Low-voltage charging system and charging method of direct-hanging type energy storage system

Abstract

The invention discloses a low-voltage electricity supplementing system and method of a direct-hanging type energy storage system. The system comprises a direct hanging type energy storage system used for storing and transmitting electric energy; the low-voltage direct-current power supply is connected with the direct-hanging type energy storage system through a connecting capacitor and is used for charging the direct-hanging type energy storage system; wherein the direct hanging type energy storage system comprises at least one power module and at least one bypass switch, and the bypass switch corresponds to the power module and is used for controlling the input state or the bypass state of the power module; the power module comprises a battery unit, a capacitor unit and a switch unit; wherein the battery unit is connected to the two ends of the capacitor unit through an inductor, and the switch unit is connected to the two ends of the capacitor unit; the switch-off unit comprises a half-bridge circuit or a full-bridge circuit.

Description

Technical Field

[0001] This application belongs to the field of energy storage technology, and in particular relates to a low-voltage power supply system and power supply method for a direct-connected energy storage system. Background Technology

[0002] The "new energy + energy storage" model has become an important technological path for promoting the high-quality development of new energy and building a new power system. With the rapid evolution of power grid technology, high-voltage direct-connected energy storage technology, with its significant advantages such as high modularity, fewer energy conversion stages, and high operating efficiency, has shown broad application prospects. This technology can be deeply integrated with modular multilevel converters (MMCs) to form a highly efficient energy storage system solution.

[0003] However, in practical engineering applications, such as during the factory commissioning or on-site installation of energy storage devices, if the overall SOC of a direct-mounted energy storage system is too low and it cannot be replenished with energy through the DC grid, the system will fail to start or operate normally. Traditional charging methods typically charge individual battery modules or battery clusters one by one, which suffers from slow charging speed, low efficiency, and the inability to achieve multi-module coordinated charging, seriously affecting engineering commissioning efficiency and system availability. Summary of the Invention

[0004] This application proposes a low-voltage power replenishment system and method for a direct-connected energy storage system, which at least partially solves the technical problems of slow power replenishment speed, low efficiency, and inability to achieve multi-module collaborative power replenishment in related technologies.

[0005] In a first aspect, this application provides a low-voltage power supply system for a direct-connected energy storage system, comprising:

[0006] Direct-connected energy storage systems are used for storing and transmitting electrical energy;

[0007] A low-voltage DC power supply is connected to the direct-connected energy storage system via a connecting capacitor for charging the direct-connected energy storage system.

[0008] The direct-connected energy storage system includes at least one power module and at least one bypass switch. The bypass switch corresponds to the power module and is used to control the power module's on or bypass state.

[0009] The power module includes a battery unit, a capacitor unit, and a switching unit; wherein the battery unit is connected to both ends of the capacitor unit via an inductor, and the switching unit is connected to both ends of the capacitor unit; the switching unit includes a half-bridge circuit or a full-bridge circuit.

[0010] A second aspect of this application provides a power replenishment method for a low-voltage power replenishment system according to the first aspect, comprising:

[0011] Obtain the actual current value and remaining power on the DC side of the power module;

[0012] The reference duty cycle of the power module is determined based on the difference between the actual current value and the target current value;

[0013] The duty cycle offset of the power module is determined based on the remaining power.

[0014] Based on the reference duty cycle and the duty cycle offset, the target duty cycle corresponding to the power module is obtained;

[0015] The power module is controlled based on the target duty cycle to charge the direct-connected energy storage system using the low-voltage DC power supply.

[0016] As described above, this application provides a low-voltage charging system and method for a direct-connected energy storage system. The system includes a direct-connected energy storage system for energy storage and transmission, which is connected to a low-voltage DC power supply via a connecting capacitor for charging. The direct-connected energy storage system consists of a power module with a bypass switch. The power module includes a battery, a capacitor unit, and a switching unit containing a half-bridge or full-bridge circuit. The charging method obtains the actual current value and remaining charge on the DC side of the power module, determines the reference duty cycle and duty cycle offset, and then obtains the target duty cycle to control the charging of the power module. This effectively utilizes the low-voltage DC power supply to accurately charge the direct-connected energy storage system, improving charging efficiency and energy storage system performance. Furthermore, it enables rapid and differentiated energy replenishment of the direct-connected energy storage system, applicable to both DC and AC direct-connected energy storage systems. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the low-voltage power supply system of the direct-connected energy storage system according to an embodiment of this application.

