Buck type electronic pre-charging device and method suitable for energy storage system

Abstract

The invention discloses a Buck type electronic pre-charging device and method suitable for an energy storage system. The Buck type electronic pre-charging device comprises a 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 Buck constant-current pre-charging circuit comprises a semiconductor switch assembly Q1, a semiconductor switch assembly Q2, an inductor L and an energy storage capacitor Co; the MCU outputs a pulse width modulation (PWM) signal and controls the Q1 to perform switching action at a preset switching frequency and duty ratio; under the switching action of the Q1, the DC bus capacitor Cx is charged through the inductor L, and the MCU realizes constant current control of the charging current by adjusting the duty ratio of the PWM signal in real time. According to the invention, by using the constant current characteristic of the Buck circuit, the pre-charging efficiency is improved, the energy loss is reduced, the charging speed is accelerated, and rapid and efficient pre-charging of the energy storage element is realized.

Description

Technical Field

[0001] This invention relates to the field of energy storage system technology, and in particular to a Buck-type electronic pre-charging device and method suitable for energy storage systems. 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, the pre-charging stage 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 a level close to the bus voltage through a controlled process before the main circuit is fully connected, thereby minimizing the inrush current at the moment of closing.

[0004] Currently, most energy storage systems employ a resistor-based current-limiting scheme for the pre-charging process. This scheme works by connecting a pre-charging resistor of appropriate resistance and a contactor (or relay) in parallel in the path between the DC bus and the energy storage element being pre-charged. During system startup, the circuit containing the pre-charging resistor is first connected, using this resistor to limit the charging current and achieve initial charging of the energy storage element. When the voltage across the energy storage element reaches a preset proportion of the bus voltage, the main contactor is closed, short-circuiting the pre-charging resistor, thus completing the pre-charging process and allowing the system to enter normal operation. Although the resistor-based current-limiting scheme is widely used due to its simple structure and low cost, its inherent technical drawbacks are also significant: High energy loss and low system efficiency: During the pre-charging process, a huge current flows through the current-limiting resistor, which generates considerable heat according to Joule's law. This part of the electrical energy is wasted and cannot be used to effectively charge the energy storage element, reducing the overall energy efficiency of the system. Especially in situations where frequent start-stop is required, the accumulated energy loss is more significant. Slow charging speed: In order to limit the current and avoid overheating of the resistor, it is usually necessary to select a resistor with a large resistance value. This results in a large RC time constant of the pre-charge circuit, which makes the capacitor voltage rise slowly and prolongs the start-up preparation time of the entire system. Thermal management requirements: The heat generated by the resistor needs to be effectively dissipated, which may increase the design complexity and cost of the system's heat dissipation structure.

[0005] Therefore, existing resistive pre-charging schemes are insufficient to meet the development needs of modern efficient, fast, and energy-saving energy storage systems, and there is an urgent need to propose a more advanced pre-charging method. Summary of the Invention

[0006] The purpose of this invention is to provide a Buck-type electronic pre-charging device and method suitable for energy storage systems. By utilizing the constant current characteristics of the Buck circuit, the pre-charging efficiency is improved, energy loss is reduced, and the charging speed is accelerated, thereby achieving rapid and efficient pre-charging of energy storage components.

[0007] To achieve the above objectives, the present invention provides the following solution: A Buck-type electronic pre-charge device suitable for energy storage systems includes: a Buck constant current pre-charge circuit, a switch K1, a switch K2, a DC bus capacitor Cx, and a microcontroller unit (MCU). The Buck constant current pre-charge circuit includes a semiconductor switching component Q1, a semiconductor switching component Q2, an inductor L, and an energy storage capacitor Co; The input terminal of the semiconductor switch assembly Q1 is connected to the positive terminal of the battery module, and the output terminal is connected to one end of the inductor L and the input terminal of the semiconductor switch assembly Q1, respectively. The other end of the inductor L is connected to one end of the energy storage capacitor Co and one end of the DC bus capacitor Cx, respectively; 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 output terminal of the semiconductor switch assembly Q1, the other end of the energy storage capacitor Co, and the other end of the DC bus capacitor Cx are all connected to one end of switch K2, and the other end of switch K2 is connected to the negative terminal of the battery module. One end of the switch K1 is connected to the positive terminal of the battery module, and the other end is connected to one end of the DC bus capacitor Cx; The control terminals of the semiconductor switching components Q1 and Q2 are electrically connected to the microcontroller unit (MCU). The 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.

[0008] Furthermore, the semiconductor switching components Q1 and Q2 each include a fully controllable semiconductor device and a unidirectional uncontrollable semiconductor device arranged in parallel. The fully controllable semiconductor device is a MOSFET, IGBT, or silicon carbide MOS, and the unidirectional uncontrollable semiconductor device is a freewheeling diode.

[0009] 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.

[0010] 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.

[0011] Furthermore, the switch K1 and switch K2 are relays or contactors.

