Energy storage system electron pre-charging device and method based on negative electrode Buck topology

Abstract

The invention discloses an energy storage system electronic pre-charging device and method based on a negative electrode Buck topology. The Buck type electronic pre-charging device comprises a negative electrode Buck constant-current pre-charging circuit, a first switch K1, a second switch K2, a direct-current bus capacitor Cx and a micro-control unit MCU. The negative electrode Buck constant-current pre-charging circuit comprises a semiconductor switch assembly Q1, a Schottky diode D, an inductor L and an energy storage capacitor Co. The control unit MCU outputs a PWM signal with a set frequency, and controls the on-off of the semiconductor switch assembly Q1 according to a duty ratio formula; the control unit MCU obtains a current signal collected in real time, dynamically adjusts the PWM duty ratio through a PI closed-loop algorithm, and maintains constant-current charging. An isolation power supply and an isolation drive are cancelled, and a pre-charging scheme with high efficiency, low cost, fast protection and easy integration is realized.

Description

Technical Field

[0001] This invention relates to the field of energy storage system technology, and in particular to an electronic pre-charging device and method for an energy storage system based on a negative electrode Buck topology. Background Technology

[0002] With the rapid development of new energy technologies, energy storage systems are increasingly widely used in grid frequency regulation, peak-valley filling, distributed generation, and electric vehicles. Energy storage systems contain large-capacity energy storage components such as supporting capacitors or battery packs. If these energy storage components are directly connected to the DC bus at the moment of system startup or main circuit contactor closure, a huge surge current will be generated due to the significant voltage difference between them. This can cause contactor contact erosion, shorten its service life, and in severe cases, even lead to system failure and threaten operational safety.

[0003] To ensure reliable system startup, pre-charging has become an indispensable and critical step in energy storage systems. The core purpose of pre-charging is to gradually raise the voltage of the energy storage elements to near the bus voltage level through a controlled process before the main circuit is fully connected, thereby minimizing the inrush current at the moment of circuit closure. Currently, pre-charging technology for energy storage systems mainly employs the following implementation schemes: The resistor-relay pre-charging scheme, as the most traditional pre-charging method, connects a pre-charging resistor with an appropriate resistance value and a contactor (or relay) connected in parallel in the path between the DC bus and the energy storage element to be pre-charged. Although the resistor current-limiting scheme is widely used due to its simple structure and low cost, it suffers from high energy loss and low system efficiency. During the pre-charging process, the huge current flowing through the current-limiting resistor generates considerable heat, which is not used for effective charging of the energy storage element, thus reducing the overall energy efficiency of the system.

[0004] The positive-side Buck electronic pre-charge solution uses switching power supply technology to replace traditional resistor pre-charge, deploying switching devices at the positive terminal of the system based on the BUCK step-down circuit. While this solution solves the resistor heating problem, it introduces new technical challenges: it requires a complex isolation drive and sampling system. Since the reference ground of the BUCK circuit is located at the positive terminal potential of the battery, which is not at the same potential as the control circuit, magnetic isolation technology must be used to achieve signal transmission and power supply; EMC performance challenges are significant, with high common-mode noise caused by high voltage side fluctuations, and complex filtering circuits; the cost is high, with isolation devices and numerous peripheral components increasing the cost.

[0005] In recent years, the industry has proposed the concept of negative electrode buck pre-charge, which has been mentioned in technical white papers from companies such as ADI and NXP. This concept theoretically avoids the need for isolation by placing the buck circuit reference ground at the negative electrode of the battery. However, this concept currently remains theoretical, lacking concrete circuit implementation solutions and thus unable to be directly applied to actual product development.

[0006] Therefore, there is an urgent need to propose an innovative pre-charging method that combines high efficiency, low cost, fast protection, and easy integration. Summary of the Invention

[0007] The purpose of this invention is to provide an electronic pre-charging device and method for energy storage systems based on negative Buck topology, eliminating the need for isolated power supplies and isolated drives, and achieving a pre-charging solution that is highly efficient, low-cost, fast-protected, and easy to integrate.

