of the first dual active series resonant converter and the second dual active series resonant converter are both connected to the same battery module; the second terminals of the first dual active series resonant converter and the second dual active series resonant converter are connected in series or in parallel to the DC bus through the switching circuit.
[0008] One possible implementation further includes: a controller; the switching circuit includes: a first switch, a second switch, and a third switch; the two ends of the first switch are respectively connected to the positive terminal of the second terminal of the first dual active series resonant converter and the negative terminal of the second terminal of the second dual active series resonant converter; the first end and the second end of the second switch are respectively connected to the negative terminal of the second terminal of the first dual active series resonant converter and the negative terminal of the second terminal of the second dual active series resonant converter; the first end and the second end of the third switch are respectively connected to the positive terminal of the second terminal of the first dual active series resonant converter and the positive terminal of the second terminal of the second dual active series resonant converter; the controller is used to control the first switch to close, and the second switch and the third switch to open, so that the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in series; it is also used to control the first switch to open, and the second switch and the third switch to close, so that the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in parallel.
[0009] In one possible implementation, the first dual active series resonant converter includes a first primary-side full-bridge circuit, a first LC resonant circuit, and a first secondary-side full-bridge circuit; the second dual active series resonant converter includes a second primary-side full-bridge circuit, a second LC resonant circuit, and a second secondary-side full-bridge circuit; the first primary-side full-bridge circuit is connected to the primary winding of the first transformer via the first LC resonant circuit, and the first terminal of the first secondary-side full-bridge circuit is connected to the secondary winding of the first transformer; the second primary-side full-bridge circuit is connected to the primary winding of the second transformer via the second LC resonant circuit, and the first terminal of the second secondary-side full-bridge circuit is connected to the secondary winding of the second transformer; the second terminals of both the first and second secondary-side full-bridge circuits are connected to the same battery module.
[0010] In one possible implementation, the first dual active series resonant converter and the second dual active series resonant converter share the same secondary-side full-bridge circuit; the primary-side full-bridge circuit of the first dual active series resonant converter is connected to the first primary winding of the transformer through a first resonant circuit, and the primary-side full-bridge circuit of the second dual active series resonant converter is connected to the second primary winding of the transformer through a second resonant circuit; the first end of the secondary-side full-bridge circuit is connected to the secondary winding of the transformer, and the second end of the secondary-side full-bridge circuit is connected to the corresponding battery module.
[0011] In one possible implementation, the controller is further configured to control the first current at the second terminal of the first dual active series resonant converter and the second current at the second terminal of the second dual active series resonant converter to be consistent when the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in series.
[0012] In one possible implementation, the controller is further configured to control the first voltage at the second terminal of the first dual active series resonant converter and the second voltage at the second terminal of the second dual active series resonant converter to be consistent when the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in parallel.
[0013] One possible implementation is that when the energy storage system is a single-phase system, the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in parallel; when the energy storage system is a three-phase system, the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in series.
[0014] One possible implementation further includes: a battery management system (BMS); each DC-DC circuit corresponds to one BMS; the BMS communicates with the controller in the corresponding DC-DC circuit and sends control commands to the controller; the controller is used to control the first dual active series resonant converter and the second dual active series resonant converter according to the control commands to perform residual power balancing of the corresponding battery modules, add the corresponding battery modules or cut off at least one of the corresponding battery modules.
[0015] In one possible implementation, the controller is further configured to adjust the inner phase shift angle of the first dual active series resonant converter and the inner phase shift angle of the second dual active series resonant converter to enable soft switching of the primary and secondary circuits; it is also configured to adjust the outer phase shift angle between the first dual active series resonant converter and the second dual active series resonant converter to charge or discharge the battery module.
[0016] One possible implementation is that the BDC circuit is a bidirectional Buck-Boost circuit.
[0017] In one possible implementation, the energy storage converter includes a controller and a BDC circuit, which are configured to receive current dispatch instructions sent by the controller and control the current at the second terminal of the BDC circuit according to the current dispatch instructions; the controller is also configured to send current dispatch instructions to the BMS corresponding to each DC-DC circuit, and the BMS controls the current at the second terminal of each DC-DC circuit according to the current dispatch instructions.
