Composite energy storage system for feedback type load, control method thereof and energy supply system

Abstract

The invention provides a composite energy storage system for a feedback type load, a control method of the composite energy storage system and an energy supply system. The composite energy storage system comprises a composite energy storage unit formed by connecting a super capacitor and a battery in series, and a load direct current bus is connected; the charging unit is composed of a direct-current power supply and a current-limiting resistor, and the discharging unit is composed of a consumption resistor. The corresponding control method is executed by a control unit, and comprises the following steps: system initial preparation; when the load is in peak power consumption, the composite energy storage unit is controlled to discharge, and the supercapacitor provides instantaneous auxiliary power; when the load is in regenerative braking, regenerative current is controlled to charge the composite energy storage unit, the supercapacitor preferentially absorbs instantaneous regenerative power, and the discharge unit is started during overvoltage; in the load idle period, the charging unit is controlled to take power from the mains supply, and the voltage of the supercapacitor is maintained. Through series injection and intelligent charging and discharging management, efficient energy recovery, battery impact buffering and system life prolonging are realized.

Description

Technical Field

[0001] This application relates to the field of elevator energy feedback and energy storage technology, and in particular to a composite energy storage system for feedback loads, its control method and energy supply system, which enables safe parallel connection of different battery packs / energy storage units with the elevator DC bus without reconstructing the internal topology of the battery pack, wide bus voltage adaptation and regenerative energy absorption. Background Technology

[0002] Elevators, as an indispensable vertical transportation tool in modern buildings, generally adopt an AC mains input—rectification—DC bus—inverter drive motor structure in their drive system. When the elevator is heavily loaded and descending or braking, it generates regenerative energy, causing the bus voltage to rise, forming a "pumped voltage." Conversely, when the elevator is heavily loaded and starting or accelerating upward, the motor needs to draw huge power instantaneously, which will cause the DC bus voltage to be subjected to a sudden drop in pressure.

[0003] To address the voltage surge issue caused by regenerative energy, traditional elevators typically convert excess regenerative energy into heat through braking resistors, or feed the energy back to the grid. However, feeding energy back to the grid requires complex energy feedback devices and can introduce grid interference. To improve energy recovery efficiency and reduce braking resistor losses, connecting energy storage units in parallel on the DC bus side has become a solution. This solution aims to store braking energy and release it when the elevator needs power, thus achieving on-site energy recycling. However, the DC bus voltage varies significantly between different brands and models of elevators, such as 540V, 570V, and 690V. This necessitates customizing battery packs with varying numbers of units connected in series for the energy storage system, increasing supply chain management complexity, inventory costs, and maintenance difficulty.

[0004] To overcome the voltage matching challenge, there are two main improvement paths. The first is to use a full-power DC / DC converter between the battery and the bus for voltage conversion, but this method introduces additional conversion losses and increases system size and cost. The second approach, as disclosed in patent document CN118367649A, is a reconfigurable energy unit, circuit, energy storage system, and its reconfiguration and equalization method. This method uses three switches, S1, S2, and S3, to control the series and parallel connection modes of the energy storage units (cells / battery boxes), achieving flexible system reconfiguration. However, this requires the selection of highly reliable, long-life switching devices, increasing cost, and each energy storage unit requires three switches and a monitoring module, increasing system complexity and size.

[0005] Therefore, there is an urgent need in the existing technology for a new type of energy storage system that can efficiently recover and utilize elevator regenerative energy, flexibly adapt to different DC bus voltages, and has a simple structure, controllable cost, and high reliability. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this application provides a composite energy storage system for regenerative loads, its control method, and its power supply system. The purpose is to solve or improve the technical problems of existing energy storage systems, such as poor versatility due to inconsistent elevator DC bus voltages, low energy recovery and utilization rates, significant impact on batteries, and high system complexity and cost.

[0007] To achieve the above objectives, the first aspect of this application provides a composite energy storage system for regenerative loads, comprising:

[0008] The composite energy storage unit is connected at both ends to the positive and negative busbars of the feedback load, and includes a supercapacitor, a series switch and a battery connected in series.

[0009] The charging unit, including a DC power supply and a current-limiting resistor, is configured to enable the DC power supply to be directly connected to the supercapacitor to form a first charging path, or to connect the DC power supply, the supercapacitor, and the current-limiting resistor in series to form a second charging path.

[0010] The discharge unit, including a dissipation resistor, is configured to connect the dissipation resistor in series with the supercapacitor to form a discharge path.

[0011] The control unit is configured to control the charging unit, the discharging unit, and the series switch based on the operating parameters of the regenerative load, the battery, and / or the supercapacitor.

[0012] Optionally, the charging unit includes a pre-charge switch and a bypass switch;

[0013] When the bypass switch is closed, the current-limiting resistor can be shorted to form the first charging path;

[0014] A second charging path can be formed when the pre-charge switch is closed and the bypass switch is open.

[0015] Optionally, the discharge unit includes a discharge switch, a supercapacitor, a discharge switch, and a dissipation resistor connected in series;

[0016] The control unit is capable of detecting the terminal voltage of the supercapacitor and is configured to control the discharge switch to close when the terminal voltage of the supercapacitor exceeds a first threshold.

[0017] Optionally, the control unit can detect the operating parameters of the regenerative load and is configured to: control the start / stop of the DC power supply and / or the operating state of the charging unit according to the operating parameters of the regenerative load, so that the terminal voltage of the supercapacitor is maintained within a preset range below a first threshold.

[0018] Optionally, the positive output terminal of the DC power supply is connected to the positive terminal of the supercapacitor, and the negative output terminal is connected to the first terminal of the bypass switch and the first terminal of the precharge switch.

[0019] The second terminal of the bypass switch is connected to the negative terminal of the supercapacitor;

[0020] The second terminal of the precharge switch is connected to the first terminal of the current-limiting resistor, and the second terminal of the current-limiting resistor is connected to the negative terminal of the supercapacitor.

[0021] Optionally, it also includes:

[0022] The capacitor charging negative terminal switch has its two ends connected to the negative output terminal of the DC power supply and the negative terminal of the battery, respectively.

[0023] The capacitor charging positive switch connects one end to the positive output terminal of the DC power supply and the other end to the positive terminal of the battery.

[0024] The busbar direct-connect switch connects one end to the positive busbar and the other end to the positive terminal of the battery.

[0025] The control unit is configured as follows:

[0026] When the voltage at the supercapacitor terminal is lower than the second threshold and power needs to be drawn from the battery for replenishment, the DC power supply is controlled to stop outputting, and the positive and negative terminals of the capacitor replenishment switch are controlled to close, so as to form a path for replenishing the supercapacitor through the battery.

[0027] When the battery voltage is sufficient to support the DC bus voltage independently, the bus direct switch is closed to allow the battery to be directly connected to both the positive and negative bus.

[0028] Optionally, the control unit is configured to control the series switch as follows:

[0029] During the initial charging of the system, the series switch is kept open.

[0030] When the terminal voltage of the supercapacitor reaches the preset target value and the system self-test is fault-free, the series switch is closed to enable the composite energy storage unit to start working.

[0031] During normal operation after the composite energy storage unit is put into operation, the series switch is kept in the closed state.