[0008] To achieve the above objectives, the present invention provides the following solution: An electronic pre-charging device for an energy storage system based on a negative Buck topology includes: a negative Buck constant current pre-charging circuit, a switch K1, a switch K2, a DC bus capacitor Cx, and a microcontroller unit (MCU). The negative electrode Buck constant current pre-charge circuit includes a semiconductor switching component Q1, a Schottky diode D, an inductor L, and an energy storage capacitor Co; The input terminal of the semiconductor switch assembly Q1 is connected to the negative terminal of the battery module, and the output terminal is connected to one end of the inductor L and the anode of the Schottky diode D, respectively. The other end of the inductor L is connected to one end of the energy storage capacitor Co, one end of the DC bus capacitor Cx, and one end of the switch K2; the inductor L and the energy storage capacitor Co together form an LC filter circuit, which is used to suppress current and voltage fluctuations during the pre-charging process; the other end of the switch K2 is connected to the negative terminal of the battery module. The cathode of the Schottky diode D is connected to the other end of the DC bus capacitor Cx and one end of switch K1; the other end of switch K1 is connected to the positive terminal of the battery module. The control terminal of the semiconductor switching component Q1 is electrically connected to the microcontroller unit MCU. The microcontroller unit MCU outputs a pulse width modulation (PWM) signal to control the semiconductor switching component Q1 to perform switching operations at a preset switching frequency and duty cycle.

[0009] Furthermore, the semiconductor switching assembly Q1 includes a fully controllable semiconductor device and a unidirectional uncontrollable semiconductor device arranged in parallel, wherein the fully controllable semiconductor device is a MOSFET, IGBT or silicon carbide MOS, and the unidirectional uncontrollable semiconductor device is a freewheeling diode.

[0010] Furthermore, it also includes a voltage sampling circuit, whose input is connected to both ends of the DC bus capacitor Cx, and whose output is connected to the MCU's analog-to-digital converter (ADC) interface.

[0011] Furthermore, it also includes a current sampling circuit for acquiring the current in the charging circuit, the output of which is connected to the MCU's analog-to-digital converter (ADC) interface.

[0012] Furthermore, the switch K1 and switch K2 are relays or contactors.

[0013] This invention provides an electronic pre-charging method for an energy storage system based on a negative electrode Buck topology, applied to the aforementioned electronic pre-charging device for an energy storage system based on a negative electrode Buck topology, comprising the following steps: Power-on detection: Close switch one K1, open switch two K2, and connect the negative terminal of DC bus capacitor Cx to the negative terminal of the battery module through inductor L and semiconductor switch assembly Q1; Constant current precharge: The control unit MCU outputs a PWM signal of a set frequency, according to the duty cycle formula. Controls the semiconductor switching assembly Q1, where D is the duty cycle and I... o L represents the loop current, f represents the inductance value, and f represents the pulse frequency. bat This indicates the battery voltage; under the switching action of the semiconductor switching component Q1, the DC bus capacitor Cx is charged through the inductor L; the control unit MCU acquires the real-time current signal and uses a PI closed-loop algorithm to dynamically adjust the PWM duty cycle to maintain constant current charging; Voltage monitoring and switching: The microcontroller unit (MCU) monitors the voltage across the DC bus capacitor Cx in real time. When the voltage reaches a preset voltage threshold, the MCU stops outputting the PWM signal, the semiconductor switch component Q1 is turned off, the pre-charging process ends, switch K2 is closed, and the main circuit of the energy storage system is put into operation.

[0014] Furthermore, the method also includes: Active discharge: When the system stops, the microcontroller unit (MCU) controls the semiconductor switching component Q1 to enter the synchronous rectification mode, and the DC bus capacitor Cx discharges through the inductor L and the active discharge resistor.

[0015] Furthermore, the set frequency is 400 kHz; the preset voltage threshold is 0.96*V. bat .

