Direct-hanging energy storage low-pressure maintenance system and method

Abstract

The invention provides a direct-hanging energy storage low-voltage maintenance system and method, and relates to the technical field of power electronic application, and the system comprises a plurality of high-voltage direct-hanging energy storage power modules, a high-voltage direct-hanging energy storage converter control system, a multiplexer switch, and a low-voltage AC maintenance single-phase power supply. The high-voltage direct-hanging energy storage converter control system is used for detecting the SOC of all batteries and controlling each high-voltage direct-hanging energy storage power module; wherein the high-voltage direct-hanging energy storage converter control system is configured to perform maintenance judgment on the SOC of each battery, compare the SOC of each battery with a preset health SOC threshold value, select a battery to be maintained according to a judgment result, and execute a maintenance program on the battery to be maintained; the maintenance program comprises the steps of pre-charging the to-be-maintained module and charging the to-be-maintained battery until the SOC of the to-be-maintained battery meets the requirement. Under the condition that normal operation of the system is not affected, the battery needing to be maintained is processed in a targeted mode, and therefore the performance of the whole energy storage system is improved, and the service life of the whole energy storage system is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics applications, and in particular to a direct-mounted energy storage low-voltage maintenance system and method. Background Art

[0002] High-voltage direct-mounted energy storage technology is an emerging power storage solution that plays an increasingly important role in large-scale renewable energy grid connection, grid stability control and smart grid construction. This technology adopts a chain structure, connecting multiple energy storage units in series to achieve a high-voltage, large-capacity energy storage system.

[0003] The advantage of the chain structure is its modular design and flexibility, which can adjust the system capacity and voltage level according to actual needs. However, this structure also brings some challenges, especially in system startup and maintenance. Black start (the process of restoring power from a completely power-off state) or power-on pre-charging has high requirements on the health of the battery, because in these processes, the battery may be subjected to large instantaneous current and voltage fluctuations.

[0004] Existing research shows that the state of health (SOH) of batteries directly affects their performance and life. Different usage environments and charging and discharging modes will cause the same batch of battery modules to present different health states. In a chain energy storage system, the performance degradation of a single battery module may affect the stability and efficiency of the entire system.

[0005] At present, the maintenance method commonly used in the industry is to regularly inspect and maintain each battery module individually. Some studies have proposed predictive maintenance strategies based on online monitoring, but this method still requires frequent manual intervention. There are also studies that have developed automated maintenance systems, but their applicability is limited to specific types of batteries and energy storage systems.

[0006] Although these existing technologies have improved maintenance efficiency to a certain extent, they still have the following problems: the maintenance process requires frequent manual operations and a large workload; the interference with the normal operation of the system is large, which may cause frequent shutdowns of the energy storage system; it is difficult to achieve accurate and timely maintenance of a single battery module; the maintenance cost is high, especially for large-scale energy storage systems. In addition, with the continuous expansion of the scale of energy storage systems and the diversification of application scenarios, traditional maintenance methods are increasingly difficult to meet actual needs.

[0007] Currently, no effective solution has been proposed for the problems in the related technologies. Summary of the invention

[0008] In view of this, the present invention proposes a direct-mounted energy storage low-voltage maintenance system and method, which monitors the SOC status of each battery in real time, selectively maintains the batteries below the preset health threshold, and uses a combination of pre-charging and charging to charge and maintain the selected batteries using a single-phase low-voltage power supply until their SOC reaches a healthy level. This method can process the batteries that need maintenance in a targeted manner without affecting the normal operation of the system, thereby improving the performance and life of the entire energy storage system, while reducing maintenance costs and complexity.

[0009] The technical solution of the present invention is achieved in this way:

[0010] On the one hand, the present invention provides a direct-mounted energy storage low-voltage maintenance system, including a plurality of high-voltage direct-mounted energy storage power modules, a high-voltage direct-mounted energy storage converter control system, a multi-way selection switch, and a low-voltage AC maintenance single-phase power supply, each high-voltage direct-mounted energy storage power module includes a battery, and the high-voltage direct-mounted energy storage converter control system is used to detect the SOC of all batteries and control each high-voltage direct-mounted energy storage power module;

[0011] Among them, the high-voltage direct-mounted energy storage inverter control system is configured to perform maintenance judgment on the SOC of each battery, compare the SOC of each battery with the preset healthy SOC threshold, select the battery to be maintained according to the judgment result, and execute the maintenance procedure for the battery to be maintained; the maintenance procedure includes pre-charging the maintenance module and charging the battery to be maintained until the SOC of the battery to be maintained meets the requirements.

[0012] On the basis of the above technical solution, preferably, the high-voltage direct-mounted energy storage power module is divided into A-phase module, B-phase module and C-phase module according to the phase, and each battery is divided into A-phase battery, B-phase battery and C-phase battery according to the phase classification of the high-voltage direct-mounted energy storage power module to which it belongs.

