Discharge circuit for bus capacitor and energy storage system

Abstract

The application provides a bus capacitor discharge circuit and an energy storage system. The discharge circuit comprises a discharge module, a switch module and a driving control module; the driving control module comprises an auxiliary relay and a power taking circuit; the discharge module and the switch module are connected in series and then connected between the positive and negative electrodes of the bus capacitor; the first end of the auxiliary relay is connected with the control end of the switch module, and the second end of the auxiliary relay is connected with the voltage dividing end of the power taking circuit; the first end of the power taking circuit is connected with the positive electrode of the bus capacitor, and the second end of the power taking circuit is connected with the negative electrode of the bus capacitor. The power taking circuit directly obtains electric energy from the residual charge of the bus capacitor itself, and breaks away from the dependence on the external auxiliary power supply in the existing discharge scheme, thereby solving the pain points that the discharge circuit cannot be turned on and the discharge is interrupted when the auxiliary power supply is powered off or fails, ensuring that the discharge circuit is continuously turned on in the entire discharge period, and improving the operation safety of the energy storage system.

Description

Technical Field

[0001] This invention relates to the field of energy storage system technology, and in particular to a discharge circuit for a bus capacitor and an energy storage system. Background Technology

[0002] During the operation of an energy storage system, a large amount of charge will remain on the bus capacitor after the system stops working and the main relay of the DC main circuit is disconnected. If it cannot be discharged in time and quickly, the residual voltage will remain at a high level for a long time. This will not only pose a serious safety hazard to subsequent equipment inspection and maintenance, and may easily lead to electric shock injury or death to maintenance personnel, but may also damage the bus capacitor, electronic switches and other devices, affecting the service life of the energy storage system and the safety of secondary startup. Therefore, the rapid and safe discharge of the bus capacitor is one of the core issues that must be solved in the design of an energy storage system.

[0003] In existing technologies, the discharge of charge from the bus capacitor is typically achieved by connecting a discharge resistor in series with a relay across the two ends of the bus capacitor. The relay relies on an external auxiliary power supply. After a system power failure, the controller activates the relay to initiate the discharge. However, if the auxiliary power supply fails or is lost, the relay cannot be kept conducting, the discharge circuit is immediately broken, and the residual charge on the bus capacitor cannot continue to be discharged. This still poses safety hazards such as high-voltage electric shock, device damage, and increased risk of secondary system restart, making it difficult to meet the design requirements of safe, reliable, and active discharge for energy storage systems. Summary of the Invention

[0004] This invention provides a discharge circuit and energy storage system for a bus capacitor to solve the problem in the prior art where the poor reliability of the auxiliary power supply of the discharge circuit leads to residual high voltage in the bus capacitor, posing a safety hazard.

[0005] In a first aspect, embodiments of the present invention provide a discharge circuit for a bus capacitor, wherein the bus capacitor is connected between the positive and negative terminals of a DC main circuit, and the discharge circuit includes: The system includes a discharge module, a switch module, and a drive control module; the drive control module includes an auxiliary relay and a power supply circuit. The discharge module and the switch module are connected in series and then connected between the positive and negative terminals of the bus capacitor; The first terminal of the auxiliary relay is connected to the control terminal of the switch module, and the second terminal of the auxiliary relay is connected to the voltage divider terminal of the power supply circuit; the first terminal of the power supply circuit is connected to the positive terminal of the bus capacitor, and the second terminal of the power supply circuit is connected to the negative terminal of the bus capacitor.

[0006] In one possible implementation, the power-drawing circuit includes a resistor unit and a Zener diode; The first end of the resistor unit is the first end of the power-taking circuit, the second end of the resistor unit is the voltage divider end of the power-taking circuit, and the second end of the resistor unit is connected to the negative terminal of the Zener diode, with the positive terminal of the Zener diode being the second end of the power-taking circuit.

[0007] In one possible implementation, the power supply circuit further includes an electrolytic capacitor; The electrolytic capacitor is connected in parallel across the Zener diode.

[0008] In one possible implementation, the auxiliary relay is a normally closed relay.

[0009] In one possible implementation, the discharge circuit further includes a controller; The controller is configured to output a high-level signal to the normally closed relay when it detects that the DC main circuit is closed, and to output a low-level signal to the normally closed relay when it detects that the DC main circuit is open or the system is powered off.

[0010] In one possible implementation, the switching module includes a switching transistor and a first resistor; The source of the switching transistor is connected to the negative terminal of the bus capacitor, and the drain of the switching transistor is connected to one end of the discharge module; the gate of the switching transistor is connected to the first end of the first resistor, and the second end of the first resistor is the control terminal of the switching module.

[0011] In one possible implementation, the switching module further includes a buffer unit; The buffer unit is connected between the gate and source of the switching transistor.

