Sodium ion battery energy storage system control method

Abstract

The invention discloses a sodium ion battery energy storage system control method, which is mainly characterized in that a bidirectional DC / DC converter and a change-over switch branch circuit are additionally arranged between a sodium ion battery cluster and a PCS converter, the bidirectional DC / DC converter and the change-over switch branch circuit are arranged in parallel, the change-over switch branch circuit comprises a main contactor and a switching soft start, and the main contactor is connected with the change-over switch branch circuit. The two-way DC / DC converter has two modes, namely a buck mode and a boost mode, and the PCS converter can control the working state of the change-over switch branch. The bidirectional DC / DC converter and the change-over switch branch are additionally arranged between the sodium ion battery cluster and the PCS converter, low-end voltage is converted, the voltage of the battery end is widened to the direct-current voltage range of the PCS converter, the battery can be used in the full-voltage range, and resource waste is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a sodium ion battery energy storage system control method. Background Art

[0002] At present, the battery energy storage market is mainly dominated by lithium iron phosphate batteries. With the vigorous development of lithium-ion batteries, the scarcity of lithium resources has attracted more and more attention from the industry. The content of lithium resources in the earth's crust is only 0.0065%, and 75% is distributed in South America. In the subsequent energy storage market, sodium-ion batteries, which have a resource content of more than 400 times that of lithium, are highly expected. It is estimated that the material cost of sodium-ion batteries is 30%-40% lower than that of lithium-ion batteries. In addition, due to the stable chemical properties of sodium batteries, it is not easy to form hard dendrites like lithium dendrites, and it has advantages in safety over similar lithium-ion battery systems.

[0003] Due to the characteristics of sodium-ion batteries, the nominal voltage of a single cell is 3.0V, and the operating voltage range is 1.5V-3.95V; while the nominal voltage of conventional lithium iron phosphate batteries is 3.2V, and the operating voltage range is 2V-3.65V. After PACK is grouped, the total voltage of the sodium-ion battery energy storage system exceeds the operating voltage range of the PCS converter, resulting in the inability to release all energy, causing a waste of resources.

[0004] To this end, the present invention provides a sodium ion battery energy storage system control method to solve the above problems. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a sodium ion battery energy storage system control method to solve the above problems.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A sodium ion battery energy storage system control method, comprising the following steps: Step 1: adding a bidirectional DC / DC converter and a switching switch branch between the sodium ion battery cluster and the PCS converter, wherein the bidirectional DC / DC converter and the switching switch branch are arranged in parallel, and the switching switch branch includes a main contactor and a switching soft starter; Step 2: When the PCS converter is charging the sodium-ion battery cluster, the PCS converter monitors the voltage of the sodium-ion battery in real time. When the voltage of the sodium-ion battery cluster is less than or equal to the minimum voltage of the PCS converter, the PCS converter cannot directly charge the sodium-ion battery cluster, and the switch branch is disconnected. The PCS converter communicates with the bidirectional DC / DC converter in real time to match the voltage. The PCS converter outputs the corresponding DC high-voltage side voltage, and the bidirectional DC / DC converter outputs the matching low-voltage side voltage according to the sodium-ion battery cluster voltage. Step 3: When the sodium-ion battery cluster is discharging to the outside, the PCS converter monitors the voltage of the sodium-ion battery cluster in real time. When it detects that the voltage of the sodium-ion battery cluster is less than or equal to the minimum voltage of the PCS converter, the PCS converter cannot discharge directly to the outside, and the switch branch is disconnected. The PCS converter communicates with the bidirectional DC / DC converter in real time to match the voltage. The bidirectional DC / DC converter outputs the corresponding DC high-voltage side voltage according to the requirements of the PCS converter.

[0007] Preferably, the DC low-voltage side voltage range of the bidirectional DC / DC converter is 150V-1000V, and the DC high-voltage side voltage range is 350V-1000V, which meets the bidirectional direct energy flow between low voltage and high voltage. The DC low-voltage side of the bidirectional DC / DC converter is the battery terminal voltage, and the DC high-voltage side voltage can be controlled by the PCS converter according to demand.

[0008] Preferably, the conventional DC side voltage range of the PCS converter is 600V-1000V.

[0009] Preferably, the sodium ion battery cluster is grouped by a plurality of sodium ion battery monomers PACK, and the operating voltage range of the sodium ion battery cluster is 288V-758.4V.