[0013] Based on the above technical solution, preferably, the multi-way selection switch is in the initial position N by default. When a maintenance procedure is performed on the battery to be maintained, the corresponding battery is maintained by controlling the multi-way selection switch to switch to the first position A, the second position B or the third position C.

[0014] Based on the above technical solution, preferably, the process of maintaining and judging the SOC of each battery includes:

[0015] The high-voltage direct-mounted energy storage converter control system detects the SOC of the A-phase battery, B-phase battery, and C-phase battery in real time, and compares the collected battery SOC with the preset healthy SOC threshold SOC n Compare and determine whether the battery SOC exceeds the healthy SOC threshold SOC n :

[0016] If the SOC of all batteries is greater than SOCn , it is determined that there is no battery that needs maintenance, and the arm of the multi-way selector switch QF is adjusted to the initial position N;

[0017] If the A-phase battery SOC corresponding to the A-phase module is detected AX Less than SOC n , then adjust the arm of the multi-way selector switch QF to the first position A, start the A-phase module capacitor pre-charging logic corresponding to the battery to be maintained, so as to execute the maintenance procedure;

[0018] If the B-phase battery SOC corresponding to the B-phase module is detected BX Less than SOC n , then adjust the arm of the multi-way selector switch QF to the second position B, start the capacitor pre-charging logic of the B-phase module corresponding to the battery to be maintained, so as to execute the maintenance procedure;

[0019] If the C-phase battery SOC corresponding to the C-phase module is detected CX Less than SOC n , then adjust the arm of the multi-way selection switch QF to the third position C, and start the C-phase module capacitor pre-charging logic corresponding to the battery to be maintained to execute the maintenance procedure.

[0020] On the basis of the above technical solution, preferably, the high voltage direct-mounted energy storage power module includes:

[0021] Batteries, which provide energy storage;

[0022] DC capacitor, used to stabilize the DC capacitor voltage;

[0023] The four switch tubes Q1, Q2, Q3, and Q4 form an H-bridge inverter, which is used to control the bidirectional flow of electric energy;

[0024] Four control switches K1, K2, K3, and K4 are used to control the working status and maintenance operations of the high-voltage direct-mounted energy storage power module;

[0025] The filter inductor is located at the output end of the H-bridge inverter and is used to filter out high-frequency harmonics;

[0026] Terminal blocks are used to connect external circuits.

[0027] On the basis of the above technical solution, preferably, the process of precharging the battery to be maintained includes:

[0028] The high-voltage direct-mounted energy storage power module to which the battery to be maintained belongs is taken as the target module, the phase classification of the target module is obtained, and its phase is taken as the target phase;

[0029] The remaining high-voltage direct-mounted energy storage power modules except the target module in the target phase category are taken as candidate modules;

[0030] The four control switches K1, K2, K3, and K4 of the candidate modules are all disconnected by using the high-voltage direct-mounted energy storage converter control system; and the high-voltage direct-mounted energy storage converter control system is used to control all candidate modules in the phase category to be bypassed;

[0031] Keep the control switches K2 and K3 of the target module open, and close the control switches K1 and K4;

[0032] When the difference between the DC capacitor voltage of the target module and the voltage of the battery to be maintained is within the difference range, the control switches K2 and K3 of the target module are closed, and the battery to be maintained continues to be charged.

[0033] On the basis of the above technical solution, preferably, the process of charging the battery to be maintained includes:

[0034] Calculate the SOC difference between the battery to be maintained and the preset healthy SOC threshold, and calculate the charging current based on the SOC difference;

[0035] According to the charging current, the d-axis voltage and the q-axis voltage in the rotating coordinate system are obtained through dq transformation;

[0036] After dq inverse transformation, a single-phase modulated wave is obtained;

[0037] Output the control signals of the switch tubes Q1, Q2, Q3, and Q4 of the target module corresponding to the battery to be maintained for charging;

[0038] When the SOC of the battery to be maintained reaches the preset healthy SOC threshold, charging is completed and the control switches K1, K2, K3, and K4 of the target module are disconnected.

[0039] Based on the above technical solution, preferably, the calculation formula of the charging current is:

[0040] ΔSOC=SOC X -SOC n

[0041] I g =k SOC ×ΔSOC

[0042] In the formula, ΔSOC is the SOC difference, SOC X is the SOC of the battery to be maintained, X represents the phase to which the battery to be maintained belongs, and SOC n is the preset healthy SOC threshold, k SOC is the proportionality coefficient, I g is the current before limiting on the d-axis of the rotating coordinate system;

[0043] The calculation formulas for the d-axis voltage and q-axis voltage in the rotating coordinate system are:

[0044]

[0045] Where U d is the d-axis voltage in the rotating coordinate system; U q is the q-axis voltage in the rotating coordinate system; is the given voltage of q axis in the rotating coordinate system, I g′ is the current after limiting on the d-axis of the rotating coordinate system; I max is the d-axis limiting current threshold of the rotating coordinate system; S represents the complex frequency variable; k i , k p Indicates closed-loop control parameters.