[0012] In one possible implementation, the discharge module includes multiple resistor strings connected in parallel; the resistor strings include multiple surface-mount resistors connected in series.

[0013] In one possible implementation, multiple surface-mount resistors in the discharge module are mounted on at least one sub-circuit board, and each sub-circuit board has a plug-in portion on one side. A corresponding groove adapted to the plug-in portion is provided on the main circuit board. The multiple sub-circuit boards are vertically mounted on the main circuit board through the plug-in portion and the groove. The main circuit board is a circuit board that integrates the discharge circuit of the bus capacitor.

[0014] Secondly, embodiments of this application provide an energy storage system, which includes: an energy storage module, an inverter module, and a bus capacitor; the power supply terminal of the energy storage module is connected to the DC terminal of the inverter module via a DC bus; and the bus capacitor is connected between the positive and negative terminals of the DC bus. The energy storage system further includes a discharge circuit for the bus capacitor as described in the first aspect above.

[0015] This application provides a discharge circuit for a bus capacitor. This architecture achieves complete self-sufficiency in the discharge drive power supply. The power extraction circuit directly obtains power from the residual charge of the bus capacitor itself, eliminating the dependence of existing discharge schemes on external auxiliary power supplies. This solves the problem of discharge circuit failure and discharge interruption when the auxiliary power supply fails or is lost. Simultaneously, this architecture forms a complete control link: bus capacitor self-power extraction – auxiliary relay on / off control – switch module drive – closed-loop conduction of the discharge circuit. As long as there is residual voltage in the bus capacitor, the power extraction circuit can continuously provide stable drive to the switch module, ensuring that the discharge circuit remains conductive throughout the entire discharge cycle until the residual charge is completely discharged. It eliminates the need for complex active control chips and external power supply circuits, resulting in a simple hardware structure and strong anti-interference capabilities. This not only eliminates the high-voltage electric shock safety hazard during equipment maintenance but also avoids long-term performance damage to the bus capacitor and power devices caused by residual high voltage, improving the operational safety of the energy storage system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art 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.

[0017] Figure 1 This is a schematic diagram of the discharge circuit of the bus capacitor provided in an embodiment of the present invention; Figure 2 This is a specific circuit diagram of the discharge circuit of the bus capacitor provided in an embodiment of the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0019] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0020] The implementation of the present invention will be described in detail below with reference to the accompanying drawings: Figure 1 This is a schematic diagram of a discharge circuit for a bus capacitor provided in an embodiment of the present invention. (Refer to...) Figure 1 The discharge circuit includes: The system comprises a discharge module 10, a switch module 20, and a drive control module; the drive control module includes an auxiliary relay K1 and a power supply circuit 30; the discharge module 10 and the switch module 20 are connected in series between the positive and negative terminals of the bus capacitor; the first terminal of the auxiliary relay K1 is connected to the control terminal of the switch module 20, and the second terminal of the auxiliary relay K1 is connected to the voltage divider terminal of the power supply circuit 30; the first terminal of the power supply circuit 30 is connected to the positive terminal of the bus capacitor, and the second terminal of the power supply circuit 30 is connected to the negative terminal of the bus capacitor.

[0021] In this embodiment, the bus capacitor is connected between the positive and negative terminals of the DC bus in the DC main circuit. It is a capacitive device used to smooth the DC bus voltage, suppress voltage ripple, and store instantaneous energy. The DC main circuit may include an energy storage module, a main circuit relay K0, and a converter module. The energy storage module is connected to the DC terminal of the converter module through the DC bus, and the main circuit relay K0 is connected in series on the DC bus.

[0022] It should be noted that the DC main circuit of the energy storage system, which includes an energy storage module and a converter module, is used as an example in the above embodiments. This is only a preferred embodiment of the present invention and is not a limitation on the DC main circuit described in the present invention. In practical applications, the DC main circuit described in the present invention can be applied to any DC power transmission circuit that has a bus capacitor and needs to safely discharge the residual charge of the bus capacitor after the main circuit is disconnected. This includes, but is not limited to, the DC main circuit of a photovoltaic grid-connected system, the high-voltage DC bus main circuit of a new energy vehicle electric drive system, the DC bus main circuit of an industrial frequency converter, the DC main circuit of an uninterruptible power supply (UPS), the DC intermediate circuit of a rail transit traction converter, and the high-voltage DC power supply main circuit of a data center.

[0023] The discharge module 10 and the switch module 20 are connected in series between the positive and negative terminals of the bus capacitor. The discharge module 10 dissipates the residual charge of the bus capacitor through the Joule heating effect. The switch module 20 is used to control the on / off state of the discharge circuit, and its on / off state directly determines whether the discharge circuit works. The discharge module 10 can be a power resistor with rated power and resistance matching the discharge requirements; the switch module 20 adopts a single-transistor on / off architecture composed of field-effect transistors.