[0016] The present invention provides an energy storage system including the above-mentioned electronic pre-charging device based on negative Buck topology. The device shares a ground with the energy storage system and is used for pre-charging before the main circuit is turned on and active discharging during shutdown, supporting ASIL-C functional safety.

[0017] According to specific embodiments provided by the present invention, the electronic pre-charging device and method for energy storage systems based on negative electrode Buck topology disclosed by the present invention have the following technical effects: In terms of cost and integration, the elimination of isolated power supplies and isolated drive components reduces the number of devices used and the area occupied by the circuit board, significantly reducing material costs. At the same time, it supports the monolithic integration of driving, sampling and related communication functions, simplifying the system structure. In terms of safety and reliability, a common-ground sampling design is adopted to accelerate the protection response speed for faults such as overcurrent and improve the timeliness of safety protection; the main negative relay is located in the negative circuit, which reduces the generation of electric arc and extends the service life of the relay. In addition, the LC filter circuit composed of alloy inductor and ceramic capacitor can suppress current and voltage fluctuations during pre-charging, reduce the electrical stress of components, and enhance system stability. In terms of efficiency and functionality, the pre-charging process has low energy loss and high efficiency. While ensuring high efficiency, it also takes into account a relatively fast pre-charging speed. In addition, an active discharge function has been added, which can realize the safe discharge of the DC bus capacitor when the system is shut down, meet the system's safe shutdown requirements, and adapt to the integrated and high-safety application requirements of modern energy storage systems. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the electronic pre-charging device structure of an energy storage system based on the negative electrode Buck topology according to an embodiment of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The purpose of this invention is to provide an electronic pre-charging device and method for an energy storage system based on a negative-electrode Buck topology, achieving: Eliminating the need for isolated power supplies and isolated drivers reduces BOM costs by more than 40%; Common ground current sampling simplifies the sampling link and improves protection speed; By moving the relay contacts to the negative terminal, the arc energy is reduced, and the lifespan is extended. The topology shares a common ground with the chip, making it easy to integrate on a single chip and supporting ASIL-C functional safety.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1 like Figure 1 As shown, the electronic pre-charging device for an energy storage system based on a negative Buck topology provided by the present invention includes: a negative Buck constant current pre-charging circuit, a main positive relay K1 (normally closed during the pre-charging stage), a main negative relay K2 (open during the pre-charging stage and closed after completion), a DC bus capacitor Cx (to be pre-charged), and a microcontroller unit MCU. The negative electrode Buck constant current pre-charge circuit includes a semiconductor switching component Q1, a Schottky diode D, an inductor L, and an energy storage capacitor Co (a ceramic capacitor may be selected, with optional high-frequency ripple absorption). Component selection: K1 and K2 are relays, with K2 located in the negative circuit, resulting in low arc energy (50K reduction in contact temperature rise); Q1 is a SiC MOSFET, supporting high-frequency switching (400kHz) and reducing switching losses; L is a 20μH alloy inductor; K1 and K2 are 800V / 50A relays; and the MCU is an STM32H743 (equipped with a 16-bit ADC and high-frequency PWM output). The drain of Q1 is connected to the negative terminal of the battery module, and the source is connected to one end of the inductor L and the anode of the Schottky diode D. The other end of the inductor L is connected to one end of the energy storage capacitor Co, one end of the DC bus capacitor Cx, and the rear end of the main negative relay K2; the inductor L and the energy storage capacitor Co together form an LC filter circuit, which is used to suppress current and voltage fluctuations during the pre-charging process; the front end of the main negative relay K2 is connected to the negative terminal of the battery module. The cathode of the Schottky diode D is connected to the rear end of the main positive relay K1 for freewheeling and suppressing reverse voltage; the front end of the main positive relay K1 is connected to the positive terminal of the battery module; the cathode of the Schottky diode D is also connected to the other end of the DC bus capacitor Cx. The control terminal of Q1 is electrically connected to the microcontroller unit (MCU). The MCU outputs a pulse width modulation (PWM) signal to control Q1 to perform switching operations at a preset switching frequency and duty cycle; and charges the DC bus capacitor Cx through the inductor L.