[0046] On the basis of the above technical solution, preferably, the voltage effective value U of the low voltage AC maintenance single-phase power supply P Greater than the rated voltage U of the high-voltage direct-mounted energy storage power module ncell / 0.9.

[0047] On the other hand, the present invention further provides a method for maintaining low voltage of direct-mounted energy storage, which is executed in any of the above-mentioned systems, and comprises:

[0048] S1 uses a high-voltage direct-mounted energy storage converter control system to detect the SOC of the batteries in each high-voltage direct-mounted energy storage power module in real time, where the batteries in the high-voltage direct-mounted energy storage power module are divided into A-phase batteries, B-phase batteries and C-phase batteries according to the phase;

[0049] S2 compares the detected SOCs with the preset healthy SOC threshold and selects the batteries to be maintained according to the judgment results;

[0050] S3 selects a target phase and controls the multi-way selection switch to switch to the corresponding position;

[0051] S4 selects a battery to be maintained belonging to the target phase;

[0052] S5 performs a pre-charging procedure on the battery to be maintained, controls the opening and closing of the control switch of the corresponding high-voltage direct-mounted energy storage power module, so that the DC capacitor voltage of the corresponding high-voltage direct-mounted energy storage power module is consistent with the voltage of the battery to be maintained;

[0053] S6 executes the charging procedure for the battery to be maintained, calculates the charging current according to the SOC difference, obtains the control signal through dq transformation and inverse transformation, and controls the switch tube of the corresponding high-voltage direct-mounted energy storage power module to charge;

[0054] S7 When the SOC of the battery to be maintained reaches a preset healthy SOC threshold, the charging process is terminated;

[0055] S8 checks whether there are any unmaintained batteries in the target phase:

[0056] If yes, return to step S4;

[0057] If not, switch the multi-way selector switch to the initial position;

[0058] S9 repeats steps S3-S8 until the SOC of all batteries reaches a preset healthy SOC threshold.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) The low-voltage maintenance system for direct-mounted energy storage provided by the present invention can realize automatic detection and online maintenance of a single battery module in a high-voltage direct-mounted energy storage system without disassembling or changing the module and the inherent circuit of the module. This design significantly reduces the complexity and workload of maintenance, improves the reliability and operating efficiency of the system, and reduces maintenance costs and human resource investment, providing a strong guarantee for the long-term stable operation of large-scale energy storage systems;

[0061] (2) The combined design of the multi-way selector switch and the low-voltage AC maintenance single-phase power supply adopted by the present invention enables the system to accurately maintain a single battery module in a high-voltage off-grid state. This method not only ensures the safety of the maintenance process, but also minimizes the interference with other normal working modules, effectively improving the overall availability and continuous operation capability of the system;

[0062] (3) The maintenance judgment logic and pre-charging logic based on SOC (state of charge) proposed in the present invention realizes accurate assessment and timely maintenance of the battery health status. This intelligent maintenance strategy can effectively prevent overcharging and discharging of the battery, extend the battery life, and ensure the stability and reliability of the system during black start or power-on pre-charging, greatly improving the performance and life of the entire energy storage system;

[0063] (4) The direct-mounted energy storage low-voltage maintenance method of the present invention realizes fully automated maintenance of the energy storage system through real-time monitoring, intelligent judgment and automatic execution of maintenance procedures. This method not only greatly improves maintenance efficiency, but also can adapt to various complex application scenarios, such as independent microgrids in remote areas. It greatly reduces the need for manual intervention, improves the reliability and economy of the system, and provides important support for the widespread application of large-scale energy storage systems and the development of smart grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0065] Figure 1 It is the system principle diagram of the present invention;

[0066] Figure 2 This is a schematic diagram of the high-voltage direct-mounted energy storage power module of the present invention;

[0067] Figure 3 It is a maintenance process implementation diagram of the present invention;

[0068] Figure 4 It is the pre-charging principle diagram of the present invention;

[0069] Figure 5 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0070] The following will be combined with 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.

[0071] First, the present invention provides a direct-mounted energy storage low-voltage maintenance system, including a plurality of high-voltage direct-mounted energy storage power modules, a high-voltage direct-mounted energy storage converter control system, a multi-way selection switch, and a low-voltage AC maintenance single-phase power supply. Each high-voltage direct-mounted energy storage power module includes a battery, and the high-voltage direct-mounted energy storage converter control system is used to detect the SOC of all batteries and control each high-voltage direct-mounted energy storage power module;

[0072] Among them, the high-voltage direct-mounted energy storage inverter control system is configured to perform maintenance judgment on the SOC of each battery, compare the SOC of each battery with the preset healthy SOC threshold, select the battery to be maintained according to the judgment result, and execute the maintenance procedure for the battery to be maintained; the maintenance procedure includes pre-charging the maintenance module and charging the battery to be maintained until the SOC of the battery to be maintained meets the requirements.