[0024] The drive control module is a functional unit used to drive the switch module 20 and control the start and stop of the discharge circuit. In this embodiment, it is composed of an auxiliary relay K1 and a power supply circuit 30. The auxiliary relay K1 is an electromagnetic switch device with controllable contact switching capability, connected in series between the power supply circuit 30 and the control terminal of the switch module 20. Through the opening and closing of its contacts, it controls whether drive energy is supplied to the switch module 20, acting as the control switch for the discharge circuit. For example, the auxiliary relay K1 is a single-pole single-throw electromagnetic relay, and the power supply circuit 30 adopts a single-stage passive resistor voltage divider architecture.

[0025] The power extraction circuit 30 is connected in parallel across the bus capacitor, extracting electrical energy from the residual charge in the bus capacitor to provide drive power for the auxiliary relay K1 and the switch module 20. The voltage divider terminal of the power extraction circuit 30 is the port that outputs the drive power to the downstream switch module 20 after voltage transformation, and is the drive power output terminal of the power extraction circuit 30.

[0026] Specifically, the discharge module 10 and the switch module 20 are connected in series between the positive and negative terminals of the bus capacitor, forming a discharge path from the positive terminal of the bus capacitor through the discharge module 10 and the switch module 20 back to the negative terminal of the bus capacitor. The power supply circuit 30 draws power from both ends of the bus capacitor and generates a stable voltage signal at its voltage divider. This voltage is applied to the control terminal of the switch module 20 through the auxiliary relay K1, thereby controlling the switching module 20 to turn on or off, and thus controlling whether the discharge module 10 is connected to both ends of the bus capacitor to achieve discharge.

[0027] As a concrete example, the power supply circuit 30 can use a linear voltage regulator, drawing power from the bus capacitor and outputting a stable voltage. The voltage divider terminal is the output terminal of the voltage regulator. The auxiliary relay K1 uses an optocoupler relay or a solid-state relay, with its input controlled by an external signal and its output connected to the voltage divider terminal and the control terminal of the switching module 20. The switching module 20 uses an IGBT (Insulated Gate Bipolar Transistor), with its gate connected to the output terminal of the optocoupler relay through a current-limiting resistor. When the external signal is high, the optocoupler conducts, the regulated voltage drives the IGBT to conduct, and the discharge module 10 discharges; when the external signal is low, the optocoupler is off, the IGBT is off, and thus the power supply circuit 30 always draws power from the bus capacitor, requiring no auxiliary power supply.

[0028] Specifically, in the relevant technical solutions, the bleeder resistor is directly connected in parallel across the bus capacitor. If a low-resistance, high-power bleeder resistor is used, the resistor will continuously generate a large amount of useless power consumption and severe heat generation during normal system operation, significantly reducing system operating efficiency. Therefore, only a high-resistance, low-power bleeder resistor can be selected, resulting in extremely slow bleed speed. If a relay is connected in series with the bleeder resistor to achieve active bleed, the relay is directly connected to the main bleed circuit. All the current of the main bleed must flow through the mechanical contacts of the relay. However, the current carrying capacity and arc extinguishing capacity of the mechanical contacts have insurmountable physical limits and cannot withstand the large current of tens or even hundreds of amperes brought by high-power bleed. Forcing its use will cause the contacts to arc, stick together, and burn out, still failing to meet the high current requirements of high-power bleed.

[0029] The discharge circuit provided in this embodiment keeps the switch module 20 in the off state when the system is running normally and the DC main circuit is closed. The discharge module 10 and the bus capacitor are completely open. No matter how high the power level or how low the resistance of the discharge module 10 is, no power consumption or heat generation will be generated. This can completely eliminate the core contradiction between high power discharge and normal system efficiency, and fundamentally allow the use of low resistance and high power discharge module 10, providing a hardware foundation for fast discharge of large current.

[0030] Furthermore, in this embodiment, the first terminal of the auxiliary relay K1 is connected to the control terminal of the switch module 20, and the second terminal of the auxiliary relay K1 is connected to the voltage divider terminal of the power supply circuit 30. This architecture places the auxiliary relay K1 entirely within the low-voltage, low-current drive control circuit, detaching it from the high-voltage, high-current main discharge power circuit. The auxiliary relay K1 is only responsible for transmitting the milliampere-level drive current of the switch module 20, and does not need to carry the large current of the main discharge circuit, thus completely eliminating the limitation of the relay's current carrying capacity on the discharge power. In the main discharge circuit, only the discharge module 10 and the switch module 20 are connected in series. The switch module 20 can use a fully controlled power semiconductor device, whose rated current carrying capacity can perfectly match the high current requirements of the low-resistance, high-power discharge module 10, enabling high-power discharge at the kilowatt or even tens of kilowatt levels, significantly shortening the discharge time, and achieving rapid discharge of the bus capacitor energy.

