Energy storage system and power-on control method thereof

Abstract

The invention relates to the technical field of energy storage systems, and discloses an energy storage system and a power-on control method thereof.The power-on control method of the energy storage system comprises the steps that whether the total voltage difference between battery packs in a battery cluster is larger than a first set value or not is judged; when the total voltage difference between the battery packs in the battery cluster is greater than a first set value, executing a single-cluster parallel power-on and power-off strategy, and carrying out voltage equalization; and when the total voltage difference between the battery packs in the battery cluster is not greater than a first set value, controlling all the battery management units in the battery cluster to be powered on, and closing the corresponding charging and discharging relays. When the total voltage difference between the battery packs in the battery cluster is large, a single-cluster parallel-connection power-on and power-off strategy is executed, voltage balancing is carried out, voltage balancing of each battery pack is ensured, and the problems of relay adhesion, fire and the like caused by large differential voltage are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and in particular to an energy storage system and a power-on control method thereof. Background Art

[0002] At present, in household energy storage products, with the widespread application of large-scale energy storage systems, the safety of the entire energy storage system has gradually become particularly important. Especially when the energy storage parallel stacking system is high voltage, if there is a large voltage difference between the battery packs, the current will be very large at the moment of high voltage, causing relay adhesion, fire and other problems, causing immeasurable losses. Therefore, it is urgent to solve the problem of large pressure difference between battery packs when the energy storage system is high voltage. Summary of the invention

[0003] In view of this, the present invention provides an energy storage system and a power-on control method thereof to solve the problem of pressure difference between battery packs when the energy storage system is at high voltage.

[0004] In a first aspect, the present invention provides a method for controlling power-on of an energy storage system, the method comprising:

[0005] Determining whether the total pressure difference between battery packs in the battery cluster is greater than a first set value;

[0006] When the total voltage difference between the battery packs in the battery cluster is greater than the first set value, the single cluster parallel power-on and power-off strategy is executed to perform voltage balancing;

[0007] When the total voltage difference between the battery packs in the battery cluster is not greater than the first set value, all the battery management units in the battery cluster are controlled to be powered on, and the corresponding charge and discharge relays are closed.

[0008] The present invention provides a power-on control method for an energy storage system. When the total pressure difference between battery packs in a battery cluster is large, a single-cluster parallel power-on and power-off strategy is executed to balance the voltage, thereby ensuring that the voltage of each battery pack is balanced and avoiding problems such as relay adhesion and fire caused by large differential pressure.

[0009] In an optional implementation, when the total voltage difference between battery packs in the battery cluster is greater than a first set value, a single cluster parallel power-on and power-off strategy is executed, including:

[0010] Control the first battery pack in the battery cluster to complete power-on;

[0011] Calculating a first voltage difference between a battery pack with the highest voltage and a battery pack with the lowest voltage;

[0012] Determining whether the first voltage difference is greater than a first set value;

[0013] When the voltage difference is greater than a first set value, performing balanced voltage control;

[0014] When the first voltage difference is not greater than a first set value, all battery packs in the battery cluster are controlled step by step to complete powering on.

[0015] In an optional implementation, when the voltage difference is greater than a first set value, balanced voltage control is performed, including:

[0016] Charge the battery pack with the lowest voltage;

[0017] Determine whether the current voltage of the battery pack with the lowest voltage is not less than a second set value, where the second set value is equal to the voltage of the battery pack with the second lowest voltage + (the current of the battery pack with the lowest voltage*the current DC internal resistance);

[0018] When the current voltage is not less than the second set value, stopping charging of the battery pack with the lowest voltage;

[0019] Determine whether a second voltage difference between the voltage of the battery pack with the lowest voltage and the voltage of the battery pack with the second lowest voltage is not greater than the first set value, and determine whether the duration exceeds a first preset time length;

[0020] When the second voltage difference is not greater than the first set value and lasts for more than a first preset time, the battery pack with the second lowest voltage is updated to the battery pack with the lowest voltage, and the step of charging the battery pack with the lowest voltage is returned until all battery packs in the battery cluster are powered on.

[0021] In an optional embodiment, the method further includes:

[0022] Check whether the energy storage system has entered the multi-cluster parallel mode;

[0023] When the energy storage system enters the multi-cluster parallel mode, the energy management system control board that is awakened first is used as the host, and the other energy management system control boards are used as slaves.