[0018] The energy storage system provided in this application embodiment has a BDC circuit in the energy storage converter directly connected to the DC bus. Battery modules are connected to the DC bus via DC-DC circuits. Each battery module can be controlled for charging or discharging via an independent DC-DC circuit, enabling SOC balancing among the battery modules. Each DC-DC circuit operates independently. When the energy storage system requires higher power, it can be connected to the DC bus; when lower power is needed, or in case of battery module or DC-DC circuit failure, the DC-DC circuit can be disconnected from the DC bus, providing flexible application options. Furthermore, the energy storage system provided in this application embodiment includes only one BDC circuit in the energy storage converter. One BDC circuit can power multiple DC-DC circuits, saving on the number of BDC circuits required. The energy storage converter can centrally control both the BDC circuit and the inverter circuit. Attached Figure Description
[0019] Figure 1 A schematic diagram of an energy storage system provided in an embodiment of this application;
[0020] Figure 2A A schematic diagram of a BDC circuit provided in an embodiment of this application;
[0021] Figure 2B A schematic diagram of a DC-DC circuit provided in an embodiment of this application;
[0022] Figure 3 A circuit diagram of a dual active series resonant converter provided in this application embodiment;
[0023] Figure 4 A schematic diagram of another DC-DC circuit provided in an embodiment of this application;
[0024] Figure 5 This is a schematic diagram of another DC-DC circuit provided in an embodiment of this application. Detailed Implementation
[0025] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0026] See Figure 1 The figure is a schematic diagram of an energy storage system provided in an embodiment of this application.
[0027] The energy storage system provided in this application embodiment includes: an energy storage converter 100 and a plurality of DC-DC converter circuits; the energy storage converter 100 includes a bidirectional DC-DC converter circuit 11, an inverter circuit 12 and a boost circuit 13.
[0028] The first terminal of each DC-DC circuit is connected to the corresponding battery module; that is, each battery module has its own corresponding DC-DC circuit, which can control the charging and discharging of the corresponding battery module. The second terminal of each DC-DC circuit is connected to the DC bus BUS, that is, all DC-DC circuits can be connected in parallel to the DC bus BUS and connected to the energy storage converter 100 through the DC bus BUS.
[0029] The energy storage converter 100 can be single-phase or three-phase, and can be directly adapted to the voltage of the energy storage converter in either a three-phase or single-phase energy storage system. The input voltage of the three-phase energy storage converter is higher than that of the single-phase energy storage converter. In the energy storage system provided in this embodiment, the addition of a DC-DC circuit allows for voltage boosting, thereby enabling a wider output voltage range for the battery module.
[0030] The energy storage system provided in this application embodiment includes a battery pack comprising a battery module and a DC-DC circuit. Each battery module can be connected in parallel after being boosted by the DC-DC circuit, i.e., all are connected to the DC bus. The parallel connection of multiple battery packs can be referred to as a battery cluster, and the energy storage system also supports the parallel connection of multiple battery clusters, thereby increasing the energy storage capacity of the energy storage system.
[0031] The embodiments of this application do not specifically limit the internal structure of the BDC circuit 11, as long as bidirectional energy transmission can be achieved.
[0032] For example, a BDC circuit can use a bidirectional Buck-Boost circuit, which is a commonly used topology. For details, please refer to [link to relevant documentation]. Figure 2A As shown, the specific structure will not be described in detail here.
[0033] The bidirectional Buck-Boost circuit can achieve the purpose of bidirectional power transmission with secondary voltage regulation.
[0034] In this embodiment, the DC bus voltage Vbus is controlled using closed-loop control. This allows the DC bus voltage Vbus to be kept within a range that the bidirectional Buck-Boost circuit can adjust, thus reducing the voltage adjustment pressure on the bidirectional Buck-Boost circuit. In other words, in the energy storage system provided in this embodiment, the voltage ratio between Vbus and the battery cluster can be adjusted as needed, and is not fixed.
[0035] For the control of the BDC circuit, the energy storage converter includes a controller, which can control the BDC circuit, inverter circuit, and boost circuit inside the energy storage converter. Specifically, the BDC circuit is used to receive current dispatch commands sent by the controller and control the current at the second terminal of the BDC circuit according to the current dispatch commands.
[0036] Since the current at the first terminal of the BDC circuit is the current on the BUS, i.e., the DC bus current, and the DC bus current is the sum of the currents at the second terminals of each DCDC circuit, the controller is also used to send current dispatch commands to the BMS corresponding to each DCDC circuit. The BMS controls the current at the second terminal of each DCDC circuit according to the current dispatch commands.
