Modularized household energy storage system and method for single-cell boost series management

Abstract

The invention discloses a modular household energy storage system for single-cell boost series management, and the system consists of the following components: n cells which are arranged in sequence and are used for energy storage; the n direct-current converters are sequentially arranged and are connected with the n battery cells respectively, every two adjacent direct-current converters are connected, and the direct-current converters are used for boosting the voltage of the battery cells and then are connected in series to form high-voltage direct current so as to realize bidirectional flow from the battery cells to the direct-current bus; and the DC / AC inverter is connected with the battery cells at the head and the tail and is used for converting the high-voltage direct current into alternating current and outputting the alternating current. The invention further discloses a modular household energy storage method for single-cell boost series management. According to the invention, the overall efficiency of the system is improved, equalization management of the batteries is realized through single-cell current control, the problem of capacity loss caused by battery imbalance is effectively solved, and expensive energy storage capacity resources are fully utilized.

Description

Technical Field

[0001] The present invention relates to the field of household energy storage, and particularly to a modular household energy storage system and method for single-cell boost series management. Background Art

[0002] As a branch of the energy storage system, the household energy storage system is characterized by a battery capacity generally within 20 kWh.

[0003] Currently, two main technical routes are mainly adopted: 100Ah large-cell low-voltage 48V system and small-cell high-voltage system. For example, Chinese Patent Application CN 109586339A discloses a hierarchical structure for renewable energy grid-connected power generation. The components of this hierarchical structure include renewable energy, a boost-type DC-DC converter, a DC transmission bus, a backup energy storage device, a buck-type DC-DC converter, a DC-AC inverter, and an AC bus. The boost-type DC-DC converter converts the generated voltage into a high voltage for transmission on the DC transmission line. The buck-type DC-DC converter is used to convert the transmission line voltage into a low voltage for energy storage and grid connection of the distribution network. The DC-AC inverter uses the old distribution network signal as a sample to convert the DC signal into an AC signal. However, the above technical solutions have the following deficiencies: 1. Low efficiency; 2. Considering the battery capacity loss caused by battery inconsistency, battery imbalance will cause some battery capacities not to be fully utilized, wasting expensive energy storage capacity resources. Summary of the Invention

[0004] Object of the Invention: The existing household energy storage systems have problems of low efficiency and capacity loss caused by battery imbalance. To solve the above problems, the present invention provides a modular household energy storage system and method for single-cell boost series management. This system adopts a technical solution in which a single cell is boosted through a DC converter, then connected in series to 400V, and finally inverted into AC through a DC / AC inverter. At the same time, the battery balance problem is achieved through single-cell current control, ensuring that the batteries are fully charged and discharged simultaneously. This technical solution not only eliminates the efficiency loss of a two-way buck-boost converter, but also effectively solves the capacity loss caused by battery imbalance, and the comprehensive discharge efficiency will be increased by 3-5 percentage points.

[0005] Technical Solution: A modular household energy storage system for single-cell boost series management consists of the following components:

[0006] n cells arranged in sequence, and the cells are used for energy storage;

[0007] n DC converters arranged in sequence are respectively connected to n battery cells, and adjacent DC converters are connected. The DC converter is used to boost the voltage of the battery cell and then connect them in series to form high-voltage direct current, so as to achieve bidirectional flow from the battery cell to the DC bus;

[0008] A DC / AC inverter is respectively connected to the battery cell at the head and the battery cell at the tail, and is used to convert the high-voltage direct current into alternating current for output. Wherein, n is a positive integer.

[0009] Further, the battery cell is a lithium-ion battery cell.

[0010] Further, n is 2 to 10.

[0011] Further, the DC converter is an isolated DC converter.