[0024] In an optional embodiment, the method further includes:

[0025] Determine the charging and discharging mode of the energy storage system;

[0026] When the energy storage system is in charging mode, a charging request is made according to a first preset voltage;

[0027] When all battery packs are fully charged, stop charging.

[0028] In an optional embodiment, the method further includes:

[0029] When the energy storage system is in a discharge mode, a cut-off voltage permission is sent according to a second preset voltage;

[0030] Determining whether the energy storage system meets a first preset condition, wherein the first preset condition is that the discharge cut-off SOC value is less than a third set value or the lowest voltage of the entire cluster of online single cells is within a first range;

[0031] When the energy storage system meets a first preset condition, performing force charging on the energy storage system;

[0032] Determining whether the energy storage system meets a second preset condition, wherein the second preset condition is that the discharge cut-off SOC value is greater than a fourth set value or the lowest voltage of the entire cluster of online single cells is within a second range;

[0033] When the energy storage system meets the second preset condition, the forced charging of the energy storage system is canceled.

[0034] In an optional embodiment, the method further includes:

[0035] When the energy storage system does not meet the first preset condition, performing extreme forced charging on the energy storage system;

[0036] Determining whether the energy storage system meets a third preset condition, wherein the third preset condition is that the lowest voltage of the entire cluster of online single cells is within a third range;

[0037] When the energy storage system meets a third preset condition, determining whether the first voltage difference is not greater than a first set value;

[0038] When the first voltage difference is not greater than a first set value, forcibly closing the entire battery pack;

[0039] When the first voltage difference is greater than a first set value, the single cluster lowest voltage battery pack is closed.

[0040] In an optional embodiment, the method further includes:

[0041] Detecting whether the energy management system sends a power-off instruction and detecting whether the charging current is less than a fifth set value and whether the discharging current is greater than a sixth set value;

[0042] When the energy management system sends a power-off command or detects that the charging current is less than the fifth set value or the discharging current is greater than the sixth set value, disconnect all battery pack relays of the single cluster;

[0043] When the energy management system does not send a power-off instruction and detects that the charging current is not less than the fifth set value and the discharging current is not greater than the sixth set value, a charging request is sent.

[0044] In an optional embodiment, the method further includes:

[0045] After clearing the serious fault of the battery pack, when multiple faulty battery packs are restored at the same time, the average voltage of the restored battery packs is subtracted from the average total voltage of the battery packs that have been incorporated into the energy storage system to obtain multiple third voltage difference values;

[0046] sorting the plurality of third voltage difference values ​​in order from small to large;

[0047] Incorporate the corresponding battery packs in order.

[0048] In a second aspect, the present invention provides an energy storage system, the system comprising: a control unit, the control unit comprising an energy management system, a battery management unit and a single cell monitoring unit, the energy management system is communicatively connected to the battery management unit, and the battery management unit is communicatively connected to the single cell monitoring unit, so as to execute the energy storage system power-on control method of the above-mentioned first aspect or any corresponding embodiment thereof.

[0049] The energy storage system provided by the present invention retains all the advantages of the existing solutions, namely, light weight, easy installation, quick plug-in design, fast stacking and other characteristics, compared with the existing series energy storage system and integrated energy storage system; it also solves the difficulties in actual use, and the faulty energy storage module is automatically cut out, and automatically cut in after the fault is cleared, without affecting the user experience; it also solves the consistency problem that the enterprise relies on, the consistency problem of production in different batches, and the production problem of different styles of battery cells; it also solves the problem of user purchasing and use habits, and the problem of mixing new and old batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 is a flow chart of a method for controlling power-on of an energy storage system according to an embodiment of the present invention;

[0052] Figure 2 is a flow chart of another energy storage system power-on control method according to an embodiment of the present invention;

[0053] Figure 3 is a flow chart of another energy storage system power-on control method according to an embodiment of the present invention;

[0054] Figure 4 is a flow chart of another energy storage system power-on control method according to an embodiment of the present invention;

[0055] Figure 5 is a flow chart of another energy storage system power-on control method according to an embodiment of the present invention;

[0056] Figure 6 is a flow chart of another energy storage system power-on control method according to an embodiment of the present invention;

[0057] Figure 7 is a flow chart of another energy storage system power-on control method according to an embodiment of the present invention;

[0058] Figure 8 is a flow chart of another energy storage system power-on control method according to an embodiment of the present invention;

[0059] Fig. 9 is a flow chart of another energy storage system power-on control method according to an embodiment of the present invention;

[0060] Fig.10 is a schematic diagram of a DC parallel machine according to an embodiment of the present invention;

[0061] Fig.11 is a schematic diagram of AC parallel operation according to an embodiment of the present invention;

[0062] Fig.12 Schematic diagram of the structure of an energy storage system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0064] The present invention provides a power-on control method for an energy storage system, which solves the problem of large voltage difference between battery packs through a single-cluster parallel power-on and power-off strategy.