[0037] For example, an energy storage system includes n DC-DC circuits, corresponding to n battery modules. The first DC-DC circuit 21 is connected to the first battery module, the second DC-DC circuit 22 is connected to the second battery module, and so on, up to the nth DC-DC circuit 2n connected to the nth battery module. n is an integer greater than or equal to 2.
[0038] The first terminal of BDC circuit 11 is connected to the DC bus BUS, and the second terminal of BDC circuit 11 is connected to the first terminal of inverter circuit 12. The second terminal of inverter circuit 12 is used to connect to at least one of grid or load. The first terminal of BDC circuit 11 is connected to the first terminal of boost circuit 13, and the second terminal of boost circuit 13 is used to connect to photovoltaic panel PV. It should be understood that this application does not specifically limit the number of photovoltaic panels.
[0039] It should be understood that multiple battery modules and multiple DC-DC circuits can be located inside the battery cluster. The interface of the battery cluster is directly connected to the DC bus. The DC bus can connect multiple battery clusters or a single battery cluster; this application does not impose specific limitations. Moreover, the energy storage system provided in this application is a photovoltaic-energy storage system, which can be applied to residential photovoltaic-energy storage scenarios as well as industrial and commercial photovoltaic-energy storage scenarios.
[0040] The energy stored in the battery module can be converted by a DC-DC circuit and an energy storage converter and then fed into the grid or used to power off-grid loads. Alternatively, excess energy from the grid or photovoltaic panels can be converted by an energy storage converter and a DC-DC circuit and stored in the battery module.
[0041] The energy storage system provided in this application embodiment has a BDC circuit in the energy storage converter directly connected to the DC bus. Battery modules are connected to the DC bus via DC-DC circuits. Each battery module can be controlled for charging or discharging via an independent DC-DC circuit, enabling SOC balancing among the battery modules. Each DC-DC circuit operates independently. When the energy storage system requires higher power, it can be connected to the DC bus; when lower power is needed, or in case of battery module or DC-DC circuit failure, the DC-DC circuit can be disconnected from the DC bus, providing flexible application options. Furthermore, the energy storage system provided in this application embodiment includes only one BDC circuit in the energy storage converter. One BDC circuit can power multiple DC-DC circuits, saving on the number of BDC circuits required. The energy storage converter can centrally control both the BDC circuit and the inverter circuit.
[0042] Since each battery module has a corresponding DC-DC circuit, battery modules with lower voltage levels can be used, i.e., low-voltage batteries can be utilized.
[0043] The energy storage system provided in this application embodiment does not specifically limit whether the switching circuit is located inside or outside the DC-DC circuit. One possible implementation is that the switching circuit is independently set outside the DC-DC circuit. That is, the energy storage system also includes: a switching circuit; the DC-DC circuit includes a first dual active series resonant converter and a second dual active series resonant converter; the first terminal of the first dual active series resonant converter and the first terminal of the second dual active series resonant converter are both connected to the same battery module; the second terminal of the first dual active series resonant converter and the second terminal of the second dual active series resonant converter are connected together in series or in parallel through the switching circuit and then connected to the DC bus.
[0044] The following describes, with reference to the accompanying drawings, the implementation method of the energy storage system provided in the embodiments of this application, in which the switching circuit is located inside the DCDC circuit.
[0045] For ease of understanding, the implementation of the DCDC circuit in the energy storage system provided in this application is described below with reference to the accompanying drawings.
[0046] See Figure 2B The figure is a schematic diagram of a DC-DC circuit provided in an embodiment of this application.
[0047] The energy storage system provided in this application embodiment includes a DC-DC circuit comprising a switching circuit 213, a first dual active series resonant converter 211, and a second dual active series resonant converter 212.
[0048] The first terminal of the first dual active series resonant converter 211 and the first terminal of the second dual active series resonant converter 212 are both connected to the same battery module. The battery module can expand its application scenarios through DC-DC circuits, and the voltage level can be applied to single-phase energy storage converters or three-phase energy storage converters.
[0049] The second terminals of the first dual active series resonant converter 211 and the second terminals of the second dual active series resonant converter 212 are connected in series or in parallel through the switching circuit 213. After being connected in series or in parallel, they are connected to the DC bus BUS.