[0012] A modular household energy storage method for single battery cell boost series management adopts the above-mentioned modular household energy storage system for single battery cell boost series management, and the steps are as follows:

[0013] (1) Determine whether the household energy storage system is in a charging state or a discharging state. If the household energy storage system is in a discharging state, go to step (2); if the household energy storage system is in a charging state, go to step (5);

[0014] (2) Set the target voltage of the high-voltage DC side to U dcObj ;

[0015] (3) Sort the n battery cells according to the state of charge SOC 1 、SOC 2 、...、SOC n ;

[0016] (4) Set the voltage target of each DC converter to Then the DC / AC inverter performs inverter discharge according to the discharge target value, where m is a positive integer and 1≤m≤n;

[0017] (5) Set the target voltage of the high-voltage DC side to U dcObj1 ;

[0018] (6) Sort the n battery cells according to the state of charge SOC 1 、SOC 2 、...、SOC n ;

[0019] (7) Set the voltage target of each DC converter to Then the DC / AC inverter performs charging according to the charging target value, where p is a positive integer and 1≤p≤n.

[0020] The innovation of a modular household energy storage system and method for single-cell boost series management disclosed by the present invention lies in:

[0021] In the cell boost link, by controlling the output voltage of a single DC converter, single-cell current control is achieved. By detecting and controlling the charge and discharge current of each cell, the charge balance management between cells is realized, ensuring that all cells are fully charged and discharged simultaneously, and avoiding capacity loss caused by cell imbalance.

[0022] This system adopts a modular design. Each cell and its corresponding DC converter form a module unit. Multiple module units can be connected in series to expand the system capacity. The modular design facilitates the expansion and maintenance of the system, improving the flexibility and reliability of the system.

[0023] In addition, this system reduces the loss of one-stage power conversion, thereby improving the overall efficiency of the system.

[0024] Beneficial effects: Compared with the prior art, a modular household energy storage system and method for single-cell boost series management provided by the present invention have the following beneficial effects:

[0025] 1. It eliminates the one-stage bidirectional boost-buck power conversion link, reduces power conversion loss, and improves the overall efficiency of the system;

[0026] 2. Through single-cell current control, the balance management of the battery is realized, effectively solving the problem of capacity loss caused by battery imbalance, and making full use of the expensive energy storage capacity resources;

[0027] 3. Adopting the design of single-cell boost series simplifies the structure of the battery management unit and the passive balance module, improving the performance and efficiency of the system;

[0028] 4. The single-cell boost series design endows the battery system with good modular characteristics, facilitating expansion and maintenance, and improving the flexibility and reliability of the system;

[0029] 5. The comprehensive discharge efficiency is increased by 3 - 5 percentage points, reducing the system operation cost and improving the economy of the system. Description of the Drawings

[0030] Figure 1 It is a flowchart of a modular household energy storage system for single-cell boost series management disclosed by the present invention. Detailed Embodiment

[0031] The following details the specific embodiments of the present invention.

[0032] The "ranges" disclosed in the present invention are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10 to 50 is listed for a specific parameter, ranges of 10 to 40 and 20 to 50 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations.

[0033] Unless otherwise specified, all embodiments and alternative embodiments of this application can be combined with each other to form new technical solutions.

[0034] Unless otherwise specified, all technical features and alternative technical features of this application can be combined with each other to form new technical solutions.

[0035] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0036] Unless otherwise specified, the "including" and "comprising" mentioned in this application mean open-ended or can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can also mean only the components listed are included or comprised.

[0037] Unless otherwise specified, the reaction is carried out under normal temperature and normal pressure conditions.

[0038] Unless otherwise specified, all parts or percentages are by weight or weight percentage.

[0039] In the present invention, the substances used are all known substances, which can be purchased or synthesized by known methods.

[0040] In the present invention, the devices or equipment used are all conventional devices or equipment known in the field, and can all be purchased.

[0041] As Figure 1 shown, a modular household energy storage system with single-cell boost series management consists of the following components:

[0042] n cells arranged in sequence, which are used for energy storage;

[0043] n DC converters arranged in sequence, which are respectively connected to the n cells, and adjacent two DC converters are connected. The DC converters are used to boost the voltage of the cells, and then form high-voltage direct current in series to achieve bidirectional flow from the cells to the DC bus;

[0044] A DC / AC inverter (rated output power 5kW, output voltage 220V±10%, frequency 50Hz±0.2Hz), which is respectively connected to the first cell and the last cell in the row, and is used to convert the high-voltage direct current into alternating current for output, where n is a positive integer.