[0065] According to an embodiment of the present invention, an embodiment of a power-on control method for an energy storage system is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0066] In this embodiment, a power-on control method for an energy storage system is provided, which can be used for a high-voltage direct current coupled modular energy storage system. Figure 1is a flow chart of a power-on control method for an energy storage system according to an embodiment of the present invention. Figure 1 As shown, the process includes the following steps:

[0067] Step S10, determining whether the total pressure difference between battery packs in the battery cluster is greater than a first set value.

[0068] Specifically, the energy storage system is started by long pressing the power start button (DI3). After the energy storage system is started, it is first determined whether there is a fault in the first battery pack in the battery cluster. When the fault level is ≤ level 2, the DC IN signal of the BMU (Battery management unit) corresponding to the first battery pack is directly awakened, and the EMS (Energy Management System) locks the D01 signal. Among them, DC IN is a low-voltage wake-up signal, which is a low-voltage wake-up input signal of the BMU; D01 is a power supply wake-up signal, which is a low-voltage wake-up output signal of the EMS, and is used by the EMS to lock the DC IN signal of the BMU. When the fault level is level 3, the first battery pack is powered on at a low voltage, and the DC IN signal of the BMU corresponding to the first battery pack is awakened, and the EMS locks the D01 signal. When the fault level is level 4, the first battery pack is prohibited from being powered on, and the energy storage system cannot operate. Please refer to the power-on and power-off process. Figure 2 The power-on conditions of the BMU relay include: 1: the first power-on, no EMS command is required and the relay remains powered on for 1 minute; 2: the EMS issues a power-on command. The power-off conditions of the BMU relay include: 1: the BMU detects a level 4 fault, no command is required, and the relay is powered off immediately after the condition is successfully determined. 2: the EMS issues a power-off command.

[0069] The DC IN signal of the BMU corresponding to the first battery pack is awakened, and after the EMS locks the D01 signal, it is determined whether the total voltage difference between the battery packs in the battery cluster is greater than the first set value. The first set value is 5V, which is only used as an example and is not limited to this.

[0070] After waking up the DC IN signal of the BMU corresponding to the first battery pack, the EMS locks the D01 signal. In addition to determining whether the total voltage difference between the battery packs in the battery cluster is greater than the first set value, the following operations are performed: the battery packs gradually wake up all the battery packs in the battery cluster through DC OUT, and then the EMS summarizes all the BMU data in CAN1, and the energy storage system performs self-tests on all the battery packs based on the BMU data. Among them, CAN1 is the data interaction communication between the BMU and the EMS. After the self-test passes, the EMS determines the current PCS (Power Conversion System, energy storage converter) power on / off status. If the current PCS is in the power-on state, press and hold for 5 seconds to shut down. Finally, turn off the DC IN signal of the BMU and shut down the battery system. If the current PCS is in the power-off state, press and hold for 3 seconds to shut down.

[0071] Step S11, when the total voltage difference between the battery packs in the battery cluster is greater than the first set value, the single cluster parallel power-on and power-off strategy is executed to perform voltage balancing.

[0072] Specifically, when the total voltage difference between battery packs in a battery cluster is greater than 5V, the single-cluster parallel power-on and power-off strategy is executed to balance the voltage and ensure that the voltage of each battery pack is balanced to avoid overcharging and over-discharging. The single-cluster parallel power-on and power-off strategy is only executed when powering on. If a fault occurs during operation, only the faulty battery cluster is disconnected, and other battery clusters continue to operate, and the corresponding charge and discharge currents are reduced by a certain ratio.

[0073] Step S12: when the total voltage difference between the battery packs in the battery cluster is not greater than the first set value, all battery management units in the battery cluster are controlled to be powered on, and the corresponding charge and discharge relays are closed.

[0074] Specifically, when the total voltage difference between battery packs in the battery cluster is ≤5V, all BMUs are powered on and the corresponding charge and discharge relays are closed.

[0075] The present invention provides a power-on control method for an energy storage system. When the total pressure difference between battery packs in a battery cluster is large, a single-cluster parallel power-on and power-off strategy is executed to balance the voltage, thereby ensuring that the voltage of each battery pack is balanced and avoiding problems such as relay adhesion and fire caused by large differential pressure.