[0012] The present invention also provides a Buck-type electronic pre-charging method suitable for energy storage systems, applied to the aforementioned Buck-type electronic pre-charging device suitable for energy storage systems, comprising the following steps: To initiate the pre-charging process, close switch K2 and open switch K1. 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. When the semiconductor switching component Q1 is switched, the DC bus capacitor Cx is charged through the inductor L. The microcontroller unit MCU achieves constant current control of the charging current by adjusting the duty cycle of the PWM signal in real time. 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, the switch K1 is closed, and the main circuit of the energy storage system is put into operation.

[0013] Furthermore, the constant current control is achieved by the MCU acquiring the current signal flowing through the inductor L or the current sampling unit connected in series in the charging circuit, comparing it with an internally set current reference value, and dynamically adjusting the duty cycle of the PWM signal through a closed-loop control algorithm.

[0014] Furthermore, the closed-loop control algorithm is a proportional-integral (PI) control or a proportional-integral-derivative (PID) control.

[0015] The present invention also provides an energy storage system, including the Buck-type electronic pre-charging device as described above, which is used to pre-charge the DC bus capacitor Cx before the main circuit is turned on.

[0016] According to specific embodiments provided by the present invention, the Buck-type electronic pre-charging device and method suitable for energy storage systems disclosed by the present invention have the following technical effects: I. Significantly improves energy efficiency and speed. This invention transforms energy dissipation into efficient energy transfer, fundamentally eliminating resistive heat loss. At the same time, it achieves rapid charging of the energy storage capacitor through constant current control of the Buck circuit, greatly shortening the system startup time. Second, it enhances control precision and system reliability by using MCU for closed-loop regulation to ensure stable and shock-free current during charging; the built-in LC filter circuit effectively suppresses voltage and current fluctuations, reduces electrical stress on components, and improves system lifespan and stability. Third, it achieves intelligence and integration. The device has a compact structure and can accurately manage the charging process through an MCU, providing a foundation for system status monitoring and intelligent protection.

[0017] In summary, this invention optimizes the pre-charging process from a high-loss, slow process into a highly efficient, fast, intelligent, and reliable active control process, thereby comprehensively improving the overall performance of the energy storage system. 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 Buck-type electronic pre-charge device applicable to energy storage systems 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 a Buck-type electronic pre-charging device and method suitable for energy storage systems. By utilizing the constant current characteristics of the Buck circuit, it enables rapid and efficient pre-charging of energy storage components, thereby solving the problems existing in the prior art.

[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 Buck-type electronic pre-charging device for energy storage systems provided by the present invention includes: a Buck constant current pre-charging circuit, a switch K1, a switch K2, a DC bus capacitor Cx, and a microcontroller unit (MCU). The Buck constant current pre-charge circuit includes a semiconductor switching component Q1, a semiconductor switching component Q2, an inductor L, and an energy storage capacitor Co; The input terminal of the semiconductor switch assembly Q1 is connected to the positive terminal of the battery module, and the output terminal is connected to one end of the inductor L and the input terminal of the semiconductor switch assembly Q1, respectively. The other end of the inductor L is connected to one end of the energy storage capacitor Co and one end of the DC bus capacitor Cx, respectively; 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 output terminal of the semiconductor switch assembly Q1, the other end of the energy storage capacitor Co, and the other end of the DC bus capacitor Cx are all connected to one end of switch K2, and the other end of switch K2 is connected to the negative terminal of the battery module. One end of the switch K1 is connected to the positive terminal of the battery module, and the other end is connected to one end of the DC bus capacitor Cx; The control terminals of the semiconductor switching components Q1 and Q2 are electrically connected to the microcontroller unit (MCU). The 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.

[0024] The semiconductor switching components Q1 and Q2 each include a fully controllable semiconductor device and a unidirectional uncontrollable semiconductor device connected in parallel. The fully controllable semiconductor device is a MOSFET, IGBT, or silicon carbide MOS, and the unidirectional uncontrollable semiconductor device is a freewheeling diode.

[0025] The Buck-type electronic pre-charge device also includes: The voltage sampling circuit has its input terminal connected to both ends of the DC bus capacitor Cx, and its output terminal connected to the MCU's analog-to-digital converter (ADC) interface. The current sampling circuit is used to collect the current in the charging circuit, and its output is connected to the analog-to-digital converter (ADC) interface of the MCU.

[0026] The voltage sampling circuit consists of a high-precision resistor divider network and an operational amplifier follower circuit, which proportionally scales the highest voltage across the DC bus capacitor Cx to the MCU's ADC range (0-3.3V). The current sampling circuit uses a closed-loop Hall current sensor connected in series in the loop containing inductor L, and its output is a current signal, which is also connected to the MCU's ADC interface.

[0027] The switches K1 and K2 are relays.

[0028] The microcontroller unit (MCU) can be a 32-bit ARM Cortex-M4 core microcontroller with high-resolution PWM output and ADC acquisition capabilities (e.g., STMicroelectronics' STM32F334).