[0024] In addition, a current sampling circuit can be set up, for example, by using a low-side shunt resistor R. SIt is connected in series between the source of Q1 and the negative terminal of the battery module to collect the inductor current; a voltage sampling circuit can also be set up, using a voltage divider network connected to both ends of the DC bus capacitor Cx, and the output terminals are all connected to the MCU's 16-bit ADC interface.

[0025] Example 2 This invention provides an electronic pre-charging method for an energy storage system based on a negative electrode Buck topology, applied to the aforementioned electronic pre-charging device for an energy storage system based on a negative electrode Buck topology, comprising the following steps: Power-on self-test: Close the main positive relay K1, open the main negative relay K2, and connect the negative terminal of the DC bus capacitor Cx to the negative terminal of the battery module through Q1 and L to complete the circuit initialization; Constant current precharge: The MCU outputs a 400kHz PWM signal, according to the duty cycle formula. (I) o =2A constant current value, f=400kHz, V bat (Based on battery voltage) controls the Q1 switch; through the low-side shunt resistor R S The current signal is acquired and transmitted to the MCU via a 16-bit ADC. The MCU uses a PI closed-loop algorithm to dynamically adjust the PWM duty cycle to maintain a constant current of 2A. Under the switching action of the semiconductor switching component Q1, the DC bus capacitor Cx is charged through the inductor L. Voltage monitoring and switching: The MCU monitors the voltage across the DC bus capacitor Cx in real time. When Vcx ≥ 0.96V... bat When the PWM signal is stopped, Q1 is turned off; the main negative relay K2 is closed, the pre-charge drive is disconnected, and the main circuit of the energy storage system is put into operation. Active discharge (optional): When the system needs to be discharged after shutdown, the MCU controls Q1 to enter synchronous rectification mode. Cx forms a discharge path through L, the 50Ω active discharge resistor, and Q1, discharging the voltage of Cx to <60V within ≤2s. The active discharge resistor is connected in series with the inductor L.

[0026] Furthermore, the method can also be used for fault handling: When overcurrent (≥125% I) is detected o Overvoltage (≥102% V) bat When the drive voltage is low (≤90% of the rated drive voltage), the MCU triggers the hardware shutdown mechanism, shuts down Q1 within 10μs, and reports to the BMS (Battery Management System).

[0027] Example 3 The present invention provides an energy storage system, including the above-mentioned electronic pre-charging device based on negative Buck topology. The device shares a ground with the energy storage system (including battery clusters, BMS and inverter, etc.) and is used for pre-charging before the main circuit is turned on and active discharging during shutdown, supporting ASIL-C functional safety.

[0028] In summary, this invention employs a negative-terminal Buck precharge topology with the battery negative terminal as the reference ground. The switching transistor, driver, sampling circuit, and MCU share a common ground, eliminating the need for isolated power supplies. The low-side shunt resistor directly detects the inductor current, enabling hardware overcurrent protection of <10 µs. The same inductor and switching device also provide active discharge functionality after precharge, with the discharge and charging paths reused. The relay contacts are located on the negative terminal, resulting in low arc energy and a lifespan >100,000 cycles. The chip-level integration of driver, sampling, and PMBus supports ASIL-C functional safety.