[0076] In an optional implementation, step S11 includes the following process:

[0077] Step S111, controlling the first battery pack in the battery cluster to complete powering on.

[0078] Step S112, calculating a first voltage difference between the battery pack with the highest voltage and the battery pack with the lowest voltage.

[0079] Step S113, determining whether the first voltage difference is greater than a first set value.

[0080] Step S114: when the voltage difference is greater than the first set value, perform balanced voltage control.

[0081] Step S115 , when the first voltage difference is not greater than the first set value, all battery packs in the battery cluster are controlled step by step to complete powering on.

[0082] Specifically, when the total voltage difference between the battery packs in the battery cluster is greater than 5V, the first battery pack in the battery cluster is awakened, and the first battery pack in the battery cluster is controlled to complete power-on. Then the entire cluster of battery packs is awakened step by step to obtain the first voltage difference U1 between the battery pack with the highest voltage and the battery pack with the lowest voltage. When U1≤5V, all battery packs in the entire cluster are closed step by step; when U1>5V, the mobile phone prompts the user to enter the balanced state, please keep the grid connected, and prompt the user: please change the operating mode to "Charging Mode". In addition, regardless of whether there is a grid, the balanced voltage control step is executed. See the flowchart for Figure 3 .

[0083] In an optional implementation, step S114 includes the following process:

[0084] Step S1141, charging the battery pack with the lowest voltage.

[0085] Step S1142, determining whether the current voltage of the battery pack with the lowest voltage is not less than a second set value, the second set value being equal to the voltage of the battery pack with the second lowest voltage + (the current of the battery pack with the lowest voltage * the current DC internal resistance).

[0086] Step S1143, when the current voltage is not less than the second set value, stop charging the battery pack with the lowest voltage.

[0087] Step S1144, determining whether a second voltage difference between the voltage of the battery pack with the lowest voltage and the voltage of the battery pack with the second lowest voltage is not greater than a first set value, and determining whether the duration exceeds a first preset time length.

[0088] Step S1145, when the second voltage difference is not greater than the first set value and lasts longer than the first preset time, the battery pack with the second lowest voltage is updated to the battery pack with the lowest voltage, and the process returns to the step of charging the battery pack with the lowest voltage until all battery packs in the battery cluster are powered on.

[0089] For details, see the flowchart Figure 4 When performing balanced voltage control, the battery pack with the lowest voltage is charged first. The specific operation is as follows: close the pre-charge relay of the battery pack with the lowest voltage, disconnect the relay of the first battery pack (if the voltage of the first battery pack is the lowest, it does not need to be disconnected), close the main relay of the battery pack with the lowest voltage, and disconnect the pre-charge relay for charging. Among them, the charge and discharge request current is initially 5A, and increases at a rate of 1A / S until I 1max Among them, I 1max The maximum allowable charging current. During the relay switching process, the charge and discharge allowable current is first set to 0.

[0090] Then determine whether the current voltage of the battery pack with the lowest voltage is ≥ the voltage of the battery pack with the second lowest voltage + (the current of the battery pack with the lowest voltage * the current DC internal resistance). If the current voltage is ≥ the voltage of the battery pack with the second lowest voltage + (the current of the battery pack with the lowest voltage * the current DC internal resistance), set the charge and discharge current to 0 and stop charging the battery pack with the lowest voltage. After waiting for 10S, set the number of online clusters N=1, determine whether the second voltage difference satisfies 0≤Vmin-Vsecond≤5V and determine for 10S. Among them, Vmin is the voltage of the battery pack with the lowest voltage, Vsecond is the voltage of the battery pack with the second lowest voltage, and the first preset time is 10S. When 0≤Vmin-Vsecond≤5V and lasts for 10S, update the battery pack with the second lowest voltage to the battery pack with the lowest voltage, and update the battery pack with the third lowest voltage to the battery pack with the second lowest voltage, return to step S1141, and charge the battery pack with the lowest voltage again until all battery packs in the battery cluster are powered on. When Vmin-Vsecond<0, a charging request is re-initiated, and when Vmin-Vsecond>0, a wait of 10S is made to determine again whether the second voltage difference satisfies 0≤Vmin-Vsecond≤5V and the determination is made for 10S. In the embodiment of the present invention, the current DC internal resistance is obtained by looking up a table.