[0032] Optionally, the control unit is configured to control the charging unit as follows:

[0033] During the initial charging of the system, the pre-charge switch is closed and the bypass switch is opened.

[0034] When the terminal voltage of the supercapacitor is detected to reach the preset target value, the bypass switch is closed.

[0035] Optionally, the control unit communicates with the main controller of the regenerative load to obtain start-up, braking, or running status commands of the load.

[0036] Secondly, this application provides a power supply system for a regenerative load, including the scheme described in the first aspect above, or any alternative scheme thereof, and a composite energy storage system.

[0037] Thirdly, this application provides a control method for a hybrid energy storage system for a regenerative load. This method is applied to the aforementioned scheme in the first aspect, or any alternative scheme thereof, and includes the following steps:

[0038] Initial preparation steps: Charge the supercapacitor through the charging unit until its terminal voltage reaches the preset target value, and then control the series switch to close so that the composite energy storage unit can be put into operation.

[0039] Discharge assistance step: When the regenerative load is in peak power consumption state, control the composite energy storage unit to discharge to the DC bus, where the supercapacitor provides instantaneous drive power;

[0040] Feedback absorption step: When the regenerative load is in regenerative braking state, the regenerative current is controlled to charge the composite energy storage unit, in which the supercapacitor preferentially absorbs the instantaneous regenerative power;

[0041] Voltage maintenance steps: Based on the operating parameters of the regenerative load, control the start / stop of the DC power supply and / or the operating status of the charging unit to keep the terminal voltage of the supercapacitor within a preset range below the first threshold.

[0042] Overvoltage protection procedure: Monitor the terminal voltage of the supercapacitor and control the discharge unit to discharge energy when it exceeds the first threshold.

[0043] Optionally, the initial preparation steps specifically include:

[0044] The control charging unit forms a second charging path, enabling the DC power supply to charge the supercapacitor in a current-limited manner through the current-limiting resistor.

[0045] When the terminal voltage of the supercapacitor is detected to reach the target value, the charging unit is controlled to form the first charging path, so that the DC power supply directly charges the supercapacitor.

[0046] Once the terminal voltage of the supercapacitor reaches the target value and the system self-test passes, the series switch is closed.

[0047] Optionally, the overvoltage protection steps specifically involve controlling the discharge unit to form a discharge path so that the supercapacitor discharges energy through the consumption resistor.

[0048] Optionally, a predictive management step is included before the discharge assistance step and the feedback absorption step:

[0049] By communicating with the main controller of the regenerative load, start, brake, or running status commands are obtained;

[0050] When the control unit receives a command or forecast that the regenerative braking state is about to be entered by the regenerative load, it checks in advance and ensures that the terminal voltage of the supercapacitor is lower than the second threshold in order to reserve energy absorption capacity.

[0051] When a command or forecast is received that the regenerative load is about to enter its peak power consumption state, the charging unit is controlled in advance to charge the supercapacitor to a preset start-up preparation voltage. The start-up preparation voltage is set to be lower than a first threshold and sufficient to enable the supercapacitor to provide a set instantaneous auxiliary power when the load starts.

[0052] Optionally, the feedback absorption step specifically includes:

[0053] In the initial stage of regenerative braking, the regenerative current is controlled to charge the supercapacitor first, so that its voltage rises rapidly.

[0054] At the same time, a portion of the regenerative current is controlled to charge the battery smoothly.

[0055] Optionally, the voltage maintenance steps also include an energy cycling sub-step:

[0056] After completing the feedback absorption step of a working cycle, when the regenerative load re-enters the discharge assist step, the energy stored in the supercapacitor is released preferentially.

[0057] When the regenerative load is in a low-power state, if the supercapacitor voltage is lower than the target value, the charging unit is controlled to draw power from the DC power supply to charge it to the preset range.

[0058] Optionally, a voltage adaptation step may also be included:

[0059] Before or during operation of the composite energy storage unit, the terminal voltage of the supercapacitor is dynamically adjusted by controlling the charging of the charging unit and the discharging of the discharging unit, so that the output voltage at both ends of the composite energy storage unit matches the rated operating voltage of the DC bus of the feedback load.

[0060] This application has at least the following beneficial effects:

[0061] It features wide-range bus voltage self-adaptation capability and strong versatility. By dynamically adjusting the terminal voltage of the supercapacitor, the total output voltage of the series-connected composite energy storage unit can be flexibly matched to the DC bus voltage of different elevators, such as 540V and 690V. The system does not require customized battery packs for different voltages, significantly reducing supply chain complexity and cost.

[0062] Improving the utilization rate of regenerative braking energy: Through the series injection structure of the battery and capacitor, this application can directly absorb electrical energy during motor regenerative power generation without the need for an additional voltage boosting stage. Since the initial voltage of the capacitor is lower than the motor's generating voltage under proper control, regenerative energy can be recharged even without the boosting device of the motor drive. This eliminates the energy loss in the traditional voltage boosting process and improves the efficiency of regenerative braking energy recovery. Furthermore, the increased total voltage after the capacitor and battery are connected in series allows the braking energy stored in the capacitor to be resupplyed to the elevator drive system at a higher voltage, reducing energy conversion losses.

[0063] This application utilizes AC / DC power to directly charge the supercapacitor from AC power, reducing the burden on the battery: The supercapacitor is charged directly from AC power via an AC / DC conversion circuit, maintaining its voltage at a set level without requiring charging via a battery or complex DC / DC device. This design relieves the battery of the burden of maintaining the capacitor's charge, reducing the number of charge-discharge cycles, lowering the battery load, and helping to extend battery life.

[0064] Safe and stable capacitor charging control: The added charging unit ensures smooth charging of the supercapacitor when powered from the mains, avoiding surge current impacts that may be caused by direct charging, thus improving the safety and stability of system operation. The AC / DC conversion circuit provides a constant and controllable voltage source, keeping the capacitor voltage within the optimized range and preventing long-term deviations from the design value due to changes in elevator operating conditions.

[0065] Active overvoltage protection energy release mechanism: This application designs a capacitor parallel resistor release circuit, with the central control unit monitoring the capacitor voltage in real time and initiating overvoltage discharge as needed. When the elevator regenerates a large amount of energy in a short period, causing the capacitor voltage to exceed the threshold, this release circuit quickly intervenes, releasing the excess energy through heat dissipation, preventing capacitor overvoltage and its adverse effects on the battery and other components. Compared to systems without an independent energy discharge channel, this application can more effectively control the peak regenerative energy and improve the system safety margin.

[0066] Buffering power pulses and extending battery life: Supercapacitors have the advantages of fast charging and discharging speeds and long cycle life, making them suitable for applications involving frequent, short-duration, high-power charging and discharging. This application utilizes capacitors to absorb the instantaneous regenerative energy during elevator deceleration and to provide instantaneous high-power output during elevator startup or acceleration, thus acting as a power buffer. The battery primarily undertakes the tasks of smooth energy supply and long-term energy storage, no longer directly experiencing the surge current of each start / brake. This significantly reduces the stress and heat generated by the battery during rapid charging and discharging at high currents, slowing down the rate of battery capacity decay. Experiments have shown that using supercapacitor assistance can significantly reduce the number of deep discharge cycles of the battery, improving the cycle life of the entire energy storage system. Therefore, this system can significantly extend the lifespan of elevator batteries and reduce maintenance and replacement costs.