[0031] As can be seen from the above embodiments, this architecture achieves complete self-sufficiency in the discharge drive power supply. The power extraction circuit 30 directly obtains power from the residual charge of the bus capacitor itself, completely eliminating the dependence of existing discharge schemes on external auxiliary power supplies. This solves the pain point of the discharge circuit being unable to conduct and the discharge being interrupted when the auxiliary power supply fails or is lost. At the same time, this architecture forms a complete control link of bus capacitor self-power extraction - auxiliary relay K1 on / off control - switch module 20 drive - discharge circuit closed-loop conduction. As long as there is residual voltage in the bus capacitor, the power extraction circuit 30 can continuously provide stable drive to the switch module 20, ensuring that the discharge circuit continues to conduct throughout the entire discharge cycle until the residual charge is completely discharged. There is no need for complex active control chips and external power supply circuits. The hardware structure is simple and has strong anti-interference capabilities. It not only eliminates the high-voltage electric shock safety hazard during equipment maintenance, but also avoids long-term performance damage to the bus capacitor and power devices caused by residual high voltage, greatly improving the operational safety of the energy storage system.

[0032] In one possible implementation, the power supply circuit 30 includes a buck converter; the positive input terminal of the buck converter is the first terminal of the power supply circuit 30, and the negative input terminal of the buck converter is the second terminal of the power supply circuit 30; the output terminal of the buck converter serves as the voltage divider terminal of the power supply circuit 30, and is used to output a stable DC voltage lower than the bus capacitor voltage.

[0033] Specifically, the buck converter can be a Buck-type DC-DC converter, consisting of a switching transistor, diode, inductor, capacitor and control chip, which can convert a higher DC bus voltage into a lower stable voltage output to the switching module 20.

[0034] In this embodiment, the control chip of the buck converter is designed with a high-voltage start-up regulator or an internal bias circuit, which draws power from the two ends of the bus capacitor. As long as there is voltage across the bus capacitor, the control chip will power itself through an internal ultra-low current regulator, putting the control chip into a sleep-wake monitoring state. When the DC main circuit is detected to be closed, the control chip does not perform high-frequency switching action and remains in sleep mode. When the DC main circuit is detected to be open, the control chip wakes up from sleep mode and enters normal switching operation mode, outputting a stable low voltage.

[0035] As can be seen from the above embodiments, since the no-load static current of the buck converter can be as low as microamps, using the buck converter as the power supply circuit 30 can significantly reduce the continuous power consumption during the power supply process, reduce the standby loss of the bus capacitor, and improve the system energy efficiency. On the other hand, the buck converter can stably output a low-voltage drive signal within a wide input voltage range, has strong load-carrying capacity and anti-input fluctuation capability, avoids abnormal heating of the switching transistor due to the drop in drive voltage, and improves the overall reliability of the discharge circuit.

[0036] In one possible implementation, Figure 2 The specific circuit diagram of the bus capacitor discharge circuit is shown. (Refer to...) Figure 2 The power supply circuit 30 includes a resistor unit and a Zener diode D1; The first end of the resistor unit is the first end of the power supply circuit 30, the second end of the resistor unit is the voltage divider end of the power supply circuit 30, and the second end of the resistor unit is connected to the negative terminal of the Zener diode D1, the positive terminal of the Zener diode D1 is the second end of the power supply circuit 30.

[0037] In this embodiment, the power supply circuit 30 adopts a structure in which a high-resistance voltage divider resistor string is connected in series with a Zener diode D1. The upper end of the resistor string is connected to the positive terminal of the bus capacitor, and the lower end is connected to the negative terminal of the Zener diode D1. The positive terminal of the Zener diode D1 is connected to the negative terminal of the bus capacitor. The voltage of the voltage divider is taken from the negative node of the Zener diode D1, and its voltage is clamped at the reverse breakdown voltage of the Zener diode D1.

[0038] In one possible implementation, the resistor unit comprises a plurality of voltage divider resistors connected in series.

[0039] Specifically, the resistor unit consists of multiple resistors, providing the required resistance value and power handling capability to limit current and work in conjunction with the Zener diode D1 to divide the voltage. Since the discharge circuit provided in this application is used in high-voltage scenarios, and conventional surface-mount resistors typically have a rated withstand voltage of 100V~200V, if the operating voltage of a single resistor exceeds its rated value, voltage breakdown, arcing, and burnout are highly likely, leading to complete failure of the power supply circuit. This application uses multiple surface-mount resistors with smaller resistance values ​​connected in series to form the power supply circuit 30, which can limit the voltage division of a single surface-mount resistor to less than its rated value. If a single large-value resistor is used, it must withstand the entire high voltage of the DC bus, resulting in higher costs and a high risk of breakdown failure.