[0019] Figure 2 This is a schematic diagram illustrating the principle of the low-voltage power supply method for a direct-connected energy storage system according to an embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0021] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] See Figure 1 , Figure 1 A schematic diagram of a low-voltage power supply system for a direct-connected energy storage system according to an embodiment of this application is shown. Figure 1 In the present application, the low-voltage power supply system of the direct-connected energy storage system includes:

[0023] Direct-connected energy storage systems are used for storing and transmitting electrical energy;

[0024] A low-voltage DC power supply is connected to the direct-connected energy storage system via a connecting capacitor for charging the direct-connected energy storage system.

[0025] The direct-connected energy storage system includes at least one power module and at least one bypass switch. The bypass switch corresponds to the power module and is used to control the power module's on or bypass state.

[0026] The power module includes a battery unit, a capacitor unit, and a switching unit; wherein the battery unit is connected to both ends of the capacitor unit via an inductor, and the switching unit is connected to both ends of the capacitor unit; the switching unit includes a half-bridge circuit or a full-bridge circuit.

[0027] In this system, a low-voltage DC power supply is connected to a direct-connected energy storage system for charging via a capacitor. The direct-connected energy storage system consists of multiple power modules with bypass switches, which flexibly control the activation or deactivation of the power modules. Each power module integrates a battery unit, a capacitor unit, and a switching unit containing a half-bridge or full-bridge circuit. The battery unit is connected to the capacitor unit via an inductor, which effectively balances energy distribution during charging, improves charging efficiency, enhances the system's adaptability to different operating conditions, and ensures stable operation of the energy storage system. This method enables rapid and differentiated energy replenishment for direct-connected energy storage systems and is suitable for both DC and AC direct-connected energy storage systems. Specifically, for example... Figure 1 The battery unit may include one or more batteries connected in series. The capacitor unit may include a series-parallel combination of one or more capacitors. The switching unit may include a half-bridge circuit or a full-bridge circuit composed of multiple switches (such as IGBTs, MOSFETs, and other controllable switches).

[0028] In some embodiments, the switching unit includes a first switch and a second switch connected in series, a first terminal of the first switch being connected to a first terminal of the capacitor unit, a second terminal of the first switch being connected to a first terminal of the second switch, and a second terminal of the second switch being connected to a second terminal of the capacitor unit; the bypass switch is connected to the first terminal of the second switch and the second terminal of the second switch.

[0029] The switching unit employs a series connection of a first switch and a second switch. One end of the first switch is connected to the beginning of the capacitor unit, and the other end is connected to one end of the second switch. The other end of the second switch is connected to the end of the capacitor unit, forming a series circuit for precise control of current flow. A bypass switch is connected across the second switch, allowing direct connection to the capacitor unit without bypassing the switching unit. This series connection structure of the switching unit enables fine-tuning of the current within the power module. Combined with the bypass switch, the power module can be quickly bypassed under fault or special operating conditions, ensuring continuous system operation and improving the reliability and flexibility of the charging process in the direct-connected energy storage system.

[0030] In some embodiments, the direct-connected energy storage system includes a DC direct-connected energy storage system or an AC direct-connected energy storage system.

[0031] Among them, direct-connected energy storage systems offer flexibility, configurable as either DC direct-connected or AC direct-connected systems. DC direct-connected systems can directly connect to the DC grid, reducing intermediate conversion stages, minimizing energy loss, and improving the efficiency of DC-side energy storage and release. They are suitable for DC power supply scenarios such as DC microgrids and data centers. AC direct-connected systems, on the other hand, can be directly connected to the AC grid, achieving seamless integration with AC systems. They can quickly respond to power fluctuations in the AC grid, providing auxiliary services such as frequency and voltage regulation, and enhancing grid stability and reliability. The two modes can be selected as needed based on the actual application scenario, effectively improving the applicability and overall benefits of the energy storage system.

[0032] This application also provides a method for power replenishment of a low-voltage power replenishment system based on a direct-connected energy storage system, including:

[0033] Obtain the actual current value and remaining power on the DC side of the power module;

[0034] The reference duty cycle of the power module is determined based on the difference between the actual current value and the target current value;

[0035] The duty cycle offset of the power module is determined based on the remaining power.

[0036] Based on the reference duty cycle and the duty cycle offset, the target duty cycle corresponding to the power module is obtained;

[0037] The power module is controlled based on the target duty cycle to charge the direct-connected energy storage system using the low-voltage DC power supply.

[0038] The process involves first acquiring the actual DC current value and remaining charge of the power module. Using this as a benchmark, the difference between the actual current and the target current is calculated to determine the benchmark duty cycle. The duty cycle offset is then determined based on the remaining charge. These two factors are combined to arrive at the target duty cycle. Finally, the power module is controlled to charge according to the target duty cycle. This precise adjustment of the charging process based on the real-time status of the power module ensures that charging better meets system requirements, effectively improving charging efficiency and accuracy, and guaranteeing stable and efficient recharging of the direct-connected energy storage system.