[0010] Preferably, the PCS converter sends a message signal for controlling the switching switch branch to the battery management system BMS through CAN communication, thereby controlling the working state of the switching switch branch. Beneficial Effects

[0011] The present invention provides a sodium ion battery energy storage system control method. Compared with the prior art, it has the following beneficial effects: The present invention converts the low-end voltage by adding a bidirectional DC / DC converter and a switching switch branch between the sodium ion battery cluster and the PCS converter, widens the battery terminal voltage to the DC voltage range of the PCS converter, realizes the use of the full voltage range of the battery, and avoids resource waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the overall flow chart of the present invention; Figure 2 is a circuit block diagram of a bidirectional DC / DC converter of the present invention; Figure 3 It is a block diagram of the working principle of the bidirectional DC / DC converter of the present invention. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0014] See also Figure 1-3 , a sodium ion battery energy storage system control method, comprising the following steps: Step 1: Add a bidirectional DC / DC converter and a switching switch branch between the sodium ion battery cluster and the PCS converter. The bidirectional DC / DC converter and the switching switch branch are connected in parallel. The switching switch branch includes a main contactor and a switching soft starter. Step 2: When the PCS converter is charging the sodium-ion battery cluster, the PCS converter monitors the voltage of the sodium-ion battery in real time. When the voltage of the sodium-ion battery cluster is less than or equal to the minimum voltage of the PCS converter, the PCS converter cannot directly charge the sodium-ion battery cluster, and the switch branch is disconnected. The PCS converter communicates with the bidirectional DC / DC converter in real time to match the voltage. The PCS converter outputs the corresponding DC high-voltage side voltage, and the bidirectional DC / DC converter outputs the matching low-voltage side voltage according to the sodium-ion battery cluster voltage. Step 3: When the sodium-ion battery cluster is discharging to the outside, the PCS converter monitors the voltage of the sodium-ion battery cluster in real time. When it detects that the voltage of the sodium-ion battery cluster is less than or equal to the minimum voltage of the PCS converter, the PCS converter cannot discharge directly to the outside, and the switch branch is disconnected. The PCS converter communicates with the bidirectional DC / DC converter in real time to match the voltage. The bidirectional DC / DC converter outputs the corresponding DC high-voltage side voltage according to the requirements of the PCS converter.

[0015] In this embodiment, the DC low-voltage side voltage range of the bidirectional DC / DC converter is 150V-1000V, and the DC high-voltage side voltage range is 350V-1000V, which meets the bidirectional direct energy flow between low voltage and high voltage (eliminating the high and low voltage difference). The DC low-voltage side of the bidirectional DC / DC converter is the battery terminal voltage, and the DC high-voltage side voltage can be controlled by the PCS converter according to demand.

[0016] The PCS converter is a 1000V-level commercial energy storage PCS converter. The conventional DC side voltage range is 600V-1000V. When the battery side voltage is lower than 600V, the PCS converter cannot work normally.

[0017] The sodium-ion battery cluster is composed of multiple sodium-ion battery cells PACK, and the operating voltage range of the sodium-ion battery cluster is 288V-758.4V. The sodium-ion battery cell capacity is 185Ah, the nominal voltage is 3.0V, and the operating voltage range is 1.5V-3.95V; after the PACK is grouped, the single cluster capacity is 370Ah, the nominal voltage is 576V, the operating voltage range is 288V-758.4V, and the power is 213kWh.

[0018] The voltage range of the sodium-ion battery cluster is 288V-758.4V. When the battery terminal voltage is 288V-600V, it is outside the voltage range of the PCS converter. At this time, a bidirectional DC / DC converter is required for voltage conversion to convert DC low voltage and DC high voltage to meet the operating voltage requirements of the battery terminal and PCS converter.

[0019] The PCS converter monitors the battery terminal voltage in real time. When the voltage of the sodium-ion battery cluster is 600V-758.4V, it is in the normal voltage range of the PCS converter. At this time, the sodium-ion battery cluster can be directly connected to the PCS converter by switching the switch branch, reducing the energy loss caused by the voltage conversion of the bidirectional DC / DC converter.

[0020] The bidirectional DC / DC converter has two modes: buck mode and boost mode: 1. Buck mode of bidirectional DC / DC converter: The PCS converter charges the sodium-ion battery cluster and monitors the battery terminal voltage in real time. If the voltage of the sodium-ion battery cluster is detected to be ≤600V, the PCS converter cannot directly charge the sodium-ion battery cluster, and the switch branch is disconnected. The PCS converter communicates with the bidirectional DC / DC converter in real time to match the voltage. The PCS converter outputs the corresponding DC high-voltage side voltage; the bidirectional DC / DC converter outputs the matching low-voltage side voltage according to the sodium-ion battery cluster voltage. The voltage setting of both ends of the bidirectional DC / DC converter is: 230V≤low-voltage side voltage≤high-voltage side voltage. The low-voltage side is set to be lower than the actual voltage of the sodium-ion battery cluster to ensure the charging capacity of the bidirectional DC / DC converter. The high-voltage side is up to 1000V.