[0050] A dual active series resonant converter includes a primary-side full-bridge circuit, a resonant circuit, a transformer, and a secondary-side full-bridge circuit. Since both the primary-side and secondary-side full-bridge circuits include switching transistors, bidirectional energy transfer can be achieved by controlling these transistors, thereby enabling battery charging or discharging.
[0051] The following is combined Figure 3 This application describes a specific implementation of the dual active series resonant converter provided in its embodiments.
[0052] See Figure 3 The figure is a circuit diagram of a dual active series resonant converter provided in an embodiment of this application.
[0053] The dual active series resonant converter includes a primary-side full-bridge circuit, a resonant circuit, and a secondary-side full-bridge circuit. The primary-side full-bridge circuit includes four switching transistors (S1-S4) and body diodes (D1-D4). The resonant circuit includes a series inductor L. r and capacitor C r The secondary-side full-bridge circuit includes four switching transistors, S5-S8, and body diodes, D5-D8, for each transistor.
[0054] A typical DC bus includes a positive DC bus and a negative DC bus. The first and second input terminals of the primary-side full-bridge circuit are connected to the positive and negative DC buses, respectively. (V in the diagram...) bus This is merely an illustration of the DC bus voltage. Since energy can flow bidirectionally, the input and output terminals in this embodiment are relative concepts. Figure 3 The description is only used as an example of energy transfer from the DC bus to the battery.
[0055] The first output terminal A of the primary-side full-bridge circuit is connected to the first terminal of the primary winding of transformer T1 via a resonant circuit. The second output terminal B of the primary-side full-bridge circuit is connected to the second terminal of the primary winding of transformer T1. The turns ratio of the primary and secondary windings of transformer T1 is n. The voltage between points A and B is V. AB The voltage between points C and D is V.CD .
[0056] The first input terminal C of the secondary-side full-bridge circuit is connected to the first end of the secondary winding of transformer T1 via a resonant circuit, and the second input terminal D of the secondary-side full-bridge circuit is connected to the second end of the secondary winding of transformer T1. The positive and negative output terminals of the secondary-side full-bridge circuit are connected to the two ends of the battery module, respectively, and the voltage of the battery module is represented by Vbat.
[0057] The dual active series resonant converter provided in this application embodiment operates with all switches in both the primary and secondary full-bridge circuits alternating at a 50% duty cycle, and has a necessary dead time. For ease of description, three phase shift angles are defined below: the phase difference between the drive signals S1 and S4 in the primary full-bridge circuit is defined as the primary-side internal phase shift angle α1; the phase difference between the drive signals S5 and S8 in the secondary full-bridge circuit is defined as the secondary-side internal phase shift angle α2; and the voltage V between the midpoints of the primary bridge arms is defined as... AB Voltage V between the midpoint of the secondary bridge arm and the secondary side bridge arm CD The phase difference between them is defined as the outward phase shift angle θ. Specifically, the voltage V between the midpoints of the primary side bridge arms is... AB The voltage V between half of the high level and the midpoint of the secondary bridge arm CD The phase difference between the two halves of the high level is defined as the outward phase angle θ.
[0058] The dual active series resonant converter provided in this application embodiment can achieve bidirectional power flow by adjusting the sign of the outer phase shift angle θ. By adjusting the inner phase shift angle α1 of the primary side and the inner phase shift angle α2 of the secondary side, the minimum resonant current and soft switching of the switching transistor can be achieved, thereby improving the overall power conversion efficiency of the dual active series resonant converter.
[0059] The energy storage system provided in this application embodiment is applicable to both single-phase and three-phase systems. It should be understood that single-phase and three-phase systems refer to the number of phases of the power grid connected to the AC side of the energy storage converter. Correspondingly, when the power grid is single-phase, the energy storage converter is a single-phase energy storage converter; when the power grid is three-phase, the energy storage converter is a three-phase energy storage converter. The DC-DC circuit includes two dual active series resonant converters. The second terminals of the two dual active series resonant converters can be selected to be connected in parallel or in series depending on the application scenario.
[0060] When the energy storage system is a single-phase system, the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in parallel; when the energy storage system is a three-phase system, the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in series.