[0067] Simple structure and low cost: Compared to some solutions that require multiple DC / DC converters for balanced control, this application achieves similar functionality using mains power and a small number of control components, resulting in a simpler overall structure. This reduces the number of power conversion stages, lowering system complexity and potential failure points. Furthermore, utilizing existing mains power resources to power the capacitors avoids the need for high-power DC / DC modules, saving costs. The central control unit primarily performs switch control and simple voltage comparisons; the control strategy is clear, straightforward, and easy to implement. This makes the system in this application highly cost-effective and conducive to its widespread application in elevator energy-saving retrofits.

[0068] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0069] To more clearly illustrate the technical solutions in the embodiments of this application or the background art, the accompanying drawings used in the embodiments of this application or the background art will be described below.

[0070] Figure 1 The figure shows an energy supply system for a regenerative load provided by this application, and the dashed box in the figure shows the composite energy storage system for a regenerative load provided by this application;

[0071] Figure 2 This is a circuit topology diagram of a composite energy storage system for a regenerative load provided in an embodiment of this application;

[0072] Figure 3 This is a flowchart of a control method for a composite energy storage system for a regenerative load, provided in an embodiment of this application. Detailed Implementation

[0073] The present application will now be described more fully below with reference to the accompanying drawings, in which various embodiments are illustrated. However, the present application may be implemented in many different ways and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present application will be exhaustive and complete, and will fully convey the scope of the present application to those skilled in the art. The same reference numerals denote the same parts throughout the drawings.

[0074] The terminology used herein is for descriptive purposes only and is not intended to be limiting. Unless the context clearly indicates otherwise, the terms “a,” “an,” “the,” and “at least one” as used herein are not intended to limit the quantity but are intended to include both singular and plural forms. For example, unless the context clearly indicates otherwise, “a component” has the same meaning as “at least one component.” “At least one” should not be construed as limited to the quantity “a.” “Or” means “and / or.” The term “and / or” includes any and all combinations of one or more of the associated listed items.

[0075] The terms “comprising” or “including” indicate the presence of a feature, quantity, step, operation, element, component, or combination thereof, but do not preclude the presence or addition of one or more other features, quantities, steps, operations, elements, components, or combinations thereof.

[0076] This document describes implementation methods with reference to circuit schematics or block diagrams as idealized illustrations. Therefore, differences from the actual circuit configuration can be anticipated due to simplifications in the illustrations, drawing scales, or symbolic representations of electronic components. Similarly, the enlarged dimensions of component symbols or line widths shown in the figures for clarity do not represent actual physical proportions or dimensional relationships. Therefore, the circuits shown in the accompanying drawings are schematic in nature, and their specific forms are not intended to show a precise physical layout of the circuit, nor are they intended to limit the scope of the claims.

[0077] In the embodiments of this application, unless otherwise expressly stated, when an element, component, or node is referred to as a "connection," "coupled," or "electrically connected" to another element, component, or node, it can be a direct connection or a connection via one or more intermediary elements, components, or nodes (e.g., resistors, switches, wires, or integrated circuits). The term "connection" in this application primarily refers to an "electrical connection" that forms a current path, but can also be understood, depending on the context, as a physical or structural connection that supports the electrical connection. Similar expressions (such as "connected," "coupled," etc.) should be interpreted similarly.

[0078] The embodiments of the technical solution of this application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples and should not be used to limit the scope of protection of this application.

[0079] The first aspect of this application provides a composite energy storage system for regenerative loads, comprising:

[0080] The composite energy storage unit is connected at both ends to the positive and negative busbars of the feedback load, and includes a supercapacitor, a series switch K1 and a battery connected in series.

[0081] The charging unit, including a DC power supply and a current-limiting resistor R1, is configured to enable the DC power supply to be directly connected to the supercapacitor to form a first charging path, or to connect the DC power supply, the supercapacitor, and the current-limiting resistor R1 in series to form a second charging path.

[0082] The discharge unit includes a dissipation resistor R2, configured to connect the dissipation resistor R2 in series with the supercapacitor to form a discharge path;

[0083] The control unit is configured to control the charging unit, the discharge unit, and the series switch K1 based on the operating parameters of the regenerative load, the battery, and / or the supercapacitor.

[0084] like Figure 1 As shown, this system is designed to be used with loads that have regenerative energy feedback characteristics (such as, but not limited to, elevators, cranes, centrifuges, etc.), and is especially suitable for DC buses connected to such loads to achieve efficient energy recovery and reuse.

[0085] Figure 2 yes Figure 1 The diagram shows a detailed partial circuit structure of the portion indicated by the dashed box. The composite energy storage system provided in this embodiment mainly includes: a composite energy storage unit, a charging unit, a discharging unit, and a control unit.

[0086] The composite energy storage unit, as the core energy storage and injection component of the system, consists of a supercapacitor C, a series switch K1, and a battery (battery pack) connected in series. The battery is a storage battery (bat). Specifically, the positive terminal of the supercapacitor C serves as the positive terminal of the unit and is connected to the positive terminal of the DC bus of the feedback load; the negative terminal of the supercapacitor C is connected to one end of the series switch K1; the other end of the series switch K1 is connected to the positive terminal of the storage battery (bat); and the negative terminal of the storage battery (bat) serves as the negative terminal of the unit and is connected to the negative terminal of the DC bus of the feedback load.

[0087] Explanatoryly, the supercapacitor involved in this application is an electrochemical energy storage device based on the double-layer principle and the Faraday pseudocapacitive effect. It stores energy through electrostatic adsorption of charges at the electrode-electrolyte interface and rapid surface redox reactions. It features high power density, fast charge and discharge speed, and extremely long cycle life (up to hundreds of thousands of times), and is commonly used in energy recovery, instantaneous power compensation, and backup power supplies.

[0088] The battery (bat) serves as the primary energy storage device, providing a stable DC power supply and storing most of the regenerative energy. The supercapacitor (C), acting as a series injection unit, leverages its high power density and long cycle life to rapidly charge and discharge, absorbing regenerative energy from the motor and providing auxiliary power during transient conditions. The total output voltage of the two connected in series is the sum of their individual voltages, thus achieving voltage injection and energy buffering to the DC bus.

[0089] The charging unit provides independent and safe charging energy to the supercapacitor C, drawing energy directly from the mains power supply, thus avoiding the depletion of the battery (bat). This unit specifically includes a DC power supply and a current-limiting resistor R1. In this embodiment, the DC power supply can be an AC / DC converter circuit, and the charging unit can be a pre-charging unit. Its input is connected to the AC mains power supply of the composite energy storage system, such as 220V single-phase power, to rectify and convert the AC mains power into a stable DC voltage suitable for charging the supercapacitor C. Through this AC / DC converter circuit, the system can directly obtain energy from the mains power supply to replenish the charge of the supercapacitor C during low-power regenerative load conditions or off-peak operation, thereby maintaining its operating voltage without consuming the energy stored in the battery (bat). This not only reduces the number of battery cycles but also helps extend the overall battery life.