[0039] In some embodiments, determining the duty cycle offset of the power module based on the remaining power includes:

[0040] The average remaining power is obtained based on the remaining power of all the power modules.

[0041] The duty cycle offset is obtained by proportionally processing the difference between the remaining power of the power module and the average remaining power.

[0042] This system allows for differentiated power replenishment for each energy storage module by calculating the deviation between the State of Charge (SOC) of each module and the average SOC, and then generating a duty cycle offset through proportional control. When determining the duty cycle offset for each power module, the average remaining capacity of all power modules is first calculated. Then, the difference between the remaining capacity of each individual power module and the average remaining capacity is calculated, and this difference is proportionally adjusted to obtain the duty cycle offset. This approach fully considers the differences in the remaining capacity of each power module. By comparing with the average value and adjusting proportionally, the appropriate duty cycle offset can be determined more accurately based on the actual state of each power module. This results in more precise and rational charging control, effectively improving the overall effect and stability of low-voltage power replenishment in direct-connected energy storage systems.

[0043] In some embodiments, determining the reference duty cycle of the power module based on the difference between the actual current value and the target current value includes:

[0044] The difference is subjected to proportional-integral processing to obtain the reference duty cycle;

[0045] The initial value of the ratio basic processing is the ratio of the voltage of the low-voltage DC power supply to the total voltage of the DC side of the direct-connected energy storage system.

[0046] This method employs a closed-loop control mechanism to manage the replenishment current by adjusting the duty cycle. The initial value of the PI controller is set to the ratio of the low-voltage DC power supply voltage to the total DC voltage of the system. The difference between the actual and target current values ​​is first calculated, and then this difference is processed using a proportional-integral (PI) circuit. The initial value for this proportional processing is set to the ratio of the low-voltage DC power supply voltage to the total DC voltage of the direct-connected energy storage system. This approach dynamically and accurately adjusts the reference duty cycle based on current deviations, effectively eliminating steady-state current errors through the PI circuit. Combined with specific initial value settings, this allows the charging control to respond quickly to current changes, improving the stability and accuracy of the charging process and ensuring the efficient and reliable completion of low-voltage replenishment by the direct-connected energy storage system.

[0047] Specifically, see Figure 2 , Figure 2 A schematic diagram illustrating the principle of a low-voltage power replenishment method based on a direct-connected energy storage system according to an embodiment of this application is shown. Figure 2First, the charging current is controlled: a target charging current value Idcref is set, and the difference is calculated with the measured current value Idc in the charging circuit. This difference is then used by a PI controller to calculate the reference duty cycle. The initial value of the PI controller is set as the ratio of the low-voltage DC power supply voltage to the total DC voltage of the direct-connected energy storage system. Next, differentiated duty cycles are generated: to achieve differentiated charging for each energy storage module (e.g., prioritizing charging for modules with lower SOC), the average SOC of each module's battery is calculated. The difference between each module's SOC and the average SOC is calculated, and this difference is processed by a proportional controller to obtain the duty cycle offset for each module. Then, duty cycle synthesis and modulation are performed: the reference duty cycle is added to the corresponding duty cycle offset for each module to obtain the final duty cycle for each module. A carrier phase-shift control algorithm is used to compare the duty cycle of each module with a triangular carrier wave varying within the range of 0 to 1, generating corresponding switching signals to control the charging process of each energy storage module.

[0048] In some embodiments, controlling the power module based on the target duty cycle includes:

[0049] The target duty cycle is compared with a triangular carrier wave to generate a corresponding switching control signal;

[0050] The power module is controlled based on the switch control signal.

[0051] One approach involves employing a carrier phase-shift control algorithm. This algorithm compares the synthesized duty cycle with a triangular carrier wave to generate a switching control signal, enabling coordinated power replenishment control across multiple modules. By comparing the calculated target duty cycle with the triangular carrier wave, the intersection of these two signals generates a precisely corresponding switching control signal. This signal is then used to control the power modules. This control method leverages the regular changes in the triangular carrier wave to dynamically adjust the switching control signal according to the target duty cycle, achieving precise control of the power module's switching state. This effectively improves the stability and accuracy of power transmission during charging, ensuring efficient and reliable low-voltage power replenishment operation of the direct-connected energy storage system.

[0052] In some embodiments, the method further includes: controlling the number of times the bypass switch is turned on to control the number of times the power module is charged.

[0053] In some embodiments, the method further includes: in response to detecting that the power module meets the charging conditions, controlling the bypass switch corresponding to the power module to disconnect, so as to put the power module into charging.

[0054] In some embodiments, the method further includes: in response to detecting that the power module meets the exit condition, controlling the bypass switch corresponding to the power module to turn on, so as to stop the power module from being powered.