[0040] When multiple resistors with small resistance values ​​are connected in series, the total withstand voltage is the sum of the withstand voltages of each resistor. By simply adjusting the number of resistors connected in series, it can be adapted to any high-voltage bus. Furthermore, the resistors are all general-purpose standard parts, which are low in cost and flexible in board layout, thus fundamentally ensuring the reliability of the power supply circuit 30 in high-voltage scenarios.

[0041] On the other hand, when multiple small-value resistors are connected in series, a single small resistor can easily achieve high precision and low temperature drift, and the total resistance value has high control precision, strong temperature stability and voltage stability. The current in the power supply circuit can be precisely locked at the low current design value, so that the power dissipation of the Zener diode is strictly controlled within the safe range, avoiding the risk of over-power failure.

[0042] In one possible implementation, the power supply circuit 30 further includes an electrolytic capacitor C3; The electrolytic capacitor C3 is connected in parallel across the Zener diode D1.

[0043] In this embodiment, electrolytic capacitor C3 is a polarized capacitor with a large capacitance, used for power supply filtering and energy storage. Electrolytic capacitor C3 is connected in parallel across the Zener diode, with its positive terminal connected to the negative terminal of Zener diode D1, and its negative terminal connected to the positive terminal of Zener diode D1. The capacitance of electrolytic capacitor C3 can be calculated based on the gate charge of the switching module 20, and can be a margin of 10 to 20 times the gate charge.

[0044] In this embodiment, the electrolytic capacitor C3 can be replaced with a multilayer ceramic capacitor or multiple small capacitors connected in parallel (C3 and C4) to improve high-frequency response and reliability.

[0045] In one embodiment, the power supply circuit 30 may further include a Zener diode; the Zener diode is connected in parallel across the electrolytic capacitor for overvoltage protection.

[0046] As can be seen from the above embodiments, the power supply circuit 30 is equipped with an electrolytic capacitor connected in parallel across the Zener diode D1. This structure fully utilizes the energy storage and smoothing filtering characteristics of the electrolytic capacitor. Firstly, it can smooth and filter the output voltage after the Zener diode D1 is clamped, effectively filtering out voltage ripple, instantaneous spikes, and high-frequency noise generated in the voltage divider circuit. It also eliminates the distortion of the drive signal caused by the complex electromagnetic environment of the system and bus voltage fluctuations, providing a more stable and pure drive voltage for the control terminals of the auxiliary relay K1 and the switching module 20. This avoids long-term impacts of fluctuating signals on the devices, reduces the probability of device performance degradation, and extends the service life of core components. At the same time, the energy storage function of the electrolytic capacitor can form short-term power supply redundancy. When the bus capacitor voltage drops momentarily or the voltage divider output of the resistor unit is momentarily insufficient, the electrolytic capacitor can quickly release the stored energy to continuously supplement the drive power supply for the subsequent circuits, preventing the switching module 20 from being erroneously turned off due to instantaneous voltage fluctuations and eliminating the risk of accidental interruption during the discharge process.

[0047] In one possible implementation, the auxiliary relay K1 is a normally closed relay.

[0048] In this embodiment, the auxiliary relay K1 is a normally closed relay, whose coil is driven by an external controller, and its contacts are connected in series between the voltage divider terminal and the control terminal of the switching module 20. The switching module 20 uses an N-channel MOSFET, with its gate as the control terminal, its source connected to the negative terminal of the bus, and its drain connected to a bleeder resistor. When the DC main circuit is detected to be connected, i.e., the main circuit relay K0 is closed, the controller controls the coil of the auxiliary relay K1 to be energized, the contacts open, the drive signal is cut off, the MOSFET is turned off, and it does not discharge; when the system is powered off or the main circuit relay K0 is opened, the controller is powered off, the contacts of the auxiliary relay K1 return to their normally closed state, the voltage at the voltage divider terminal is directly applied to the MOSFET gate, making it conduct, and the bleeder resistor is connected across the bus capacitor to complete the discharge.