[0090] A pre-charge unit is connected in series between the DC output terminal of the AC / DC conversion circuit and the two ends of the supercapacitor C. This pre-charge unit also includes a pre-charge switch K5 and a bypass switch K6. In this embodiment, specifically, the positive output terminal of the AC / DC conversion circuit is connected to the positive terminal of the supercapacitor C, and its negative output terminal is connected to the first terminal of the bypass switch K6 and the first terminal of the pre-charge switch K5. The second terminal of the bypass switch K6 is directly connected to the negative terminal of the supercapacitor C. The second terminal of the pre-charge switch K5 is connected to the first terminal of the current-limiting resistor R1, and the second terminal of the current-limiting resistor R1 is connected to the negative terminal of the supercapacitor C. In this connection state, the pre-charge switch K5 and the current-limiting resistor R1 are connected in series to form a first branch; this branch is connected in parallel with the bypass switch K6.

[0091] When the system is initially powered on or when the supercapacitor C needs to be charged from a low voltage, the control unit closes the pre-charge switch K5 and opens the bypass switch K6. At this time, the charging current flows out from the AC / DC conversion circuit, passes through the current-limiting resistor R1, and forms a second charging path. This path enables current-limited soft-start charging of the supercapacitor C, effectively preventing surge current impact. This pre-charge process ensures the safety and stability of the supercapacitor C when it is put into use, preventing large currents from impacting the power grid and devices.

[0092] When the control unit detects that the voltage of the supercapacitor C has risen to near the preset target value, it controls the bypass switch K6 to close. At this time, the low-impedance bypass switch K6 short-circuits the branch containing the current-limiting resistor R1, and the charging current flows out from the AC / DC conversion circuit, mainly flowing through the bypass switch K6, forming the first charging path. The system then enters the normal charging state, where the AC / DC conversion circuit directly performs efficient, stable, and rapid charging of the supercapacitor C.

[0093] In an optional embodiment, the current-limiting resistor R1 is connected in parallel with the bypass switch K6 to form a parallel module; the precharge switch K5 is connected in series with the parallel module.

[0094] When current-limited charging is required, the control unit closes the pre-charge switch K5 and simultaneously opens the bypass switch K6. After current flows through K5, it can only flow to the supercapacitor C through R1, forming a second charging path and achieving current-limited soft start.

[0095] When full-speed charging is required, the control unit keeps the pre-charge switch K5 closed and also closes the bypass switch K6. At this time, after the current flows out from K5, most of it flows through the low-impedance path of K6, effectively shorting R1 and forming the first charging path to achieve fast charging.

[0096] Both circuit structures described above can achieve the core functions of safe current-limited charging through the second charging path and efficient full-speed charging by switching to the first charging path. The control unit manages the switching states and timing of K5 and K6 to achieve safe and efficient management of the entire charging process.

[0097] The discharge unit, as an active safety protection device, includes a dissipation resistor R2 connected in parallel with the supercapacitor C and a discharge switch K7, such as a power transistor or relay. During normal operation, the discharge switch K7 remains open, and the discharge circuit is inactive. When the control unit detects in real time that the terminal voltage of the supercapacitor C exceeds a first threshold, it immediately controls the discharge switch K7 to close, causing the excess charge stored in the supercapacitor C to form a discharge current through the dissipation resistor R2. The electrical energy is rapidly released as heat, thereby actively reducing the capacitor voltage to a safe range. In this embodiment, the first threshold is the maximum safe operating voltage or overvoltage protection action voltage of the supercapacitor C. For example, this threshold can be set to 95%-105% of the rated voltage of the supercapacitor C, with the specific value determined according to the specifications and safety margin of the selected supercapacitor C. This discharge circuit is equivalent to a controllable "electronic braking" device, ensuring that energy is discharged in a controlled manner to prevent overvoltage damage to the capacitor and other components.

[0098] The control unit is the intelligent control core of this system and can be composed of a microcontroller (MCU) or a dedicated control chip. It continuously monitors key parameters such as the operating status of the regenerative load, the voltage and status of the battery (bat), and the terminal voltage of the supercapacitor (C). Its control functions are comprehensive and predictable, controlling the start and stop of the AC / DC conversion circuit according to operating conditions and controlling the switching states of K5 and K6 in the pre-charging unit to achieve safe and efficient management of the entire charging process. It monitors the terminal voltage of the supercapacitor (C) in real time and controls the operation of switch K7 in the discharge unit when it exceeds a first threshold. Furthermore, the control unit implements the following safety logic control on the series switch K1 in the composite energy storage unit: during the initial charging phase of the system, K1 is kept open; when the terminal voltage of the supercapacitor (C) reaches a preset target value and the system self-test is fault-free, K1 is closed, enabling the composite energy storage unit to operate; during normal operation after the energy storage unit is operational, K1 is kept closed. Through the above control, the energy storage branch is safely activated and reliably isolated in case of faults or anomalies.

[0099] By communicating with the main control system of the regenerative load or the motor driver, the system can obtain its operating status commands or operating condition forecast signals to coordinate the operation of the energy storage system.

[0100] To further enhance the energy management flexibility and operating condition adaptability of the hybrid energy storage system, additional switches can be configured to form auxiliary energy paths. For example... Figure 2 As shown, these switches mainly include capacitor charging positive switch K2, capacitor charging negative switch K3, and busbar direct connection switch K4.

[0101] Capacitor replenishment path: One end of the positive terminal switch K2 is connected to the positive output terminal of the DC power supply (i.e., the AC / DC conversion circuit), and the other end is connected to the positive terminal of the battery; the two ends of the negative terminal switch K3 are connected to the negative output terminal of the DC power supply and the negative terminal of the battery, respectively. These two switches together form a battery-capacitor replenishment path. When the system determines that the supercapacitor is low on power and needs to be replenished quickly, and wants to use the battery (rather than mains power) to charge it, the control unit can execute specific logic: first, disconnect the mains input switches K8 and K9, and then close K2 and K3. At this time, the battery's electrical energy can replenish the supercapacitor through the DC power supply (which can be considered as a controllable DC / DC channel). This mode is suitable for scenarios where mains power is unavailable or where it is desirable to reduce dependence on mains power, realizing autonomous energy regulation within the energy storage system.

[0102] Bus Straight-Through Path: One end of the bus straight-through switch K4 is connected to the positive bus, and the other end is connected to the positive terminal of the battery. This switch establishes a straight-through path from the battery to the bus. When the battery terminal voltage is high enough to meet the bus voltage requirements without the need for an additional series boost from the supercapacitor, such as when the battery is fully charged and the load demand is moderate, the control unit can close switch K4. This action is electrically equivalent to short-circuiting the supercapacitor from the series circuit, allowing the battery to be directly connected in parallel to the DC bus. This reduces unnecessary energy circulation in the supercapacitor, lowers system losses, and simplifies control.

[0103] By configuring the aforementioned switches and having them intelligently managed by the control unit, the system can flexibly switch between series injection boost mode, battery-capacitor internal charging mode, and battery direct-through mode, thereby more precisely adapting to different operating conditions and energy states, further optimizing system efficiency, enhancing reliability, and expanding its application flexibility.