[0029] Example 2 The present invention also provides a Buck-type electronic pre-charging method suitable for energy storage systems, applied to the aforementioned Buck-type electronic pre-charging device suitable for energy storage systems, comprising the following steps: To initiate the pre-charging process, close switch K2 and open switch K1. 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. When the semiconductor switching component Q1 switches, the DC bus capacitor Cx is charged through the inductor L. The microcontroller unit (MCU) controls the charging current by adjusting the duty cycle of the PWM signal in real time. The constant current control is achieved by the MCU acquiring the current signal flowing through the inductor L or the current sampling unit connected in series in the charging circuit, comparing it with an internally set current reference value, and dynamically adjusting the duty cycle of the PWM signal through a closed-loop control algorithm (proportional-integral PI control or proportional-integral-derivative PID control). 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, the switch K1 is closed, and the main circuit of the energy storage system is put into operation.

[0030] Example 3 The present invention also provides an energy storage system, including the Buck-type electronic pre-charging device as described above, which is used to pre-charge the DC bus capacitor Cx before the main circuit is turned on.

[0031] In summary, this invention uses a Buck circuit as a pre-charging circuit for pre-charging, which can significantly reduce energy loss and improve system efficiency; precise control of the charging process by the MCU can accelerate the charging speed and shorten the pre-charging time; during the pre-charging process, the inductor L and capacitor Co constitute an LC filter circuit, which effectively suppresses current fluctuations, improves charging stability, and reduces the damage of current fluctuations to circuit components.

[0032] 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. A Buck type electronic pre-charge device suitable for use in an energy storage system, characterized in that, The application relates to a battery module pre-charging circuit. The Buck constant-current pre-charging circuit comprises semiconductor switch components Q1, semiconductor switch components Q2, an inductor L and an energy storage capacitor Co. The input end of the semiconductor switch component Q1 is connected to the positive pole of a battery module, and the output end is connected to one end of the inductor L and the input end of the semiconductor switch component Q1. The other end of the inductor L is connected to one end of the energy storage capacitor Co and one end of the DC bus capacitor Cx. The other end of the semiconductor switch component Q1, the other end of the energy storage capacitor Co and the other end of the DC bus capacitor Cx are commonly connected to one end of the switch K2, and the other end of the switch K2 is connected to the negative pole of the battery module. One end of the switch K1 is connected to the positive pole of the battery module, and the other end is connected to one end of the DC bus capacitor Cx. The control ends of the semiconductor switch components Q1 and Q2 are electrically connected to the micro control unit MCU, the micro control unit MCU outputs a pulse width modulation (PWM) signal, and the semiconductor switch component Q1 is controlled to perform switching action at a preset switching frequency and duty ratio. The semiconductor switch components Q1 and Q2 each comprise a full-control semiconductor device and a unidirectional non-controllable semiconductor device arranged in parallel, wherein the full-control semiconductor device adopts a MOSFET, an IGBT or a silicon carbide MOS, and the unidirectional non-controllable semiconductor device adopts a freewheeling diode.

2. The Buck type electronic precharge device suitable for energy storage systems according to claim 1, characterized in that, The application further comprises:

3. The Buck type electronic precharge device suitable for energy storage systems according to claim 1, characterized in that, A voltage sampling circuit, the input end of which is connected to the two ends of the DC bus capacitor Cx, and the output end is connected to an analog-to-digital conversion (ADC) interface of the MCU. The application further comprises:

4. The Buck type electronic precharge device suitable for energy storage systems according to claim 1, characterized in that, A current sampling circuit for collecting the current in the charging circuit, the output end of which is connected to an analog-to-digital conversion (ADC) interface of the MCU. The switch K1 and the switch K2 are relays or contactors.

5. The Buck type electronic precharge device suitable for energy storage systems according to claim 1, characterized in that, The application comprises the following steps:

6. A Buck type electronic pre-charging method suitable for energy storage system, applied to the Buck type electronic pre-charging device suitable for energy storage system of any one of claims 1-5, characterized in that, Starting the pre-charging process, closing the switch K2 and opening the switch K1; The micro control unit MCU outputs a pulse width modulation (PWM) signal, and the semiconductor switch component Q1 is controlled to perform switching action at a preset switching frequency and duty ratio. Under the switching action of the semiconductor switch component Q1, the DC bus capacitor Cx is charged through the inductor L, wherein the micro control unit MCU realizes constant-current control of the charging current by adjusting the duty ratio of the PWM signal in real time. 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 K1 is closed, and the energy storage system main circuit is put into operation. The constant-current control is realized by collecting the current signal of the current sampling unit flowing through the inductor L or connected in series in the charging circuit through the MCU, comparing the current signal with an internally set current reference value, and dynamically adjusting the duty ratio of the PWM signal through a closed-loop control algorithm.

7. The Buck type electronic pre-charge method suitable for energy storage systems as claimed in claim 6, wherein, ​ 8. The Buck type electronic pre-charge method suitable for energy storage system according to claim 7, characterized in that, The closed-loop control algorithm is proportional integral (PI) control or proportional integral derivative (PID) control.

9. An energy storage system characterized by, The Buck type electronic pre-charging device for energy storage system as claimed in any one of claims 1-5 is used to pre-charge the DC bus capacitor Cx before the main circuit is turned on.

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