[0091] Further, the remaining equilibrium time calculation scheme is:

[0092] 1: After low voltage power-up, EMS collects SOC data of all battery packs;

[0093] 2: After entering the initial startup and paralleling process, determine how many normal battery packs are still not integrated into the system;

[0094] 3: Calculate the capacity of the battery pack currently incorporated: C = C1 + C2 + Cx, C = SOC * 20Ah;

[0095] 4: Get the battery pack with the highest SOC of the normal battery pack and get Cmax = SOC * 20Ah, and get the required charging capacity for parallel operation, X * Cmax, where X is the number of normal battery packs in the whole system;

[0096] 5: Remaining time calculation formula T = (X*Cmax-C) / 17.5A;

[0097] 6: When the parallel connection is completed, the timer is cleared, allowing the user to change the mode;

[0098] 7: When the parallel connection is not completed, the timer card does not change in the last minute, and is cleared immediately after the parallel connection is completed.

[0099] The above calculation method is a simple calculation formula. If accurate calculation is required, factors such as current and waiting time must also be considered.

[0100] In an optional implementation, the energy storage system power-on control method further includes:

[0101] Step S20, detecting whether the energy storage system enters a multi-cluster parallel mode.

[0102] Step S21, when the energy storage system enters the multi-cluster parallel mode, the energy management system control board that is awakened first is used as the host, and the other energy management system control boards are used as slaves.

[0103] For details, see the flowchart Figure 5 , wake up the DC IN signal of the BMU corresponding to the first battery pack. After the EMS locks the D01 signal, it is also necessary to detect whether the energy storage system has entered the multi-cluster parallel mode. When CAN3 has a message and a parallel resistor, it is determined that the energy storage system has entered the multi-cluster parallel mode. Among them, CAN3 is the data exchange communication between EMS and EMS. At this time, the energy management system control board that is awakened first is used as the host, and other energy management system control boards are used as slaves. The host collects CAN3 data and sends data through CAN2, and the slave CAN2 data stops sending. Among them, CAN2 is the data exchange communication between EMS and PCS. Determine whether there is a serious fault in all battery packs in a single cluster. When a serious fault occurs in all battery packs in a single cluster, the operating allowable power is reduced. If any energy storage module has a protection fault, the BMU cuts out the circuit and reports the fault to the EMS. The EMS identifies and adjusts the operating power in real time. For example, when cluster 1 has 3 battery packs operating normally, cluster 2 has 1 battery pack operating normally, cluster 3 has 2 battery packs operating normally, and cluster 4 has no normal battery pack operation. It is known that the operating power of 2 or more is P, and the operating power of 1 is 0.5P. The allowable charging and discharging power of the entire system = P+0.5P+P+0=2.5P.

[0104] In an optional implementation, the energy storage system power-on control method further includes:

[0105] Step S30, determining the charge and discharge mode of the energy storage system.

[0106] Step S31: when the energy storage system is in charging mode, a charging request is made according to a first preset voltage.

[0107] Step S32, when all battery packs are fully charged, stop charging.

[0108] For details, see the flowchart Figure 6After EMS determines the current PCS power on / off status, it determines the charge and discharge mode of the energy storage system according to the current flow direction. When the energy storage system is in charging mode, a charging request is made according to the voltage of 350.4V. Among them, the first preset voltage is 350.4V. When all battery packs are fully charged, charging stops, and the charging demand of the entire cluster is 0A. Among them, Vmax≥3.6V / 1S. Then determine whether the following conditions are met: the Vmax of the entire cluster online monomer is ≤3.4V or the discharge current of the entire cluster is ≥5A / 3S or SOC≤95%. When met, the full charge mark is cleared.

[0109] In an embodiment of the present invention, if one battery pack is full and charging stops, while other battery packs are not yet full, the full battery pack will provide circulation power to other battery packs. When the SOC (State of Charge) voltage drops, the full charge mark is cleared and the PCS is requested to charge again until the total voltage of all battery packs is at a uniform level. At this time, the SOC of each battery pack is calibrated to 100%.

[0110] There are two conditions for single pack SOC calibration: 1: If the battery pack Max_CV ≥ 3.6V during this process, the charging is terminated immediately, which is defined as charging stop, and the SOC is 100%. 2: When the battery pack Max_CV ≥ 3.45V, the charging current is < 5A for 5S, and the calibration SOC is determined to be 100%.

[0111] In an optional implementation, the energy storage system power-on control method further includes:

[0112] Step S40: When the energy storage system is in the discharge mode, a cut-off voltage permission is sent according to the second preset voltage.