[0104] The aforementioned components together constitute the composite energy storage system of this application. Structurally, the battery and supercapacitor C are connected in series via a series switch K1, and then coupled to the DC bus of the regenerative load, thereby "injecting" an energy storage unit composed of a battery and a capacitor into the load's power supply circuit. Unlike existing technologies that directly connect the battery in parallel to the bus or use a supercapacitor alone, this application achieves efficient management and utilization of bidirectional energy flow from the regenerative load through this series connection method and its accompanying dedicated charge and discharge control logic.

[0105] Specifically, by introducing the aforementioned series injection structure into the load power supply circuit, the supercapacitor C can be considered a dynamic voltage regulation unit for the battery terminals. When the load motor requires additional voltage or instantaneous high current support, the supercapacitor C can work together with the battery to raise the total supply voltage or provide instantaneous high current. When the load motor is in regenerative braking mode, the feedback energy will raise the voltage of the supercapacitor C, thereby absorbing and storing most of the instantaneous regenerative power and effectively reducing the voltage fluctuation amplitude experienced by the battery terminals. The entire system does not rely on the complex full-power DC / DC conversion topology commonly found in existing technologies. Instead, it achieves a similar "series injection" effect through a mains-powered charging unit and a controllable parallel discharge unit. This design is particularly suitable for regenerative load applications such as elevators, which already have a mains power supply and whose operating conditions change rapidly. It has the advantages of simple structure, controllable cost, and rapid response.

[0106] The composite energy storage system and its control method for regenerative loads (such as elevators) provided in this application will be described in detail below with reference to the accompanying drawings and embodiments. This embodiment uses an elevator system as a typical application scenario, but the technical solution of this application is also applicable to other electromechanical equipment with regenerative braking characteristics, such as elevators and nodding donkeys.

[0107] like Figure 1 The diagram shows the overall architecture of the regenerative load power supply system involved in this application, with the right side illustrating a common DC bus multi-drive topology. The system includes multiple elevator drive units connected in parallel to the same pair of positive and negative DC buses. Each drive unit includes a grid-side AC / DC conversion circuit and a motor-side DC / AC inverter. The AC / DC conversion circuit feeds mains power into the common DC bus when needed, while the DC / AC inverter draws power from the DC bus to drive the motor, or feeds regenerated energy back to the DC bus when the motor is generating power. A DC meter and a main bus circuit breaker QF are installed between the DC bus and the composite energy storage system on the left. Each drive branch has a pair of DC contactors (e.g., S1 and S2, S3 and S4, etc.) and a branch fuse (FU1…FU4) connected in series on the positive and negative busbars to realize grid connection, maintenance isolation and fault protection of the branch; in addition, each branch is equipped with an AC meter at the mains input terminal to measure the actual amount of electricity drawn by the drive unit from the grid side.

[0108] FL1, marked on the lower side of the main control unit, and FL2, located at the connection between the DC meter and the bus, are both key current acquisition devices.

[0109] FL1 is connected in series in the circuit of the composite energy storage unit to collect the charging and discharging current of the battery and supercapacitor in real time. This current signal is sent to the central control unit, which calculates the real-time charging and discharging power and cumulative charging and discharging capacity (Ah) of the battery and supercapacitor, and uses it for charge state estimation, energy management, and overcurrent protection. FL2 is connected in series in the main bus path where the DC meter is located, also for current collection, and is used to display the current value on the meter.

[0110] These two current sensors, together with the voltage detection points in each branch, form a comprehensive electrical parameter monitoring network for the system. The data they collect forms the physical basis for intelligent energy management, condition assessment, fault diagnosis, and safety protection algorithms, ensuring that the system can reliably control and operate efficiently based on real-time and accurate measurement information.

[0111] The system's operation and energy flow follow a defined path. When any elevator is in an upward or regenerative braking state, energy is typically injected into the common DC bus via the mains power, the elevator's AC / DC conversion circuit, and then drives the motor via the elevator's DC / AC inverter. If there is sufficient energy on the bus from feedback from other elevators or the left-side energy storage system, the drive unit's AC / DC conversion circuit can reduce or even stop drawing power from the mains, instead directly utilizing the existing energy within the bus to achieve energy savings. When the elevator is in a downward or regenerative braking state, the regenerative energy generated by the motor is fed back to the DC bus via the DC / AC inverter, causing the bus voltage to rise. This regenerated energy will be utilized in the following priority order: First, it will be directly absorbed by other elevator drive units currently in operation on the bus, thereby reducing their power consumption from the grid and achieving internal energy sharing. When there is still surplus energy on the bus, the surplus energy will flow through the DC meter and circuit breaker QF to the composite energy storage system on the left side for absorption and storage, stabilizing the bus voltage. If the energy storage system is unavailable or full, and the bus voltage continues to rise, the system will activate the discharge units (such as consumption resistors) built into each drive unit or at the system level to dissipate excess energy as heat, thereby preventing bus overvoltage. The system's start-up, shutdown, and control are based on the bus voltage as the core monitoring variable. By coordinating the operation of each AC / DC conversion circuit, internal energy sharing, interaction with the energy storage system, and the backup of the discharge units, stable control of the bus voltage and efficient utilization of energy are achieved. When a DC-side fault occurs in any single drive branch, the corresponding branch fuse QF and contactor can quickly operate to isolate the faulty branch from the DC bus, ensuring the normal operation of the remaining elevators.

[0112] In summary, Figure 1 The right side features a multi-elevator DC bus system with internal energy sharing and tiered energy absorption capabilities. This system, along with the composite energy storage system on the left, works in synergy through the DC bus to form a complete energy supply solution that is highly efficient, reliable, and has high fault tolerance.

[0113] The second aspect of this application provides an energy supply system for a regenerative load. This energy supply system includes a composite energy storage system as described in any of the embodiments of the first aspect. Therefore, this energy supply system also possesses all the technical features and beneficial effects of a composite energy storage system, and can efficiently manage the bidirectional energy flow generated by the regenerative load during operation, realizing energy recovery, buffering, and reuse, thereby improving the energy efficiency, stability, and economy of the entire energy supply system.

[0114] In a typical embodiment, the circuit topology of the power supply system is as follows: Figure 1 As shown.

[0115] A third aspect of this application provides a control method for a hybrid energy storage system with a regenerative load, applicable to the hybrid energy storage system of any of the foregoing embodiments. This method is executed by a control unit within the system, forming a closed-loop intelligent management process aimed at achieving efficient energy recovery, buffering, and reuse. Specifically, it includes the following core steps.

[0116] The initial preparation steps are a prerequisite for system operation. In this step, the control unit first controls the charging unit to pre-charge the supercapacitor. Specifically, the control unit first controls the charging unit to form a second charging path through the current-limiting resistor R1, allowing the DC power supply to charge the supercapacitor with limited current to suppress inrush current. When the terminal voltage of the supercapacitor is detected to reach the preset target value, the control unit then switches the charging unit to the first charging path, allowing the DC power supply to directly charge the supercapacitor to quickly reach and stabilize the target value. After the supercapacitor voltage reaches the target value and the system self-test is fault-free, the control unit closes the series switch K1, allowing the composite energy storage unit consisting of the battery and supercapacitor connected in series to be formally connected to the DC bus of the feedback load, and the system enters standby mode.