[0049] As can be seen from the above embodiments, the auxiliary relay K1 provided in this embodiment is a normally closed relay. When the system is running normally and the DC main circuit is closed, the normally closed relay contacts can be driven to open through the control signal, cutting off the drive link of the switch module 20. This ensures that the discharge module 10 is not connected to the DC bus when the system is working normally, completely avoiding the useless power consumption generated by the discharge module 10, and improving the energy conversion efficiency and operating economy of the energy storage system. When the system stops and the DC main circuit is disconnected, the normally closed relay loses the drive control signal and can automatically reset to the contact closed state without additional power supply. It instantly connects the voltage divider terminal of the power supply circuit 30 and the control terminal of the switch module 20, quickly triggering the discharge circuit to conduct, realizing automatic and delay-free discharge after the system stops. Even if the controller completely loses power and fails, the discharge circuit can still be triggered and conducted through the inherent physical characteristics of the normally closed relay, greatly improving the fault redundancy capability and safety reliability of the circuit, and fundamentally avoiding the problem of discharge failure caused by the relay failing to engage after power failure.

[0050] In one possible implementation, the discharge circuit further includes a controller; The controller is configured to output a high-level signal to the normally closed relay when it detects that the DC main circuit is closed, and to output a low-level signal to the normally closed relay when it detects that the DC main circuit is open or the system is powered off.

[0051] In this embodiment, system power-on refers to the condition where the low-voltage auxiliary power supply circuit of the system containing the DC main circuit is powered normally, and low-voltage units such as the controller and detection circuit obtain working power and enter normal working state. System power-off refers to the condition where the low-voltage auxiliary power supply circuit of the system containing the DC main circuit loses power, and low-voltage units such as the controller and detection circuit lose working power and cannot work normally.

[0052] The controller in this embodiment uses a microcontroller unit (MCU). The MCU's digital signal acquisition port acquires the on / off state of the DC main circuit through the auxiliary contact of the main circuit relay K0, and acquires the system power-on / power-off state through the auxiliary power supply voltage acquisition port. The MCU's general purpose input / output port (GPIO) is used as a signal output terminal and is connected to the coil drive circuit of the normally closed relay.

[0053] When the MCU detects that the DC main circuit is closed through the auxiliary contact, the GPIO port continuously outputs a high-level signal, driving the normally closed relay coil to be energized, and the contact remains open; when the MCU detects that the DC main circuit is open, or detects that the system auxiliary power supply is de-energized (system power failure), the GPIO port switches to output a low-level signal, the normally closed relay coil is de-energized, and the contact is reset to the closed state.

[0054] As another specific example, the controller in this embodiment can also be a field-programmable gate array (FPGA). The differential signal acquisition port of the FPGA acquires the on / off state of the DC main circuit through a DC bus voltage sensor and acquires the power-on / power-off state of the system through an auxiliary power supply voltage sensor. The differential signal output terminal of the FPGA is connected to the coil drive circuit of the normally closed relay.

[0055] When the FPGA detects that the DC main circuit is closed through the voltage sensor, the differential output terminal continuously outputs a high-level signal, driving the normally closed relay coil to be energized and the contacts remain open. When the FPGA detects that the DC main circuit is open or detects that the system auxiliary power supply is de-energized (system power failure), the differential output terminal switches to output a low-level signal, the normally closed relay coil is de-energized, and the contacts are reset to the closed state.

[0056] In this embodiment, when the controller detects that the main circuit relay K0 of the DC main circuit is in an open state for multiple consecutive sampling cycles, or when the system is powered off, it outputs a low-level signal to the normally closed relay; when the controller detects that the main circuit relay K0 of the DC main circuit is in a closed state for multiple consecutive sampling cycles, it outputs a high-level signal to the normally closed relay.

[0057] As can be seen from the above embodiments, this embodiment limits the controller to output high and low level signals to control the normally closed relay according to the main circuit status. When the main circuit is closed, the controller outputs a high level, the normally closed relay coil is energized, the contacts open, and discharge is prohibited; when the main circuit is open or the system loses power, the controller outputs a low level, the normally closed relay contacts close, and discharge is initiated. This control logic ensures that discharge only occurs when needed, avoiding energy waste and heat generation caused by accidental discharge during normal operation, while automatically discharging after power failure, thus balancing energy saving and safety.

[0058] In one possible implementation, refer to Figure 2 The switching module 20 includes a switching transistor Q1 and a first resistor R1; The source of the switching transistor Q1 and the bus capacitor C BUS The negative terminal of the switch Q1 is connected to the negative terminal of the discharge module C. BUS One end of the switch is connected; the gate of the switch transistor Q1 is connected to the first end of the first resistor R1, and the second end of the first resistor R1 is the third end of the switch module 20.

[0059] Specifically, the switching transistor Q1 is an N-channel enhancement-mode power MOSFET or an N-type insulated-gate bipolar transistor.

[0060] The first resistor R1 is connected in series in the gate circuit of the switching transistor Q1 to limit the current flowing into the gate, protect the gate of the switching transistor Q1 from being broken down by overcurrent, and suppress parasitic oscillations in the gate circuit.