[0113] Step S41, determining whether the energy storage system meets a first preset condition, the first preset condition being that the discharge cut-off SOC value is less than a third set value or the lowest voltage of the entire cluster of online single cells is within a first range.

[0114] Step S42: When the energy storage system meets the first preset condition, the energy storage system is force-charged.

[0115] Step S43, determining whether the energy storage system meets a second preset condition, the second preset condition being that the discharge cut-off SOC value is greater than a fourth set value or the lowest voltage of the entire cluster of online single cells is within a second range.

[0116] Step S44: when the energy storage system meets the second preset condition, cancel the forced charging of the energy storage system.

[0117] For details, see the flowchart Figure 7, when the energy storage system is in discharge mode, a cut-off voltage permission is sent according to the voltage of 250V. Among them, the second preset voltage is 250V. When the energy storage system meets the discharge cut-off SOC value <10% or 2.5≤Vmin≤2.8V, a strong charge mark request is sent to force charge the energy storage system. Among them, the third setting value is 10%, and Vmin is the lowest voltage of the entire cluster of online single cells. When the energy storage system meets the discharge cut-off recovery SOC value >15% or Vmin≥3.1V, the strong charge mark is cleared and the strong charge of the energy storage system is cancelled. Among them, the fourth setting value is 15%. When the battery cell is undervoltage alarm, the over-discharge mark. When the energy storage system meets the entire cluster of online single cells Vmin≥3.0V or the charging current≥5A / 3S, the over-discharge mark is cleared.

[0118] In the embodiment of the present invention, the SOC for judging discharge cutoff is the average SOC of all online cluster battery packs; the discharge cutoff SOC does not disconnect the relay, but only sends the request precondition of the strong charge mark; the discharge cutoff and recovery SOC values ​​can be set by the host computer and the cloud platform.

[0119] In an optional implementation, the energy storage system power-on control method further includes:

[0120] Step S45: When the energy storage system does not meet the first preset condition, the energy storage system is forcedly charged to the limit.

[0121] Step S46, determining whether the energy storage system meets a third preset condition, the third preset condition being that the lowest voltage of the entire cluster of online single cells is within a third range.

[0122] Step S47, when the energy storage system meets the third preset condition, determine whether the first voltage difference is not greater than the first set value.

[0123] Step S48, when the first voltage difference is not greater than the first set value, the entire battery pack is forcibly closed.

[0124] Step S49: when the first voltage difference is greater than the first set value, the single cluster lowest voltage battery pack is closed.

[0125] For details, see the flowchart Figure 8. When the energy storage system does not meet the discharge cut-off SOC value of <10% or 2.5≤Vmin≤2.8V, press and hold the button for more than 10S to enter the limit forced charging, and perform limit forced charging on the energy storage system. Then, when the BMU determines that the lowest voltage of the single cells of all battery packs in the entire discharge cluster meets 2.0≤Vmin<2.5V, it determines whether the first voltage difference U1 between the battery pack with the highest voltage and the battery pack with the lowest voltage is ≤5V. When U1≤5V, the entire cluster of battery packs is forced to close for 5min; when U1>5V, the single cluster of lowest voltage battery packs is closed. Next, the BMU detects whether the EMS sends a power-off command and the BMU detects whether the charging current is less than the fifth setting value and the BMU detects whether the discharge current is greater than the sixth setting value. When the EMS sends a power-off command or detects that the charging current is less than the fifth setting value or the discharge current is greater than the sixth setting value, the relays of all battery packs in the single cluster are disconnected. When the EMS does not send a power-off command and detects that the charging current is not less than the fifth setting value and the discharge current is not greater than the sixth setting value, a charging request is sent and step S43 is returned. Among them, the fifth setting value is 1A / 5min, and the sixth setting value is 1A / 3s.

[0126] In an optional implementation, the energy storage system power-on control method further includes:

[0127] Step S50, after clearing the serious fault of the battery pack, when multiple faulty battery packs are restored at the same time, the average voltage of the restored battery packs is subtracted from the average total voltage of the battery packs that have been incorporated into the energy storage system to obtain multiple third voltage difference values.

[0128] Step S51, sorting the plurality of third voltage differences in order from small to large.

[0129] Step S52, integrating corresponding battery packs in sequence.