[0061] The DC-DC circuit provided in this application includes two dual active series resonant converters. The secondary full-bridge circuits of the two dual active series resonant converters can be shared, meaning only one transformer is needed, consisting of two primary windings and one secondary winding. Alternatively, two independent transformers can be included, with each dual active series resonant converter comprising an independent primary-side full-bridge circuit and a secondary-side full-bridge circuit. The implementation of the independent transformers for the two dual active series resonant converters will be described below with reference to the accompanying drawings.
[0062] See Figure 4 The figure is a schematic diagram of another DC-DC circuit provided in an embodiment of this application.
[0063] The energy storage system provided in this application embodiment includes a first dual active series resonant converter comprising a first primary-side full-bridge circuit (S1-S4), a first LC resonant circuit, and a first secondary-side full-bridge circuit (S5-S8); and a second dual active series resonant converter comprising a second primary-side full-bridge circuit (Q1-Q4), a second LC resonant circuit, and a second secondary-side full-bridge circuit (Q5-Q8).
[0064] The first primary-side full-bridge circuit is connected to the primary winding of the first transformer T1 through the first LC resonant circuit, and the first end of the first secondary-side full-bridge circuit is connected to the secondary winding of the first transformer.
[0065] The second primary-side full-bridge circuit is connected to the primary winding of the second transformer T2 through the second LC resonant circuit, and the first end of the second secondary-side full-bridge circuit is connected to the secondary winding of the second transformer.
[0066] The second terminal of the first secondary full-bridge circuit and the second terminal of the second secondary full-bridge circuit are both connected to the same battery module.
[0067] The input voltage of the first primary-side full-bridge circuit is V. bus1 The input voltage of the second primary-side full-bridge circuit is V. bus2 The voltage between the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter connected in series and parallel is V. bus .
[0068] The output current of the first secondary full-bridge circuit is I. bat1 The output current of the second secondary full-bridge circuit is I. bat2 It should be understood that, since the output terminals of both the first and second secondary full-bridge circuits are connected in parallel to the battery V... bat Therefore, I needs to be controlled at both ends. bat1 with I bat2 equal.
[0069] The energy storage system provided in this application embodiment further includes: a controller (not shown in the figure); the switching circuit includes: a first switch K1, a second switch K2 and a third switch K3.
[0070] The two ends of the first switch K1 are respectively connected to the positive terminal of the second end of the first dual active series resonant converter and the negative terminal of the second end of the second dual active series resonant converter.
[0071] The first and second terminals of the second switch K2 are respectively connected to the negative terminal of the second terminal of the first dual active series resonant converter and the negative terminal of the second terminal of the second dual active series resonant converter.
[0072] The first and second terminals of the third switch K3 are respectively connected to the positive terminal of the second terminal of the first dual active series resonant converter and the positive terminal of the second terminal of the second dual active series resonant converter.
[0073] The controller is used to control the first switch K1 to close and the second switch K2 and the third switch K3 to open, so that the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in series; it is also used to control the first switch K1 to open and the second switch K2 and the third switch K3 to close, so that the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in parallel.
[0074] The controller is also used to ensure that, when the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in series, the first current at the second terminal of the first dual active series resonant converter and the second current at the second terminal of the second dual active series resonant converter are consistent. It should be understood that consistency between the two currents means that the difference between the two currents is within a preset range, i.e., within the allowable error range, which is considered as proper adjustment.
[0075] The controller is also configured to, when the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in parallel, control the first voltage at the second terminal of the first dual active series resonant converter and the second voltage at the second terminal of the second dual active series resonant converter to be consistent, i.e., V bus1 and V bus2 Consistency. It should be understood that consistency between the two voltages means that the difference between the two voltages is within the preset range, that is, within the allowable error range, which is considered to indicate that the adjustment is in place.
[0076] In the energy storage system provided in this application embodiment, the second end of the DC-DC circuit is generally the high-voltage side. The high-voltage side connects the two primary-side full-bridge circuits in series or in parallel through K1, K2, and K3 (switches or relays), while the two secondary-side full-bridge circuits are directly connected in parallel.
[0077] When K1 is off and K2 and K3 are closed, the high-voltage side is in parallel mode, and the high-voltage side voltage V bus =V bus1 =V bus2， By adjusting the two independent inner and outer phase shift angles, the effect of parallel current sharing can be achieved, making I bat1 =I bat2 .