[0073] The high-voltage direct-mounted energy storage power module is divided into A-phase module, B-phase module and C-phase module according to the phase, and each battery is divided into A-phase battery, B-phase battery and C-phase battery according to the phase classification of the high-voltage direct-mounted energy storage power module to which it belongs. The multi-way selection switch is in the initial position N by default. When the maintenance procedure is performed on the battery to be maintained, the corresponding battery is maintained by controlling the multi-way selection switch to switch to the first position A, the second position B or the third position C.

[0074] like Figure 1 As shown, in one embodiment of the present invention, the direct-mounted energy storage low-voltage maintenance system is composed of: multiple high-voltage direct-mounted energy storage power modules, which are divided into A-phase modules An_PACK to A1_PACK, B-phase modules Bn_PACK to B1_PACK, and C-phase modules Cn_PACK to C1_PACK according to phase; a high-voltage direct-mounted energy storage converter control system CS; a multi-way selection switch QF; and a low-voltage AC maintenance single-phase power supply P.

[0075] The high-voltage direct-mounted energy storage power module includes a battery PACK and a power conversion unit. The A-phase battery SOC is SOC A1 ...SOC An , the B phase battery SOC is SOC B1 ...SOC Bn , the C phase battery SOC is SOC C1 ...SOC Cn ; A phase module DC capacitor voltage U CA1 ...U CAn , B phase module DC capacitor voltage U CB1 ...U CBn , C phase module DC capacitor voltage U CC1 ...U CCn ; Battery voltage U corresponding to phase A module CELLA1 ...U CELLAn , the battery voltage U corresponding to the B phase module CELLB1 ...U CELLBn , the battery voltage U corresponding to the C phase module CELLC1 ...U CELLCn .

[0076] The high-voltage direct-mounted energy storage inverter control system CS detects the SOC (state of charge) of all batteries, controls each high-voltage direct-mounted energy storage power module, makes maintenance judgments, compares the battery SOC with the preset healthy SOC threshold, selects the battery that needs maintenance, and executes maintenance procedures, including pre-charging and charging.

[0077] The multi-way selection switch QF is in the initial position N by default, and can be switched to the first position A, the second position B, and the third position C, which correspond to the maintenance of the three-phase battery respectively.

[0078] The low-voltage AC maintenance single-phase power supply P provides the power required for the maintenance process. Specifically, the effective value of the voltage of the low-voltage AC maintenance single-phase power supply P is U p , High voltage direct-mounted energy storage power module rated voltage U ncell , U p >U ncell / 0.9; set U p >U ncell / 0.9, which is U p >1.11*U ncell , this is to ensure that the voltage of the low-voltage AC maintenance single-phase power supply P is always higher than the rated voltage of the module. This is necessary because to charge the battery, the voltage of the charging power supply must be higher than the rated voltage of the device being charged. In the process of converting AC to DC (through rectification and DC / DC conversion), there will be a certain voltage loss. The coefficient of 0.9 is a conservative estimate after taking this loss into account, ensuring that even in the worst case, the voltage reaching the battery is still sufficient for charging. It should be noted that although a higher voltage is set, during the actual charging process, the system will adjust the voltage and current actually applied to the battery through precise control (such as PWM control) to ensure safety and optimize the charging process. This setting provides sufficient input voltage to give the system enough room for precise control.

[0079] Specifically, Figure 2 As shown, in one embodiment of the present invention, the core components of the high-voltage direct-mounted energy storage power module are as follows:

[0080] Batteries, which provide energy storage;

[0081] DC capacitor, used to stabilize the DC capacitor voltage;

[0082] The four switch tubes Q1, Q2, Q3, and Q4 form an H-bridge inverter, which is used to control the bidirectional flow of electric energy;

[0083] Four control switches K1, K2, K3, and K4 are used to control the working status and maintenance operations of the high-voltage direct-mounted energy storage power module;

[0084] The filter inductor is located at the output end of the H-bridge inverter and is used to filter out high-frequency harmonics;

[0085] Terminal blocks are used to connect external circuits.

[0086] Specifically, the battery is located at the core of the module, used to store and provide electrical energy, and is connected to the DC / DC converter through switches K2 and K3. The DC / DC converter is located between the battery and the DC bus, used to adjust the voltage and current between the battery and the DC bus, and realize bidirectional energy conversion. One end of the DC / DC converter is connected to the battery through switches K2 and K3, and the other end is connected to the DC bus. The DC bus is located between the DC / DC converter and the inverter, serving as a high-voltage DC transmission line inside the module. The four switch tubes Q1, Q2, Q3, and Q4 constitute an H-bridge inverter. The inverter is located between the DC bus and the AC output terminal, converting DC power into AC power, or rectifying AC power into DC power. One end of the inverter is connected to the DC bus, and the other end is connected to the AC output terminal through switch K1. The AC output terminal is located at the output end of the module, which is connected to the external power grid and connected to the inverter through switch K1. The pre-charging circuit includes a pre-charging resistor and a switch K4, which are used to control the charging process of the DC bus to prevent large current shocks. It is connected in parallel at both ends of the switch K1 and controlled by the switch K4. The DC capacitor is located on the DC bus to stabilize the DC bus voltage and filter out ripples.