[0045] Furthermore, the cell is a lithium-ion battery cell (model LFP, rated capacity 314Ah, rated voltage 3.2V).

[0046] Furthermore, n is 7. In another embodiment, n is 10. In another embodiment, n is 2.

[0047] Furthermore, the DC converter is an isolated DC converter.

[0048] A modular household energy storage method with single-cell boost series management uses the above modular household energy storage system with single-cell boost series management, and the steps are as follows:

[0049] (1). Determine whether the household energy storage system is in a charging state or a discharging state. If the household energy storage system is in a discharging state, go to step (2); if the household energy storage system is in a charging state, go to step (5);

[0050] (2). Set the target voltage of the high-voltage DC side as U dcObj ;

[0051] (3). Sort the n cells according to the state of charge SOC 1 、SOC 2 、...、SOC n ;

[0052] (4) Set the voltage target of each DC converter to Then the DC / AC inverter performs inversion and discharge according to the discharge target value, where m is a positive integer and 1 ≤ m ≤ n;

[0053] (5) Set the target voltage of the high-voltage DC side to U dcObj1 ;

[0054] (6) Sort the n battery cells according to the state of charge SOC 1 、SOC 2 、...、SOC n ;

[0055] (7) Set the voltage target of each DC converter to Then the DC / AC inverter performs charging according to the charging target value, where p is a positive integer and 1 ≤ p ≤ n.

[0056] In the charging mode, the DC / AC inverter converts the AC grid power into high-voltage direct current to charge the battery cells. Each DC converter controls the charging current of the corresponding battery cell according to the detected state of charge of the battery cell to achieve balanced charging of the battery cells;

[0057] In the discharging mode, the battery cells output high-voltage direct current to the DC / AC inverter, and the DC / AC inverter converts it into alternating current for output. Similarly, each DC converter controls the discharging current of the corresponding battery cell according to the detected state of charge of the battery cell to achieve balanced discharging of the battery cells.

[0058] The above has made a detailed description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A modular household energy storage system with single-cell boost and series management, characterized in that: It consists of the following components: n battery cells arranged in sequence, wherein the battery cells are used for energy storage; n DC converters are arranged in sequence, connected to n battery cells respectively, and two adjacent DC converters are connected, the DC converters are used to boost the voltage of the battery cells, and then connect them in series to form high-voltage DC power, so as to achieve bidirectional flow from the battery cells to the DC bus; The DC / AC inverter is connected to the battery cells at the head and the battery cells at the tail, respectively, and is used to convert high-voltage direct current into alternating current output, wherein n is a positive integer.

2. A modular household energy storage system with single-cell boost and series management as claimed in claim 1, characterized in that: The battery cell is a lithium-ion battery cell.

3. A modular household energy storage system with single-cell boost and series management as claimed in claim 1, characterized in that: n is 2 to 10.

4. A modular household energy storage system with single-cell boost and series management as claimed in claim 1, characterized in that: The DC converter is an isolated DC converter.

5. A modular household energy storage method for single-cell boost and series management, using the modular household energy storage system for single-cell boost and series management as claimed in any one of claims 1 to 4, the steps are as follows: (1) Determine whether the household energy storage system is in a charging state or a discharging state. If the household energy storage system is in a discharging state, proceed to step (2); if the household energy storage system is in a charging state, proceed to step (5); (2) Set the target voltage of the high-voltage DC side to U dcObj ; (3) Sort the n cells according to the battery state of charge SOC1, SOC2, ..., SOC n ; (4) Set the voltage target of each DC converter to Then the DC / AC inverter performs inverter discharge according to the discharge target value, where: m is a positive integer, and 1≤m≤n; (5) Set the target voltage of the high-voltage DC side to U dcObj1 ; (6) Sort the n cells according to the battery state of charge SOC1, SOC2, ..., SOC n ; (7) Set the voltage target of each DC converter to The DC / AC inverter then charges according to the charging target value, where p is a positive integer and 1≤p≤n.

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