[0078] When K1 is closed and K2 and K3 are closed, the high-voltage side is in series mode. By adjusting the two independent inner and outer phase shift angles, the effect of series voltage equalization can be achieved, thus increasing the high-voltage side voltage V. bus =2V bus1 =2V bus2 This expands the voltage range of the high-voltage side, meaning it can be applied to situations with high DC bus voltage, such as three-phase energy storage systems.
[0079] Figure 4 The introduced DC-DC circuit includes two independent dual active series resonant converters, each with its own independent primary-side full-bridge circuit and secondary-side full-bridge circuit. The following describes how the two dual active series resonant converters share the secondary-side full-bridge circuit. The transformer can be magnetically integrated. Figure 4 The primary winding of the first transformer T1 and the secondary winding of the second transformer T2 share a single magnetic core. The secondary winding is connected to the secondary full-bridge circuit. Figure 4 In the full-bridge circuit on the central side, each switching transistor can be one or more connected in parallel; in the full-bridge circuit on the secondary side, each switching transistor can be one or more connected in parallel.
[0080] See Figure 5 The figure is a schematic diagram of another DC-DC circuit provided in an embodiment of this application.
[0081] The DC-DC circuit provided in this application embodiment uses the same secondary full-bridge circuit for the first dual active series resonant converter and the second dual active series resonant converter.
[0082] The primary-side full-bridge circuit of the first dual active series resonant converter is connected to the first primary winding of the transformer T through the first resonant circuit, and the primary-side full-bridge circuit of the second dual active series resonant converter is connected to the second primary winding of the transformer through the second resonant circuit.
[0083] The first end of the secondary full-bridge circuit is connected to the secondary winding of transformer T, and the second end of the secondary full-bridge circuit is connected to the corresponding battery module.
[0084] Figure 5 The DCDC circuit shown is Figure 4 The difference between the DCDC circuits shown is that... Figure 5The two dual active series resonant converters shown share the same secondary full-bridge circuit; the remaining connections are the same as... Figure 4 The same applies, so I won't repeat it here.
[0085] The energy storage system provided in this application embodiment configures a DC-DC circuit for each battery pack, enabling better one-pack-one-maintenance. Each battery pack includes a Battery Management System (BMS), which is primarily responsible for battery detection, evaluation, and protection. The BMS can send control commands to the DC-DC circuit based on battery information, achieving SOC (State of Charge) balancing among the battery packs within the battery cluster. Furthermore, the BMS in this application embodiment can also control the switching on and off of the DC-DC circuit and the addition of battery packs, allowing for the connection or disconnection of the DC-DC circuit with the corresponding battery module. This improves the flexibility, safety, and cycle life of the energy storage system.
[0086] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. An energy storage system, characterized in that, include: The energy storage converter and multiple DC-DC converter circuits; the energy storage converter includes a bidirectional DC-DC circuit, an inverter circuit, and a boost circuit. The first terminal of each DC-DC circuit is connected to the corresponding battery module; the second terminal of each DC-DC circuit is connected to the DC bus. The first terminal of the BDC circuit is connected to the DC bus, and the second terminal of the BDC circuit is connected to the first terminal of the inverter circuit. The second terminal of the inverter circuit is used to connect to at least one of the power grid or the load. The second terminal of the BDC circuit is connected to the first terminal of the boost circuit. The second terminal of the boost circuit is used to connect to the photovoltaic panel.
2. The energy storage system according to claim 1, characterized in that, Also includes: Switching circuit; The DC-DC circuit includes a first dual active series resonant converter and a second dual active series resonant converter; the first terminals of the first dual active series resonant converter and the first terminals of the second dual active series resonant converter are both connected to the same battery module. The second terminals of the first dual active series resonant converter and the second dual active series resonant converter are connected in series or in parallel through the switching circuit and then connected to the DC bus.
3. The energy storage system according to claim 1, characterized in that, The DC-DC circuit includes a switching circuit, a first dual active series resonant converter, and a second dual active series resonant converter. The first terminal of the first dual active series resonant converter and the first terminal of the second dual active series resonant converter are both connected to the same battery module; The second terminals of the first dual active series resonant converter and the second dual active series resonant converter are connected in series or in parallel to the DC bus through the switching circuit.