[0061] In this embodiment, a bidirectional transient voltage suppressor diode (TVS) can also be connected in parallel between the gate and source of the switching transistor Q1. When an abnormal voltage spike occurs at the gate, the TVS quickly clamps the voltage to prevent the gate from being damaged by overvoltage breakdown, thereby improving the anti-interference capability of the switching transistor Q1.

[0062] As can be seen from the above embodiments, in this embodiment, the first resistor R1 is connected in series in the gate drive path. The first resistor R1 can limit the gate drive current, prevent the drive signal from overshooting or oscillating, and avoid the switch Q1 from being mis-turned or damaged due to drastic fluctuations in the gate voltage; at the same time, the first resistor R1 can adjust the conduction speed of the switch Q1, slow down the drain current rise rate, reduce electromagnetic interference, and improve the switching safety and electromagnetic compatibility of the switching module 20.

[0063] In one possible implementation, the switching module 20 further includes a buffer unit; The buffer unit is connected between the gate and source of the switching transistor Q1.

[0064] In this embodiment, the buffer unit can be an RC buffer circuit or a TVS diode buffer circuit. Alternatively, the RC buffer circuit and the TVS diode buffer circuit can be connected in parallel between the gate and source of the switching transistor Q1.

[0065] As can be seen from the above embodiments, this embodiment includes a buffer unit between the gate and source of the switching transistor Q1. The buffer unit can absorb voltage spikes and oscillations in the gate drive circuit, preventing false turn-on due to static electricity or interference when the gate is floating; at the same time, during the turn-off period of the switching transistor Q1, the buffer unit provides a low-impedance discharge path, accelerates the discharge of gate charge, improves turn-off speed and reliability, thereby enhancing the anti-interference capability and operational stability of the switching module 20.

[0066] In one possible implementation, refer to Figure 2 The buffer unit includes a second resistor R2 and a first capacitor C1; The first end of the second resistor R2 and the first end of the first capacitor C1 are both connected to the gate of the switching transistor Q1; the second end of the second resistor R2 and the second end of the first capacitor C1 are both connected to the source of the switching transistor Q1.

[0067] In this embodiment, the RC parallel buffer circuit consists of a second resistor R2 and a first capacitor C1 connected in parallel between the gate and source of the switching transistor Q1. The first capacitor C1 is used to absorb high-frequency interference and smooth the drive voltage; the second resistor R2 is used to dissipate oscillation energy, suppress parasitic oscillations, and provide a discharge path for the gate charge.

[0068] In one possible implementation, the discharge module 10 includes multiple resistor strings connected in parallel; the resistor strings include multiple surface-mount resistors connected in series.

[0069] In this embodiment, the discharge module 10 includes multiple resistors; the resistors can be connected in series or in parallel.

[0070] Specifically, the discharge module 10 includes multiple resistor strings connected in parallel, and each resistor string includes multiple surface-mount resistors connected in series.

[0071] Specifically, the bus capacitor voltage is typically several hundred volts to over a thousand volts, while the rated withstand voltage of a single surface-mount resistor is extremely low, usually only tens of volts. If a single small resistor is directly connected across the high-voltage bus, it will be instantly broken down and burned out by the high voltage, making discharge impossible. This embodiment uses multiple small resistors connected in series to form a resistor string, so that the total withstand voltage of the individual resistor string is equal to the product of the withstand voltage of the single resistor and the number of resistors connected in series. This allows for precise matching of the high-voltage bus voltage, and the voltage distribution of each small resistor is uniform, preventing overvoltage failure of a single resistor and providing a safe basis for rapid discharge of the small resistor.

[0072] Furthermore, rapid discharge of DC bus voltage requires a large current, but the rated current-carrying capacity of a single surface-mount resistor is extremely weak. If only series resistors are used, the loop current will be limited by the current-carrying capacity of a single resistor, making rapid discharge of large current impossible. Moreover, a single resistor will overheat and burn out quickly due to excessive current and power overload. This embodiment uses multiple sets of series resistors connected in parallel. The total current-carrying capacity is equal to the product of the current-carrying capacity of a single set of series resistors and the number of parallel sets, which can easily handle the large current required for rapid discharge. At the same time, the total power loss is evenly distributed across each small resistor, avoiding localized overheating and ensuring a continuous and stable discharge process without interruption due to resistor burnout.

[0073] In one possible implementation, the multiple surface-mount resistors in the discharge module 10 are mounted on at least one sub-circuit board, and each sub-circuit board has a plug-in portion on one side. A corresponding groove adapted to the plug-in portion is provided on the main circuit board. The multiple sub-circuit boards are vertically mounted on the main circuit board through the plug-in portion and the groove. The main circuit board is a circuit board that integrates the discharge circuit of the bus capacitor.