[0117] During actual load operation, the method executes corresponding steps based on the operating conditions. When the regenerative load is at its peak power consumption, a discharge assistance step is performed: the control unit controls the already operational composite energy storage unit to discharge to the DC bus. During this process, the battery provides the main steady-state power output, while the supercapacitor, with its rapid discharge characteristics, provides instantaneous high drive power to help support the bus voltage and meet the peak load demand. The terminal voltage of the supercapacitor will decrease accordingly during this process.

[0118] When the regenerative load is in regenerative braking mode, the regenerative absorption step is executed: the control unit controls the regenerative current to charge the composite energy storage unit. In this step, the supercapacitor, with its high-rate charging capability, is configured to preferentially absorb instantaneous regenerative power, and its terminal voltage rises rapidly; simultaneously, part of the regenerative current is used to slowly charge the battery, thereby achieving "peak shaving and valley filling" of the battery charging current and effectively protecting battery life. If the regenerative energy is too large, causing the supercapacitor voltage to rise above a preset first threshold, the overvoltage protection step is triggered: the control unit immediately controls the discharge unit to operate, forming a discharge path composed of the dissipation resistor R2, allowing the supercapacitor to discharge excess energy through this resistor until its voltage drops back to a safe range.

[0119] Before the discharge assistance step and the regenerative absorption step, a predictive management step can be performed. In this step, starting, braking, or operating status commands are obtained through communication with the main controller of the regenerative load. When the control unit receives a command or forecast that the regenerative load is about to enter regenerative braking state, it checks in advance and ensures that the terminal voltage of the supercapacitor is below a preset second threshold, thereby reserving sufficient energy absorption capacity. When it receives a command or forecast that the load is about to enter peak power consumption state, it controls the charging unit in advance to charge the supercapacitor to a higher start-up preparation voltage, enabling it to release stored energy in time when load demand surges, assisting the battery in providing the required instantaneous auxiliary power. The second threshold is a voltage reference point used to reserve energy absorption capacity, which is lower than the first threshold. For example, this threshold can be set to 80%-90% of the rated voltage of the supercapacitor C. The start-up preparation voltage is lower than the first threshold and sufficient to enable the supercapacitor to provide the set instantaneous auxiliary power when the load starts.

[0120] The above embodiments pre-set multiple voltage parameters. Among them, the first threshold is the limit voltage for overvoltage protection; the target value is the normal voltage maintained by the supercapacitor during standby or light load conditions; the startup preparation voltage is the target voltage for pre-charging during peak power consumption; and the second threshold is the voltage set to ensure regenerative braking absorption capacity. The relationship between them typically satisfies: second threshold < target value < startup preparation voltage < first threshold. For example, in one specific embodiment, the second threshold can be set to 75% of the supercapacitor's rated voltage, the target value for normal system use to be 85%, the startup preparation voltage to be 95%, and the first threshold to be 105%. During standby, the system maintains the supercapacitor voltage near the preset target value; when the load is anticipated to start, it is rapidly charged to the startup preparation voltage to optimize instantaneous power output capability.

[0121] Throughout the operating cycle, the control unit also performs a voltage maintenance step to keep the supercapacitor in optimal operating condition. This step includes an energy cycle sub-step: after completing a feedback absorption step, when the load re-enters the discharge assist step, the control unit prioritizes releasing the regenerated energy stored in the supercapacitor, thereby achieving closed-loop energy utilization. When the regenerative load is in a low-power state, if the supercapacitor voltage falls below the target value due to self-discharge or usage, the control unit activates the charging unit to draw power from the DC power supply (mains power) to replenish the supercapacitor's energy, restoring its voltage and maintaining it within the preset range. Furthermore, the method includes a voltage adaptation step: by coordinating the charging process of the charging unit and the discharging process of the discharging unit before or during system operation, the terminal voltage of the supercapacitor can be dynamically adjusted, allowing the total output voltage of the composite energy storage unit to flexibly match the rated operating voltage of the DC bus of different regenerative loads, enhancing the system's versatility.

[0122] In a typical embodiment, the battery and the supercapacitor are connected in series to the load DC bus. This series connection determines that the equivalent output voltage Vout of the composite energy storage unit to the bus is the sum of the battery terminal voltage Vbat and the supercapacitor terminal voltage Vcap, satisfying the following relationship:

[0123] Vout = Vbat + Vcap

[0124] This feature is the basis for achieving voltage adaptation and dynamic support: by dynamically adjusting Vcap through the control unit, Vout can be matched or supported to meet different bus voltage requirements.

[0125] In summary, this control method, through a series of coordinated and orderly steps, fully utilizes the energy density advantages of batteries and the power density advantages of supercapacitors. It not only efficiently manages the bidirectional energy flow of regenerative loads but also significantly improves the protection effect on batteries and the economy and adaptability of the entire system.

[0126] The following section, in conjunction with the working process of the system in this application, further explains its control methods and implementation details.

[0127] Initial power-on and pre-charging process: When the elevator system is powered on or the system of this application is put into operation, the control unit first puts the AC / DC conversion circuit into working state, which controls the current-limiting resistor R1 of the pre-charging unit to put it into current-limiting mode. At this time, the DC voltage output by the AC / DC conversion circuit is gradually applied to both ends of the supercapacitor C. Under the action of the current-limiting resistor R1, the capacitor is slowly charged, and its voltage rises from the initial 0V. As the capacitor voltage increases, the charging current gradually decreases. When the capacitor voltage is detected to be close to the predetermined target value, the control unit closes the bypass switch K6 of the pre-charging unit, short-circuits the current-limiting resistor R1, and switches to normal charging mode. At this time, the supercapacitor C is charged to the preset target voltage. This pre-charging stage ensures that the capacitor and battery voltage are coordinated before series connection, avoiding instantaneous large current charging and discharging shocks.

[0128] After pre-charging is complete, the control unit, upon confirming that the supercapacitor voltage has reached the target value and the system is functioning normally, controls the series switch K1 to close. At this point, the composite energy storage unit, consisting of the battery and supercapacitor connected in series via K1, is officially connected in parallel to the elevator's DC bus, and the system enters standby operation mode. Subsequently, the control unit can, as needed, control the charging unit to operate in a low-current float charging mode during lightly loaded or idle periods of the elevator to compensate for the supercapacitor's self-discharge, maintaining its terminal voltage near the preset target value and ensuring its ability to absorb or release energy at any time.