[0087] These components work together through the above connection relationship, and energy storage and release are achieved through batteries and DC / DC converters; the DC / DC converter adjusts the battery voltage to the DC bus voltage; the inverter realizes bidirectional conversion between DC and AC; the connection or disconnection with the external power grid is achieved by controlling the switch K1; the large current shock at startup is prevented by the pre-charging circuit; different working modes of the module are achieved through the combined operation of each switch; the DC capacitor ensures the stability of the DC bus voltage.

[0088] Its working mode is:

[0089] Charging mode: The grid charges the battery through the inverter and DC / DC converter.

[0090] Discharge mode: The battery supplies power to the grid through a DC / DC converter and inverter.

[0091] Standby mode: The system is in standby state, ready to respond to control commands.

[0092] The system can maintain individual battery modules online without disassembly and assembly; it can achieve automated maintenance through intelligent control; it can perform low-voltage maintenance in high-voltage systems to improve safety; and it is suitable for large-scale energy storage systems, especially three-phase systems.

[0093] like Figure 3 As shown, according to the above system components and working principles, the maintenance judgment of the battery in the high-voltage direct-mounted energy storage power module is realized, and the judgment process is as follows:

[0094] The high-voltage direct-mounted energy storage converter control system detects the SOC of the A-phase battery, B-phase battery, and C-phase battery in real time, and compares the collected battery SOC with the preset healthy SOC threshold SOC n Compare and determine whether the battery SOC exceeds the healthy SOC threshold SOC n :

[0095] If the SOC of all batteries is greater than SOC n , it is determined that there is no battery that needs maintenance, and the arm of the multi-way selector switch QF is adjusted to the initial position N;

[0096] If the A-phase battery SOC corresponding to the A-phase module is detected AX Less than SOC n , then adjust the arm of the multi-way selector switch QF to the first position A, start the A-phase module capacitor pre-charging logic corresponding to the battery to be maintained, so as to execute the maintenance procedure;

[0097] If the B-phase battery SOC corresponding to the B-phase module is detected BX Less than SOC n , then adjust the arm of the multi-way selector switch QF to the second position B, start the capacitor pre-charging logic of the B-phase module corresponding to the battery to be maintained, so as to execute the maintenance procedure;

[0098] If the C-phase battery SOC corresponding to the C-phase module is detected CX Less than SOC n , then adjust the arm of the multi-way selection switch QF to the third position C, and start the C-phase module capacitor pre-charging logic corresponding to the battery to be maintained to execute the maintenance procedure.

[0099] Specifically, the preset healthy SOC threshold SOC n It is a percentage value pre-set based on factors such as battery type and usage environment.

[0100] In this embodiment, the pre-charge logic is as follows:

[0101] The high-voltage direct-mounted energy storage power module to which the battery to be maintained belongs is taken as the target module, the phase classification of the target module is obtained, and its phase is taken as the target phase; the system first identifies the high-voltage direct-mounted energy storage power module to which the battery to be maintained belongs, and defines it as the target module. The phase classification of the target module (A, B or C phase) is determined, and this phase is defined as the target phase.

[0102] The remaining high-voltage direct-mounted energy storage power modules in the target phase category except the target module are taken as candidate modules.

[0103] The four control switches K1, K2, K3, and K4 of the candidate modules are all disconnected by using the high-voltage direct-mounted energy storage converter control system; the high-voltage direct-mounted energy storage converter control system (CS) sends instructions to all candidate modules to disconnect their four control switches K1, K2, K3, and K4. The purpose of this step is electrical isolation.

[0104] Keep the control switches K2 and K3 of the target module open. These two switches connect the battery and the DC / DC converter. Close the control switches K1 and K4. K1 connects the inverter DC capacitor and the DC side positive bus. K4 controls the negative pole of the battery pack and the DC side negative bus. This switch configuration allows the pre-charging circuit to work while protecting the battery from direct impact.

[0105] The high-voltage direct-mounted energy storage converter control system is used to control the bypass of all candidate modules in the phase category; this step involves adjusting the internal connections of the candidate modules to ensure that the AC voltage can be directly applied to the target module through the candidate modules.

[0106] The system continuously monitors the DC capacitor voltage of the target module and the voltage of the battery to be maintained. When the difference between the DC capacitor voltage of the target module and the voltage of the battery to be maintained is within the difference range, the pre-charging process is considered complete. At this time, the system closes the control switches K2 and K3 of the target module to reconnect the battery to the system.