[0130] For details, see the flowchart Fig. 9 . After all batteries fail the self-test, determine whether the battery pack has a serious fault. When there is a serious fault, the faulty battery pack turns off the charge and discharge relays and exits the system. Taking the original number of online clusters as 3 as an example, if the current number of online normal battery packs N = 2, the energy storage system operates normally; if the current number of online normal battery packs N = 1, the energy storage system operates at a reduced rate; if the current number of online normal battery packs N = 0, the energy storage system stops operating. The high-voltage DC coupled modular energy storage system solution can automatically cut out the faulty energy storage module from the system and stop using it.

[0131] After clearing the serious fault of the battery pack, the average voltage Verr of the faulty battery pack is compared with the average total voltage Vave of the battery packs that have been integrated into the system, and the number of online clusters N is detected. When multiple faulty battery packs are restored at the same time, the closing logic is that the battery pack corresponding to the smallest third voltage difference |Verr-Vave| is first incorporated and queued in sequence. In an embodiment of the present invention, when the corresponding battery pack is incorporated, the total negative and pre-charge relays of the faulty battery pack are closed, the main positive relay is closed, the pre-charge is disconnected, and the faulty battery pack is automatically incorporated without any APP reminder.

[0132] The solution of the modular energy storage system with high voltage DC coupling can automatically cut out the faulty energy storage module from the system and stop using it. When the system voltage is inconsistent, the system can be automatically cut in and used after the cut-in conditions are met after normal use by the user. This embodiment can also be applied to the use of new and old batteries and different types of battery cells, and the automatic cut-in and cut-out functions can be achieved through the voltage control method.

[0133] In an optional implementation manner, the DC parallel operation schematic diagram is as follows: Fig.10 As shown, the capacity is expanded to a maximum of 2 clusters. Fig.11 As shown, the power and capacity are expanded to a maximum of 6 clusters.

[0134] The present invention provides an energy storage system, including a control unit, the control unit including an energy management system, a battery management unit and a single cell monitoring unit, the energy management system is communicatively connected to the battery management unit, and the battery management unit is communicatively connected to the single cell monitoring unit, so as to execute the energy storage system power-on control method of the above-mentioned embodiment.

[0135] Specifically, Fig.12 As shown in the figure, the modular energy storage system architecture of high-voltage DC coupling consists of multiple modular energy storage modules and an inverter control integrated machine, where one energy storage module represents a battery pack. The energy storage architecture of the entire system is parallel, and each energy storage module is equipped with an independent control system, namely the battery management unit BMU and the single-cell monitoring unit CMU, which has the function of switching in and out of the main circuit. The energy management unit EMS and the inverter device are integrated inside the inverter control integrated machine. The DC side adopts a three-level control architecture, namely the single-cell monitoring unit CMU, the battery management unit BMU, and the energy management unit EMS. Among them, the single-cell monitoring unit CMU is responsible for collecting the basic data, voltage, temperature, internal resistance and balancing function of the battery cell; the battery management unit BMU is responsible for processing the battery cell data and circuit control, battery cell fault warning and protection, status display, heating control, pre-charge control, and main circuit control function; the energy management unit EMS is responsible for dispatching all energy storage modules in the parallel circuit, and dispatching the inverter device to reasonably use the energy of the energy storage module.

[0136] Furthermore, compared with the existing series energy storage system and integrated energy storage system, this embodiment retains all the advantages of the existing solutions, namely, light weight, easy installation, quick plug-in design, fast stacking and other characteristics; it also solves the difficulties in actual use, the faulty energy storage module is automatically cut out, and it is automatically cut in after the fault is cleared, which does not affect the user experience; it also solves the consistency problem that the enterprise relies on, the consistency problem of production in different batches, and the production problem of different styles of battery cells; it also solves the problem of user purchasing and usage habits, and the problem of mixing new and old batteries.

[0137] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for controlling power-on of an energy storage system, characterized in that: The method comprises: Determining whether the total pressure difference between battery packs in the battery cluster is greater than a first set value; When the total voltage difference between the battery packs in the battery cluster is greater than the first set value, the single cluster parallel power-on and power-off strategy is executed to perform voltage balancing; When the total voltage difference between the battery packs in the battery cluster is not greater than the first set value, all the battery management units in the battery cluster are controlled to be powered on, and the corresponding charge and discharge relays are closed.