[0129] Elevator Upward Heavy Load (Peak Power Consumption Condition): When the elevator needs to lift a heavy load, its motor drive draws a large amount of energy from the DC bus. At this time, the composite energy storage unit actively participates in power supply. The battery provides the main steady-state power output, while the supercapacitor, having been pre-charged to a certain voltage, can immediately release its stored energy, connecting in series with the battery to boost the bus supply voltage or share part of the supply current. Under instantaneous high power demand, the capacitor voltage will drop, releasing charge to provide additional energy. For example, if the elevator's rated DC bus voltage is Vh, obtained by mains rectification, the battery terminal voltage is Vbat, which is lower than Vh, and the capacitor's initial voltage is Vcap, then at peak power consumption, the capacitor voltage drops rapidly by ΔV, injecting this energy into the bus, raising the equivalent supply voltage to approximately Vbat + (Vcap - ΔV). From another perspective, the capacitor provides an instantaneous voltage boost, ensuring that even when the battery voltage is insufficient to support the load alone, the total voltage after series connection can still meet the elevator's drive requirements. During this process, the control unit monitors the capacitor voltage drop. When it falls below a second threshold, it sends a signal to limit the depth of over-discharge, protecting the capacitor's lifespan. Simultaneously, the mains power supply maintains a small charge on the capacitor through the main rectifier and AC / DC conversion circuit (if the load has not depleted the capacitor's charge), ensuring the capacitor does not over-discharge. After the entire upward heavy load process is completed (e.g., the elevator reaches its destination floor and stops accelerating), if the capacitor voltage is low, the main control unit will restart the AC / DC conversion circuit to charge the capacitor back to Vcap with a certain current, preparing for the next cycle.

[0130] Elevator Downward Braking (Regenerative Braking): When the elevator is heavily loaded or decelerating during downward braking, the traction motor switches to generator mode, the DC bus voltage begins to rise, and electrical energy is output. The bus is connected to a series-connected battery and supercapacitor, thus actively absorbing regenerative energy: regenerative current flows through the bus into both the battery and the supercapacitor, charging them. During this process, the battery, limited by its own chemical characteristics, can only accept a limited charging current, and its charging acceptance capacity decreases as its voltage gradually rises towards full charge. In contrast, the supercapacitor can accept rapid charging, and its terminal voltage can rise significantly in a short time, absorbing a large amount of energy. Therefore, most of the braking energy in the initial stage of regenerative braking is stored in the capacitor, and the capacitor voltage gradually rises from Vcap to a higher value. The battery only absorbs a portion of this energy, gently increasing its state of charge and avoiding overcharging in a short period of time.

[0131] The control unit continuously monitors the voltage of the supercapacitor. If the elevator's regenerative energy is low and the capacitor voltage does not exceed the set first threshold, all the energy is stored in the battery and capacitor without any additional action. If the regenerative energy is high, causing the capacitor voltage to rise to near or exceed the first threshold, the control unit controls the discharge switch K7 of the discharge unit to close, allowing the supercapacitor to form a discharge path through the dissipation resistor R2. Excess energy is rapidly discharged as heat, thus clamping the capacitor voltage within a safe range. For example, when the capacitor voltage reaches the first threshold (assumed to be 130% of the initial value), the control circuit conducts the dissipation resistor R2, causing the excess charge on the capacitor to flow through the resistor as current and be converted into heat. Once the capacitor voltage drops below the first threshold, the resistor circuit is disconnected, restoring normal operation. Throughout the process, the elevator's regenerated energy is prioritized for boosting battery and capacitor charge, only being used for heat loss when overflow occurs, maximizing the recovery of braking energy. In addition, the system in this application performs "peak shaving and valley filling" on the charging rate of the battery - that is, the capacitor undertakes the main charging in the early stage of regeneration, and after the regeneration is completed, the capacitor slowly transfers some energy to the battery through the DC link, thereby avoiding the life damage of the battery caused by transient high current charging.

[0132] Energy Reuse and Cycle: After the braking process described above, the supercapacitor typically stores energy exceeding the initial target value. During the subsequent upward movement of the elevator, this stored regenerated energy will be preferentially released and utilized. For example, when the elevator starts its next ascent, the capacitor, due to its higher voltage, can first supply some electrical energy to the elevator motor (consumed via the inverter driver). As the capacitor voltage decreases, the previously stored braking energy is reused to lift the load, achieving closed-loop energy utilization. The battery, in turn, supplies less energy, resulting in battery discharge savings. Similarly, after a running cycle, if the capacitor still has some energy remaining and the battery is not fully charged, the main control can choose to transfer the remaining energy of the capacitor to the battery during elevator idle periods via DC / DC or AC / DC inverters (this application mainly focuses on the structure itself; adding a small-power bidirectional DC / DC converter between the battery and capacitor to optimize energy sharing is not excluded, but this is not a necessary condition). This system ensures that the energy from each elevator deceleration is fully recovered and released during the next run, forming a virtuous cycle of energy and significantly reducing the overall energy consumption of the elevator.

[0133] Based on this, such as Figure 3As shown, the control flow of the composite energy storage system of this application is as follows: After the system is powered on, it first enters the pre-charging stage, where the supercapacitor is charged with current-limited charging by the charging unit until its voltage reaches the target value; then the elevator enters the running state. When the elevator is in peak power consumption conditions such as upward heavy load, the battery provides stable power, and the supercapacitor provides instantaneous drive power, and its terminal voltage drops accordingly; if the capacitor voltage is detected to be lower than the preset second threshold, the control unit will limit its discharge depth and recharge it through the AC / DC conversion circuit after the operating condition ends. When the elevator is in regenerative braking conditions such as downward regenerative braking, the regenerative energy generated by the motor charges both the battery and the supercapacitor. The supercapacitor's voltage rises due to the rapid absorption of most of the transient energy; if its voltage exceeds the safety upper limit, i.e., the first threshold, the control unit immediately activates the parallel discharge circuit (such as the discharge switch K7) to discharge the excess energy through the consumption resistor R2 until the voltage drops back to the safe range. Throughout the entire operating cycle, the control unit continuously manages energy and prepares for the cycle: it prioritizes the release and utilization of regenerated energy stored in the supercapacitor during the next upward cycle of the elevator, and uses an AC / DC conversion circuit to stabilize the supercapacitor voltage near the target value during elevator idle periods, thus preparing for subsequent working cycles. This control process fully demonstrates the efficiency and reliability of the series injection structure in dynamically buffering, recovering, and reusing energy in a typical regenerative load like an elevator.

[0134] In summary, this application constructs a high-efficiency, reliable, and economical composite energy storage system by combining a series injection structure of a battery and a supercapacitor, along with intelligent charging management powered by mains electricity and active overvoltage discharge control. This system not only effectively recovers and utilizes the regenerative braking energy of elevators, improving overall energy efficiency, but also significantly extends the battery's lifespan by buffering power surges through the supercapacitor. Furthermore, it eliminates the need for the expensive and loss-prone full-power DC / DC converter found in traditional solutions, offering advantages such as simple structure, low cost, and flexible control.

[0135] The above description is only a partial embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A composite energy storage system for regenerative loads, characterized in that, include: The composite energy storage unit, with its two ends connected to the positive and negative busbars of the feedback load respectively, includes a supercapacitor, a series switch (K1), and a battery connected in series. The charging unit includes a DC power supply and a current-limiting resistor (R1), configured to: enable the DC power supply to be directly connected to the supercapacitor to form a first charging path, or to connect the DC power supply, the supercapacitor and the current-limiting resistor (R1) in series to form a second charging path; The discharge unit includes a dissipation resistor (R2) configured to connect the dissipation resistor (R2) in series with the supercapacitor to form a discharge path. The control unit is configured to control the charging unit, the discharge unit, and the series switch (K1) based on the operating parameters of the regenerative load, the battery, and / or the supercapacitor.