[0107] Specifically, in this embodiment, the purpose of the pre-charging logic is to safely reconnect the battery to be maintained to the system, prevent high current shocks, protect the battery and other system components, ensure that the stability of the entire system is not affected when maintaining a single module, and create safe and stable initial conditions for the subsequent charging process.

[0108] Phase A module A X Capacitor pre-charging logic is used as an example: the high-voltage direct-mounted energy storage converter control system CS controls the switches K1, K2, K3, and K4 of other modules in phase A to disconnect, and keep the A corresponding to the battery to be maintained. X The module switches K2 and K3 are disconnected, and the switches K1 and K4 are closed. The arm of the multi-way selection switch QF is adjusted to the first position A, and the A-phase module capacitor pre-charging logic corresponding to the battery to be maintained is started; at the same time, the high-voltage direct-mounted energy storage converter control system CS controls the bypass of other modules in the A phase, so that only the A phase corresponding to the battery to be maintained is charged. X The module DC capacitor is charged, and when the A X Module DC capacitor voltage U CAX =U CELLAX , close the module switches K2 and K3 corresponding to the battery to be maintained; and continue the charging procedure of the battery to be maintained.

[0109] In this embodiment, the charging logic is as follows:

[0110] Calculate the SOC difference between the battery to be maintained and the preset healthy SOC threshold, and calculate the charging current based on the SOC difference;

[0111] According to the charging current, the d-axis voltage and the q-axis voltage in the rotating coordinate system are obtained through dq transformation;

[0112] After dq inverse transformation, a single-phase modulated wave is obtained;

[0113] Output the control signals of the switch tubes Q1, Q2, Q3, and Q4 of the target module corresponding to the battery to be maintained for charging;

[0114] When the SOC of the battery to be maintained reaches the preset healthy SOC threshold, charging is completed and the control switches K1, K2, K3, and K4 of the target module are disconnected.

[0115] The charging current is calculated as:

[0116] ΔSOC=SOC X -SOC n

[0117] I g =k SOC ×ΔSOC

[0118] In the formula, ΔSOC is the SOC difference, SOC X is the SOC of the battery to be maintained, X represents the phase to which the battery to be maintained belongs, and SOC n is the preset healthy SOC threshold, k SOC is the proportionality factor used to convert the SOC difference into an appropriate charging current, I g is the current before limiting on the d-axis of the rotating coordinate system;

[0119] The calculation formulas for the d-axis voltage and q-axis voltage in the rotating coordinate system are:

[0120]

[0121] Where U d is the d-axis voltage in the rotating coordinate system; U q is the q-axis voltage in the rotating coordinate system; is the given voltage of q axis in the rotating coordinate system, I g′ is the current after limiting on the d-axis of the rotating coordinate system; I max is the d-axis limiting current threshold of the rotating coordinate system; S represents the complex frequency variable; k i , k p Indicates closed-loop control parameters.

[0122] Specifically, in the dq transformation, the d-axis represents the direct axis, which is used to control the active power or current amplitude. The q-axis represents the orthogonal axis, which is used to control the reactive power or phase. The dq inverse transformation converts the voltage information of the d-axis and q-axis back to the time domain to obtain a single-phase modulated wave. This modulated wave will be used to control the switch tube of the inverter. Based on the obtained modulated wave, a control signal is generated to drive the switch tubes Q1, Q2, Q3, and Q4 of the target module. The switching combination of these switch tubes determines the voltage waveform output to the battery. The system continuously monitors the SOC of the battery to be maintained until it reaches the preset healthy SOC threshold. When the battery SOC reaches the target value, the system disconnects all control switches K1, K2, K3, and K4 of the target module to end the charging process.

[0123] In this embodiment, the charging process can accurately control the charging current and voltage through dq conversion and PI control. The charging current is dynamically adjusted according to the SOC difference to make the charging process more efficient. The battery and system components are protected by current limiting. SOC ,k i ,k p ,I max etc.) to optimize the charging process of different types of batteries. This control method is applicable to various battery types and capacities.

[0124] See also Figure 4 , the charging process of phase A battery is described as follows:

[0125] 1. Calculate the charging current:

[0126] ΔSOC AX =SOC AX -SOC n

[0127] I g =k SOC ×ΔSOC AX

[0128]

[0129] 2. After dq inverse transformation, a single-phase modulated wave is obtained.

[0130] 3. Output the A corresponding to the battery to be maintained X Module switch tubes Q1, Q2, Q3, Q4, until SOC AX =SOC n After charging is completed, disconnect switches K1, K2, K3, and K4.

[0131] 4. If the batteries corresponding to other modules of this phase need maintenance, the module capacitor pre-charging logic is repeated; if no batteries corresponding to other modules of this phase need maintenance, the QF arm is adjusted to the N position.