[0029] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An energy storage system electronic pre-charge device based on a negative Buck topology, characterized in that, Comprise: A negative Buck constant current pre-charging circuit, switch one K1, switch two K2, DC bus capacitor Cx and micro control unit MCU; The negative Buck constant current pre-charging circuit comprises semiconductor switch component Q1, Schottky diode D, inductor L and energy storage capacitor Co; The input end of the semiconductor switch component Q1 is connected to the negative electrode of the battery module, and the output end is respectively connected to one end of the inductor L and the anode of the Schottky diode D; The other end of the inductor L is respectively connected to one end of the energy storage capacitor Co, one end of the DC bus capacitor Cx and one end of the switch two K2; the inductor L and the energy storage capacitor Co together constitute an LC filter circuit for suppressing current and voltage fluctuations during pre-charging; the other end of the switch two K2 is connected to the negative electrode of the battery module; The cathode of the Schottky diode D is respectively connected to the other end of the DC bus capacitor Cx and one end of the switch one K1; the other end of the switch one K1 is connected to the positive electrode of the battery module; The control end of the semiconductor switch component Q1 is electrically connected to the micro control unit MCU, and the micro control unit MCU outputs a pulse width modulation (PWM) signal to control the semiconductor switch component Q1 to perform switching operation at a preset switching frequency and duty cycle.

2. The energy storage system electronic pre-charging device based on negative Buck topology according to claim 1, characterized in that, The semiconductor switch component Q1 comprises a fully controlled semiconductor device and a unidirectional non-controllable semiconductor device arranged in parallel, wherein the fully controlled semiconductor device adopts MOSFET, IGBT or silicon carbide MOS, and the unidirectional non-controllable semiconductor device adopts a freewheeling diode.

3. The energy storage system electronic pre-charging device based on negative Buck topology according to claim 1, characterized in that, Further comprising: A voltage sampling circuit, the input end of which is connected to both ends of the DC bus capacitor Cx, and the output end is connected to the analog-to-digital conversion (ADC) interface of the MCU.

4. The negative Buck topology based energy storage system electronic pre-charge device of claim 1, wherein, Further comprising: A current sampling circuit for collecting current in the charging circuit, the output end of which is connected to the analog-to-digital conversion (ADC) interface of the MCU.

5. The negative Buck topology based energy storage system electronic pre-charge device of claim 1, wherein, The switch one K1 and the switch two K2 are relays or contactors.

6. An electronic pre-charging method of the energy storage system based on negative Buck topology, applied to the electronic pre-charging device of the energy storage system based on negative Buck topology in any one of claims 1-5, characterized in that, The method comprises the following steps: Power-on detection: close the switch one K1 and open the switch two K2, the negative end of the DC bus capacitor Cx is connected to the negative electrode of the battery module through the inductor L and the semiconductor switch component Q1; Constant current pre-charge: the control unit MCU outputs a PWM signal with a set frequency, according to the duty cycle formula The semiconductor switch assembly Q1 is switched, wherein D is the duty cycle, I o I represents the circuit current, L represents the inductance value, f represents the pulse frequency, V bat represents the battery voltage; under the switching action of the semiconductor switch assembly Q1, the DC bus capacitor Cx is charged through the inductor L; the control unit MCU acquires the real-time collected current signal, dynamically adjusts the PWM duty cycle using the PI closed-loop algorithm, and maintains constant current charging; Voltage monitoring and switching: the micro control unit MCU monitors the voltage across the DC bus capacitor Cx in real time, and when the voltage reaches a preset voltage threshold, the micro control unit MCU stops outputting the PWM signal, the semiconductor switch component Q1 is turned off, the pre-charging process is completed, the switch two K2 is closed, and the main circuit of the energy storage system is put into operation.

7. The energy storage system electronic pre-charging method based on negative Buck topology according to claim 6, characterized in that, The method further comprises: Active discharge: when the system is shut down, the micro control unit MCU controls the semiconductor switch component Q1 to enter the synchronous rectification mode, and the DC bus capacitor Cx is discharged through the inductor L and the active discharge resistor.

8. The energy storage system electronic pre-charging method based on negative Buck topology according to claim 6, characterized in that, The set frequency is 400 kHz; the preset voltage threshold is 0.96*V bat .

9. An energy storage system characterized by, The electronic pre-charging device based on the negative Buck topology of any one of claims 1-5, the device is common with the energy storage system, used for pre-charging before the main circuit is turned on and active discharge when the system is shut down, supporting ASIL-C functional safety.

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