[0074] Specifically, since the bleeder module 10 includes a large number of surface mount resistors, simply using a surface mount method would require reserving a large area on the main circuit board to mount the resistors. In this embodiment, multiple surface mount resistors can be evenly mounted on multiple sub-circuit boards and connected on the sub-circuit boards in the series-parallel manner described above. At the same time, a plug-in part is provided on one side of the sub-circuit board with the surface mount resistors evenly mounted, and a groove is provided on the main circuit board. Through the cooperation of the plug-in part and the groove, multiple sub-circuit boards with surface mount resistors are vertically plugged into the main circuit board, thereby making full use of the Z-axis space in the system and avoiding the problem of needing to expand the system space due to laying a large number of surface mount resistors on the main circuit board.

[0075] In this embodiment, the plug portion is a protruding metal pin, the groove is a metal slot adapted to the metal pin, the metal pin is electrically connected to the series-parallel resistor network in the discharge module 10, and the metal slot is electrically connected to the corresponding circuit line on the main circuit board, for example, the metal slot is electrically connected to the positive terminal of the bus capacitor on the main circuit board and the drain of the switch module 20.

[0076] This application provides an energy storage system, which includes: an energy storage module, an inverter module, and a bus capacitor; the power supply terminal of the energy storage module is connected to the DC terminal of the inverter module through a DC bus; and the bus capacitor is connected between the positive and negative terminals of the DC bus. The energy storage system also includes a discharge circuit for the bus capacitor as described above.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A discharge circuit for a bus capacitor, characterized in that, The bus capacitor is connected between the positive and negative terminals of the DC main circuit, and the discharge circuit includes: The system includes a discharge module, a switch module, and a drive control module; the drive control module includes an auxiliary relay and a power supply circuit. The discharge module and the switch module are connected in series and then connected between the positive and negative terminals of the bus capacitor; The first terminal of the auxiliary relay is connected to the control terminal of the switch module, and the second terminal of the auxiliary relay is connected to the voltage divider terminal of the power supply circuit; the first terminal of the power supply circuit is connected to the positive terminal of the bus capacitor, and the second terminal of the power supply circuit is connected to the negative terminal of the bus capacitor.

2. The discharge circuit for the bus capacitor according to claim 1, characterized in that, The power supply circuit includes a resistor unit and a Zener diode; The first end of the resistor unit is the first end of the power-taking circuit, the second end of the resistor unit is the voltage divider end of the power-taking circuit, and the second end of the resistor unit is connected to the negative terminal of the Zener diode, with the positive terminal of the Zener diode being the second end of the power-taking circuit.

3. The discharge circuit of the bus capacitor according to claim 2, characterized in that, The power supply circuit also includes an electrolytic capacitor; The electrolytic capacitor is connected in parallel across the Zener diode.

4. The discharge circuit for the bus capacitor according to claim 1, characterized in that, The auxiliary relay is a normally closed relay.

5. The discharge circuit for the bus capacitor according to claim 4, characterized in that, The discharge circuit also includes a controller; The controller is configured to output a high-level signal to the normally closed relay when it detects that the DC main circuit is closed, and to output a low-level signal to the normally closed relay when it detects that the DC main circuit is open or the system is powered off.

6. The discharge circuit for the bus capacitor according to claim 1, characterized in that, The switching module includes a switching transistor and a first resistor; The source of the switching transistor is connected to the negative terminal of the bus capacitor, and the drain of the switching transistor is connected to one end of the discharge module; the gate of the switching transistor is connected to the first end of the first resistor, and the second end of the first resistor is the control terminal of the switching module.

7. The discharge circuit for the bus capacitor according to claim 6, characterized in that, The switching module also includes a buffer unit; The buffer unit is connected between the gate and source of the switching transistor.

8. The discharge circuit for the bus capacitor according to claim 1, characterized in that, The discharge module includes multiple resistor strings connected in parallel; each resistor string includes multiple surface-mount resistors connected in series.

9. The discharge circuit for the bus capacitor according to claim 8, characterized in that, The multiple surface-mount resistors in the discharge module are mounted on at least one sub-circuit board, and each sub-circuit board has a plug-in portion on one side. The main circuit board has a corresponding groove adapted to the plug-in portion. The multiple sub-circuit boards are vertically mounted on the main circuit board through the plug-in portion and the groove. The main circuit board is a circuit board that integrates the discharge circuit of the bus capacitor.

10. An energy storage system, characterized in that, include: The system includes an energy storage module, an inverter module, and a bus capacitor. The power supply terminal of the energy storage module is connected to the DC terminal of the inverter module via a DC bus. The bus capacitor is connected between the positive and negative terminals of the DC bus. The energy storage system further includes: a discharge circuit for the bus capacitor as described in any one of claims 1 to 9.

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