[0132] Also, see Figure 5 The present invention also provides a method for maintaining low voltage of direct-mounted energy storage, which is executed in any of the above-mentioned systems, and includes:

[0133] S1 uses a high-voltage direct-mounted energy storage converter control system to detect the SOC of the batteries in each high-voltage direct-mounted energy storage power module in real time, where the batteries in the high-voltage direct-mounted energy storage power module are divided into A-phase batteries, B-phase batteries and C-phase batteries according to the phase;

[0134] S2 compares the detected SOCs with the preset healthy SOC threshold and selects the batteries to be maintained according to the judgment results;

[0135] S3 selects a target phase and controls the multi-way selection switch to switch to the corresponding position;

[0136] S4 selects a battery to be maintained belonging to the target phase;

[0137] S5 performs a pre-charging procedure on the battery to be maintained, controls the opening and closing of the control switch of the corresponding high-voltage direct-mounted energy storage power module, so that the DC capacitor voltage of the corresponding high-voltage direct-mounted energy storage power module is consistent with the voltage of the battery to be maintained;

[0138] S6 executes the charging procedure for the battery to be maintained, calculates the charging current according to the SOC difference, obtains the control signal through dq transformation and inverse transformation, and controls the switch tube of the corresponding high-voltage direct-mounted energy storage power module to charge;

[0139] S7 When the SOC of the battery to be maintained reaches a preset healthy SOC threshold, the charging process is terminated;

[0140] S8 checks whether there are any unmaintained batteries in the target phase:

[0141] If yes, return to step S4;

[0142] If not, switch the multi-way selector switch to the initial position;

[0143] S9 repeats steps S3-S8 until the SOC of all batteries reaches a preset healthy SOC threshold.

[0144] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A direct-mounted energy storage low-voltage maintenance system, characterized in that: It includes several high-voltage direct-mounted energy storage power modules, a high-voltage direct-mounted energy storage converter control system, a multi-way selection switch, and a low-voltage AC maintenance single-phase power supply. Each high-voltage direct-mounted energy storage power module includes a battery. The high-voltage direct-mounted energy storage converter control system is used to detect the SOC of all batteries and control each high-voltage direct-mounted energy storage power module; Among them, the high-voltage direct-mounted energy storage inverter control system is configured to perform maintenance judgment on the SOC of each battery, compare the SOC of each battery with the preset healthy SOC threshold, select the battery to be maintained according to the judgment result, and execute the maintenance procedure for the battery to be maintained; the maintenance procedure includes pre-charging the maintenance module and charging the battery to be maintained until the SOC of the battery to be maintained meets the requirements.

2. A direct-mounted energy storage low-voltage maintenance system as claimed in claim 1, characterized in that: The high-voltage direct-mounted energy storage power module is divided into A-phase module, B-phase module and C-phase module according to the phase, and each battery is divided into A-phase battery, B-phase battery and C-phase battery according to the phase classification of the high-voltage direct-mounted energy storage power module to which it belongs.

3. A direct-mounted energy storage low-voltage maintenance system as claimed in claim 2, characterized in that: The multi-way selection switch is at the initial position N by default. When a maintenance procedure is performed on a battery to be maintained, the corresponding battery is maintained by controlling the multi-way selection switch to switch to the first position A, the second position B or the third position C.

4. A direct-mounted energy storage low-voltage maintenance system as claimed in claim 3, characterized in that: The process of maintaining and judging the SOC of each battery includes: The high-voltage direct-mounted energy storage converter control system detects the SOC of the A-phase battery, B-phase battery, and C-phase battery in real time, and compares the collected battery SOC with the preset healthy SOC threshold SOC n Compare and determine whether the battery SOC exceeds the healthy SOC threshold SOC n : If the SOC of all batteries is greater than SOC n , it is determined that there is no battery that needs maintenance, and the arm of the multi-way selector switch QF is adjusted to the initial position N; If the A-phase battery SOC corresponding to the A-phase module is detected AX Less than SOC n , then adjust the arm of the multi-way selector switch QF to the first position A, start the A-phase module capacitor pre-charging logic corresponding to the battery to be maintained, so as to execute the maintenance procedure; If the B-phase battery SOC corresponding to the B-phase module is detected BX Less than SOC n , then adjust the arm of the multi-way selector switch QF to the second position B, start the capacitor pre-charging logic of the B-phase module corresponding to the battery to be maintained, so as to execute the maintenance procedure; If the C-phase battery SOC corresponding to the C-phase module is detected CX Less than SOC n , then adjust the arm of the multi-way selection switch QF to the third position C, and start the C-phase module capacitor pre-charging logic corresponding to the battery to be maintained to execute the maintenance procedure.