4. The energy storage system according to claim 2 or 3, characterized in that, Also includes: Controller; The switching circuit includes: a first switch, a second switch, and a third switch; The two ends of the first switch are respectively connected to the positive terminal of the second end of the first dual active series resonant converter and the negative terminal of the second end of the second dual active series resonant converter; The first and second terminals of the second switch are respectively connected to the negative terminal of the second terminal of the first dual active series resonant converter and the negative terminal of the second terminal of the second dual active series resonant converter. The first and second terminals of the third switch are respectively connected to the positive terminal of the second terminal of the first dual active series resonant converter and the positive terminal of the second terminal of the second dual active series resonant converter. The controller is configured to control the first switch to close, and the second and third switches to open, so that the second terminals of the first dual active series resonant converter and the second dual active series resonant converter are connected in series; it is also configured to control the first switch to open, and the second and third switches to close, so that the second terminals of the first dual active series resonant converter and the second dual active series resonant converter are connected in parallel.
5. The energy storage system according to claim 4, characterized in that, The first dual active series resonant converter includes a first primary-side full-bridge circuit, a first LC resonant circuit, and a first secondary-side full-bridge circuit; the second dual active series resonant converter includes a second primary-side full-bridge circuit, a second LC resonant circuit, and a second secondary-side full-bridge circuit. The first primary-side full-bridge circuit is connected to the primary winding of the first transformer through the first LC resonant circuit, and the first end of the first secondary-side full-bridge circuit is connected to the secondary winding of the first transformer. The second primary-side full-bridge circuit is connected to the primary winding of the second transformer through the second LC resonant circuit, and the first end of the second secondary-side full-bridge circuit is connected to the secondary winding of the second transformer. The second terminal of the first secondary full-bridge circuit and the second terminal of the second secondary full-bridge circuit are both connected to the same battery module.
6. The energy storage system according to claim 4, characterized in that, The first dual active series resonant converter and the second dual active series resonant converter share the same secondary full-bridge circuit; The primary-side full-bridge circuit of the first dual active series resonant converter is connected to the first primary winding of the transformer through the first resonant circuit, and the primary-side full-bridge circuit of the second dual active series resonant converter is connected to the second primary winding of the transformer through the second resonant circuit. The first end of the secondary-side full-bridge circuit is connected to the secondary winding of the transformer, and the second end of the secondary-side full-bridge circuit is connected to the corresponding battery module.
7. The energy storage system according to any one of claims 3-6, characterized in that, The controller is further configured to control the first current at the second end of the first dual active series resonant converter and the second current at the second end of the second dual active series resonant converter to be consistent when the second end of the first dual active series resonant converter and the second end of the second dual active series resonant converter are connected in series.
8. The energy storage system according to any one of claims 3-6, characterized in that, The controller is further configured to control the first voltage at the second terminal of the first dual active series resonant converter and the second voltage at the second terminal of the second dual active series resonant converter to be consistent when the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in parallel.
9. The energy storage system according to any one of claims 2-8, characterized in that, When the energy storage system is a single-phase system, the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in parallel; when the energy storage system is a three-phase system, the second terminals of the first dual active series resonant converter and the second terminals of the second dual active series resonant converter are connected in series.
10. The energy storage system according to any one of claims 3-6, characterized in that, Also includes: Battery Management System (BMS); each DC-DC circuit corresponds to one BMS; The BMS communicates with the controller in the corresponding DC-DC circuit and sends control commands to the controller. The controller is used to control the first dual active series resonant converter and the second dual active series resonant converter according to the control commands to balance the remaining power of the corresponding battery module, add the corresponding battery module or cut off at least one of the corresponding battery modules.
11. The energy storage system according to any one of claims 4-8, characterized in that, The controller is also used to adjust the inner phase shift angle of the first dual active series resonant converter and the inner phase shift angle of the second dual active series resonant converter to enable soft switching of the primary circuit and the secondary circuit; it is also used to adjust the outer phase shift angle between the first dual active series resonant converter and the second dual active series resonant converter to charge or discharge the battery module.
12. The energy storage system according to any one of claims 1-3, characterized in that, The BDC circuit is a bidirectional Buck-Boost circuit.
13. The energy storage system according to claim 12, characterized in that, The energy storage converter includes a controller and a BDC circuit, which is used to receive current dispatch instructions sent by the controller and control the current at the second terminal of the BDC circuit according to the current dispatch instructions. The controller is also configured to send a current scheduling instruction to the BMS corresponding to each DC-DC circuit, and the BMS controls the current at the second terminal of each DC-DC circuit according to the current scheduling instruction.