[0055] The low-voltage charging process of a direct-connected energy storage system can be optimized by flexibly controlling bypass switches. Specifically, by adjusting the number of open bypass switches, the number of power modules participating in charging can be precisely controlled to adapt to different charging needs. When a power module meets the charging conditions (such as its charge level being below a threshold or the system issuing a charging command), its corresponding bypass switch is promptly disconnected, and the module is put into the charging process. Conversely, if the exit conditions are met (such as the charge level reaching a set value or system overload risk), the bypass switch is immediately turned on, causing the module to exit the charging process. This dynamic control mechanism effectively improves charging efficiency and system safety, avoids overcharging or ineffective charging, and enhances the system's adaptability to complex operating conditions.

[0056] It is evident that the low-voltage power replenishment system and method for direct-connected energy storage systems provided in this application can achieve rapid and differentiated energy replenishment for direct-connected energy storage systems, and are applicable to both DC and AC direct-connected energy storage systems.

[0057] Additionally, to simplify the description and discussion, and to avoid obscuring the embodiments of this application, the well-known power / ground connections to integrated circuit (IC) chips and other components may or may not be shown in the provided drawings. Furthermore, the apparatus may be shown in block diagram form to avoid obscuring the embodiments of this application, and this also takes into account the fact that the details of the implementation of these block diagram apparatuses are highly dependent on the platform on which the embodiments of this application will be implemented (i.e., these details should be fully understood by those skilled in the art). While specific details (e.g., circuits) have been set forth to describe exemplary embodiments of this application, it will be apparent to those skilled in the art that the embodiments of this application can be implemented without these specific details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0058] Although this application has been described in conjunction with specific embodiments thereof, many substitutions, modifications, and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may be used with the embodiments discussed.

[0059] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this application.

Claims

1. A low voltage power makeup system for a direct mount energy storage system, comprising: include: Direct-connected energy storage systems are used for storing and transmitting electrical energy; A low-voltage DC power supply is connected to the direct-connected energy storage system via a connecting capacitor for charging the direct-connected energy storage system. The direct-connected energy storage system includes at least one power module and at least one bypass switch. The bypass switch corresponds to the power module and is used to control the power module's on or bypass state. The power module includes a battery unit, a capacitor unit, and a switching unit; wherein the battery unit is connected to both ends of the capacitor unit via an inductor, and the switching unit is connected to both ends of the capacitor unit; the switching unit includes a half-bridge circuit or a full-bridge circuit.

2. The low voltage power supplementing system of claim 1, wherein, The switching unit includes a first switch and a second switch connected in series. The first end of the first switch is connected to the first end of the capacitor unit, the second end of the first switch is connected to the first end of the second switch, and the second end of the second switch is connected to the second end of the capacitor unit. The bypass switch is connected to the first end of the second switch and the second end of the second switch.

3. The low voltage power supplementing system of claim 1, wherein, The direct-connected energy storage system includes a DC direct-connected energy storage system or an AC direct-connected energy storage system.

4. The method of claim 1-3, wherein, include: Obtain the actual current value and remaining power on the DC side of the power module; The reference duty cycle of the power module is determined based on the difference between the actual current value and the target current value; The duty cycle offset of the power module is determined based on the remaining power. Based on the reference duty cycle and the duty cycle offset, the target duty cycle corresponding to the power module is obtained; The power module is controlled based on the target duty cycle to charge the direct-connected energy storage system using the low-voltage DC power supply.

5. The method of claim 4, wherein, Determining the duty cycle offset of the power module based on the remaining power includes: The average remaining power is obtained based on the remaining power of all the power modules. The duty cycle offset is obtained by proportionally processing the difference between the remaining power of the power module and the average remaining power.

6. The method of claim 4, wherein, Determining the reference duty cycle of the power module based on the difference between the actual current value and the target current value includes: The difference is subjected to proportional-integral processing to obtain the reference duty cycle; The initial value of the ratio basic processing is the ratio of the voltage of the low-voltage DC power supply to the total voltage of the DC side of the direct-connected energy storage system.

7. The method of claim 4, wherein, Controlling the power module based on the target duty cycle includes: The target duty cycle is compared with a triangular carrier wave to generate a corresponding switching control signal; The power module is controlled based on the switch control signal.

8. The method of claim 4, wherein, Also includes: The number of bypass switches turned on is controlled to control the number of power modules that are engaged for charging.

9. The method of claim 8, wherein, Also includes: In response to the detection that the power module meets the charging conditions, the bypass switch corresponding to the power module is opened to allow the power module to be charged.

10. The method according to claim 8, characterized in that, In response to the detection that the power module meets the exit condition, the bypass switch corresponding to the power module is turned on to stop the power module from being powered.

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