5. A direct-mounted energy storage low-voltage maintenance system as claimed in claim 2, characterized in that: High voltage direct-mounted energy storage power modules include: Batteries, which provide energy storage; DC capacitor, used to stabilize the DC capacitor voltage; The four switch tubes Q1, Q2, Q3, and Q4 form an H-bridge inverter, which is used to control the bidirectional flow of electric energy; Four control switches K1, K2, K3, and K4 are used to control the working status and maintenance operations of the high-voltage direct-mounted energy storage power module; The filter inductor is located at the output end of the H-bridge inverter and is used to filter out high-frequency harmonics; Terminal blocks are used to connect external circuits.

6. A direct-mounted energy storage low-voltage maintenance system as claimed in claim 5, characterized in that: The process of precharging the battery to be maintained includes: The high-voltage direct-mounted energy storage power module to which the battery to be maintained belongs is taken as the target module, the phase classification of the target module is obtained, and its phase is taken as the target phase; The remaining high-voltage direct-mounted energy storage power modules except the target module in the target phase category are taken as candidate modules; The four control switches K1, K2, K3, and K4 of the candidate modules are all disconnected by using the high-voltage direct-mounted energy storage converter control system; and the high-voltage direct-mounted energy storage converter control system is used to control all candidate modules in the phase category to be bypassed; Keep the control switches K2 and K3 of the target module open, and close the control switches K1 and K4; When the difference between the DC capacitor voltage of the target module and the voltage of the battery to be maintained is within the difference range, the control switches K2 and K3 of the target module are closed, and the battery to be maintained continues to be charged.

7. A direct-mounted energy storage low-voltage maintenance system as claimed in claim 6, characterized in that: The process of charging the maintenance battery includes: Calculate the SOC difference between the battery to be maintained and the preset healthy SOC threshold, and calculate the charging current based on the SOC difference; According to the charging current, the d-axis voltage and the q-axis voltage in the rotating coordinate system are obtained through dq transformation; After dq inverse transformation, a single-phase modulated wave is obtained; Output the control signals of the switch tubes Q1, Q2, Q3, and Q4 of the target module corresponding to the battery to be maintained for charging; When the SOC of the battery to be maintained reaches the preset healthy SOC threshold, charging is completed and the control switches K1, K2, K3, and K4 of the target module are disconnected.

8. A direct-mounted energy storage low-voltage maintenance system as claimed in claim 7, characterized in that: The charging current is calculated as: ΔSOC=SOC X -SOC n I g =k SOC ×ΔSOC In the formula, ΔSOC is the SOC difference, SOC X is the SOC of the battery to be maintained, X represents the phase to which the battery to be maintained belongs, and SOC n is the preset healthy SOC threshold, k SOC is the proportionality coefficient, I g is the current before limiting on the d-axis of the rotating coordinate system; The calculation formulas for the d-axis voltage and q-axis voltage in the rotating coordinate system are: Where U d is the d-axis voltage in the rotating coordinate system; U q is the q-axis voltage in the rotating coordinate system; is the given voltage of q axis in the rotating coordinate system, I g′ is the current after limiting on the d-axis of the rotating coordinate system; I max is the d-axis limiting current threshold of the rotating coordinate system; S represents the complex frequency variable; k i , k p Indicates closed-loop control parameters.

9. A direct-mounted energy storage low-voltage maintenance system as claimed in claim 1, characterized in that: The voltage effective value U of the low voltage AC maintenance single-phase power supply P Greater than the rated voltage U of the high-voltage direct-mounted energy storage power module ncell / 0.

9.

10. A method for maintaining low voltage of direct-mounted energy storage, characterized in that: The method is performed in the system according to any one of claims 1 to 9, and the method comprises: S1 uses a high-voltage direct-mounted energy storage converter control system to detect the SOC of the batteries in each high-voltage direct-mounted energy storage power module in real time, where the batteries in the high-voltage direct-mounted energy storage power module are divided into A-phase batteries, B-phase batteries and C-phase batteries according to the phase; S2 compares the detected SOCs with the preset healthy SOC threshold and selects the batteries to be maintained according to the judgment results; S3 selects a target phase and controls the multi-way selection switch to switch to the corresponding position; S4 selects a battery to be maintained belonging to the target phase; S5 performs a pre-charging procedure on the battery to be maintained, controls the opening and closing of the control switch of the corresponding high-voltage direct-mounted energy storage power module, so that the DC capacitor voltage of the corresponding high-voltage direct-mounted energy storage power module is consistent with the voltage of the battery to be maintained; S6 executes the charging procedure for the battery to be maintained, calculates the charging current according to the SOC difference, obtains the control signal through dq transformation and inverse transformation, and controls the switch tube of the corresponding high-voltage direct-mounted energy storage power module to charge; S7 When the SOC of the battery to be maintained reaches a preset healthy SOC threshold, the charging process is terminated; S8 checks whether there are any unmaintained batteries in the target phase: If yes, return to step S4; If not, switch the multi-way selector switch to the initial position; S9 repeats steps S3-S8 until the SOC of all batteries reaches a preset healthy SOC threshold.

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