[0021] 2. Boost mode of bidirectional DC / DC converter: When the sodium-ion battery cluster is discharging to the outside, the PCS converter monitors the voltage of the sodium-ion battery cluster in real time. When it is detected that the voltage of the sodium-ion battery cluster is ≤600V, the PCS converter cannot discharge directly to the outside, and the switch branch is disconnected. The PCS converter communicates with the bidirectional DC / DC converter in real time to match the voltage. The bidirectional DC / DC converter outputs the corresponding DC high-voltage side voltage according to the requirements of the PCS converter.

[0022] The voltage setting of both ends of the bidirectional DC / DC converter is: 1000V ≥ high voltage end voltage ≥ low voltage end voltage. The low voltage side is set to be lower than the actual voltage of the sodium ion battery cluster to ensure the charging capacity of the bidirectional DC / DC converter. Its value is ≥230V. The high voltage side is the output voltage of the bidirectional DC / DC converter, and its value is ≥600V and ≤1000V.

[0023] At the same time, in this embodiment, the PCS inverter can control the working state of the switching branch (branch control mode). When the battery terminal voltage is 600V-758.4V, the PCS inverter is in the branch adjustable mode. By adjusting the output voltage of the bidirectional DC / DC converter, when the PCS inverter detects that the difference between the DC low voltage and the DC high voltage is ≤1V, it sends a switching branch signal to directly connect the PCS inverter to the PCS inverter; when it detects that the battery terminal voltage is ≤600V, the switching branch is disconnected to enter the bidirectional DC / DC converter conversion mode.

[0024] In branch control mode, the PCS converter sends a message signal to the battery management system BMS through CAN communication to control the switching switch branch. The battery management system BMS starts the switching soft start in the switching switch branch and monitors the status of the switching soft start node. After the switching soft start works normally, the main contactor is closed and the soft start contactor is disconnected after a delay of 2s. The battery management system BMS feeds back the contactor status information in real time, and the PCS converter limits the power output of the bidirectional DC / DC converter.

[0025] In branch control mode, the PCS converter monitors the battery terminal voltage and the status of the switch branch contactor sent by the battery terminal management system BMS in real time to avoid the situation where the battery terminal voltage range exceeds the DC side voltage range of the PCS converter and cannot be charged and discharged normally.

[0026] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0027] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0028] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A sodium ion battery energy storage system control method, characterized in that: The following steps are involved: Step 1: adding a bidirectional DC / DC converter and a switching switch branch between the sodium ion battery cluster and the PCS converter, wherein the bidirectional DC / DC converter and the switching switch branch are arranged in parallel, and the switching switch branch includes a main contactor and a switching soft starter; Step 2: When the PCS converter is charging the sodium-ion battery cluster, the PCS converter monitors the voltage of the sodium-ion battery in real time. When the voltage of the sodium-ion battery cluster is less than or equal to the minimum voltage of the PCS converter, the PCS converter cannot directly charge the sodium-ion battery cluster, and the switch branch is disconnected. The PCS converter communicates with the bidirectional DC / DC converter in real time to match the voltage. The PCS converter outputs the corresponding DC high-voltage side voltage, and the bidirectional DC / DC converter outputs the matching low-voltage side voltage according to the sodium-ion battery cluster voltage. Step 3: When the sodium-ion battery cluster is discharging to the outside, the PCS converter monitors the voltage of the sodium-ion battery cluster in real time. When it detects that the voltage of the sodium-ion battery cluster is less than or equal to the minimum voltage of the PCS converter, the PCS converter cannot discharge directly to the outside, and the switch branch is disconnected. The PCS converter communicates with the bidirectional DC / DC converter in real time to match the voltage. The bidirectional DC / DC converter outputs the corresponding DC high-voltage side voltage according to the requirements of the PCS converter.

2. A sodium ion battery energy storage system control method according to claim 1, characterized in that: The DC low-voltage side voltage range of the bidirectional DC / DC converter is 150V-1000V, and the DC high-voltage side voltage range is 350V-1000V, which meets the bidirectional direct energy flow between low voltage and high voltage. The DC low-voltage side of the bidirectional DC / DC converter is the battery terminal voltage, and the DC high-voltage side voltage can be controlled by the PCS converter according to demand.

3. A sodium ion battery energy storage system control method according to claim 1, characterized in that: The conventional DC side voltage range of the PCS converter is 600V-1000V.

4. A sodium ion battery energy storage system control method according to claim 1, characterized in that: The sodium ion battery cluster is grouped by a plurality of sodium ion battery monomers PACK, and the operating voltage range of the sodium ion battery cluster is 288V-758.4V.

5. A sodium ion battery energy storage system control method according to claim 1, characterized in that: The PCS converter sends a message signal for controlling the switching switch branch to the battery management system BMS through CAN communication, thereby controlling the working state of the switching switch branch.

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