2. The composite energy storage system according to claim 1, characterized in that, The charging unit includes a precharge switch (K5) and a bypass switch (K6). When the bypass switch (K6) is closed, it can short-circuit the current-limiting resistor (R1) to form the first charging path. The second charging path can be formed when the precharge switch (K5) is closed and the bypass switch (K6) is open.

3. The composite energy storage system according to claim 1, characterized in that, The discharge unit includes a discharge switch (K7), and the supercapacitor, the discharge switch (K7), and the dissipation resistor (R2) are connected in series. The control unit is capable of detecting the terminal voltage of the supercapacitor and is configured to control the discharge switch (K7) to close when the terminal voltage of the supercapacitor is detected to exceed a first threshold.

4. The composite energy storage system according to claim 1 or 2, characterized in that, The control unit is capable of detecting the operating parameters of the regenerative load and is configured to: control the start / stop of the DC power supply and / or the operating state of the charging unit according to the operating parameters of the regenerative load, so that the terminal voltage of the supercapacitor is maintained within a preset range below a first threshold.

5. The composite energy storage system according to claim 2, characterized in that, The positive output terminal of the DC power supply is connected to the positive terminal of the supercapacitor, and the negative output terminal is connected to the first terminal of the bypass switch (K6) and the first terminal of the precharge switch (K5). The second terminal of the bypass switch (K6) is connected to the negative terminal of the supercapacitor; The second terminal of the precharge switch (K5) is connected to the first terminal of the current-limiting resistor (R1), and the second terminal of the current-limiting resistor (R1) is connected to the negative terminal of the supercapacitor.

6. The composite energy storage system according to claim 1, characterized in that, Also includes: The capacitor charging negative terminal switch (K3) is connected at both ends to the negative output terminal of the DC power supply and the negative terminal of the battery, respectively. The capacitor charging positive switch (K2) is connected at one end to the positive output terminal of the DC power supply and at the other end to the positive terminal of the battery. The busbar direct-connect switch (K4) is connected at one end to the positive busbar and at the other end to the positive terminal of the battery. The control unit is configured as follows: When the voltage at the terminal of the supercapacitor is lower than the second threshold and power needs to be drawn from the battery for replenishment, the DC power supply is controlled to stop outputting, and the positive terminal switch (K2) and the negative terminal switch (K3) for capacitor replenishment are controlled to close, so as to form a path for replenishing the supercapacitor through the battery; When the battery voltage is sufficient to support the DC bus voltage alone, the bus direct switch (K4) is closed to allow the battery to be directly connected to the positive and negative bus.

7. The composite energy storage system according to claim 1, characterized in that, The control unit is configured to control the series switch (K1) as follows: During the initial charging of the system, the series switch (K1) is kept open. When the terminal voltage of the supercapacitor reaches the preset target value and the system self-test is fault-free, the series switch (K1) is closed to enable the composite energy storage unit to start working. During normal operation after the composite energy storage unit is put into operation, the series switch (K1) is kept in the closed state.

8. The composite energy storage system according to claim 2, characterized in that, The control unit is configured to control the charging unit as follows: During the initial charging of the system, the pre-charge switch (K5) is closed and the bypass switch (K6) is opened. When the terminal voltage of the supercapacitor is detected to reach a preset target value, the bypass switch (K6) is controlled to close.

9. The composite energy storage system according to claim 1, characterized in that, The control unit is communicatively connected to the main controller of the regenerative load to obtain start-up, braking, or running status commands of the load.

10. A power supply system for a regenerative load, characterized in that, Including the composite energy storage system as described in any one of claims 1 to 9.

11. A control method for a hybrid energy storage system for a regenerative load, applied to the hybrid energy storage system according to any one of claims 1 to 9, characterized in that, Includes the following steps: Initial preparation steps: Charge the supercapacitor through the charging unit until its terminal voltage reaches the preset target value, and then control the series switch (K1) to close so that the composite energy storage unit can be put into operation; Discharge assistance step: When the regenerative load is in peak power consumption state, control the composite energy storage unit to discharge to the DC bus, wherein the supercapacitor provides instantaneous drive power; Feedback absorption step: When the feedback load is in regenerative braking state, the regenerative current is controlled to charge the composite energy storage unit, wherein the supercapacitor preferentially absorbs instantaneous regenerative power; Voltage maintenance steps: Based on the operating parameters of the regenerative load, control the start / stop of the DC power supply and / or the operating state of the charging unit to maintain the terminal voltage of the supercapacitor within a preset range below a first threshold. Overvoltage protection steps: Monitor the terminal voltage of the supercapacitor, and control the discharge unit to discharge energy when it exceeds the first threshold.

12. The control method according to claim 11, characterized in that, The initial preparation steps specifically include: The charging unit is controlled to form the second charging path, so that the DC power supply charges the supercapacitor in a current-limited manner through the current-limiting resistor (R1); When the terminal voltage of the supercapacitor is detected to reach the target value, the charging unit is controlled to form the first charging path, so that the DC power supply directly charges the supercapacitor. After the terminal voltage of the supercapacitor reaches the target value and the system self-test passes, the series switch (K1) is controlled to close.

13. The control method according to claim 11, characterized in that, The overvoltage protection step specifically involves controlling the discharge unit to form the discharge path so that the supercapacitor discharges energy through the dissipation resistor (R2).

14. The control method according to claim 11, characterized in that, Before the discharge-assisted step and the feedback absorption step, a predictive management step is also included: By communicating with the main controller of the regenerative load, start, braking, or running status commands can be obtained; When the control unit receives a command or forecast that the regenerative braking state is about to be entered, it checks in advance and ensures that the terminal voltage of the supercapacitor is lower than the second threshold in order to reserve energy absorption capacity. When receiving an instruction or forecast that the regenerative load is about to enter peak power consumption state, the charging unit is controlled in advance to charge the supercapacitor to a preset start-up preparation voltage. The start-up preparation voltage is set to be lower than the first threshold and sufficient to enable the supercapacitor to provide a set instantaneous auxiliary power when the load starts.

15. The control method according to claim 11, characterized in that, The feedback absorption step specifically includes: In the initial stage of regenerative braking, the regenerative current is controlled to charge the supercapacitor first, causing its voltage to rise rapidly. At the same time, a portion of the regenerative current is controlled to gently charge the battery.

16. The control method according to claim 11, characterized in that, The voltage maintenance step also includes an energy cycling sub-step: After the feedback absorption step of completing one working cycle is completed, when the feedback load re-enters the discharge assist step, the energy stored in the supercapacitor is released preferentially. When the regenerative load is in a low-power state, if the voltage of the supercapacitor is lower than the target value, the charging unit is controlled to draw power from the DC power supply to charge it to the preset range.

17. The control method according to claim 11, characterized in that, It also includes voltage adaptation steps: Before or during operation of the composite energy storage unit, the terminal voltage of the supercapacitor is dynamically adjusted by controlling the charging of the charging unit and the discharging of the discharging unit, so that the output voltage at both ends of the composite energy storage unit matches the rated operating voltage of the DC bus of the feedback load.

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