2. The energy storage system power-on control method according to claim 1, characterized in that: When the total voltage difference between the battery packs in the battery cluster is greater than the first set value, the single cluster parallel power-on and power-off strategy is executed, including: Control the first battery pack in the battery cluster to complete power-on; Calculating a first voltage difference between a battery pack with the highest voltage and a battery pack with the lowest voltage; Determining whether the first voltage difference is greater than a first set value; When the voltage difference is greater than a first set value, performing balanced voltage control; When the first voltage difference is not greater than a first set value, all battery packs in the battery cluster are controlled step by step to complete powering on.

3. The energy storage system power-on control method according to claim 2, characterized in that: When the voltage difference is greater than a first set value, balanced voltage control is performed, including: Charge the battery pack with the lowest voltage; Determine whether the current voltage of the battery pack with the lowest voltage is not less than a second set value, where the second set value is equal to the voltage of the battery pack with the second lowest voltage + (the current of the battery pack with the lowest voltage*the current DC internal resistance); When the current voltage is not less than the second set value, stopping charging of the battery pack with the lowest voltage; Determine whether a second voltage difference between the voltage of the battery pack with the lowest voltage and the voltage of the battery pack with the second lowest voltage is not greater than the first set value, and determine whether the duration exceeds a first preset time length; When the second voltage difference is not greater than the first set value and lasts for more than a first preset time, the battery pack with the second lowest voltage is updated to the battery pack with the lowest voltage, and the step of charging the battery pack with the lowest voltage is returned until all battery packs in the battery cluster are powered on.

4. The energy storage system power-on control method according to claim 1, characterized in that: The method further comprises: Check whether the energy storage system has entered the multi-cluster parallel mode; When the energy storage system enters the multi-cluster parallel mode, the energy management system control board that is awakened first is used as the host, and the other energy management system control boards are used as slaves.

5. The energy storage system power-on control method according to claim 2, characterized in that: The method further comprises: Determine the charging and discharging mode of the energy storage system; When the energy storage system is in charging mode, a charging request is made according to a first preset voltage; When all battery packs are fully charged, stop charging.

6. The energy storage system power-on control method according to claim 5, characterized in that: The method further comprises: When the energy storage system is in a discharge mode, a cut-off voltage permission is sent according to a second preset voltage; Determining whether the energy storage system meets a first preset condition, wherein the first preset condition is that the discharge cut-off SOC value is less than a third set value or the lowest voltage of the entire cluster of online single cells is within a first range; When the energy storage system meets a first preset condition, performing force charging on the energy storage system; Determining whether the energy storage system meets a second preset condition, wherein the second preset condition is that the discharge cut-off SOC value is greater than a fourth set value or the lowest voltage of the entire cluster of online single cells is within a second range; When the energy storage system meets the second preset condition, the forced charging of the energy storage system is canceled.

7. The energy storage system power-on control method according to claim 6, characterized in that: The method further comprises: When the energy storage system does not meet the first preset condition, performing extreme forced charging on the energy storage system; Determining whether the energy storage system meets a third preset condition, wherein the third preset condition is that the lowest voltage of the entire cluster of online single cells is within a third range; When the energy storage system meets a third preset condition, determining whether the first voltage difference is not greater than a first set value; When the first voltage difference is not greater than a first set value, forcibly closing the entire battery pack; When the first voltage difference is greater than a first set value, the single cluster lowest voltage battery pack is closed.

8. The energy storage system power-on control method according to claim 7, characterized in that: The method further comprises: Detecting whether the energy management system sends a power-off instruction and detecting whether the charging current is less than a fifth set value and whether the discharging current is greater than a sixth set value; When the energy management system sends a power-off command or detects that the charging current is less than the fifth set value or the discharging current is greater than the sixth set value, disconnect all battery pack relays of the single cluster; When the energy management system does not send a power-off instruction and detects that the charging current is not less than the fifth set value and the discharging current is not greater than the sixth set value, a charging request is sent.

9. The energy storage system power-on control method according to claim 2, characterized in that: The method further comprises: After clearing the serious fault of the battery pack, when multiple faulty battery packs are restored at the same time, the average voltage of the restored battery packs is subtracted from the average total voltage of the battery packs that have been incorporated into the energy storage system to obtain multiple third voltage difference values; sorting the plurality of third voltage difference values ​​in order from small to large; Incorporate the corresponding battery packs in order.

10. An energy storage system, characterized in that: The system includes: a control unit, the control unit includes an energy management system, a battery management unit and a single cell monitoring unit, the energy management system is communicatively connected to the battery management unit, and the battery management unit is communicatively connected to the single cell monitoring unit, so as to execute the energy storage system power-on control method described in any one of claims 1 to 9.

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